Flaps Inop

455 Bravo Uniform

455 Bravo Uniform

Final Approach
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455 Bravo Uniform
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Flaps are in the up position, do not come down.

Motor does not run when activation lever is moved. Circuit breaker is not popped. I can hear the detent on the up and down switches in the panel.

Question: what's the best and worst case in terms of parts cost and labor hours?

To the best of my ability, my guesses- Dead motor or something in the panel (bad switches, broken wiring) or follow-up system issue (which I don't fully understand the mechanics of).
 
Dunno, but this makes me thankful for the hydraulic flaps in my bird. Good luck, wish I could do more than be an asshat and brag.
 
Get out your multimeter and stand on your head under the panel. Just because you can hear the microswitches "click" (is that what you were saying) doesn't mean they're functioning. Just because the circuit breaker appears pushed doesn't mean it's passing current.

If all is well there, then you need to go out to the right wing. The motor is there along with two more switches.
 
micro switch....depends where you buy them. There are MS switches to be had for $30 or you can buy them from Cessna for $250 ea.
 
Our 172 had same failure, same description. Was micro switch as alluded to in above reply. Wasn't backbreaking. Was also exactly as described in parts, chose between Cessna switch at stupid money, or functionally identical switch for a fraction of the money.
 
Our 172M had same symptom which we traced to a bad crimp (from Cessna) under that RH wing cover.
 
You guys have mentioned the flap motor in the right hand wing...isn't there one in each wing?
(Yeah, I am serious...or seriously dumb)
 
No, not a dumb question. I had to look it up in the maint manual last night. One motor. Controls one pulley (cam?). That cam is tied with a cable to the pulley/cam in the other wing.

I am up for correction.
 
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Sinistar said:
You guys have mentioned the flap motor in the right hand wing...isn't there one in each wing?
(Yeah, I am serious...or seriously dumb)
Click to expand...

Only one motor on the Cessnas I am aware of, along with two limit switches. Always on the right side. This isn't uncommon in aircraft. You really don't want the possibility of one flap extending and the other not. Better to have one actuator and a mechanical linkage. The Navion flaps are actually bolted together and there's one hydraulic actuator in the middle (just behind the gear wells).
 
Timbeck2 said:
<---- thankful to have a long Johnson
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:yikes: You.didn't.say.that. Timothy!

oh-long-johnson-finally-made-it-on-a-movie_o_1473865.jpg
 
flyingron said:
Only one motor on the Cessnas I am aware of, along with two limit switches. Always on the right side.
Click to expand...
Mine is also on the right side ... when looking from the front. :D
Are all Cessnas expected to have the motor in the same place? Mine is in the port wing and linked with cables to the starboard flap.
 
Sinistar said:
You guys have mentioned the flap motor in the right hand wing...isn't there one in each wing?
(Yeah, I am serious...or seriously dumb)
Click to expand...

Asymmetric extension of the flaps is the sort of thing that kills people. One drive (hydraulic cylinder, electric motor, whatever) and mechanical linkage (torque tube, etc.) connecting the flaps to ensure they move in unison.

This year at annual inspection my mechanic found a hairline crack in one of the attach brackets riveted to the flap on one side. The first sentence in this post paraphrases what he said when he showed it to me. ;)
 
Thanks for the info. Single point of drive makes a lot of sense. At first I thought a single motor meant a direct shaft but that would be tough to span across the cockpit and would load unevenly. So, yet another cable in there I was never aware of!
 
The microswitches (there are two, up-limit and down-limit, IIRC) under the panel are the most likely cultprits. We've had issues with these twice in 13 years of ownership. The switches can be had for a not-outrageous price (see note above, but I don't recall where we got ours on the less-expensive side), and the labor is probably an hour-ish to diagnose and fix.
 
I would reach into the wing and try to turn the black plastic coupler between the motor and the gearbox, without any power on of course. You should be able turn it if nothing is jammed.
 
GRG55 said:
This year at annual inspection my mechanic found a hairline crack in one of the attach brackets riveted to the flap on one side. The first sentence in this post paraphrases what he said when he showed it to me. ;)
Click to expand...


Buy that man a beer
 
Sinistar said:
Thanks for the info. Single point of drive makes a lot of sense. At first I thought a single motor meant a direct shaft but that would be tough to span across the cockpit and would load unevenly. So, yet another cable in there I was never aware of!
Click to expand...

Many airplanes have a torque tube that span the width of the cabin to actuate the flaps. Cherokees, Aztecs, and Mooneys are airplanes that come to mind immediately...

Obviously Cessna's linear actuator and cable setup works, and works pretty well, but I've never been fond of the setup myself.
 
There are two microswitches on the flap motor assembly in the wing. They limit the travel of the actuator; not supposed to rely on the control lever switches for that.

Those two microswitches frequently get badly contaminated by oil used on the jackscrew. Mechanics don't read the manual, which says to clean off the jackscrew with a clean dry cloth, and apply No. 10 non-paraffin oil to the screw. A little bit of oil. The jackscrew uses a recirculating-ball mechanism that needs very little oil. But some guys take the LPS-2 spray can and hose the whole thing with it, and that stuff gets into the microswitches where it sludges everything up and fouls the contacts and the overcenter function of the switch. Some guys are still using moly disulfide grease on everything, which belongs in the really old systems. It really makes a mess. If the flaps won't come down, the down-limit switch is stuck open or its contacts aren't contacting.

C301002-0101_115.JPG


See those two rectangular aluminum blocks on that shaft? They have the limit switches on them, and the one on the right is the problem. It can often be cleaned if it's taken off, put into a small container of non-chlorinated brake cleaner, and worked a few times and blown out a few times.

Oct-2015-pic-1.png


Here's the typical system. Some, like the 210, are different but work the same. There are two cables, one to pull the left flap down and the other to pull it up. (The 210 has the motor in the left wing.) Those cables are a pain to inspect, being above the headliner, but are prone to wear at the small nylon pulleys on the fuselage centerline, and they can also corrode. A failed down-cable is a bad deal. Assymmetric flap, instantly.
 
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Had the same problem on a Bonanza, but stuck down. Turned out to be a bad wire between switch and motor for the up select. Put direct current to the motor to get the flaps up, labeled INOP, and a ferry permit to get the bird home.
 
overdrive148 said:
Buy that man a beer
Click to expand...

...Or three. No kidding!
He has eyes like a raptor. After we cleaned off the paint to expose the metal I had to use a magnifier to see the hairline crack clearly.
These old airplanes need constant attention to this sort of thing, so I am thankful he is meticulous.
 
Update:

Have power to switches, all switches check out fine (open and close internally), and motor operates up and down.

Once the flap goes all the way up, flaps become inoperable. You have to manually turn the flaps down just a tad, then the motor runs fine downward and fine upward, until it goes all the way up again.

Any ideas? Weak motor? Something out of adjustment? Still a possible bad switch?

By the way, I can't believe how small these motors are, I pictured something much bigger from the pics.
 
My q model had a loose wire crimp. Have someone run switch, jiggle wires.
 
It’s usually the microswitches. They like to fail during touch and goes. That’s why you always look outside to see if they’re really retracting every time.

Or if you decide to get lazy like me, you take off at about 40 indicated in ground effect and then land immediately. At night. Thankfully on a long enough runway to do that.

And don’t have to hope you can milk it around the pattern with flaps stuck at 40 at 6000’ MSL on a warm summer’s evening. :)

Cessna flap microswitches are bad juju. I can think of at least three circuits that would be a better replacement and not fail, but if you dared change it, you’d be an illegal experimental aircraft.

Because FAA is all about safety, of course. Ha. Those microswitches are certified (crap).
 
I had a flap bracket fail and one flap instantly blow up while at about 400 feet on final. I can confirm full aileron is not sufficient to overcome the instant roll rate. Fortunately I was flying a bird with stick flaps and not a motorized system, immediately dumped the handle to raise the good flap. And had enough airspeed with altitude to straighten the bird out. Made airobatic lessons appreciated! It was beyond an unusual attitude. Another case of God being with me in the cockpit.

The airplane was usually parked on the ramp, not hangared, where it was constantly subjected to wind elements that I think attributed to the bracket failure wth about 2000 hours on the airframe. Ever since then I am hesitant to apply more than 15 to 20 degrees of flaps unless they are really needed.
 
steingar said:
Dunno, but this makes me thankful for the hydraulic flaps in my bird. Good luck, wish I could do more than be an asshat and brag.
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Yes, because we all know that hydraulics never fail. :rolleyes2:

So how do the hydraulic flaps work in your plane? What powers the hydraulic pump?
 
Would bet that one side of the up limit switch is bad.
 
SkyDog58 said:
Yes, because we all know that hydraulics never fail. :rolleyes2:

So how do the hydraulic flaps work in your plane? What powers the hydraulic pump?
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I do. There's a little lever on the panel that gets pumped, twice for takeoff flaps, 4-5 times for landing flaps. Its just hydraulic lines and a cylinder. Of course, if the cylinder breaks I'm certain its made from unobtainium. But its just a cylinder.
 
steingar said:
I do. There's a little lever on the panel that gets pumped, twice for takeoff flaps, 4-5 times for landing flaps. Its just hydraulic lines and a cylinder. Of course, if the cylinder breaks I'm certain its made from unobtainium. But its just a cylinder.
Click to expand...

The ref has to throw the flag on the third pump...


LOL.
 
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