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Old 05-19-2013 | 09:19 AM
  #26  
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Default RE: Tip Stall

Excellent thread and I hope more people read it!
Old 05-19-2013 | 10:19 AM
  #27  
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Default RE: Tip Stall


ORIGINAL: Bozarth


ORIGINAL: essyou35

?? G force doesn't make you maintain level flight. As for the rest of your post no idea what you are saying.

Oh, but it does. A tad shy of 2 g's at 60 degrees of bank and you will descend. A tad too much pull (more than 2 g's) at 60 degrees and you will climb. Trigonometry at it's finest.

Kurt
It all depends on the angle of thrust. One can make a "level turn" at 90 degress bank with enough up thrust. And depending on how hard you pull the elevator you can get a 2G turn or a 9G turn.

It's all about the forces on the aircraft - ALL OF THEM.
Old 05-19-2013 | 11:28 AM
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Default RE: Tip Stall

There is quite a story about the ultimately simple appearing solution to the problem of one wing stalling during approach with the F-4U Corsair.

Jess
Old 05-19-2013 | 01:27 PM
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Default RE: Tip Stall

Hi Gerryndennis,
I wasn't replying to you so much as just adding what I know (or think I know) to the thread. It's a very interesting topic. Thanks for your reply, it goes to show how little I know.
Cheers.
Old 05-19-2013 | 02:35 PM
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Default RE: Tip Stall

Could someone tell me how to tell the difference between an asymmetric stall and a tip stall. What are the visible differences.
Old 05-19-2013 | 04:38 PM
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Default RE: Tip Stall

ORIGINAL: FLYMAD

Could someone tell me how to tell the difference between an asymmetric stall and a tip stall. What are the visible differences.
In an asymmetric stall (stall developing from the root) the wing will drop and a spin may develop if no correction is made.

In an asymmetric stall (stall developing from the tip) the wing will drop and a spin may develop if no correction is made... much more violently and quickly.

In an asymmetric stall (stall developing from the root) aileron (gentle) will at least reduce the roll and may be sufficient to prevent the wing drop.

In an asymmetric stall (stall developing from the tip) aileron will make the wing drop worse.... much worse.

Flymad you're post said 'in reply to... me' in the bottom right hand corner, which is why I wondered.

Dave H
Old 05-19-2013 | 05:18 PM
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Default RE: Tip Stall


ORIGINAL: Rob2160


ORIGINAL: gerryndennis


My advice to all modellers is stall your model lots,<span style=''color: rgb(255, 0, 0);''>get used to where the elevator stick is when it stalls. Every time you put the stick in that position your model will stall</span>. If you find yourself turning final low and slow or making a tight turn and you notice that the Angle of Attack (elevator) stick is near the stall position then be aware that you are near the stall. Speed or angles (bank or climb or descent) are irrelevant.

Not quite 100% true in theory but close enough in practice.

Dave H
The wisest words written in this thread, . Yes this was the most fundamental concept we would teach aerobatic students.. Your elevator is an angle of attack control device.. the wing always stalls at the same critical angle and therefore the elevator joystick (RC or fullsize) will be in the same position each time you stall.. if stall is encountered, you only need a few mm forward stick to unstall..

Very refreshing to see someone else say this.. Ahh.. New Zealander... Ex RNZAF?

Well I've never been accused of being wise in here before, usually when I post something that doesn't match the accepted wisdom I get ignored, so thank you. And yes to both, you? RAAF?

I agree totally with your 'elevator is a (the?) angle of attack control device' concept but I wasn't allowed to call it the 'joy stick'. Sort of a 'this is my rifle, this is my gun, this is for shooting, this is for fun' argument for using correct terminology (military's funny like that).

My first flight with a civilian instructor included 30 minutes of basic stall instruction as part of the type rating (light twin) and then a demo of the recovery. When it was my turn I checked forward, increased power, and climbed away. 'What the hell was that' he yelled 'you'll re stall if you recover like that, you need to go for speed'.

I pointed out that if speed was the important thing then what was the point of the last 20 minutes (that I was paying for) demonstrating all the (angle of attack related) stall symptoms. And how would his recovery work at 300' turning finals from a circling approach, you guessed it his speed based recovery took 300', mine 30' (yeah I know but it was my first touch of the stick, sorry sir, control wheel).

To give him his due he did accept that he had been teaching it all wrong, especially after I showed him some accelerated stall recoveries (2G /60 bank, 90 bank and about 30 kts in a wing over). Doubt that he's been able to convince CAA to change the syllabus though.

Where do you teach aero's?

Dave H

Old 05-19-2013 | 05:43 PM
  #33  
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Default RE: Tip Stall

ORIGINAL: essyou35

?? G force doesn't make you maintain level flight. As for the rest of your post no idea what you are saying.
Nothing "makes" one maintain level flight. OTOH, should one (pilot) decide to maintain level flight then that someone has to follow the laws of nature such as lift equal to weight.
To produce lift in subsonic convergence airflow, one has to provide the airflow with needed pressure variations to attain the needed forces. Given a wing in a 60° bank relative to earth, at I G loading will be 1 G short of the required aerodynamic force required to maintain level flight.

Should you not understand these basic lift/drag/etc. aerodynamic truths, I certainly agree that you would have absolutely NO IDEA of what I was/am saying.
Old 05-19-2013 | 06:13 PM
  #34  
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Default RE: Tip Stall


ORIGINAL: Rob2160
The aircraft will NEVER stall by itself..... A stall will never just Happen to you.. It is a result of what you are doing wtih the elevator. any aircraft will stall if you apply too much elevator..

Depending on a number of factors (control throw, CofG, wing shape, elevator size etc) the elevator position for the stall may be 30% deflection or it may be 90% deflection, but for a given aircraft, and without changing the CofG, the elevator position will always be the same .

The tapered wings will usually stall at the tips first,

When I hear people say.. "The plane just stalled on me, the true answer is.. NO.. you stalled the airplane by using too much elevator... you just may not have realised you were doing it"
Don't disagree. But if you had read before you pounced you would have seen my comment that Iwas practicing low powder flight to see what it would do beforeand afterentering a stall. Most models don' t come with a pilots operating handbook behind the seat stating the stall speed so you have to find out emperically. To do that you reduce throttle and maintain altitude with elevator. This isn't my first rodeo, either.
Old 05-20-2013 | 03:10 AM
  #35  
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Default RE: Tip Stall

ORIGINAL: Hossfly

ORIGINAL: essyou35

?? G force doesn't make you maintain level flight. As for the rest of your post no idea what you are saying.
Nothing ''makes'' one maintain level flight. OTOH, should one (pilot) decide to maintain level flight then that someone has to follow the laws of nature such as lift equal to weight.
To produce lift in subsonic convergence airflow, one has to provide the airflow with needed pressure variations to attain the needed forces. Given a wing in a 60° bank relative to earth, at I G loading will be 1 G short of the required aerodynamic force required to maintain level flight.

Should you not understand these basic lift/drag/etc. aerodynamic truths, I certainly agree that you would have absolutely NO IDEA of what I was/am saying.
This is why I preach so much about the greatness of light weight airframes, the lower the wing loading is, the less one must worry about those nasty tip stalls, on the stuff I build and fly for the most part there is no tip stall characteristics to think about at all; so I am left to just play and have fun, but many times when ever I fly somebody else’s airplane especially warbirds; I must manage my available energy throughout the flight envelope to keep things on the ball. For this very reason I believe warbird pilots are better pilots than most 3D pilots, warbird guys deal with these issues due to higher wing loadings all the time, and the ones that don't manage the energy very well... Crash and burn.

Bob
Old 05-20-2013 | 10:15 AM
  #36  
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Default RE: Tip Stall

After fooling about with aviation for some time now. Full scale and flying models. I have never encountered a beginner wanting to know all the ins and outs of aero dynamics. Most new folks, also known as beginners know if the tip of the wing hits the big ball, also know as the earth, it is a bad thing. Now I do think the beginners that come to this section of RCU do enjoy all this going ons about what make one of these things fly. What I have found out is some pilots are better flyer because of the planes they fly. I also discovered who is the best pilots depends on who is doing the telling. Like one of the new dudes told me yesterday on the flight line. "Mr Jerry, some of these people are real serious about all this"
Old 05-21-2013 | 03:51 AM
  #37  
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Default RE: Tip Stall

Serious? Did you ever go to an RC show where everythign is there? Watch closely at the RC Tank folks. Now that's serious.. almost scary!! [X(]

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