Cessna 120 N4237N

Summary

On 21 August 2019 at about 18:50 local time, a Cessna 120 registered N4237N was involved in an accident near Livermore, California, United States. One person was on board and one was seriously injured. The aircraft was substantially damaged. The NTSB has published a probable cause for this accident; it is quoted in full below.

Date

21 August 2019 at 18:50

Classification

Accident

Location

Livermore, California, United States

Nearest airport

Livermore Municipal Airport (LVK)

Coordinates

37.6894, -121.8189

Aircraft

Cessna 120

Registration

N4237N

Category

Airplane

Year built

1947

Engines

1

Operator

Not recorded

Operating rule

Part 91: General Aviation

Purpose of flight

Personal

Phase of flight

Not recorded

Route

Livermore → Unknown

Aircraft damage

Substantial

Weather

VMC

Light

Day

NTSB number

WPR19LA233

1 person was seriously injured.

A partial loss of engine power due to fouled spark plugs in the No. 4 cylinder. Contributing to the accident was the pilot’s exceedance of the airplane’s critical angle of attack and a subsequent loss of control during the initial climb.

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

Read the full NTSB narrative

The accident flight was the first flight following the airplane’s annual inspection. The pilot reported that, during the takeoff roll, the airplane took longer than expected to accelerate, and after becoming airborne, did not seem to be producing full power. Witnesses stated that the airplane made a sharp left turn about 100 feet above the ground and the left wing impacted the ground; the airplane cartwheeled before coming to rest, resulting in substantial damage. A postaccident examination revealed that the upper and lower spark plugs from the No. 4 cylinder and the lower spark plug from the No. 3 cylinder exhibited oil and soot bridging the gap between the electrodes. All other spark plugs exhibited black soot build-up on the electrodes and insulators. The reason for the fouled spark plugs was not determined based on the examination. The mechanic who completed the annual inspection reported that he cleaned, gapped, and functionally tested all of the spark plugs. After the inspection, he conducted an engine run-up and found that one of the plugs had become fouled. He cleaned the plugs a second time and reinstalled them using new gaskets. He ran the engine up a second time, and it ran smoothly. Based on the condition of the No. 4 cylinder spark plugs, it is likely that the engine was not producing nominal power and that its takeoff and climb performance was degraded. The witness observations of a steep left turn and descent to impact is consistent with an aerodynamic stall due to the pilot exceeding the airplane’s critical angle of attack during the initial climb.

Quoted verbatim from the NTSB record.