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David
Mistral had the test aircraft at Oshkosh one
year. They had a secondary muffler in addition to the mostly inconel
muffler of their own design. I was told, I believe it was the next year at
Oshkosh again, that the secondary muffler had choked up and caused the loss of
the aircraft.
Dean Van Winkle
RV-9A, 89 13B NA
----- Original Message -----
Sent: Sunday, March 20, 2011 10:26
PM
Subject: [FlyRotary] Re: Forced
Landing.
I also have had several mufflers fall apart in sort order, even with my
turbo, and I no longer use one. The mistral guys lost their
aircraft due to a clogged muffler (professionally custom made).
I did have a DNA muffler that did not fall apart (yet), but it REALLY
robbed my power. I was down about 20% in top end power so I removed
it. It nicely cut down on the pitch and didn't weigh alot, so I was
sorry to see it go.
A nice long straight pipe seems to do a pretty good job at cutting down
on the sound levels without much cost or risk of bringing down my plane.
I have been using that for the last couple hundred hours and don't expect that
I will ever change.
On Sun, Mar 20, 2011 at 6:37 PM, Mark Steitle <msteitle@gmail.com> wrote:
Bill,
The DNA (Dynamic Noise Attenuation) muffler is the only one I've used
that has not self-destructed in a matter of hours, except for the tangential
muffler which was too restrictive and caused other problems and gave poor
performance. (I should have listened to Lynn.) The DNA is not as
quiet as other mufflers, but it has worked for about 100 hours so far with
no sign of fatigue. Also, it has no packing to blow/burn out.
ANR headsets are a given.
Mark
Bobby,
That is an
excellent job of both flying and troubleshooting to discover the cause of
the problem. I am wondering why you have a muffler if you have a
turbo?
My Hushpower is
welded in and up inside the cowl. I would not be able to see inside
if or remove or replace it with the current setup. This incident has
really made me start to think about the muffler.. Thanks for the
great report!
Bill
B
From:
Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bobby J. Hughes
Sent:
Sunday, March 20, 2011 4:02 PM
To: Rotary motors in
aircraft
Subject:
[FlyRotary] Forced Landing.
Since it’s been so quiet lately.
I had a complete loss of engine power yesterday
during climb out from Tyler TX (KTYR). I had executed a Vx climb to see
you hot I could get the oil with the supplemental oil cool I recently
added. The engine was running but stopped making any power. I switch fuel
tanks, adjusted the mixture both directions, toggled the primary injector
switch for cold start and check my breakers. I did everything but switch
to the B controller. All the troubleshooting took place in about 10
seconds or less. At that time my AOA starting telling me “angle, angle,
push, push” . Glad I had the AOA as I’m not sure my attention was focused
on the right priorities. I told the tower I had an engine failure and was
landing. 35. Very happy this happened at an airport with three long
runways with different headings. I pointed the nose down and made a right
turn to the runway. The landing was downwind with 15 knot wind. I was too
fast and used all 3500ft I had left. I coasted onto a taxiway with the
engine idling very rough. I couldn’t make enough power to taxi. The FBO
was there within two minutes and towed me back to their hanger. At this
point I figured I had lost an apex seals. I pulled the prop through but
had good compression. I pulled the cowl and everything was in place. Up
until now I had remained very calm but that changed when I realized there
was no smoking gun. I checked my injector power connections at the
switches but everything seem good. The EC2 coil test worked but the
injector test did not. I attempted an engine start and it ran normally.
“What the h***” I later realized I had not activated the cold start switch
for the injector test. Injectors tested fine. I was at a complete loss as
what to look at next. I thought about a CAS intermediate failure but
nothing I could come up with fit the problem. After another five minute
full power run to 38”MP on both controllers I rolled the plane back into
the FBO’s hanger and took a break. So here I am 200 miles from home after
a forced landing and the plane is making full power as usual. Now the
nerves set in full force. It downed on me to check the muffler for
blockage. From what I could see with a flashlight the cone in my
HushpowerII was out of place. I dropped the muffler from the belly and
about a ½” cup of material came out. It was small pieces of mess from the
cone. About 1/3 of the entrance side cone was still intact but the rest
was gone. The internal steel support that forms the cone was still intact
but movable with a large screw driver. I knocked as much out as I could
and reinstalled the muffler. I was unable to knock out any of the mesh
that was still in place. I decided to conduct a flight test over the
airport for ten minutes. If all was good then I would head for home and
climb to 8500 for the trip back. The headwind at 8500 would add 20 minutes
to the flight unless I ran the engine above 30” MP. I didn’t think it was
a good time to stress the muffler any more than necessary. I took off and
climbed to 3000 ft on the B controller and circled for several laps. I
switched controllers, fuel, injector cold start, coils and everything was
normal. So I nervously departed for the 200 mile trip. I picked up flight
following and had the autopilot/ flight director take me home. I spent the
entire flight with the nearest airport active on my Advanced EFIS moving
map. It draws a line, gives a distance and runway lengths. I also check
airport information on my ipad and Foreflight. The flight was uneventful
but was the most stressful I have ever experienced.
I’m guessing the muffler internals came loose and
slid rearward trapping all the small come material that was dislodged. I
was somewhere between Vx and Vy at a very high angle of attack when the
problem occurred. The muffler is parallel l with the bottom of the
fuselage so I believe any small dislodged material would remain inside the
muffler. The plan now is to go through the entire electrical system and
check every connection associated with the EC2 and fuel delivery. I will
also be looking for a different muffle and putting the plane back into
flight testing until I can regain my confidence with the install. I am
also very thankful none of my family was onboard. My teenage daughter had
decided she didn’t want to spend the remainder of spring break with me
visiting my sister.
Bobby Hughes
(shaken not stirred)---- check your
mufflers!!!!
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