Cessna A185F N1718R accident near Skwentna, Alaska

Probable cause

Maintenance personnel’s reuse of worn hardware during the installation of the landing gear assembly and the hardware’s failure and subsequent separation of the gear leg from the landing gear box assembly during taxi.

NTSB analysis

The pilot reported that, while taxiing for takeoff from a remote, snow-covered lake, the right landing gear leg collapsed, resulting in substantial damage to the landing gear box assembly and door post assembly.

A postaccident examination of the right landing gear leg assembly revealed that the gear leg separated from its position in the landing gear box assembly and folded under the airplane. The bolt that secured the gear leg to the landing gear box assembly remained in place; however, the nut was found in the belly of the airplane.

Although the hardware installed on the airplane’s main landing gear spring differed from the hardware specified in the airplane manufacturer’s parts catalog, the composition and hardness of the installed bolt were consistent with typical specifications for an AN-type bolt. However, the bolt and nut exhibited worn threads consistent with progressive wear over time rather than a sudden overload. The mechanic who performed a landing gear change about a year and a half before the accident stated that, although he did not recall the hardware used during the gear change, when he changes landing gear, he uses the hardware provided by the owner for installing the landing gear.

Based on the condition of the nut and bolt, the worn hardware was likely re-used during the installation of the landing gear assembly. Re-use of the worn bolt and nut then allowed the hardware to fail under load during taxi, resulting in collapse of the landing gear.

Text from the NTSB. Open the NTSB docket for ANC25LA030 for the full record.