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Aircraft misbehaving .....


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Hey guys, need some thoughts here. One of our birds is throwing a

sh!t-fit, yawing to the left.

Initially, props \'n engines were blamed, but after we changed

the \'offending\' engine/prop combo and no result, the drawing board

was called on. Since then, we have had all the control surfaces off,

replaced the rudder, r/h aileron tab and l/h elevator tab. Also the

aircraft was put through a full symmetry check.

After todays FCF, the pilot told us he had to put in 7° rudder

trim to stay straight after T/O, reducing to 4° for level flight, or do

some serious pedal work. Also lined up torques at 14k and

reduced #3 and #4 to 9400 before yawing stopped.

Aircraft is a standard C130H.

Any ideas will be greatly appreciated .....

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Not sure that this is related but years ago before my Herc time, \'72 or so, I worked the RAM team out of Kelly AFB. We, me and 2 structural guys, went to Laughlin AFB to rebuild a T-38 that had handgrenaded an engine on TO and totally filled the back of the bird with holes. The AR struct guys had the job of patching the holes, I had to rebuild the aircraft systems and flight controls from the \"firewall\" back. We had to replace the vertical stab with one from a bone-yard bird. On FCF the bird had a similar flight characteristic, left yaw. They did a lot of checks, full symmetry check, etc., etc. Eventually it came down to the fuel vent on the trailing edge of the vertical stab was bent to the left a few degrees, giving the bird the left yaw. Once that was fixed the bird flew straight.

Anyone check out any kind of protrusions on the left side/wing? Hope this helps.

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A real challenge---Everything checked within limits on the symmetry check? Seems like a lot of rudder for correction.

Drastic move, but what if you swapped #1 & #4, and #2 & #3----that should eliminate or confirm the powerplant question.

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Has ALL rigging been checked? From the pedals to the pack, and throw checks done with each system isolated. Verify flap rig also, including ops check of assymetry system. I would think that out of sync flaps would induce more roll than yaw, but it is easy enough to check.

How about loose, bent, or otherwise unserviceable external tank components? Could remove them, and fly it slick once.

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Talon, I hear you on the engine swap, but I believe engines have been

eliminated on the last FCF.

KEF, she\'s going in for ISO and all cables etc will be replaced. I also

suggested your list of possiblities, so we\'ll see after ISO.

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Have you guys checked the flap rigging, I remember an AC that would yaw and was found the flaps were out of rig....dont remember the details.

Also you have external tanks right?

Sorry guys just saw the flap rig question...check and make sure your ext tanks are not loose....I had an IFR pod that was loose and wouls side slip in the airstream.....

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I agree that the flaps rigging is a very strong possibility. Because the bird is going into ISO, it probably doesn\'t make a lot of sense, and is not economically feasible to do a lot of checking up front.

So with the cables being replaced and alignment of the flight controls (including rigging of the flaps), the airplane just may emerge from ISO flying straight and true.

Please let the rest of us know how it comes out.....

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  • 4 weeks later...

Other (rare) things that would cause asymmetry like this would be:

Is 737 ring tight? has happened in the past where the entire empennage would twist inflight. I long had a habit of making the tail bounce when I was out at the tip of the horizontal stabilizer and found a couple loose over the years.

Or

How is the center wing attachment? We had problems like this but not quite as severe on one of our ABCCC many decades ago and they couldn\'t find out why. Well it was heading to Ontario for -15 engines, new outer wings and UARRSI so it pretty much got pushed to \"later\", the day after we dropped it off the engineers called us up to let us know that ALL of the smaller rivets attaching center wing to fuselage were sheared allowing the centerwing to shift inflight (Boy that was a post incident pucker factor). They said when they went to jack the plane the wing jacks kept going up and up and the fuselage was not lifting was the reason they found it.

Dan

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Just out of curiosity... Has anyone checked the rudder trim indication/rigging? Perhaps the trim tab is assisting the rudder in deflecting thus causing the aircraft to have an obscure yaw rate? Just a thought... I had this happen to an aircraft several years ago. E-model if I\'m not mistaken.

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are all the seals in that area good, what if something is freezing up during flight. seen this happen before both and a herk. The elevator trim actuator froze in flight at the higher altitudes but when dropping down below 10 they thaw out and work again.

when the actuator and cable was removed they filled the a bucket with the sludge from the tubing. lucky the B model was on a fairy flight for PDM.

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GCSTroop wrote:

Just out of curiosity... Has anyone checked the rudder trim indication/rigging? Perhaps the trim tab is assisting the rudder in deflecting thus causing the aircraft to have an obscure yaw rate? Just a thought... I had this happen to an aircraft several years ago. E-model if I\'m not mistaken.

Complete rudder replaced - out of balance, and could not be balanced

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pjvr99 wrote:

...After todays FCF, the pilot told us he had to put in 7° rudder

trim to stay straight after T/O, reducing to 4° for level flight, or do

some serious pedal work. Also lined up torques at 14k and

reduced #3 and #4 to 9400 before yawing stopped.

.....

Per my origional post - problem is worst at take-off

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  • 11 months later...

Sorry for resurrecting an old post...

The surfaces on the -130 don't have that much repair capability built into them. I've seen this on the ailerons more than any other FC. Every time a repair is riveted on, it is aft of the hinge line, and adds a tail heavy moment to the equation. What we have done to correct this condition is to replace the entire skin panel(s).

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Sorry for resurrecting an old post....

Don't be sorry, I should have reported back some time ago. We found a misaligned truss

mount, which cleared a lot of the problem after replacement. A number of very minor defects,

and 'within limits' decisions, came together to cause all this frustration. She has been flying

for several months without any further problems.

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Don't be sorry, I should have reported back some time ago. We found a misaligned truss

mount, which cleared a lot of the problem after replacement. A number of very minor defects,

and 'within limits' decisions, came together to cause all this frustration. She has been flying

for several months without any further problems.

Stacked tolerances....the bane of any troubleshooter.

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  • 2 months later...

A real challenge---Everything checked within limits on the symmetry check? Seems like a lot of rudder for correction.

Drastic move, but what if you swapped #1 & #4, and #2 & #3----that should eliminate or confirm the powerplant question.

Man I hope you are not serious about this. And if you are serious are you an engine troop that is due orders? If so what is your name so we can turn you down here!!!!!!! Fo the love of god how do your airplanes fly?????? Holy shit

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I agree that the flaps rigging is a very strong possibility. Because the bird is going into ISO, it probably doesn\'t make a lot of sense, and is not economically feasible to do a lot of checking up front.

So with the cables being replaced and alignment of the flight controls (including rigging of the flaps), the airplane just may emerge from ISO flying straight and true.

Please let the rest of us know how it comes out.....

Why the hell would you check flaps for yaw????? And why would you check your assemertry brakes. When was the last hard landing. Ohhhh by the way the flaps wont move if the brakes are set. Man I want to work with you guys I would be like a god!!!!!!!

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Cant hold my tounge on this one! Everyone on this thread has mentioned possibilities that can and do cause yaw problems in any flight phase. Did you read that it also had a roll associated with it? Even a fuel imbalance can cause this. Some of these people have more experience in their little finger than most will have in a lifetime. You wouldnt look like a god up against the person you are slamming, you would look like an idiot. But your already showing that brilliantly.

Regards John

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