Hi Jim,
First let me welcome Charlie back, I missed him for a while. I very much
appreciate your inputs and am very happy that your AC works that good. In no way
do I feel that either system is better than the other rather that we all have
two choices. However, I would like to respond to a few things that Charlie
brought up that are not completely true.
Thanks for these good comments, sure is better than getting flamed.
Not completely true? Those are the things I'm looking to square
away.
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The Aero Cool the system is heavier. (Extra equipment-fan. Heavier
wiring-fan. Heavier hoses- to run further aft.)
The fan weight is probably less that 2 or 3 lbs different if at all. It would
take weighing the two systems to know.
You are right, The only way we can determine the truth here is to
weigh both systems and make sure the inventory is correct. Later , you mentioned
that the scoop would be equal to mounting for the condenser. The scoop is made
out of carbon and is very light. The one Installation I saw of the Aero Cool
looked much heavier. And the items above in parentheses are undoubtedly heavier
in the Aero-Cool system.
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The scoop and all it's attaching cloth, resin, primer and paint and you have
to run the lines from the armrest area to the center of the floor taking up
space there. How do you cover them? Does that weigh anything?
The scoop is made out of carbon and is very light. No covers are
needed. Air conditioning hoses go underneath the aft side of the main spar
covers. Alongside the main fuel lines. The dryer is located on the sidewall.
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I just got back from my Concorde trip to the UK and I gained almost 10 lbs.
Who cares about 2 or 3?
A pound here , a pound there, adds up. I think it's a trade-off. I
have the Ryan 9900 BX. It's a very heavy unit. I think I would rather have it at
the expense of most anything else.
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The Aero Cool system has drag by cutting holes in the fuselage and blowing
out hot air. Perhaps more drag than a scoop.
This is pure guessing.
Yes, but educated (from experience) guessing.
I first flew the Lancair at Santa Paula Airport , with Neil Perks in
1991. The airplane did not have gear doors over the main gear. When they
installed those doors, The airspeed increased approximately 15
knots.
Do you recall , the Orinda , powered Tigris? I recall a conversation
with Don G. in which he said that during a test flight with the radiator
exhausting down the side of the fuselage that he felt it was trying to go
sideways. The speeds estimated never materialized. I wonder why?
I recall having a door come open on an Aztec many years ago and
nearly lost control.
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air is NOT going in but spilling over in the slipstream.
I would maintain that the air is spilling out of the NACA scoop and
not entering if you have the fan turned off.
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How does your belly scoop handle the drag when it is not needed for cooling?
If air is going thru the condenser then it is big drag.
Possibly, but the term "big" would indicate a large loss of airspeed
, and that is not the case. And the KISS principle applies. No doors. No levers.
No cranks. No motors.
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(Questions arise as to structural strength. *)
Strength is probably a slight bit less but it is in the big part of the
fuselage not the small area in front of the tail. That is where the L4 is weak.
In fact the factory is coming out with a tail stiffing mod. that adds about 2
inches to the leading edge of the vertical stab. and a much bigger dorsel fin
going forward to help strengthen the tail torsorsonal resistance. It looks much
better too. Just do a vertical Hit on the tip of you Horz stab. and watch the
shake. Then do this on the Tandem, you will see the difference and why they will
probably require this on the turbines.
I worked two years in the engineering department of International
Harvester motor truck engineering division, in the stress lab. I performed photo
stress, stress coat, and strain gauge analysis of truck frames , front end parts
etc. etc..
The term "slight bit less" would have made my boss go
ballistic.
One of the reason I chose the Lancair, was the stress analysis--and
flutter analysis. We are modifying these airplanes to the point where these
original analysis are no longer valid. Band-Aids are being put in places where a
new analysis should be done. Your hitting the tail to excite the empennage is
just the warning flag.
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Aero Cool system requires much more electrical service.
I don't see this, but we would have to put a load meter on to find out. When
I idle at 800 rpm with the AC full on I do get a low voltage light and my SFS
reads 12.9 volts. Then after take off with everything on I get a Low Voltage and
Standby Alt light when I put the gear up. That Hyd. pump draws a lot. BTW, I
have a 65 amp alt. on 12V and full UPS stack, 3 screen SFS, TCAD, Storm Scope,
and TruTrak 3 servo AP. All on but not engaged at that time. In other words, I'm
drawing a few amps that others may not.
The only electrical load that would be in excess of the Airflow
system is that of the condenser cooling fan.
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The Aero Cool system is much more complex to install.
I'm not sure how easy it is to install the scoop on the bottom and paint but
I would call it about even.
If I'm correct, I understand that in the Aero Cool system, the
elevator pressure compensators are removed. Then a modification to the elevator
pressure boots to the direct system. Installing the condenser box, cutting
holes, installing scoops, moving electronic equipment , etc. etc.
Whereas, on the airflow system the scoop is glued directly to the
fuselage by standard surface preparation and clicos.
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Mine doesn't take ANY room out of the baggage compartment, and I still could
have put in a SKI tube. The condenser is below the baggage floor level and
behind the rear baggage bulkhead. The TCAD, Stormscope, and AHRS would be the
ones likely to interfere.
I give you this one.
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The Aero Cool system moves the center of gravity aft. Will you be able to
carry backseat passengers in that rare event they're needed?
I recently had 4 on board, Mike Custard being one, and 55 gals. Took off from
Sedona, AZ. 4800 ft Alt. with AC on and flew over the Grand Canyon and made it
back. Nice ride. However, I will give Charlie one here that I am in the aft CG
area. Just weighed it with full 108 gal. fuel and two 200 pounders in the front
and was at 92.4% vs a 94% aft limit. Must watch the back seat load.
Sure glad you "made it back." If I had one more figure, gross weight,
we we could see where the CG curve is. Using MT prop, I'm afraid I would be out
the aft limit with 114 gal. of fuel , and a hefty copilot.
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The Aero Cool system cost more to purchase--costs more to install.
I use to worry about money now I worry about have enough time to spend it. I
don't know the prices so that should be taken into account.
I sure would like to work for you!
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The Airflow systems unit needs no fan for the condenser.
How long can you be taxing or on hold on the ground before it shows less
cooling?
Actually , I don't know of any restriction or time that would make
the Airflow system be less effective. If it works 10 minutes after start up,
it'll work good 30 minutes after start up.
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It works well on the ground (the propeller provides the cooling airflow over
the condenser.)
Therefore, it's lighter. Condenser can be smaller because of the adequate
Airflow in all régimes.
Condenser size and weight should be compared, I'm not sure that they aren't
about the same weight just different shape.
As with any heat exchanger, you can increase area to get better
cooling/heating. Have you ever heard of the discussion to increase the
size?
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Condenser is located outside the hull,
and the heat associated in a closed contained environment, therefore requiring
less Airflow to cool the condensate.
This is a guess. Mine is outside of the pressure vessel also. My complete
fuselage is a heat sink in the rear. And cooling drag is bad from other areas,
like the cowl seams and the NOSE gear doors. Also, where does all that air go
that we pump into the cabin? An airplane is a Bunch of compromises flying in
close formation, ya know.
I would debate , the wisdom of using the empennage as a "heat sink."
I agree that cabin pressurization air is exhausted into the wheel well
area
and spills out into the airstream. For what effect I do not know. And
yes , we compromise all over the place.
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Small loss in airspeed, that perhaps, may be the same as, or less than
the Aero Cool system, due to less weight, and no holes in the fuselage providing
turbulent Airflow over the fuselage and tail surfaces.
I guess that is where "LESS FILLING / TASTE GREAT" also applies here, I don't
think I loose any speed..
Your right, It looks great on a P-51.
Hey, I loved your discussion anyway. Let's fly.
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BTW, you have never given a report of the MT prop with swept blades. And be
objective.