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Good points Ed, but how many hours were on this engine before it was installed in this airframe? More importantly, how many hours were on these rotors? Were the apex seal grooves checked for excessive wear? It will be interesting to see what Joe finds upon teardown.
Mark
________________________________
From: Rotary motors in aircraft on behalf of Ed Anderson
Sent: Sun 12/24/2006 7:55 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Dead Rotor at 3000ft
Mark, while there was some folks who felt that not having an air filter was
a factor. I do not concur with that hypothesis myself. Tracy Crook has
over 1600 hours without an air filter. While I certainly believe that
grit/grime (as you described it) can increase wear, I just don't think that
100-200 hours would result in significant wear - unless you perhaps live
where airborne dust is very heavy and fairly constant.
We are airborne most of the engine running time and unless you are in a
region with frequent dust/sand storms I personally do not believe that it is
that significant a factor. Also, I would expect to see compression and
power decreasing due to the same wear before it got bad enough to cause a
seal to fail.
So given the very few hours that Joe has on his engine, I just don't think
that was a significant factor. But, all this is assessment is my personal
opinion - and we all know what that's worth {:>)
Ed
----- Original Message -----
From: "Steitle, Mark R" <mark.steitle@austin.utexas.edu>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Sent: Sunday, December 24, 2006 8:43 AM
Subject: [FlyRotary] Re: Dead Rotor at 3000ft
Ed,
Adding my 2 cents worth on the subject... back when you had your rotor/apex
seal failure, I vaguely recall some comments being made about the importance
of running an air cleaner at pattern altitudes. With the oil trapped in
between the apex seals and the rotor (as it should be), injesting fine dirt
which is then mixed in with the apex seal oil creates a gritty, "lapping
compound" like mixture that will cause rapid wear of the apex seal slots.
Is this correct, or have I totally lost it? Could this be the cause of
Joe's failure?
Mark
________________________________
From: Rotary motors in aircraft on behalf of Ed Anderson
Sent: Sun 12/24/2006 7:26 AM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Dead Rotor at 3000ft
Ok, Joe. As you probably recall, I lost an apex seal (two actually) on one
rotor back a couple of years ago. My conclusion was that the problem
resulted from a combination of using used rotors in which the apex seal
slots were wallowed out taking them from a vertical slot to a "V" shape.
When I took the engine apart and measured that parameter (seal slot width),
I found it was considerably out side the specs. I was also using Hurley
seals from Atkins.
I surmised that the combination of the "V" slot which lost its ability to
support the side of the seal and the softer Hurley seals lead to one
fracturing and that piece taking out the following seal. So I now know
that the wear specification for that apex seal slot is something to pay
attention to.
I went to new rotors and now use Tracy Crooks apex seals (much, much
stronger than stock or Hurley).
Ed
----- Original Message -----
From: Joe Hull <mailto:joeh@PilgrimTech.com>
To: Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
Sent: Sunday, December 24, 2006 12:00 AM
Subject: [FlyRotary] Re: Dead Rotor at 3000ft
Thanx Ed. I'll double check but pretty sure I'm at 35.
Have a very, very Merry Christmas too! (hoping the spouse and others gift
you with many aviation toys!)
Joe
________________________________
From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On
Behalf Of Ed Anderson
Sent: Saturday, December 23, 2006 8:31 PM
To: Rotary motors in aircraft
Subject: [FlyRotary] Re: Dead Rotor at 3000ft
Joe, Sorry to hear about your problem but glad to hear you brought her back
safely. Does certainly appear you have a bad apex seal. You might want to
check your ignition timing. I once mistakenly (of course - who would to it
intentionally {:>)) sat my static timing to 45 deg rather than 35. I
noticed while flying that If I opened up the throttle wide open the note of
the exhaust changed to a staccato popping. Well did not fortunately lose an
apex seal but I found the center electrode ceramic cone was missing for two
of the 4 plugs and cracked on the other two. Just lucky they didn't take
out the apex seal. So you might check that timing just to be certain.
"Merry Christmas"?
Ed
----- Original Message -----
From: Joe Hull <mailto:joeh@PilgrimTech.com>
To: Rotary motors in aircraft <mailto:flyrotary@lancaironline.net>
Sent: Saturday, December 23, 2006 11:15 PM
Subject: [FlyRotary] Dead Rotor at 3000ft
The weather today in the Seattle area was marginal for flying - but a nice
hole opened around my home airport (KAWO) and I was there tinkering with the
plane anyway (re-torqueing the prop)- so up I went. I did 4 touch and goes
just for a wee bit of practice and then departed the pattern toward a bigger
hole that would be legal to climb through VFR. I flew about 30 miles
northwest of the airport out to the edge of the Puget Sound and enjoyed just
being in the air. Power setting was about 4400RPM and I was loping along at
a lazy 135kts. I turned around and headed back for Arlington and decided to
ramp up the power to ramming speed - errr I mean cruising speed. In a few
minutes I was cruising along at 170kts at about 5500RPM. Then all of a
sudden BAM - the engine stumbled and RPM's dropped to 2300RPM. I
immediately throttled back and switched tanks while turning toward the
airport. Altitude was 3200FT (about 3000AGL) and I was maybe 7 miles from
the airport. The engine was running real rough and wouldn't give me more
than 2300RPM. Even with that little bit of power I ended up entering the 45
to the pattern at about 800 above pattern altitude. It was pretty slow at
the airport so I easily made a normal landing and was able to taxi back to
the hanger under power.
At the hangar I double checked everything I could from the cockpit - fuel
pressure good at 36PSI, oil pressure good at 55PSI at 2300 RPM, MicroTech
ECM showed "OK" for the size major areas it monitors. So, I shut it down and
pulled the cowl. I pulled the prop through a number of times and it seemed
that there was a couple places where I should have been hearing a "pop" in
the exhaust but didn't. I also notice that there is a nice ding in the prop
that is about an inch long - that wasn't there when I left (remember I'm a
pusher).
I got the engine compression gage and proceeded to take the spark plug out
of the front rotor - top - BR9EQ-14. Hmmm - I don't remember there being a
casing around the electrode - and why is that casing sliding? Apparently
the casing around the electrode broke somewhere inside the sparkplug and
into two halves long ways down the electrode. Each half slides freely up and
down the electrode and even sticks out a little from the end.
I put the compression gage on and it looks like I get 30-30-70 when I turn
the engine over. I tried this several times and there is definitely a couple
of places where it only goes to 30. So I double check the location of that
ding in the prop - hmmm it's exactly even with the bottom of the exhaust -
right about where an apex seal would come out.
I put two new BR9EQ-14's in both rotors and did a quick run - 2300RPM rough
is the best I could get.
Some time this week I'll go up and yank the exhaust so I can see the apex
seals - my guess is I'm missing at least one. Bummer.
Joe Hull (getting tired of little surprises in the air).
Redmond/Seattle WA, Cozy-Mazda Rotary 71hrs
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