The pilot was en route to his home airport when the Zenith CH750’s engine lost all power.
He set up for a forced landing to a plowed field near Montrose, Colorado, and attempted to restart the engine. The engine restarted momentarily, but then lost power again.
During the forced landing, the airplane’s main landing gear hit an irrigation ditch and the airplane nosed over and came to rest inverted.
The airplane sustained substantial damage to the left wing, fuselage, vertical stabilizer, and rudder, while the pilot sustained minor injuries.
A mechanic who examined the airplane and engine after the accident confirmed continuity of the engine’s rotating components, fuel distribution throughout the engine, integrity of the ignition system, and found no evidence of any pre-accident mechanical failures or malfunctions with the airplane’s engine that would have precluded normal operation.
The pilot reported that before the flight, the airplane was parked on the airport ramp and the outside air temperature was near 100°F. About noon, when he went to start the airplane, the engine would not start.
The pilot hangared the airplane so the engine could cool down and about an hour and a half later, he started the airplane and took off.
The pilot reported that he was about halfway home when the power loss occurred.
The pilot also reported that the airplane had a history of vapor lock occurrences in hot weather conditions and that he thought the engine’s power loss was due to vapor lock. The loss of engine power was consistent with a fuel vapor lock occurrence.
Probable Cause: The loss of engine power due to fuel vapor lock.
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This June 2021 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
“The pilot also reported that the airplane had a history of vapor lock occurrences in hot weather conditions and that he thought the engine’s power loss was due to vapor lock.”
Why would anyone fly an airplane with a known discrepancy when that defect could result in an off-field event?
I don’t find this report to be the NTSBs best. I could not find mention of the engine and/or fuel used. Maybe I missed it since someone here mentioned the engine and fuel used. But the conclusion that the root cause of the crash was caused by vapor lock seems premature and doesn’t meet my criteria of Root Cause.
My airplane has a Rotax 912 and it does occasionally suffer from vapor lock problems, in the ground only if I forget to run the electric fuel pump, mostly because of the shitty unleaded fuel we have to put on these engines here in the US but Rotax engines come standard with a fuel return port (that must be used per it’s install manual) and that eliminates the problem since you have cold fuel recirculating through the system at all times (if setup right). Not having insulation in the fuel lines is also a bad idea if you use auto fuel. In my airplane it is a mandatory SB to install them. Maybe here we could say incorrect engine install was the root cause of this accident. There is mention of low fuel on one side, could this have been a fuel starvation/sloshing problem? My point is that vapor lock is not a proper root cause, just a consequence of something else that was not OK particularly if the airplane had a history of vapor lock issues.
I think that the NTSB new recruits need a bit of supervision.
Best,
Chris
Reading the pilot statements, it was 100 degrees at the 5,800 ft alt airport, and the experimental engine did not have any insulation/firesleeve on the fuel line that was in the engine compartment.
Another pilot with the same UL power engine reported no problems.
So, not a fuel or engine design problem.
BTW, I experienced a similar problem, the engine momentarily stumbled, climbing out of So. Lake Tahoe on a warm day , as I reached 10,000 ft. Afterward I calculated that the fuel vapor pressure, [ 100LL], matched the airpressure at 10,000 ft.
Love to know how you got this. It was what I suspected based on heat issues with a ’59 Vauxhall some years ago. The fuel line needed to be shielded from heat sources and/or re-routed away from same. (I read the referenced NTSB report, and didn’t see any reference(s) to shielding the fuel line, etc.)
I looked up the tail number on the FAA registry website.
Bet he was burning auto gas.
Yet another primitive deadly problem lurking in GA engines. My grandfather’s 1939 Chevy suffered from vapor lock on the way to the Jersey Shore from Philly on hot days. Somehow the vehicle mfrs overcame this condition, but alas, not the plane engine mfrs. Just pathetic.