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Charlie K / Colyn
I just did the opposite this winter, and removed the Airflow
systems scoop from my IV-P and engineered a low drag plenum out back. I saw an
8 knot gain in TAS at FL180. My original system was installed in 2001 time
frame (1st flight in ’02), so I don’t know if it was the “reduced
drag” version. I’m very aware of the topic of cutting holes in the fuselage
and took great care to overdesign the modification and have a carbon expert
build and install it. There are bids of reinforcing carbon both inside and
outside the fuselage that are cut well beyond the scoops, which are also made
of carbon and hysol’d in. A couple of pics attached, I’m planning a LOBO
paper on it sometime soon. It works very well, looks fantastic, is light
(except for the fan), and is strong and safe.
Bob R
From: Lancair Mailing
List [mailto:lml@lancaironline.net] On Behalf Of Charlie Kohler
Sent: Friday, May 04, 2012 9:26 AM
To: lml@lancaironline.net
Subject: [LML] Re: Necessity of A/C in IV-P?
Yes-it worked out fine. By that- I mean- it was the best you can
do.
In the beginning, The pressurized IVs had the cabin intercooler
located on the side of the left lower cowling- with louvers. The intake air was
taken from the engine air cleaner box. Even after moving the intercooler to the
front/left side the air (thanks Don) into the cabin was measured at 105°on the
70° day.
What I didn't say in the post yesterday was that selecting 11,000
feet on the controller put an electrical signal to the outflow valve to open it
wide open. You also could use the "dump" switch to open the valve.
That helps a lot. But the big Issue is to shut off that 105° air from entering
the cabin.
I liked the idea of the Airflow design--but I heard stories of
airspeed penalties with the P51 scoop. I asked Bill Genevro if he had ever
considered doing wind tunnel testing.Then they did-- at Ohio University. They
tucked the condenser up closer to the fuselage and drag reduced drastically. I
bought his system. At that time there was no choice. I did testing later
and saw less than three knot change--. The only holes cut in the fuselage was a
pair of 1 inch holes for freon in and out of the condenser. The beautiful part
of it, is that --it works. Very well! In all regimes.
From: Colyn
Case <colyncase@earthlink.net>
To: lml@lancaironline.net
Sent: Friday, May 4, 2012 8:08 AM
Subject: [LML] Re: Necessity of A/C in IV-P?
Charlie,
how did that work out? You eventually added the airflow systems unit
right?
Does that
require a hole through the fuselage floor?
On May 3,
2012, at 1:20 PM, Charlie Kohler wrote:
In the years before AC was available, I developed a plan for
Summer (hot) flying. On take off I set the controller to 11,000 feet with the
Pressurized air to the cabin OFF. I opened the air valve from the fresh air
from the vertical stabilizer.
I took off and climbed to 11,000 feet . At 10,000 feet I closed
the fresh aHim himir from the vertical stabilizer and gradually selected the
pressurized air to the cabin to the ON position. Then as I continued to climb I
selected the cruise altitude on the pressurization controller and adjusted the
rate knob to 200 feet a minute descent. The cabin would then descend and level
off 1000 feet above selected altitude.
On the descent into the landing airport-- I set the controller to
1000 feet above field elevation.
Complicated maybe--but it kept the hot turbocharged air out
of the cabin until it was necessary.
It can be really warn even at 17,000
feet without A/C in an IV-PT. Why? The bleed air is super warm. Absolutely
necessary? Not IMHO. But a few letdowns from 20k+ and a drip drip drip off the
end of your nose will tell you it’s nice. Or in summer heat in Houston, Phoenix
or some other sauna, it is even better than nice.
Wouldn’t it be good to use that air to
air heat exchanger in line with the bleed air to the cabin? HEAVY.
From: Lancair
Mailing List [mailto:lml@lancaironline.net] On Behalf Of Dan & Kari
Olsen
Sent: Wednesday, May 02, 2012 11:05 AM
To: lml@lancaironline.net
Subject: [LML] Necessity of A/C in IV-P?
With all the discussion of
structural integrity compromises of the IV-P fuselage by cutting air
conditioning holes, I have a question for you seasoned IV-P drivers… How
necessary is air conditioning in this aircraft?
I have been flying my 320 for
almost 9 years now and certainly would love to have had it during ground
operations on hot summer days with the green house canopy. However, once
moving and at altitude, there is no need. I realize that the IV-P is
going to have warmer air because of the pressurization but it is also typically
flying much higher (colder ambient) and it doesn’t have the bubble canopy.
So, in normal cross country
cruise operations above FL180, do any of you that don’t have A/C *really*
wish that you had it?
I’m early in the building of my
IV-P and don’t want to put it in for several reasons:
· Potential structural issues
· One more thing to break down the road
I live in Colorado and will be
using this plane as a cross country traveler with my wife, so comfort is
certainly a factor but not at all costs. One thought is to get one of
those cooler-with-ice-and-a-fan systems to toss in the back seat for those few
days that are very hot.
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