Pilot Debrief

CONSOLIDATED AERONAUTICS INC. LAKE LA-4-200 near Twentynine Palms, CA — 2021-04-21

Final reportWPR21LA171
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Date
2021-04-21
Location
Twentynine Palms, CA, USA
Airport
TNP
Aircraft
CONSOLIDATED AERONAUTICS INC. LAKE LA-4-200
Registration
N2989P
Category
Airplane
Highest injury
Minor
Fatalities
0
Phase of flight
Initial climb

Probable cause

A partial loss of engine power due to inadequate ignition from cracked spark plugs and a failed magneto.

NTSB narrative

The pilot had recently purchased the airplane and was transporting it to his home airport. During the cross-country flight, the pilot stopped to refuel the airplane. During departure, the airplane climbed to an altitude of about 200 ft above ground level, at which point the engine lost partial power and was unable to maintain altitude. The pilot elected to perform an emergency off-airport landing, and the airplane touched down on desert terrain. During the landing, the airplane collided with a sign and nosed over, coming to rest inverted. The airplane had undergone a pre-buy and an annual inspection about 10 flight hours before the accident. The pilot stated that, on the day before the accident, he flight tested the airplane, during which time the manual turbocharger went into overboost for “a second” before he pulled the power back. A postaccident examination revealed that several ceramic cores of the spark plugs were cracked. The combustion chambers were free from deposits, consistent with a preignition or detonation event. It is unknown if the overboost event that the pilot described resulted in this damage. The magnetos, while still installed on the engine, did not produce a consistent spark, and their timing could not be determined. The magnetos were then removed from the engine. The right magneto was functionally tested and operated normally. The left magneto capacitor lead insulation had previously been cut, exposing the center conductor wire, consistent with improper assembly. The contact point tungsten faces were both corroded and exhibited an oxide crust on the external surfaces of the tungsten. A functional test, revealed the left magneto would not produce spark at different rpms. The left magneto was likely not operating during the accident takeoff, which, along with the cracked spark plugs, would have resulted in a partial loss of engine power.

Analysis

Primary failure mode
Engine power loss
First missed decision gate
Pilot could have conducted a thorough preflight inspection for engine issues.

NTSB coding

Evidence available

  • 8 docket documents
View NTSB final reportView NTSB docket

Docket documents8

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