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static line retriever problem


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I have a static line retriever that is blowing the current limiters anytime the switch is (bumped) it wont blow the limiter if you just hold the switch but it blows when the switch is bumped just to bring in the cable a bit at a time. We have new relays on order but has anyone ever had this problem?

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Yes I swapped out retrievers and it still blows the limiter. Changed both the unwind and rewind relays and still pops the limiter. You can hold the switch either to full unwind or rewind and it will not blow, but if you bump the switch 6 or 7 times pretty quick, it will blow before you know it. I dont see how it can be the control relay but that is the only thing left to change. I cleaned all the contacts including the common ground and it didn't help either.

Any other advice? This trainer is used for loadmaster training and has been a problem for quite a while.

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IMO it sounds like your power source may be the problem. If the voltage is low the retriever will pull more current. Bumping it may cause the current limiters to heat up and eventually blow. Put a meter on the limiters and see if you are getting a voltage drop between each phase and the ground and voltage drop between phases.

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pjvr99,

He already swapped out the retriever, that pretty much takes that motor out of the picture.

Circuit breakers and fuses are there to protect the wiring, not the component. I don't think it's a supply issue. Physically check the power wires from the retrievers to the fuses. There could be a chafed wire along the way.

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Tiny, you may be right in that he REPLACED the retriever, but the way he says it, sounds like

he only swapped left and right over, and the problem followed. Let's see if he has some more

info .....

Another thought: were the correct value limiters installed after the first set failed? I made

the same mistake last year with the GTC/APU test stand - fitted a 200A limiter instead

of 275A

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The aircraft has been converted to a loadmaster trainer and its tail # is 69-0949. I have ensured that a 80A current limiter is installed each time. I did swap the retrievers from R to L and the problem still remains on the LH side. The problem is always on the LH side. I'm Looking at the MD 4 (power unit) right now for possible voltage issues, but not sure. We have 3 trainers running off of 1 MD4 and you would think that if it were a power issue it would happen to another trainer. I unwound the winch while checking the phases on the generator and they remained consant without any fluctuation also.

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OK, here's why I think the fuse is blowing, or at least a feasable explaination. Of course, this may be all crap I just made up.

When you quickly bump the switch, the voltage in the motor winding keeps builds up, then collapses, builds up, collapses. When voltage in a coil collapses, its polarity is reversed. So, get lucky and bump quickly enough, and you have +28VDC going into a coil with a negative voltage on it.

Since the left side is used much more that the right side on a normal basis, and this has been done over many years, I think the left side 4 gauge wire has broken down somewhere and can't handle that current load caused by the switch bumping.

1. Tell the Loadies to stop bumping the switch or you'll paint their leather jackets with shiny black radome paint.

2. You could swap the 4 gauge wire at the fuses and C1 of the power relays. That will tell you if the wire is good. Even if both of them won't reach, you should be able to use one of those wires on the other system.

3. Install a 100 amp limiter and the exact problem will undoubtedly surface. Keep an extinguisher handy.

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  • 2 weeks later...

The initial start up current draw is much higher then a steady state (unwind/rewind) so if the switch is continuously cycled the heat build up in the current limiter (due to the higher initial current draw) will do just as you describe, cause the limiter to open.

As I see it the system is working as designed.... Not sure why you would need to cycle the switch 6 or 7 times in rapid succession but....

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NATOPS1, the AF uses the static line winches connected to a restraint strap cutter on CDS bundles as well as a static line retiever. During rigging the switch is bumped many times to take the slack out of the cable. The tension has to be just right when the drop is made as the winch only runs a few seconds when the copilot hits the green light . We have a FUT at Dobbins and the winches on it get a huge work out. When the winches were designed, they had only one function and that as we all know was to pull the static lines back inside the aircraft. An 80 amp limiter was good enough then...but with the additional requirement as a CDS strap cutter, the whole system is strained. There were 3 different brand of winches when I retired in 2003 and who is to say they were all built within the same tolerences as the original, supposed to but...... Also wear and tolerence creep of the electrical and mechanical components of the winch and wiring could total up to more than an 80 amp draw. 1038CC have ops notify you the next time they rig a CDS and eyeball the whole procedure. Also note how many turns of 80 lb. tape used to secure the static line cable to the winch cable. Might be an real eye opener to you. On a more humorous note, I was on a troopdrop at 29 Palms years ago and was standing under the left winch as the bags were being pulled and they caught on the ADS arm in the rear and it pulled the winch off of FS 245 before the load saw what was happening and let go of the switch.It never did blow the limiter. Bill

Edited by Spectre623
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