North American AT-6D N29947 accident near Fredericksburg, Texas

Probable cause

A total loss of engine power due to a failure of the No. 1 cylinder.

NTSB analysis

The pilot stated that he completed a preflight inspection and engine run-up with no anomalies noted. During the initial climb after takeoff, immediately after retracting the landing gear, the pilot noticed white smoke from the engine cowling. A few seconds later, the engine “coughed loudly” and lost total power. The pilot landed the airplane on the remaining runway; however, the airplane exited the runway and collided with a runway light. resulting in substantial damage to the left wing and left aileron.

Federal Aviation Administration (FAA) inspectors completed an examination of the airplane and assisted the owner’s mechanics with removing the engine for transport. They discovered that the No. 1 cylinder was cracked around its circumference. They did not observe any other anomalies during the examination.

Postaccident engine examination confirmed that the No. 1 cylinder head fractured near the rear spark plug on the exhaust side. The mechanic noted it was likely that during the accident takeoff, the cylinder head separated due to pre-ignition or detonation stresses, which no longer allowed the push rods to operate the valves and resulted in a loss of engine power.

A recurring FAA airworthiness directive (AD) was applicable for this airplane and related to visual inspections to prevent cylinder head cracking. The AD was completed 164.7 flight hours before the accident and was due to be completed again in 85.3 hours.

Text from the NTSB. Open the NTSB docket for CEN22LA187 for the full record.