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Old Jun 27, 2012, 06:12 PM
Tossing planes into the snow
Canada, BC, Smithers
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Originally Posted by AA5BY View Post
An observed stall and lengthy rebuild is not a theory... it is a reality.
That is true, and it applies to all stalls, no matter what the cause. What I am hoping to do is to figure out how to avoid the stall in the first place, especially when turning downwind.
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Old Jun 27, 2012, 06:49 PM
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Originally Posted by Jovanx View Post
That is true, and it applies to all stalls, no matter what the cause. What I am hoping to do is to figure out how to avoid the stall in the first place, especially when turning downwind.
We all hope to figure it out and avoid them. I've suffered the down wind stall twice and in both a moderately strong cross wind existed in the face. That made the normally down wind leg, a cross wind leg and the base leg then became a down wind leg. I've never gotten into trouble with a strong wind down the runway... perhaps lucky.

What I learned from those two crashes and rebuilds of both, is to sense danger when a strong cross wind exist in the face. My adjustment for that danger is to fly the landing pattern differently.... to stay higher on what is normally the down wind leg, which then makes the turn onto base leg and final have a greater descent rate.

The last point to remember is that the base leg will have a much faster ground speed than normal so there will be a tendency to overshoot the turn onto final causing a harder than normal turn and danger level.

So... given a strong wind in the face at the field. Fly the pattern higher on the normal down wind leg and give the base leg a greater decent rate and then anticipate the need to make an earlier turn onto final. And... it helps if space permits to make the whole a gentle turn rather than two distinct turns.
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Old Jun 28, 2012, 01:25 PM
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Strange how free flight models never suffer the 'downwind turn', could it be because the RC pilot is standing still, and the free flight flier is running after his model.

This 'downwind turn' thing has been done to death so many times, there will always those who argue it no matter how many times the facts surface.

Buy a hot air balloon, fly in it on a windy day, climb above the clouds, (so you can't see the ground for reference), hand launch your plane and fly it round and round yourself.

Does it fall out the sky in a turn ?, like it does when you are standing on the ground and think in terms of ground speed and not airspeed ?

'nough said.
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Old Jun 28, 2012, 02:52 PM
Tossing planes into the snow
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Originally Posted by eflightray View Post
Does it fall out the sky in a turn ?, like it does when you are standing on the ground and think in terms of ground speed and not airspeed ?
There is no doubt that a large part of the problem is that the pilot misjudges the air speed, but there are other factors on windy days when you are near the ground. The example of the balloon is similar to the example of flying a mini-helicopter inside a moving train. They both remove wind from the picture, and are the equivalent of flying on a calm day.

As has been stated before, if the air mass is moving uniformly, as in the balloon example, and the pilot is moving at the same speed as the air, the problem disappears. That is a fundamentally different scenario than what happens near the ground on a windy day, where turbulence makes it more difficult to judge your air speed, and the pilot is not moving.

The purpose of this thread is not to figure out who is right and who is wrong, but to come up with some ideas of things to do or not do that will reduce the chances of it happening again.
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Old Jun 30, 2012, 07:10 AM
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United States, VA, Virginia Beach
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Originally Posted by Jovanx View Post
Zor, if you can find the time, your comments would be appreciated. It is only by understanding both sides of this issue, that we might all gain from the understanding, and our planes might crash less often. This forum has 2 purposes:

1 That we treat each other with respect.
2 We try to answer the question: "Given that it is widely believed that the downwind turn does not exist, why do people continually get themselves in trouble while trying to execute this maneuver?"
I agree. I would like to know. If there is misinformation or someone has a convoluted understanding (especially if it's me) I'd like to know so I don't tell some budding pilot wrong information.

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Originally Posted by Jovanx View Post
There is no doubt that a large part of the problem is that the pilot misjudges the air speed, but there are other factors on windy days when you are near the ground. The example of the balloon is similar to the example of flying a mini-helicopter inside a moving train. They both remove wind from the picture, and are the equivalent of flying on a calm day.

As has been stated before, if the air mass is moving uniformly, as in the balloon example, and the pilot is moving at the same speed as the air, the problem disappears. That is a fundamentally different scenario than what happens near the ground on a windy day, where turbulence makes it more difficult to judge your air speed, and the pilot is not moving.

The purpose of this thread is not to figure out who is right and who is wrong, but to come up with some ideas of things to do or not do that will reduce the chances of it happening again.
This!

I've had 2 crashes where I mislabeled it a downwind turn stall. It was actually me backing off the throttle due to a tailwind. Then when I came about into the wind the power was anemic and I lost my lift.

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but to come up with some ideas of things to do or not do that will reduce the chances of it happening again.
In my case it was to maintain throttle no matter what the planes speed looked like relative to the ground. I actually ran into this issue last Sunday when I flew a new plane, I consciously fought the urge to back off the throttle when flying downwind, when I made my turn the plane slowed to a crawl in the head wind, but I had enough power not to stall.
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Old Jul 02, 2012, 02:04 AM
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Ugh - "downwind" stalls or turns - really!

Forget all this drivel about air masses and Newton's theories about accelerating a mass - total bunk.

It's really easy for RC pilots! - FLY by frickin power and trim settings!!!! If your plane doesn't "fall" out of the sky upwind at a certain power and trim setting it won't "downwind"!!! STOP pulling the power and cranking it to make a normal pattern!!!!

THERE IS NO DOWNWIND!!!! (as far as the airplane knows)
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Old Jul 02, 2012, 03:01 AM
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Originally Posted by Hepdog View Post
Ugh - "downwind" stalls or turns - really!

Forget all this drivel about air masses and Newton's theories about accelerating a mass - total bunk.

It's really easy for RC pilots! - FLY by frickin power and trim settings!!!! If your plane doesn't "fall" out of the sky upwind at a certain power and trim setting it won't "downwind"!!! STOP pulling the power and cranking it to make a normal pattern!!!!

THERE IS NO DOWNWIND!!!! (as far as the airplane knows)
All those adjectives are unconvincing as they do no more than adorn an opinion. I've got one as well, and it concludes that if one is flying down wind and hit by a sudden gust, air speed drops. If one is flying cross wind to a strong wind and turns downwind... air speed drops. So, if flying cross wind at near minimum sustainable airspeed and turning down wind... the plane will likely find itself with inadequate air speed.

The solution of course is straightforward... airspeed before turning downwind should be sustainable air speed plus wind velocity.
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Old Jul 02, 2012, 09:24 AM
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Originally Posted by Hepdog View Post
Ugh - "downwind" stalls or turns - really!

Forget all this drivel about air masses and Newton's theories about accelerating a mass - total bunk.

It's really easy for RC pilots! - FLY by frickin power and trim settings!!!! If your plane doesn't "fall" out of the sky upwind at a certain power and trim setting it won't "downwind"!!! STOP pulling the power and cranking it to make a normal pattern!!!!

THERE IS NO DOWNWIND!!!! (as far as the airplane knows)
You say it's drivel yet you maintain the solution is to "FLY by frickin power and trim", so you agree they are real. If you believe they aren't then don't juice your plane in a downwind turn and see what happens.
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Old Jul 02, 2012, 12:25 PM
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Originally Posted by dedStik View Post
You say it's drivel yet you maintain the solution is to "FLY by frickin power and trim", so you agree they are real. If you believe they aren't then don't juice your plane in a downwind turn and see what happens.
Set up your planes like this and FLY like this and you will never have an issue no matter how windy/gusty/turbulent it is.

1. Take your plane up reasonably high and stall it in a landing configuration (gear and flaps etc) AND in a methodical fashion. By methodical I mean in a progressive fashion with incrementally lowered throttle settings and the bare minimum elevator pressure to hold level flight. This make take 2 or 3 passes to get it consistent. Take note of the throttle position and elevator required - do NOT care about the perceived ground speed.

2A. Trim your airplane for HANDS OFF level flight at a power setting above the stall. How much faster than the stall is up to you and the type of airplane. Floaty trainer types or lightly loaded high power 3D types don't need much margin - slick jets or anything highly loaded like heavy fast scale warbirds need quite a bit (1/4 throttle or more).

2B. Shim your motor (mounts/thrust tube) to eliminate as much climbing or descending with power changes as you can. Do NOT use the elevator trim to compensate except maybe one or two clicks provided you go back to 2A for landing. Most my planes with retracts and flaps have a landing trim change and I trim that out with each gear up/down change.

3 - Go up reasonably high again, set up in landing config (gear and flaps) and AT the low power setting from 2A, confirm the amount of bank you can turn at without inducing a stall. Do this methodically - I like to find out just how hard of a turn I can do so I keep trying it until it DOES stall. Most trainers won't stall at all - some warbirds have to be flown gently! NOTE the angle of bank and elevator required.

4 - FLY downwind and base leg at (or slightly above if you want) this power setting. The windier it is the faster the ground speed will be - DO NOT reduce power on downwind or base leg. Adjust your pattern by turning sooner but NOT harder (stall speed increases with angle of bank as in #3).

5 - Once established on final, start to lower the power and adjust as required. You shouldn't need to touch the elevator much. Let the plane fly the trim setting - throttle/power controls climb/descent - elevator controls airspeed!

6 - IF you are having trouble landing on your field (floating, too fast etc) then adjust the height of your pattern or the length of final but do NOT lower the power setting on downwind or base. Use the wind to your advantage once set up on final. A longer final gives more time to bleed off any excess airspeed.

Go out and try this. IF that sounds like too much work then that probably explains why you believe in this downwind turn bunk - you don't understand why/how your plane flys!

AS to "juicing it" on the downwind (or any x-wind etc) I fly all types in 30mph winds all the time - LOTS of fun! I've never noticed the need to juice it! The windier the better - makes landing heavy war birds alot easier.

BTW just because your airplane is bouncing around up and down does not mean the wing stalled and it "dropped" - that's just the natural order of things as your plane swims through the ocean of air which is rarely ever stable or constant. The ONLY reason people still think there is some magical phenomenon on the downwind to base turn causing stalls is they reduce power because of higher ground speed and then stall it themselves!
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Old Jul 02, 2012, 01:59 PM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
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Thank you Hepdog, for your well-put advice. These are the kind of responses I was hoping to get when I started this thread. It is a great list of do's and don'ts. Your advice about not turning too quickly is right on, and I also agree that the heavy warbirds are a lot easier to land into a stiff wind.
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Old Jul 02, 2012, 04:17 PM
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I'm not sure everyone is on the same page regarding what wind speed condition we are thinking when offering a perspective. When wind velocity is light, I don't see much problems. When the velocity is 12-18 there is no doubt for me that there is danger of stalling.
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Old Jul 02, 2012, 05:10 PM
Tossing planes into the snow
Canada, BC, Smithers
Joined Nov 2011
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Here is the kind of wind I am talking about. I don't have a wind-guage, so I can't give real numbers, but when you can basically "hover" the plane for a few seconds then you are there. I am not talking about a 3D plane that is made to hover, but just a basic plane flying into a strong headwind. This is not a situation that would often be encountered by a full-scale airplane pilot, because the typical stall-speed of a real airplane is usually much larger than the wind speed.
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Old Jul 02, 2012, 05:30 PM
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The only issue with Hepdogs setup is your plane is now trimmed for straight and level flight near stall, you will have to fight down elevator for anything much over stall speed. Or am I wrong in thinking that.

I've always trimmed my planes for cruise speed, not wide open and not below cruise speed.

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Originally Posted by Hepdog View Post
The ONLY reason people still think there is some magical phenomenon on the downwind to base turn causing stalls is they reduce power because of higher ground speed and then stall it themselves!
We established that pages ago. I know as I've done it twice and it took me days after the second crash to admit it was the cause of that one and a previous one.

I think one of the hardest things in this hobby is to admit we are at fault for something.
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Old Jul 03, 2012, 12:48 AM
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Originally Posted by dedStik View Post
The only issue with Hepdogs setup is your plane is now trimmed for straight and level flight near stall, you will have to fight down elevator for anything much over stall speed. Or am I wrong in thinking that.

I've always trimmed my planes for cruise speed, not wide open and not below cruise speed.

I think one of the hardest things in this hobby is to admit we are at fault for something.
Don't trim for stall speed! Trim for a power setting comfortably above that - but not cruise power either (unless you want to fly the circuit at cruise power - not impossible just alot faster than required).

The "climb under power" problem can be largely mitigated with more motor down thrust - but not eliminated. One could certainly adjust the trim in flight for various power settings - JUST like real pilots - but if you're comfortable doing that you likely don't need to worry about going too slow downwind (cuz you know what you are doing!) One bonus to climb under power is if you get into trouble on final and go full throttle it climbs naturally.

IF you want to get fancy (and have the radio for it) put in a down trim mix to power setting increase - I've had to do that on some "unusual flying machines".
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Old Jul 03, 2012, 12:54 AM
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Originally Posted by Jovanx View Post
Here is the kind of wind I am talking about. I don't have a wind-guage, so I can't give real numbers, but when you can basically "hover" the plane for a few seconds then you are there. I am not talking about a 3D plane that is made to hover, but just a basic plane flying into a strong headwind. This is not a situation that would often be encountered by a full-scale airplane pilot, because the typical stall-speed of a real airplane is usually much larger than the wind speed.
I like to do vertical circuits in those winds. Take off - climb straight out and up and then pull the power back while holding lots of up elevator in. If it's windy enough the plane "backs up" across the field to where I can reduce power and land back where I started! All without ever turning.

BTW this can and has been done in real airplanes. I learned to fly in a Cessna 150 on the prairies. Light enough the stall was about 40 knots - 35 with flaps and gentle touch - well within the normal winds so long as it was right down the runway. Of course we went a little higher before trying to go backwards but the stall was so gentle it really wasn't that dangerous.
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