Mountain flying forum at osh

[Bill Greenwood]

I am already thinking about going to Oshkosh, and looking forward to it, despite having about 3 in of new snow on the ground.

I am doing a presentation on Mt. Flying this year, and I wonder is anyone has any specific questions or areas that I could prepare for or cover.
If so, please give me a brief idea here.

And this is oriented toward someone who might be flying into Colo. for vacation.
It should be mostly applicable to other areas as well.

It's not Alaska type bush flying.

I did this the 1st year at Sun N Fun, and just before the start, I thought, "who cares about this in the middle of Florida", but was surprised at a decent turnout and good reception.

There have been other presentations of this type, but mostly they are not from those living and flying in the middle of the mountains.
Thanks

[gbrasch]

Bill, I think this is a great idea on your part. When I learned to fly as a kid in Illinois, density altitude was only something I read about in a book. Now after thousands of hours in the mountains it is something I view with great respect. Good luck!

[Bill Greenwood]

Glenn, I don't fly copters but was just talking to a friend who has a new one here and the service ceiling at about 13,000 due to something like retreating tip stall if I have the right term.
He was doing a search for a local missing skier, and being very careful in a valley surrounded by peaks at 14,400.

Medevac service is invaluable here, especially in winter. It is 90 air miles to the nearest big trauma hospital. Folks love to get outside, but you can get in trouble.

[danielfindling]

I live in S.E. Michigan where the terrain varies by maybe 500 feet over the course of the State. Notwithstanding, I love the romance of Mountain Flying and I dream of flying my Cessna 140A in the "bush".

Here are some questions I would like explained:

The concept of a rotor on a the downwind side of a mountain with low and slow flying. Is there a minimum altitude above a peak necessary to avoid the rotor?

I remember reading that Steve Fosset died in a SuperCub in part because the downdrafts exceeded the airplanes ability to climb. What factors (in addition to density altitude) should a pilot be aware of? Is there a critical wind speed/Altitude over a Mountain to avoid?

Emergency procedures with Mountain flying: Where do you put a plane down?

Hope this helps. (Oh, and I would love to hear your opinions on the questions posed.)

Daniel


P.S. I asked a bush helicopter pilot during a ski trip how he accounted for rotors and he gave a reply akin to watch for minor airspeed fluctuations, and seat of the pants (feel of the airplane) response that did not make a whole lot of sense to me.

[Joe Delene]

Thanks, those educational & safety forums are one of my newer favorite things to do at Airventure. I went to several last year & may do even more this year.

[Victor Bravo]

Bill, maybe spend some time on explaining how wind moving through a pass or a gap creates sinking air downstream of the gap. Approaching a high pass from the downwind side will put you in a combination of headwinds and sink that can easily overcome an average airplane's climbing and penetrating ability.

Random ideas:

Staying the hell out of wave systems until you have had some wave training in sailplanes.
Staying well beow maneuvering speed/gust speed when flying through wave rotors.
Using the lift on the windward side of a ridge,a nd not flying along the downwind side.
Always leaving an "out" where you can "fall away" from any hill, or the mountain range, to lower terrain.
Never turning downwind when that turn is toward the mountain.
Using the artificial horizon as a frequent reference, even in VFR conditions, to augment the compromised visual "horizon".
Use of partial wing flap deployment to increase control authority and stall resistance when maneuvering at low speed and high DA.

[gbrasch]

Glenn, I don't fly copters but was just talking to a friend who has a new one here and the service ceiling at about 13,000 due to something like retreating tip stall if I have the right term.
He was doing a search for a local missing skier, and being very careful in a valley surrounded by peaks at 14,400.

Medevac service is invaluable here, especially in winter. It is 90 air miles to the nearest big trauma hospital. Folks love to get outside, but you can get in trouble.

You got it Bill........the "official" term is retreating blade stall, close enough. Here are the factors that contribute to it, as you can see, density altitude is on the list:

• High gross weight
• High airspeed
• Low rotor RPM
• High density altitude
• Steep or abrupt turns
• Turbulent ambient air

[Bill Greenwood]

Dan, as for how far to fly over and clear a ridge by in order to avoid turbulence and downdrafts on the leeward or downwind side; just as a rule of thumb, about 2000 feet above the peak is usually ok. BUT IT DEPENDS. The three main passes that I cross going to Boulder/Denver are about 12,000, so I may go east at 13,500 or a little higher and west at 14,500. It depends on the winds aloft, which we get from FSS at 9, 12, and 18. If they are for instance, 15 knots, 20 knots and 45 knots, then 2000 feet AGL or so is probably ok. If they are much higher, say 25 knots, 35 knots, 55 knots, I would likely go to 4000 feet above to cross the pass. 40 knots at 12 is pretty much the limit of what I will fly in, but I would also check for pireps along the route. If only light turb is reported or even moderate by a pilot who is flying low, the I could probably cross ok at 15,500 or 16,000 and not descend till I was past the turbulent area,
But, I would be very careful and often cancel if someone where I am going has reported mod to severe especially if it is a large plane. Having been in severe once or twice where it put my head into the roof and tossed off my headset and all the ash trays out of the holders and papers on the floor, I don't want to do it again. Fortunaltely I had slowed down,but it still feel like getting hit by a linebacker that you didn't see coming.

My turbo Be 36 will easily go above 16,000. If you are in a 140 then you need to go on a calm day, usually early morning. You can cross at 12,500 but there is little margin for error.

I aim so when I cross I am as high as I need to be, and going into lower terrain, and always with room to turn around.

[AmigoOne]

Hi Bill, I live in Virginia next to the Appalachian and I have a good idea of the amount of turbulence that these mountains can generate on windy days which I'm sure they are child's play compared to the Rockies. This summer after Oshkosh we are planning with a friend to cross the Rockies in our way to Seattle. Throughout the years I have purchased a mountain flying video, read articles and most recently at S&F I got the shirt pocket guide by Sparky Anderson. Still as a flatlander I will start the summertime journey over the Rockies with a healthy degree of apprehension. Leaving Oshkosh we plan our first stop in Rapid CIty, SD and from there I would like to ask you, if you know, what would be the best route to make at least the navigating route a bit easier. The weather is another issue and I'll continue to study the subject. We will come back over the southern route where the desert heat becomes an issue and for that I guess that the best strategy is a departure before sundown and landing at or before mid-day. I would have preferred a different route and to do it might depend on the experience of the first crossing.
I'm also planning to attend your seminar at Oshkosh. We will be flying a 1968 Mooney Ranger.

[Bill Greenwood]

Amigo, my first airplane was a 1970 Mooney M20 C Ranger.
Let me take a look at the route up north to Seattle and get back to writing in the next day or two. I have flown from Osh to Seattle, but it has been years ago, and I was in a much different airplane. I have also flown a few times from Colo to Wash in some other planes,one a T-34.

Just in brief, go in good weather, probably early morning flights. Have O2 on board, keep the load light.