qbynewbie
Pre-takeoff checklist
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- Sep 22, 2007
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Qbynewbie
I completed my long cross-country last Saturday. In the write up (Long cross-country completed or Long cross-country completed ), I reported running into a mountain wave that really surprised me. Worse, I reacted incorrectly and could easily have crashed as a result.
I ran into the wave less than 20 minutes from home. I was over Bennington, VT, where the mountains are only about 4,000 feet tall. Who would ever think about mountain waves so low? Unfortunately, I was descending from 7,500' to 5,500' to maintain VFR, so I was coming with 1,400 feet of terrain when I leveled out. Except that I didn't level out and was carried downward for about six-hundred feet before I got the vertical descent stopped and then was able to climb again.
But that was a mistake. I jokingly blamed the whole thing on Henning, who had written about mountain waves that very morning here on these forums. On the Purple Board, he responded:
After some research, it turns out the Henning is correct (Big surprise there.): dive out of a downdraft and climb out of an updraft. It's really counterintuitive -- when I was caught in that downdraft, I REALLY wanted to climb -- but nevertheless correct. Trying to outclimb a downdraft in a light GA airplane is not the right thing to do.
I found a PDF called Mountain Flying. It's produced by the Civil Aviation Authority of New Zealand. I think it's really good and chock full of information pilots should know even if they are only flying over itty, bitty mountains. Consequently, I'm posting this on all three forums, something I generally try to avoid.
http://www.caa.govt.nz/safety_info/GAPs/Mountain_Flying.pdf
I ran into the wave less than 20 minutes from home. I was over Bennington, VT, where the mountains are only about 4,000 feet tall. Who would ever think about mountain waves so low? Unfortunately, I was descending from 7,500' to 5,500' to maintain VFR, so I was coming with 1,400 feet of terrain when I leveled out. Except that I didn't level out and was carried downward for about six-hundred feet before I got the vertical descent stopped and then was able to climb again.
But that was a mistake. I jokingly blamed the whole thing on Henning, who had written about mountain waves that very morning here on these forums. On the Purple Board, he responded:
I wanted to learn as much as I could about mountain waves. I actually had a lesson in mountain flying in Alaska last month, when I took a first ASES lesson in a Supercub on floats at Moose Pass. Then it was clear that we were in MOUNTAINS... great, tall, mountains. My CFI was explicit about flying near the mountains, not in the middle (gives you the most room to turn in an emergency), seeking out updrafts, leaving yourself an out, being careful about canyons, etc. But I was stupid enough to not extrapolate that to the terrain here near home. I guess we always feel comfortable near home.
After some research, it turns out the Henning is correct (Big surprise there.): dive out of a downdraft and climb out of an updraft. It's really counterintuitive -- when I was caught in that downdraft, I REALLY wanted to climb -- but nevertheless correct. Trying to outclimb a downdraft in a light GA airplane is not the right thing to do.
I found a PDF called Mountain Flying. It's produced by the Civil Aviation Authority of New Zealand. I think it's really good and chock full of information pilots should know even if they are only flying over itty, bitty mountains. Consequently, I'm posting this on all three forums, something I generally try to avoid.
http://www.caa.govt.nz/safety_info/GAPs/Mountain_Flying.pdf
