From full flaps to no flaps in 0.5 sec.

[JerzyGeorge]

Hi All ,

 

Not long ago I had my flaps disengaged from full position to nothing during take off.

 

Not nice experience , but I recovered with no damage at all .

 

After thorough examination this is what I discovered:

 

1. The top bolt which is the lock-in bolt did not go into position - even with spring action .

 

2. I thought that flaps were locked , but as soon as I got enough air flow over the wing they slammed shut,

 

3. The problem is and please check your flaps assembly for:

 

a) the bottom bolt should work as a stop bolt in full flaps position

 

b) the top bolt should have a 1 mm clearance from the notch to allow for free movement

 

In my case it was opposite the top bolt was working as a stop bolt and not allowing to move up because of the friction. It is something hard to detect without actually looking down there or running your fingers there ( risking nasty pinch) because on the top of the flap lever it looks OK.

 

I do not use full flaps very often and did not notice this problem before ( having about 500 hrs.)

 

I used needle file to open 1 mm gap for the top bolt to allow it to slide free with the bottom bolt taking full pressure. Operated on the ground about 15 times and could not fault it.

 

I am sorry about the poor quality of the photo

 

George

 

 

 

[Old Koreelah]

George what sort of aeroplane?

 

 

[JerzyGeorge]

Of course my trusty Savannah VG

 

 

[JerzyGeorge]

Of course my trusty Savannah VG

[Ultralights]

will have a look at mine tomorrow, though im not a fan of using full flap for take off though.

 

 

[Jabiru Phil]

Same thing happened to me with instructor when training in an old Jab.

 

I made sure it never happened again by wiggling the flap handle to make sure it was in the slot.

 

My memory was that it went off with a fair bang.

 

Phil

 

 

[JerzyGeorge]

will have a look at mine tomorrow, though im not a fan of using full flap for take off though.

It was very short take off ground run because of the limited space available, otherwise I do not use full flaps on take off.

 

 

[erd72]

To prevent that I always pull the button after manipultate the flap handle to check if it is locked in position.

 

Savannah's flaps handle is probably the main savannah's weakness...

 

 

[cooperplace]

Same thing happened to me with instructor when training in an old Jab.I made sure it never happened again by wiggling the flap handle to make sure it was in the slot.

My memory was that it went off with a fair bang.

 

Phil

I always wiggle the flap handle to check it's seated in properly. I've never taken off with full flaps. I've done zero flaps t/o in the jab, and it's fine.

 

 

[SDQDI]

I don't often use full flaps for takeoff BUT when I do it is mainly for the familiarisation of the feeling of high drag and lowered climb performance (I have electric flaps so bumping and dumping flaps to 'bounce her off' isn't an option for me) and I think everyone should practice it (unless of course the Poh says not to!) as it gives you a better appreciation of how that extra drag affects the plane which could come in handy if you are doing a precautionary landing in a short strip and need to do a late go around.

 

 

[rankamateur]

Of course my trusty Savannah VG

There are two little tabs on the inner aluminium part of the flap handle. Reg was here the other day and suggested mine needed more filed off the tabs because it binds a little bit and doesn't lock in the full position unless I wiggle it. Might help yours too.

 

 

[erd72]

I don't often use full flaps for takeoff BUT when I do it is mainly for the familiarisation of the feeling of high drag and lowered climb performance (I have electric flaps so bumping and dumping flaps to 'bounce her off' isn't an option for me) and I think everyone should practice it (unless of course the Poh says not to!) as it gives you a better appreciation of how that extra drag affects the plane which could come in handy if you are doing a precautionary landing in a short strip and need to do a late go around.

I don't need often full flaps to take off with the savannah, but I also think it is important to make some test, in the following video i made ( beginning and particularly at 2.12 mn), you can see that with the motor torque the sav loose the take off axle at low speed due to the engine torque effect i think (probably depend also of the propeller pitch). I means that at very LOW speed, the stabiliser drift do not receive enought wind, so you cannot compensate the drift.

 

With the full flaps, there are much drag, i think the best way to have a short take off is, 0 flaps, short rolling, then progressively full flaps without locking, then progressively first flap.

 

 

 

[Bruce Tuncks]

Having both flaps lift unexpectedly is bad news, but not nearly as bad as just ONE flap letting go.

 

This killed a guy I knew with a glider year ago.

 

Your only chance would be to let the other one go up instantly.

 

 

[facthunter]

Assymetric flap is a problem not particularly addressed by any design rules we operate under. Being aware it may happen is a good start point. The natural reaction is to oppose the roll with appropriate aileron input, which may not be enough so making the flaps the same both sides is the cure. You may also be too slow for the new configuration, so bear that in mind. Also the flap mechanism may be jammed/damaged. Nev

 

 

[bobcharl]

Hi Jerzy,

 

I remember during construction of my VG-XL that it appeared that the slots to accept the locking bolt were not deep enough to be secure. Your photo seems similar. I recall around that time someone else had trouble with inadvertent disengagement of the flap mechanism, so I decided to file the slots deeper to ensure a more positive engagement. Cannot remember if I widened the slot , but I do remember stretching the spring slightly to hold the bolt a little firmer into the slot. So far so good but it is relatively early days yet- only 80 hrs. to date. Could possibly organize a photo if you feel you need it.

 

Regards,

 

Bob

 

 

[winsor68]

I always did the same in the Sav after having them suddenly retract due to not being locked securely. Its a mistake you only make once...due to the BOOM@!!!

 

 

[winsor68]

I don't need often full flaps to take off with the savannah, but I also think it is important to make some test, in the following video i made ( beginning and particularly at 2.12 mn), you can see that with the motor torque the sav loose the take off axle at low speed due to the engine torque effect i think (probably depend also of the propeller pitch). I means that at very LOW speed, the stabiliser drift do not receive enought wind, so you cannot compensate the drift.With the full flaps, there are much drag, i think the best way to have a short take off is, 0 flaps, short rolling, then progressively full flaps without locking, then progressively first flap.

 

I like your videos Eric. Please share more.

 

 

[facthunter]

Can't imagine flaps going full up when loaded would help things. Taking off with full flap is not recommended with anything else I can think of. You get it into the air and it staggers away. A bit sensitive to wind gusts, (as all minspeed climb outs are) and an engine failure would change your situation quickly. Nev

 

 

[dsam]

Taking off with full flap is not recommended with anything else I can think of.

Nev, I frequently take off from rough grass strips with full flaperon in my Eurofox. The flaperons are full length, and hang just below the underside of the wing. The full flap setting isn't a severe angle, so it results in more lift than drag, compared to conventional flaps.

Using full flaps gets me off the rough stuff earlier and slower, and still leaves me with a very acceptable drag penalty. The climb out-out remains quite good, and not a drastic change as I raise them, either. Just thought you'd like to hear of an example.

 

 

[facthunter]

Your design is not conventional. Normal full flap is a large % drag increase. Fine on approach but not sensible on go around or climb out. Draggy planes need quick reaction with engine failure. Your power has to overcome the drag before you can climb and maintain a safe airspeed. Engine out performance is poor and if your speed is such as to have a significant margin above stall you are in strife. You won't climb because of the drag penalty. Nev

 

 

[dsam]

I agree, Nev. I wouldn't recommend take offs with full conventional flaps, either. I was just pointing out that some aircraft designs do exist where this is possible and sometimes desirable.

 

I'm also thankful that my flap lever stays where I put it too!

 

 

[facthunter]

Jets use flap for take off (always less than landing settings) but at higher altitudes it is a small amount. This is to maintain an acceptable climb rate on initial climb.. You have a much higher lift off speed and distance needed too. The principle is the same for all. Soft surface needs you to be clear of the ground as soon as possible but you may have to fly in ground effect and milk the flaps up before climbing.Nev

 

 

[JerzyGeorge]

Hi Guys,

 

Thank you All for interesting discussion,

 

Just to clarify my reason of full flaps:

 

I do it only when want get of the ground quickly ( soft , long grass, wet boggy). I figured out that it starts flying at lower air speed over the wings. With my 100 HP up front there is apple power to overcome rolling resistance quickly, unless I have a flat tyre just before take off. As soon as I am off the ground and have enough speed I close flaps and climb away. This allows me to get airborne with short ground roll and good climbing performance.

 

George

 

 

[Geoff13]

So a question, what limits maximum safe flap speed?

 

 

[Kyle Communications]

why dont you just pump the flap after you get rolling at some speed that will pop you off the ground then slowly release the flap as you accellerate away. Just keep your thumb on the button and pump it out of the indents