Subject: How much will this cost me?
From: Rotary Engine
Date: 2/21/2009, 3:05 PM
To: AAA Put this in the To box



Hi, Paul:

My project kitplane will be the Aerocomp CA11, (photo attached), a 6-place,
pressurized monster with an equally enormous TPE-331-14 (1,600 shp) turboprop.
In discussions with the company, it is not unrealistic to downgrade the engine
to 800 hp with the accompanying reduced gross weight penalty.  My intentions
are to somehow assemble a 3 rotor 20B turbocharged, turbocompound rotary with
an SFC goal of 0.33.  Instead of hauling around 400 gal of Jet A fuel in the
wings, I think my math works out to only needing 200 gal of Avgas, giving me
a weight savings of 1600 lbs which is better than the reduced gross weight penalty.

My question is all about cost, a topic dear to anyone these days.  How much
will all of this really involve?  How many parts are 'off the shelf', how
much design and testing will be needed, how many prototypes will blow up
before we get this right?  Here's a quick list of what I think I need but
please comment where you find yourself laughing on the floor.

  * 200 hp per rotor (by the way, what's the advantage/disadvantage
between the P-Port and side housing ports)
  * 200 hp X 3 rotor = 600 hp + 30% increase with
turbocompounding = 800 hp max power.  I intend to cruise at 75% power.(600 hp)
  * Turbo critical altitude of 25,000 ft.  The turbo will need to
deliver 600hp up to 25k as well as pressurize the cabin at 6 psi.
  * I believe the ideal design calls for turbocompounding directly
at the exhaust port, then turbocharging coming next in line (instead of
the other way around)
  * Can variable inlet geometry turbochargers eliminate the need for wastegates?
  * Have silicon carbide ceramic apex seals been developed enough to consider for this project?
  * Besides the end housings, what other parts can/should be made of aluminum?
  * Is there any performance gain in the Berilium/Aluminum rotors over cast iron, or is the cost too
prohibitive?
  * Can I expect 9,000 rpm max takeoff from this engine, and cruise at 6,700 rpm all day?  BTW, prop
speeds are 1,600-2,200 rpm so I need a PRSU of 4:1
  * Can a PRSU that will handle up to 1,000 hp be found 'off the shelf' or is this a major "fresh
sheet" component? (I think I already know the answer)
  * How much work/discussion has this forum had with the good people at specialty shops like Racing
Beat, Barber-Nichols, Vibratech, etc?  I think they are a must in order to design this right
(instead of a hit-n-miss approach)
  * The TPE-331-14 engine weighs 620 lbs dry.  Will the rotary engine weigh more than this (with
coolant and rad)?
  * Can the Mistral Dual Digital Engine Mangement system be adapted to this engine?  I assume Mistral
sells their components for Experimental users.
So, how much will this prototype cost to get it airborne?  $50,000?  $100,000?
10X more?  Once developed, is it marketable as an 800 hp stump-puller?  Can all
the R & D that went into it be used for smaller variants?  That's the one problem
I see with this whole rotary aeroengine thing.  Those of us on this forum all have
our own unique design and size requirements.  There is no one engine to suit everybody.
We are all pioneers, as it were, checking out recycle and used car lots trying to
find parts for our 1-of-a-kind engines.  We know more about the auto applications
than some mechanics, and spend lonely hours in our garage trying to connect oil
lines and custom fit starter motors.

Are there others on this forum who have an interest or need in such a big
engine as I've described?  Are there any who would like to develop a
turbocompound system for their engine, regardless of the HP range?
If I knew what kind of money this project would require, I could either
start down the path myself, or join in with the many others who might
like to join in for the adventure.  Who knows, maybe there's 50 people
in the world who have $10,000 to invest.  Or maybe I'm standing all
alone with the crickets.

Paul, you would seem to be the natural conductor of this train.  I'm
asking for your advise and opinion on whether the engine described
above is realistic.  If so, how do we get from A to Z?  If we make a
committment to 'git'er done, the train might finally leave the station.
Otherwise, we will still be talking about it 10 years from now.  I know
this is a marketable project (an ICE with 0.35 SFC).  Whether it's
certifiable is doubtful unless Mistral wants to join in (also doubtful).
But as an experimental powerplant option with 'off the shelf' availability,
there might be more than a few customers.

Thanks to all for any comments.
Greg Fleming

Contact Jim Mederer at Racing Beat and get him to give you a quote
on a 4 rotor turbo. My guess is right around 1000 HP with
2/3rd the fuel burn of a turbo prop. Also better performance
in the 20,000 to 30,000 foot range

I'll work on the rest of the questions when I get back from
Aus next week. I am on the EeePC which is rather small.

Paul Lamar

Greg,

This is a very interesting idea.  I was looking at the Malibu as a starting point for a project.  I was interested in a composite "clone" if you will.  Your project will be very interesting to follow.


DB

Bill Fedorko, COO of CompAir says they will have a prototype of the -11 at Fun 'n Sun in April.  I will be there with a million questions and a million gig memory card in my camera.  Biggest question is how much can the powerplant be derated before the aircraft just won't take-off or climb.  They have already planned for offering the TPE-331-10 engine which is a downgrade from their monster -14 engine.  That's a drop from 1,600 shp to 1,000 shp.  Both engines claim an SFC of 0.53.  They also cost $250,000 + each and that's for a zero-time overhauled.  If a rotary engine can be installed, I will need to seek out a good design engineering firm to plan out the firewall forward refit.  I know I will get support from AeroComp since a successful outcome is good for all parties.

My concern with using a certified aircraft (i.e. Malibu) as a starting point is that the aircraft would be 'neutered' for life with the certification removed (at least here in Canada).  Starting with an experimental gives more freedom to modify the powerplant and gives the airframe vendor another powerplant option, however using an unproven airframe along with a new engine doubles the chances of problems.  Fortunately, CompAir has been designing and making airplanes for some years now and this is not a completely new venture for them.
Greg Fleming

I agree with what Jim says.
Last time I looked Compair was using a chopper gun to layup fuselages
if not wing skins. Is that still true?

Paul Lamar In Melbourne on the way home

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