Instrument Flying Handbook Chapter 11

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Chapter 11

Emergency Operations

Introduction

Changing weather conditions, air traffic control (ATC), the aircraft, and the pilot are all variables that make instrument flying an unpredictable and challenging operation. The safety of the flight depends upon the pilot’s ability to manage these variables while maintaining positive aircraft control and adequate situational awareness. This chapter will discuss the recognition and suggested remedies for such abnormal and emergency events related to unforecasted, adverse weather, aircraft system malfunctions, communication/navigation system malfunctions, and loss of situational awareness.

Unforecast Adverse Weather

Inadvertent Thunderstorm Encounter

A pilot should avoid flying through a thunderstorm of any intensity. However, certain conditions may be present that could lead to an inadvertent thunderstorm encounter. For example, flying in areas where thunderstorms are embedded in large cloud masses may make thunderstorm avoidance difficult, even when the aircraft is equipped with thunderstorm detection equipment. Therefore, pilots must be prepared to deal with an inadvertent thunderstorm penetration. At the very least, a thunderstorm encounter will subject the aircraft to turbulence that could be severe. The pilot, as well as the passengers, should tighten seat belts and shoulder harnesses and secure any loose items in the cabin.

Emergency: A distress or urgent condition.

As with any emergency, the first order of business during an inadvertent thunderstorm encounter must be to fly the aircraft. The pilot workload will be high; therefore, increased con-centration is necessary to maintain an instrument scan. Once you enter a thunderstorm, it is better to maintain a course straight through the thunderstorm rather than turning around. A straight course will most likely get you out of the hazard in the least amount of time, and turning maneuvers will only increase structural stress on the aircraft.

Reduce power to a setting that will maintain a speed at the recommended turbulence penetration speed as described in the Pilot’s Operating Handbook/Airplane Flight Manual (POH/AFM), and try to minimize additional power ad-justments. Concentrate on keeping the aircraft in a level attitude while allowing airspeed and altitude to fluctuate. Similarly, if using the autopilot, disengage the altitude hold and speed hold modes, as they will only increase the aircraft’s maneuvering—thereby increasing structural stress.

During a thunderstorm encounter, the potential for icing also exists. As soon as possible, turn on anti-icing/deicing equip-ment and carburetor heat, if equipped. Icing can be rapid at any altitude and may lead to power failure and/or loss of airspeed indication.

Lightning will also be present in a thunderstorm and can temporarily blind a pilot. To reduce this risk, turn up cockpit lights to the highest intensity, concentrate on the flight instruments, and resist the urge to look outside.

Inadvertent Icing Encounter

Because icing is unpredictable in nature, pilots may find themselves in icing conditions even though they have done everything to avoid it. In order to stay alert to this possibility while operating in visible moisture, pilots should monitor the outside air temperature (OAT).

Proper utilization of the anti-icing/deicing equipment is critical to the safety of the flight. If the anti-icing/deicing equipment is used before sufficient ice has accumulated, the equipment may not be able to remove all of the ice accumu-lation. Refer to the POH/AFM for the proper use of anti-icing/ deicing equipment.

Prior to entering visible moisture with temperatures at 5° above freezing or cooler, activate the appropriate anti-icing/deicing equipment in anticipation of ice accumulation—early ice detection is critical. This may be particularly difficult during night flight. You may need to use a flashlight to check for ice accumulation on the wings. At the first indication of ice accumulation, you must act to get out of the icing conditions.

There are four options for action once ice has begun to accumulate on the aircraft:

Move to an altitude with significantly colder temperatures;
Move to an altitude with temperatures that are above freezing;
Fly to an area clear of visible moisture; or
Change heading and fly to an area of known nonicing conditions.

If none of these options are available, you must consider an immediate landing at the nearest suitable airport. Anti-icing/ deicing equipment is not designed to allow aircraft to operate in icing conditions indefinitely. Anti-icing/deicing equip-ment will simply give you more time to get out of the icing conditions.

Precipitation Static

Precipitation static, often referred to as P-static, occurs when accumulated static electricity is discharged from the extremities of the aircraft. This discharge has the potential to create problems for the instrument pilot. These problems range from the serious, such as the complete loss of very-high

Precipitation static: A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it.

frequency (VHF) communications and erroneous magnetic compass readings, to the annoyance of high-pitched audio squealing, and St. Elmo’s Fire. [Figure 11-1]

Precipitation static is caused when an aircraft encounters airborne particles during flight (e.g., rain or snow), and de-velops a negative charge. It can also result from atmospheric electric fields in thunderstorm clouds. When a significant negative voltage level is reached, the aircraft will discharge it, which can create electrical disturbances.

To reduce the problems associated with P-static, the pilot should ensure the aircraft’s static wicks are properly maintained and accounted for. Broken or missing static wicks should be replaced before an instrument flight. [Figure 11-2]

St. Elmo’s Fire: A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.

Aircraft System Malfunctions

Preventing aircraft system malfunctions that might lead to an inflight emergency begins with a thorough preflight inspection. In addition to those items normally checked prior to a visual flight rule (VFR) flight, pilots intending to fly under instrument flight rules (IFR) should pay particular attention to the alternator belt, antennas, static wicks, anti-icing/deicing equipment, pitot tube, and static ports.

During taxi, verify the operation and accuracy of all flight instruments. In addition, during the runup, verify that the operation of the pneumatic system is within acceptable parameters. It is critical that all systems are determined to be operational before departing into IFR conditions.

Alternator/Generator Failure

Depending upon theaircraft being flown, an alternator failure is indicated in different ways. Some aircraft use an ammeter that indicates the state of charge or discharge of the battery. [Figure 11-3] A positive indication on the ammeter indicates a charge condition; a negative indication reveals a discharge condition. Other aircraft use a loadmeter to indicate the load being carried by the alternator. [Figure 11-4] If the alternator were to fail, then a zero load indication is shown on the loadmeter. Sometimes an indicator light is also installed in the aircraft to alert the pilot to an alternator failure. Review the appropriate POH/AFM for information on the type of systems installed in your aircraft.

Ammeter: An instrument installed in Loadmeter: A type of ammeter series with an electrical load to installed between the generator measure the amount of current output and the main bus in an aircraft flowing through the load. electrical system.

Once an alternator failure has been detected, the pilot must reduce the electrical load on the battery and land as soon as practical. Depending upon the electrical load and condition of the battery, there may be sufficient power available for an hour or more of flight—or for only a matter of minutes. You should also be familiar with what systems on the aircraft are electric and which continue to operate without electrical power. The pilot can attempt to troubleshoot the alternator failure by following the established alternator failure procedure published in the POH/AFM. If the alternator cannot be reset, advise ATC of the situation and inform them of the impending electrical failure.

Instrument Failure

System or instrument failure is usually identified by a warning indicator or an inconsistency between the indications on the attitude indicator and the supporting performance instruments. Aircraft control must be maintained while identifying the failed component(s). Expedite the cross-check and include all the flight instruments. The problem may be individual instrument failure or a system failure that affects several instruments.

One method of identification involves an immediate comparison of the attitude indicator with the rate-of-turn indicator and vertical speed indicator (VSI). Along with providing pitch-and-bank information, this technique compares the static system with the suction or pressure system and the electrical system. Identify the failed component(s) and use the remaining functional instruments to maintain aircraft control.

Attempt to restore the inoperative components(s) by checking the appropriate power source, changing to a backup or alternate system, and resetting the instrument if possible. Covering the failed instrument(s) may enhance your ability to maintain aircraft control and navigate the aircraft. Usually the next step is to advise ATC of the problem and, if necessary, declare an emergency before the situation deteriorates beyond your ability to recover.

Pneumatic System Failure

One possible cause of instrument failure is a loss of the suction or pressure source. This pressure or suction is supplied by a vacuum pump mechanically driven off the engine. Occasionally, these pumps fail, leaving the pilot with inoperative attitude and heading indicators. [Figure 11-5] Many small aircraft are not equipped with a warning system for vacuum failure; therefore, the pilot should monitor the system’s vacuum/pressure gauge. This can be a hazardous situation with the potential to lead the unsuspecting pilot into a dangerous unusual attitude—which would require a partial panel recovery. It is important pilots practice instrument flight without reference to the attitude and heading indicators in preparation for such a failure.

Pitot/Static System Failure

A pitot or static system failure can also cause erratic and un-reliable instrument indications. When a static system problem occurs, it will affect the airspeed indicator, altimeter, and the VSI. In most aircraft, provisions have been made for the pilot to select an alternate static source. Check the POH/AFM for the location and operation of the alternate static source. In the absence of an alternate static source, in an unpressurized aircraft, the pilot could break the glass on the VSI. The VSI is not required for instrument flight and breaking the glass will provide the altimeter and the airspeed indicator a source of static pressure. This procedure could cause additional instrument errors.

Communication/Navigation System Malfunction

Avionics equipment has become very reliable, and the like-lihood of a complete communications failure is remote. However, each IFR flight should be planned and executed in anticipation of a two-way radio failure. At any given point during a flight, the pilot must know exactly what route to fly, what altitude to fly, and when to continue beyond a clearance limit. Title 14 of the Code of Federal Regulations (14 CFR) part 91 describes the procedures to be followed in case of a two-way radio communications failure. If the pilot is operating

Clearance limit: The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance.

in VFR conditions at the time of the failure, the pilot should continue the flight under VFR and land as soon as practicable. If the failure occurs in IFR conditions, or if VFR conditions cannot be maintained, the pilot must continue the flight:

Along the route assigned in the last ATC clearance received;
If being radar vectored, by the direct route from the point of radio failure to the fix, route, or airway specified in the vector clearance;
In the absence of an assigned route, by the route that ATC has advised may be expected in a further clearance; or
In the absence of an assigned route or a route that ATC has advised may be expected in a further clearance, by the route filed in the flight plan.

The pilot should maintain the highest of the following altitudes or flight levels for the route segment being flown:

The altitude or flight level assigned in the last ATC clearance received;
The minimum altitude (converted, if appropriate, to minimum flight level as prescribed in part 91 for IFR operations); or
The altitude or flight level ATC has advised may be expected in a further clearance.

In addition to route and altitude, the pilot must also plan the progress of the flight to leave the clearance limit:

When the clearance limit is a fix from which an approach begins, commence descent or descent and approach as close as possible to the expect-further-clearance time if one has been received; or if one has not been received, as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time en route.
If the clearance limit is not a fix from which an approach begins, leave the clearance limit at the expect-further-clearance time if one has been received; or if none has been received, upon arrival over the clearance limit, and proceed to a fix from which an approach begins and commence descent or descent and approach as close as possible to the estimated time of arrival as calculated from the filed or amended (with ATC) estimated time en route.

While following these procedures, set the transponder to code 7600 and use all means possible to re-establish two-way radio communication with ATC. This includes monitoring navigational aids (NAVAIDs), attempting radio contact with other aircraft, and attempting contact with a nearby automated flight service station (AFSS).

Loss of Situational Awareness (SA)

Situational awareness (SA) is not simply a mental picture of where you are; rather, it is an overall assessment of each element of the environment and how it will affect your flight. On one end of the SA spectrum is a pilot who is know-ledgeable of every aspect of the flight; consequently, this pilot’s decision making is proactive. With good SA, this pilot is able to make decisions well ahead of time and evaluate several different options. On the other end of the SA spectrum is a pilot who is missing important pieces of the puzzle: “I knew exactly where I was when I ran out of fuel.” Con-sequently, this pilot’s decision making is reactive. With poor SA, this pilot lacks a vision of future events and is forced to make decisions quickly, often with limited options.

During a typical IFR flight, a pilot will operate at varying levels of SA. For example, a pilot may be cruising to his/her destination with a high level of SA when ATC issues an unexpected standard terminal arrival route (STAR). Since the pilot was not expecting the STAR and is not familiar with it, SA is lowered. However, after becoming familiar with the STAR and resuming normal navigation, the pilot returns to a higher level of SA.

Factors that reduce SA include: distractions, unusual or unexpected events, complacency, high workload, unfamiliar situations, and inoperative equipment. In some situations, a loss of SA may be beyond a pilot’s control. For example, with a pneumatic system failure and associated loss of the attitude and heading indicators, a pilot may find his/her aircraft in an unusual attitude. In this situation, established procedures must be used to regain SA.

As a pilot, you should be alert to a loss of SA any time you find yourself in a reactive mindset. To regain SA, you must re-assess your situation and work toward understanding. This may mean you need to seek additional information from other sources, such as the navigation instruments or ATC.

Appendix 1

Clearance Shorthand

The following shorthand system is recommended by the Federal Aviation Administration (FAA). Applicants for the Instrument Rating may use any shorthand system, in any language, which ensures accurate compliance with air traffic control (ATC) instructions. No shorthand system is required by regulation and no knowledge of shorthand is required for the FAA Knowledge Test; however, because of the vital need for reliable communication between the pilot and controller, clearance information should be unmistakably clear.

The following symbols and contractions represent words and phrases frequently used in clearances. Most of them are used regularly by ATC personnel. By practicing this shorthand, omitting the parenthetical words, you will be able to copy long clearances as fast as they are read.

Example: CAF

RH RV V18

40 SQ 0700 DPC 120.4 Cleared as filed, maintain runway heading for radar vector to Victor 18, climb to 4,000, squawk 0700, departure control frequency is 120.4.

Words and Phrases Shorthand

Above ......................................................................... ABVAbove (Altitude, Hundreds of Feet) ................................ 70

Adjust speed to 250 knots..........................................250 K

Advise ......................................................................... ADZ

After (Passing) .................................................................. <

Airway (Designation) ................................................... V26

Airport .............................................................................. A

Alternate Instructions ...................................................... ( )

Altitude 6,000-17,000 .............................................. 60-170

And .................................................................................. &

Approach ....................................................................... AP

Approach Control ........................................................ APC

Area Navigation........................................................RNAV

Arriving .............................................................................At ..................................................................................... @At or Above ....................................................................At or Below ....................................................................(ATC) Advises ............................................................... CA(ATC) Clears or Cleared ................................................... C(ATC) Requests ............................................................. CRBack Course................................................................... BCBearing .......................................................................... BRBefore (Reaching, Passing) .............................................. >Below...........................................................................BLOBelow (Altitude, Hundreds of Feet) ................................70
Center .......................................................................... CTRClearance Void if Not Off By (time) .............................. v<Cleared as Filed ........................................................... CAFCleared to Airport ............................................................. ACleared to Climb/Descend at Pilot’s Discretion ............ PDCleared to Cross ............................................................... XCleared to Depart From the Fix ........................................ DCleared to the Fix ............................................................. FCleared to Hold and Instructions Issued ........................... HCleared to Land ................................................................ LCleared to the Outer Marker ............................................. OClimb to (Altitude, Hundreds of Feet) .........................Contact Approach .......................................................... CTContact (Denver) Approach Control ............................(denContact (Denver) Center............................................ (DENCourse .......................................................................... CRS

Cross ................................................................................. XCruise..............................................................................Delay Indefinite ............................................................ DLIDepart (direction, if specified) ................................ T

( ) Departure Control ........................................................ DPC Descend To (Altitude, Hundreds of Feet) ......................

70 Direct ............................................................................. DR Direction (Bound)

Eastbound ............................................................... EB

Westbound ............................................................. WB

Northbound............................................................. NB

Southbound..............................................................SB

Inbound.....................................................................IB

Outbound ................................................................ OBDME Fix (Mile) .............................................................Each ............................................................................... EAEnter Control Area ........................................................Estimated Time of Arrival ........................................... ETAExpect ............................................................................ EXExpect-Further-Clearance ............................................ EFCFan Marker .................................................................... FMFinal .................................................................................. FFinal Approach ............................................................... FAFlight Level .................................................................... FLFlight Planned Route ................................................... FPRFor Further Clearance .................................................. FFCFor Further Headings ................................................... FFHFrom .............................................................................. FMGround ........................................................................ GNDGPS Approach ............................................................. GPSHeading....................................................................... HDGHold (Direction) ..........................................................H-WHolding Pattern .............................................................

ILS Approach.................................................................ILSIncrease Speed 30 Knots .......................................... +30 KInitial Approach ................................................................. IInstrument Departure Procedure.................................... DPIntersection .................................................................... XNJoin or Intercept Airway/

Jet Route/Track or Course.............................................Left Turn After Takeoff ....................................................Locator Outer Marker ................................................. LOMMagnetic .......................................................................... MMaintain........................................................................Maintain VFR Conditions On Top .............................. VFR
Middle Compass Locator .............................................. MLMiddle Marker ............................................................. MMMissed Approach .......................................................... MANondirectional Beacon Approach............................... NDBOut of (Leave) Control Area........................................Outer Marker ................................................................ OMOver (Station) ............................................................. OKC
On Course ...................................................................... OCPrecision Approach Radar ........................................... PARProcedure Turn ............................................................... PTRadar Vector .................................................................. RVRadial (080° Radial) ................................................... 080RReduce Speed 20 Knots ............................................. -20 KRemain This Frequency................................................RTFRemain Well to Left Side ............................................... LSRemain Well to Right Side ............................................. RSReport Crossing ............................................................. RXReport Departing ........................................................... RDReport Leaving .............................................................. RLReport on Course ..................................................... R-CRSReport Over ................................................................... RO

Report Passing ................................................................ RPReport Reaching ............................................................ RRReport Starting Procedure Turn ................................. RSPTReverse Course .............................................................. RCRight Turn After Takeoff ..................................................Runway Heading ........................................................... RHRunway (Number) ..................................................... RY18Squawk .......................................................................... SQStandby ..................................................................... STBYStraight-in Approach ....................................................... SISurveillance Radar Approach ...................................... ASRTakeoff (Direction) ................................................... T

N Tower ................................................................................ Z

Turn Left ......................................................................... TLTurn Right...................................................................... TRUntil ................................................................................... /Until Advised (By) ........................................................ UAUntil Further Advised .................................................. UFAVFR Conditions On Top .............................................. OTPVia.................................................................................VIAVictor (Airway Number) .............................................. V14Visual Approach ............................................................ VAVOR...............................................................................VOR Approach .............................................................. VRVORTAC .......................................................................While in Control Area ..................................................

Appendix 2

Instrument Training Lesson Guide

Introduction

Flight instructors may use this guide in the development of lesson plans. The lessons are arranged in a logical learning sequence and use the building-block technique. Each lesson includes ground training appropriate to the flight portion of the lesson. It is vitally important that the flight instructor brief the student on the objective of the lesson and how it will be accomplished. Debriefing the student’s performance is also necessary to motivate further progress. To ensure steady progress, student pilots should master the objective of each lesson before advancing to the next lesson. Lessons should be arranged to take advantage of each student’s knowledge and skills.

Flight instructors must monitor progress closely during training to guide student pilots in how to properly divide their attention. The importance of this division of attention or “cross-check” cannot be overemphasized. Cross-check and proper instrument interpretation are essential components of “attitude instrument flying” that enables student pilots to accurately visualize the aircraft’s attitude at all times.

When possible, each lesson should incorporate radio communications, basic navigation, and emergency procedures so the student pilot is exposed to the entire IFR experience with each flight. Cross-reference the Instrument Training Lesson Guide with this handbook and the Instrument Practical Test Standards for a comprehensive instrument rating training program.

Lesson 1—Ground and flight evaluation of student’s knowledge and performance

Aircraft systems Aircraft performance Preflight planning Use of checklists Basic flight maneuvers Radio communications procedures Navigation systems

Lesson 2—Preflight preparation and flight by reference to instruments

Ground Training

Instrument system preflight procedures Attitude instrument flying Fundamental instrument skills Instrument cross-check techniques

Flight Training

Aircraft and instrument preflight inspection Use of checklists Fundamental instrument skills Basic flight maneuvers Instrument approach (demonstrated) Postflight procedures

Lesson 3—Flight instruments and human factors

Ground Training

Human factors Flight instruments and systems Aircraft systems Navigation instruments and systems

Flight Training

Aircraft and instrument preflight inspection Radio communications Checklist procedures Attitude instrument flying Fundamental instrument skills Basic flight maneuvers Spatial disorientation demonstration Navigation systems Postflight procedures

Lesson 4—Attitude instrument flying

Ground Training

Human factors Flight instruments and systems Aircraft systems Navigation instruments and systems Attitude instrument flying Fundamental instrument skills Basic flight maneuvers

Flight Training

Aircraft and instrument preflight inspection Checklist procedures Radio communications Attitude instrument flying Fundamental instrument skills Basic flight maneuvers Spatial disorientation Navigation Postflight procedures

Lesson 5—Aerodynamic factors and basic flight maneuvers

Ground Training

Basic aerodynamic factors Basic instrument flight patterns Emergency procedures

Flight Training

Aircraft and instrument preflight inspection Checklist procedures Radio communications Basic instrument flight patterns Emergency procedures Navigation Postflight procedures

Lesson 6—Partial-panel operations

Ground Training

ATC system Flight instruments Partial-panel operations

Flight Training

Aircraft and instrument preflight inspection Checklist procedures Radio communications Basic instrument flight patterns Emergency procedures Partial-panel practice Navigation Postflight procedures

Lesson 7—Recovery from unusual attitudes

Ground Training

Attitude instrument flying ATC system NAS overview

Flight Training

Preflight Aircraft and instrument preflight inspection Checklist procedures Radio communications Instrument takeoff Navigation Partial-panel practice Recovery from unusual attitudes Postflight procedures

Lesson 8—Navigation systems

Ground Training

ATC clearances Departure procedures IFR en route charts

Flight Training

Aircraft and instrument preflight inspection Checklist procedures Radio communications Intercepting and tracking Holding Postflight procedures

Lesson 9—Review and practice

Ground Training

Aerodynamic factors Flight instruments and systems Attitude instrument flying Navigation systems NAS ATC Emergency procedures

Flight Training

Aircraft and instrument preflight inspection Checklist procedures Radio communications Review and practice as determined by the flight instructor Instrument takeoff Radio communications Navigation systems Emergency procedures Postflight procedures

Lessons 10 through 19—Orientation, intercepting, tracking, and holding using each navigation system installed in the aircraft

Ground Training

Preflight planning Navigation systems NAS ATC Emergencies

Flight Training

Aircraft and instrument preflight inspection Checklist procedures Radio communications Departure procedures En route navigation Terminal operations Partial-panel operation Instrument approach Missed approach Approach to a landing Postflight procedures

Lessons 20 and 21—Cross-country flights

Ground Training

Preflight planning Aircraft performance Navigation systems NAS ATC Emergencies

Flight Training

Emergency procedures Partial-panel operation Aircraft and instrument preflight inspection Checklist procedures Radio communications Departure procedures En route navigation Terminal operations Instrument approach Missed approach Approach to a landing Postflight procedures

Lessons 22 and 23—Review and practice

Ground Training

Human factors Aerodynamic factors Flight instruments and systems Attitude instrument flying Basic flight maneuvers Navigation systems NAS ATC Emergency operations

Flight Training

Aircraft and instrument preflight inspection Checklist procedures Radio communications Review and practice as determined by the flight instructor Instrument takeoff Partial-panel operations Unusual attitude recoveries Radio communications Navigation systems Emergency procedures Postflight procedures

Lessons 24 and subsequent—Practical test preparation

Ground Training

Title 14 of the Code of Federal Regulations (14 CFR) parts 61, 71, 91, 95, and 97

Instrument Flying Handbook

Practical test standards Administrative requirements Equipment requirements Applicant’s requirements

Flight Training

Review and practice until the student can consistently perform all required tasks in accordance with the appropriate practical test standards.

NOTE: It is the recommending instructor’s responsibility to ensure that the applicant meets part 61 requirements and is prepared for the practical test,including: training, knowledge, experience, and the appropriate instructor endorsements.

absolute altitude. The actual distance between an aircraft and the terrain over which it is flying.

absolute pressure. Pressure measured from the reference of zero pressure, or a vacuum.

a.c. Alternating current.

acceleration error. A magnetic compass error that shows up when the aircraft accelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward North.

accelerometer. A part of an inertial navigation system (INS) that accurately measures the force of acceleration in one direction.

ADF. See automatic direction finder.

ADI. See attitude director indicator.

ADM. See aeronautical decision making.

adverse yaw. A flight condition at the beginning of a turn in which the nose of the aircraft starts to move in the direction opposite the direction the turn is being made, caused by the induced drag produced by the downward-deflected aileron holding back the wing as it begins to rise.

aeronautical decision making (ADM). A systematic approach to the mental process used by pilots to consistently determine the best course of action in response to a given set of circumstances.

A/FD. See Airport/Facility Directory.

agonic line. An irregular imaginary line across the surface of the Earth along which the magnetic and geographic poles are in alignment, and along which there is no magnetic variation.

aircraft approach category. A performance grouping of aircraft based on a speed of 1.3 times their stall speed in the landing configuration at maximum gross landing weight.

AIRMET. In-flight weather advisory issued as an amend-ment to the area forecast, concerning weather phenomena of operational interest to all aircraft and is potentially hazardous to aircraft with limited capability due to lack of equipment, instrumentation, or pilot qualifications.

airport diagram. The section of an instrument approach procedure chart that shows a detailed diagram of the airport including surface features and airport configuration infor-mation.

Airport/Facility Directory (A/FD). An FAA publication containing information on all airports, communications, and NAVAIDs.

airport surface detection equipment (ASDE). Radar equipment specifically designed to detect all principal features and traffic on the surface of an airport, presenting the entire image on the control tower console; used to aug-ment visual observation by tower personnel of aircraft and/ or vehicular movements on runways and taxiways.

airport surveillance radar (ASR). Approach control radar used to detect and display an aircraft’s position in the terminal area.

airport surveillance radar approach. An instrument approach in which ATC issues instructions for pilot com-pliance based on aircraft position in relation to the final approach course, and the distance from the end of the runway as displayed on the controller’s radar scope.

air route surveillance radar (ARSR). Air route traffic con-trol center (ARTCC) radar used primarily to detect and display an aircraft’s position while en route between terminal areas.

air route traffic control center (ARTCC). Provides ATC service to aircraft operating on IFR flight plans within con-trolled airspace and principally during the en route phase of flight.

airways. Based on a centerline that extends from one naviga-tion aid or intersection to another navigation aid (or through several navigation aids or intersections); used to establish a known route for en route procedures between terminal areas.

alert area. An area in which there is a high volume of pilot training or an unusual type of aeronautical activity.

almanac data. Information the GPS receiver can obtain from one satellite which describes the approximate orbital position-ing of all satellites in the constellation. This information is necessary for the GPS receiver to know what satellites to look for in the sky at a given time.

ALS. See approach lighting system.

alternate airport. Designated in an IFR flight plan, provides a suitable destination if a landing at the intended airport becomes inadvisable.

alternate static source valve. A valve in the instrument static air system that supplies reference air pressure to the altimeter, airspeed indicator, and vertical speed indicator if the normal static pickup should become clogged or iced over. This valve is accessible to the pilot in flight.

altimeter setting. Station pressure (the barometric pressure at the location the reading is taken) which has been corrected for the height of the station above sea level.

amendment status. The circulation date and revision number of an instrument approach procedure, printed above the procedure identification.

ammeter. An instrument installed in series with an electrical load to measure the amount of current flowing through the load.

aneroid. The sensitive component in an altimeter or baro-meter that measures the absolute pressure of the air. It is a sealed, flat capsule made of thin disks of corrugated metal soldered together and evacuated by pumping all of the air out of it.

aneroid barometer. An instrument that measures the absolute pressure of the atmosphere by balancing the weight of the air above it against the spring action of the aneroid.

angle of attack. The acute angle formed between the chord line of an airfoil and the direction of the air that strikes the airfoil.

anti-ice. System designed to prevent the accumulation of ice on an aircraft structure.

approach lighting system (ALS). Provides lights that will penetrate the atmosphere far enough from touchdown to give directional, distance, and glidepath information for safe transition from instrument to visual flight.

area chart. Part of the low-altitude en route chart series, these charts furnish terminal data at a larger scale for congested areas.

area navigation (RNAV). Allows a pilot to fly a selected course to a predetermined point without the need to overfly ground-based navigation facilities, by using waypoints.

ARSR. See air route surveillance radar.

ARTCC. See air route traffic control center.

ASDE. See airport surface detection equipment.

ASR. See airport surveillance radar.

ATC. Air Traffic Control.

atmospheric propagation delay. A bending of the electro-magnetic (EM) wave from the satellite that creates an error in the GPS system.

attitude director indicator (ADI). An aircraft attitude indicator that incorporates flight command bars to provide pitch and roll commands.

attitude indicator. The basis for all instrument flight, this instrument reflects the airplane’s attitude in relation to the horizon.

attitude instrument flying. Controlling the aircraft by reference to the instruments rather than outside visual cues.

autokinesis. Nighttime visual illusion that a stationary light is moving, which becomes apparent after several seconds of staring at the light.

automatic direction finder (ADF). Electronic navigation equipment that operates in the low- and medium-frequency bands. Used in conjunction with the ground-based non-directional beacon (NDB), the instrument displays the number of degrees clockwise from the nose of the aircraft to the station being received.

back course (BC). The reciprocal of the localizer course for an ILS. When flying a back-course approach, an aircraft approaches the instrument runway from the end at which the localizer antennas are installed.

barometric scale. A scale on the dial of an altimeter to which the pilot sets the barometric pressure level from which the altitude shown by the pointers is measured.

BC. See back course.

block altitude. A block of altitudes assigned by ATC to allow altitude deviations; for example, “Maintain block altitude 9 to 11 thousand.”

cage. The black markings on the ball instrument indicating its neutral position.

calibrated. The instrument indication was compared with a standard value to determine the accuracy of the instrument.

calibrated orifice. A hole of specific diameter used to delay the pressure change in the case of a vertical speed indicator.

CDI. Course deviation indicator.

changeover points (COPs). A point along the route or airway segment between two adjacent navigation facilities or way-points where changeover in navigation guidance should occur.

circling approach. A maneuver initiated by the pilot to align the aircraft with a runway for landing when a straight-in landing from an instrument approach is not possible or is not desirable.

Class Aairspace. Airspace from 18,000 feet MSL up to and including FL600, including the airspace overlying the waters within 12 NM of the coast of the 48 contiguous states and Alaska; and designated international airspace beyond 12 NM of the coast of the 48 contiguous states and Alaska within areas of domestic radio navigational signal or ATC radar coverage, and within which domestic procedures are applied.

Class B airspace. Airspace from the surface to 10,000 feet MSL surrounding the nation’s busiest airports in terms of IFR operations or passenger numbers. The configuration of each Class B airspace is individually tailored and consists of a surface area and two or more layers, and is designed to contain all published instrument procedures once an aircraft enters the airspace. For all aircraft, an ATC clearance is required to operate in the area, and aircraft so cleared receive separation services within the airspace.

Class C airspace. Airspace from the surface to 4,000 feet above the airport elevation (charted in MSL) surrounding those airports having an operational control tower, serviced by radar approach control, and having a certain number of IFR operations or passenger numbers. Although the config-uration of each Class C airspace area is individually tailored, the airspace usually consists of a 5 NM radius core surface area that extends from the surface up to 4,000 feet above the airport elevation, and a 10 NM radius shelf area that extends from 1,200 feet to 4,000 feet above the airport elevation.

Class D airspace. Airspace from the surface to 2,500 feet above the airport elevation (charted in MSL) surrounding those airports that have an operational control tower. The configuration of each Class D airspace area is individually tailored, and when instrument procedures are published, the airspace will normally be designed to contain the procedures.

Class E airspace. Airspace that is not Class A, Class B, Class C, or Class D, and it is controlled airspace.

Class G airspace. Airspace that is uncontrolled, except when associated with a temporary control tower, and has not been designated as Class A, Class B, Class C, Class D, or Class E airspace.

clean configuration. An aircraft in a clean configuration is one in which all flight control surfaces have been placed so as to create minimum drag; in most aircraft this means flaps and gear retracted.

clearance. Allows an aircraft to proceed under specified traffic conditions within controlled airspace, for the purpose of providing separation between known aircraft.

clearance delivery. Control tower position responsible for transmitting departure clearances to IFR flights.

clearance limit. The fix, point, or location to which an aircraft is cleared when issued an air traffic clearance.

clearance on request. After filing a flight plan, the IFR clearance has not yet been received but it is pending.

clearance void time. Used by ATC to advise an aircraft that the departure clearance is automatically canceled if takeoff is not made prior to a specified time. The pilot must obtain a new clearance or cancel the IFR flight plan if not off by the specified time.

clear ice. Glossy, clear, or translucent ice formed by the rel-atively slow freezing of large supercooled water droplets.

compass course. A true course corrected for variation and deviation errors.

compass locator. A low-power, low- or medium-frequency (L/MF) radio beacon installed at the site of the outer or middle marker of an ILS.

compass rose. A small circle graduated in 360° increments printed on navigational charts to show the amount of compass variation at different locations, or on instruments to indicate direction.

computer navigation fix. A point used to define a navigation track for an airborne computer system such as GPS or FMS.

concentric rings. The dashed-line circles depicted in the plan view of IAP charts, outside of the reference circle, that show en route and feeder facilities.

cone of confusion. A cone-shaped volume of airspace directly above a VOR station where no signal is received causing the CDI to fluctuate.

control and performance. A method of attitude instrument flying in which one instrument is used for making attitude changes, and the other instruments are used to monitor the progress of the change.

controlled airspace. An airspace of defined dimensions within which ATC service is provided to IFR and VFR flights in accordance with the airspace classification. Includes Class A, Class B, Class C, Class D, and Class E airspace.

control pressures. The amount of physical exertion on the control column necessary to achieve the desired aircraft attitude.

convective. Unstable, rising air—cumiliform clouds.

convective SIGMET. Weather advisory concerning con-vective weather significant to the safety of all aircraft, including thunderstorms, hail, and tornadoes.

coordinated. Using the controls to maintain or establish various conditions of flight with (1) a minimum disturbance of the forces maintaining equilibrium, or (2) the control action necessary to effect the smoothest changes in equilibrium.

COPs. See changeover points.

Coriolis illusion. An abrupt head movement, while in a prolonged constant-rate turn that has ceased stimulating the motion sensing system, can create the illusion of rotation or movement in an entirely different axis.

crew resource management (CRM). The effective use of all available resources—human resources, hardware, and information.

critical areas. Areas where disturbances to the ILS localizer and glide-slope courses may occur when surface vehicles or aircraft operate near the localizer or glide-slope antennas.

CRM. See crew resource management.

cross-check. The first fundamental skill of instrument flight, also known as “scan”; the continuous and logical observation of instruments for attitude and performance information.

cruise clearance. Used in an ATC clearance to allow a pilot to conduct flight at any altitude from the minimum IFR alti-tude up to and including the altitude specified in the clearance. Also authorizes a pilot to proceed to and make an approach at the destination airport.

current induction. An electrical current is induced into, or generated in, any conductor that is crossed by lines of flux from any magnet.

DA. See decision altitude.

d.c. Direct current.

dark adaptation. Physical and chemical adjustments of the eye that make vision possible in relative darkness.

deceleration error. A magnetic compass error that shows up when the aircraft decelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward South.

decision altitude (DA). A specified altitude in the precision approach, charted in feet MSL, at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.

decision height (DH). A specified altitude in the precision approach, charted in height above threshold elevation, at which a decision must be made to either continue the approach or to execute a missed approach.

deice. System designed to remove ice accumulation from an aircraft structure.

density altitude. Pressure altitude corrected for nonstandard temperature. Density altitude is used for computing the performance of an aircraft and its engines.

departure procedure (DP). Preplanned IFR ATC departure, published for pilot use, in textual and graphic format.

deviation. A magnetic compass error caused by local mag-netic fields within the aircraft. Deviation error is different on each heading.

DGPS. Differential global positioning system.

DH. See decision height.

direct indication. The true and instantaneous reflection of aircraft pitch-and-bank attitude by the miniature aircraft, relative to the horizon bar of the attitude indicator.

direct user access terminal system (DUATS). Provides current FAA weather and flight plan filing services to certified civil pilots, via a personal computer, modem, and telephone access to the system. Pilots can request specific types of weather briefings and other pertinent data for planned flights.

distance circle. See reference circle.

distance measuring equipment (DME). A pulse-type electronic navigation system that shows the pilot, by an instrument-panel indication, the number of nautical miles between the aircraft and a ground station or waypoint.

DME. See distance measuring equipment.

DME arc. Flying a track that is a constant distance from the station or waypoint.

DOD. Department of Defense.

doghouse. A mark on the dial of a turn-and-slip indicator that has the shape of a doghouse.

double gimbal. A type of mount used for the gyro in an attitude instrument. The axes of the two gimbals are at right angles to the spin axis of the gyro, allowing free motion in two planes around the gyro.

DP. See departure procedure.

DUATS. See direct user access terminal system.

duplex. Transmitting on one frequency and receiving on a separate frequency.

eddy currents. Current induced in a metal cup or disc when it is crossed by lines of flux from a moving magnet.

EFAS. See En route Flight Advisory Service.

EFC. See expect-further-clearance.

elevator illusion. The feeling of being in a climb or descent, caused by the kind of abrupt vertical accelerations that result from up- or downdrafts.

emergency. A distress or urgent condition.

emphasis error. Giving too much attention to a particular instrument during the cross-check, instead of relying on a combination of instruments necessary for attitude and performance information.

EM wave. Electromagnetic wave.

encoding altimeter. A special type of pressure altimeter used to send a signal to the air traffic controller on the ground, showing the pressure altitude the aircraft is flying.

en route facilities ring. A circle depicted in the plan view of IAP charts, which designates NAVAIDs, fixes, and inter-sections that are part of the en route low altitude airway structure.

En route Flight Advisory Service (EFAS). An en route weather-only AFSS service.

en route high-altitude charts. Aeronautical charts for en route instrument navigation at or above 18,000 feet MSL.

en route low-altitude charts. Aeronautical charts for en route IFR navigation below 18,000 feet MSL.

inverter. A solid-state electronic device that converts electrical current from d.c. into a.c. to operate a.c. gyro-instruments.

expect-further-clearance (EFC). The time a pilot can expect to receive clearance beyond a clearance limit.

FAF. See final approach fix.

false horizon. Inaccurate visual information for aligning the aircraft caused by various natural and geometric formations that disorient the pilot from the actual horizon.

federal airways. Class E airspace areas that extend upward from 1,200 feet to, but not including, 18,000 feet MSL, unless otherwise specified.

feeder facilities. NAVAIDs used by ATC to direct aircraft to intervening fixes between the en route structure and the initial approach fix.

final approach fix (FAF). The fix from which the IFR final approach to an airport is executed, and which identifies the beginning of the final approach segment. An FAF is desig-nated on government charts by the Maltese cross symbol for nonprecision approaches, and the lightning bolt symbol for precision approaches.

fixating. Staring at a single instrument, thereby interrupting the cross-check process.

FL. See flight level.

flight configurations. Adjusting the aircraft controls surfaces (including flaps and landing gear) in a manner that will achieve a specified attitude.

flight level (FL). A measure of altitude used by aircraft flying above 18,000 feet with the altimeter set at 29.92" Hg.

flight management system (FMS). Provides pilot and crew with highly accurate and automatic long-range navigation capability, blending available inputs from long- and short-range sensors.

flightpath. The line, course, or track along which an aircraft is flying or is intended to be flown.

flight patterns. Basic maneuvers, flown by reference to the instruments rather than outside visual cues, for the purpose of practicing basic attitude flying. The patterns simulate maneuvers encountered on instrument flights such as holding patterns, procedure turns, and approaches.

flight strips. Paper strips containing instrument flight information, used by ATC when processing flight plans.

FMS. See flight management system.

fundamental skills. Instrument cross-check, instrument interpretation, and aircraft control.

glide slope (GS). Part of the ILS that projects a radio beam upward at an angle of approximately 3°from the approach end of an instrument runway. The glide slope provides vertical guidance to aircraft on the final approach course for the aircraft to follow when making an ILS approach along the localizer path.

glide-slope intercept altitude. The minimum altitude of an intermediate approach segment prescribed for a precision approach that ensures obstacle clearance.

global positioning system (GPS). Navigation system that uses satellite rather than ground-based transmitters for location information.

goniometer. As used in radio frequency (RF) antenna sys-tems, a direction-sensing device consisting of two fixed loops of wire oriented 90°from each other, which sense received signal strength separately and send those signals to two rotors (also oriented 90°) in the sealed direction-indicating instrument. The rotors are attached to the direction-indicating needle of the instrument and rotated by a small motor until minimum magnetic field is sensed near the rotors.

GPS. See global positioning system.

GPS Approach Overlay Program. An authorization for pilots to use GPS avionics under IFR for flying designated existing nonprecision instrument approach procedures, with the exception of LOC, LDA, and SDF procedures.

graveyard spiral. The illusion of the cessation of a turn while actually still in a prolonged coordinated, constant-rate turn, which can lead a disoriented pilot to a loss of control of the aircraft.

great circle route. The shortest distance across the surface of a sphere (the Earth) between two points on the surface.

groundspeed. Speed over the ground; either closing speed to the station or waypoint, or speed over the ground in whatever direction the aircraft is going at the moment, depending upon the navigation system used.

GS. See glide slope.

HAA. See height above airport.

HAL. See height above landing.

HAT. See height above touchdown elevation.

hazardous attitudes. Five aeronautical decision-making attitudes that may contribute to poor pilot judgment are: antiauthority, impulsivity, invulnerability, macho, and resig-nation.

Hazardous Inflight WeatherAdvisory Service (HIWAS).

Recorded weather forecasts broadcast to airborne pilots over selected VORs.

head-up display (HUD). A special type of flight viewing screen that allows the pilot to watch the flight instruments and other data while looking through the windshield of the aircraft for other traffic, the approach lights, or the runway.

height above airport (HAA). The height of the MDA above the published airport elevation.

height above landing (HAL). The height above a designated helicopter landing area used for helicopter instrument approach procedures.

height above touchdown elevation (HAT). The DA/DH or MDA above the highest runway elevation in the touchdown zone (first 3,000 feet of the runway).

HF. High frequency.

HIWAS. See Hazardous Inflight Weather Advisory Service.

holding. A predetermined maneuver that keeps aircraft within a specified airspace while awaiting further clearance from ATC.

holding pattern. A racetrack pattern, involving two turns and two legs, used to keep an aircraft within a prescribed airspace with respect to a geographic fix. A standard pattern uses right turns; nonstandard patterns use left turns.

homing. Flying the aircraft on any heading required to keep the needle pointing directly to the 0°relative bearing position.

horizontal situation indicator (HSI). A flight navigation instrument that combines the heading indicator with a CDI, in order to provide the pilot with better situational awareness of location with respect to the courseline.

HSI. See horizontal situation indicator.

HUD. See head-up display.

human factors. A multidisciplinary field encompassing the behavioral and social sciences, engineering, and physiology, to consider the variables that influence individual and crew performance for the purpose of optimizing human perfor-mance and reducing errors.

hypoxia. A state of oxygen deficiency in the body sufficient to impair functions of the brain and other organs.

IAF. See initial approach fix.

IAP. See instrument approach procedures.

ICAO. See International Civil Aviation Organization.

ident. Push the button on the transponder to identify your return on the controller’s scope.

IFR. See instrument flight rules.

ILS. See instrument landing system.

ILS categories. Categories of instrument approach proce-dures allowed at airports equipped with the following types of instrument landing systems:

ILS Category I: Provides for approach to a height above touchdown of not less than 200 feet, and with runway visual range of not less than 1,800 feet.

ILS Category II: Provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet.

ILS Category IIIA: Provides for approach without a decision height minimum and with runway visual range of not less than 700 feet.

ILS Category IIIB: Provides for approach without a decision height minimum and with runway visual range of not less than 150 feet.

ILS Category IIIC: Provides for approach without a decision height minimum and without runway visual range minimum.

IMC. See instrument meteorological conditions.

indirect indication. A reflection of aircraft pitch-and-bank attitude by the instruments other than the attitude indicator.

induced drag. Drag caused by the same factors that produce lift; its amount varies inversely with airspeed. As airspeed decreases, the angle of attack must increase, and this increases induced drag.

inertial navigation system (INS). A computer-based navigation system that tracks the movement of an aircraft via signals produced by onboard accelerometers. The initial loca-tion of the aircraft is entered into the computer, and all subsequent movement of the aircraft is sensed and used to keep the position updated. An INS does not require any inputs from outside signals.

initial approach fix (IAF). The fix depicted on IAP charts where the IAP begins unless otherwise authorized by ATC.

inoperative components. Higher minimums are prescribed when the specified visual aids are not functioning; this information is listed in the Inoperative Components Table found in the U.S. Terminal Procedures Publications.

INS. See inertial navigation system.

instrument approach procedures (IAP). A series of predetermined maneuvers for the orderly transfer of an aircraft under IFR from the beginning of the initial approach to a landing or to a point from which a landing may be made visually.

instrument flight rules (IFR). Rules and regulations established by the Federal Aviation Administration to govern flight under conditions in which flight by outside visual reference is not safe. IFR flight depends upon flying by reference to instruments in the cockpit, and navigation is done by reference to electronic signals.

instrument landing system (ILS). An electronic system that provides both horizontal and vertical guidance to a specific runway, used to execute a precision instrument approach procedure.

instrument meteorological conditions (IMC). Meteoro-logical conditions expressed in terms of visibility, distance from cloud, and ceiling less than the minimums specified for visual meteorological conditions, requiring operations to be conducted under IFR.

instrument takeoff. Using the instruments rather than out-side visual cues to maintain runway heading and execute a safe takeoff.

International Civil Aviation Organization (ICAO). The United Nations agency for developing the principles and techniques of international air navigation, and fostering planning and development of international civil air transport.

inversion illusion. The feeling that the aircraft is tumbling backwards, caused by an abrupt change from climb to straight-and-level flight while in situations lacking visual reference.

inverter. A solid-state electronic device that converts d.c. into

a.c.: current of the proper voltage and frequency to operate
a.c.: gyro instruments.

isogonic lines. Lines drawn across aeronautical charts to connect points having the same magnetic variation.

jet route. A route designated to serve flight operations from 18,000 feet MSL, up to and including FL450.

jet stream. A high-velocity narrow stream of winds, usually found near the upper limit of the troposphere, which flows generally from west to east.

Kollsman window. A barometric scale window of a sensitive altimeter used to adjust the altitude for the altimeter setting.

LAAS. See local area augmentation system.

lag. The delay that occurs before an instrument needle attains a stable indication.

land as soon as possible. Land without delay at the nearest suitable area, such as an open field, at which a safe approach and landing is assured.

land as soon as practical. The landing site and duration of flight are at the discretion of the pilot. Extended flight beyond the nearest approved landing area is not recommended.

land immediately. The urgency of the landing is paramount. The primary consideration is to ensure the survival of the occupants. Landing in trees, water, or other unsafe areas should be considered only as a last resort.

LDA. See localizer-type directional aid.

lead radial. The radial at which the turn from the DME arc to the inbound course is started.

leans, the. An abrupt correction of a banked attitude, entered too slowly to stimulate the motion sensing system in the inner ear, can create the illusion of banking in the opposite direction.

lines of flux. Invisible lines of magnetic force passing be-tween the poles of a magnet.

LMM. See locator middle marker.

load factor. The ratio of a specified load to the total weight of the aircraft. The specified load is expressed in terms of any of the following: aerodynamic forces, inertia forces, or ground or water reactions.

loadmeter. A type of ammeter installed between the generator output and the main bus in an aircraft electrical system.

LOC. See localizer.

local area augmentation system (LAAS). A differential global positioning system(DGPS) that improves the accuracy of the system by determining position error from the GPS satellites, then transmitting the error, or corrective factors, to the airborne GPS receiver.

localizer (LOC). The portion of an ILS that gives left/right guidance information down the centerline of the instrument runway for final approach.

localizer-type directional aid (LDA). A NAVAID used for nonprecision instrument approaches with utility and accuracy comparable to a localizer but which is not a part of a complete ILS and is not aligned with the runway. Some LDAs are equipped with a glide slope.

locator middle marker (LMM). NDB compass locator, colocated with a MM.

locator outer marker (LOM). NDB compass locator, colo-cated with an OM.

LOM. See locator outer marker.

long range navigation (LORAN). An electronic naviga-tional system by which hyperbolic lines of position are determined by measuring the difference in the time of reception of synchronized pulse signals from two fixed transmitters. LORAN A operates in the 1750 to 1950 kHz frequency band. LORAN C and D operate in the 100 to 110 kHz frequency band.

LORAN. See long range navigation.

lubber line. The reference line used in a magnetic compass or heading indicator.

MAA. See maximum authorized altitude.

magnetic bearing (MB). The direction to or from a radio transmitting station measured relative to magnetic north.

magnetic heading (MH). The direction an aircraft is pointed with respect to magnetic north.

mandatory altitude. An altitude depicted on an instrument approach chart with the altitude value both underscored and overscored. Aircraft are required to maintain altitude at the depicted value.

mandatory block altitude. An altitude depicted on an instrument approach chart with two altitude values under-scored and overscored. Aircraft are required to maintain altitude between the depicted values.

MAP. See missed approach point.

margin identification. The top and bottom areas on an instrument approach chart that depict information about the procedure, including airport location and procedure identi-fication.

marker beacon. A low-powered transmitter that directs its signal upward in a small, fan-shaped pattern. Used along the flightpath when approaching an airport for landing, marker beacons indicate both aurally and visually when the aircraft is directly over the facility.

maximum altitude. An altitude depicted on an instrument approach chart with the altitude value overscored. Aircraft are required to maintain altitude at or below the depicted value.

maximum authorized altitude (MAA). A published altitude representing the maximum usable altitude or flight level for an airspace structure or route segment.

MB. See magnetic bearing.

MCA. See minimum crossing altitude.

MDA. See minimum descent altitude.

MEA. See minimum en route altitude.

MH. See magnetic heading.

microwave landing system (MLS). A precision instrument approach system operating in the microwave spectrum which normally consists of an azimuth station, elevation station, and precision distance measuring equipment.

mileage breakdown. A fix indicating a course change that appears on the chart as an “x” at a break between two seg-ments of a federal airway.

military operations area (MOA). MOAs consist of airspace established for the purpose of separating certain military training activities from IFR traffic.

Military Training Route (MTR). Airspace of defined vertical and lateral dimensions established for the conduct of military training at airspeeds in excess of 250 KIAS.

minimum altitude. An altitude depicted on an instrument approach chart with the altitude value underscored. Aircraft are required to maintain altitude at or above the depicted value.

minimum crossing altitude (MCA). The lowest altitude at certain fixes at which an aircraft must cross when proceeding in the direction of a higher MEA.

minimum descent altitude (MDA). The lowest altitude (in feet MSL) to which descent is authorized on final approach, or during circle-to-land maneuvering in execution of a nonprecision approach.

minimum en route altitude (MEA). The lowest published altitude between radio fixes which ensures acceptable navi-gational signal coverage and meets obstacle clearance requirements between those fixes.

minimum obstruction clearance altitude (MOCA). The lowest published altitude in effect between radio fixes on VOR airways, off-airway routes, or route segments which meets obstacle clearance requirements for the entire route segment and which ensures acceptable navigational signal coverage only within 25 statute (22 nautical) miles of a VOR.

minimum reception altitude (MRA). The lowest altitude at which an airway intersection can be determined.

minimum safe altitude (MSA). The minimum altitude depicted on approach charts which provides at least 1,000 feet of obstacle clearance for emergency use within a specified distance from the listed navigation facility.

minimum vectoring altitude (MVA). An IFR altitude lower than the minimum en route altitude (MEA) that provides terrain and obstacle clearance.

minimums section. The area on an IAP chart that displays the lowest altitude and visibility requirements for the approach.

missed approach. A maneuver conducted by a pilot when an instrument approach cannot be completed to a landing.

missed approach point (MAP). A point prescribed in each instrument approach at which a missed approach procedure shall be executed if the required visual reference has not been established.

mixed ice. A mixture of clear ice and rime ice.

MLS. See microwave landing system.

MM. Middle marker.

MOA. See military operations area.

MOCA. See minimum obstruction clearance altitude.

mode C. Altitude reporting transponder mode.

MRA. See minimum reception altitude.

MSA. See minimum safe altitude.

MTR. See Military Training Route.

MVA. See minimum vectoring altitude.

NACO. See National Aeronautical Charting Office.

NAS. See National Airspace System.

National Airspace System (NAS). The common network of U.S. airspace—air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, infor-mation and services; rules, regulations and procedures, technical information; and manpower and material.

National Aeronautical Charting Office (NACO). A Federal agency operating under the FAA, responsible for publishing charts such as the terminal procedures and en route charts.

National Route Program (NRP). A set of rules and proce-dures designed to increase the flexibility of user flight planning within published guidelines.

National Security Area (NSA). National Security Areas consist of airspace of defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. Pilots are requested to voluntarily avoid flying through the depicted NSA. When it is necessary to provide a greater level of security and safety, flight in NSAs may be temporarily prohibited. Regulatory prohibitions are disseminated via NOTAMs.

NM. Nautical mile.

NAV/COM. Combined communication and navigation radio.

NOAA. National Oceanic and Atmospheric Administration.

no-gyro approach.A radar approach that may be used in case of a malfunctioning gyro-compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions “turn right/left” or “stop turn,” as appropriate.

nonprecision approach. A standard instrument approach procedure in which only horizontal guidance is provided.

no procedure turn (NoPT). Used with the appropriate course and altitude to denote the procedure turn is not required.

NRP. See National Route Program.

NSA. See National Security Area.

NWS. National Weather Service.

OM. Outer marker.

omission error. Failing to anticipate significant instrument indications following attitude changes; for example, concen-trating on pitch control while forgetting about heading or roll information, resulting in erratic control of heading and bank.

optical illusion. A misleading visual image of features on the ground associated with landing, which causes a pilot to misread the spatial relationships between the aircraft and the runway.

orientation. Awareness of the position of the aircraft and of oneself in relation to a specific reference point.

overcontrolling. Using more movement in the control column than is necessary to achieve the desired pitch-and-bank condition.

overpower. Using more power than required for the purpose of achieving a faster rate of airspeed change.

P-static. See precipitation static.

PAPI. See precision approach path indicator.

PAR. See precision approach radar.

parasite drag. Drag caused by the friction of air moving over the aircraft structure; its amount varies directly with the air-speed. The higher the airspeed, the greater the parasite drag.

PIC. See pilot in command.

pilot in command (PIC). The pilot responsible for the opera-tion and safety of an aircraft.

pilot report (PIREP). Report of meteorological phenomena encountered by aircraft.

Pilot’s Operating Handbook/Airplane Flight Manual (POH/AFM). FAA-approved documents published by the airframe manufacturer that list the operating conditions for a particular model of aircraft.

PIREP. See pilot report.

pitot pressure. Ram air pressure used to measure airspeed.

pitot-static head. A combination pickup used to sample pitot pressure and static air pressure.

plan view. The overhead view of an approach procedure on an instrument approach chart. The plan view depicts the routes that guide the pilot from the en route segments to the IAF.

POH/AFM. See Pilot’s Operating Handbook/Airplane Flight Manual.

point in space approach. A type of helicopter instrument approach procedure to a missed approach point more than 2,600 feet from an associated helicopter landing area.

position error. Error in the indication of the altimeter, ASI, and VSI caused by the air at the static system entrance not being absolutely still.

position report. A report over a known location as trans-mitted by an aircraft to ATC.

precession. The characteristic of a gyroscope that causes an applied force to be felt, not at the point of application, but 90° from that point in the direction of rotation.

precipitation static (P-static). A form of radio interference caused by rain, snow, or dust particles hitting the antenna and inducing a small radio-frequency voltage into it.

precision approach. A standard instrument approach procedure in which both vertical and horizontal guidance is provided.

precision approach path indicator (PAPI). Similar to the VASI but consisting of one row of lights in two- or four-light systems. A pilot on the correct glide slope will see two white lights and two red lights. See VASI.

precision approach radar (PAR). A type of radar used at an airport to guide an aircraft through the final stages of landing, providing both horizontal and vertical guidance. The radar operator directs the pilot to change heading or adjust the descent rate to keep the aircraft on a path that allows it to touch down at the correct spot on the runway.

preferred IFR routes. Routes established in the major terminal and en route environments to increase system efficiency and capacity. IFR clearances are issued based on these routes, listed in the A/FD except when severe weather avoidance procedures or other factors dictate otherwise.

pressure altitude. Altitude above the standard 29.92" Hg plane.

prevailing visibility. The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle (which is not necessarily continuous).

primary and supporting. A method of attitude instrument flying using the instrument that provides the most direct indication of attitude and performance.

procedure turn. A maneuver prescribed when it is necessary to reverse direction to establish an aircraft on the intermediate approach segment or final approach course.

profile view. Side view of an IAP chart illustrating the vertical approach path altitudes, headings, distances, and fixes.

prohibited area. Designated airspace within which flight of aircraft is prohibited.

propeller/rotor modulation error. Certain propeller RPM settings or helicopter rotor speeds can cause the VOR course deviation indicator (CDI) to fluctuate as much as ±6°. Slight changes to the RPM setting will normally smooth out this roughness.

rabbit, the. High-intensity flasher system installed at many large airports. The flashers consist of a series of brilliant blue-white bursts of light flashing in sequence along the approach lights, giving the effect of a ball of light traveling towards the runway.

radar. Radio Detection And Ranging.

radar approach. The controller provides vectors while monitoring the progress of the flight with radar, guiding the pilot through the descent to the airport/heliport or to a specific runway.

radials. The courses oriented FROM the station.

radio or radar altimeter. An electronic altimeter that determines the height of an aircraft above the terrain by measuring the time needed for a pulse of radio-frequency energy to travel from the aircraft to the ground and return.

radio magnetic indicator (RMI). An electronic navigation instrument that combines a magnetic compass with an ADF or VOR. The card of the RMI acts as a gyro-stabilized mag-netic compass, and shows the magnetic heading the aircraft is flying.

radio wave. An electromagnetic wave (EM wave) with frequency characteristics useful for radio transmission.

RAIM. See receiver autonomous integrity monitoring.

random RNAV routes. Direct routes, based on area naviga-tion capability, between waypoints defined in terms of latitude/longitude coordinates, degree-distance fixes, or off-sets from established routes/airways at a specified distance and direction.

ranging signals. Transmitted from the GPS satellite, these allow the aircraft’s receiver to determine range (distance) from each satellite.

RB. See relative bearing.

RBI. See relative bearing indicator.

RCO. See remote communications outlet.

receiver autonomous integrity monitoring (RAIM). A system used to verify the usability of the received GPS signals and warns the pilot of any malfunction in the navigation system. This system is required for IFR-certified GPS units.

recommended altitude. An altitude depicted on an in-strument approach chart with the altitude value neither underscored nor overscored. The depicted value is an advisory value.

reference circle (also, distance circle). The circle depicted in the plan view of an IAP chart that typically has a 10 NM radius, within which the elements are drawn to scale.

regions of command. The “regions of normal and reversed command” refers to the relationship between speed and the power required to maintain or change that speed in flight.

REIL. See runway end identifier lights.

relative bearing (RB). The angular difference between the aircraft heading and the direction to the station, measured clockwise from the nose of the aircraft.

relative bearing indicator (RBI). Also known as the fixed-card ADF, zero is always indicated at the top of the instrument and the needle indicates the relative bearing to the station.

relative wind. Direction of the airflow produced by an object moving through the air. The relative wind for an airplane in flight flows in a direction parallel with and opposite to the direction of flight; therefore, the actual flightpath of the airplane determines the direction of the relative wind.

remote communications outlet (RCO). An unmanned communications facility remotely controlled by air traffic personnel.

restricted area. Airspace designated under 14 CFR part 73 within which the flight of aircraft, while not wholly pro-hibited, is subject to restriction.

reverse sensing. When the VOR needle appears to be indicating the reverse of normal operation.

RF. Radio frequency.

rigidity. The characteristic of a gyroscope that prevents its axis of rotation tilting as the Earth rotates.

rime ice. Rough, milky, opaque ice formed by the instan-taneous freezing of small supercooled water droplets.

RMI. See radio magnetic indicator.

RNAV. See area navigation.

runway end identifier lights (REIL). This system consists of a pair of synchronized flashing lights, located laterally on each side of the runway threshold, to provide rapid and posi-tive identification of the approach end of a runway.

runway visibility value (RVV). The visibility determined for a particular runway by a transmissometer.

runway visual range (RVR). The instrumentally-derived horizontal distance a pilot should be able to see down the runway from the approach end, based on either the sighting of high-intensity runway lights, or the visual contrast of other objects.

RVR. See runway visual range.

RVV. See runway visibility value.

SA. See selective availability.

St. Elmo’s Fire. A corona discharge which lights up the aircraft surface areas where maximum static discharge occurs.

satellite ephemeris data. Data broadcast by the GPS satellite containing very accurate orbital data for that satellite, atmospheric propagation data, and satellite clock error data.

scan. The first fundamental skill of instrument flight, also known as “cross-check”; the continuous and logical observa-tion of instruments for attitude and performance information.

SDF. See simplified directional facility.

selective availability (SA). A method by which the Department of Defense (DOD) can, in the interest of national security, create a significant clock and ephemeris error in the satellites, resulting in a navigation error.

sensitive altimeter. A form of multipointer pneumatic altimeter with an adjustable barometric scale that allows the reference pressure to be set to any desired level.

SIGMET. A weather advisory issued concerning weather significant to the safety of all aircraft.

signal-to-noise ratio. An indication of signal strength received compared to background noise, which is a measure of how adequate the received signal is.

simplex. Transmitting and receiving on the same frequency.

simplified directional facility (SDF). A NAVAID used for nonprecision instrument approaches. The final approach course is similar to that of an ILS localizer except that the SDF course may be offset from the runway, generally not more than 3°, and the course may be wider than the localizer, resulting in a lower degree of accuracy.

situational awareness. Knowing where you are in regard to location, air traffic control, weather, regulations, aircraft status, and other factors that may affect flight.

skidding turn. An uncoordinated turn in which the rate of turn is too great for the angle of bank, pulling the aircraft to the outside of the turn.

slant range. The horizontal distance from the aircraft antenna to the ground station, due to line-of-sight transmission of the DME signal.

slaved-compass. A system whereby the heading gyro “slaved to,” or continuously corrected to bring its direction readings into agreement with a remotely-located magnetic direction sensing device (usually a flux valve or flux gate compass).

slipping turn. An uncoordinated turn in which the aircraft is banked too much for the rate of turn, so the horizontal lift component is greater than the centrifugal force, pulling the aircraft toward the inside of the turn.

small airplane. An airplane of 12,500 pounds or less maximum certificated takeoff weight.

somatogravic illusion. The feeling of being in a nose-up or nose-down attitude, caused by a rapid acceleration or deceleration while in flight situations that lack visual reference.

spatial disorientation. The state of confusion due to mis-leading information being sent to the brain from various sensory organs, resulting in a lack of awareness of the aircraft position in relation to a specific reference point.

special use airspace. Airspace in which flight activities are subject to restrictions that can create limitations on the mixed use of airspace. Consists of prohibited, restricted, warning, military operations, and alert areas.

SSV. See standard service volume.

standard holding pattern. A holding pattern in which all turns are made to the right.

standard-rate turn. A turn in which an aircraft changes its direction at a rate of 3°per second (360°in 2 minutes) for low- or medium-speed aircraft. For high-speed aircraft, the standard-rate turn is 1-1/2° per second (360° in 4 minutes).

standard service volume (SSV). Defines the limits of the volume of airspace which the VOR serves.

standard terminal arrival route (STAR). A preplanned IFR ATC arrival procedure published for pilot use in graphic and/ or textual form.

STAR. See standard terminal arrival route.

static longitudinal stability. The aerodynamic pitching moments required to return the aircraft to the equilibrium angle of attack.

static pressure. Pressure of the air that is still, or not moving, measured perpendicular to the surface of the aircraft.

steep turns. In instrument flight, anything greater than standard rate; in visual flight, anything greater than a 45°bank.

stepdown fix. Permits additional descent within a segment of an IAP by identifying a point at which an obstacle has been safely overflown.

strapdown system. An INS in which the accelerometers and gyros are permanently “strapped down” or aligned with the three axes of the aircraft.

stress. The body’s response to demands placed upon it.

suction relief valve. A relief valve in an instrument vacuum system to maintain the correct low pressure inside the instru-ment case for the proper operation of the gyros.

synchro. A device used to transmit indications of angular movement or position from one location to another.

TAA. See terminal arrival area.

TACAN. See tactical air navigation.

tactical air navigation (TACAN). An electronic navigation system used by military aircraft, providing both distance and direction information.

TDZE. See touch down zone elevation.

TEC. See Tower En route Control.

technique. The manner or style in which the procedures are executed.

temporary flight restriction (TFR). Restrictions to flight imposed in order to:

Protect persons and property in the air or on the surface from an existing or imminent flight associated hazard;
Provide a safe environment for the operation of disaster relief aircraft;
Prevent an unsafe congestion of sightseeing aircraft above an incident;
Protect the President, Vice President, or other public figures; and,
Provide a safe environment for space agency operations.

Pilots are expected to check appropriate NOTAMs during flight planning when conducting flight in an area where a temporary flight restriction is in effect.

tension. Maintaining an excessively strong grip on the control column; usually results in an overcontrolled situation.

terminal arrival area (TAA). The objective of the TAA procedure design is to provide a new transition method for arriving aircraft equipped with FMS and/or GPS navigational equipment. The TAA contains a “T” structure that normally provides a NoPT for aircraft using the approach.

TFR. See temporary flight restriction.

thrust(aerodynamic force). The forward aerodynamic force produced by a propeller, fan, or turbojet engine as it forces a mass of air to the rear, behind the aircraft.

time and speed table. A table depicted on an instrument approach procedure chart that identifies the distance from the FAF to the MAP, and provides the time required to transit that distance based on various groundspeeds.

timed turn. A turn in which the clock and the turn coordinator are used to change heading a definite number of degrees in a given time.

Title 14 of the Code of Federal Regulations (14 CFR). The federal aviation regulations governing the operation of air-craft, airways, and airmen.

touchdown zone elevation (TDZE). The highest elevation in the first 3,000 feet of the landing surface, TDZE is indicated on the instrument approach procedure chart when straight-in landing minimums are authorized.

Tower En route Control (TEC). The control of IFR en route traffic within delegated airspace between two or more adja-cent approach control facilities, designed to expedite traffic and reduce control and pilot communication requirements.

TPP. See U.S. Terminal Procedures Publication.

tracking. Flying a heading that will maintain the desired track to or from the station regardless of crosswind conditions.

Transcribed Weather Broadcast (TWEB). Meteorological and aeronautical data is recorded on tapes and broadcast over selected NAVAIDs. Generally, the broadcast contains route-oriented data with specially prepared NWS forecasts, in-flight advisories, and winds aloft; plus selected current information such as weather reports (METAR/SPECI), NOTAMs, and special notices.

transponder. The airborne portion of the ATC radar beacon system.

transponder code. One of 4,096 four-digit discrete codes ATC will assign to distinguish between aircraft.

trend. Instruments showing an immediate indication of the direction of aircraft movement.

trim. Adjusting the aerodynamic forces on the control sur-faces so that the aircraft maintains the set attitude without any control input.

TWEB. See Transcribed Weather Broadcast.

uncaging. Unlocking the gimbals of a gyroscopic instrument, making it susceptible to damage by abrupt flight maneuvers or rough handling.

underpower. Using less power than required for the purpose of achieving a faster rate of airspeed change.

U.S. Terminal Procedures Publication (TPP). Booklets published in regional format by the NACO that include DPs, STARs, IAPs, and other information pertinent to IFR flight.

unusual attitude. An unintentional, unanticipated, or extreme aircraft attitude.

user-defined waypoints. Waypoint location and other data which may be input by the user; this is the only GPS database that may be altered (edited) by the user.

variation. The compass error caused by the difference in the physical locations of the magnetic north pole and the geo-graphic north pole.

VASI. See visual approach slope indicator.

VDP. See visual descent point.

vectoring. Navigational guidance by assigning headings.

venturi tube. A specially-shaped tube attached to the outside of an aircraft to produce suction to operate gyro instruments.

very-high frequency omnidirectional range (VOR).

Electronic navigation equipment in which the cockpit instrument identifies the radial or line from the VOR station measured in degrees clockwise from magnetic north, along which the aircraft is located.

vestibular. The central cavity of the bony labyrinth of the ear, or the parts of the membranous labyrinth that it contains.

VFR. See visual flight rules.

VFR-On-Top. ATC authorization for an IFR aircraft to operate in VFR conditions at any appropriate VFR altitude.

VFR Over-The-Top. A VFR operation in which an aircraft operates in VFR conditions on top of an undercast.

Victor airways. Based on a centerline that extends from one VOR or VORTAC navigation aid or intersection, to another navigation aid (or through several navigation aids or intersec-tions); used to establish a known route for en route procedures between terminal areas.

visual approach slope indicator (VASI). A system of lights arranged to provide visual descent guidance information during the approach to the runway. A pilot on the correct glide slope will see red lights over white lights.

visual descent point (VDP). A defined point on the final approach course of a nonprecision straight-in approach procedure from which normal descent from the MDA to the runway touchdown point may be commenced, provided the runway environment is clearly visible to the pilot.

visual flight rules (VFR). Flight rules adopted by the FAA governing aircraft flight using visual references. VFR opera-tions specify the amount of ceiling and the visibility the pilot must have in order to operate according to these rules. When the weather conditions are such that the pilot can not operate according to VFR, he or she must use instrument flight rules (IFR).

visual meteorological conditions (VMC). Meteorological conditions expressed in terms of visibility, distance from cloud, and ceiling meeting or exceeding the minimums speci-fied for VFR.

VMC. See visual meteorological conditions.

VOR. See very-high frequency omnidirectional range.

VORTAC.A facility consisting of two components, VOR and TACAN, which provides three individual services: VOR azimuth, TACAN azimuth, and TACAN distance (DME) at one site.

VOR test facility (VOT). A ground facility which emits a test signal to check VOR receiver accuracy. Some VOTs are available to the user while airborne, while others are limited to ground use only.

WAAS. See wide area augmentation system.

warning area. An area containing hazards to any aircraft not participating in the activities being conducted in the area. Warning areas may contain intensive military training, gunnery exercises, or special weapons testing.

waypoint. A designated geographical location used for route definition or progress-reporting purposes and is defined in terms of latitude/longitude coordinates.

WCA. See wind correction angle.

wide area augmentation system (WAAS). A differential global positioning system(DGPS) that improves the accuracy of the system by determining position error from the GPS satellites, then transmitting the error, or corrective factors, to the airborne GPS receiver.

wind correction angle (WCA). The angle between the desired track and the heading of the aircraft necessary to keep the aircraft tracking over the desired track.

work. A physical measurement of force used to produce movement.