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   b.    Mmc Probleas

Absolutely ~~al system.    ro~ those of you who are not aware of
aoee of our proble~ with the NBC syst~s o~t &t TuM,j please take
aot..

             The XlA! ~ system va~ constriactod o~t of oo=ponents
designed for an aircraft.  ~le they initially f~~nction properly,
the dust,  Shock and vibration of the I-r'~ *nvironaent literally
plugs and beats the syaten to death.     At ~ we e:~t a total
*yste failure *oiewhere boti~~en 1000 ~d 1500 ~lea,     or 100 and
150 engine hours froa a tank that coaaa~o£f of the Uson~l? line.

         2.     The  failures    are  i=ediate   and   potentially
catastrophic.   I "sponson ov~r temp"   light will CCztL* ON    the
Co=ando:' a panel, and within that ~~icle travtling 100 yards on
the ~ syst~ can be on fire.      When the X~C filters catch on fir~,
the  flames burn thro~~h the filter canisters and can burn the
drive:.   Zt is now np to the crew and the v.hicle fire suppression
system to keep- the entire vehicle from going up.

         ~.  Since the Co=~der many times rides with the upper
body ~ut of the t~rret hatch,    he cannot easily see ths warning
lights.   At ~G, our early warning system is essantially t~e C:2W
=embers thenselves who wear cooling vests to ~eep th.: cool.   Th~y
sense a sudden increase in the teaperature of the )~C air and shut
the system down i=c~iately!

         4.    The MIM   X~   aystea  suffers f~     three  prinary
probloms:

             `  ~l':~ed Precoolers.  Ambient air is drawn into the
sponson   box,  through a particle  separator and  through   a heat
exchai'ger.  Although the separator operates at approxizaately 92%
e~f.1  a lot of dust still gets drawn into this cooling syst~.
When the ~Mt exchanger is no longer able to purge the systen of
the  heat    (cooling down   the engine  bleed  air),   the  sy:t~
temperatures ~ic)~1y rise to over the ~eIting ta:~perature of th~
plastic tubes in the particle separator.    Zventually,  th~ heated
air starts the charcoal filters on fire.

The best prevention of this probl*:n, is to k~p ~~e ~hicIe out of
as ~ch dust as possible.     Run the system in a clcin environment
to purge dust out of the iponson box.    when doing any aainten~nce
on  the  system, clean the   dust  out of this heat  exchangQr  and
related parts.   z consider it nandatory to do this at 1500 ~£le or
se~ai-annual aaintenances.


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