Lufthansa B744 at Frankfurt on Nov 26th 2010, right hand main gear fractured during line up

Last Update: August 14, 2019 / 16:38:44 GMT/Zulu time

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Incident Facts

Date of incident
Nov 26, 2010

Classification
Report

Flight number
LH-510

Aircraft Registration
D-ABVM

Aircraft Type
Boeing 747-400

ICAO Type Designator
B744

D-ABVM still on taxiway L the following day(Photo: Sebastian Schwakenberg)A Lufthansa Boeing 747-400, registration D-ABVM performing flight LH-510 from Frankfurt/Main (Germany) to Buenos Aires Ezeiza,BA (Argentina) with 257 passengers and 17 crew, was taxiing on taxiway N towards Frankfurt's runway 18 for departure. A preceding Airbus A319 was cleared for takeoff and began moving, the 747 had been cleared to line up, the 747 crew taxied their aircraft slowly towards the runway for line up, when the A319 stopped again. The 747 crew applied brakes but felt a sharp loud thump from the right side of the aircraft. After the A319 departed the 747 crew decided to taxi onto runway 18 and vacate the runway via taxiway L. After vacating the runway the aircraft was stopped, the passengers disembarked via mobile stairs supplied by responding emergency services and were bussed back to the terminal.

The German BFU released their bulletin reporting the occurrence was rated an accident.

The right hand main gear was found fractured in the area of the trunnion, the rear bearing of the gear cylinder. Damage was also found in the gear bay and the landing flaps, hydraulic fluid was leaking. The right hand wing had been punctured through above the main gear, the outer skin of the fuselage had been punctured above the right hand wing. A 30cm (12 inch) long piece of the right main gear was found on taxiway N.

On Aug 14th 2019 the BFU released their final report without a formal conclusion.

The BFU reported a load evener system, formerly used on Boeing 747-200 and -300 types, had required a "fill plug bore", the surface of which had received a nickel coating. However, below the nickel coating corrosion had developed initiating a crack that ultimately led a stress fracture.

The BFU wrote:

The fractured outer cylinder was an older version which originally had been used in the B747-200/300. For these airplanes, there was a ‘load evener’ system which would apply an even pressure to all four main landing gear struts in order to keep the airplane level anytime the airplane weight was being carried by the landing gear. Based on service experience, the ‘load evener’ system was omitted for the B747-400 model. In order for an ‘older style’ (with the load evener system) outer cylinder to be used in aircraft types such as the B747-400 the manufacturer modified it by filling the fill plug hole (for the evener system) with a plug. It was secured with a bolt (Appendices Fig. 7). The plug was subject to the pressure of the nitrogen fill of the landing gear. The surface of the fill plug bore was coated with nickel.

The fractured outer cylinder on the accident aircraft was manufactured in 1976 for an older model of the B747 which had the load evener system installed. For use on the B747-400, the fill port on the strut for the evener system was plugged. The landing gears of the B747 do not have a life span limitation due to the redundancy of having 4 main landing gears to support the weight of the airplane. If a main landing gear fails, the other three are certified to carry the weight of the airplane during taxi, takeoff and landing. Therefore no detailed information as to the number of cycles on the fractured gear was available. Maintaining cycle/hour counts are therefore not required for components which are not subject to life span limitations. Estimates show that the outer cylinder had completed about 27,750 cycles. During its life span the outer cylinder was subject to maintenance actions in 1996 and 2003. Among other things, the area of the fill connection was overhauled so that it could be fitted to a B747-400 model. Since the last overhaul it had completed about 4,500 cycles.

The fractured outer cylinder was the last of this kind which the operator had still used. During maintenance work it was replaced by the newer version which was manufactured without the evener system fill plug.
Incident Facts

Date of incident
Nov 26, 2010

Classification
Report

Flight number
LH-510

Aircraft Registration
D-ABVM

Aircraft Type
Boeing 747-400

ICAO Type Designator
B744

This article is published under license from Avherald.com. © of text by Avherald.com.
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