How bad could this have been?

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texasmatt

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texasmatt
First time posting here but figured this would be the place to ask. I'm currently getting my private in Cherokee 140. I've finished my solo and duel cross country (just to give you an idea of where I am).
Last week I flew with my instructor to a nearby airport. This particular day we had a direct left crosswind at 7-8 knots which was good for me because I needed to practice my crosswind landings. I was about halfway thru my final approach at 400 ft AGL and 80 knots with full flaps and side slipping the airplane to compensate for the crosswind. Suddenly the plane banked left for no apparent reason and it all got sloppy at end. I was able to get realigned with the runway and set it down but I couldn't understand why a well executed approach had turned so bad. My instructor reassured my that it was just the wind whipping close to ground and that I had handled the situation well.
Determined to get better I took off and tried the same landing again and it felt better (not great). That was enough that day so we headed back to our airport where I made another so-so landing and put the plane away.
Yesterday I went to fly the airplane (first time since that day). I did a thorough pre-flight inspection like I should and I found something that was very scary. On my left flap the pin (its actually a bolt) that the control rod connects to had backed out and was flopping all over the place. This was allowing the trailing edge of the flap to move 2-3 inches in either direction. Took the plane straight to the shop. With the flaps all the way down the bolt just fell out letting the flap go completely free.
So I'm figuring that last week on that bad landing was when it came loose and that let the flap retract a few degrees which caused the plane to bank a little on final. What scares me is (1) I landed the plane 2 more times after that with the flaps down, and (2) this is the big one, what if that pin had come out while on one of those final approaches. I feel like the plane would have banked hard left and at that altitude would I have had time to figure out what had happened before wrecking the plane. Would full right aileron and some use of right rudder have been enough to compensate for the role until I could regain airspeed and raise the one flap that I had left. Any thoughts on this would be appreciated.
As it is right now I'm considering myself lucky and quite certain that no matter how long I fly or how new my plane is, I will always perform detailed pre flights before any flight, not just at the start of that flying day.

Thank.
 
Asymetrical flap application on short final probably would not have been survivable. No one knows without trying but I doubt opposite aileron and rudder would have near enough authority to overcome the roll.
Good catch!
Tim
 
Learn what should have been there. Either a nylock or castle nut and cotter pin. finding missing cotter pins and such is part of a good preflight. at least several times during training, I found stuff that others had missed many times over with the rental fleet.
 
You learned a valuable lesson,on the benefits of a thorough pre flight. Glad it all worked out for you.
 
N175PT - Thank you, "Asymetrical flap application" was the wording that I wasn't using when I was looking for information on this condition. After I used that I found a lot of info on it. You confirmed what I thought. It would have been an unlikely recovery.

yetti - I fully understand what you mean and as an engineer myself I understand what I should be looking when I check my control surfaces. This plane "no kidding" was built without any lock nut/pin/lockwire of any kind on this connection only. It is just a bolt into a nut plate. I know this sounds crazy but next time you see a pre 65' Cherokee take a look at the flaps. Their made in such a way that you can't even see the nut that the bolt is going into. Later models of this plane were re designed to use a nut and cotter pin and allow viewing of them from above. We are looking at changing to the newer design as it will be much safer.
 
I was taught never to extend flaps while in a turn (to base or final), to avoid this rare occurrence. What was the time between your final flap adjustment and the sudden bank?
 
texasmatt said:
So I'm figuring that last week on that bad landing was when it came loose and that let the flap retract a few degrees which caused the plane to bank a little on final.
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I know you're trying to analyze the situation, but the odds are this didn't happen. A loose nut does not impact the sheer holding ability of the bolt, it impacts the ability of the bolt to stay in. The airplane certification rules require that the bolt be placed in a way that the stress is not on the nut, it's entirely on the bolt. Losing the nut should not have allowed the flaps to come out a few degrees.

It was probably the wind whipping you around.

BTW, you've probably heard this all the time, but when you get sloppy on final, a go around is always a good option. Good that you could get back to land on the runway, but bad that you might have been pushing to do it. Don't guess, if it isn't right, give it up. Your CFI is looking for you to show good judgement and one good way is to get into situations like this and then say "hey, it's not great, I'll go around and do it better next time".
 
For peace of mind I would start getting in the habit of executing a go around at anytime you feel uneasy about your landing. Call me a sissy but it's not at all infrequent for me to do that when something is out of the norm. For example few weeks ago flying back from a 300 nm XC there was a hefty 10+ knot crosswind at my homefield. As I set one wheel down my wife said 'Yah', not knowing what she said or if she was pointing out another plane, or a flat tire or what I immediately went all in and took back off. Then I reminded her on downwind that we don't talk unless there's a problem. Salvaging landings is something I don't want to gamble with.
 
N175PT said:
Asymetrical flap application on short final probably would not have been survivable. No one knows without trying but I doubt opposite aileron and rudder would have near enough authority to overcome the roll.
Good catch!
Tim
Click to expand...

I wonder about this. Cherokee flaps aren't exactly barn doors like on a Cessna. Anyone ever had asymmetric deployment on the Cherokees?
 
It "seems" like what you experienced was possibly some wind shear, wake or wave turbulence on final. Any terrain or river valleys?

Where I trained the mountains made for some rolling air on windy days. Sometimes the airplane would bank hard and full opposite aileron and full power made little difference until exiting the situation.

I've experienced the exact type of wing drop you describe in wind sheer on final going from a cross/headwind to a tailwind aloft. Just remember the winds can be very different in the air above the runway compared to what an AWOS/ATIS is reporting on the runway.

Great catch on the pre-flight. It amazes me how so many people out there really don't give them the attention they should. Heck, I even had times during my training my CFI would ask me to hurry it up. Not gonna happen.. I'm not flying this thing unless I know everything I could see was as it should be.
 
Sounds like the wind more than a loose nut. I usually input flaps high enough that if it goes south I can put in the power and get some altitude. Still, something that bad should be spotted in a thorough preflight.
 
Ok so I can't put a hyperlink or a web address in a post without approval. I'll try this. Go to youtube and search G7DiVf3rk5I or Flap Push Rod. It's an 11 second video that shows the failure. I guess it could have been wind and I can't disagree because I only have 15 hours of flying but this seems like it could have had an effect. Thank you all for the feedback.
 
texasmatt said:
Ok so I can't put a hyperlink or a web address in a post without approval. I'll try this. Go to youtube and search G7DiVf3rk5I or Flap Push Rod. It's an 11 second video that shows the failure. I guess it could have been wind and I can't disagree because I only have 15 hours of flying but this seems like it could have had an effect. Thank you all for the feedback.
Click to expand...

here ya go..

 
From what I understand the manual flap setup used in the piper planes makes an asymetrical flap almost impossible. Since the linkage is basically controlled by one rod that then feed the rods that adjust the flap. That type of failure is much more likely (although still very rare) in electric flaps where two separate motors are controlling extension. I have been training in a Warrior which is essentially the same plane. What you experienced is very similar to the wind shear situation I had about 2 weeks ago. I was trying to practice short field landings, and the IAS was jumping up and down about 10 knots at times, along with the plane suddenly starting to settle faster and sooner than expected. Not fun when you are going over trees. It is also common with strong gusts that the plane will weathervane aggressively into the wind. My biggest experience on this was not on landing, but take-off. After the mains left the ground the plane instantly rotated about 30 degrees into the wind.
 
drotto said:
From what I understand the manual flap setup used in the piper planes makes an asymetrical flap almost impossible. Since the linkage is basically controlled by one rod that then feed the rods that adjust the flap. That type of failure is much more likely (although still very rare) in electric flaps where two separate motors are controlling extension. I have been training in a Warrior which is essentially the same plane. What you experienced is very similar to the wind shear situation I had about 2 weeks ago. I was trying to practice short field landings, and the IAS was jumping up and down about 10 knots at times, along with the plane suddenly starting to settle faster and sooner than expected. Not fun when you are going over trees. It is also common with strong gusts that the plane will weathervane aggressively into the wind. My biggest experience on this was not on landing, but take-off. After the mains left the ground the plane instantly rotated about 30 degrees into the wind.
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Not correct.

Most electric flaps (I've experience with 172s, 177s, 182s, and 206s) have one flap motor. On Cessnas, it's inside the right wing near the root, in the back. An electrical fault alone will not cause asymmetric deployment.

The observed fault was downstream of the common rod, and would have affected any flap application, electric or otherwise.

Most likely, were it to fail, it would be during deployment. So, the recovery is to suck them back up immediately, apply full power and go around. But the incident at hand really does sound like ground level wind shear and not a flap fault. It's very very VERY common. Sometimes even in no wind where the ground is unevenly heated by differences in coloration or temperature. A sudden rolling moment on short final is also consistent with a wake turbulence encounter.
 
Good reminder why it's good to not just look at but touch every one of those little linkages on every pre-flight.
 
cowman said:
Good reminder why it's good to not just look at but touch every one of those little linkages on every pre-flight.
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You bet. Even when the manufacturer's checklists (Cessna) don't include lowering the flaps.

If you're going to be using it during flight, you want to know it works. Flaps can only be tested by deployment and tactile inspection of linkage ends and tracks. For electric flaps, extension also tells you the state of your electrical system.
 
yetti said:
Learn what should have been there. Either a nylock or castle nut and cotter pin. finding missing cotter pins and such is part of a good preflight. at least several times during training, I found stuff that others had missed many times over with the rental fleet.
Click to expand...


Yup


To the OP, what happened to you seems more like landing in gusty conditions, be sure to adjust your approach speed for half the gust factor, ie you approach at say 50kts, winds are 5 gusting 15, this gives us a 10kt gust, half of 10 is 5, so your new approach speed should be 55kts.

As for how bad a asymmetrical flap condition could be, well it's a non event if you keep your hand on the flap switch or lever until your flaps are down, plane starts to roll take the flaps OUT, this is one reason I prefer manual flaps.
 
Yup, this is why I push and pull every control rod I can get my fingers on.

Was the bolt bent? Has the hole worn out? I've never seen that kind of wear before and I flew Pipers that had 14,000 hours on them. Granted, they were inspected and flow multiple times almost every semi-decent day and inspected every 50 hours.

But that's pretty grossly out of spec.

Still, this wouldn't really make the airplane skew the way you originally described. It was wind.
 
You guys are great. What I've learned (1) Thorough pre flights ALWAYS even if it's hangered and I'm the only person that flies it. Look at, touch, and move by hand everything that will be moving in flight. Got it. (2) This may not have been what caused the rough approach but I do know that it would have caused an asymmetrical flap deployment at some point since I watched the bolt fall out shortly after taking the video. Hopefully that failure would have happened during clean flight or as the first notch of flaps were being deployed. I think MAKG1 was probably right on with that, the chances of that pin working it's way out with the pressure of full deployment pushing on them is far less likely and that makes me feel much better about the situation. The only other thing I would be interested in is if anybody has ever experienced an asymmetrical flap emergency of any kind on something like the PA-28 and what was the recovery like. Thanks again.
 
bflynn said:
Was the bolt bent? Has the hole worn out? I've never seen that kind of wear before and I flew Pipers that had 14,000 hours on them. Granted, they were inspected and flow multiple times almost every semi-decent day and inspected every 50 hours.
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No the bolt was not bend or worn down, it just simply backed out of the "nut-plate" that it was threaded into. The flap had zero play in it until this happened. So I don't think it was a wear issue unless you want to count the nut wearing out which is apparently what happened but who would have known since you can't see it. On the version of the Piper flaps that replaced these the sheet metal is cut much further out to the left if your looking at that picture/video. That exposes the lock nut and and cotter pin for inspection. Several other planes on our field are just like this one.
 
I agree with the other posters in saying this was most likely the wind rocking you around down final, especially with the X-wind conditions you described. Also a good job with the pre-flight in finding that loose nut. Chances are it wasn't the nut that made the wing drop but likely the wind.
 
texasmatt said:
No the bolt was not bend or worn down, it just simply backed out of the "nut-plate" that it was threaded into.
Click to expand...

I have a very similar story with my Mustang (the Ford kind, not the P-51 kind, sorry). The bolt holding the left lower control arm of the rear axle backed out, just like yours. I too got lucky by noticing play (in tracking on the road) and after climbing under the rear, I found the bolt and felt the pure luck of the last 4 threads sticking in the hole. :eek:

I agree with the sentiment here, a good preflight is essential. A good postflight helps too.
 
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