Bad news from today's AOPA epilot news.  Thankfully, nobody was
seriously injured.

Mark S.


MISTRAL ENGINE PROTOTYPE CRASHES IN FLORIDA
A Piper Arrow powered by a prototype Mistral
( http://www.mistral-engines.com/ ) rotary aircraft engine crashed after the
engine lost power following takeoff from Palatka Municipal-Lt. Kay Larkin
Field in Florida. The owner, retired physician Stephen Roth of Deland, Fla.,
received minor injuries. The aircraft was used in 2004 for engine testing
( http://www.aopa.org/members/files/pilot/epilot/2004/040409epilot.html ) at
Embry Riddle Aeronautical University in Daytona Beach, Fla.


Dang!!! Real bad news. Glad to see your OK Steve.

I hope it was highly insured.

What date was that Mark? I do not have an AOPA password as I am not a
member.

As far as I can tell the NTSB has no record yet.
http://www.ntsb.gov/ntsb/AccList.asp?month=5&year=2008

What happened Francois?

BTW  Steve, I did not know you were a physician. I thought you were a Phd ex
Embry Riddle.


Paul Lamar ...No rotor no motor.

Here's the story in the Jacksonville News...with a rather fast video
(well, playing at a frame rate different than it was recorded, so it
LOOKS fast <G>)

www.news4jax.com/news/16474292/detail.html

Harley Dixon

Glad to see Steve is OK.
Can you capture that video as mpeg or wmv Harley?

I suspect somebody put in Jet A. The engine looks a lot
like a PT6. Near identical. Could be a cracked exhaust manifold.
Things to check.


Paul Lamar


Dear friends,

Mistral has indeed suffered a set-back with the destruction on Tuesday
of its test-bed Piper Arrow.  However, we at Mistral rejoice and thank
God that our colleague and friend Stephen Roth (aka "Doc") walked out of
the spectacular accident with only minor bruises and cuts.  He was back
at work the next day.

Mistral immediately dispatched to Florida Gordon Anderson, COO and CTO.
Gordon, Steve and a FAA investigator acting on behalf of the NTSB
examined on Thursday the wreckage as well as the complete and
uncompromised engine data log retrieved from the proprietary Digital
Engine Management (DEM) system.  It was soon evident that all engine
parameters were absolutely normal right down to the impact, with the
exception of abnormally low engine RPM.  The cause of the partial power
loss was found to be the failure of the internals of the exhaust
silencer, reducing the effective exhaust area by approximately 75%.

This particular silencer was a temporary and experimental solution,
built in SS 321 and with 169.7 service hours.  Nearly 100% of these
hours were done at maximum available power or close to it.   Mistral
is precisely finalizing the design and testing of a silencer
specifically designed for the frequency spectrum of the rotary, as well
as for its particularly high EGTs.

We shall soon publish on our website a white paper on exhaust systems
for rotary aircraft.  From our experience with our inconel primary
intake manifold which is almost like new (except of course for impact
damage) after ~430 hours in service, and from the present unfortunate
event, we can highly recommend the investment of a few hundred dollars
additional into an inconel exhaust.  Should your particular exhaust be
made of another, less temperature-resistant material, be sure to
regularly inspect it.

A more thorough report of the accident and of its cause will be posted
on our web site later today.

Francois

PS:  the airplane was very well insured and we are already in the
process of replacing it.  However, no more rides for a few months, sorry
guys! ;-)


Thanks for the report Francois.
I suspected it had something to do with the exhaust.
Were exactly did it crack first? Here are some pictures from March 2006.
Please
mark them up and send them back so we can learn from this incident.

Thanks

Paul Lamar ...No rotor no motor.

Paul,

The Mistral-designed double-walled PRIMARY EXHAUST MANIFOLD shown in
your pictures was like new (TTSN 341 hours) except for some impact
damage to the outer shell.  The internal shell is made of inconel.

It is the under-the-belly muffler, an off-the-shelf product in SS 321
that we bought from a Florida-based company manufacturing aviation
mufflers which failed.  Report and pictures on our website sometimes
next week after Gordon is back from Florida.

Francois

Ah so. Thanks Francois. I can believe it. Most people underestimate the
energy in the rotary exhaust both heat and kinetic energy.
There is a supersonic shock wave out of the peripheral port exhaust.
If a way can be found, using turbo compounding, to harness this incredible
energy, the rotary will prove to be THE most efficient internal combustion
engine of all. No exhaust valves to sap the energy.