Grumman American Avn. Corp. AA5A N26387 accident near Redstone Arsenal, Alabama

Probable cause

The separation of the clamp assembly securing the throttle control cable outer housing, which resulted in the pilot’s inability to control the throttle.

NTSB analysis

After takeoff the pilot performed a practice RNAV approach, then climbed to 3,500 ft mean sea level en route to another airport. While at altitude the pilot attempted to adjust the engine power settings, but the engine power “went to low power and was not responding to throttle control inputs.” He declared an emergency and after realizing that the flight was unable to reach a nearby airport, he selected a nearby field with a paved road. After landing on the road, he applied maximum braking, but the left wing impacted a metal pole, resulting in substantial damage to the leading edge of the wing.

Postaccident inspection of the engine compartment revealed the throttle control cable assembly remained attached to the throttle control lever of the fuel injection servo, but the outer cable assembly was not secured in the engine compartment. Thus, movement of the throttle control in the cockpit did not result in movement of the throttle control lever. A clamp, shim, two screws, and two metal self-locking nuts that secured the outer cable assembly were not located, but a washer was found loose in the engine compartment.

The throttle cable was replaced at the airplane’s last annual inspection 8 months earlier; the airplane had been operated for about 15 hours since the annual inspection. Although it is unlikely that the screws used to secure the cable would have sheared or failed, they were not located. Thus, the reason for the outer cable clamping hardware to separate could not be determined from the available evidence.

Text from the NTSB. Open the NTSB docket for ERA23LA286 for the full record.