Cessna 172K N79944

Summary

On 24 May 2002 at about 13:45 local time, a Cessna 172K registered N79944 was involved in an accident near Lake Thomas A., California, United States. 3 people were on board and one was seriously injured, 2 had minor injuries. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

24 May 2002 at 13:45

Classification

Accident

Location

Lake Thomas A., California, United States

Nearest airport

Reedley Municipal Airport (O32)

Coordinates

36.1164, -119.6810

Aircraft

Cessna 172K

Registration

N79944

Category

Airplane

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Reedley → Milford

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

LAX02LA172

1 person was seriously injured.

a partial loss of engine power due to the partial malfunction of the left magneto and leakage of the ignition leads for that magneto, due to inadequate maintenance inspections. Factors in the accident include the high density altitude, the maintenance personnel's failure to accomplish a service bulletin, and the effects of the pilot's manipulation of the mixture and carburetor heat controls.

Quoted verbatim from the NTSB record. This site does not paraphrase or interpret it.

Read the full NTSB narrative

The airplane experienced a partial loss of engine power and collided with a tree stump during a precautionary landing on a beach. While climbing through 9,000 feet mean sea level (msl) the pilot leaned the airplane by relying solely on the exhaust gas temperature gauge. When reaching about 9,500 feet msl, about 1,500 feet above ground level over mountainous terrain, the pilot reported that the engine lost partial power. The propeller continued to turn, and the tachometer showed about 2,450 to 2,500 rpm, but the engine failed to produce enough power to sustain level flight. The pilot adjusted the mixture control, while also turning the carburetor heat to the on position, and applying full throttle. The engine failed to respond and the pilot made an approach to a sandy beach. The pilot flared the airplane about 2 feet above ground level, and the left wing collided with a tree stump, veering the airplane to the right. The elevation at the crash site was about 7,600 feet msl. A post accident investigation revealed that the left magneto exhibited excessive play at the cam end (points) of the main shaft. The subject magneto was later functionally tested, which revealed an intermittent spark on ignition lead T1. According to Textron Lycoming Mandatory Service Bulletin 515 the magnetos must be inspected every 500 hours. At the time of the accident, the magneto had accumulated a total time in service of 1,540.23 hours, and there was no maintenance entry indicating that the Service Bulletin had been complied with. While post accident tests showed that the left magneto was working only on an intermittent basis, information provided by Lycoming suggests that in and of itself the complete loss of one magneto would only result in a 3 to 5 percent loss of power. It is likely that the combined effects of the magneto malfunction, the high density altitude, and the pilot's manipulation of the mixture and carburetor heat all played roles in the engine's decreased performance capability.

Quoted verbatim from the NTSB record.