Sonex down at Osh. Two dead..R.I.P.

[rwanttaja]

NTSB Final Report is out.

http://app.ntsb.gov/pdfgenerator/Rep...Final&IType=FA

Ron Wanttaja

[1600vw]

It looks like the turbo could have been an issue or caused this. So sad. They also say if just maybe they would have used the complete runway we would not be talking about this. Again very sad. Thanks for the update Ron.

[Joda]

It looks like the turbo could have been an issue or caused this. So sad. They also say if just maybe they would have used the complete runway we would not be talking about this. Again very sad. Thanks for the update Ron.

For those of you who don't know, I worked for Sonex during the time of this accident. I had just returned from 25 hours of cross country in the accident airplane. I flew it down to Florida for the Sebring and Sun N Fun events. The airplane had been flown only one other time since returning from Sun N Fun that spring. I helped Jeremy and Mike push the airplane out before the accident flight. I personally checked the oil and the fuel, and watched them taxi out and do the run-up. All was normal at that time.

I did not witness the takeoff, and it seems that nobody else did either. No eye witnesses have ever come forward at any rate. Jeremy was notorious for doing that intersection takeoff when the wind was from the east, as it was a long taxi from Sonex (on the very east side of the airport at OSH) to the far end of Runway 09. The intersection that they departed from is almost exactly half-way down the 6000 ft+ runway.

To get to my point, I was also the Sonex factory representative who assisted the FAA and NTSB with their on-site investigation the day after the accident. I personally turned the wrenches as we carefully evaluated the impact-damaged engine. One of the things we focused on was the turbo. The turbo housing was fractured on the compressor side, forcing the compressor housing to physically jam the turbine wheel. As soon as we dismantled the intake manifold to the point that this pressure was released, the turbine wheels and shaft turned freely. There was no failure of the turbo that was apparent other than the physical impact damage. The wording of the factual and final reports don't adequately illustrate this, which Sonex is disputing. Hopefully the report will be corrected to reflect what we actually found on-site.

Unfortunately, we will never know what actually happened that day. There are a few mysteries that we will never solve, but the lesson that can be learned (and it's not a new one) is that it is a mistake to leave usable runway behind you, regardless of what you "think" you'll need. Take that lesson to heart, and fly safely.

[martymayes]

I did not witness the takeoff, and it seems that nobody else did either.

Joe, do you know how the NTSB was able to determine takeoff ground run was ~1700 feet?

[Joda]

Joe, do you know how the NTSB was able to determine takeoff ground run was ~1700 feet?

There was apparently some GPS data that they were able to recover from the data card on the MGL instrument that was installed in the aircraft. Unfortunately, the instrument either didn't record any of the engine parameters, or the data was lost during the impact.

I question that statement as well, as that would be far beyond normal for a Sonex, especially the turbo, even with two people aboard. I had quite a bit of time in that aircraft, and I know it's takeoff performance was very good.

It's unfortunate that there were no eye witnesses that could verify what actually occurred during the takeoff run. That is just one of the mysteries that we'll probably never have an answer to.

[martymayes]

Thanks -

[rwanttaja]

Joe, I appreciate how hard this must be. There are two sections of the NTSB report where, perhaps, you might provide some insight.

From the wreckage and impact section:

The engine's turbocharger could not be rotated by hand. Disassembly of the turbo found static marks corresponding to compressor blades without any smearing or deformation of the blades. Disassembly of the turbo found that the bearing housing was cracked.

To a layman like myself, the "without any smearing or deformation" implies it was not turning at impact. Test and Research section seems to echo this, but there is mention of damage which might imply it was turning (I underlined that portion):

Impact marks were located at the upper and aft portions of the compressor housing surface. The impact marks were relatively distinct and discrete consistent with little relative motion between the blades and the housing at the time of impact. Corresponding blade damage was observed on the compressor wheel. Six of the compressor blades had radial cracks that emanated inward from the outer edges. The cracks were all associated with deformation of the blade where the airfoils between the cracks and the blade tip were bent toward the pressure face of the blade (toward the direction of rotation). Both the compressor wheel and turbine wheel turned together freely within the center housing when either wheel was rotated by hand.

My layman's interpretation of this is that the lack of smearing/little relative motion was a result of the engine failing for other reasons (e.g., if the engine is windmilling, the turbo's not spinning quickly). The bent blade tips were a reflection of the idle rotation. This, the fact that everything turned freely after impact distortion was relieved, indicates to me that the turbo wasn't directly a cause.

Ron Wanttaja

[Joda]

Ron,

Your interpretation is exactly correct in my view. It does appear that the turbo shaft wasn't turning, or was turning very little, at the time of impact. It is also true that, as I mentioned before, once the impact damage was relieved, the turbo shaft turned freely. There was no obvious evidence of any sort of in-flight failure of the turbo. Whatever happened, there was no tell-tale evidence that could be discerned by after-accident inspection of the engine.

Joe