Wherewhendid dual speed on ias come from

Steven P. McNicoll
Steven gave a wonderful presentation as to the conflict of statute
and nautical miles to be used in the U.S. during the 1950s to 70s. What he
failed to give us who the genius was to come up with both sets of numbers on
our airspeed indicators.

The main push for a KNOT measure of aircraft speed came from the use of DME
in military aircraft which was always slant range to a
military VOR known as a TACAN."

It may be of interest that the use of Distance Measuring Equipment
or DME was derived during the last few months of WWII from a radar set known
as the APQ-23. The -23 was able to give an odomenter like read-out as to
the exact slant range distance from the bomb release point to planned impact
point. The trigonometry to do this was electronically done by using taps
taken from wire wound resistors. So difficult to do that there were only
six APQ-23s in the Pacific when the war ended. Getting both statudte and
nautical distances would have more than doubled the complexity of the -23 .
Hence the conflict between AOPA and the military in Steven's email.

As a corporal, I had the APQ-23 installed on my Supersonic Trainer on Tinian
to simulate flights in the vicinity of Nagasaki
for radar bombardment practice. The Nagasaki chart I used and
the manual to the simulator are on my web site. The manual displays the
equipment and I have written explanations of the pictures.
www.whittsflying.com
On the home page click on the sixth blue line down: Gene Whitt's WWII.
Page 8.935 is the WWII aeronautical chart can be expanded and moved. Go to
right side.
Page 8.935 is annotated pictorial Supersonic trainer manual.

The APQ-23 was standard equipment in the post-war B-47 jet bomber.