Cessna 172P N65698 accident near Eagle River, Alaska

Probable cause

An inflight collision with terrain under unknown circumstances. Contributing to the delayed rescue response was the failure of the emergency locator transmitter (ELT) to activate as designed, and the mechanic’s failure to ensure the correct ELT was installed and all applicable airworthiness directives complied with in accordance with federal regulations.

NTSB analysis

The pilot and flight instructor departed on a 2-hour discovery flight and did not return. The wreckage was subsequently located nearly 9 hours after the airplane’s scheduled return time in an area of rocky, mountainous terrain. The airplane sustained substantial damage to the fuselage and left wing.

No pre-accident engine or airframe mechanical malfunctions or anomalies were found that would have precluded normal operation. The carburetor “heat valve” was observed in the ON/HOT position, and was captured in this position due to the deformation of the surrounding heat box material, consistent with the absorption of impact energy. The propeller remained attached at the crankshaft. Each blade was missing about 2 inches of the blade tip and exhibited leading-edge gouging and torsional twisting, chordwise striations across the cambered surface, and trailing edge “S” bending, all of which is consistent with rotation under power at the time of impact.

The temperature and dewpoint in the area of the accident site around the time of the accident were consistent with a moderate risk of serious carburetor icing at cruise power settings and severe icing at glide power settings.

Although the airplane’s emergency locator transmitter (ELT) emitted a signal the day after the accident, which was detected by search and rescue personnel, no signal was detected immediately after the accident. During postaccident examination of the ELT, when in the ON mode, the ELT activated and transmitted on both 121.5 and 406MHz. When tested in the ARMED mode, the ELT transmitted only once out of numerous tests.

The ELT installed in the airplane was an AmeriKing AK-451 ELT that was the subject of a Federal Aviation Administration (FAA) airworthiness directive (AD) which required annual testing as a result of an unapproved parts investigation. The AD was prompted by multiple reports of ELT failures and a report of noncompliance to quality standards and manufacturer processes. The AD further stated that failure to adhere to the standards and processes could result in ELTs that would not function, similar to the circumstances in this accident.

A review of the airplane’s maintenance records revealed an entry showing compliance with the AD about 19 months before the accident. An entry with the same date indicated that the ELT was replaced with a different make and model. An entry dated about 6 months before the accident indicated that the ELT was tested in accordance with 91.207(d) and the AD compliance sheet was up-to-date.

Since the maintenance records indicated that the AD-affected ELT had been removed and replaced with a unit not affected by the AD, the required testing was likely not accomplished; therefore, the faults with the ELT were not discovered. Had the ELT functioned as designed, emergency personnel would have been alerted to the accident, even if the company did not report it overdue. Similarly, had the AD-affected ELT been removed and replaced with a functional unit as was noted in the maintenance records, the search and rescue response likely would have been faster; however, whether faster location of the wreckage would have prevented a fatal outcome could not be determined.

Text from the NTSB. Open the NTSB docket for ANC21FA065 for the full record.