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Message
OK, all you
powerplant experts, here's a good one for you. I apologize for the length
of this post, but it's a long, sordid story.
I have an LNC2 with
an IO-320-D1C (160 hp) and a Hartzell HC-F2YL-1F prop (the standard
prop supplied by Lancair). When I bought my plane (flying
since 1992, 450 hrs.) last year, RPM control and behavior were perfectly
normal. On take-off, RPM would go to 2700 at full throttle/full
increase. RPM control in flight was exactly as you would
expect.
After having flown
the plane for about 10 hours, I decided to have a JPI EDM-700 installed (by the
way, I wish I'd gone for the 800 now, but that's a different story).
During the installation the A&P discovered that the oil pressure and
temperature pick-ups were reversed from their normal locations. The
pressure pick-up was at the front of the engine at the far end of the oil galley
and the temperature sensor was on the back of the engine at the oil pump.
He said they should be the other way, so I OKed the change. After that
change (and completion of the EDM installation), the first run-up I did I
noticed oil pressure was up to 120#! It had been in the 80# range
before. I took the plane back to the A&P and he threw a pressure gauge
on it and confirmed the pressure at 120. He concluded that the previous
owner must have cranked up the pressure because he was getting a low reading due
to the pressure pick-up being in the wrong place. It appears that the
plane had been flown all of its 450 hrs. with the oil pressure over red-line
(the engine was factory new when installed). So the A&P cranked down
the pressure and I went to test fly it. Pressure was reading right in the
80-85 range during run-up, so I attempted a take-off. Upon applying full
throttle (prop and mixture controls full forward) the engine accellerated
smoothly to 2500 RPM and stayed there. I pulled the prop control back
until I got a drop in RPM then ran it back to the full increase stop. RPM
went back to 2500. Everything else looked good and the airplane wanted to
fly, so I took off and orbited over the airport. I climbed to 2,000' agl
at 120 KIAS with the RPM stable at 2500 (still full throttle and full
increase. As I levelled off and airspeed began to increase, the RPM began
to increase, just like a fixed pitch prop! Accellerating
through 160 KIAS the RPM was passing through 2700, so I pulled the prop
control back to maintain 2700, which the governor maintained as normal. I
then tried a zoom climb, and as the airspeed came down, so did the RPM. I
then descended and the RPM came back up.
Back on the ground,
the A&P checked the prop control cable and linkage and found no
problems. I didn't think he believed me about the RPM behavior, so I took
him for a ride and he fiddled around with the prop control while I flew, and it
behaved exactly the same for him. He then concluded I had a bad
governor. I asked whether messing with the oil pressure setting could have
anything to do with the RPM problem. He said it shouldn't, because the
prop governor has it's own pump that boosts the engine oil pressure up into the
200-250# range for prop control. But just to make sure, he cranked the
engine oil pressure back up to about 110 and I flew. No change in the
odd RPM behavior.
So off comes the
governor for an overhaul (it had 450 hrs. since new!). Prop shop found no
obvious problems with the gov and a normal overhaul was done. Gov is
reinstalled. I go fly. No change in the strange RPM behavior!!
A&P says prop needs overhauled (450 hrs. since new, but ten years since
manufactured). I am skeptical. Also, I have two important trips
coming up (annual Canadian fishing trip and Oshkosh!) and don't want the plane
AOG. I start communicating with Hartzell. They give me a couple of
diagnostic procedures to check the setting of the stops on the governor linkage
and the pitch stops on the prop. I pass those on to the A&P. He
claims he has already checked those settings. Over the next month I fly
the plane to Canada and Oshkosh (actually Fond Du Lac) with the strange RPM
behavior continuing. I essentially have to fly as though I have a
fixed-pitch prop, except that I can adjust RPM in level flight and the governor
will hold it.
After Oshkosh I am
slowly beginning to accept that I'm going to have to pop for a prop overhaul
(but still not convinced that is the solution). Then I have my prop strike
incident (I swear, it really was an accident! http://lancaironline.net/lists/lml/Message/18655.html).
So now, six months
later (that's another long, sordid story!), the airplane is back together and
flyable. I have a brand new prop (manufacture date 2/20/03!), the engine
has been torn down, inspected and reassembled with what was essentially a major
overhaul, I have a recently overhauled governor, and everything should work as
advertised, right? Wrong!!! First flight after rebuild, same exact
strange RPM behavior!!! We adjust the pitch stops on the prop such that we
should see a 200 rpm increase, per instructions from Hartzell. I fly. NO
CHANGE!!! Cannot get more than 2500 RPM until in level (or descending)
flight with airspeed above about 140 KIAS.
Excuse my language,
but WHAT THE HELL IS WRONG WITH MY AIRPLANE!!!!
Thanks in advance
for any help you can offer.
Lee "Q-Tip"
Metcalfe
N320WH - Kansas City
(IXD)
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