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Hidden above the ceiling on Airbus and Boeing airframes, as well as on
many business jets, is VT Miltope's 802.11n Multifunction Access Point
(nMAP), critical hardware for the aircraft's LAN. The nMAP quietly
supports passenger Internet access and wirelessly connects crew systems
that monitor and control cabin temperature, meals data, and In-Flight
Entertainment (IFE) systems. It also wirelessly bridges the aircraft to
airport terminals, transferring maintenance data and crew support
information.
When developing its latest nMAP hardware, Miltope relied on Coolit to
predict overheating issues and prescribe design changes to keep the system
cool and problem free---all before any prototypes were built.
The hardware sits in stagnant air, relying on natural convection (at
up to 55C steady state; 71C for 30 minutes) and limited thermal
conduction into the aircraft support structure. Zero heat flux through
the mounting plate was specified for a worst case analysis. Coolit's
early predictions indicated that, without design changes, the processor,
radio cards, and Gigabit Ethernet chips would overheat.
Coolit's prescription was to add two custom conduction heat sinks to
pull heat away from the hard-working chips and radio cards and dump this
heat into the aluminum support chassis. When the conduction heat sinks
were modeled, Coolit predicted that all components would remain within
the manufacturer's specifications at maximum operating power-even without
any thermal conduction through the mounting plate.
Subsequent benchmark testing on prototype hardware verified that the
Coolit predictions were accurate, typically within a few degrees of
actual for most components. Predictions usually were on the high side
because worst-case steady state power dissipations were modeled versus
the lower and unpredictable power draws of the tested software
applications.
The nMAP teams up with other VT Miltope systems, such as Network
Server Unit (NSU) and Ethernet Switch Unit (ESU) in the aircraft's
equipment bay, a wireless Printer in the cockpit, Network Control Panel
in the galley, and an Airborne Telephony Server (ATS) that enables
passengers to use cell phones while aloft. Coolit also was used in the
design of these systems.
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