Deice Boots Timing Cycle

[Paul Sharp]

I just had the boots on my plane replaced this year since the originals simply wore out. It is a 1967 T337B model. Sure love those boots! I haven't had to use them often but when you need them they are heavenly.

My question is that I noted the last trip when playing with them (it was VFR but I thought I'd run them a few times to inspect the new goods), I noted that sometimes the cyle would only last for 1 or 2 seconds. It is supposed to run for a nominal 6 second cycle.

It would appear to me that the timer is the culprit, but would appreciate input from others if they have ideas.

If the light stayed on longer than the inflation operated I would suspect a leak somewhere or possibly a messed up shuttle valve or something, but the boots actually inflate for just the amount of time the light stays on.

It was intermittent; most of the time the boots would cycle through the full 6 seconds or so (I didn't time it but you can count for a ballpark range for these kinds of short time periods).

If it does seem to indicate a time problem, does anyone know how difficult these items are to locate? I haven't asked Don Nieser or anyone else about a replacement part yet.

Thanks.

(And a Happy New Year to all, too!)

[Pete Somers]

Paul

6 secs sounds about right to me for a cycle of the boots, remember they are only there to crack the ice off the leading edge.
Also i have noticed that if you cycle them sometime the timer does not go back to zero and only cycles for a very short time.
It is just something about those timers.

Pete

[DHatfield]

Paul,

Note also that the light is activated by an air pressure switch, not by the timer itself.

The fact that the light illuminates indicates that the system is pressurized and the pressure is sufficient.

If you have a leak that only occurs when the system is under pressure, you might see the behavior you are seeing.


David

[Paul Sharp]

Thanks for the input.

I actually watched the boots and in the "short' cycle operations I saw - i.e., those that didn't go for the expected full 8 seconds, the boots didn't actually inflate all the way. So it seems to me that maybe the pressure is sufficient to activate the light, but doesn't operate for a long enough time to fully finish inflating the boots.

And in my past experience, the rear boot (on the stabilizer) inflates last, due to the pressure having to build up enough to get to it after the wing boots inflate.

But it's encouraging to know that others have seen this kind of behavior - namely that cycle not being the full length at times. Makes me think maybe I don't need to spend the money on a new timer.

[Roger]

Paul


If you find a timer/s at a reasonable price, or a place to have one repaired, please let me know (adivse the board) . Mine won't shut off. I have to kill the master. Even pulling the breaker doesn't work as it receives power frm another source as well

[Pete Somers]

Roger
The Timers on the 337H are adjustable.
Peel bacl the label with the p/n on it and you will see hole, use a flat bladed screwdriver and you can adjust the time it cycles on. It will take a couple of attempts to get it right.

There is no other source the valves can get power from, though pulling the C/B might cause the vacuum not to pull the boots in streamline, check all the valve work and are free to move this can be done without removiing them. On the top of the valve is a pin if you push it down with your finger it should return back when you let go. If it does not remove and clean the valve and pin.

Regards
Pete