SonexBuilders.net

Good day everyone.
Thought I’d ask this to see if anyone else has experienced this at all. The other day I was doing some stalls clean and dirty configuration to check out the handling and what to expect.
All good until I completed a full flap stall. On recovery, I could Not for the life of me retract from full flaps. It felt as if the flap handle was intended in concrete.
Only upon landing was I able to retract the flaps. During the dirty full flap stall I started to extend flaps 10 degrees at 80 mph, 20 degrees at 70 mph and full flap going through 50-55 mph so I know the flap speed was not exceeded.

Never have any trouble retracting flaps from 20 degrees or 10 degrees but something that is concerning is trying to retract them from 30 degree configuration, especially when on an overshoot condition.
Any info would be wonderful on this if you had the same issue. I don’t believe that the load on the flaps would be that much that it would prevent retraction from 30 degrees.

Thanks in advance
Mark

You should test these on the ground while simulating an air load on the flaps. While in full down flap config, have someone exert an upward pull on the flaps as if moving airflow is trying to raise them. Not enough pressure to dent the flap, obviously, but enough to keep a constant load on the flaps.

Now try to move out of full flaps using the flap handle. Pictures of your full system would aid all of us to help diagnose.

Others have had trouble if they have created a nub on the flap dedent for the purpose of keeping the flap handle from releasing on its own. Sometimes that dedent is too big or shaped in a manner that won't let it release while the flaps are under a load. Without an air load, it works fine, but with the load, it won't release cleanly or easily.

Of course, it could be anything else, but this is a good place to start.

pappas wrote:You should test these on the ground while simulating an air load on the flaps. While in full down flap config, have someone exert an upward pull on the flaps as if moving airflow is trying to raise them. Not enough pressure to dent the flap, obviously, but enough to keep a constant load on the flaps.

Now try to move out of full flaps using the flap handle. Pictures of your full system would aid all of us to help diagnose.

Others have had trouble if they have created a nub on the flap dedent for the purpose of keeping the flap handle from releasing on its own. Sometimes that dedent is too big or shaped in a manner that won't let it release while the flaps are under a load. Without an air load, it works fine, but with the load, it won't release cleanly or easily.

Of course, it could be anything else, but this is a good place to start.

Thanks for the reply pappas. Definitely a start thanks.

Mark

If it is NOT an actual mechanical issue and when on the ground they are not bound up and jamming in some way......Then are we actually talking about how hard it is to pull them out the Flaps 30 detent and ease them out to Flaps 20???

You do need pretty good biceps to get the last 10 degrees of flaps applied under any slow flight regimen unless you are going slow. And once it is in there - it can be a bear to get the handle back out. That "stuck in concrete" feeling you reported.

Couple of tricks:

- If the handle is just the bare aluminium bar that hurts your hand as you pull it - get a slip on plastic sleeve - or binding it with some tape will make it easier on your hand, it hurts less and let you pull harder.

- though it goes against the teachings of most stall recovery where you pitch down, go full power and then milk the flaps off. On the Sonex - I actually go flaps 30 to 20 FIRST and then pitch down and apply power. With the flaps less loaded it is a lot easier to get the handle out the Flaps 30 detent. For the overshoot/go around - well I will admit my flaps are 20 on final and I only apply 30 when I KNOW I have the runway made and I am pulling them to act as a brake and create an air cushion to soften the decaying airspeed. I usually never actually put them in the Flaps 30 detent on final and if I do need to go around I drop them into the Flaps 20 detent and then apply full power. As soon as I touch down I let the flaps go to zero to kill the lift and stick the plane. Like the bush pilots do up in Alaska....

- Eat more Wheaties or Spinach to get that bicep working better for you...... ;-)

GraemeSmith wrote:If it is NOT an actual mechanical issue and when on the ground they are not bound up and jamming in some way......Then are we actually talking about how hard it is to pull them out the Flaps 30 detent and ease them out to Flaps 20???

You do need pretty good biceps to get the last 10 degrees of flaps applied under any slow flight regimen unless you are going slow. And once it is in there - it can be a bear to get the handle back out. That "stuck in concrete" feeling you reported.

Couple of tricks:

- If the handle is just the bare aluminium bar that hurts your hand as you pull it - get a slip on plastic sleeve - or binding it with some tape will make it easier on your hand, it hurts less and let you pull harder.

- though it goes against the teachings of most stall recovery where you pitch down, go full power and then milk the flaps off. On the Sonex - I actually go flaps 30 to 20 FIRST and then pitch down and apply power. With the flaps less loaded it is a lot easier to get the handle out the Flaps 30 detent. For the overshoot/go around - well I will admit my flaps are 20 on final and I only apply 30 when I KNOW I have the runway made and I am pulling them to act as a brake and create an air cushion to soften the decaying airspeed. I usually never actually put them in the Flaps 30 detent on final and if I do need to go around I drop them into the Flaps 20 detent and then apply full power. As soon as I touch down I let the flaps go to zero to kill the lift and stick the plane. Like the bush pilots do up in Alaska....

- Eat more Wheaties or Spinach to get that bicep working better for you...... ;-)

Lol. Thanks for that. I’ll give that a shot. I read somewhere but can’t remember where about this.

Mark

Had exactly this happen twice; once when it was embarrassing and once when it was dangerous. The embarrassing one was while doing my BFR and I pulled full flap for an engine out landing drill. I had to get the instructor to take control while I used both hands on the flap lever. On the other occasion I wasn't happy with my approach and decided to go around. I ended up doing the whole circuit on full flap and even with 3300 power it didn't want to climb. After that I made a new flap position bar and got rid of that stupid deep notch.

Peter

It is usually a very simple problem with an easy fix. The way the handle is bent in at the top so that it can easily be grabbed results in twisting of the handle, and the harder you pull the more it wants to twist and that binds it into the notches of the angle that holds it in set positions. That happened to me on first flight. Two solutions, One is cut angled recesses into the notches in the position holding angle so the handle can twist without binding, which is what I did, or pre-twist the handle slightly so that it is near straight when being pulled back.

However, having received training in a Sonex that had home brew electric flaps I quickly converted to that. and it has many other advantages. Have drawings showing the modified notches and the electric flap conversion if interested in either PM me with your direct e-mail. The actuator used and various bits only cost about $150, and has been trple free for 10 years and a lot of landings.

David A.

I just had that happen in my OneX. I had just fabricated a new slot plate with a mid flap position for the flaps. Was kind of proud of my improved workmanship for the revised piece. Next flight I was unable to get flap handle out of full flap position. I could duplicate the problem on the ground by putting just slight up pressure on the flap trailing edge. It turned out that with the up pressure from the flap air load would put a slight twist on the handle in the slot. The handle would wedge against the aft slot and the front nub catch. I filed the aft edge of the slot to provide a little more clearance which helped but didn’t remedy the issue. Next I removed the handle and bent some forward twist in it so it wouldn’t wedge in the slot with upward pressure on the flaps. Another option would be to make the slot depth deeper so a slight handle twist can’t wedge. I haven’t tried tightening the tension on the flap handle pivot bolt. That might reduce the handle twist flexing.
Tom

There was some discussion of this problem in the early stages of the Sonex. I think it came down to some rotation of the flap handle in a tight fitting flap slot. Since the handle is bent inward near the top, pulling on it gives it some rotational force. This in effect locks it into the slot.

I simply elongated my slot slightly with a file to provide a looser fit. Works great now.

Mervin Friesen
Sonex 122

Mark.............David A. is correct in that the harder one pulls on the flap lever, the more it twists. This is most problematic at the 30 degree flap position. A solution is to widen the slot at the rear to provide space for the "twist" to occur without binding. No more stuck flaps on a goaround. Been there, done that.

Art,,,,,,,,,,,,,,,,,,Sonex taildragger #95,,,,,,,,,,,,,,,,Jabiru 3300 #261