Report On A320 Decompression Faults Maintenance Personnel's

SEPTEMBER–OCTOBER 2002

F L I G H T S A F E T Y F O U N D A T I O N

Aviation Mechanics Bulletin

Report on A320Decompression Faults

Maintenance Personnel’sWork on Air Packs

F L I G H T S A F E T Y F O U N D A T I O N

Aviation Mechanics BulletinDedicated to the aviation mechanic whose knowledge,craftsmanship and integrity form the core of air safety.

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Report on A320 Decompression Faults MaintenancePersonnel’s Work on Air Packs .....................................................................1

Maintenance Alerts ........................................................................................8

News & Tips ............................................................................................... 16

September–October 2002 Vol. 50 No. 5

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Report on A320Decompression Faults

Maintenance Personnel’sWork on Air Packs

The report by the U.K. Air Accidents Investigation Branchsaid that trouble-shooting failed to detect damage to an air-conditioning pack and that maintenance personnel used an

unapproved technique to reattach a disconnected duct.

FSF Editorial Staff

About 1333 local time June 10,2000, the crew of an Airbus A320 ex-perienced a rapid decompression asthe airplane was flown throughFlight Level (FL) 300 (approximate-ly 30,000 feet) following departurefrom London Gatwick Airport enroute to Palma de Mallorca, Spain.The crew donned oxygen masks,conducted an emergency descent andlanded the airplane at the departureairport. The airplane received minordamage; none of the 182 people inthe airplane was injured seriously,

but a number of passengers said thatthey experienced symptoms typical-ly associated with hyperventilationor anxiety.1

In its report, the U.K. Air AccidentsInvestigation Branch (AAIB) saidthat the incident — the second de-compression incident involving theairplane that day — had occurred oneday after problems involving the air-plane’s no. 2 (right) air-conditioningpack were “inappropriately addressedby maintenance.”

2 FLIGHT SAFETY FOUNDATION • AVIATION MECHANICS BULLETIN • SEPTEMBER–OCTOBER 2002

In A320s, high-pressure air from eachengine is ducted to an air-conditioningpack, where the pressure, temperatureand humidity are adjusted. The packsare located outside the pressure hullin a compartment that is protectedagainst overpressure by a “blow-outpanel.” Conditioned air flows fromeach air-conditioning pack, througha section of flexible ducting/bellowsand a non-return valve (NRV) andinto the pressure hull.

The report said that the bellows “con-nects the pack condenser outlet to arigid duct, which leads to the NRV at[the] entry to the pressure hull.” TheNRV, which is designed to maintaincabin pressure in the event of a fail-ure of one air-conditioning pack, is aflap held in the closed position by aspring. The flexible bellows is se-cured by a V-band clamp at its for-ward end, where a metal rim meetsthe clamp; at the aft end, the final sec-tion of the flexible bellows slides overthe condenser outlet duct and is se-cured by a metal flat-band clamp.

Maintenance records showed thatnearly two years before the incident,in July 1998, repairs were performedon the no. 1 pack flexible duct. Thenotation in the maintenance recordsdid not describe the nature of the re-pairs but reported that the ducting“appeared to hold OK.” Four dayslater, however, the flexible duct wasreplaced. In September 1998, the no.2 air-conditioning pack outflow duct

was replaced. Several subsequentnotations in the maintenance recordsinvolved the no 2 air-conditioningpack, but none mentioned the flexi-ble duct.

The air-conditioning packs had un-dergone maintenance several times inthe days preceding the incident.(Maintenance was conducted by acompany under contract with the air-line; the report did not name the air-line or the maintenance company.) Anoverheating problem was reported onthe no. 2 pack on June 6; a built-intest equipment check and a groundrun detected no anomalies. On June7, the no. 2 pack condenser was re-placed because of a cracked flange;the replacement work involved dis-connecting and reconnecting the flex-ible duct at the condenser outlet.

“The engineer who carried out thiswork while the aircraft was on athree-hour ‘turn-round’ found that theduct was held on the condenser out-let by a nylon tie-wrap, and he re-placed ‘like with like,’” the reportsaid. “Though he had some doubtsabout whether this was the correctattachment method, he became in-volved with handing over to the nextshift after he had completed the job,and he did not pursue the matter orraise a ‘deferred defect’ to have it re-placed or monitored.

“In flight, following the condenser re-placement, a low-frequency vibration

FLIGHT SAFETY FOUNDATION • AVIATION MECHANICS BULLETIN • SEPTEMBER–OCTOBER 2002 3

was reported during the climb, and theno. 2 pack overheated several times inthe cruise. After flight, the (nonpres-surized) air-conditioning pack com-partment overpressure (blow-out)panel was found open. The no. 2 packwas disabled, [and] the exhaust doorand its actuator [were] removed dueto a structural fault.”

Although the no. 2 pack had been dis-abled by maintenance technicians,during the next three days, the air-conditioning-bay blow-out panel wasfound open three times. The reportsaid that the blow-out panel may haveopened because of “leakage at the no.2 pack flexible duct, which was pres-surizing the bay (perhaps from thecabin), or from other leaking seals inthe pack ducting which were lateridentified.”

As a result, maintenance personnelconducted functional checks and leakchecks on the no. 2 pack.

On June 9, when the airplane waslanded in Manchester, England, thetechnical log included a report thatthe no. 1 air-conditioning pack hadoverheated while the airplane was onthe ground in Naples, Italy. After testsshowed that the no. 1 pack was ser-viceable, the maintenance technicianinstalled a new exhaust door and anew actuator on the no. 2 pack.

After the repairs, the airplane was fer-ried from Manchester to Gatwick.

During a descent from FL 190, theflight crew heard “a loud pulsingnoise,” followed by a 2,000-foot-per-minute increase in cabin altitude. Thecrew conducted an emergency descentand landed the airplane at Gatwick,where the airplane was reported asunserviceable and the captain wrote inthe technical log, “A/c failed to pres-surize. All ECAM [electronic cautionalert module] ind(ications) (all pages)normal.”

The captain later filed a flight safetyreport containing a more completedescription of the rapid depressuriza-tion, but the maintenance techniciansaw only the captain’s entry in thetechnical log. The technician had noopportunity to talk to the crew beforeperforming the repairs.

“The engineer had been working onand [had been] deeply engrossed inan engine defect on another aircraftand was called from that job to in-vestigate and rectify [the problem onthe incident airplane],” the reportsaid. “An airline liaison engineer, whohad been involved in the work on theother aircraft, accompanied him.While he was working on [the inci-dent airplane], he was interrupted byquestions about the other aircraft.”

The maintenance technician’s inspec-tion revealed that “the no. 2 blow-outpanel had deployed and the flexibleduct had detached and was in poorcondition,” the report said.


The technician did not locate themetal flat-band clamp that shouldhave been used to secure the aft endof the flexible duct; instead, a nylontie-wrap fell out when he removed theaccess panel to gain access to theduct.

“The size and curvature of the tie-wrapfitted the bellows end,” the report said.“[The maintenance technician] foundthat neither the duct nor the flat-bandclamp were available … at Gatwick,and the airline liaison engineer askedwhether a temporary repair could becarried out; the airline was havingsevere scheduling difficulties due toseveral aircraft having become unser-viceable.”

The maintenance technician, withhelp from other maintenance person-nel, used fiberglass-reinforced adhe-sive tape and two tie-wraps to attachthe aft end of the flexible duct.

“This produced what appeared to bea much more secure arrangementthan that which had previously beenin place,” the report said. “Such a re-pair was outside the approval author-ity of the [maintenance technician],and it should have been consideredby the maintenance company’s mainoperations control (maintrol) and anengineering concession [should havebeen] obtained. Maintrol was contact-ed by telephone, but the personnel atGatwick were advised that no one atmaintrol would take responsibility for

such a repair. Neither did maintroltake any action to prevent the aircraftbeing returned to operation with thisrepair. The [maintenance technician]and other personnel at Gatwick wereconfident in the security of the repairand, after carrying out a functionaland leak check, the engineer signedthe certificate of release to service inthe technical log.”

Nevertheless, the leak check, whichwas conducted using the auxiliary pow-er unit, was not a full-pressurizationtest and did not subject the duct to fullpressure differential.

The report said that the NRV “musthave been damaged at this time toallow the loss of cabin pressure whenthe bellows detached. However, it didnot occur to any of the personnel in-volved, either at Gatwick or maintrol,that detachment of the flexible ductfrom one pack should not have result-ed in a loss of cabin pressure or a fail-ure to pressurize, as described in thetechnical log. The NRV should haveclosed off the outflow from the cab-in, leaving it pressurized by the no. 1system. The failure of the NRV was,therefore, not discovered.”

After maintenance was completed,the airplane was prepared for theflight to Palma de Mallorca. The cap-tain briefed the cabin crew on theprevious problems with the air-conditioning system, including thedepressurization during the morning


ferrying flight to Gatwick, and thecrew altered cabin service proceduresto remove as little equipment as pos-sible from galley area and to delaycabin service until the flight crewconfirmed that the pressurization sys-tem was working properly.

When the passengers boarded, theirdeparture already had been delayedabout 15 hours because of technicalproblems with another airplane, andsome passengers “voiced concernover the serviceability of the aircraft,”the report said.

The report said that the takeoff fromGatwick was uneventful and that thecaptain reduced the rate of climb toabout 1,000 feet per minute to moni-tor the pressurization system.

“Initially, all of the pressurizationsystem indications on the flight deckwere normal,” the report said. “Pass-ing … FL 200, the [captain] selected‘open climb,’ which is the normalmaximum climb power setting.

“Passing FL 300, the [captain] hearda resonance, similar to that experi-enced during the previous sector justprior to the loss of cabin pressure.Again, a decompression occurred,and the cabin altitude began to climbrapidly.”

The maximum cabin altitude experi-enced during the event was 14,000feet.

The airplane’s flight data recordershowed that the descent began afterthe airplane reached 28,600 feet andthat the airplane was leveled at FL280 momentarily before a rapid de-scent began. At the same time, thecabin-pressure warning activated, in-dicating that cabin altitude was morethan 9,550 feet. The warning contin-ued for seven minutes 30 seconds,until the airplane was flown below9,000 feet.

A post-incident examination of theairplane revealed that the no. 2 air-conditioning pack blow-out panelwas out of place. The flexible ductwas disconnected at the aft end, andthe detached ends were damaged; thewalls of the bellows were chafed andsplit.

“Its condition indicated that it hadbeen damaged by rapid fluttering andaxial compression of its convolu-tions,” the report said. “It was theduct’s aft fitting [that] had been thesubject of the repair carried out be-fore the flight.”

The post-incident examination alsorevealed that the NRV was damaged.Its flap was broken in half; half wasmissing, and the half that remainedwas deformed “in a manner [that] in-dicated that it had been slammedagainst the flexible ‘open’ stop, whichnormally contacts the center of the cir-cular flap of the valve,” the report said.A small piece of the broken valve was


found in the under-wing fairing in thebay where the pack is located.

“Its position suggested that the otherfragments had also been expelled out-ward by cabin air through the openend of the duct and had probably beenlost through the blow-out panel thathad opened in flight,” the report said.“This was consistent with bellows de-tachment preceding failure of theNRV.”

The report said that “it seems cer-tain” that the NRV failed during thefirst depressurization incident onJune 10.

“It seems likely that the oscillationof the bellows after it detached on thepositioning flight, as well as the com-peting air flows from the pack and thepressurized cabin, produced severeflow [fluctuations] and pressure fluc-tuations in the downstream part of theduct to the NRV,” the report said.“This resulted in the flap of the[NRV] slamming open and shut,causing it to break. This sequence isconsistent with symptoms consistingof a loud noise and vibration as de-scribed by the crew.”

The report said that the maintenancepersonnel, during their work on theair-conditioning system the day be-fore the incident, failed to detect thedamaged NRV and used an unap-proved method of reconnecting thecondenser outlet duct.

“This resulted in the duct again be-coming disconnected and a subse-quent loss of cabin pressurization,”the report said. “There were somemitigating circumstances in that theindividuals were under considerablepressure to return the aircraft to ser-vice and the requisite spares were notavailable.”

The report said that the maintenancecompany’s investigation of the incidenthad “concluded that there had been sig-nificant deviations by staff from laid-down internal procedures and a failureof the engineering management orga-nization to support line staff.

[The internal investigation] alsofound that the company’s reliability-monitoring system had failed to high-light the recurrent problems with theno. 2 air-conditioning pack.”

The internal investigation said that themaintenance staff at Gatwick shouldbe briefed “on the limits of their au-thority and the concession proce-dure.”♦

[FSF editorial note: This article, ex-cept where specifically noted, isbased on the U.K. Air Accidents In-vestigation Branch final report onoccurrence EW/C2000/6/4.]

Note1. The report by the U.K. Air Acci-

dents Investigation Branch


(AAIB) said that of the 176 pas-sengers, 53 said that they hadshortness of breath, weakness,numbness or tingling sensations.Forty-three said that they hadheadaches, 13 said that they ex-perienced chest pains and fivesaid that they experienced jointpain. The report said, “Given thatthe maximum cabin altitudeachieved during the incident was14,000 feet for less than five min-utes, the likelihood of anyonesuffering the effects of hypoxia(lack of oxygen in the blood-stream) [was] probably limited tothose passengers who wereheavy smokers, obese or other-wise physically unfit.”

In a survey of passengers after theincident, 76 percent of the 106respondents said that they haddifficulty using the oxygen masksand 95 percent of respondentssaid that they lacked confidencein the operation of the emergencyoxygen system. The report saidthat the absence of an announce-ment, after deployment of oxygenmasks, to remind passengersabout how to use them “probablycontributed to the difficulties, per-ceived and real, that the passen-gers experienced.” As a result ofthe investigation, AAIB recom-mended the following:

• That the U.K. Civil AviationAuthority should remind opera-tors, if appropriate, that they

should include pubic addressannouncements as part of post-decompression procedures; and,

• That the Joint Aviation Authori-ties should review requirementsfor passenger briefings involv-ing the operation of emergencyoxygen equipment.

Further Reading fromFSF Publications

FSF Editorial Staff. “Cabin-air Con-tamination Briefly IncapacitatesCrew.” Cabin Crew Safety Volume 37(January–February 2002).

FSF Editorial Staff. “Flight Crew In-capacitation Follows Learjet 35 CabinDepressurization.” Accident Preven-tion Volume 58 (April 2001).

Mohler, Stanley R. “Quick Responseby Pilots Remains Key to SurvivingCabin Decompression.” Human Fac-tors & Aviation Medicine Volume 47(January–February 2000).

FSF Editorial Staff. “Racing BalloonIs Shot Down by Air Force AttackHelicopter in Belarus.” Accident Pre-vention Volume 53 (July 1996).

Mohler, Stanley R. “A Sudden High-altitude Cabin Decompression Imme-diately Threatens Safety of AircraftCrew and Passengers.” Human Fac-tors & Aviation Medicine Volume 41(November–December 1994).


FSF Editorial Staff. “U.S. Studies SayAltitude Chamber Training OffersImportant Hypoxia Recognition

Training at Low Risk.” Human Fac-tors & Aviation Medicine Volume 39(November–December 1992).

MAINTENANCE ALERTS

FAA ProposesInspections of DC-9

Disconnect Panel

The U.S. Federal Aviation Adminis-tration (FAA), citing a Nov. 29, 2000,fire in a McDonnell Douglas DC-9-32, has proposed requiring operatorsof some McDonnell Douglas DC-9airplanes to inspect a disconnect pan-el in the left-forward cargo compart-ment for contamination of electricalconnectors by lavatory rinse fluid andfor the presence of a drip shield. Theinspections of DC-9-10, DC-9-20,DC-9-30, DC-9-40 and DC-9-50 se-ries airplanes would be conducted inaccordance with Boeing Alert ServiceBulletin (ASB) DC9-24A190 Revi-sion 01, dated Nov. 21, 2001. (TheMcDonnell Douglas Corp. is nowBoeing, Douglas Products Division.)

FAA also said that it would issue aflight standards information bulletinto principal inspectors of DC-9 op-erators to discuss circumstances ofthe fire and the importance of prop-er service and proper draining of lav-atory waste tanks and sealing floorpanels.

The FAA actions followed recom-mendations from the U.S. NationalTransportation Safety Board (NTSB)issued July 9, 2002, during the inves-tigation of an accident involving anAirTran Airways DC-9-32. After de-parture from Hartsfield Atlanta(Georgia, U.S.) International Airport,the flight crew observed the activa-tion of numerous circuit breakers andillumination of several annunciatorpanel lights. They declared an emer-gency and returned to the departureairport for landing.

After the landing, a flight attendantobserved smoke at the left sidewallin the forward cabin, and air trafficcontrol observed smoke coming fromthe airplane. The airplane was evac-uated on a taxiway. The airplane wasdamaged substantially; no one in theairplane was injured seriously.

An investigation revealed fire dam-age to the left-forward area of the fu-selage and the cargo compartmentfrom fuselage station (FS) 237 to FS313 and damage to the cabin floor.

“Fire damage was concentrated inan area just aft of the electrical


disconnect panel located at FS 237,which is a junction panel for sevenwire bundles,” NTSB said. “The fu-selage exterior also exhibited heatdiscoloration in an area beneath thelavatory service panel located be-tween FS 237 and [FS] 256 and a soottrail that extended aft from the radiorack vent, located just aft of the lava-tory service panel. Soot was alsopresent throughout the forward car-go compartment and on the cabinoutflow valve near the rear of the air-plane.”

On sidewall insulation blankets andcomponents near FS 237 in the inte-rior area between the forward cargocompartment and the fuselage, therewere blue stains that resembled thecolor of lavatory rinse fluid. Supportbrackets were in place above the FS237 disconnect panel to hold a dripshield, but no drip shield was in-stalled.

Examination of the wires near FS 237revealed beading — considered con-sistent with the heat damage causedby arcing — at the ends of manywires. Investigators opened sevenelectrical connectors and found thatone of the connectors had more ther-mal damage than the others and alsocontained “light blue and turquoisegreen crystalline deposits” and “pin-to-pin shorts.” Tests revealed elevat-ed levels of sulfate (found in lavatoryrinse fluid) in the connector’s grom-met material.

Examination of another AirTran DC-9 revealed that, although a drip shieldwas installed, there were dried blu-ish stains on surfaces near the discon-nect panel. Examinations of twoDC-9s operated by another carrierrevealed that drip shields had not beeninstalled on either airplane and that,although there were no blue stains,“many components were coveredwith a white, mottled substance,which suggests that a fluid other thanlavatory rinse fluid may have leakedfrom above,” NTSB said.

NTSB said that two C-9A airplanes— the military equivalent of DC-9s— were involved in incidents similarto the AirTran accident. Drip shieldshad been installed in both C-9As;nevertheless, electrical componentswere damaged by shorting and fluidsaturation.

The Boeing DC-9 maintenance man-ual says that the lavatory waste-disposal system is serviced by drain-ing, washing and flushing the wastetank and filling it with at least 3.5gallons (13.2 liters) of clean rinse flu-id. AirTran’s procedure was to use atleast 3.5 gallons of rinse fluid but nomore than four gallons (15.1 liters).

NTSB said that, when the accidentoccurred, “neither Boeing’s [proce-dures] nor AirTran’s procedures spec-ified how to determine when the tankhas been completely drained. Incom-pletely draining the tank can, over


time, lead to an overflow of fluid ontothe lavatory floor; the fluid can thenmigrate beneath the floor and ontocomponents below, especially in ar-eas where the floor panels are notproperly sealed.”

NTSB said that after the accident,AirTran revised its procedures to“emphasize the importance of com-pletely draining the waste tank,” andBoeing issued the ASB and ServiceLetter DC-9-SL-53-101 discussingthe importance of “properly sealingfloor panels and adhering to lavatoryservicing procedures.”

Fatigue Cracks Cited inMetro III Engine

Failure

The flight crew of the Fairchild In-dustries SA227-DC Metro III appliedfull power for takeoff from an airportin Australia on Aug. 12, 2001, thenheard a loud bang. They retarded thethrottles and observed an increase inleft-engine exhaust gas temperature.They then shut down the left engine.After a passenger observed smokeand flames from the left engine, theflight crew discharged the fire bottleinto the left engine, then shut downthe right engine and evacuated theairplane.

An inspection of the airplane revealeddamage to the left-engine turbineblades and the exhaust nozzle.

The Australian Transport SafetyBoard said, in a report on the inci-dent, that the failure of the Allied Sig-nal (Garrett) turboprop engine(TPE331-12UHR-701G), was a re-sult of the failure of the turbine first-stage disc-rotating air seal.

The report said that the engine hadaccumulated 9,140 hours and 3,067cycles since new. In May 1997, theinner baffle (part no. 3108039-2) wasreplaced in accordance with AlliedSignal service bulletin (SB) TPE331-72-2002, and in July 1999, the com-pressor interstage seal assemblysupport was replaced during an en-gine overhaul, in accordance with SBTPE331-72-2030. After the overhaul,the engine was installed in the inci-dent airplane.

The rotating air seal (part no.3103839-3) apparently had been inthe incident airplane since new. Thereport said that during the 1999 en-gine overhaul, the rotating air sealwas inspected and was found service-able. The report said that a crackedrotating air seal was rare on enginesthat had been maintained in accor-dance with the two SBs.

Examination of the rotating air sealshowed that the entire rim had sepa-rated from the flanged section andthat 70 percent of the rim circumfer-ence had been recovered. Most ma-terial from the outer 10 millimeters(0.4 inch) of the plate flange was


missing. The report said that in onearea with substantial loss of materi-al, there was a “short length of frac-ture showing evidence of fatiguecrack propagation” that had beenpresent before the incident.

The engine manufacturer said that anumber of in-flight engine shutdownshad occurred because of separationof the rotating air seal plate rim thatfollowed cracking in the rim. Thecracking resulted from elevated rimoperating temperatures caused by“hot gas leakage from deterioratedfirst-stage stator assembly hardware.”The two SBs and changes in the en-gine maintenance manual were in-tended to address the problem.

“The subject rotating air seal had ac-cumulated over 6,000 hours beforethe engine had the requirements of theservice bulletins incorporated,” thereport said. “At that time, the seal wasinspected in accordance with the cur-rent requirements. However, the pos-sibility that the rotating seal failurewas related to damage incurred dur-ing the seal’s prior time in servicecould not be excluded.”

In a separate technical analysis, ATSBsaid, “Thermal fatigue cracking is aproblem associated with repeated dif-ferential heating of components and,as such, many turbine engine com-ponents are potentially susceptible topremature degradation in this man-ner. Engine design and operation

present the best opportunities forcombating thermal fatigue. Appropri-ate cooling of components is criticalto resistance, and design enhance-ments may be able to be made in thisarea. Similarly, measures taken tominimize abrupt changes in powersettings can also be beneficial in less-ening thermally induced stresseswithin the engine.”

Faulty Inspection Citedin Separation of EngineCowling During Takeoff

During takeoff from Seattle-Tacoma(Washington, U.S.) International Air-port on a nonscheduled internationalcargo flight, the cowlings of the no.1 engine and no. 2 engine on a Boe-ing DC-8-63F separated from the air-plane. The flight crew returned to theairport for landing. The airplane’s leftwing and left horizontal stabilizerwere damaged substantially; none ofthe three crewmembers in the airplanewas injured.

The U.S. National TransportationSafety Board (NTSB) said, in the fi-nal report, that the probable cause ofthe accident was “inadequate inspec-tion of the no. 1 and [no.] 2 enginecowls by company maintenance per-sonnel and inadequate preflight in-spection by the flight engineer.”

The aircraft maintenance log showedthat maintenance had been performed


before the flight to lubricate, inspectand check the four thrust reversers.(After the previous flight, the crewhad said that the no. 2 thrust reverserwas inoperable; a deferred mainte-nance item involved a problem withthe no. 1 thrust reverser.)

Work on the no. 2 thrust reverser wasassigned to a maintenance technicianwho also was responsible for identi-fying and correcting a problem withthe captain’s course deviation indica-tor (CDI). The technician said that hecompleted his assigned tasks, thenasked the technician working on theno. 1 thrust reverser to “finish up theaircraft and close all engine cowls,”the report said.

“He then signed off the no. 2 thrustreverser in the maintenance log andleft for the day. (This [maintenancetechnician] stated that he worked un-til 1645 on this shift, three hours and45 minutes past the end of his nor-mal shift.) This [maintenance techni-cian] reported that when he left, allcowlings were wide open and heldopen by their hold-open rods.”

The maintenance technician who wasasked to close the cowling doors saidthat he had lowered the doors but thathe and another maintenance techni-cian were unable to secure them. Hesaid that he had written in the turn-over log that all four cowling doorsrequired securing and that he also hadtold two technicians on the next shift.

One of the maintenance technicianswho received the turnover report saidthat he had been given the report at1530, about 30 minutes after he re-ported to work. He said that the pre-vious day, he had been scheduled towork until 0130 but actually hadworked until 0800, then went homeand was unable to sleep before return-ing to work. He said that his primaryassignment involved work on a Boe-ing 747 but that he had worked on theincident airplane about 1630; at thetime, the cowlings on the no. 1 en-gine and no. 2 engine were closed andthe cowlings on the no. 3 engine andno. 4 engine were open.

“None of the [maintenance person-nel] indicated in their statements thatthey checked that the no. 1 or [no.] 2cowlings were latched, although theindividual who marshaled the aircraftout on the accident flight indicatedthat he performed a ‘basic walk-around’ of the aircraft,” the reportsaid.

The flight engineer, who conducteda pre-flight walk-around inspection,said that all cowlings were “verifiedclosed and latched prior to takeoff.”

The captain said that the first indica-tion of a problem occurred duringtakeoff, when the no. 2 engine high-pressure section revolutions-per-minute indication was zero, the no. 2engine generator light illuminatedand the airplane rolled left.


The report said that examinations ofthe recovered cowling sections re-vealed that “no cowl sections were at-tached to each other by any latchmechanisms, and no evidence of dis-tress to any latches, latching pins orassociated areas was observed. Of fourlatches observed on the sections lefton the runway, three were observed inthe unsecured position and one wasobserved in the latched position (butnot engaged to its mating latch pin;however, a … maintenance represen-tative [said] that the latch found in thelatched position had been in the unse-cured position when returned, and thatthe airline’s personnel had left it in thelatched position in the course of dem-onstrating/practicing its operation.Both of the two latches observed onone of the sections recovered from [anarea near the runway] were observedto be in the unsecured position.”

InspectionsRecommended forPiper Seneca Nose

Undercarriage

The Civil Aviation Authority of NewZealand has recommended that opera-tors and maintainers of Piper PA34-200T Seneca airplanes regularly inspectthe nose undercarriage assembly forcorrect alignment and that they beaware of taxiing and towing limitations.

The August 2002 actions followed aJan. 25, 2002, accident in which the

nose landing gear of a Piper Senecafailed to extend during an attemptedlanding at Gisborne Aerodrome. Thepilot of the emergency medical ser-vices flight and a non-flying pilotused normal landing-gear-extensionprocedures and emergency landing-gear-extension procedures before di-verting the flight to HastingsAerodrome, where the pilot landedthe airplane with the landing gear re-tracted.

The airplane received minor damage,and the two crewmembers and onepatient in the airplane were not in-jured.

The nose undercarriage was steerableand was hinged to retract into the nosewheel well. The pilot’s movement ofthe rudder pedals moved both the air-plane’s rudder and a “steering chan-nel” that was connected to thenosewheel by a steering tiller and asteering ball. When the pilot retract-ed the landing gear, the steering ball“slid out of the steering channel anddown a track assembly channel,” thereport said.

An investigation revealed that whenthe pilot retracted the landing gear onthe accident flight, the steering ballmoved out of the steering channel andalong the outside of the channel, thenbecame lodged there. When the pilotmoved the lever to extend the land-ing gear, the available hydraulic pres-sure was insufficient to free the ball


and extend the nose landing gear. Thereport said that, if the ball had beenfreed and the nose landing gear hadbeen extended, the airplane wouldhave had offset nosewheel steering —or perhaps uncontrollable nosewheelsteering — after landing.

The New Zealand Transport AccidentInvestigation Commission said, in thefinal report on the accident, “The rea-son for the undercarriage malfunctionwas not fully determined. However,the nose undercarriage retraction sys-tem had become misaligned overtime, possibly because of a combina-tion of the nose leg exceeding its lim-itations during aircraft towing and theaircraft being turned too tightly whilemaneuvering over rough ground. Themisalignment of the undercarriageprobably contributed to [its] jammingafter retraction.”

Inspection of the nose undercarriageassembly was required every 100 flighthours. Nevertheless, the report said thatthe inspection typically would have giv-en a maintenance technician a side viewof the upper portion of the assemblyand that misalignment of the assemblywould have been difficult to identify.

“A vertical view … would have re-quired the removal of the aircraft’slower panel, which only occurredwhen specifically required,” the re-port said. “The misalignment could,therefore, have been present for someconsiderable time.”

[A similar accident involving a Pip-er Seneca at an airport in Englandresulted in minor damage to the air-plane; the flight instructor andstudent pilot were not injured. Main-tenance personnel examined the air-plane and determined that, during atow by a tug, the airplane’s steeringlimits had been exceeded. (See “TowDamage Prevents Extension ofNose Landing Gear.” Flight SafetyDigest Volume 21 [May–June 2002]:109–110.)]

Bearing-seal InstallationCited in Nosewheel

Failure on EMB-145

An Embraer EMB-145 was beinglanded in Edinburgh, Scotland, onMarch 2, 2001, after a flight fromParis, France, when the flight crewheard a “high-speed noise” followingtouchdown. Because the crew be-lieved that a tire had failed, theystopped the airplane on the runwayand asked fire fighters and mainte-nance personnel to examine the tire.When the crew began to taxi the air-plane to allow the maintenance tech-nician to hear the noise, the leftnosewheel fell off.

An inspection revealed that the nose-landing-gear axle had broken. The U.K.Air Accidents Investigation Branchsaid, in a report on the incident, thatthe area next to the fracture “showedsigns of severe ‘over-temperature,’


with paint in the axle bore blisteredand blackened.”

The report said, “The evidence clear-ly indicated that the [nose-landing-gear] axle had failed as a result ofsevere overheating, which had beengenerated by bearing [no.] 2 havingoperated in a grossly deterioratedcondition. Local embrittlement andcracking had led to rapid fracturingof the axle, probably under normalloading.”

The report said that similar problemsinvolving other EMB-145 airplaneshad been caused by dirt and water inthe bearings. In this occurrence, how-ever, double seals had been fitted in-correctly at three bearing positions,resulting in “distortion and abnormalwear of the seals and severe degrada-tion of the standard of bearing seal-ing,” the report said.

The report said that causes of incor-rect installation were not determinedbut that “there clearly had been con-fusion over the different standards ofseal deflector configuration that mayhave been brought about by the factthat ‘wheel assembly’ part numbershad not been changed to reflect theintroduction of the wheel assemblymodification.”

After the accident, the operator in-spected its other EMB-145 airplanesfor incorrect installations of wheelbearing seal/deflectors, and found no

discrepancies. The operator also issuedan alert quality assurance notice andapplied decals to EMB-145 nose-land-ing-gear doors to increase awarenessof the different seal/deflector standardsdescribed in the Aircraft MaintenanceManual (AMM). Later, the operatorrequired that when nosewheels werereplaced, the replacements shouldhave the most recent standard of seal/deflector.

After the accident, the manufacturerissued a field report (no. GST-0773/01) that said that nose-landing-gearbearing inspections should be con-ducted in accordance with the BFGoodrich Component MaintenanceManual (CMM) 32-49-04.

The CMM and the AMM later wererevised to include more recent infor-mation about part numbers and prop-er assembly methods.

Overheating ofPitot-static Hose Cited

In Flight Deck Fire

The airplane was descendingthrough Flight Level 200 (approxi-mately 20,000 feet) for an approachto an airport in Scotland when theflight crew observed smoke andsmelled a burning odor. The captainsummoned a flight attendant. Whenthe flight attendant entered the flightdeck, she observed flames comingfrom the wall behind the captain’s


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seat; she used a fire extinguisher toextinguish the flames.

The flight crew declared an emergen-cy and landed the airplane at the des-tination airport. They stopped theairplane on the runway, shut down theengines and lowered the airstairs. Thepassengers and crew disembarked,and the airplane was towed to a re-mote stand.

An investigation revealed extensiveoverheating damage to a flexible hoseconnected to a port on the upper-leftcombined pitot-static probe.

The airplane has four combined pitot-static probes, two on each side of theforward fuselage. The upper-left pitot-static probe is located behind the cap-tain’s seat. An internal heater elementprevents ice accumulation on theprobes. The heater circuit is protectedby a five-ampere circuit breaker; dur-ing the incident, pitot-static heat wason and the circuit breaker remainedretracted.

The investigation revealed that theoverheating damage was a result of“internal shorting of the probeheater to the probe body, in combi-nation with degraded bonding be-tween the probe and structure.Corrosion … contributed to thisbonding degradation, making flexiblehose metallic components the path toground.”

The report said that the corrosion wasa result of “the by-products of exteri-or cleaning of the aircraft, coupledwith thermal cycling of the probe, andthere was also evidence of internalcontaminants, probably due to thecorrosion, which had allowed the in-ternal shorting of the heater elementto the probe body.”

After the incident, the operator in-spected combined pitot-static probeson all airplanes in the fleet; no otheranomalies were found. The airplanemanufacturer also began a reviewof bonding of the combined pitot-static probes.♦


repairs. The course can be complet-ed in about six hours and includes amastery test. A certificate of comple-tion is given to those who completethe course satisfactorily.

For more information: AviationLearning, One Airport Way, Roches-ter, NY 14624 U.S. Telephone: (888)458-5040 (U.S.) or +1 (585) 328-5000 ext. 268.

Cutting Tool RemovesAircraft Seam Sealants

The SR Cutter and the SR RadialBristle Disc remove seam sealantsquickly and safely during aircraftmaintenance without damaging un-derlying materials, said the manufac-turer, 3M Aerospace.

integral metal mandrel for use onright-angle drills at low speeds, themanufacturer said. The SR RadialBristle Disc uses plastic abrasivesto remove thin layers of sealantswithout damaging paint. Both prod-ucts eliminate the need for harshchemicals and hand scraping to re-move seam sealants, the manufactur-er said.

For more information: 3M Aero-space, 3M Center, Building 220-8E-05, St. Paul, MN 55144-1000 U.S.Telephone: (800) 362-3550 (U.S.) or+1 (651) 733-9105.

Oversleeve ProtectsCables, Hoses From Heat

The Fyrejacket protective oversleevecombines fiberglass and silicone rub-ber to protect cable assemblies, hoseassemblies, fuel lines and hydrauliclines from heat and flame, said themanufacturer, Federal-Mogul Sys-tems Protection Group.

The oversleeve is made from braid-ed fiberglass substrate and coatedwith silicone rubber to protectagainst temperatures up to 500 de-grees Fahrenheit (260 degrees Cel-sius), molten-material splash andwelding sparks. The oversleeve ex-pands to accommodate fittings andcouplings and is asbestos-free. Itcomplies with the requirements ofSociety of Automotive Engineers

SR Cutter

The SR Cutter is a plastic rotary cut-ting tool that removes thick layersof sealants. It is available in diame-ters of 0.40 inch (10 millimeters) and0.83 inch (21 millimeters) and has an


(SAE) Aerospace Standard AS 1072Type 2, the manufacturer said.

For more information: Federal-Mogul Systems Protection Group, 241Welsh Pool Road, Exton, PA 19341U.S. Telephone: +1 (610) 363-2600.

United States for developer AsahiGlass Co. of Japan.

Lumiflon’s durability reduces the fre-quency of repainting and associatedmaintenance costs, AGA Chemicalssaid.

For more information: AGA Chemi-cals, 2201 Water Ridge Parkway,Suite 400, Charlotte, NC 28217 U.S.Telephone: +1 (704) 329-7614.

Flashlight UsesLED Technology

The Lightwave 2100 Portable Light-ing System flashlight uses four light-emitting diodes (LEDs), each with atypical life of thousands of hours, saidthe manufacturer, Lightwave.

Fyrejacket Protective Oversleeve

Coating ProtectsAgainst Corrosion

Lumiflon, a durable resin used in ex-terior paint, protects surfaces — in-cluding aircraft exteriors — againstcorrosion caused by exposure towater, oxygen, ultraviolet light andchemicals, said AGA Chemicals,which markets Lumiflon in the

Portable Lighting System

The flashlight has a printed circuitboard that controls the flow of volt-age from three AA alkaline batteries.This procedure means that the batter-ies will last 14 times longer than sim-ilar batteries powering typicalflashlights, the manufacturer said.The flashlight is water-resistant and


shockproof, with an industrial gradeon-off switch.

For more information: Lightwave,PMB 325, 5665 Highway 9, No. 103,Alpharetta, GA 30004 U.S. Tele-phone: +1 (678) 393-9072.

Radiant Tube HeatersProvide Even Heating of

Large Spaces

Ambi-Rad gas-fired, vacuum-operatedER-series radiant tube heaters pro-vide an even heat distribution forbuildings with large open spaces anddoors that often are open, said themanufacturer, Advanced RadiantSystems.

The heaters are designed to warmpeople and objects near the floor rath-er than the air in the entire space. Theheaters have burner ratings that rangefrom 40,000 British thermal units perhour (Btu/h) to 150,000 Btu/h, andare available in U-shaped tubes orstraight tubes from 20 feet (sixmeters) to 60 feet (18 meters) long.

As many as 10 burners can be con-nected to a single exhaust fan, themanufacturer said.

For more information: Advanced Ra-diant Systems, 12910 Ford Drive,Fishers, IN 46038 U.S. Telephone:(888) 330-4878 (U.S.) or +1 (317)577-0337.

Custom-designedHeaters Warm Complex

Surfaces

Molded-to-Shape heaters provide ef-ficient, even heat distribution forcomplex, large surface areas, said themanufacturer, Elmwood Sensors, anInvensys Sensor Systems company.

The heaters are custom designed andthen formed, molded or curved toconform around cylindrical surfac-es and three-dimensional shapes.They are equipped with single-layeror multi-layer etched circuits orwire-wound circuits and single-watt,multiple-watt and variable-watt den-sities. They typically are used to pro-long battery life in cold environmentsand in other applications, includingaerospace electronics and aircraft gal-ley equipment, the manufacturer said.

For more information: Elmwood Sen-sors/Invensys Sensor Systems, 500Narragansett Park Drive, Pawtucket,RI 02861 U.S. Telephone: +1 (401)727-1300.Radiant Tube Heaters


Megohmmeter ProvidesAutomated Insulation

Measurements

The Model 5060 digital/analog me-gohmmeter is a fully automated5,000-volt insulation tester that pro-vides measurements to 10,000 gigao-hms, said the manufacturer, AEMCInstruments.

5,000-volt Insulation Tester

The megohmmeter has a softwarepackage for display of test results andgraphs and a memory function forstorage of test results. The megohm-meter can be programmed and con-trolled by a personal computer, themanufacturer said.

For more information: AEMC Instru-ments, 200 Foxborough Blvd., Fox-borough, MA 02035-2872 U.S.Telephone: +1 (508) 698-2115.

Device Protects AgainstStatic Discharge

The Tow Bar Mounted GroundingAssembly (TBMGA) protects aircraftground crews and equipment fromstorm-related static discharge of up to120 kilovolts, said the manufacturer,Lightning Eliminators and Consultants(LEC). The TBMGA also protectsagainst “bound charge,” which occurswhen a storm cell induces an electri-cal charge on everything beneath thecell — a condition 1,000 times morefrequent than a direct lightning strike,the manufacturer said.

The TBMGA comprises stainless-steel components and can beclamped with U-bolts to aircraft towbars used to move aircraft of all siz-es. A spring-loaded plunger pressesa stainless-steel castored tire to anydriving surface to assure positiveground connection during all phas-es of ground operation, the manufac-turer said. The device eliminates theneed for time-consuming proceduresto protect against static discharge.

For more information: LightningEliminators and Consultants, 6687Arapahoe Road, Boulder, CO 80303U.S. Telephone: +1 (303) 447-2828.♦

Want more information about Flight Safety Foundation?

Contact Ann Hill, director, membership and development,by e-mail: [email protected] or by telephone: +1 (703) 739-6700, ext. 105.

Visit our Internet site at <www.flightsafety.org>.

Submit your nomination(s) via our Internet site.Go to http://www.flightsafety.org/hf_award.html

For more information, contact Kim Granados, membership manager,by e-mail: [email protected] or by telephone: +1 (703) 739-6700, ext. 126.

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F L I G H T S A F E T Y F O U N D A T I O N – A I R B U S H U M A N

F A C T O R S I N A V I A T I O N S A F E T Y A W A R D

The Flight Safety Foundation–Airbus Human Factors in Aviation SafetyAward was established in 1999 to recognize “outstanding achievement inhuman factors contributions to aviation safety.” The award was institutedto encourage human factors research that would help reduce humanerror — one of the most common elements in aviation accidents.

The award — instituted by the Foundation and sponsored by Airbus— is presented to an individual, group or organization for a one-timecontribution or sustained contributions in the field of human factors.The award includes an elegant engraved wooden plaque.

The nominating deadline is Nov. 29, 2002. The award will bepresented in Geneva, Switzerland, at the FSF European Aviation SafetySeminar, March 17–19, 2003.�

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