L-1011 Avionics Bending: Collins Radio Altitude Tape - Power on Test (Video)

Matt Witlispach who is building an amazing 747 simulator (Matt, I should really get your web site URL so I can post it on here) sent me some additional information on the Collins Radio Altitude Indicator. I did a preliminary power on test of the tape electronics only to see if the tapes that I have for the L-1011 project are functional or require repair. And yes, all the ones I have powered up just fine.

Here are a few things about the test that you see in the video above. The Radio Altitude Indicator is powered from a 26VAC 400Hz source. The altitude valid signals are simulated from a 24VDC source. The FAULT FLAG in the video does not clear because the Decision Hight (DC) portion of the instrument is not powered (I have to do a little more research on that part).

The altitude information simulated from a National Instrument Multifunction DAQ 6024E card and covers a range of -10VDC to +10VDC. The instrument, however, requires a -30VDC to +30VDC input range for the entire altitude range ... for the final setup I will run the DAC output from the card through an OPAMP.

Avionics Bending: Radio Altimeter - Pinout

For today's pinout I have the pinout for a Collins Radio Company Radio Altitude Indicator type 339H-2. This one again is a unit that was very commonly found on Lockheed as well as Boeing aircraft. This device actually has a number of interesting functions, such as decision hight alert and a miniature airplane that moves with the decision height along the scale. See the functional description below.

The schematic of the instrument is pretty straight forward. There are some pins missing in the schematic ... namely the ones for instrument lighting.

Finally here is the collected pinout:

Format: Connector | Pin | Function

P3	B	28VAC Power
P3	G	Ind Maint. Annunciator +28V
P3	H	-30V
P3	J	+30V
P3	K	Comparator Warning
P3	M	Altitude Valid 28VDC
P3	Y	Auxiliary Altitude Value
P3	Z	Auxiliary Altitude - GND