nuckolls.bob(at)aeroelect
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 Posted: Sat Sep 19, 2020 9:54 am Post subject: Getting the numbers . . . |
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The image in his VAF thread shows V & I ranges; V variation is ~.3V; I is ~0--~10A.
The only 'device' I can think of that might cycle like that, at that wattage level, would be a heater circuit that had a controller capable of ramping power up/down in response to temp changes.
Oh...Pitot heat! Dynon and probably others now have temp controllers for their pitot heat. And the current is about right.
Charlie
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Aha! yeah . . . I'm betting it's pretty
simple. It's unfortunate that the condition
created so much work . . . especially doing
'swap-tronics'. I've always taught that
one should KNOW what needs to be removed
before picking up any wrenches.
Sometimes getting the numbers can be an
exercise . . . worked an intermittent
in the tail de-ice system on a Beechjet
that had grounded a revenue generating
airplane for over a month. Seems the problem
only manifested after 15 or 20 minutes at altitude.
A LOT of fuel and hours were consumed before
I was asked to join the search. We needed to
take measurements back in the 'hell hole'
just above the baggage compartment and
outside the pressure vessel.
Tried to capture the glitch with my laptop
DAS strapped down to the floor of the baggage.
compartment.
It takes quite awhile and lots of gas to
get to 41,000 feet . . . but about 12
minutes after leveling off, the system
glitched and we hoped to 'catch it' on the
DAS.
No joy . . . the heads on the lap-top's hard-
drive wouldn't 'fly' at 41K feet! That was
long before solid state hard drives.
http://aeroelectric.com/Pictures/Misc/RK371_Deice_A.JPG
http://aeroelectric.com/Pictures/Misc/RK371_Deice_B.JPG
http://aeroelectric.com/Pictures/Misc/RK371_Deice_C.JPG
http://aeroelectric.com/Pictures/Misc/RK371_Deice_D.JPG
Plan B: I built a breakout box that would let me
bring the sample leads out to a ribbon cable
routed through the baggage compartment
door gasket, taped to the fuselage and into
the cabin through the cabin door gasket.
Had to put an x-ticket on the airplane.
I could sit in the cabin and watch the
system parameters.
On flight #2, the system 'glitched' again and
the DAS was in my lap. Knew exactly which system
wire to scope out. Found a pushed back pin in a
pressure bulkhead connector that would de-mate as the wire
bundle contracted in the cold air.
Sometimes the simplest things can be exceedingly
expensive to find . . . in this instance it
was tens of killobux! But in this case,
as in virtually all others, known good
numbers are the key solving the most
intractable problems.
Bob . . .
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