Boeing 737-236 series 1, G-BGJL: Main document - Leonardo

A check on the hardness of the CCOC in the vicinity of the bulgedarea suggested that temperatures
of up to 930°C had beenexperienced by the casing, at which temperatures the materialproperties
would have been significantly impaired.
The fuel nozzles from engine P 702868 were tested against themanufacturer's specifications for
both the flow rate and flowpattern, which could affect the local heat distribution and thusthe level
of distress felt by the can. The conclusion of the testswas that they did not reveal any functional
discrepancies comparedwith in-service standards.
The No 9 nozzle exhibited heavy wear of the outside diameter ofthe nozzle nut where it engages in
the No 9 can, consistent withexcessive movement of the can relative to the nozzle having
occurredafter the dome section had separated from the rest of the can.
The FCU was examined to check its serviceability and settings.Whilst the unit had suffered some
fire damage, it was still possibleto bench test it and to extract various parameters relevant tothe
accident. In particular, it was found that there was no evidenceto support a lack of 'idle speed
repeatability' - ie failure tomaintain an idle speed setting. The condition of the unit wasgenerally as
might be expected from a unit with about 15,000 hourssince last bench calibration. The idle trim
screw was found aboutmid-way in its 22-turn range. It was concluded that the unit wascapable of
running a JT8D-15 engine throughout its operationalrange.
FDR evidence indicated that both the right and left reverser systemsdeployed normally, but that
only the right reverser retractedagain into the stowed position; the left reverser remained
fullydeployed.
The left reverser mechanism had suffered general fire damage,resulting in partial seizure of the
feedback mechanism and stiffnessof the lock mechanisms. The operating cable and interlock
systemmounted in the wing above the pylon were also affected by thefire. The retraction
mechanism operated satisfactorily when thehydraulic system was pressurised by means of a hand
pump, andthe only evidence of abnormality was stiffness of the variouslinkages as a result of the
fire.
Analysis of the flight recorder data from preceding flights showedthat the left engine oil pressure
typically decayed to 35 psiat an N2 of 26% (the oil pressure switch which inhibits the thrustreverser
actuating system is set to trip at a nominal 35 psi).Recorder data for the accident flight indicates
that the leftengine oil pressure fell below this value 3 seconds after thereverser had deployed, but
approximately 6.5 seconds before reversethrust was de-selected (assuming right and left reverse
were de-selectedtogether), de-activating the operating system before reverse wascancelled.
1.12.2.2 Fire (Appendix 8 Figs a-b)
Fuselage
The whole of the rear fuselage aft of seat row 19 had collapsedonto the ground as a result of
external fire attack on the fuselagelower skin and longerons between frames 867 and 907, and
firedamage to the cabin floor structure which led to floor collapseover much of the area above the
aft cargo hold. Aft of the wingtrailing edge, between seat row 14 and the rear entrance vestibule,the
fuselage was partially destroyed by a combination of externaland internal fire. The greatest damage
was concentrated on theleft side in the vicinity of the aft baggage hold.
Empennage