Landing w/ Flaps? - RC Groups
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Feb 23, 2007, 10:31 AM
Registered User

Landing w/ Flaps?

Hi All,
I converted a .60 sized P-51 to electric and had a really bad landing on the maiden. It's the World Models Mustang and it has flaps. On the maiden, I put the flaps down while high up in the air to see what she would do - which was pitching up or down. I was cruising pretty fast when I tried it and I'm wondering if I should have tried it at slow speeds. Would that have a different effect.

Also - I'd love to hear from Warbird owners who have flaps and can tell me what I should do. Thanks so much!!
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Feb 23, 2007, 11:08 AM
Registered User
How much flap travel did you have. I'd suggest at least 40 degrees.

When landing with flaps you will need more power on than you're used to. If you try to kill the power the extra drag will make the plane fall out of the sky. I generally recommend not landing with flaps until you've gotten used to the model. If you can't land without flaps, you're not going to be able to land with them. The main reason flaps are used is to increase the descent angle. Warbirds will fly slower with flaps but be careful to not slow down too much. As you appear to have discovered, flaps are not a magic anti-stall device. Hence the need to get a few landings in before you go to flaps.

I've seen many .60 sized P-51 fly and they really don't even need flaps. Just keep the airspeed up touch the mains down first.
Feb 23, 2007, 01:03 PM
jrb's Avatar
The best flap landings (very scale like) that Iíve ever seen with any RC model are by the large gas (not glow) powered Corsairs!

Several of my RC buddies have these large Corsairs (80+Ē, Byron); maybe itís the inverted gull wing, or just the right wing loading???

It really makes you want one!

All others seem to land virtually the same w&w/o flaps.
Feb 23, 2007, 01:03 PM
Registered User
elfwreck's Avatar
Hey now,
Another anoying thing with flaps; they tend to tipstall and get some wing rock when deployed. I've gotten around this by using the glider guider trick of using "crow". My flaps drop as close to 90* as possible, my ailerons raise around 20-30* and I dial in some down elevator to keep from "balooning".

The added wash in from the raised ailerons adds a lot of stability, even if it isn't quite as scale, and I can come in at a crawl.
Of course you'd want to try this out at serious altitude it takes a little practice and tuning to get it right.
Feb 23, 2007, 02:09 PM
Registered User
dusmmdb34's Avatar
When using flaps, do most mix in elevator?
Feb 23, 2007, 03:11 PM
Registered User
My flap travel is about 40-45 degrees. I've used flaps on a B-17 I had and I had to mix in down elevator, but that was an easy glider compared to this thing.
Feb 23, 2007, 04:03 PM
Registered User
Jimbo45cn's Avatar
If my parts come in today I am going to remaiden my A 26 tommorow. I also have flaps on this one, but frankly have been kind of hesitant to deploy them as of yet. Any advice? My A 26 is a Wing mfg kit, right about 7lbs auw, 65 " ws. Jim
Feb 23, 2007, 04:35 PM
Registered User
Deploy the flaps up high and then slow down until the model stalls. That will give you an ide of how slow and at what angle the model will stall at. With such a light wing loading, the model should really float in.
Feb 23, 2007, 04:46 PM
Deletedfor proving Nauga wrong
There may be some confusion going on... (re the first poster's Mustang)

Is the particular model equipped for separate control surfaces near the wing root acting as flaps and independant aileron surfaces?

Deploying "flaps" in the flaperon mode can and will cause low speed instability when flying a mustang. The taper of the wing virtually guarantees it.

If the full span control surfaces going down changes the effective AOA at the tip more than at the root, you have effectively added "washin" which causes the wing to stall at the tip first. That is EXACTLY what you do not want. The plane flips over ind without altitude available, recovery is impossible.

With the separate surfaces for ailerons and flap, the center section surfaces going down increases center section AOA without changing the tip AOA, that effectively adds washout, making the center stall before the wingtip. This produces a stall that is more likely to have the plane continue relatively straight and level rather than flipping over.

A Mustang bennefits from a small amount of flaps on takeoff, to add the effective washout. Large deflection is to help prevent speed build-up durring descent and continues to help slow the plane after touchdown.

The slowing effect on final approach when using large flap deflection can have the plane lose more airspeed than you really desired. Due to only having the visual cues to how the model is doing, you can miss the indication that the center section of the wing is stalling when descending on purpose, slightly nose up with power on. (the way some people do thier approaches)

If you do a nose-up power on approach, you need to practice slow flight in that attitude and find what power just holds altitude. Less power than that when configured "dirty" is likely to cause a stall even in a landing approach descent. Chop power as you flair.

Most warbirds are unforgiving of landing approach errors. The P-51 is a prime example.


RE the A-26 ... Separate surface flaps can help, just as with any other warbird.

Take it high.

Slow it down.

Apply a little bit of flaps at a time. Do a figure 8 traffic pattern... more flap. Repeat the figure 8.

If you have the mix capability, set up a switch that yanks up the flaps regardless of the dial setting. Then if there is a problem with flaps down, you can get them up without fiddling around for the recovery. Full flaps down and a spin can be difficult to get out of. (even though it should be harder to make the plane spin with flaps down)

Do your experiments with plenty of altitude to recover from a 3 turn spin with the allowance for a mis-correction causing a second spin.

And.. on the twin. If you lose one engine on takeoff.. get the nose down. Pulling up is a virtually guaranteed crash.

(remaiden implies it flew and got broke...)


Some planes nose down with flaps.

Some planes nose up

Some are pitch neutral.

That is dependant on the airfoil used and the % chord used by the flap surface.


added note:

Crow mix is to partly help counter the added lift of the flaps and partly to counter the pitch effect in some cases. It also adds more airbrake effect and virtually eliminates the chance of adverse yaw if you do use the ailerons.

Crow is not necessary but can be useful. Its use is definitely not scale ona WWI fighter or bomber.
Last edited by fhhuber506771; Feb 23, 2007 at 04:57 PM. Reason: found more typos...
Feb 23, 2007, 04:50 PM
Scale Builder, RCAPA #29
Rob Schaffer's Avatar
Flaps,... lots of discussion here and there about them on RCU and here on the Ezone,.. a search might lend other insight, but here is mine.

Currently, I am flying a Top Flite Corsair with Flaps. I have them setup on a three position switch so I can get the same predictable result each time, which I feel is much better than a dial setup.

When testing flaps, I find that you should be about 100 to 150 feet up, and around 1/2 throttle. Drop your flaps when you are flying level and into the wind, and see what happens. If you roll a little to one side, then you possibly aren't getting the same travel on each side. While you may measure the same on the ground, be sure there isn't slop in the linkage, as there will be air pressure on them when flying.

Also, note if you pitch up or down. My corsair pitches a little at 50% flap, but there isn't a change when I go to full flap. You can correct this with a mix if you would like. For example, I drop retracts on my final pass, do a visual check, and then turn on the downwind leg. Drop flaps 50% with a little mix of elevator while on the downwind leg. Turn onto final approach and into the wind,... drop flaps to full -- NO Change in throttle.

Your decent is controlled by the throttle when at full flap,.. as the flaps are causing drag. Lower the throttle smootly from 1/2 to a little less,... then slowly apply a little more as you get close to the ground. DO NOT PUNCH the throttle,.. you'll torque to much and roll right over if you do.

Nice smooth landings are a practice of a consistant flap setting, with the proper throttle setting to make a nice smooth approach. Very little flair at the end of the decent just before she touches down.
Feb 23, 2007, 05:46 PM
Registered User
Jimbo45cn's Avatar
Thanks guys. Yes, the A 26 flew and then I lost a motor on the second flight and it went in. Not horrible as I was able to repair, but a crash none the less. My flaps are on a switch, full up, about 35 degrees(I'm guessing here) then about 75 degrees. It does float, but not as much as you would think. Jim
Feb 23, 2007, 06:07 PM
Deletedfor proving Nauga wrong
I also have an e-power twin, which had a single-motor-out incident.

I should have taken the downwind landing. I was at the wrong end of the flying field, high enough for easy recovery when one motor died.
(I should have paid attention to which motor... and planned all turns accordingly)
Dropped throttle to 0 and was gliding back.
Applied throttle to stretch and both ran.
I tried to stretch for a normal approach... just as I started turn to base, the motor on the low wing died. (I could have set up the turns to go right instead of left...)
The running motor pulled the nose around to point straight down.

If the tree hadn't been there... I would have had enough altitude to pull out and land. I was JUST a little further out than I thought. Even though I was expecting the motor t die... there just wasn't room to avoid the tree.

3 things wrong... Motor acting up. Not paying attention to which motor. Trying to stretch out the flight when somethings wrong. Add the tree in the wrong place for "Strike Four" Airplanes don't survive four strikes.

That tree no longer exists... It had been "catching" too many planes.


I got lucky. The fuselage and one wing were virtually unscathed. Snapped one wing panel. It will fly again.
Feb 23, 2007, 07:15 PM
Registered User
So should I trying landing my P-51 with a little flaps, or should I go full deflection. I will certainly try everything up in the air and do a couple of high altitude practice landings and see what the results are from my flaps at different degrees. sounds like full flaps (40 degrees) will bring it down nice and smooth while power is still on.
Feb 23, 2007, 08:41 PM
Deletedfor proving Nauga wrong
small deflection will be more like what you are used to with a trainer (assuming its not flaperons) It won't be the same... but its less likely to get you in trouble.

needing to "go around" and being at full flaps can be dangerous. The flaps make it hard to gain airspeed. Proceedure (full scale aircraft) is usually to add power, and reduce flaps, then as speed builds take the flaps the rest of the way up.

There are NTSB accident reports about full scale planes failing to pull up flaps when doing an aborted landing.... usually its ugly.
Feb 23, 2007, 10:55 PM
Done it all
I think that one of the best ways to understand the use of flaps is to just do a google search, "what are flaps used for?" Once you understand the use for flaps you will be able to translate it to RC. However, RC scale planes fly different with flaps deployed because RC planes are much more touchy on the controls and they tend to have non-scale reactions.

The main concerns when using flaps on full sized airplanes or RC are the following.

1. Flaps are not to be deployed at high speed, they can be damaged.
2. When deploying flaps at slow speed, the other controls may not have much effect so you better be landing straight.
3. Some planes pitch up when flaps are deployed, some don't.
4. Flaps are used to enable the plane to land on shorter runways. More lift is created, but, also much more drag is also created, power must be used to control the decent.
5. Most planes cannot take off with full flaps, too much drag. If you have to go around, it will be scary and must be orchestrated perfectly.
6. With RC airplanes, if the flaps come down uneven, they will act like ailerons and the plane may roll.

My opinion, flaps on RC airplanes are mostly for appearance.

You put down the flaps at 100 feet to see what they will do and the plane stalls or gets into a spin, how good are you at spin recovery at any altitude?

The plane does not glide well with flaps down, you have to fly the plane onto the runway. Practice wheel landings first, with the flaps up, it's not that easy.


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