Final NTSB Probable Causes

[RyanB]

So Im sure most of you have came across the video of the Bonanza taking off from Fairbanks, AK and lands in a field at the end of the runway after losing power. If you have not here is a link.

https://www.youtube.com/watch?v=94IURXCoY5A

The NTSB released the probable cause they determined it :The total loss of engine power reason that could not be determined because postaccident examination and test run did not reveal any anomalies that would have precluded normal operation.

Just curious as to how this happens? The pilot lost power but the NTSB is not able to find any reasons for it, I've seen this on other accidents as well, the engine had trouble and quit but they did not find any reasons for it too. Any thoughts?

NTSB: http://www.ntsb.gov/_layouts/ntsb.aviation/brief.aspx?ev_id=20120727X40845&key=1

 

[txflyer]

Vapor lock then when the engine cools down it dissapears or either water in fuel just enough to kill it but not enough to show up afterwards?

I'm guessing here ...

 

[MauleSkinner]

Another possibility would be a fuel selector on an empty tank until after the landing...

not that I have any actual reason to believe that's the case here. This one was obviously due to all the cameras on the airplane.

 

[tmyers]

We will likely never know IIRC the pilot was killed in. baron about a year after this accident scud running through one of the passes in the Alaskan range near denali

 

[wanttaja]

It actually happens surprisingly often...about 5% of accidents are attributed to engine failure of undetermined cause. A few are totals that don't leave enough evidence, but most aren't. On some, like this one, the engine starts successfully afterwards and runs normally.

It does vary by aircraft type; Cessna 172s see about 3.5% of the cases, fixed-gear Cherokees about 6%, Cessna 210s around 11%. The latter could be due to the aircraft hitting harder, though.

Homebuilts run about 9%.

My assumption is that these are mostly vapor lock, carb ice, or a fuel-feed problem that the pilot either didn't realize or doesn't admit to.

Ron Wanttaja

 

[Graueradler]

I.ve experienced two intermittent engine problems that would show up on one engine run and not the next. Physical conditions were there but might or might not have been found after an accident. One was a mud dauber nest that had migrated from the carb heat muff across the flapper vlve to the normal induction side of the flapper valve. At WOT on one run, it might get sucked up into the carb throat, on the next run - maybe not. Never happened at pre-flight check RPM. The other was a piece of failed muffler internals sometimes moving over the muffler outlet inspite of a bail that is supposed to prevent that.

 

[MauleSkinner]

My assumption is that these are mostly vapor lock, carb ice, or a fuel-feed problem that the pilot either didn't realize or doesn't admit to.

Ron Wanttaja

"Fuel feed" problems can be related to numerous things as well...I know of one instance where debris in the fuel tank vent allowed the engine to run for a solid hour-long flight, but the vacuum in the tank caused a vapor lock when the power was reduced to idle for landing.

The go-around didn't last long.

 

[acrophile]

[]I[']m sure most of you have c[o]me across the video of the Bonanza taking off from Fairbanks, AK and land[ing] in a field at the end of the runway after losing power. [...]

The NTSB released the probable cause they determined[: t]he total loss of engine power [for a] reason that could not be determined because postaccident examination and test run did not reveal any anomalies that would have precluded normal operation.

Just curious as to how this happens[.] The pilot lost power but the NTSB is not able to find any reasons for it[.] I've seen this on other accidents as well[:] the engine had trouble and quit but they did not find any reasons for it too.

I find it more impressive that evidence of the cause of engine failure sometimes does survive a mangled wreckage than that it sometimes does not.

 

[Geico266]

Good stuff Ron, thanks.