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Can you name four types of flaps?

Can you name four types of flaps?

Don’t feel bad if you can’t; you are not alone.  And did you know that your plane will react to the flap deployment differently depending on the type of flap you have on your plane.  For a quick rundown on these all important features, read on and see what Klaus Ronge has to say about how flaps will change the way your plane lands.

There are four basic types of flaps: plain, split, Fowler and slotted. The plain flap is simply a hinged portion of the trailing edge. Split type flaps are hinged at the bottom of the wing and create much more drag than plain flaps. The slotted flap is similar to a plain flap, but has a slot between the wing’s trailing edge and the flap. The air passing through the slot delays the airflow separation and creates a greater increase in lift with a smaller increase in drag than a plain or split flap. Fowler flaps extend aft and down increasing the wings area and provide large increases in lift with a minimum of drag.

Plain flaps lower the wing’s trailing edge increasing its curvature and, therefore, its lift.

Split flaps generate a lot of drag by disturbing the airflow on the underside of the wing.

Fowler flaps move rearward and downward increasing the wing area and curvature.

 

Slotted flaps allow high-energy air to flow from underneath the wing up and over the flap to help prevent airflow separation.

Deflecting flaps will cause a twisting action to the airplanes’ wing. The type of flap as well as the wing’s design will determine the amount of twisting action, with the split flap generating the least amount. Deploying the flaps may result in the plane pitching up or pitching down. The elevator must be used to compensate and keep the plane on the desired approach path. Another characteristic of flaps is that the first half of the flap’s deflection results in a greater increase in lift while the second half results in a greater increase in drag. Flaps also impart a large structural load on the plane and should only be used at a lower airspeed. Full-size planes have their air speed indicators marked for safe flap operating range.

YOU MAY BE SURPRISED HOW MUCH ELEVATOR CORRECTION IT TAKES TO COMPENSATE FOR FULL FLAP DEFLECTION

Updated: July 16, 2015 — 4:07 PM

16 Comments

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  1. Are not the picture of the slotted and plain flaps swapped?

  2. It all looks good to me…
    After the fix…
    Nice catch Jim, looks like I need to study up on my flaps. 🙂

  3. I knew it…AF A/C mechanic,F4, F105, C141m C5A

  4. “Another characteristic of flaps is that the first half of the flap’s deflection results in a greater increase in lift while the second half results in a greater increase in drag.” Remember this! Although you must lower your airspeed before deploying flaps, you will need to increase power as you add more flap to maintain flying speed. I forgot this basic fact a while ago and my Hangar 9 Twin Otter stalled suddenly and is now a pile of junk.

    1. To clarify your comment….Saying the “first half” is a relative term, you are correct but need some quantifiers. The first 20 degrees of flaps creates more lift than drag, 20+ creates more drag than lift. For example, a jet uses small deflection ( about 15 degrees max) for takeoff, but uses max deflection for creating the needed drag for landing. 30 degrees has the same amount of lift, but much more drag than 20 degrees.

  5. Did the B52D have Fowler Flaps?

    1. Yes the B-52 has Fowler flaps.

  6. Sorry Jim, they are not switched, the plain flap is hinged, with no gap, the slotted flap allows air to accelerate through a gap between the flap and the slot lip immediately prior to the flap’s leading edge, as is shown in the diagram. You, (and anyone else)
    can check out a great Technical Report on the NASA Tech report server…look for NACA TR 664. There is a fifth flap that is not mentioned here….the Youngman Flap which Fairey Aircraft of Britain used.

  7. And it took 60 seconds to fully deploy/retract the B-52 flaps!

  8. Flaps were not something I ever built into a plane or used if they were already installed but after being involved with Scale war birds for a few years, Flaps are really needed for a slower, normal speed landing. All my planes pitch up just for a few seconds at 1/3 throttle on the down leg of landing approach but settle right in for a great landing speed.. But I leave that throttle up a few clicks till right before touch down to avoid stall as I found out on my P 51..

  9. There are, of course variations, the most effective of which is the Slotted Fowler Flap. This is the type of flap used on almost all jet airliners. Early Boeing jetliners used a triple-slotted Fowler flap. The B-727 used a combination of triple-slotted Fowler flaps on the trailing edge with slotted leading edge slats on the outboard portion of the leading edge and Krueger flaps on the inboard section of the LE. We used to joke that on approach, a 727 pilot didn’t call, for example, for “Flaps 50”, he asked instead for “50% wing disassembly.”

  10. What category are flaperons, or are they sub-category of only types listed:1and 4?

  11. An important thing to remember is to slow the movement of the flaps down if possible. You can use your radio if it has this function or after market controllers that slow the servo motor. If you do this, many times you won’t have the large ballooning effect you would if the flaps go “Boing!” In one quick movement. Besides, it just looks cool deploying slow.

  12. I find this very interesting and informative. I just called them regular flaps or roll-top desk type flaps when talking about my Duane Habets Air Tractor 502. That plane has the most awesome flaps I own. I guess they would have to come under the Fowler Flap title, because they roll out and down and not just a pivot place. I believe all flaps should have a 3-Position switch for No Flap, Half Flap and Full Flap. I just don’t like rotating a dial and trying to fly at the same time.

    I recently bought the Habu 2, which has flaps and is made for retracts as well. My Spectrum DX-6i doesn’t have a 3-way switch, so I am going to have to spend some more money on a new Transmitter…most likely the DX-9 which talks to the pilot so ya don’t have to look down to see what it has done. $450.00 for that TX the last time I checked.

    Thank you very much for the information on the flaps. I think we should have more air brakes on our planes, like the F-86 on the side and the F-15 on the top. It only makes sense to have air brakes on a plane, since I used to drive trucks with air brakes and I never got off the ground in any of those, thank Heavens. Ha! Ha!

  13. Jim Dozet, no the pictures are correct.

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