Flight Control Failures?

[HeyEng]

So in regards to the little airplanes, how common are flight control failures? The cable systems are obviously very simple but I would think that there are more failures than there seem to be. I did a search on NTSB and found very few accidents that were attributed to flight control failure. Maybe I am just a little paranoid, but it seems like that the failure of a cable, or just the simple cable coming loose from a bell crank would be more common than it is.

 

[Douglas]

I have thought about that too.
But I have never heard or seen one personally.

 

[Roger, Roger]

Well, there was Sean Tucker's incident...
I can't get the NTSB report, their search site is running slower than molasses in January.

 

[HeyEng]

Well, there was Sean Tucker's incident...
I can't get the NTSB report, their search site is running slower than molasses in January.

I don't recall that one. I did come across one on a Piper Colt where the eye splice came loose from the cable and airplane made a gradual slow left descending turn and ultimately crashed and killed the pilot but not the one passenger. It was determined that the crimp was insufficient. Here is the part of the report...

The inboard end of the right aileron upper cable was missing its eye splice and thimble. The cable had an approximate 90-degree bend at the location corresponding to the eye, consistent with residual deformation associated with an eye loop. The cable separation did not exhibit any kinking or heavy rubbing. The other crimped sleeves (Nicropresses) in the aileron system were examined and their dimensions measured. Three of the sleeves from the four outboard aileron cables had crimp dimensions consistent with a properly installed sleeve, as specified in the control cable engineering drawings. However, the remaining three sleeves had crimp dimensions that did not conform to manufacturer's specifications. These nonconforming sleeves also had tooling markings that were not consistent with the use of the specified installation tool. One of these nonconforming sleeves was the remaining sleeve on the right aileron upper cable.

The strength of the remaining eye splices was tested. In a properly installed eye splice, the cable should fracture before pulling out of its corresponding sleeve. The aileron cables used had a specified limit load of 2,000 pounds. The remaining eye splice on the right aileron upper cable pulled out of its sleeve at 476 pounds. The other five eye splices tested held more than 1,600 pounds before failure occurred in the cable

 

[Orange Anchor]

Not a failure but I did have a cable on the 737 which was off the crank.. would roll nicely to one side but not the other.

Friend of mine was taxiing out and someone made the call, "Speedbrakes UP!" My friend, like everyone else, checked the speedbrake handle down. Everyone moved up in line and again the radio call, "Speedbrake UP!" Again my buddy checked his handle completely down. When he was number one, the call came but this time with the N number. My buddy opened his window and checked.. sure enough. the boards were UP. The cable had broken and the speeedbrakes had deployed.

 

[HeyEng]

Not a failure but I did have a cable on the 737 which was off the crank.. would roll nicely to one side but not the other.

Friend of mine was taxiing out and someone made the call, "Speedbrakes UP!" My friend, like everyone else, checked the speedbrake handle down. Everyone moved up in line and again the radio call, "Speedbrake UP!" Again my buddy checked his handle completely down. When he was number one, the call came but this time with the N number. My buddy opened his window and checked.. sure enough. the boards were UP. The cable had broken and the speeedbrakes had deployed.

That's kinda messed up. I would think that they would fail closed in the event of a cable failure.

 

[ppragman]

So in regards to the little airplanes, how common are flight control failures? The cable systems are obviously very simple but I would think that there are more failures than there seem to be. I did a search on NTSB and found very few accidents that were attributed to flight control failure. Maybe I am just a little paranoid, but it seems like that the failure of a cable, or just the simple cable coming loose from a bell crank would be more common than it is.

They're pretty bullet proof actually, never had a controll surface failure, but I know several people who had, the only one who had anything dramatic happen had an aileron fall off a beaver. Rolled him inverted, and crashed him in a lake. He survived, but it beat the hell out of him and his pax.

 

[Blackhawk]

Most of the ones I have heard of have been on airplanes that just came out of maintenance- eg., ailerons put on backwards, something not connected. Not a slam on mechanics- almost all that I have delt with are very good. They are human, however. That is why I am particularly careful on pre-flight if an airplane just came out of maintenance.

 

[Roger, Roger]

Here...this is what came up on Sean Tucker's incident. It sounds like an elevator cable snapped.
http://www.aero-news.net/index.cfm?ContentBlockID=ac50e14f-18e8-4ab0-a609-6e503d869141

 

[HeyEng]

Here...this is what came up on Sean Tucker's incident. It sounds like an elevator cable snapped.
http://www.aero-news.net/index.cfm?ContentBlockID=ac50e14f-18e8-4ab0-a609-6e503d869141

Actually, the NTSB report said it was the failure of the elevator push/pull rod. The rod-end bearing on one of the ends snapped off. The NTSB ordered some of the same bearings and are supposed to have a break force of 1500 LBS, but a couple of the six ordered sheared at less than 870 lbs or less!!! anic:

Here is the report:

http://ntsb.gov/ntsb/brief.asp?ev_id=20060405X00398&key=1

 

[Roger, Roger]

OK, thanks Galaxy. That right there would scare the bejabbers out of me.

 

[t-cart]

I broke a rudder cable in an Ag Cat one time. The left pedal went to the floor. Wasn't that big of a deal. I went over to the municipal airport and landed on the ramp into the wind.

The previous owner of my place dropped in over some trees one day and the elevator cable(old Ag Cat) snapped. Straight in he went. Didn't hurt him too bad. The newer ag planes all have torque tubes for the elevator control now.

 

[HeyEng]

OK, thanks Galaxy. That right there would scare the bejabbers out of me.

You and me both. One stupid failure...man that just ain't cool. I am a little curious if the part in question is sold as "approved" by the FAA. I know it was an experimental, but there was no mention if it was a PMAed part on not.

 

[HeyEng]

I broke a rudder cable in an Ag Cat one time. The left pedal went to the floor. Wasn't that big of a deal. I went over to the municipal airport and landed on the ramp into the wind.

The previous owner of my place dropped in over some trees one day and the elevator cable(old Ag Cat) snapped. Straight in he went. Didn't hurt him too bad. The newer ag planes all have torque tubes for the elevator control now.

D'oh! I don't think the rudder would bug TOO bad, but losing the elevator...that could make for a real bad day.

Most of the ones I have heard of have been on airplanes that just came out of maintenance- eg., ailerons put on backwards, something not connected. Not a slam on mechanics- almost all that I have delt with are very good. They are human, however. That is why I am particularly careful on pre-flight if an airplane just came out of maintenance.

I hadn't put too much thought into doing an owner-assisted annual, but I think it's not a bad idea. Obviously, I trust my IA, but nothing wrong with two sets of eyes on things. Besides, it's not as though he forgot to reconnect my landing light when he replaced the cowling last time!!!

 

[Orange Anchor]

I hadn't put too much thought into doing an owner-assisted annual, but I think it's not a bad idea.

Reminds me of the shop board that posts labor rates.
$75/hr if we do it
$100/hr if you watch
$150/hr if you help

The guy who does the annual on my Swift is, like the airplane, getting on in years so I get to twist into the cramped spaces at no extra charge. And you learn quickly the unwritten rule of airplanes assembled in those days.

1) if you can see it, you can not reach it.
2) if you can reach it, you can not see it.
3) before you can get to the part you want to work on, you have to removed X parts to get at it. The smaller the part you need to work on, the more parts have to be removed.
4) the smaller the part, the longer the part number.

 

[Roger, Roger]

Also this one...
Rule number 32 of aircraft maintenance...
"All aircraft components are easily replaced, provided you have an infinite supply of triple-jointed moisture-proof midgets with no sense of claustrophobia."

 

[t-cart]

Reminds me of the shop board that posts labor rates.
$75/hr if we do it
$100/hr if you watch
$150/hr if you help

The guy who does the annual on my Swift is, like the airplane, getting on in years so I get to twist into the cramped spaces at no extra charge. And you learn quickly the unwritten rule of airplanes assembled in those days.

1) if you can see it, you can not reach it.
2) if you can reach it, you can not see it.
3) before you can get to the part you want to work on, you have to removed X parts to get at it. The smaller the part you need to work on, the more parts have to be removed.
4) the smaller the part, the longer the part number.

Ha, Yeah most of the mechanics I know are what I would classify as professional cussers. After getting in a few spots like you describe, I can understand.

 

[Roger, Roger]

The part that breaks most often is always the part that was installed first, and had the rest of the airplane built around it.

 

[HeyEng]

Reminds me of the shop board that posts labor rates.
$75/hr if we do it
$100/hr if you watch
$150/hr if you help

The guy who does the annual on my Swift is, like the airplane, getting on in years so I get to twist into the cramped spaces at no extra charge. And you learn quickly the unwritten rule of airplanes assembled in those days.

1) if you can see it, you can not reach it.
2) if you can reach it, you can not see it.
3) before you can get to the part you want to work on, you have to removed X parts to get at it. The smaller the part you need to work on, the more parts have to be removed.
4) the smaller the part, the longer the part number.

HA!!! Yes, very true. The original shop I used had a similar policy. My arrangement now is much better. I share a hanger with an A&P who is business partners with an IA down the way. I do all the dirty work (pulling panels, etc.), my A&P buddy helps and assists me with the actual maintenance, the IA does what he does, and I put it all back together. Since I let the A&P buddy fly the plane on occasion, the annual and other maintenance is covered at no cost to me (well, I do pay for parts). Not a bad deal, huh? That doesn't include the 3 other guys that are begging for me to sell shares in the thing!!! Airplane ownership so far has been much better than what I thought it was going to be.

 

[matt152]

I had a the rudder cable fail on a 172 once. I think it just came off a pully. Was not a big deal, but it was a little weird to press on the rudder pedal and nothing happened.