# t3 w
U.S. Department ofTransportation Fedemi Aviation Administration 

# Advisory

Circular

Subject: ELECTRICAL FAULT AND

### FIRE Date: 4/5/91 ACNo: 

### 25-16

PREVENTION ANDPROTECTION Initiated by: ANM-

### 100 Change:



### 1 PURPOSE. This advisory circular (AC) provides information on electrically caused faults, overheat, smoke, and fire in transport category airplanes. Acceptable means are provided to minimize the potential for these conditions to occur, and to minimize or contain their effects when they do occur. These means are not mandatory. An applicant may elect to use any other means found to be acceptable by the Federal Aviation Administration for compliance with the Federal Aviation Regulations (FAR).

2 RELATED FARSECTIONS. The related sections of the FARare as follows. Where applicable, corresponding sections of Part 4b of the Civil Air Regulations (CAR) of 

### 1962follow each cited Part 25 section of the FAR. 

### 21.21(b)(l) 25.1309(a)/4b.606(a) 21.21(b)(2) 25.1309(b) 

### 25.601/4b.300 25.1309(c)/4b.606(b) 

### 25.603/4b.301 25.1309(d) 

### 25.671/4b.320(a) 25.1333/4b.612(f) 25.695 (Initia1)/4b.320(b) 25.135l(b)(2)/4b.622(b)(2) 25.672 (Amdt. 25-23 or later amdt.)/4b.320(b) 25.1353 

### 25.831(c)/4b.371(c) 25.1357(a)/4b.624(a) 

### 25.853/4b.381 25.1359(d) 

### 25.863/4b.385 25.1363/4b. 

### 627 25.901/4b.400 25.1435/4b.654 and 4b.655 25.903/4b.401 25.1529 25.1307(c)/4b.602 and 4b.605(e) 25.158l(a)(2)/4b.740(c).

3 RELATEDADVISORY CIRCULARS. The guidance in this ACsupplements the following existing guidance on safe electrical design and installation practices.

a. AC43.13.lA, Change 3, Acceptable Methods, Techniques, and Practices, Aircraft Inspection and Repair.

b. AC43.13.2A, Change 

### 1, Acceptable Methods, Techniques, and Practices, Aircraft Alterations.

c. AC25-9, Smoke Detection, Penetration, Evacuation Tests, and Related Flight Manual Emergency Procedures.

d. AC25-10, Guidance for 

### Installation of Miscellaneous, Non-required Electrical Equipment.AC

### 25-16 04/05/91

4

. DEFINITIONS.

a. Electrical Component: For the purpose of this AC, an electrical component is defined as an electrical power source, or a component receiving electricity from any source. Sources of electricity are not limited to power sources or distribution buses. They also include signal sources, such as the output of an autopilot servo amplifier, or data sources that transfer information electrically from one component to another.

b. Circuit Protective Device (CPD): Adevice used to protect electrical/electronic circuit components from an over-voltage or over-current condition, by automatically interrupting the current flow. The most common types of CPDs used in aircraft are the circuit breaker and the fuse.

c. Aromatic Polyimide Insulation: Awire insulating material formed as the result of a polycondensation reaction between an aromatic dianhydride and an aromatic diamine.

d. Arc: Aphenomenon in which a conductive carbon path is formed across an insulating surface. This carbon path provides a short circuit path through which current can flow. Normally a result of electrical arcing. Also referred to as "Carbon Arc Tracking," 'Wet Arc Tracking," or "Dry Arc Tracking."

e. Insulation Flashover: Aresult of Arc Tracking, an instantaneous burn-through of the insulated wire with the possibility of continuing the burn into surrounding wires. This failure mode, which is a result of the high temperature degradation of the insulation experienced during arcing, can propagate through acomplete wire bundle severing the entire grouping.


### 5

. WIRINGFAULT ANDWIRE

### INSULATIONFLAMMABILITYINFORMATION.

a. Backsround. Amendment 25-32, effective May 1, 1972, added a new 3

### 25.1359(d) which applies the flammability requirements 

### of Appendix Fof Part 25 to wire insulation used in aircraft and also revised Appendix Fto make the burn test requirements more stringent. These requirements are effective on airplanes for which application for atype certificate is (or was) made on or after May 

### 1, 1972; on the Boeing 747, Douglas 

### DC-lo, and Lockheed 

### L-1011 airplanes by special conditions; and on certain other airplanes. (Reference the Type Certificate Data Sheet of each airplane type for its type certification basis.) Before these regulatory actions, there were no wire insulation flammability requirements in either Part 25 or Part 4b. Certain types of insulation, including polyvinyl chloride (PVC) insulation, do not comply with the 5

### 25.1359(d) flammability requirements.

requirements are referred -to as "later" airplanes, and a referred to as "earlier" airplanes. Similarly, wire hav b. Discussion. Airplanes subject to the 5

### 25.1359(d) flammability airplanes are lation which li other ing insu



### 2 Par 4

### 04/05/91 AC

### 25-16

complies with these flammability requirements is referred to as 'later" wire, and all other wire is referred to as "earlier" wire.

c. General Guidance. The guidance in this ACsupplements existing guidance provided in AC43.13-1A and AC43.1302A, and should be applied to new airplanes, as well as to modifications of previously-certificated airplanes in all locations where electrical systems, components, or wires are affected. It may also be useful in developing corrective Airworthiness Directive (AD) actions taken in response to hazards discovered in service. 

### It should be noted that this guidance is not intended to take the place of instructions or precautions provided by wire, wire insulation, or equipment manufacturers. Also, if any requirement of Part 25 that is included in the airplane's type certification basis supersedes any particular guidance in this AC, compliance with that requirement of Part 25 should be ensured. This guidance reflects past certification practices and is considered to provide acceptable means of compliance with, or equivalent safety to, $5 

### 25.1359(d) and 25.831.



### (1) Earlier wire may be used in all locations in earlier airplanes. (2) Earlier wire may be used inside the fuselage of later airplanes only if its use does not create any significant potential for hazard. Under the equivalent safety provision of 

### 521.21(b)(l), the potential for hazard is considered insignificant if the guidance provided in any of the following three paragraphs is followed:

(i) Earlier wire may be used inside equipment designed, on an overall basis, to be as fire-resistant as practicable if it is either:
(A) Enclosed in acase made of metal or other material that complies with the flammability requirements of Amendment 25-32 that will either contain an internal fire so that it cannot propagate to other locations or is sufficiently airtight that internal ignition sources cannot cause a fire; or (B) Located and installed where a fire cannot damage safety-related parts, propagate to flammable parts, or cause personal injury. Maximum physical or spatial separation is especially important above the equipment or downstream of any consistent, known airflow.

(ii) Earlier wire may be used inside the cases of video or audio tape players, television receivers, telephones, or other passenger convenience or entertainment equipment purchased on the general commercial market where similar, economically-feasible equipment having wire which complies with 5 25.1359(d) does not exist. 

### In such instances, the equipment should be located where smoke or fire would readily be noticed, and a readily identifiable switch, located away from the equipment, should be provided to enable its safe and rapid disconnection.

Par 5AC25- I.6 

### 04/05/91
(iii) Where reasonable and appropriate, very small amounts of earlier, special-purpose wire, such as telephone interconnection wires, may also be used outside equipment cases.
d. General Wire Installation Guidance. (1) All instructions and precautions provided by wire and wire insulation manufacturers should be followed and observed.

(2) Machines used to stamp identification on wire insulation should be adjusted so as not to penetrate through the insulation. Quality assurance procedures to verify that penetration has not occurred should be established. An acceptable method would be to employ an approved high voltage test. Alternatively, a non-impact process to place identification on wire insulation may be used.

(3) Care should be taken to ensure that the clamps and ties around wire bundles do not present a rough surface that may damage the wire insulation. These clamps and ties should be tight enough to hold the wires in place, but not so tight that insulation damage would occur during fabrication
or installation, or later in service. To prevent insulation chafing, wires and bundles should be installed by routing and clamping to ensure sufficient spacing from structure or other parts after any single failure. Alternatively, other means may be used to prevent insulation chafing after any single failure. Some examples of such single failures would include the failure of any single clamp or clamp fastener. To prevent insulation damage during installation or maintenance, avoid routing wires or bundles in the vicinity of parts having sharp edges, corners, or protrusions. Alternatively, sharp edges, corners, or protrusions should be covered with smooth protective material or other devices. Bend radii should be large enough to ensure that insulation cracking does not occur during the fabrication or installation of wires or bundles, or later in service due to excessive mechanical stress. The clamps should be oriented such that abrasion of the wire or the clamp insulation does not occur. The clamps should be acompression type and should be spaced so that, assuming awire break, the broken wire will not contact hydraulic lines, oxygen lines, pneumatic lines, or other equipment whose subsequent failure caused by arcing could cause further damage. Quality assurance procedures should be established to verify that insulation damage has not occurred during the process of fabricating and installing wires and bundles. (4) Abrasion of wire insulation caused by differences in hardness can be hazardous. Therefore, wires having significantly different insulation hardness, or abrasion characteristics, should be routed in separate bundles. This is particularly important in areas of high vibration. Abrasion of either the insulation or the insulation-facing material of the clamps, conduits, or other devices used to secure or support wires or bundles can also be hazardous. Therefore, wire and bundle installations should be designed so that the insulation-facing material has ahardness compatible with that of the

4 Par 5

### 04/05/91 AC25-16

insulation. Compatible materials areoften knownbythewire orwire insulation manufacturer ortheairplane manufacturer ormodifier. Compatible materials mayalso havebeenestablished byprior satisfactory service experience ortests. However, if suchinformation is unavailable, insulation andinsulation-facing materials should betested to ensurethat differences in hardnesswould not result in abrasion i-nservice.

(5) Toprevent insulation damage,wires orwire bundles should not berouted in locations whereliquid spillage or leakage maybeanticipated in service. It should beassumedthat water orother liquids fromanysource are electrolytic. This assumption applies whether the liquids are pureor have other chemical(s) dissolved inormixedwith them. Service experience shows that locating wires or bundles underlavatories andgalleys hassometimes resulted in insulation damage. Locating themin thewheelwells andsome areasof thewings hasalso resulted indamage. Locating themin someareas of the empennagecould also result indamage. Careshould betaken to ensure that condensation, rain, snow,hail, ice, orslush will not result in insulation damageordeterioration ofwires or bundles exposedtothese environments. This maybeestablished bysatisfactory service experience, tests, orcomparison of the insulation chemistry anddesign with those of other types of insulation that areknownto besafewhenexposedto these environments. In particular, the useof aromatic polyimide insulation material inthese areas should becarefully evaluated.

(6) Installations that are inherently difficult sometimes lead to post-maintenance reinstallations that donot conform to anyapprovedtype design. Service experience showsthat suchnon-conforming reinstallations, especially if donehurriedly, cansignificantly increase the potential for electrical faults, smoke,orfires. Therefore, to the greatest practicable extent, atype design should beprovided for wire andwire bundle installations that allows for easyreinstallation after the completion of maintenance.

(7) Wires andwire bundles should berouted orotherwise protected tominimize the potential for maintenance personnel to step, walk, orclimb on them, orusethemfor handholds. Thewire bundles should berouted along heavier structural memberswheneverpossible. Sharpmetal edgesmustbe protected bygrommetsto prevent chafing. Wires should not berouted between aircraft skin andfuel lines. Avoid running wires along the bottom of the fuselage, over the landing gear, in areasofthe leading edgeofthewing wherefuel spillage is anticipated, oradjacent to flammable fluid lines or tanks. (8) In installations wherewires orwire bundles areexpected to flex, suchaslanding gear harnesses, aromatic polyimide insulated wires should beavoided. If this wire type is usedin flexible conduit, then the conduit installation should beproperly designed for this purpose.

Par 5AC25-16 

### 04/05/91

6

. CIRCUITPROTECTIVEDEVICE(CPD)INFORMATION.

a. Background. Historically, the FAAcriterion for circuit protective device (e.g., 

### circrit breaker orfuse) selection cansimply beexpressed as, "to protect the aircraft wiring, but notthe equipment." This limited criterion is basedondesigning electrical componentsto beasfire-resistant
as 

### practicable andeither enclosing themin metal casesthat will contain an internal 

### fire oraresufficiently airtight that internal ignition sources cannot 

### causeafire, or isolating themfromflammable materials and safety-related parts. Inthevast majority of instances metal caseshavebeen used. 

### Thefewexceptions which are knownto haveresulted' in orcontributed to 

### fires havebeencorrected byairworthiness directive (AD)action. However, protecting electrical system 

### installations byusing CPDsto protect wiring and through 

### componentdesign to protect the rest of the system is not adequate. Circuit protective devices (circuit breakers andfuses) areconsidered to be slow-acting devices andmaynot offer sufficient disconnect protection from events suchasarc-tracking or insulation flashover. Forexample, service experience 

### showsthat:

(1) Selection of CPDratings; protection of three-phase loads; design 

### ofconnectors, wire bundles, routing andclamping; andcomponent temperatures have not always been safe.



### (2) Faulty maintenance sometimes 

### occurs in regard to routing, clamping, 

### andcleanliness of locations surrounding certain equipment.

(3) Aging, weathering, vibration, andthe normalwearandtear of maintenance 

### sometimes causechafing, abrasion, ordeterioration of insulation, which 

### canresult in cracks orcuts that exposethe conductor.

(4) The effects 

### ofelectrical faults caninclude component overheating; toxic fumes; smoke; 

### fire; damagetowires, wire bundles, or parts; 

### melting of holes in sheet metal parts byfaulted, high-current feeder cables; 

### melting andburning oftitanium bleed air ducts byachafed, highcurrent feeder cable; electromagnetic 

### interference (EMI)with equipment; and the 

### simultaneous andunrestorable loss of both engine-driven generators in a two-engine 

### airplane. While these effects occur infrequently, guidance is considered 

### necessary to minimize themwhenthey dooccur andto minimize their potential causes. These effects can 

### becausedbythe following conditions or failure 

### modesfor which CPD'soften donot provide timely, if any, automatic protection: (i) Intermittent, 

### low impedance 

### short-circuits, suchaschafing
or arcing of wires on grounded metal 

### parts, orchafing betweenconductors of different 

### phases.

(ii) Higher impedance 

### short-circuits which, for example, canbe caused by locating wire in amoist 

### orwetenvironment if thewire insulation is cracked or cut.



### Par6

### 04/05/91 AC250 16 (iii) Low or higher impedance short-circuits inside electrical components themselves; or in component power, signal, or data transfer interconnection wires.

(iv) Failure of power to one or two phases of components intended for three-phase power.

(v) Incorrect assumptions of worst-case load conditions in regard to safe component temperatures.

(vi) Inadequate design bundle temperatures.

(vii) High-current cab (viii) Arcing on wire damage. Service experience documents in regard to safe connector' or wire

e faults.
nsulation, or the resulting insulation only a relatively small number of incidents of arcing damage for all types of insulation. However, service experience of aromatic polyimide insulation, as presently constructed, documents a failure mode called "insulation flashover" where conduction at insulation breakdown areas has damaged or destroyed the wire or wire bundle in which it occurs. Also, other adverse effects have sometimes occurred as a result of this failure mode. Arcing on wire insulation, or "arc tracking," can result from electrolytic contamination of wire having insulation cracks or cuts that expose the conductor. 

### It can also result from chafing damage that reduces the dielectric strength of dry insulation. Each successive attempt to restore an automatically-disconnected power source, or the resetting of an automatically-disconnected CPD, can result in progressively worse effects from "arc tracking."

b. Circuit Protective Device Selection And Related Guidance. 

### (1) Linear corrections should be made of any measured temperatures to the maximum sea level outside ambient temperature approved for operations in the Limitations Section of the FAA-approved airplane flight manual (AFM) or AFMrevision or supplement. Alternatively, they may be corrected in accordance with an analysis that establishes a rational method of correction.

(2) Quality assurance (QA) procedures should be established to ensure that circuit breaker time-versus-c conform to their specifications, whenever Such procedures should be followed before rrent automatic trip characteristics a specific type or iot is suspect. installing circuit breakers. 

### (3) To protect against unsafe w should be given to the wire size and spec deliverable continuous current of the CPDi i

lre temperatures, consideration fication used at the maximum

disconnection specification for each CPDshou into account its ambient temperature and that he time-versus-current automatic Id also be considered, taking of the protected wire. If doubt

Par 6 

### 7AC25-16 

### 04/05/91

exists regarding safe wire insulation temperatures, measurements should be taken and corrected as described in paragraph 

### 6b(l).

(4) To minimize deliverable power to potential fault loads, the minimum commercially-available CPDrating should be used. This is the rating that will power the normal (intended) load without spurious automatic disconnections due to temporary conditions such as transients, surges, or momentary overloads,

NOTE: 

### It is recommended that thermal circuit breakers not be specified for a continuous load in excess of 85 percent of the circuit breaker rating because it may cause deterioration of the trip point. (5) To protect against propagation of an internal electrical component fire to surrounding locations, electrical components should be designed using non-flammable or self-extinguishing materials to minimize the potential for fire. Electrical components should be enclosed in metal or other fire-resistant cases (reference paragraph 5c(2)(i)(A)) that will either contain an internal fire or are sufficiently airtight that internal ignition sources cannot cause a fire. However, if such acase is impracticable, the component should be located and installed where a fire cannot damage safety-related parts, propagate to flammable parts, or cause personal injury (reference paragraph 5c(2)(i)(B)). Maximum physical or spatial separation is especially important above the component, or downstream of any consistent, known airflow.

(6) Precautions should be taken to ensure that three-phase loads are not a smoke or fire hazard and do not result in unsafe component temperatures when powered by fewer than three phases. Note that three-phase, integral (ganged) circuit breakers seldom detect the loss of phases when an overcurrent condition does not exist. 

### If component overheating could occur, separate thermal protection should be provided in the equipment case. This could occur, for example, as a result of a bus phase outage, a load control component failure, or an open wire. 

### If doubt exists regarding safe component temperatures, measurements should be taken and corrected as described in paragraph 6b(

### 1). The recommended maximum safe external temperatures are considered to be: 450°F for components in dry, clean, and isolated locations; 400°F for components located in the vicinity of safety-related or flammable parts (including liquids or gases), or where flammable waste or other foreign material (such as used paper towels) might inadvertently accumulate without readily being noticed; and 140°F for components in occupied locations.

(7) Some internally-faulted components may not cause automatic disconnection of their CPD's before causing excessive temperatures that would result in a serious personnel, smoke, toxic fumes, or fire hazard. Some examples would include certain transformers and motors. In such cases, adequate backup protection should be provided. If over-temperature protection systems are used, the disconnection of the components protected by these

8 Par 6

### 04/05/91 AC25-16



### systems should beconsidered whendetermining compliance with the applicable 

### regulations. This is especially important for components in morethan one channel ofaredundant system, orcomponentsinvarious systemsthat perform 

### operationally-similar functions. Consideration should also begiven to foreseeable operational andlocal environmental conditions, andthe failure of 

### anynecessary cooling air supply.

(8) Protection should beprovided against unsafe temperatures in 

### connectors andwire bundles. Consideration should begiven to probable 

### combinations anddurations ofthe maximumnormal (intended) loads, combined 

### with the simultaneous maximumsingle continuous fault load for that individual 

### wire whichwouldcausethe maximumincrease in connector or bundle temperature 

### (reference paragraph 6b(3)). Themaximumsafe temperature should be determined fromthe specifications ofthe connector orthewires with the lowest temperature rating. Themaximumsafe temperature should not be exceeded, except in unavoidable applications with high ambient temperatures 

### (e.g., the powerplant). If doubt exists regarding safe connector or bundle 

### temperatures, measurementsshould betaken andcorrected asdescribed in paragraph 6b(1).
70 MISCELLANEOUS DESIGN, OPERATIONAL. ANDMAINTENANCE-RELATED GUIDANCE.



### a. Careshould betakento ensurethat EM1causedbyintermittent 

### faults doesnot adversely affect systemsorequipment. Suchintermittent 

### faults canbecaused, for example, 

### bychafing ofconductors ongrounded metal 

### parts, chafing betweenconductors ofdifferent phases, orarcing onwire insulation. Digital equipment, including digital computer-based equipment, is 

### usually moresusceptible to suchEM1thanother equipment.
b. It is accepted practice todemonstrate bytests that the generator 

### protection system 

### responds properly to faults in the electrical generation and 

### distribution system, or in anyutilization system. Demonstrations of arcing 

### onwire insulation should beallowed to progress to the point of "insulation 

### flashover." Thetests maybesupported byanyrelevant analysis. If laboratory tests are conducted instead of airplane tests, compliance should be 

### shownwith 525.1363.

c. 

### Penetration of the effects ofelectrical faults orfailure modes 

### into tanks, tubes, orcomponentscontaining fuel, other flammable fluid, 

### oxygen, orconcentrated oxidizing or reducing agents (such aschemical oxygen generators) canbeextremely hazardous. Therefore, it is important to ensure 

### that anyforeseeable penetration will not occur. Someexamplesof foreseeable 

### faults orfailure modesthat could result in penetration would include short-circuits of conductors, arcing onwires orwire bundles, or "insulation 

### flashover." Consideration should begiven tothe maximumpowerwhich could be 

### produced bysuchfaults orfailure modes,andthe physical orspatial separation provided betweentheir possible locations andthe areasof potential hazard, Additionally, physical orspatial separation should be provided betweenhigh-current cables andtheareasof potential hazard. However, if adequateseparation is impracticable, protection should be
Par6AC25-16 

### 04/05/91

provided against the effects of foreseeable faults or failure modes by providing alternative physical protection such as an adequate barrier or conduit, or by other acceptable means. For example, adequate separation is impracticable for wires or bundles that are necessarily located inside of or close to fuel tanks, and may be impracticable for some wires or bundles located in nacelles or pylons. Whenever practical, aromatic polyimide insulation wires should not be used for high current carrying cables.

d. Electrical components should be assessed for potential fire or smoke (which includes harmful or hazardous concentrations of gasses or vapors) assuming a failure has occurred. Typically, circuit protective devices and metal enclosures are all that are used to control the failure conditions, but not in every case (example - overheat protective devices). Each installation must be evaluated on its own merits. Electrical equipment bays should contain smoke and overheat detectors, and methods should be devised to contain a fire and prevent smoke from penetrating into the cabin or the cockpit. Smoke detection tests, smoke penetration tests, and smoke evacuation tests should be conducted in flight to demonstrate that the methods to detect, control, and evacuate the smoke are functioning as designed. The tests should be conducted in accordance with the test procedures outlined in AC25-9.

e. Electrical components located in fuel vapor zones should be qualified as explosion proof in accordance with Section 9of RTCADocument DO160B, "Environmental Conditions and Test Procedures for Airborne Equipment," dated July 20, 

### 1984, or later approved revision. Fuel vapor zones are defined by the airplane manufacturer.

f. Burning of ametal part can be extremely hazardous; therefore, it is important to ensure that any foreseeable burning will not occur. Some parts made of certain metals, such as magnesium or titanium, can sometimes ignite and burn before they melt and drip away. Ignition can be caused by electrical faults or failure modes. Whether such a part will burn before it melts depends on various factors. Some examples of such factors would include mass; electrical and thermal conductivity; design, construction, and installation; rate of heat dissipation into surrounding locations; smaller dimensions (e.g., metal thickness); presence of sharp or thin edges, corners, or protrusions (e.g., cooling fins); air temperature; airflow; and oxygen content. If the use of such apart otherwise complies with @ 25.601 and 25.603, consideration should be given to the maximum power which could be produced by foreseeable faults or failure modes and the physical or spatial separation provided between their possible locations and the part. Some examples of such faults or failure modes would include short-circuits of conductors, arcing on wires or wire bundles, or "insulation flashover." Routing high-current cables in the vicinity of such parts should be avoided; however, if adequate separation is impracticable, protection should be provided against the effects of foreseeable faults or failure modes by the use of alternative physical protection, such as an adequate barrier or conduit, or by other acceptable means. For example, adequate separation may be impracticable for some wires or bundles located in nacelles or pylons.

10 Par 7

### 04/05/91 AC250 16

g 

### Information should be provided in FAA-approved AFM's or AFM revisions or supplements that the crew should make onlv one attempt to restore an automatically-disconnected power source or reset or replace an automatically-disconnected CPDthat affects flight operations or safety.

h. Some electrical faults or failure modes can result in the automatic disconnection of apower source, bus, or high-current load for which power cannot be restored (or will not remain restored) without maintenance action. Such adisconnection could result in aserious latent failure of a flight control system component if the fault or failure mode occurs in its vicinity. For this reason, it is important that maintenance personnel determine by close inspection of related and non-related components in the vicinity of the fault, and before the next flight, that such a latent failure has not occurred. Therefore, this maintenance information should be provided to owners and operators of the airplane early enough for well-planned, timely incorporation into FAA-approved maintenance programs. 

# *&IyJyg<2$

Manager; Transport Airplane Directorate Aircraft Certification Service, 

### ANM-100

W.S.Government Printingoffice: 1991- 522-242/40101

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### 11U.S.

Department ofTransportation Federul aviation Administration

800 Independence Ave., S.W. Washington, D.C.20591

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