"Jim Burns" wrote in message
...
Mike,

Just a few questions and thoughts, mainly because I'm curious.

I'd be interested to know the HP rating of the GO480 installed in the
Helio.
I've been watching a few people that are building Bearhawks and one
article
mentions that the GO480 isn't favored for that application for the
relative
high weight to HP ratio compared to the 540.

295HP


I "believe" that the Beech Queen Air originally used a version of the 480
and I "know" a lot of them have been retrofitted with either 720's or
turbines. Whether this was due to high rebuild or maintenance costs or
lack
of power, I have no idea.

Would the desirability of the 480 in the Helio be due to a desire to keep
them "original"?


No, Helio owners only care about STOL performance. The Helio requires high
power for takeoff only. Actually what it requires is high static thrust and
it benefits from a large diameter prop so that thrust flows over more of the
slats/wing/flaps. The geared engine can use a larger diameter prop without
the tips going supersonic. Once airborn, the airplane is not going to go
very fast (135-140kts) with its large wing and large exposed wheels no
matter how much power is availible.

The 350hp TIO 540 tends to overheat in the Helio probably due to the
cowling/baffling design. There were only about seven Helios made with the
TIO540 and at least three seem to be on the market at any given time, a dead
giveaway that the airplane is a lemon..

The 400hp IO 720 adds a lot of weight both in terms of the engine itself and
the additional fuel it requires.

Both the H700 and H800 (350hp and 400hp) were also designed to accomodate
both nosewheel and tailwheel configurations and they are heavier as a
result.

I was surprised that this was the case since generally later airplanes are
improved over earlier ones with various bugs fixed. MU-2s underwent a
gradual transformation over the ~20 yr production run where they got more
power, more pressurization, more fuel capacity, better avionics ect. I went
to OSH last year specifically to find out why all the experienced Helio
pilots preferred the H295 (295hp) to the H700 (350hp) and H800 (400hp). The
explanations varied somewhat but everyone thought strongly that the earlier
ones were better.

The ultimate Helio is a early model with an Allison turbine engine. I know
of only one that exists. This give you a larger prop, much more power AND
lighter weight, although fuel consumption eats up some of the weight
savings.

Mike
MU-2