Spelled out, it's an Autonomous Standby Power Supply Unit, and it's pretty similar to an EPSU - a control unit with attached batteries.  The ASPSU is used to supply power to the warning lights at all the aircraft exits, the emergency exists, and the cargo doors.  It also monitors the output of the differential pressure switch which shows a difference between the air pressure inside and outside the cabin.  During normal operation, the power for these lights comes from the aircraft's 28VDC supply.  The ASPSU monitors that supply, and if the voltage dips significantly or the supply is interrupted, the ASPSU switches to its own batteries which can supply power for about 50 minutes.  In doing so, it will bump up the voltage from the 6VDC of the batteries to the 28VDC the lights expect to see.   

The ASPSU is microprocessor-controlled and it will keep the two NiCad batteries optimally charged.  Those need to be treated like the EPSU batteries: with care!!  In fact, they are the same as the most common EPSU battery, the original 3214-30 or the new unitized design and less expensive 3214-1.  These batteries can be used interchangeably.

There are two ASPSU versions available from Diehl Aerospace Gmbh, both for use on Airbus aircraft.  The original unit is the 3214-90 which was designed for us on A300-600, A310 and A330/340 aircraft.  A newer unit (3214-91) was released in 1994 specifically for the A330/340.  It includes an RS232 communication interface and software that lets it talk to the aircraft's enhanced CIDS system. 

If you have questions on the use or maintenance of these products, please don't hesitate to contact us.  You can reach us by phone at 1-814-838-8934 or by email info@erieaviation.com.   

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