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Throttle Creep


DanGothe
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Hello!

Has anyone ever experienced throttle creep? The problem we are having is that # 3 engine on acft 78000812 has a slight throttle creep when you pull the throttle lever up out of the ground idle detent and move it ahead 1/2 knob and let it go it will move on it's on without going into the flight idle detent. When it moves there is no change in engine settings all FF,TORQUE,RPM,TIT Remain the same.We checked the rigging and it was good all cable tension was dead on.We even changed the fuel control and coordinator and gimble assy. The problem is still there. I don't feel it is in the engine .Can anyone give me any input? You can email me at [email protected]

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Doubt seriously it's the VHousing.

Most of this can be pointed to cable tension or worn out parts.

First and foremost I would check would be the swing arm for worn out bushing or improper alignment .

Worn gimble parts such as the yoke is a culprit too.

I would also do a pull check per the rigging job guide.

Feel free to call the prop shop at the 302nd .

Edited by MAXTORQ
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In response to your query, the following information is provided.

1. The tension regulator assembly should be checked for correct part number and proper adjustment. The part number for the tension regulator assembly is R73-2004-42-3A, 695606-7.

2. The cable tension should be checked for equal tension on both the input and return cables throughout the cable system.

3. The cable rigging should also be RECHECKED from the quadrant to the gimble.

We experienced a similar situation of throttle creeping in the past. This problem occurred on older aircraft, which resulted in the rebuilding of the throttle quadrant assembly.

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My memory is very VERY bad on this one but I seem to remember something about the mount bracket for the beta feedback shaft had come loose so the beta feedback shaft had nothing to feedback to, this caused the linkage to try to hunt to match up the BFS. I don't remember any details or what exactly was wrong. But they found the mounting area completely messed up around the valve housing.

Probably barking up the wrong tree completely.

Like I said. it was a long time ago in a command far-far away.

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pjvr99,

I have recieved a lot of valuable info from you in the past. I am hoping now that you can do it again - would you be able to explain how a valve housing can cause throttle creep? I can't say that I have ever experienced that, but it is not at all unusual for me to find new and different problems.

Thanks in advance

Edited by Steve1300
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pjvr99,

I have recieved a lot of valuable info from you in the past. I am hoping now that you can do it again - would you be able to explain how a valve housing can cause throttle creep? I can't say that I have ever experienced that, but it is not at all unusual for me to find new and different problems.

Thanks in advance

Found the alpha shaft bearings were worn/loose, causing a creep to flight idle. Must admit

it took a loonnngggg time to figure it out. In fact the excess movement was spotted by

my apprentice.

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Thing is, when you're standing there looking at it, it doesn't make sense. How can something

so small and light have that effect? We had had some binding problems a few weeks earlier,

and spent some time getting all the pulleys lubed up, cleaned all the fairleads, got the

tensions just so ..... basically the throttle system was so smooth and easy, it felt like the

engine wasn't hooked up. So a little vibration had a lot of effect

One of those twice in a lifetime things :-)

On a similar vein, recently had a torque 'drift' at ground and flight idle. At either setting, the

torque would move up 400/500"lb and then go back down - a cycle of 30 seconds or thereabouts. Initially thought there may be something wrong with the pickup, but that

checked out ok, no oil build-up in torque tube, etc. Then I thought of wind, because we've

had a lot of tailwind recently. That theory went the way of the dinosaur on a windstill

morning.

I climbed up and just started poking at everything in sight. I realized that there was a lot

of slop between the RGB rig point and the valve housing. Found the backlash screw a

little loose, and the control universal joint worn out (out of my limit, at any rate). Fixed

them up, and steady torque after that. BTW, in my test cell, I have both a digital and

analogue torque indication

Bottom line is, never take anything for granted. Always question, always check.

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I know of two possibilities. One is damaged (broken or missing) springs that are used to balance the forces on the levers. This is fairly easy to spot if you take the cover off.

Second would be that the quadrant may be due an overhaul. I have tried for years to add quadrant overhauls to the PDM w/ no luck -- instead we do them "on-condition." Unfortunately, this often means you guys end up nursing loose or bound quadrants until we can get a UDLM team in place or limp into PDM. There are several drivers but the two most common problems in the quadrant that allows the levers to creep is either worn shims (pealable shims are used to set the gaps between each lever and these can become worn) or a worn shaft (that the levers ride on). Both conditions necessitate an overhaul.

A solution that some play with is snugging up on the friction knob -- got to be careful here because the intention of the friction knob is to increase the friction axially -- if the shaft is worn and you try to overcome this looseness by tightening the friction knob, you can accelerate the damage to the pealable shims and cause the levers to bind.

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Let us know what you did to fix it.. VH is my choice, since you checked every thing else out..

there is a team coming from depot to ck it out. We ran it with the prop linkage disconnected and it still had the creap so that explains why the team is coming in to ck out the throttle quadrant.

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Check the pulleys for splitting, especially the ones that are at FS245 above the T/Rs. There are 2 types of pulleys in the system; 1 is a plastic looking one and 1 is a reinforced phoenolic type. The plastic type are prone to splitting and the only way to tell is to relieve the tension and look for cracks in the groove with a flashlight and magnifying glass (if needed). You have to look close because it is easy to miss and the crack won't open up until there is a load on it. The pulleys can be at the bottom of FS 245 (16 each) and behind the life raft T-handles on the flight deck (16 each). It is critical that the tension is equal on the cables under the quadrant. This is a PITA to do. The thing to look at is what was done to the aircraft just prior to the throttle creep showing up?

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