Safety Documents

Here is a safety document on mountain flying.


Don't Smack the Mountain_img_19

Good morning, class. Today we will be discussing an alarming statistic. In the past 30 years our soaring area has witnessed 5 fatal accidents in the mountains and 3 of these accidents have occurred within the last 5 years! Would one of you work up a trend analysis on those statistics? Thank you Mr. Kelly.

All these accidents involved experienced pilots flying modern sailplanes and most of them impacted with high energy, indicating a stall situation. Why would an experienced aviator inadvertently stall his aircraft, especially near the rocks? Everybody now look at the graphic, the top sailplane represents us flying into the page as we approach a mountain on our initial pass. We stay 300 feet away from the rocks and keep our speed up (minimum 65 knots). Is that safe enough? Maybe not! Lets just suppose there’s trouble lurking out there in the form of a gigantic gust, a really strong thermal, a violent wind shear. For the purposes of our discussion we’ll just call it a zephyr and its going to apply a differential rolling moment to our theoretical sailplane. What’s a differential rolling moment? Good question, Mr. Green, it happens when our right wing flies into lift that is much stronger than what our left wing is experiencing. We are constantly looking for this, aren’t we? We call it “light wing” and turn into the wing that’s coming up as soon as possible, because there’s probably a thermal on the light wing side. Ever try to turn into the light wing and have the machine refuse to turn? Sure, happens all the time and we say something like, Turn, you big beast, turn! What’s happening? Why won’t the ship turn into the rising wing? Because, the thermal is stronger than the authority available in our ailerons. Another way to state this is; The thermal is trying to roll us left and we are trying to make the ship roll right. The result is a Mexican stand off and we fly straight with full right stick and rudder applied.

Now class, look at the second sailplane in the graphic. That’s us, still flying into the page, but the zephyr’s got us and its rolling us left into the mountain. We have applied full right stick & rudder, but the zephyr’s stronger than the controls and we’re still rolling left and there’s rocks over there! Why is this happening? It is estimated that our ailerons can only counteract a differential moment of 500 fpm. Let’s say there’s 1200 fpm under our right wing and only 300 fpm under our left wing. Reasonable figures? Sure, we see 1200 fpm all the time on the Whites and in the Sierras, only near this damned mountain it’s mostly under our right wing!

Now, look at the third ship. We’re in real trouble, aren’t we? There are rocks and trees up there on our canopy where the sky is supposed to be! We’re experienced aviators and we don’t panic, we continue to hold full right stick & rudder and apply forward stick to make the rocks stay away from our canopy.


Class, remember what we learned in Aviation –101? We can stall a ship in any attitude and at almost any airspeed, can’t we? I believe it was in chapter 6 that we learned how to do a snap roll. All you had to do was slam in full rudder and full back stick and the airplane would do a snap roll in the direction of applied rudder. Can we stall a ship while inverted? Yes we can! OK, resume action. We’re flying 65 knots, holding full right rudder and the stick’s now in the right forward corner. What’s the ship likely to do? It might try to snap roll to the right, but the zephyr probably won’t allow that, so I’m betting it will just stall & fall and we have another mysterious high energy impact on the side of a mountain, don’t we?

Does it have to be this way? Are those of us who choose to fly close to the mountains, destined to become a high-energy impact, some day? NO

I see Mr. Seamons has his hand up. OK, sir what’s you question? How do we prevent smacking the mountain? Good question, I was just getting to that. First of all, there are days where I won’t get within 1000 feet of the rocks. If I’m approaching a mountain and the turbulence is so bad that things are flying around the cockpit. I don’t get within 1000 foot of the rocks

Let say I’m approaching the Whites, I’m holding 65 knots and things seem fairly smooth. My computer tells me the westerly wind should make the canyon up ahead, work. But, what if there’s a zephyr in the canyon? What if it tries to roll me into the mountain? As I get within 300 feet of the rocks, I roll the ship into a 30 degree right bank and hold it there with a bit of top rudder. Why? Because, I’m already banked away from the mountain, so if a zephyr tries to get me, I’m ready to apply all three control inputs to fight it with right stick, right rudder and back stick to make it turn away from the rocks.

I also follow all the normal rules about never turn directly into the mountain, always S turn an area for a beat or two before attempting to circle. If I fly by an area that shows 300-fpm lift for 20 seconds, I turn away from the mountain and come back through the lift area to verify it really is workable lift. If it is, I turn 90 degrees away from the rocks, roll wings level for a count of 3 (you know 1000-one, 1000-two, 1000-three) then I turn back into the mountain. My 3-second burst flying away from the rocks gives me plenty of room to finishing a turn into the mountain, but I’m still not committed. As I face the rocks again, I ask myself; Am I 100% sure I can finish this turn? Only if the answer is an unequivocal YES, do I continue. If I’m not completely sure, I roll the other way and continue S turning the area. If I do continue the turn, I may shallow out the turn as I come parallel to the rocks and let the ship drift in close, if that’s where the best lift is. I do this while holding a 30 degree bank angle AWAY from the rocks.

OK, that’s enough for today, class dismissed!

Oh, one more thing, always keep an escape route open! You may see some of this material on the quarterly exam. Mr. Kelly, you may give your accident trend analysis, first thing Monday morning, please hold it down to 2 minutes, maximum.

Don't Smack the Mountain_img_20


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

%d bloggers like this: