Date: Tue, 11 Jan 2000 09:53:30 -0600 From: David Domeier Subject: COZY: Cozy Cold Wx Ops I do not have as much cold weather experience in small airplanes as many of you , so I've been doing some reading and experimenting. A very good source of information on cold weather operations is the Lycoming Flyer. It covers induction ice, water in fuel system, pre heat, engine temperature considerations, and the "whistle slot" for the oil breather line. The entire Flyer is online at Lycoming. Just a few observations so far. The Cozy carb heat as per the plan with the Ellison unit works very well. One caveat, make sure cabin heat is off or the system will suck cold air from the cabin. I am assuming the heat to the carb is adequate based on how much heat comes forward with cabin heat on since the source is the same. A pre take off check at 2000 rpm yields a 50 rpm drop. On a cold day, the pipes are not very hot at that time so the check won't tell much except that the valve is working. Lycoming recommends a minimum oil temp of 160°. It has been a while since I've seen 160 so yesterday I ran quite hard in a climb to 9000' and finally got it up to 169°. This is important, I think, if the engine is going to sit idle for any length of time because one needs to vaporize as much moisture in the oil system as possible. Minimum oil temp has been a problem. It may be advisable to block the cooler as is done in Pipers, although I don't know why one should have to do that if the thermal bypass is working properly at 190°. I think mine is since the oil temp sits at 190° in cruise much of the summer. Pre-heat, according to Lycoming, should be used if the temp is below 10°F. I haven't seen such a low temp this year and if it does get that cold, I'm not flying....can't think of a reason to do so unless war is declared and Cozy's are pressed into action. The coldest temp I've operated in was in the mid 20s and the engine started immediately. The B&C electric stuff along with electronic ignition makes all that happen. The oil temp was less than 30 but it came up to 60 in just a few minutes. Cabin heat is adequate and mostly a function of how well the cabin is sealed. Mine works good down to the 20's but one day I noticed not much heat was coming forward. After a bit of sleuthing I found the carb heat was not full off. If that valve door is open just a smidgen cabin heat is gone. When I pushed it full closed, there was a rush of hot air. The oil breather line can freeze up if the exit is in the cold slip stream. It's happened many times and the result is a popped crank shaft seal and loss of some oil. The fix is a small vent hole somewhere in the breather line inside the engine compartment. They call it a "whistle slot" in the Bonanza's. This could happen in our airplanes anytime since we do fly them quite high where temps can be below freezing. In closing, engine performance in cold air depends on how warmed up the engine is. I've noticed first take off rpm of 2330 with the oil temp around 70° and 2360+ later after things are hot. There probably is less friction when the oil is hot as opposed to just warm. dd