Flaps

[Captain Pappy]

Well this arrow T 28 has been my first plane with flaps. I have been using a 10% flap on the first setting and 20% on the second. The plane still seems to land fast. Not sure if it would be safe to adjust for more flaps. What percentages do you pilots use on your flaps.

[Evan D]

The instructions give you a specific distance in mm. Use that.

[Captain Pappy]

The instructions give you a specific distance in mm. Use that.

Nothing on the instructions on the flaps

[boomer108]

Try 15% and 30%

[Evan D]

You’re right! Odd... let me look at other 1.1 or 1.2M T-28 instructions. I assume about 15 and 30 would be about right...

the 1.2 has 20 and 50mm so maybe 18 and 40... I don’t see another 1.1 with flaps.

[Captain Pappy]

You’re right! Odd... let me look at other 1.1 or 1.2M T-28 instructions. I assume about 15 and 30 would be about right...

the 1.2 has 20 and 50mm so maybe 18 and 40... I don’t see another 1.1 with flaps.

[Captain Pappy]

Well I adjusted the flaps to 40mm it bottom out. So I set the flaps to 35mm which was about 30% like boomer mention. I have about 27 % mix on the elevator. Going to fly tomorrow and I will see how it flies. Thanks for the info I will update tomorrow.

[rifleman_btx]

I always did mine in degrees, so landing was 45° and take off was 20°

[Evan D]

That could be a good starting point though some planes can use quite a bit more deflection.

I always did mine in degrees, so landing was 45° and take off was 20°

[GliderGuy]

If you wish to have a better understanding of flaps <highly recommended>, may I suggest a read:

https://en.wikipedia.org/wiki/Flap_(aeronautics)

There are many other articles also available online.

RC pilots should have more than a minimal understanding of flaps. I will add a caveat. There are exceptions to every "rule", but generally.....

Those who think that "it's time to land...flip the flap switch" and do this regardless of airspeed may eventually regret their lack of understanding FLAPS!

The main functions of flaps the RC pilots should thoroughly understand are:

• increase lift at any given flying speed
  • deployed flaps allow one to stay in the air at a slower airspeed for a given weight <within limits, of course>
  • the effect is a reduced stall speed (example: 35 mph stall without flaps down changing to 30 mph stall with the flaps down)
• increase drag...significantly more after about 15 degrees of deflection...after 15 degrees, the drag increases much more rapidly than lift increases
• with flaps down there is an increase in structural loads on the wing and supporting flap hardware
  • you may rip off your flap(s) if deployed at too high an airspeed
• may cause <typically do cause> a pitch up or pitch down attitude change when deployed
• 40 degrees to even 90 degrees of deflection for landing provides lots of DRAG to bleed off kinetic energy quickly for shorter landing rolls (small fields)
  • a corollary to this is steeper approaches can be made to clear tall obstacles in the approach path without increased airspeed from a low nose attitude
  • large deflections will have the effect of decreasing the airspeed for any given pitch attitude, so the pilot must either add power or lower the nose to maintain a given airspeed

Things RC pilots <and full scale pilots> should understand about WHAT NOT TO DO with regard to flaps:

• because of the structural stress caused by flap deflections beyond 10 to 15 degrees...deployment of flaps at high speed should be avoided...you can rip them off!!!
  • a corollary to this is that different amounts of deflection can have different "red line" speeds <max speed for deployment>
    • in the full scale sailplane I fly, each flap setting has a separate "never exceed" speed
      • In the flight simulator I fly, for the high performance aircraft, the digital RED BAR or barber pole immediately changes upon flap deployment to reflect the max red line speed for that flap setting
    • for the Freewing MiG-29, DO NOT FLY FAST WITH FLAPS DOWN or you risk becoming a lawn dart
      • this may be unique to this RC EDF, but flying fast with flaps down has been demonstrated to cause excess elevator servo loading...sufficient enough to stall the servos. MRC is now providing even stronger hardware/servos for the full flying stabs for this EDF
• for best take-off performance, avoid take offs with full flaps...limit take off settings to about 20 degrees max (more lift for the given drag increase)
• avoid aerobatics with the flaps extended
  • aerobatics add additional stress to the structure...flaps down add more stress...may exceed max flap deployment speed during aerobatic maneuvers
    • might have a structural failure
• changes of deflection from about 45 degrees to 90 degrees typically do not cause additional pitch changes
  • 90 degrees of deflection will, however, require significant power addition or lower nose attitude to maintain flying speed
    • full scale sailplanes which use 90 degrees of flap deflection <vs spoilers or dive brakes> for approach descend at impressive nose down and descent angles which take a bit of getting use to by the pilots
• avoid dumping of flaps on approach...the immediate decrease of lift will cause the plane to drop and may impact the ground
• using flaps in cross winds complicates the approach
  • slower speeds equate to the need for an increased wind correction angle to counter the cross wind (work it out on your handy E6B or computer program)
    • a bounce <now at even a slower airspeed after the bounce> will require an even greater wind correction angle (and your control effectiveness is now decreased even more due to the slower airspeed)
      • things go to heck in a hurry, if you get my point
        • you may not be able to keep the plane on the runway
          • most authors suggest not using flaps in cross wind landings, or only minimal deflection at best

The most important take-away from the above is....

S L O W D O W N before you deploy the flaps to reduce the stresses imposed on the structure and to help minimize pitch changes.

Setting a flap/elevator mix, of course, helps counteract the pitch changes caused by the flaps (note: some aircraft do not require flap/elevator mix), but the amount of mix may not work for faster airspeeds.

Pilots who have a better understanding of why and how things work are better pilots.

-GG

Aside: In the "Exception to every rule" category, you can watch tons of YouTube videos where Navy pilots are shot off carriers with FULL FLAPS...approaching 90 degrees of deflection. I reckon the additional reduction in stall speed (from 45 degrees to 90 degrees) is worth the added significant drag increase. But with a catapult shooting you off...what's a few more pounds of added drag among friends?

[kallend]

Pilots who have a better understanding of why and how things work are better pilots.

-GG

What he said!

[Captain Pappy]

What he said!

Well headed out this morning and got one flight in, the adjustment on the flaps seem to be ok, but still lands a little fast. Next flight out I am going to exetnd them all the way down. Which is about 40%.

Well on a bad note I had a crash during take off, to much ruder to the right, nosed it right in to the ground. I got lucky, only a broken prop and a crack in the wing. The plane is a Arrow T 28. I use to use hot glue to repair some planes with but that was a long time ago. Any suggestion on what would be a good glue to use that wont damage the foam.

[SanExup]

Based on what your damage sounds like...

Foam tac works well, it's fairly easy to clean up, post drying, if you have a little squeeze out. If you use too much and have a lot of squeeze out then you have to decide to wipe it then or let it dry. Foam tac is a more flexible glue.

Then there's foam safe CA which isn't as flexible. It's sold in different viscosity. And you can use accelerator spray, which makes for quick gluing. I bring it to the field with me for quick repairs but I try not to do field gluing anymore. CA plus accelerator glue joints can turn out ugly if you're not diligent about using just enough. It creates boogers.

A number of people did use hot glue. I'm not versed in it so I can't speak to it. For me, I need to use brushes or toothpicks or other items to apply glue and not have it be an ugly mess. I assume with hot glue that it has to come straight from the gun? So thus I haven't even tried it. Though, as I said, a number of people do use it.

[SanExup]

Also, I don't know what radio system you have but programming some exponential to your rudder/nose wheel can help with those twitchy on the ground steering corrections. I know some people have a light touch with the rudder, but I need expo.

[GliderGuy]

Well headed out this morning and got one flight in, the adjustment on the flaps seem to be ok, but still lands a little fast. Next flight out I am going to exetnd them all the way down. Which is about 40%.

Well on a bad note I had a crash during take off, to much ruder to the right, nosed it right in to the ground. I got lucky, only a broken prop and a crack in the wing. The plane is a Arrow T 28. I use to use hot glue to repair some planes with but that was a long time ago. Any suggestion on what would be a good glue to use that wont damage the foam.

Sorry about your oops. Also, you may want to back up to post #10 if you haven't already

#10
Today, 07:36 AM

Multiple glues...CA, hot glue, 5-min epoxy, etc. work fine on EOP foam.

For a small crack in the wing...and the fastest repair, 2-part / 5-min epoxy...clean up excess with isopropyl alcohol while uncured works well. However, I use hot glue with a fine tip. With practice, you can apply without too much foam damage, but for small cracks hot glue may not be the best choice due to the melting of the foam. Foam Tac would also be a good option, but you will need to wait for it to cure.

Some planes respond rather positively to rudder application with an accompanying wing roll. Sounds like the T28 is one of these. It's probably best to use rudder for minor directional corrections on take-off and stick mainly with aileron and elevator controls, otherwise. The AL37 is one such bird. Gotta be easy on the rudder on take-off with it, too. She'll roll fast with rudder and get a wing down before you know it.

Adding expo on the rudder/nosewheel may help...maybe 30%.

If you are concerned about the structural strength, you can cut a thin slit 90 degrees across the break about an inch long (on the bottom side of the wing) and insert and glue in some stiff material...like thin plywood, carbon fiber, even a balsa stringer.

-GG

[Captain Pappy]

Also, I don't know what radio system you have but programming some exponential to your rudder/nose wheel can help with those twitchy on the ground steering corrections. I know some people have a light touch with the rudder, but I need expo.

I adjusted the ruder the other day and made it less but that just was not the case. It was all me, so many successful flights and an occasional crash. Definitely humbles you. The wing does not appear to be broken but there is a crease and it is flexible. I am sure there is crack in it but it just does not appear on the finish part of the foam.

[Captain Pappy]

I adjusted the ruder the other day and made it less but that just was not the case. It was all me, so many successful flights and an occasional crash. Definitely humbles you. The wing does not appear to be broken but there is a crease and it is flexible. I am sure there is crack in it but it just does not appear on the finish part of the foam.

Good info on the flaps, I have watched u tube, and done a lot of reading on the flaps. This is my first plane with flaps, I just want to make sure I am setting the flaps in the correct position.

[SanExup]

On your cracked wing flex, do you think you broke the spar?

I broke a carbon spar last year from a very mild crash with another plane. I was actually surprised at how easily it broke. I don't know if that's the case for you or not, but I've seen wings fold under stress from a previously broken spar.

[Captain Pappy]

On your cracked wing flex, do you think you broke the spar?

I broke a carbon spar last year from a very mild crash with another plane. I was actually surprised at how easily it broke. I don't know if that's the case for you or not, but I've seen wings fold under stress from a previously broken spar.

I can't really tell if the spar is broken. The wing seems to have a crease in it. I was just assuming it was cracked on the inside. Not sure, it just seems a little weak. I am going to use some glue on it to strengthen it and see how that works out first.

[GliderGuy]

I can't really tell if the spar is broken. The wing seems to have a crease in it. I was just assuming it was cracked on the inside. Not sure, it just seems a little weak. I am going to use some glue on it to strengthen it and see how that works out first.

From lessons learned….adding a bit of reinforcement other than glue (work on the bottom side that you don’t see) is far better than “see how it works out=failed wing”.

-GG