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