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Gents: Correct me if I’m wrong, please, but Harry’s plane came apart in clear VFR conditions over Sisters, OR. There was no thunder storm to tear the plane apart because of a fuselage weakened by a hole for air conditioning. Based on my conversation with Pat Franzen a year ago, it sounds very much like his incident over Redmond where his turbine just caught fire – again in clear VFR conditions. Witnesses describe a plane going straight down, with a plume of black smoke coming from it. That sounds like an engine fire to me. If it just shattered into pieces because of the violence of a thunderstorm and a weakened fuselage because of AC holes, it may or may not have caught fire. This one was definitely on fire. Just like the one Pat survived last year, the day before I did HPAT with him. Interesting to me how quiet things go (no one knows anything) after an incident like this. John Hafen IVP 413AJ 400 Hours From: Lancair Mailing List [mailto:lml@lancaironline.net] On Behalf Of Joseph Czabaranek
Sent: Wednesday, May 09, 2012 10:39 AM
To: lml@lancaironline.net
Subject: [LML] Re: Necessity of A/C in IV-P? Who wants to volunteer to be that test pilot? How would you determine if the nominal Vne has been reduced from flight testing without exceeding it? And then if you do exceed the new Vne I imagine the odds are greater that failure will be catastrophic and sudden rather than gradual. Flight test is a poor choice to determine new structural limits. Validate its within a margin of safety yes... I wouldn't turn off the SAS on an F-16 or change its structural modes in flight to see if the ailerons are coming off without first modeling it on the ground. And that's with an ejection seat. No amount of experience at the controls should make flight testing an attractive option for structural testing after you've cut new holes in the plane. N424DH On Tue, May 8, 2012 at 12:30 PM, Ted Noel <tednoel@cfl.rr.com> wrote: I've been watching this thread with considerable interest. And all the concerns seem valid. There seem to be three ways to deal with the problem:
1. No A/C. Not a great answer.
2. Detailed structural analysis. Problematic due to cost, and variability in individual builds.
3. Flight testing with a competent test pilot.
I think #3 is best since it deals with the variabilities of the installation and creates a hard VNE number. Also, there are a lot of A/C installations flying. This implies a degree of safety.
Ted Noel
N540TF
On 5/8/2012 7:51 AM, Colyn Case wrote: Hi Bob, That would appear to be a huge improvement in that the area of penetration through the fuselage is greatly reduced. Congrats on getting your 8 knots back b.t.w. However, given all previous discussion (e.g. read the "flutter" article on the main lml page) I personally wouldn't be comfortable pronouncing it "safe" especially to others, unless I had had the engineering analysis done on the resulting entire fuselage structure. On May 7, 2012, at 7:51 AM, Bob Rickard wrote: 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. 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. 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. 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. <IMG_0568.jpeg><IMG_0566.jpeg><IMG_0534.jpeg><IMG_0594.jpeg>--
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