|
|
<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
<< Lancair Builders' Mail List >>
<<<<<<<<<<<<<<<<--->>>>>>>>>>>>>>>>
>>
N361DC (my lancair 360) flew for the first time Saturday, September 9, 2000 at
10:50 am from Romeo airport (D98) in Michigan at the capable hands of Mike
Dehate. What a day!
I have a full report that Marv Kaye has asked be placed in the upcoming issue of
the LNN. However, there were some issues that I want to post to you folks here
and get your opinions. Here they are...
"Meanwhile, time is ticking off and we have some pressure because I need stick
time before Mike leaves in order to be able to continue to fly the airplane
safely. The two remaining problems caused me heartburn: a baulky idle mixture
circuit and a prop/governor problem. Both of which I would like help from the
list with.
The governor (McCauley unit from Lancair) problem surfaced when we tried a full
power run-up to check static rpm. 2400 rpm was best we could do. No good.
This is an IO-360 B1F with MT prop (MTV-12B). Target was 2600 rpm roughly. The
prop would cycle normally however. Very unfortunately, I had some time ago
removed the governor control arm to thin it so that the B-nut would fit on it.
I realised too late that I had neglected to mark its position on the splined
shaft and did not know where to put it back on. I guessed and flagged Mike
about this. Figuring that I had put it back on wrong we moved it so that the
governor would allow a higher engine rpm (rotate the governor shaft further into
the body). We move it all the way to the limit and could do no better than 2450
rpm (?!) We took the governor to a prop shop and had it tested. It was about
right at our final setting requiring the shop to tweak it only a little. Then
the technician gave me the dredded "come hither" finger. He said the governor
was flowing about half the oil it was supposed to. Yes, it was a new unit. Yes
it was effectively on the shelf for a long time (2Q'97 build date). He said it
should function normally but he wouldn't let one like this out of his shop. We
put it back on the airplane and no luck, the rpm was not improved. Must be the
prop (right?) MT has an easy way to adjust the blade pitch stops with a single
nut on the front. We turned it and were finally able to get a satisfactory
static rpm of 2600. Great, we're all set (yeah, right!)
During the takeoff roll and into the initial climb the rpm climbed beyond 2700
and went well over. Mike was able to clamp it down with the prop control but we
figured it went about 10% overspeed which sent us scurrying to the MT manual for
consequences - fortunately only a 100 hour inspection. But why was our newly
checked out governor allowing such an overspeed? We turned the prop pitch nut
back halfway towards the original setting and found the overspeed was less. We
found on subsequent runs that we could prevent overspeed by progressively
pulling back the prop control during the takeoff run. We also found that we
could not get more than a 10 or 20 rpm drop during prop cycling at the 1800 rpm
runup. During flight the governor seems to control rpm normally in the range we
used between 2200 and 2500 rpm and the position of the control seemed "normal"
compared to what I had been previously used to. The rpm measurement was
identical on the VMS unit and the separate rpm counter Mike had.
Our conclusion: something's wrong with the governor. We base this primarily on
the fact that the prop shop set it for 2700 max rpm (we watched this) and their
statement that the flow rate was inadequate. Does anybody out there have a view
that fits the evidence? If so, I would really like to hear it since we judge
the airplane not flyable by me alone until this gets resolved.
The second problem concerns the Precision fuel control unit. We are unable to
get the customary 30-50 rpm rise during leaning at idle without running the
mixture adjustment so rich that it jams against the unit housing during throttle
application. We are also getting a lot of fuel seeping into the throttle body
after shut down. We can tell this because the unit has been rotated forward
with a 90 degree elbow attaching it to the bottom of the oil pan, so fuel tends
to pool in the intake pipe in front of the injection unit. Additionally, when
hot, the engine will diesel after the mixture is pulled for shut down and there
is a lot of popping during idle which Mike described as "after firing". The
mixture control screen was examined and found to be free of foreign material.
This is a factory new Lycoming engine which spent an hour on the test dyno with
this injection unit installed. All flight performance seemed to be normal.
Our conclusion: the idle mixture plates inside the fuel control unit are worn
or otherwise damaged. Can anyone shed any additional light on this? Best way to
fix, etc.
But back to the first flight... " and the rest you will have to wait for your
LNN copy.
For those of you not yet at this magical day, keep building and think safety.
The airplane will reward you with a fabulous experience.
Best Regards,
Ed de Chazal
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
LML website: http://www.olsusa.com/Users/Mkaye/maillist.html
LML Builders' Bookstore: http://www.buildersbooks.com/lancair
Please send your photos and drawings to marvkaye@olsusa.com.
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
|
|