PA30 Throttle cable

[15384]

Need new right engine throttle cable. Anyone know where best or easiest place to get on Monday morning and have it overnighted to me?

John

[AlanBreen]

Hi John,

I'm not in the US so I'm not able to advise where to buy, but I wonder why you are looking for a new cable. They last very well and in my experience end up being replaced when there is no need to replace them.

I'm guessing that the throttle has gotten stiff to move. This stiffness is often caused by the two concentric tubes on the end of the cable becoming bent and this usually happens at the engine end (the same tubes are at the lever end as well and could be bent there if work has been done on the quadrant) after there has been work done on the engine. These two tubes slide, one inside the other, as the cable is moved. If they get a small bend in them they bind when that cable is operated.

A mechanic can inadvertently apply pressure to the tubes which working on something at the rear of the engine. The problem seems to be made worse when atmospheric temperatures cool down.

The bend in the tubes will be very slight and you will probably not see it easily at first. You can check for this problem by opening the throttle fully, to entend the tubes fully, and then rotating one or other or both tubes. They should be quite easy to turn with your fingers, unless the bend is bad then they may be a bit harder. If there is some bending present you will see the tubes wobble as you spin them.

The wobble will show you which way the tubes are bent, all you need to do is bend them in the opposite direction and you should find the stiffness is gone. I have fixed stiff throttles and prop cables by doing this, it's much quicker and easier than changing cables, I have done that too, before I figured out what the problem was.

I hope I have explained myself well enough for you to understand. Let me know if you need more help.

Good luck.

Alan Breen
ICS 14156

[15384]

Alan: Sometime during the overhaul process on my right engine the mechanic bent the throttle cable to the extent that the inside cable has a kink in it that causes a problem as it exits the collar of the outer sheath. I think it happened when we were hanging the engine back on the plane. I have tried bending it the opposite direction but because I can not see it I really don't know which angle it is bent. I have LPS2ed it and worked it by hand for hundreds of cycles to no avail.

So this is my dilemma. This problem shows up at idle position up until about 1100 RPM. The cable is stiff. So much so that I have to use both hands to get it to move when I am trying to reach a RPM in that range. Now if I was going balls to the wall full throttle with both like on take off it wouldn't be a problem or if I was chopping the throttles as when landing it wouldn't be a problem. It would be worse if the problem existed at the 25-2000 range and I am trying to sync the props.

John

[AlanBreen]

John,

I know what you mean about the stiffness. We replaced the mixture cables because one of them was like that. It was after that I realised what the problem was. We tried lubrication etc but to no avail. It's amazing what effect a small bend in those tubes has on the operation of the cable

From your description it sounds like you might need to new cable. They are not too bad to change, just takes a bit of time and you need to remove the interior front side panels and some of the floor panels from memory. Just make sure you pull a draw wire thru when you pull out the old cable, but you probably knew that.

I think the cables are a standard cable, I don't remember where we got ours from, but I would suggest Weebco as a first place to try. They advertise in the "Flyer".

Regards,
Alan

[15384]

Yep. Called them this morning. $175.00 I think it was.

Thanks for the information.

John