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PostPosted: Tue Dec 13, 2005 10:08 am
by yankeflyer
looking for cool air at altitude ? density altitude in a 2000 lb plane at a runway at 4600 ft and a 460lb ultralight and the same runway - :huh:

PostPosted: Tue Dec 13, 2005 7:05 pm
by daffy1029
Hi russellrewis,
Yes, the take-off distance is much shorter. The engines have more power and the wings have more lift in cold weather. A lazair feels more alive!! Just have to dress for the weather :ph34r: . Daffy

PostPosted: Tue Dec 13, 2005 8:38 pm
by yankeflyer
Hey Russell,

I hope I didn't sound too flip but in general aviation training density altitude is emphasized and pounded into your head as much as weight and balance is.

On that hot Midsummer day you describe -- imagine that, it is here, at the Clyde ice airfield in Spearfish, South Dakota. You're taking off on a runway 3000 ft. long, more than enough to get that 100 horsepower Grumman AA1A into the air. But previous experience tells you to trust the seat of your pants and even though the gauges all read right and on a good day the plane only gains 400 ft. per minute anyway -- it's 100° outside and density altitude has cut that rate of climb in half and the ridgeline that is a half a mile off the end of the runway still appears to be 10 ft. above the windshield. And every time you try to pull back on the stick -- the seat of your pants tells you that you are not gaining any altitude and one more inch back on the stick and you're probably going to stall the thing. If not stall - your Grumman is going to go into a mush and start losing altitude. Maybe not much but at that particular point in time -- 10 ft. can be important.

Realizing that any action taken so far has not improved your situation, the best you can hope for is not make the situation worse and as the story goes -- the Grumman clears the ridgeline by a good 50 ft. but normally you're climbing out at 400 to 500 ft. per minute and clearing the ridgeline by 200 or 300 ft.

On the other side of the coin I've flown ultralights in situations that break all those density altitude rules and I've seen a Lazair at the ultralight air park in Arlington Washington do a 180 right in front of the clubhouse; where we all gathered to watch the other pilots practice their touching goes - at a slower speed than any other airplane/ultralight that I had seen flying the pattern and it may have been an optical illusion but I swear the wing on the inside of the turn flew backwards.

To say nothing of the fact that he was only about 50 ft. above the ground. I did a lot of crazy things in ultralights myself back then, 1987 to 1995 - pushing all the rules to the limits and Rick Moore and I came to the conclusion because of the lower weight of ultralights 250/ 300 pounds and some combination of ground effect, lightweight and adequately powered, ultralights seem to be able to bend the rules.

But as we witnessed not too long ago -- an ultralight crash into a crowd if you going to experiment and test out the limits of your skill and your aircraft it's a good idea to do it out in the country in the wide-open spaces and to do a little reading on the subject. Micro meteorology -- situational awareness -- Our flying knowledge comes from the experience and science of a lot a great pilots and builders who have come before us. And this forum certainly is a roster of new talent and contributors. B)

PostPosted: Tue Dec 13, 2005 8:44 pm
by yankeflyer
If you can go snowmobiling - you can fly in it. :ph34r:

PostPosted: Wed Dec 14, 2005 10:04 am
by russell

No flip taken (actually it was over my head). The reason I asked about the cold air was because at a 140 pounds soaking wet I have little problem in hot air anyway and the mild winters offer no contrast in roll distance. The only thin air sensation I experience is in climbing out of tight spaces. A friend has a 1938 65 hp Aeronca and in the summer it struggles to lift two people but in the winter it performs to it's full potential.