Pilot Debrief

PIPER PA24 near San Jose, CA — 2018-05-21

Final reportWPR18LA153
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Date
2018-05-21
Location
San Jose, CA, USA
Airport
KSJC
Aircraft
PIPER PA24
Registration
N244TW
Category
Airplane
Highest injury
None
Fatalities
0
Phase of flight
Landing

Probable cause

A landing gear retraction during the landing rollout for reasons that could not be determined based on the available evidence.

NTSB narrative

The pilot had rented the airplane and conducted an uneventful personal flight earlier that day. He departed later that afternoon, destined for an airport a few hundred miles away. According to the pilot, after the airplane was established on the downwind leg, he extended the landing gear and observed that the landing gear position indicator light was illuminated green, which denoted that the landing gear was down and locked into position. He verified that indication on the base leg. The approach and touchdown were normal and uneventful, and the pilot then began to brake the airplane. When the airplane was traveling about 30 mph, the landing gear "suddenly collapsed." The airplane slid on its belly and came to a stop on the runway, which resulted in substantial damage to the fuselage. During recovery of the airplane, the cockpit landing gear handle was found to be in the fully down position. Initial postaccident examination of the airplane revealed that the two main landing gear (MLG) could be fully extended via the normal cockpit landing gear handle but that the nose landing gear (NLG) did not fully extend, the extension motor did not shut off, and the green cockpit indicator light did not illuminate. Manual attempts to fully extend the NLG by pulling it forward were unsuccessful. Aft-directed light-to-moderate force applied to the NLG tire resulted in unlocking the two MLG, which allowed all three gear to be retracted via manually pushing on the NLG. These results demonstrated that the landing gear system was susceptible to uncommanded retraction when the system was not properly adjusted. The reason for the failure of the NLG to fully extend and lock after the accident could not be determined, and the investigation could not determine if this condition existed before the accident. During subsequent examination, the NLG was mechanically isolated from the rest of the landing gear system. Subsequent landing gear travel tests in this configuration revealed that all three landing gear were able to be independently moved into their respective fully extended and locked positions. When the NLG was fully extended, it was more difficult to dislodge by aft pressure to the NLG tire than during the previous examination. The NLG travel change that resulted from mechanically isolating the NLG indicated that after the accident, there was some physical constraint that limited NLG travel and prevented downlock; however, the investigation was unable to determine the nature or cause of the NLG travel constraint. If the constraint was present before the accident, it is likely that the landing gear motor would not have shut off, the green cockpit light would not have illuminated, and the NLG would not have fully extended to the locked position when the pilot extended the landing gear. The reasons for the differences between the preaccident landing gear functionality reported by the pilot and the postaccident observations of landing gear functionality could not be determined.

Analysis

Primary failure mode
Mechanical failure
First missed decision gate
Proper maintenance checks on landing gear system before flight could have prevented failure.

NTSB coding

Evidence available

  • 8 docket documents
View NTSB final reportView NTSB docket

Docket documents8

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