[QCWA] The Correct Polarization Saves Lives in WW2

[Norm Gertz]

Walt....I'm thankful that you guys provided the necessary information for me 
to be able to safely fly  from  Honolullu to San Francisco in 1945 in a 
flying boat......we took off from the water off Barbers Point and landed in 
SF Bay.

73   Norm   K1AA


----- Original Message ----- 
From: "Walter Maxwell" <walt at w2du.com>
To: "QCWA Mailman" <qcwa at mailman.qth.net>
Sent: Friday, September 23, 2005 11:26 AM
Subject: [QCWA] The Correct Polarization Saves Lives in WW2


>     During WW2, Prose Walker, W4BW, (then W2BMX and later W0CXA) in 1942 
> became
> Chief of the Radio Security Center (RSC) of FCC's RID, located in the 
> Dillingham
> Building, Honolulu. (Long after WW2 Walker was Chief of the Amateur 
> Division of
> the FCC, succeeded by our John Johnston, W3BE, President of QCWA.) In his
> position as Chief RSC Walker learned that many military aircraft and its
> personnel were being lost at sea while traveling from the U.S. Mainland to
> Hawaii. There were two reasons for their being lost, 1) 'navigationally 
> impaired
> ' pilots (bureaucratese for 'lost'), and 2) totally drained fuel tanks. 
> There
> was naturally a limit to the size of the fuel tanks, but what caused the 
> pilots
> to become navigationally impaired? That point preyed on Walker's mind, and 
> on
> investigating he discovered a deplorable situation that needed fixing. 
> Here's
> what he found.
>
>     At the Boeing aircraft plant in Seattle they were building bombers as 
> fast
> as possible. Dozens of green flight teams just out of flight school were
> awaiting their new aircraft, and anxious to get aboard and proceed to the 
> South
> Pacific area as soon as possible. The navigators and radio operators were 
> taught
> how to use the loop direction finders that were standard equipment on the
> aircraft. But they were never told that loop DF's were incapable of 
> obtaining
> reliable directional information from signals propagated by sky waves. The 
> DF's
> aboard the aircraft were capable of delivering reliable data only when the
> electromagnetic energy in the received signals is vertically polarized, 
> but the
> navigators and radio ops didn't know that. Unfortunately for them, on 
> reflection
> and refraction through the ionosphere, a linearly-polarized wave is 
> converted
> into an elliptically-polarized wave, resulting in a continual shift in the 
> null
> obtained by the loop DF as the polarization angle of the incoming signal 
> rotates
> elliptically during propagation. Consequently, once the aircraft has left 
> the
> mainland, and can no longer receive the vertically polarized waves from AM
> broadcast stations, the only reception remaining is from sky waves 
> propagated
> far beyond the range of the ground waves of the AM stations. Therefore, 
> bearings
> taken from the loop DF's aboard the aircraft when at sea beyond the ground 
> wave
> signal were useless. The only remaining means for the navigator to 
> determine the
> position of the aircraft was through celestial navigation, using readings 
> from
> the sun or stars. The situation gets pretty bad on cloudy days, and that's 
> when
> the pilots became navigationally impaired.
>
>     At this point Walker came up with a solution that ended the era of 
> lost
> aircraft flying between the mainland and Hawaii. Fortunately, every FCC
> monitoring station in the U.S., Hawaii, Alaska, and Puerto Rico had Adcock
> direction finders as standard equipment. Adcocks, as you probably already 
> know,
> are susceptible only to the vertical component of the arriving wave, 
> regardless
> of its angle of polarization. Therefore, instead of constantly wandering, 
> as
> with the loop DF, the null obtained appears at constant angle on the 
> Adcock
> scale, even though the angle of polarization of the arriving wave is 
> continually
> rotating elliptically. In other words, Adcocks give accurate directional
> information obtained from sky waves. Walker's reasoning was that 
> triangulation
> from bearing measurements obtained by the FCC Adcocks taken on signals
> transmitted from the lost aircraft could determine its precise location, 
> and
> thus determine a course to fly directly toward Hickam Field in Honolulu. 
> The
> problem then was how to organize the communications to achieve the 
> necessary
> procedure. Walker organized it in this manner:
>
>     The CAA (then the Civil Aeronautics Administration) had a terminal in
> Honolulu with facilities for communicating with all aircraft. A direct 
> teletype
> connection was setup between the CAA and the RSC, which had a kilowatt
> transmitter used to communicate with the secondary monitoring stations on 
> all
> the Islands, each of which had Hallicrafters HT-9 transmitters. When the 
> pilot
> of the aircraft determined they were lost, the radio operator signals the 
> CAA,
> who instantly puts the aircraft's frequency on the teletype and rang its 
> bell,
> alerting the RSC operator of the situation. The RSC operator then sends 
> the
> following message to all secondary stations that continuously monitor the 
> RSC
> frequency: "LOS LOS LOS 4250 4250 4250," where LOS meant lost aircraft and 
> 4250
> was the frequency being transmitted by the aircraft. The operators of the 
> Adcock
> DF stations immediately tune to the 4250 KHz frequency, hears the 
> aircraft, and
> begins taking continuous bearings. The aircraft is sending long dashes, MO 
> MO
> MO, to enable the DF operators to be certain they're hearing the right 
> signal,
> and obtain a satisfactory bearing angle on a moderately constant signal.
>
>     As each bearing is taken by all stations, the bearing angles are
> transmitted to RSC, where a great circle map of the entire Hawaiian area 
> is
> hanging on the wall. A compass rose is printed on the map at the location 
> of
> every monitoring station in the Islands, with a hole in the center of the 
> rose
> through which a weighted string is hung. A pin is attached to the opposite 
> end
> of the string to secure the string at the desired point on the map, with 
> the
> string stretched over the angle on the compass rose indicating the angle 
> of the
> bearing obtained by that particular station. As the strings representing 
> each
> station reporting are secured they intersect at the point indicating the
> location of the lost aircraft, the intersection point called a 'cocked 
> hat'. It
> was usual for the aircraft's position to be determined within ten minutes 
> after
> the pilot alerted the CAA of its being lost.
>
>     After the aircraft's position is located it is then given a course to 
> fly
> toward Hickam Field, and the bearing measurements are reported continually 
> until
> the pilot can see the Field. During this time the aircraft's location is
> followed all the way in to the Field, thus verifying the accuracy of the 
> bearing
> measurements and the pilot's success in following the directions.
>
>     Once Walker's plan was in operation no more aircraft were lost while 
> flying
> between the mainland and the Hawaiian Islands. In 1943 alone, 273 aircraft 
> were
> saved by the FCC Adcocks, and more than 600 were saved during the duration 
> of
> the War.
>
>     Unfortunately, planes were continuing to be lost on the run between 
> Hawaii
> and the South Pacific, so Walker was invited by the Military to 
> investigate.
> What he found was almost unbelievable. The Army Air Corps was using 
> Mercator
> Projection maps for those runs, unaware that using maps of that projection
> produced directional errors of humongous and fatal proportions. On 
> Walker's
> advice, once they acquired new maps with great circle projection, the 
> number of
> lost planes dropped to zero.
>
>     This is just one of the stories of how the FCC assisted in the ending 
> of
> WW2. I was privileged to have been one of the bearing  takers.
>
>
>
> Walt, W2DU
>
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