Split Flaps

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pelmet
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Split Flaps

Post by pelmet »

Have heard of a couple of split flap situations on trainer aircraft lately including one that crashed. Almost makes me wonder if partial flap landings in some aircraft might be a good idea. Here is what a split flaps situation can do......

https://www.youtube.com/watch?v=WzPTg86r9aw
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telex
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Re: Split Flaps

Post by telex »

pelmet wrote: Tue Nov 10, 2020 6:17 pm Have heard of a couple of split flap situations on trainer aircraft lately including one that crashed. Almost makes me wonder if partial flap landings in some aircraft might be a good idea. Here is what a split flaps situation can do......

https://www.youtube.com/watch?v=WzPTg86r9aw
Based on the video maybe a split flap take off "checklist" would be a good idea?

Some manufacturers have produced checklists for all flaps up landing, trailing edge flaps up, flap asymmetry, and flap disagree.

Did you have any thoughts on "some aircraft" benefitting?
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Last edited by telex on Wed Nov 11, 2020 12:41 am, edited 1 time in total.
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PilotDAR
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Re: Split Flaps

Post by PilotDAR »

There are a couple of Piper twins I know of for which flap extension is suggested to be incremental, in case the flaps split. Otherwise I think that flap asymmetry in GA types is happily very rare. 100 series Cessnas can jam a flap part way if the track to shroud clip is broken (I've had it happen) detectable during a walk around, and does not result in asymmetry, just jamming around 20. Operating flaps incrementally, rather than all at once, is a good plan in any case.
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digits_
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Re: Split Flaps

Post by digits_ »

PilotDAR wrote: Tue Nov 10, 2020 8:38 pm There are a couple of Piper twins I know of for which flap extension is suggested to be incremental, in case the flaps split. Otherwise I think that flap asymmetry in GA types is happily very rare. 100 series Cessnas can jam a flap part way if the track to shroud clip is broken (I've had it happen) detectable during a walk around, and does not result in asymmetry, just jamming around 20. Operating flaps incrementally, rather than all at once, is a good plan in any case.
Are there any certification requirements with regards to aileron control and full flap assymetry? I believe navajos publish 86% loss of aileron control with full flap symmetry and a metro something like 98%.
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PilotDAR
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Re: Split Flaps

Post by PilotDAR »

Are there any certification requirements with regards to aileron control and full flap assymetry?
Not for GA planes. I've heard the stories about Navajos, and was warned when I flew them. I very much doubt that you could maintain roll control with any more than the slightest asymmetry. It's certainly not something demonstrated during certification.

In my early days flying Aztecs, we took off from Buttonville one night, and on climb out, as we sped up, it was rolling. Controllable, but rolling. We knew this airplane very well, and it had been fine the last flight. The flaps appeared symmertical, and when we cautiously extended them, roll was better. Once back on the ramp, we checked it over really carefully. Someone had bumped the trailing edge of the flap outboard of the step (briefcase, perhaps), and that damage acted like a tiny trim tab, and flew the flap higher within its freeplay, that was all it took to be annoying. The plane was flyable the whole time, but with some annoying effort. I can't imagine flying with several degrees of asymmetry, based upon what I learned that night!
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Re: Split Flaps

Post by valleyboy »

The craziest thing that happened to me was in the herc sim during my initial training. The instructor froz one side flap at about 400 ft with flap retraction and we simply rolled it up in a ball. Thanking the gods for the freeze button. You much remember it needed 2 system failures to do this and the likely hood of it ever happening was infinitesimal. Good demonstration though.

The DC3 most companies required flap full selected around 300 to 400 feet on final in case of a flap rod failure. In boeing jets flap position is always called out for both indication needles verbally, specifically looking for split flap. All large aircraft have split flap indication and flap lockout systems. Except for maybe the very old built prior to 1950.

So to answer the question -- no, performance is based on landing flap configurations. I don't even cut back on flaps in xwind, the dc3 was always landed at full flap no matter what the xwind for me.

It depends on the aircraft, the 727 I never landed at full flap but at recommended landing flap. Full flap was landing weight restricted and locked out with noise modes, so why even consider it
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