saddletramp wrote:

Mountain Doctor wrote:

saddletramp wrote:This is a great topic. On another board I mentioned on a recent trip through the Columbia Gorge in my 57 182A that was very turbulent, I looked out at those old wings & wondered just how strong they really were.

Sailplanes have been mentioned. I'm a CFI/glider (& airplane). One thing that's saved my rear a few times is this: When you're in a strong downdraft increase airspeed...this will get you out of the down air quicker. The ride might be more miserable but you'll get to better air quicker. It's kind of like spin recovery. Even though your nose is pointing down...pushing it forward will get the wing flying again.

I've been a pilot for 45 years & I find as I age, turbulence bothers me more than it used to.

Maybe it's the "no old bold pilots" saying.

Nice to see another Southeast Washington dweller here. Do you fly out of WW or Martin Field?

I'm based at Martin. I'm in the process of starting a glider operation here. I'm hoping to get the sailplane bought soon & hope to be in operation by spring. I owned a similar operation up in Ephrata during the early 90's. I thought about a trike Maule for a tow plane too. I would have preferred a tailwheel tow plane but there's getting to less tailwheel guys around.

My wife & I hope to get out and fly to some of the mountain strips in our 182 also.

If you start a glider operation at Martin I'll commit to being one of your first customers.

Martin Field is one of my favorite local airstrips. I have a lot of respect for Dave and what he has accomplished there. College Place is a beautiful town and Martin Field is like going back in time to a kinder gentler place. I also like the grass strip.

I look forward to seing the Maule towplane also!

Headoutdaplane wrote:While the air in a down draft may flatten out and go horizontal, an aircraft weighs more and the inertia of the aircraft may continue down and hit the ground. If you are counting on the air "flattening out" and saving you, you may want to rethink that strategy.

My comment was not to imply that the air flattening out will "save" you by itself, and yes the inertia of the airplane of course does not stop as fast as the air.

What I was pointing out, and completely stand behind, is this: If you are flying close to the ground, where the downdraft has ALREADY "flattened out", the local air movement becomes far more 'back and forth' and far less 'up and down'. Which means that there will be LESS up and down air currents acting on your airplane in the first place (the uncomfortable stuff) and MORE horizontal wind (which is a lot more comfortable and less hard on the airplane). Your airplane will develop LESS of a sink rate in the first place, because it had LESS downward air velocity acting on it.

If you are flying along at 1000 feet AGL, and you are caught in a severe downburst, and because of that downburst acting on the airplane for 20 seconds your little airplane is descending at 10K feet per minute toward the ground... the air "flattening out" at 100 or 200 AGL is certainly not going to save you from being splattered. Like Bing Crosby said... "Aloha on the steel guitar".

But if your airplane was flying LEVEL at 100 feet AGL, not climbing or descending, then the greatly reduced downward vector from the downburst (because it flattened out before it reaches the ground) will apply far less downward force on your airplane. You will have less (or no) downward inertia to overcome (desperately putting in the power, pulling back on the stick, etc.)

OR, to address Gump's reference to bugs on the windshield, if that bug had been flying back and forth in "ground effect" very close to the windshield, and a 60 MPH gust of wind hits the car from the front, the bug is not going to be splattered into the windshield. His annoying little ass is going to be blown ALONG the windshield surface, over the top of the car, and swirl around for a minute in the wake turbulence behind the car. But he will live another day... he will not get squashed on the windshield like his poor dead friend who was just flying around the hood ornament, and had enough distance (altitude) for the wind to accelerate his sorry ass in the direction of a hard surface.

I'm losing situational awareness on this discussion. I have never flown through a thunderstorm or rotor cloud under a lenticular. I have flown in all strength of updraft and downdraft from 2-10,000 feet per minute in most makes of small manufactured aircraft. Never hit the ground. Always hit a strong bump and air going the other way. When in control, I managed this energy by flying slow in up air and fast through down air. Maybe I was just lucky and maybe I am wrong about natural air flow in the mountains.

I want to see one of those bugs that can fly back and forth in ground effect close to my windshield.

EZFLAP, I understand the theory of what you are saying, I just can't come up with a flying scenario where I would apply it.

Folks that have flown Lake Clark pass (a fairly narrow passage through the mountains from Lake Clark to the Cool inlet) on a windy day have seen the beaver ponds as still as they can be while you are getting the crap kicked out of you at 500, or 1000 feet, however, if you watch long enough the ponds will have williwaws (cats paws, wind shadows, whatever you want to call them) explode on them, meaning the down drafts are getting to the surface.

More to the point I believe in the collective learning experience. I can't say I have seen anyone flying the pass at 100 feet on a bouncy day - low cloud days yes - but not bouncy. If it worked the experienced guys would be doing it, and they don't.

Headoutdaplane wrote:EZFLAP, I understand the theory of what you are saying, I just can't come up with a flying scenario where I would apply it.

Folks that have flown Lake Clark pass (a fairly narrow passage through the mountains from Lake Clark to the Cool inlet) on a windy day have seen the beaver ponds as still as they can be while you are getting the crap kicked out of you at 500, or 1000 feet, however, if you watch long enough the ponds will have williwaws (cats paws, wind shadows, whatever you want to call them) explode on them, meaning the down drafts are getting to the surface.

More to the point I believe in the collective learning experience. I can't say I have seen anyone flying the pass at 100 feet on a bouncy day - low cloud days yes - but not bouncy. If it worked the experienced guys would be doing it, and they don't.

I totally agree and have flown through Lake Clark pass many times when the winds suck. I will not be flying right on the deck on this kind of day.

The day I wrecked Bushwacker in Alaska west of Iliamna the winds were blowing 35-45 at 1000 agl. I probably should have turned around and headed back to the calmer air at Iliamna Airport but instead I thought I would land at the strip I was headed too. I figured if I got down and did not like what I was encountering I would add power and go back to the airport. In fact as I was on my final into the long straight unobstructed patch of firm tundra I was thinking this is not that bad. I got lots of room, when I was only 10-15 feet off the ground about to touch down that is when a gust of wind hit me from the left side of the airplane that stood the airplane on knife edge vertical to the ground. At that moment I added full power to fly out of it and to my surprise the airplane continued in an arc to the right. I was stuck in that vertical position and even though I had full power it felt as ever foot went by the airplane was looking down more at the ground then the sky. I realized I was going to hit hard at full power and pulled the power to idle and came to a complete stop instantly. It turned out when I retraced my ground track that my right wing made contact with the ground when I was hit with this severe cross wind and never broke free of it. As I was on the ground the wind would come and go from 0 to gusting 40 or more. Scary shit wind is and I had a similar encounter the day before in the Wrangells on final to Devils Mountain Lodge but instead of being 15 feet off the ground when I was hit by it I was 600 feet but the same thing happened. The airplane went completely knife edge instantly.

I am a different pilot now. I get the heck out of nasty/windy places if I have a choice and if I am ever concerned about the airplane coming apart because of turbulence I am getting that plane on the ground. Most likely turning around and going for the direction the air was smoother is going to be my first choice. Call me chicken but until you wreck an airplane because of wind maybe you can't appreciate the
place I am at now.

The wind ended up taking my slightly damaged airplane and flipping it upside down during the night and finishing it off. You can see a picture of the airplane upside down in my gallery if you click on the web site. It shows just how wide open the area I was landing was.

Mountain winds can be and often are amazing. A fellow in a Turbo Beaver on floats went to the south end of Kodiak, and was going to land in the lee of a peninsula. Had the engine near flight idle when the Williwaw hit, and he went to max. Older PT 6 so spooled slow, and he hit the water just as the engine made all sorts of power.

Hit so hard it broke both spreader bars on the floats. Flew it back to town and landed on the wheels......floats spread eagled, but nothing else got hurt.

And, he was very low when that thing hit him.

Mountain winds can be amazing. Around here sometimes there'll be almost no wind and all of a sudden it'll rattle the rafters, then ten minutes later it'll be calm again.

MTV

Wow, going to have to go back and read this thread...

...as for downdrafts...my take on it is that you can have a bunch of momentum going, and the wind may not go through the ground...but it can go all the way to the ground...and you have a bunch of downward inertia going...

I was just out for a scenic tour with my Dad and my son a few years back, and was just doing a touch and go on every airstrip I came across, wasn't even a windy day...

...but at Ekwok, on short final I hit a serious pile of sink air, went full power...and landed. With full power. Not a spool-up problem.

Wasn't a hard landing, but it made me super aware of my altitude when the air starts dropping.


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Older pilot told me he never went through Lake Clark Pass if the winds at Iliamna were gusting over 30. That discussion came after I had already been through the rodeo a few times...but I have found it is a pretty good rule of thumb. If the wind is over 25 at Iliamna, the pass is rarely fun. Over 30 it is horrible. When my GPS ground speed is 55 mph and the airspeed is 105...in the mountains...no thanks. Been there, done that, done with that.


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You guys make me glad that I live in an area so flat we give names to the tallest rows of cotton.

Although a downdraft is converted to outwash before it reaches the ground, flying low (depending upon your location and flight direction relative to the core) can result in your flying dierectly from a strong outwash headwind to an equally strong outwash tailwind. The immediate transient effect on the plane due to the sudden loss of airspeed is the same as if the downdraft continued all the way to the ground. I'll pass. Been there, done that. Once.

Jim C,

I'm not sure what you mean by low, but when spraying in ground effect, I found shears sent me sideways and not down.

At 200' on pipelines, either in the mountains or Midwest, I found a hole and pitched down, rather than up, in a downwind shear. So over many long days and many hours, I found ground effect and energy management to be effective.

That doesn't mitigate the greater safety of avoidance. It just supports the need to keep flying no matter what and to work with , rather than against, natural energy. This is more pertinent to those who have to work in the wind. Many are the possible preparatory possibilities for those who don't. Due to my years at so low an orientation, I know high altitude or simulator training is inefficient. You sort of have to be down there when the wind is blowing.

Jim

JimC wrote:You guys make me glad that I live in an area so flat we give names to the tallest rows of cotton.

Although a downdraft is converted to outwash before it reaches the ground, flying low (depending upon your location and flight direction relative to the core) can result in your flying dierectly from a strong outwash headwind to an equally strong outwash tailwind. The immediate transient effect on the plane due to the sudden loss of airspeed is the same as if the downdraft continued all the way to the ground. I'll pass. Been there, done that. Once.

Had a similar experience on an ILS - in the clouds trying to recover to the ground in the middle of a line of pop-up thunderstorms. Scared the crap out of me when I saw the A/S needle swinging counterclockwise fairly quickly. I'll pass on that one again, too.

Bdiazair wrote:When we left dead cow we went through truckee up the valley to Delano, glad we didn't go through mammoth pass, it looked rough. We had a 35-40 knot head wind the whole way back.

Delano, eh?

I'm based down at MIT and just got myself stuck into a Maule. Working on a dirt strip just east of you out by highway 65.... we should connect some time!




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We recently crossed the Sierra's with a 60 knot tail wind...smooth as glass. We've been over that pile of rocks so many times, in so much weather, that we've gotten a pretty good idea of where to go and where to avoid. Looking down, the snow was whipping off the ridges at ferocious rates. Aside from a brief 2,000 fpm climb from 14,000 to 14,800, we could just about trim the airplane by leaning back and forth.

Lord help anyone down low, however. Trying to get through one of the passes that day would have been suicide. And at our altitude there are still areas we wouldn't go near. Anywhere the lee side burble coming off a peak has the potential to catch you in the downward part of its wave is a no-no, the way mine fields and extremely radio active areas are no-no's.

I am SO thankful for the hundreds of hours I spent in a tiny, underpowered airplane...learning these lessons when the wind was blowing ten knots is a lot more forgiving than when it's blowing 60.

tcj wrote:I want to see one of those bugs that can fly back and forth in ground effect close to my windshield.

Funnily enough, I think butterflies can sometimes avoid the windscreen, at least at car speeds... They seem to change direction fast enough to avoid the windsheild as the airflow re-directs around the car. Bugs will smaller wing to body mass ratios, seem to go splat every time.

I tend to subscribe to the "air spreading out" theory too. Of course there are exceptions and extreme cases, and I don't fly under thunderstorms or low through passes on windy days either. But for anyone unlucky or foolish enough, I think there would be some hope in flat land at least. There is no accounting for mountain turbulence, although some places low in the mountains are safe in certain winds.

But as I say eariler, I would say turbulence is "bumpy air". A massive downdraft and windshear is a whole different kettle of fish.

Mauleguy wrote:The day I wrecked Bushwacker in Alaska west of Iliamna the winds were blowing 35-45 at 1000 agl. I probably should have turned around and headed back to the calmer air at Iliamna Airport but instead I thought I would land at the strip I was headed too. I figured if I got down and did not like what I was encountering I would add power and go back to the airport. In fact as I was on my final into the long straight unobstructed patch of firm tundra I was thinking this is not that bad. I got lots of room, when I was only 10-15 feet off the ground about to touch down that is when a gust of wind hit me from the left side of the airplane that stood the airplane on knife edge vertical to the ground. At that moment I added full power to fly out of it and to my surprise the airplane continued in an arc to the right.

Very sorry to hear the Bushwacker succumbed, Greg. I didn't know. I hope the rebuild is almost there.

I had a very similar experience this year, except we got lucky. The only difference was the severe gust threw us downward instead of twisting us sideways. Fortunately for us, we were flying fast enough and had enough altitude to recover from the dive before we hit the ground.

It was our third approach and we had already encountered gusts, but none this bad. I had prepared for tailwind gusts and we were flying at 65kts groundspeed - as fast as possible for this airstrip's length. The extra airspeed was enough to save the approach. In retrospect we should not have landed. We landed because my passenger's plane was waiting for him on the ground, but it could have stayed there overnight. We waited a long time before taking off again, we wanted to get the feel of the wind. It was blowing a steady 10kts up valley, but there were truely evil gusts of 30-40kts either up valley or down valley. This made takeoff from the 850ft airstrip a scary proposition. We made the take-off roll (low in ground effect) along the full length of the airstrip, to get maximum airspeed, then accellerated away in a shallow climb >100kts.

While we were cruising at 130kts everything felt manageble and under control. Just the usual uncomfortably heavy turbulence of a mountain valley on a very windy day. Flying low and slow near the ground revealed the true demonic nature of the wind. It was a frightening experience I don't want to repeat. It just goes to show the temptation to "get there" is very strong.

Flying home right behind a C180, then seeing it suddenly rocket upwards like it was on a string - that really helped me realise how much the turbulence throws your aircraft around. That was the first time I'd seen such bad turbulence acting on an aircraft from an external viewpoint. It was impressive how much they can endure.

Contact, I meant HAG anywhere from ground effect to a hundred feet or so. Due to search and rescue flying I too, have a good bit of time in ground effect -- not as much as you though. I also work on the flapping flight mechanics of articulated membrane wings in and out of ground effect (mostly in), so am somewhat familliar with its effect (I love bad puns, couldn't resist that).

Remember what I said about location and direction of flight relative to the core? If you miss the core, the horizontal shear will slide you more sideways. Boresight the core, and it just changes your airspeed. Increasing lift as you approach the core (due to extra airspeed), then suddenly decreased lift after you pass through it (due to reduced airspeed - no transverse shear if you boresight). It is the decrease in airspeed after passing through the core that will bust your butt. That's what got the Dallas airliner years ago

We have the Columbia River Gorge. My airport Troutdale KTTD is at the west end. It sounds similar to Lake Clark pass. This fall we have had several days with winds over 80 MPH in the gorge 9 miles east of my airport. No way will you find me out in those winds.

Cheers..Rob

Jim, I understand the physics. I just don't understand how in all that time, all day long in all seasons, I failed to experience that effect. I must have been in it some and the most powerful engine was the 235hp on the Pawnee. I lost 7,000 feet in less than a minute in a Tri-Pacer once. It was so rough I had little control, but it bottomed out on the desert floor. Good compression down there. With control, in less violent down air, I just pushed over getting through or at least to the big compression bump as quickly as practable.Going slow in the up air beyond more than made up the difference. Jim

"Good compression down there".

To make sure we are using the same definition for jargon terms, would you say a bit more about compression? We are talking about airspeeds that are in the incompressible aerodynamics regime, so I'd like to make sure we are using the word in the same way. Are you talking about the interplay between static and dynamic pressure that leave the total pressure unchanged?

Only way you can get transverse shear (side forces) when you are boresighting the core is when the flow is spinning (dust devil or pre-tornadic). But, if the flow is spinning, then the core flow is an updraft, not down, and the horizontal flow is an inwash, not outwash.

I've never deliberately boresighted a downwash (and don't plan to), but have landed a J3 in a direct tailwind caused by the outflow downwash from a thunderstorm (about 15 kts at my distance from the core) without noticing any transverse forces in play. Reason I landed downwind was that the storm would have been upon me before I reached the hangar had I taken time to go to the other end of the airstrip.