Manual flaps pulley came off pulley - Snow?

gitmo234

gitmo234

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gitmo234
Hey everyone,

During a de-icing and pre-flight adventure today I cleared off about 6-7 inches of snow from the wings of my plane and then de-iced it. I'm in a 1956 C172

After the de-icing I noticed a gap on the right flap when fully up. I could see daylight. The gap was about 1/2 an inch to an inch. I lowered the flaps, and there was a "rough" feeling, which I assumed was due to the snow and ice melting off of it.

Raised them again and they were even rougher. Gap was still there. With some play.

Lowered again to take a look, and when I tried to raise them, it was hard to get them back to fully 0 degrees.

Airport mechanic happened to be in his hanger and I called him over. He popped a panel or two and said that the cable for that flap had come off the pulley and he'll take care of it early in the AM monday if it was a simple pulley up top, but my flaps go down under the floorboards to the johnson bar. If they were off those pulleys as well we're talking a longer time to fix.


My question is: Could this be related to the weight of the snow? Or, as my dad would politely put it "horse assing around" with the flaps before the ice and snow were cleared 100%? I didnt use much force lowering them the first time, but it was also about 15 degrees out.


Thanks
 
Which way did you spray the deice fluid?

With the natural flow of the wind over the wing? Getting that stuff into the wrong places can cause all sorts of problems.

I doubt the weight of the snow caused the cable to come off the pulley, I could see it causing other stress issues though.

I could also see the flaps being a little iced up and not moving freely, your flaps up and down could have made some slack in the cable with a stiff flap, then the cable could have tightened up and came off the pulley.
 
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I kinda mixed up the flow of the de-ice. It was a small cart, and the pressure on it made it almost not worth doing.

What areas do I need to make sure I dont get it in?
 
Looks like I'm good. My glycol wasnt heated, and it was so low pressure I would have done better with a hand pumped spray bottle, and I didnt spray any of the sensors/tubes, etc

Laughably, I would have more PSI If I would have dumped glycol from a jug onto the wing
 
If you're going to be needing de ice often, those insecticide sprayer backpacks are great, just add hot water from the bathroom or somewhere and a snow brush and you're golden.

I've seen people spray the stuff up their flaps and cause issues. Just be sure to always go with the flow of the air over the wing and you should be good.

The heat is really what takes the frost off, I've never bothered to spray it on cold.
 
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If the cable is off the pulley, it's because a safety pin or strap is missing. They're called cable guards. All pulleys have one or more means of keeping cables from falling off when slack. I'd bet that the whole airplane needs checking for such stuff. Imagine an elevator cable coming off a pulley and jamming between the pulley and bracket; could get really ugly.

18776d1342535858-cable-guards-093.jpg


Dan
 
I agree with that, cables shouldn't just jump the pulleys. Isn't stuff like this supposed to be checked during annual inspections?
Dan Thomas said:
If the cable is off the pulley, it's because a safety pin or strap is missing. They're called cable guards. All pulleys have one or more means of keeping cables from falling off when slack. I'd bet that the whole airplane needs checking for such stuff. Imagine an elevator cable coming off a pulley and jamming between the pulley and bracket; could get really ugly.

18776d1342535858-cable-guards-093.jpg


Dan
Click to expand...
 
peerlesscowboy said:
I agree with that, cables shouldn't just jump the pulleys. Isn't stuff like this supposed to be checked during annual inspections?
Click to expand...

Depends what the owner is willing to pay for inspections, and how ethical the mechanic is. Some owners want an inspection that is little more than a walkaround, and some mechanics are willing to do those. It takes considerable time to open up all the inspection panels on the wings and fuselage, and sometimes it takes a long time because they haven't been off in many years and the screws are rusted in. And it takes a long time to take the seats and carpet out so the floor panels can be removed to get a look at all those cables and pulleys that run through the belly, up the doorposts, and back to the tail. When we get an airplane that we haven't been through before we take a good look and always find a bunch of stuff that should have been fixed a long time ago. Some of it is scary: frayed control cables, seized pulleys, mouse nests with dried-up dead mice, fuel lines chafed almost all the way through by cables or wiring or Adel clamps from which the rubber cushions have rotted away. Cracked structures. Corrosion. 40-year-old hoses that are as hard as wood, sometimes cracking they're so old, sometimes with steel braid bursting out of them from swelling caused by braid rust. Stuff that should have been caught at the last annual, but has obviously been there many years.

Sometimes there are so many expensive problems that it's just not worth saving the airplane. The owner thinks he has been a frugal airplane owner all those years and thinks his machine has appreciated in value. Ha.

Dan
 
What Dan said, and an annual inspection doesn't preclude part failure the very next flight.

My mechanic is a good one and the first thing he mentioned was the probability of needing to go into floor boards depending on the what he finds up top.
 
Issue resolved:

Pulley guards were all fine, but the mechanic diagnosed that with the weight of 6+ inches of snow, combined with my "horse assing" the handle to de-ice it, caused quite a bit of slack in the cable. It was off the pulley but within the pulley guard.

Everything has been reset, checked for proper tension, etc and we are 100% back to functional operation.

It was even test flown today.
 
gitmo234 said:
Issue resolved:

Pulley guards were all fine, but the mechanic diagnosed that with the weight of 6+ inches of snow, combined with my "horse assing" the handle to de-ice it, caused quite a bit of slack in the cable. It was off the pulley but within the pulley guard.

Everything has been reset, checked for proper tension, etc and we are 100% back to functional operation.

It was even test flown today.
Click to expand...

So the pulley guard is misadjusted or bent, or the pulley's flange is worn or nicked. There should not be enough room between the flange and guard for the cable to come off.

Dan
 
Cessna flaps require a cable pull to move them in either direction. I seen a lot more than 6" of snow on lots of Cessna's and haven't seen any pulley problems. The same is true for wind on the tail. On a plane like a Cub that has a cable to employ flaps and a little spring to retract them? That's different.
 
gitmo234 said:
Hey everyone,My question is: Could this be related to the weight of the snow?
Thanks
Click to expand...

NO.... your cable rigging is wrong, and the tension on the cables was wrong or it will never come off the pulleys.
 
gitmo234 said:
Issue resolved:

Pulley guards were all fine, but the mechanic diagnosed that with the weight of 6+ inches of snow, combined with my "horse assing" the handle to de-ice it, caused quite a bit of slack in the cable. It was off the pulley but within the pulley guard.
Click to expand...

Get a new mechanic, there is a cotter key placed in the pulley that prevents the cable from getting out of the pulley channel. But even when the cable tension is correct that will hold the cable in the pulley.
 
Aluminum aircraft shrink when they are very cold, aluminum shrinks more than steel, so the tension on cables is less on the cables in extreme cold weather.

But still should be tight enough to prevent the cables from coming off their pulleys, but just in case Cessna placed a safe guard on each pulley guard. a simple cotter key that prevents this.
 
Tom-D said:
what is that picture?
Click to expand...

I got that off the 'net, since there were no pictures of Cessna-specific pulley guards, and it looks much like the Lockheed Electra systems I used to work on. Large airplanes often use that spring-tube type guard; it comes out easily when required but stays put otherwise unless it's worn out. The picture shows one guard partially out, and was likely taken as an instructional picture.

Dan
 
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