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I would like to respectfully disagree with anything related to the turbo based on my interpretation of the report. As a turbo owner, I am going to stand along side the factory that was closely involved in the investigation. If they felt the turbo was an issue and may have had any factor in the crash, they would have an SB out. The issues with the turbo today did not appear present in the accident. I have 100% faith in my turbo which has flown me over 7,000nm in the past 7 months.

The turbine blades were spinning at time of impact because there were radial cracks emanating inward, bent blade tips corresponding to the direction of rotation, and the compressor wheel and turbine wheel turned together freely.

For me personally, having lost a two friends a few years ago at the end of my home base runway (an accident that was avoidable), I think it is a good time for all of us to remember what we all learned in flight school:

1) Always use a comprehensive check list for every stage of pre-flight and flight
2) Take the extra taxi time and use the full length of the runway. Then fly runway heading until a minimum safe altitude has be obtained
3) Always climb out at the appropriate Vx or Vy, never deviate for with the "high speed, high angle departures" at the very end of the runway

I know I am far from a perfect pilot, but following those 3 rules has significantly improved my flying proficiency and safety. I have seen a lot of home built planes flying without good checklists, abbreviated departure patterns and downright scary climbing turns.

Fly safe and have a wonderful holiday season.

One portion of the report says:

A company employee reported he experienced a degraded turbocharger system a few weeks prior to the engine functional test. During that flight, the airplane would fly level, but could not maintain a positive climb. He reported that after the flight, the turbo was examined and found to not be completely seized, but the piston ring-type seal on the shaft connecting the compressor and turbine wheels had partially seized and interfered with the shaft's ability to rotate. An examination of the accident turbocharger did not find a similar signature. Replicating a seized turbocharger during engine operation was not possible.

The report doesn't indicate if this performance was with the plane heavy or if it was light.
If the Aerovee Turbo were modified to allow manual opening of the wastegate (reducing exhaust backpressure in case of a seized turbine), would this likely improve performance with a turbo that has a seized/damaged turbine/compressor? Or, in a case like this, does the reduction in performance largely result from reduction in available intake flow past/through the compressor?

The report states an employee had problems with the turbo. It says they had a really long take off roll and poor climb rate. Sonex didn't provide data on the mfg of the accident turbo. The example one didn't have any mfg data and the accident wastegate had the mfg and serial number ground off. The turbo could not be rotated by hand. NTSB inspection shows little movement of the compressor blades in the housing at time of impact. There is a current SB regarding problems with turbos, yet you want to disagree that it may have been the turbo?

Not saying it was or was not the turbo, but to outright say it was nothing to do with it when looking at all of that info seems like wearing blinders. The majority of the report focuses on the turbo, so I would venture a guess that the FAA and NTSB thinks it played a part in it more than something else.

Forgive me here JJ but I'm going to have to respectfully disagree with you about the turbo.

There is, in fact, a SB out on the turbo. Whether anything in the accident had anything to do with it is pure speculation but it does exist.

Also, the report suggests the engine was not running at the time of impact. Why would the turbo be spinning if the engine wasn't running? "Static" marks imply no movement by definition. Also, the impeller would not spin at the accident site it wasn't until the folks in D.C. messed with it that it started spinning where "the impact marks were relatively distinct and discrete consistent with little relative motion". Now that doesn't say the turbo seized but suggests it was not moving or moving very little at the time of impact. The impact itself could've caused all the damage to the turbo.

The rest of what you said I totally agree with.

Fastcapy wrote:The turbo could not be rotated by hand. NTSB inspection shows little movement of the compressor blades in the housing at time of impact. There is a current SB regarding problems with turbos, yet you want to disagree that it may have been the turbo?

It is my personal opinion. I do not believe the turbo had an impact on the flight operation of the aircraft. Disassembly of the turbo found that the bearing housing was cracked which is why it could not spin freely by hand. The engine was separated from the aircraft, and it is probable the turbo sustained damage at the time of impact. Upon inspection, the notes indicate the turbo was free to spin.

The current SB with the turbo has not had anything to do with cracking of bearing housings. It has to do with Choking and degraded performance, not fracturing of turbine blades, shafts or bearing housings.

I personally do not believe the two are related and know a lot of people are skeptical right now of the turbo, people are steering away from it, etc. I respect their choices and respect their posts. But, I can also be an advocate for the turbo just as they can be of their opinions. It is all just opinion.

I just think the the turbo is getting an unfair assessment and wanted to share my personal point of view. Everyone points to the turbo, but there are a lot of other factors in that report which had significant contribution to the accident.

A lot of threads have been posted against the turbo. I like to post some that shows it can be a great platform, especially for those considering that as their engine choice.

You are entitled to your opinion.

However, you say the damage was caused by the impact. Maybe, but the report seems to indicate otherwise. Either way, lets say it was all impact related. Well, you even say the SB is for coking and degraded performance. So a 1700ft takeoff roll, and minimal climb performance could very well indicate that it wasn't working correctly and could have had the same issues the SB was issued for.

But, then again, the factory Waiex had the same issues as well without the turbo when it crashed in Fond Du Lac, so yes you may be right, maybe it is an Aeroinjector or Aerovee problem. Either way I know I would not feel to comfortable behind a turbo aerovee with an aeroinjector. To each their own though.

Thank you guys for keeping things civil with respect to Jeremy and Mike. Regardless of the cause, I know we all agree this is a very terrible tragedy.

One item I'd like to add if I read the report properly; it states...

"company employee reported he experienced a degraded turbocharger system a few weeks prior to the engine functional test."

I believe this may have been on Red One which was flying during the accident analysis and subsequent investigation. Remember, Red One didn't fly until 1 1/2 years after N123SX's accident. The "degraded turbocharger" issue would certainly be a culprit in the issuance of the current SB and may or may not have anything to do with the SA's accident. But, in the end, I believe it's two very different situations.

Just asking to those who are smarter and I (pretty much all of you), is this the final report or will the NTSB follow with a "Probable Cause" statement?

Thanks everyone!

MichaelFarley56 wrote:Just asking to those who are smarter and I (pretty much all of you), is this the final report or will the NTSB follow with a "Probable Cause" statement?

That would be nice,
I don't understand why the NTSB often remains so ambiguous (for lack of a better word) about the cause of the accident, even in their "final" report.
Remember the final report of N75654, even though pretty much the whole report hinted strongly towards issues with the design standards of the Y tail spar, that report also never explicitly stated this to be the cause of the in flight break-up.
In this report they also seem to spend a lot of focus on one particular aspect without explicitly stating a problem, it's not like they're just saying "loss of power because of unknown factors" or something like that which you read in most reports.

I didn't see any mention of testing the magnetos. My thinking was that if you had two similar degradation of power incidents one on a turbo powered plane and the other on a standard non turbo engine and there seems to be no other problems with the engine rotating freely or the fuel was proven to be reaching the cylinders, then I'd suspect something in the ignition system. This is just me thinking out loud and I have practically no experience.

This was the factual report. It does not specify the cause, only releases the facts they have gathered to this point. Following NTSB reports for a few years, it goes preliminary, factual, final. Usually they skip the factual and straight to final if they know the cause. From what I've read so far, if they can't prove the turbo was the cause, they will find the root cause as engine failure due to unknown factors. The presence of smoke puffs is interesting and the investigators trying to recreate them on the test stand. Didn't think about a smoke system, but you'd think they would have mentioned that. Also, seems the engine wasn't turning at impact which kinda rules out the turbo being a problem. Even if it seized, the engine would still be turning.