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  #1  
Old 05-10-2021, 08:50 AM
pvalovich pvalovich is offline
 
Join Date: Dec 2005
Location: Ridgecrest, CA
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Default Split Flaps Flight Testing

After reading a recent Tip of the Week, during recent preflight of my -8A came up with the question of what would happen if for some unlikely reason, one of the flaps came loose while approaching or in the landing pattern.

Has anyone had any experience - or conducted split flaps flight testing?
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  #2  
Old 05-10-2021, 08:54 AM
gassman gassman is offline
 
Join Date: Jul 2016
Location: Stanton, mi
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My buddy had this happen in an apache. After takeoff he raised the flaps and one stuck for a little bit. He said one wing got really heavy before he discovered what was going on. He was just gonna put them back down before it popped up and all was well. I van imagine things would get very interesting in a full flap situation
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  #3  
Old 05-10-2021, 09:18 AM
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chepburn chepburn is offline
 
Join Date: Apr 2006
Location: Ottawa , Canada
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Default

Quote:
Originally Posted by pvalovich View Post
After reading a recent Tip of the Week, during recent preflight of my -8A came up with the question of what would happen if for some unlikely reason, one of the flaps came loose while approaching or in the landing pattern.

Has anyone had any experience - or conducted split flaps flight testing?
First:
Do NOT try that.
Second:
Its not the same aircraft, (not even close really) but I did an accident investigation of a DHC-6 (Twin Otter) where the flap rod connection broke on final approach. This resulted in an uncontrollable roll and crash into the ocean. There will be a very high roll rate with one flap floating and one flap down. It is unlikely you will be able to overcome the roll rate with aileron even if you recognize in time what has happened to raise the lowered flap.
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  #4  
Old 05-10-2021, 09:41 AM
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Tandem46 Tandem46 is offline
 
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Default

Quote:
Originally Posted by pvalovich View Post

Has anyone had any experienceÖ.
https://vansairforce.net/community/s...ad.php?t=35894
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  #5  
Old 05-10-2021, 04:04 PM
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n82rb n82rb is offline
 
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I had it happen in my twin Comanche on a go around one stuck about half way up. Luckily Comanche flaps donít come up really fast and I noticed the roll coming in as I brought them up and identified it immediately. I just stopped bringing them up and matched the m up and came around and landed.
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  #6  
Old 05-10-2021, 05:40 PM
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flightlogic flightlogic is offline
 
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Default somewhat related

A build item to think about. I note that many builders have elected to use the solid HEX rod to push flaps down. On my 9A, I swapped them out after thinking just how fast that bird would roll, if a hollow tube collapsed or cracked at the threads.
I suspect if this occurred within 300 ft. of the ground, it would not be survivable.
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  #7  
Old 05-10-2021, 10:26 PM
JDeanda JDeanda is offline
 
Join Date: Apr 2013
Location: Ventura, CA
Posts: 261
Default Flap Asymmetry

I don’t know of anyone trying this on purpose. Doing so sounds a little like practicing bleeding. What actually happens depends how much roll authority is available at the current airspeed and configuration. I had a friend experience a flap asymmetry in a Grumman AA-5A Cheetah and he said it flew OK as long as he kept the speed down. He landed normally. I was in the back of a Lockheed C-5 one night that had an asymmetry. I noticed some rolling back and forth but the crew got it under control and we landed normally. They got on a maintenance stand and came down saying the airplane was pretty damaged and was headed off to a depot maintenance facility. My favorite was a Service Bulletin from Bellanca about breaking flap cables, which would allow the affected flap to retract violently. It said “This condition, while undesirable, is controllable.” My sense is that any of our RVs with their very effective ailerons and relatively high roll rates should be controllable with one flap extended, but I have no intention of trying it out on purpose. My CFI wife teaches her students to only move the flaps when the wings are level, just to hopefully make it easier to deal with an asymmetry.
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  #8  
Old 05-14-2021, 05:48 AM
chopperchops chopperchops is offline
 
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Location: Brisbane, Queensland, Australia
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Quote:
Originally Posted by n82rb View Post
I had it happen in my twin Comanche on a go around one stuck about half way up. Luckily Comanche flaps donít come up really fast and I noticed the roll coming in as I brought them up and identified it immediately. I just stopped bringing them up and matched the m up and came around and landed.
My father had one stick full down on his twin Comanche on takeoff. Sadly it didnít end well.
PLEASE donít try this!
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  #9  
Old 05-14-2021, 11:19 AM
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Ironflight Ironflight is offline
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Ever since I saw Paul’s (the OP) post, I have been thinking about how to do this testing, just to see what kind of rolling moment you’d get, and how much aileron it would take to counteract it. I suppose you could disconnect one flap and remove the pushrod, then use speed tape to tape the flap up (its going to want to trail in flight anyway). Then you get to altitude with flaps up, establish level conditions, and deploy just a tiny amount of flap and see the result. Add a little more, see the result. Record stick forces in roll with a fish scale maybe.

With a good test plan and safety analysis, you could get some great data for the community! Tip of the hat to Chris for the modeling, but in this case, I think you’d need test data to back up the analysis....which would be interesting to compare in itself.

WARNING - this is a thought experiment, and if someone would want to try it, they need to be a VERY experienced test pilot with a deep background in flight test safety!

Paul
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  #10  
Old 05-14-2021, 11:33 AM
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Mel Mel is offline
 
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Quote:
Originally Posted by Ironflight View Post
WARNING - this is a thought experiment, and if someone would want to try it, they need to be a VERY experienced test pilot with a deep background in flight test safety!
Paul
AND A PARACHUTE! Of course, that would go without saying. This would already be on the checklist for an experienced test-pilot.
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