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Ice detectors


trev130eng
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I have an on-going problem with the ice detection system switching it itself on in no icing conditions. I've swapped out everything in the system now and all wiring checks are good. The only spare ice detectors i have access to are coming from an aircraft where the system is known not to have worked in some time. In order to order new detectors i need to prove my current ones are unserviceable. Is there any bench check with a multimeter i can carry out to check the serviceability of ice detectors?

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I have an on-going problem with the ice detection system switching it itself on in no icing conditions. I've swapped out everything in the system now and all wiring checks are good. The only spare ice detectors i have access to are coming from an aircraft where the system is known not to have worked in some time. In order to order new detectors i need to prove my current ones are unserviceable. Is there any bench check with a multimeter i can carry out to check the serviceability of ice detectors?

With a multimeter, and a freezer....Check the circuit (well, really the thermostat); circuit must close on decreasing temperature of 52 plus or minus 5 degrees F. Circuit must open on an increasing temperature of 67 plus or minus 8 degrees F.

I have repaired and overhauled a lot of ice-detectors (092-000-001 and 575-315), but can't say I have ever seen one turn on by itself.

The only other possibility I can think of is that the tension spring is screwed down to tight, setting the switch nipple to close to the diaphragm, activating it inconsistently.

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We have mechanical ice detectors. 20 flights this week alone (paratroops) the ice detection system is turning itself on almost constantly. I am a C-130 ground test engineer. During ground test of the system, going to between reset and normal during test with the engines running the orange light should go on and off during the test cycle. This has never happenned. The on light goes off and stays off during the test cycle. Any help will be most appreciated. Flying with the a/c nearly everyday and seeing the problem.

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After takeoff pull the IGN control cber for # 2 and leave it pulled (untill you land or need to pull the fire handle OR get the ice detection turns itself ON)

See if the ice detection comes on in no ice condition.

If it does reset #2 IGN control Cb and pull #3 and leave it pulled (untill you land or need to pull the fire handle)

See if the ice detection comes on in no ice condition.

You should be able to see which one (2 or 3) is tripping your system.

do your engine inlets open when the ice detection turns itself on?

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Trev,

Keep in mind, I AM NOT a C-130 mech. My only involvement here is due to working for a company that manufactures C-130/T56 test gear. (Disclaimer)

When multiple failures of the same system or component have come up before;

1. We have had a bad batch of parts come through the system

2. There has been a change to the component limits (specifications) by the manufacturer without updating the T.O. (Causing the unit or system or test equipment to fail the unit for being out of limits.)

3. Bad test equipment

I’m not sure if this will help you, but it’s food for thought.

As an aside, corroded sockets and pins in a system create some real troubleshooting nightmares. Are you checking resistance as well as continuity?

Edited by jetcal1
Added test equipment to para 2.
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