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Seeing as how one rotor operation CAN happen, I thought I
might mention my experience with one rotor flight.
When I lost the apex seal (and compression) on my front
rotor in April 2004, three things immediately happened. The engine
started vibrating (noticeable but not severe), the rpm started to drop, and the
EGT on the affected rotor went to minimum of the gage (1200F).
I was at max gross weight at 7000 ft when this
happened. Well, having nothing better to do, I experimented trying to find
some combination of setting that would maximize power with the remaining
rotor.
I found that if I cranked up the mixture to maximum rich,
which at that point gave me 14.5 GPH burn rate, that I could keep the rpm above
4000 rpm. Naturally all that fuel going through the bad rotor was not
producing any meaningful power and I might have been leaving a "afterburner"
flame (don't know),but the engine rpm stayed around 4200-4400 rpm.
Besides, I was fully loaded with fuel, so did not mind get rid of some of that
stuff prior to landing.
I suspect that quickly increasing the mixture before the
engine has had time to unwind in rpm may be crucial. I don't think you
would likely gain back rpm lost, so taking this action immediately may make a
difference in how much rpm you can maintain.
I flew approx 60 miles in the one rotor condition
maintaining 6500 MSL and could have probably made it back to my 2200 ft
strip. But, the sight of a 6000 ft runway just off my left wing was too
tempting - besides, I did not know what had caused the failure (but at the time
I thought it was the different spark plugs I had just put in the day before) so
decided setting it down while I still had power was the wiser thing to
do.
After making a safe landing - on the taxi back to the
parking area, the one thing I notice was how much more throttle it took to
taxi.{:>)
Just thought I would pass my experience on. Turning
up the mixture was not the first thing that occurred to me, it was just the only
thing that seemed to help.
FWIW
Ed
----- Original Message -----
Sent: Sunday, December 24, 2006 8:23
AM
Subject: [FlyRotary] Re: Dead Rotor at
3000ft
Joe,
Sorry
to hear about the problem. Good
to hear though, that you can lose a rotor, still make a safe landing, and taxi
back to the hanger. There are
many problems that could have ended in a worse result. At least you are OK, the plane is OK,
and you’re at your home field.
My
spark plugs are BR9EQ-7’s and 9’s.
What engine do you have ?
Steve
Brooks
-----Original
Message-----
From: Rotary
motors in aircraft [mailto:flyrotary@lancaironline.net]On Behalf Of Joe Hull
Sent: Saturday, December 23, 2006 11:16
PM
To: Rotary motors in
aircraft
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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