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Folks, for those of you who I hoped to meet at Sun
& Fun this year, its not going to happen.
Story follows:
After the sun broke through the early AM clouds, I
launched at 1000 and found myself with a tail wind (unbelievable). I
started a 500 fpm slow climb to stay under Bravo airspace and reached 7000 MSL
about 20 miles or so on top of a overcast (clear on the other side), when the
fun started.
The first indication was a difference in the engine
sound, then I noticed the EGT on the rear rotor dropping. #&%^@ spark
Plug SAG was my initial thought - but, I had just put in 4 new B9EQV spark plugs
the previous day. Then as things continued to develop (like EGT went to
min 1200F) I noticed that the EGT (which normally only drops 300F) was at
effectively zero (or bottom of meter at 1200F). Well, as Tracy has
mentioned pulling back on the power generally helps, so I did - no
joy. Tried switching off primary and secondary injectors (alternatively of
course) still no improvement. By this time I had begun a 180 deg turn
(into a now headwind).
I tried varying the mixture control -
switched fuel tanks in case I picked up bad fuel in one tank (see I do learn)
- fuel pressure was 43 psi (nominal), oil pressure was 70 psi (nominal),
Oil temp was down to 160F, coolant was also down to 160F ( a bit
low). Indicating that perhaps less power was being produced. The
aircraft was now vibrating with the characteristic one-rotor-running
vibration. Altitude was down to 6500 MSL, but I was making no
attempt to hold altitude. Finally can see ground beneath, home base still
50 miles away. Situation is continuing to deteriorate, I have increased
fuel flow to 14 gph just to maintain 5000 rpm. A fuel flow of below
12 gph and the engine starts to unwind as if it is going to
stop.
Now I noticed that EGT on rotor number one is
coming down to around 1500F. Clearly not Sparkplug SAG. Because of
the high fuel flow I though perhaps I had a fuel problem even though pressure
was OK. I had also switched fuel tanks, just in case on tank was
bad. Engine is clearly losing power progressively. I still had 6000
MSL and was thinking about getting home, but then decided that going into the
headwind I would have very little glide (ground path) and there were no airfield
down wind of me anywhere within 40 miles.
I decided to divert to Lancaster ,SC airport (cross
wind) as it was the closest and had a 6000 ft runway - plus I could see it off
my left wing. On the way, down I thought about turning off the engine to
preserve any remaining engine power in case I needed it to make the
runway. THEN! I remember saying so many time, that despite damage -
so long as a rotary is RUNNING, it will stay running - but, if you turned it off
you would probably never get it started again. I quickly switched the
injectors back on while the prop was still windmilling and the engine caught and
fired back up. Actually had 3000 ft when I arrived over the
airfield, so would probably have made it with the engine stopped. Landing
was uneventfully and I turned off on the taxi way with the engine still
running. I notice that it took almost full throttle just to make the
aircraft taxing up a the small incline to the terminal.
Got parked, uncowled and could find no evidence of
anything amiss - but, clearly I was not going any further in the air this
day.
Then I grabbed the prop and pulled it through - no
evidence of compression on any of the six rotor faces!
It will be a day or two before I can get the engine
off and torn down to determine the cause of the problem but here are my two
candidates in no particular order other than the sequence in which they occurred
to me.
THIS IS PRELIMINARY, so stand by for corrections
after I open the engine up.
Candidate one (my initial thought) - the new
style B9EQV spark plugs electrodes stuck too far down into the combustion
chamber and all six apex seals got clipped. However, if this were the
cause, you would have though that my several full throttle runup the day
before Or early in my max power climb it would have happened. Why did it
wait until 70-80 miles down the road - took that long for heat expansion to
elongate the plug sufficiently to clip the apex seals? Hard to believe,
but I guess it possible. These are colder plugs so would stay cooler
longer But, I would have expected that if this were the cause, the
effective would have been immediate or very soon after take off..
Candidate two. I installed the plastic plenum
several days ago and have had a number or WOT runs on the ground, but this was
the first flight. Recall, thought, I have flown with plastic plenums
for a number of hours on previous iterations of intake systems (three
intakes to be precise). There is a 3/8" wall of plastic separating
the primary and secondary runners inside this plenum. This wall divides
the two runners from each other . When the TB is wide open the throttle
plate edge is at that divider and parallel to it. To
improve airflow I had sanded that divider at the throttle body to a thinner
front edge (a 3/8" blunt wall would hurt airflow). The
thought occurs that perhaps this had disintegrated and been ingested causing the
damage (those powerful FAW pulses). This would account for the problem not
happening immediately and after the climb to 7000 MSL. I examined the
engine and the exterior surface of the plenum and there was no evidence of
cracks, etc. However, it did not occur to me at the time, while waiting
for the wife to drive 50 minutes to get me, to take off the air flow tube to
examine the internal condition of the plenum, will do that
tomorrow.
Candidate three??? Any other thoughts before
I tear it down and end the mystery??
Oh, to complete the picture with local color,
the local airport manager suggested that I remove my radios - I asked
why? Well it turns out they had theft of such a week before
(just GREAT!). So pulled all the electronic gear, even took my seat
cushions home with me. While removing the radios - guess who drives up -
nope not the wife, yep!, the county's local detective assigned to the theft case
and asks me what I am doing - well, removing radios, of course. But, all
ends well and I don't get hauled to jail on top of everything else
{:>)
So again, my disappointment in not getting to see
many of you down there. Fix it up and fly down Tuesday you say?
Well, even if there were no serious damage to housings or rotor (I should be so
lucky), the guy who sell the apex seal I would use - is down in Florida -
at Sun & Fun I do believe {:>).
I have already talked with Tracy and told
him of my sparkplug theory, but I now have to give equal (if not more weight) to
disintegrating plenum. But, once again, I am amazed at the damage a rotary
engine will take and continue to produce power. Here both rotors were
damaged -not just one - and yet I could still manage, at its lowest 3000
rpm) - probably enough power to keep my RV and me airborne in a long
glide to home (but why chance it when things could get worst). Besides the
prospect of having to make a go-a-round if I misjudged the approach to our
narrow 2200 ft runway was not appealing - 6000ft was better.
Well, like I always say anything that wants to
break on the ground if just fine with me. Any thing that wants to break in
the air - so long as it gets me safely back to an airpatch (before dying
completely) - is also just fine with me.
My story for the day, now where did I put that
bottle of Whiskey?
Best Regards
Ed
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