DeHavilland DHC-8-311Piedmont Airlines
Philadelphia, PA, USA · 2008-11-16·N326EN
What happened
NTSB summary, verbatimThe airplane was on approach for landing. When the landing gear was selected to the extended position, the main landing gear extended properly but the nose landing gear did not. The crew performed a go-around, exited the airport airspace, and unsuccessfully attempted to extend the nose landing gear using several checklists and in consult with ground-based maintenance personnel. A subsequent fly-by of the air traffic control tower confirmed that the nose landing gear doors were open, but that the nose landing gear was not extended. The captain subsequently landed the airplane with the nose landing gear retracted and delayed lowering the nose until the slowest speed possible. The nose of the airplane contacted the runway and the airplane slid for about 525 feet before it stopped. There was no fire, and the passengers deplaned normally at the scene. On-site examination of the airplane and a laboratory examination of the nosegear components revealed that the steering links had been circumferentially loaded in tension beyond their load-carrying capacity. Failure of the steering links allowed the nosewheels to rotate in the wheel well and become wedged within the structure. Hardness testing satisfied the manufacturer's minimum requirements and no determination could be made as to when the overload occurred.
Photographs
1the aircraft, and what the investigators foundProbable cause
the Board's determinationThe mechanical overload of the nosewheel steering links for undetermined reasons, which resulted in nose landing gear rotation and its subsequent wedging within the wheel well structure.
Occurrence sequence
2 stepsNTSB coding · CICTT taxonomy- 1 · LandingAbnormal runway contact
- 2 · ApproachSys/Comp malf/fail (non-power)defining event
Findings
1 causal · 1 contributing- CAUSEAircraft › Aircraft systems › Landing gear system › Gear extension and retract sys — Capability exceeded
- FACTORAircraft › Aircraft systems › Landing gear system › Nose/tail landing gear — Malfunction
Sequence of events
8 timed eventsfrom the FDR factual report · claude-sonnet-5- 550,530 sec (SRN)Departurep.3The aircraft departed
- 551,517 sec (SRN)Approachp.3The aircraft began an initial descent to PHL
- 551,670 sec (SRN)Go-around 1p.4Power was applied to both engines and a climb was initiated to go around
- 553,080 sec (SRN)Approachp.4The aircraft begins a second descent to PHL
- 553,460 sec (SRN)Go-around 2p.4Power was applied to both engines and a climb is initiated to go around
- 554,910 sec (SRN)Final Approachp.4The aircraft began its final descent to PHL
- 555,835 to 555,876 sec (SRN)Landingp.4The aircraft landed and decelerated at PHL; a precise time of landing could not be determined based on available FDR parameters
- 555,880 sec (SRN)Post-landingp.4The engine shutdown process began
NTSB analysis
from the final reportThe airplane was on approach for landing. When the landing gear was selected to the extended position, the main landing gear extended properly but the nose landing gear did not. The crew performed a go-around, exited the airport airspace, and unsuccessfully attempted to extend the nose landing gear using several checklists and in consult with ground-based maintenance personnel. A subsequent fly-by of the air traffic control tower confirmed that the nose landing gear doors were open, but that the nose landing gear was not extended. The captain subsequently landed the airplane with the nose landing gear retracted and delayed lowering the nose until the slowest speed possible. The nose of the airplane contacted the runway and the airplane slid for about 525 feet before it stopped. There was no fire, and the passengers deplaned normally at the scene. On-site examination of the airplane and a laboratory examination of the nosegear components revealed that the steering links had been circumferentially loaded in tension beyond their load-carrying capacity. Failure of the steering links allowed the nosewheels to rotate in the wheel well and become wedged within the structure. Hardness testing satisfied the manufacturer's minimum requirements and no determination could be made as to when the overload occurred.