Piper PA-28-140 N1695H accident near Acton, California

Probable cause

The pilots inability to fully turn off the carburetor heat which resulted in a reduction of engine power and reduced climb performance. Contributing to the accident was the pilots delayed recovery from the simulated emergency landing.

NTSB analysis

The private pilot applicant and designated pilot examiner (DPE) were conducting a simulated engine failure exercise as part of the flight portion of a private pilot practical test. Once satisfied that the applicant would successfully complete an emergency landing, the DPE announced the end of the exercise and asked the applicant to initiate a go-around. The applicant advanced the throttle to full forward, turned the carburetor heat off, and pitched the airplane for 66 kts.

A few seconds later, the applicant informed the DPE that the airplane didn’t seem to be climbing, and the DPE checked the airplane’s climb configuration, confirming full throttle, full rich mixture, carburetor heat cold, and flaps up. Both pilots noted that the tachometer was displaying about 2000 rpm. During the simulated emergency descent and subsequent go-around, the airplane was flying toward rising terrain. The DPE attempted several shallow turns toward lower terrain; however, he could not turn without losing altitude, so did not turn away from the rising terrain. He identified a flat area on top of a ridge and executed an emergency landing on the ridgeline in heavy brush, about one mile from the go around initiation point.

Postaccident examination of the wreckage revealed that the carburetor heat control cable was improperly attached to the carburetor heat control arm, which restricted travel of the airbox heat door and the cabin-mounted carburetor heat control knob. The improper attachment restricted the heat door from closing fully in the carburetor heat OFF position but did not restrict the heat door from closing fully in the ON position. The inability to fully close the carburetor heat into the OFF position could have resulted in a reduction in engine power; however, an exact amount of engine rpm reduction could not be determined. Postaccident test run of the engine revealed that it produced full power and showed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The reason for the partial loss of engine power could not be determined.

Both pilots reported that they initiated the go-around while about 800 ft above ground level (agl); however, recorded flight data from the airplane’s avionics indicated that the airplane had descended to about 90 ft agl when the go-around was initiated. The airplane then attained an average climb rate of 310 ft per minute between the initiation of the go-around and the accident site. The elevation at the accident site was 381 ft higher than the elevation where the go-around was initiated. While flying into rising terrain, the airplane could have appeared to the pilots that it was not climbing, despite the documented climb rate. However, the partial loss of engine power likely prevented the airplane from outclimbing the rising terrain.

Text from the NTSB. Open the NTSB docket for WPR24LA117 for the full record.