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  #1  
Old 11-06-2017, 10:27 AM
pvalovich pvalovich is offline
 
Join Date: Dec 2005
Location: Ridgecrest, CA
Posts: 439
Default Mountain Flying - More Lessons Learned

Saturday afternoon passenger drop-off flight over the Southern Sierra Nevada Mountains from Inyokern (IYK) to Kern Valley (L05) - less than 30 miles. Wind 260/12 at IYK. Climbed to 8500 in clear skies to safely clear the two major ridgelines enroute. A little bumpy, but nothing unusual for the Southern Sierra. Uneventful leg - except noting winds were on the nose at 42kts at 8500 ft.

Return leg at 7500 ft. Fewer bumps than first leg until lee side of westernmost ridge. First roller banged my head off the canopy (thought I was tightly strapped in - but I was wrong) and induced an uncontrolled right roll. Second roller immediately thereafter continued roll with nose down pitch. Ended up about 120 degrees right wing down, 30 degrees nose low, accelerating. + 4.5, -3.1 g's on the g meter. This occurred within 2-3 seconds under clear skies, in pretty calm air with no warning.

Lessons learned:
1. Be wary of ridge crossings with high tailwinds.
2. Ensure you have enough altitude for recovery from nose low unusual attitudes.
3. Be comfortable with sudden unusual attitude recovery (I'm a former Navy A-4 Adversary pilot; joke about being more comfortable upside down than right side up).
4. If you suddenly find yourself nose low with excessive bank, roll wings level before pulling to the horizon - otherwise you risk increasing bank into a tight nose down spiral.
5. Be aware of your nose low airspeed - Vne is a real number.
6. Clear skies does not correlate to smooth air in the mountains.
7. Be wary - and prepared.
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  #2  
Old 11-06-2017, 11:06 AM
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Ironflight Ironflight is offline
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Location: Dayton, NV
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Good reminders Paul! Flying on the eastern slopes of the Sierra this time of year can be sobering - clear skies plus winds can mean...wham!!

We fly up and down the Owens Valley between Carson City and Big Bear a lot, and always try to be done with the trip by mid-morning if there are any winds at all. If we're forced to go when the winds are up, I generally stay well away from the Sierra (west) side of the valley, or fly low between the Mojave and Bishop. Those High Sierra are world class wave and roller generators!

I had an A&P exam at Fox Field last March, and it finished up about 0900. I coudl feel the wind coming up already, so I decided to go spend another night at Big Bear instead of heading up the Valley for home. Glad I did, as pilot reports for bumps got pretty severe that afternoon.

A man's gotta know his (and his airplane's) limitations!
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  #3  
Old 11-06-2017, 02:17 PM
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snopercod snopercod is offline
 
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Scary stuff. Foreflight has Turbulence Potential and Mountain Wave forecast charts, which I believe to be accurate.
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  #4  
Old 11-06-2017, 07:51 PM
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Steve Melton Steve Melton is offline
 
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wow, a +4.5g thump in Clear Air Turbulence (CAT). RV-9/9A is utility category (+4.4/-1.75 G). I'm reading "The Electra Story" and it is fascinating. It's a FREE Kindle book. Just certified by the agency, two brand new planes' wings fall off from CAT within two weeks of each other. In 1957 they allowed it to continue to fly but reduced the max speed from 400 kt to 225.
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Last edited by Steve Melton : 11-06-2017 at 08:08 PM.
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  #5  
Old 11-06-2017, 08:10 PM
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mchargmg mchargmg is offline
 
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Location: Palmer Lake, CO
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Default Similar

Yes, after a similar incident, I went back to watching the upper winds when I fly around the mountains in Colorado. If they are above 25 knots at 12,000 or above I go somewhere else. Cuts down on my mountain trips, but it also alleviates my head hitting the canopy.
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  #6  
Old 11-06-2017, 08:48 PM
Robb Robb is offline
 
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Location: Nevada City Ca
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I had a similar experience over Utah last year. Hit my head hard and when I got back I ordered a set of harnesses with a crotch strap. I must admit my Husky takes the bumps a lot better probably because it goes a lot slower and has inertial reels in the seat belts
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  #7  
Old 11-06-2017, 09:07 PM
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Steve Melton Steve Melton is offline
 
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Quote:
Originally Posted by RV8JD View Post
Well, not quite. The Electra's came apart due to Whirl Flutter.
I'm about halfway into the book and it's pointing towards CAT but now I know how it ends ( I asked for it )..... what the heck is whirl flutter? blades in resonance with engine whirl?
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Cincinnati, OH
RV-9A, Tip-up, Superior O-320, roller lifters, 160HP, WW 200RV, dual impulse slick mags, oil pressure = 65 psi, EGT = 1300F, flight hours = 900+ for all

Simplicity is the art in design.
I was born an airplane nut. I have no explanation for it.
My Artwork is freely given and published and cannot be patented.
www.rvplasticparts.com

Last edited by Steve Melton : 11-06-2017 at 09:22 PM.
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  #8  
Old 11-07-2017, 12:49 AM
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skylor skylor is offline
 
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Location: Southern California
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Default Whirl Flutter

Quote:
Originally Posted by Steve Melton View Post
I'm about halfway into the book and it's pointing towards CAT but now I know how it ends ( I asked for it )..... what the heck is whirl flutter? blades in resonance with engine whirl?
More like wing resonance with propellor slip-stream..

It?s technically called whirl-mode flutter.
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  #9  
Old 11-07-2017, 01:25 AM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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The rule of thumb I was taught is a thousand feet of terrain clearance for every ten knots of wind. Above thirty knots, fuhgeddaboutit. I did most of my mountain flying over Arizona, and never had occasion to challenge the 10,000+ ft high passes in Colorado (had a converted Cessna back then.) not sure I wanted to.

At least take an online mountain flying course...
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  #10  
Old 11-07-2017, 04:56 AM
AttackPilot64 AttackPilot64 is offline
 
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Location: SPring lake NC
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Default Mountian Flying

Mountian Flying can be an adventure for sure. Its important to learn about Winds and wind terrain analysis. Be careful on the leeward side of the mountain. That's were those downdrafts occur.
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