ASN Wikibase Occurrence # 205787
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| Date: | Sunday 15 October 2017 |
| Time: | 10:00 |
| Type: | Turbine Cubs PA-18 Super Cub |
| Owner/operator: | Private |
| Registration: | N181TJ |
| MSN: | TC0705014 |
| Year of manufacture: | 2009 |
| Total airframe hrs: | 379 hours |
| Engine model: | Lycoming O-360 |
| Fatalities: | Fatalities: 0 / Occupants: 2 |
| Aircraft damage: | Substantial |
| Category: | Accident |
| Location: | Skull Valley, UT -
 United States of America
|
| Phase: | En route |
| Nature: | Private |
| Departure airport: | West Jordan, UT (U42) |
| West Jordan, UT (U42) | |
| Investigating agency: | NTSB |
| Confidence Rating: |  Accident investigation report completed and information captured |
The private pilot reported that he had just completed a low-altitude pass to observe an object on the ground and that, as he applied power to initiate a climb, the engine “stumbled slightly and seemed to hesitate.” The pilot applied carburetor heat after noting the outside air temperature because he thought that carburetor ice might have accumulated. The pilot then applied full power, and the engine again seemed to hesitate, so he decided to initiate a precautionary landing to an open salt flat area. Shortly after touchdown, the airplane nosed over. The pilot reported that he used cabin heat during the entire flight.
The left and right brake master cylinders remained secured to their respective mounts. When actuated by hand, the right brake pedal needed minimal input to actuate the brake; however, the left brake pedal needed a significant amount of movement to actuate the brake. Both the left and right main landing gear wheels moved unrestrictedly. During postaccident examination of the recovered wreckage, heat was applied to the right brake master cylinder for about 25 minutes, and the brake engaged, restricting movement of the wheel. The application of heat to the left brake master cylinder resulted in no change. The brake fluid reservoir contained residual hydraulic fluid, most of which likely drained through the vent hole in the cap after the accident sequence. It is likely that the pilot’s use of cabin heat throughout the flight resulted in the master cylinders and hydraulic fluid reservoir heating to the point that it allowed the hydraulic fluid to expand and subsequently actuate the brakes and led to the airplane nosing over during the landing. It is possible that the hydraulic reservoir had too much fluid in it before impact, which could have led to such an outcome, but given the fluid leaked out postaccident, this could not be determined with certainty.
Postaccident examination of the engine revealed that one of the two carburetor temperature probe wires was separated from an electrical connector, consistent with a bad crimp. The disconnected wire likely prevented the carburetor air temperature from being displayed on the airplane’s avionics panel. However, this would not have affected the outcome of the accident. The atmospheric conditions in the area at the time of the accident were conducive to the formation of carburetor ice at glide and cruise power. It is likely that the hesitation in the engine performance reported by the pilot was the initial stages of carburetor ice formation, which precipitated the off-airport precautionary landing.
Probable Cause: The uncommanded activation of the brakes due to the expansion of the hydraulic fluid within the hydraulic reservoir and master cylinders, which resulted from heat produced by using the cabin heat throughout the flight and resulted in the airplane nosing over during an off-airport precautionary landing.
Accident investigation:
 |
|
Sources:
NTSB
Location
Revision history:
| Date/time | Contributor | Updates |
|---|---|---|
| 07-Feb-2018 13:50 | ASN Update Bot | Added |
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