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Subject: WWII   ICE
From: Shilling )
Date: Jan 19 1996
Newsgroups: rec.aviation.military

     Yes transports as well the bomber had pneumatic boot.
Incidently they were inflated from the pressure side of the
instrument vacuum pump, needing only a few pounds.  Depending upon
the wing span and number of engines, depended upon the number of
sets of boots that were installed.  In a twin engine plane such as
C-47 and C-46, there was an inboard section and an outboard
section.  Each section of boot, normally had three cells, and
inflation took place sequentially.  They were inflated in pairs,
first the inboard sets and then the outboard sets.  Each boot was
made up of three cells.  First the center cell was inflated, then
the two joining outer cells inflated. 

Pilots had to deal with three types of ice formation. Carburetor
ice, wing ice and windshield ice.  Ice could be in the form of rime
ice or clear ice.  Rime ice was not as difficult to remove since
its build up was normal on the leading edge of the wing, and could
be deiced by the pulsing of the boots.  Clear ice could occurred at
or slightly below freezing, It could form either on the leading
edge or worse, form behind the boot, run back onto the wing. 

There were two ways of dealing with ice, one was to deicing such as
removing it after it built up.  This deicing was accomplished as a
result of the boot pulsating.  The other was anti-icing such as
pumping anti-icing fluid on the windshield, prop and carburetor. 
Anti-icing fluid for the propeller was normally made up a mixture
of alcohol and glycerine.  Straight alcohol was used to deice the

Propellers didn't have boots. They had a slinger ring that
direction anti-icing fluid along the leading edge of each
propleller blade.  Some, not all of the propellers had a rubber
strip with molded groves to direct the anti-icing fluid down the
leading edge.

There was a knack of using the wing deicer boot.  They had to be
used intermittently.  If they were left on continuously Ice could
build up in front of the boot and its pulsing would be working
inside a pocket, not touching the ice.  The secret was to allow
just the right amount of ice to build up and then turn the boots
on.  Then turn then off until a sufficient amount had build up
again.  If one waited too long the boot didn't have enough force to
break the ice away and you were in deep do do.

Slightly more than six hundred airplane were lost flying the
"Hump," from India to China during the war.  It is estimated that
at least 300 of those that were lost, went down in the mountain due
to sever icing conditions.  In other words the ice build up became
so sever, and rapid, the deicer boots weren't able to hand the
build up.

Erik Shilling
Author, Destiny;
A Flying Tiger's 
Rendezvous With Fate.

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