flap retraction past neutral

[Quint Van Deman]

Hello ICS from a new member!
I recently finished the purchase process on a 1961 Comanche 180.
Unfortunately, despite a thorough pre purchase inspection, I encountered an issue on my first flight.
We were getting the feel of the airplane by going through the standard stall sequence.
During the cleanup after a power off dirty stall the flap on the pilot's side actually retracted past neutral by a couple degrees.
This lead to a roll force that was uncomfortable yet manageable.
We returned to the field and did an uneventful no flap landing.

Once we were back at the maintenance hanger we confirmed that the flap had actually gone past neutral. The mech pushed on it an heard a series of clicks before it locked back into place.
After that the flaps could be operated normally & retracted to their proper position. The airplane is being taken apart today, but has anyone else experienced this before or have any advice on possible causes/corrections?

Thanks,

Quint

[N3322G]

Hi Quint,

Welcome to Comanche ownership. Glad to hear you were able to land safely.

wrt your flaps. This is the first I've heard of Comanche flaps retracting beyond neutral in 40 years of flying a twin and 6 years of reading two different Comanche internet forums. Did this problem also happen on the pre-buy inspection flight?

I have to preface this with the fact that I am not a mechanic. If I were in your shoes, I'd call one of the Comanche Tech Directors shown in the Flyer Magazine - or one of them may post here. If I were to speculate on the problem, my guess is the plane is not rigged correctly. The service manual is on this website at http://www.comancheflyer.com/NS/index_serv_manuals.php and describes how to correctly rig the flaps.

I'll be interested in the actual problem and solution, please post what happens.

I'd also suggest taking the CPPP Comanche Pilot Proficiency Program, you'll learn a lot no matter what your starting level of Comanche knowledge is.

Hope this helps.

[John Wedge]

Hi Quint,
Congratulations on you getting the 180. I have had a partnership on a 1962 180 for 27 yrs next month and have never had a problem as you had with flap. I have never heard of anyone else having this happen to them either so as Pat said, we would all be very interested in your investigation of this incident and your findings. I am prejudiced of course but I think you bought one of the best and hope you will be as happy as I am with your 180. I will also endorse Pat's recommendation on taking the CPPP course at your first chance, it will really help you to get to know your Comanche in all areas, maintenance, performance and how to best fly it. I would also say that if you can OVERLOOK some of the back biting that has been on this forum in past, you will find a WEALTH of information by going back and reading the old posts. I had been away from flying for several years during the time ICS started this forum and when I got back into ICS I spent hours reading and it really brought me back up to speed on maintenance problems, where to find parts, how to best operate the plane and where to find KNOWLEDGEABLE Comanche advice. There IS a big difference between an A&P / shop that just works on several Comanches a year and an A&P / shop that has become a part of the Comanche following and strive to perform proper maintenance on the Comanche and usually they have a Comanche themselves. I know this from painful financial experience. Am looking forward to your posting of investigation results.
John

[Zach Grant L1011jock]

Quint,
The only way this can happen is if there is something broken/bent/missing in the flap system. As you said it was manually pushed down into position and then all subsequant operations with no load were normal, I would say you probably have a broken flap up stop or bent metal that the stop acts on. The flaps are driven down by cable through the flap handle, but they are returned by spring tension, so physically you should not be able to over stress the flap return to up, but if you just pushed the button and allowed the flaps to snap up from the full down position while under air load, you could possibly do damage to the system. Always be smooth and hold pressure against the flap handle to prevent the flaps from returning to the up position hard. Even when recovering from a full stall in the landing configuration, there is nothing that needs to be rushed. Add power, break the stall (doesn't take much, but a slight reduction in AOA), and then the plane will fly all day long in that configuration. Plenty of power, so never get in a hurry.

Oh yeah, and welcome to Comanche ownership. 180's are awsome in their efficiency and capability on not much HP, but they are misunderstood, and more than a few people who fly C150's all day long have told me how dangerous they are because they are so underpowered...right....

Zach

[Quint Van Deman]

Thanks guys, I will certainly be sure to post the outcome.
I, more than anyone, am obviously very invested in what caused it to occur.
There wasn't anything unusual about the way we did the flap retraction after the stall, but perhaps the springs & such hadn't been retracted under anything more than taxi speeds in a couple of years. The CFI I was flying with is actually a multi comanche owner (1 250, 1 twin) so I feel pretty confident in his knowledge of the airplane.
Regardless I'll definitely check out the pilot's course.

-Quint

[Quint Van Deman]

Hello all--

I heard back from the A&P today. In his estimation there were two problems:
1. The cable was too loose.
2. The return spring was worn out.

It's a little concerning to me that there isn't a physical stop that prevents the flap from going past neutral, but hopefully the adjustments will take care of the problem.

Thanks,

-Quint

[Zach Grant L1011jock]

There is a stop. It obviously didn't work! There in fact is an integral stop/lock on both flaps on the manual flap airplanes. It is at the flap bellcrank. This lock is not adjustable, only the flap actuator rods are. Also do not tighten the actuator cable. It is meant to be loose when flaps are up. First part of the pull releases the lock, and then the cable actually determines the extension for each flap, so if there is an issue with rolling with flap extension, tighten the turnbuckle on the side it rolls toward, or losten the other one... Springs bring the flap UP to the stop. Ir sounds as if your stop on one side was stuck open and the flap excedded the normal up position (don't know how that would work, but I suppose it is possible, or your bell crank is loose and didn't engage the stop at all...) Page 1G5-6-7-8 in the PA-24 service manual has the description and diagrams, and it is part 56 and 56a on figure 36, page 2K10 in the PA-24 parts manual.
-Zach

[Quint Van Deman]

Hello all, as a follow up, I got her back in the air yesterday and all is well with the flaps.
The mechanic, who I really trust & is a former Comanche owner, said that there were 3 problems in the end:
1. The return spring was worn (replaced)
2. The stop "plunger" (as he described it) needed lubrication
3. The rigging was "loose and terrible" (redone & adjusted)

I gave it a thorough ground test and the flaps performed perfectly on the 10 or so landings we performed.

Thanks to all for the helpful advice.

-Quint

[N3322G]

Quint,


Glad you are flying again and all is well.

Excellent post. Thanks for the follow-up - it is appreciated as we all can learn from one another.