ASN Wikibase Occurrence # 281840
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| Date: | Sunday 30 May 2021 |
| Time: | 09:55 LT |
| Type: | Piper J-4A Cub Coupe |
| Owner/operator: | private |
| Registration: | N8501Z |
| MSN: | 4-1231 |
| Year of manufacture: | 1940 |
| Total airframe hrs: | 1653 hours |
| Engine model: | Continental C85-12F |
| Fatalities: | Fatalities: 0 / Occupants: 1 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Omaha, Nebraska -
 United States of America
|
| Phase: | Take off |
| Nature: | Private |
| Departure airport: | Omaha, NE |
| Omaha, NE | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
During takeoff, the airplane traveled about three-quarters of the way down the runway and climbed to about 300 ft above ground level. The engine sputtered once and stopped producing power. The pilot switched the fuel selector from the forward fuel tank to the auxiliary fuel tank and unsuccessfully tried to restart the engine. The pilot maneuvered the airplane for a forced landing, and the airplane impacted the ground. The pilot reported that fuel was pouring into the cockpit after the airplane came to rest, and he quickly exited the airplane. The airplane sustained substantial damage to both wings and the fuselage.
A postaccident examination revealed that the forward fuel tank cap was not the correct part for the airplane; the cap had an unknown part number etched on it with no manufacturer name displayed. The fuel tank cap appeared to be manufactured with a single vent hole and was equipped with two worn gaskets stacked under the cap. The lower gasket had multiple visible cracks present on both sides of it. The upper gasket was wrinkled and was displaced toward the vent hole, which blocked the venting capability of the fuel tank. For the accident model airplane, the sole source of venting for the forward fuel tank was through a vented fuel tank cap.
The pilot reported that the forward fuel tank cap was on the airplane when he purchased it several years ago. The pilot did not have any knowledge of the origin or the background of the forward fuel tank cap.
It is likely the engine sustained fuel starvation during the takeoff due to blockage of the forward fuel tank cap vent hole. Based on the available evidence, it could not be determined when the vent hole became blocked. The accident occurred 39 days and 2.3 flight hours after the most recent annual inspection. During the inspection, the mechanic should have observed the multiple visible cracks present on both sides of the lower gasket in the fuel tank cap. Further, during the preflight inspection, the pilot should have observed the multiple visible cracks present on both sides of the lower gasket in the fuel tank cap. Had the deficiencies with the fuel tank cap gasket been observed during the annual inspection or preflight, it is likely the fuel tank cap would have been replaced.
Probable Cause: A total loss of engine power due to a blocked fuel tank cap vent hole, which resulted in fuel starvation. Contributing to the accident was the mechanic's and the pilot's inadequate inspections of the fuel tank cap.
Accident investigation:
 |
|
Sources:
NTSB CEN21LA242
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 21-Aug-2022 18:57 | ASN Update Bot | Added |
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