Saturday, April 24, 2010

Mi-24 Altimeter News, moving from 6 o'clock to 7 o'clock position

As part of the U.S. certification process for the Cold War Air Museum Mil Mi-24, the altimeter needed to be changed from meters to feet. While airspeed indicators can be remarked, altimeters have to be replaced because the equivalent gear ratio between the "big hand" and "little hand" is different for "English" (1 turn for every 1000 feet) and "Metric" (1 turn for every 3,281 feet) units.

The panel cutout for all of the altimeters in our Soviet helicopters has a teardrop shape, the barometric adjustment knob is at the "6 o'clock" position. It is located directly at the bottom of the instrument.

While many older U.S. Altimeters had an adjustment in this position, they are now non-standard and are much harder to find. While we recently purchased several rebuilt units for the helicopters, when one was installed in Bord 118, we found it already needed to be overhauled again. Essentially it had failed while "on the shelf". This caused us to look instead at modifying our panels to use the more readily available, more modern parts that have an adjustment knob at the "7 o'clock" position (drawn on the picture above).

Again, we are fortunate to have the resources to use our metal craftsman, Charles, who has done this kind of work before. In order to keep metal shavings or dust from getting into the instruments or switch panels, the area around and behind the panel was protected with plastic sheets or paper filler to catch the bits of metal being removed.

An altimeter with the "new" style adjustment is shown here temporarily mounted in the reworked panel. The old opening remaining below the altimeter will be covered with a filler plate.

No comments:

Post a Comment