Used Avionics

wrote in
:

Flying east is great, but my plane's slow enough that the
speed gain from altitude doesn't come close to making up for the
headwind hit. Flying west I'll usually cruise 2000' AGL and argue
with the bumps and slightly faster groundspeed.

The higher you go, the more likely the winds are out of the west - as
you say. In the summer they may "drift around" a bit, but in the winter
you can almost count on it. On shorter flights, or against the
headwinds, I will usually try to stay fairly low - probably below 10K
(although sometimes in the summer I *have* decided that 1+30 in cool
smooth air was better than 1+00 in thermals and with the OAT reading
over 100 F.

Longer flights will *usually* make it worth it to climb into higher
altitudes. I'll usually break even, even with a headwind, and get
better conditions, less traffic, and better routing if IFR.

WITH the wind... well, coming back from El Paso one winter day after
dropping off an Angel Flight patient, I was throttled back to 55% in the
low flight levels, sipping about 8.5 gph, and watching the groundspeed
vary between 250 and 275 knots!!!! [Of course, a *significant* part of
that was tailwind! G]

Question though... my mechanic recently did the the wastegate
upgrade, but it seems like it didn't do a whole lot for it. Stock
setup was atrocious (make boost all the time and regulate MP with
throttle only). It was almost rotation speed before he was able to
look up from the MP and tach on takeoff, because it wanted to
overboost so much. Even with the new one, it seems flakey and prone
to overboost. True? Any way to add an intercooler to the setup too?

The stock wastegate setup used by Piper (and by Mooney) on many models
is 14 karat CHEAP! It's a bolt screwed into a hole in a pipe, period.
No matter how you set it up, at sea level you are providing boost (and
heat) when you least need it. And at higher altitudes you are dumping
half your boost overboard. About the ONLY thing that could be said good
for it is that it's cheap, and well, it can hardly break.

The other downside, as you noticed, is that it makes bootstrapping a
significant issue in setting the throttle. Add throttle and the MP will
continue to rise (substantially) after you stop moving the throttle.
Reduce the throttle, and you will often find yourself having to add some
back in.

With practice it is not as bad as it sounds. You get used to it... and
throttle movement becomes somewhat automatic -- just the "automatic"
part is in your head rather than in the controls. G Still, it is NOT
really a good thing for a plane on the leaseback or flight training line
- precisely where many of them are used. This is been a major reason
that many turbo Arrows have gotten a bad reputation for short engine
life.

Something like the Merlyn automatic helps a lot. At sea level and
cruise power the wastegate is fully open - you are running essentially
unboosted. Temperatures stay low. Climbing high the wastegate
completely closes and adds almost 6K feet to your critical altitude -
that REALLY helps with the climb. Bootstrapping is still there - but
it's much better. Not nearly as sensitive until you get up into the
flight levels (where, with the wastegate fully closed, you are back to
being the same as before in terms of bootstrapping sensitivity).

There is an aftermarket intercooler mod. I know another pilot here in
Austin that has one on his turbo Arrow and he likes it. I don't have
one on mine, and haven't really ever had significant temperature
problems. There is a "cooling kit" that basically adds some more vents
to the cowling - most have had this added, and it is very recommended.

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James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
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