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brewtoo
Joined: 14 Aug 2006
Posts: 1
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 Posted: Sat Aug 19, 2006 7:50 pm Post subject: That dang Tiger heat! |
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1979 Tiger. I understand that heat coming in thru the pilot-side vent is a problem on this aircraft.
The air from our left vent is nine to twelve degrees warmer than the right vent. When it's 95 degrees OAT and the vent air is 105, well, you notice it. The cooling air for the radios enters at about the same place...not good.
CHTs run 375-400 typically.
Here's what I've tried...sealed any tiny holes in firewall, no change. Completely taped over every gap on the left side of the cowling - front to back, top to bottom - tiny change, maybe two degrees. Moved the heater hose out from in front of the left outlet in the bottom of the cowl which it was blocking. No change.
Climbing, descending, power changes, turning, slips...all can affect the vent temperature. Sometimes there's a bit of an 'engine' scent. We do have a CO monitor. It is quiet.
A friend has a '79 Tiger and he has no vent-heat issues. However, he does have the ground adjustable cowl flaps. Ironically, his engine tends to run on the warm side but ours does not.
So. Is this curable? I guess it will be great in the winter time but what about the other 3/4 of the year?
Cowl flaps? Insulation in the bottom of the cowl, especially the left? Surely someone has licked this problem.
Thanks,
Brewtoo
Hot, humid Alabama
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GrummanDude
Joined: 15 Jan 2006
Posts: 926
Location: Auburn, CA
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| Posted: Sun Aug 20, 2006 12:00 am Post subject: That dang Tiger heat! |
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In a message dated 8/19/06 8:52:29 PM, brewtoo(at)yyhmail.com writes:
| Quote: | 1979 Tiger. I understand that heat coming in thru the pilot-side vent is a problem on this aircraft.
The air from our left vent is nine to twelve degrees warmer than the right vent. When it's 95 degrees OAT and the vent air is 105, well, you notice it. The cooling air for the radios enters at about the same place...not good.
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Wow, this is a new one. I've never heard of this. By your discription, it sounds like the air coming into the NACA on the pilot's side (the left side) is entering the cabin at roughly 10 degrees higher than ambient air (and the air entering on the right side.) Aside from leaks at the cowling and the heated air from the cowling entering the cabin, I can't think of anything. I would look into getting some Temperature strips (ask Ned Thomas for the key words he used in his search). Put the strips on the outside of the fuselage. They'll record the temperature of the skin of the plane. Maybe it is being heated some other way. [quote][b]
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Gary
AuCountry Aviation
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halb(at)adelphia.net
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| Posted: Sun Aug 20, 2006 4:03 am Post subject: That dang Tiger heat! |
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Where in Alabama are you located?
It's hard to say what's causing the problem with out seeing the plane. I
don't think I have that problem but I have never put a thermometer in the
air duct . I would be glad to compare planes with you to see if there is a
noticeable difference.
Hal Beauchesne Tiger N920GT
Enterprise, AL. 334-347-7360
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flyv35b(at)minetfiber.com
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| Posted: Sun Aug 20, 2006 6:18 am Post subject: That dang Tiger heat! |
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It's been known for a long time that the air temp coming in the NACA ducts is hotter than ambient air. I didn't know it was hotter on the LH side than the RH side though. I think hot air from inside the cowling leaks out through the cowl latches and into the air ducts. If you have much of an exhaust leak at the riser couplings on the LH side you will see the exhaust stains around the cowl latches. I wonder if some from the exhaust tailpipe could get swirled around to the LH side from the propeller slipstream.
Based on what I know about Grummans and the cooling problems that many owners seem to have I think that having cockpit adjustable cowls flaps might be a good idea. The speed variation from climb to cruise is just getting into the range I think where cockpit adjustable cowl flaps become beneficial. Having said that I don't think they are necessary to achieve adequate cooling with proper baffling. And maybe they aren't worth the extra cost, complexity and weight, but on my Bonanza I have better cooling at climb airspeeds with the cowl flaps open and during cruise with them closed than most Tigers. And the outlet area with them closed is probably no more than on a Tiger for a much larger engine size. Also, my cruise speed will increase about 4 kts when closing the cowl flaps. With the cowl flaps open climb CHTs can be kept not much higher than cruise CHTs and well below 400F. And that is with JPI probes and instrumentation!
Cliff
[quote] ---
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tbmorse(at)cox.net
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| Posted: Sun Aug 20, 2006 11:05 am Post subject: That dang Tiger heat! |
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I had a similar problem on my '76 Cheetah. Never could figure it out until I blew an exhaust gasket on the left side. The exhaust leak left some streaks on the outside of the cowl that ran from the little shark-fin openings on the left side of the cowl directly into the NACA scoop leading to the pilot vent. Fixing the leak did not fix the higher temperature in the vent but it did clean up the paint job.
Anyone know the purpose of the shark-fin openings on the lower left cowl? Does it augment the scoop on the bottom?
Tim
N9816U '76 Cheetah
Gilbert, Az
[quote][b]
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