Interesting sidenote…

As a former navigator, this is an interesting little story… I’ve seen and used a driftmeter before, and when I retired, we were using prototype GPS units…

     A crucial part of flying is the ability to navigate, absent this flight is dangerous. In aviation’s early years, life-saving instruments were either crude or nonexistent. The lack of navigation equipment was the principal reason for the 32 men, out of 230 men, who lost their lives flying mail for the Post Office Department between 1918 and 1927. The lack of navigation equipment made flying mail for the Post Office Department just as dangerous as flying over the trenches during World War I.

     Prior to WW II, flying on instruments relied on dead reckoning making estimations of time-spent flying using basic questionable compass and primitive maps readings. Early instrumentation was primitive, altimeters weren’t accurate, if they worked at all. The reasons being for this was that when  flying in heavy fog or other vision obscuring conditions with no natural horizon for perspective, pilots quickly became disoriented, resulting with pilots flying into the ground while believing they were flying a safe altitude. Today navigating by visual reference to landmarks and dead reckoning are the primary tools used by pilots of recreational aircraft. In the days, leading up to World War II all pilots used this method, simply because there was nothing else to rely on.

     B-29’s relied on  Mount Fuji to be an ideal  navigational waypoint for bombing missions into Japan, being the highest mountain in Japan, rising to 12,388 feet  near the Pacific Ocean coast in Yamanashi and Shizuoka ken (prefectures) of central Honshu, about 60 miles west of the Tokyo-Yokohama metropolitan area, and can be seen from the  city on a clear day. B-29’s were required to use dead reckoning navigation over the ocean, and land when forward based in China, and the Marianna’s, and this worked as long as the navigators use of their Astrodomes was not obscured by clouds, which limited the  ability to track the sun, stars, and land navigational waypoints. 

     The B-29’s were designed with a radical navigational innovation being the Automatic Position Indicator produced by The Eclipse-Pioneer Division of Bendix Aviation Corporation. This was a navigator’s companion to the autopilot, and for the first time in aviation or marine history, a device could provide continuous readings of latitude and longitude regardless of speed or drift.

      The brain of the API was a self-contained device, mounted on the instrument panel, and automatically performed all of the computing, calculating, and indicating functions. It instantaneously made calculations, which would have required the navigator to work for hours with charts, basic navigational reference books, star-sighting sextants, a chronometer, and parallel rules and dividers to calculate the position of the aircraft in flight. This system used a remote indicating earth induction compass and consisted of four main parts:

·       A fluxgate which was a transmitter, a horizon gyro, an amplifier, and a master compass located in the navigators position.

·       The fluxgate measured the directive force of the earth’s magnetic field determining the aircraft’s position relative to the azimuth relation of the flux gate to the earth’s directive magnetic force.

·       As the aircraft would change direction, the angular relation of the fluxgate to the earth’s magnetic field was altered and this would provide new navigation data.[ii]

     Two indicating counters, set in an instrument panel compass dial, indicated degrees of latitude and longitude and gave the navigator an exact and con­t­inuous reading of his position. This same dial also gave the navigator a distance measuring (DME) cont­inuous record of nautical air miles flown, radio ranging, and indicated the corr­ect compass heading of the aircraft. From these readings plus a check of the drift meter, the navigator could pin point his position immediately on the map.

Several problems were encountered with the API instrument itself.

·       The problems were that the navigation computer failed to operate properly because of failures of the air mileage unit to transfer its power to the computer due to a shearing of the shaft from the gear to which it was attached in the pump units.

·       The system was designed to work with a west to east calibration for a European Theater, and it required a North South recalibration to bomb from the Marianna’s. 

·       This caused the computer to fail to follow the compass in one direction.

·       This caused the latitude and longitude readings to be in error while the compass read correctly.

·       The recommended solution was for specially trained personnel to calibrate, maintain and repair the API.

·       In a letter to the Commanding General of the AAF dated February 22, 1944, the 20th Bomber Command recommended that four “compass adjusters” be assigned to each engineering squadron of the service group, special, by addition to the Table of Organization.

·       It was suggested that these “compass adjusters” should be specially trained in the maintenance and repair of the API. By May 26, 1944, problems with the API system were still unsolved when four API units had failed. The approximate flying time was 50 hours and all API use was dis­continued on this date. By June 26, 1944, no reply was received by the 20th BC head­quarters on any action by the ATSC to fulfill the requirement for “compass adjusters”. By December 27, 1944, about 70% of the API equipment was still inoperable because of a complete lack of spares for fluxgate and API units.

     The majority of API units had arrived in theater with broken vacuum tubes, and other physical damages, rendering them inoperable. The majority of the navigation personnel stressed the desirability of having this equipment during individual flights such as photoreconnaissance flights and for formation leaders on bombing missions, in view of the absence of checkpoints in the broad Pacific. Wartime shortages left only one Pioneer technical representative available in the CBI Theater.

·       It was considered imperative that at least one additional representative be made available to the 73rd Bomber Wing as well as additional trained ground personnel since the training of the ground echelons on this equipment had been inadequate.

·       The training of the navigators in the use of the API and in the accomplishment of minor maintenance, such as the location and installation of the fuses, needed to be improved.

·       Each airplane needed three each of the compass and repeater units installed in it.

·       The only reason that any of the equipment was still in operation was that the technical representative brought along spares.

       The failure to solve the problems with the API would negate the value this innovation would contribute to B-29 operations.

·       The global Army Airways Communications System (AACS) would eventually provide radio ranging, and weather reports, for air traffic navigation.

·       Radio ranging worked through Loran allowing a navigator to determine his position through the time displacement between radio signals from two known radio stations.

·       By December of 1944, the AACS system had begun to expand to cover all Pacific Allied areas of operation, to include Japan by late in the war.  

     The impact of this was that the B-29 attacks on Japan, and Japanese held Manchuria, were not able to use the API navigation to the target being forced to rely on  full moon’s and good weather which permitting dead reckoning, absent the API, and celestial fixes along the route. Radar bombing which was in its infancy, which helped to provide navigational direction once over land with early positive results demonstrating improvements in navigation and bombing accuracy. GPS navigation would be the solution decades after the war, providing accuracy to within three yards sufficient for all weather navigation.


Interesting sidenote… — 13 Comments

  1. Ooh. Thanks.

    Would not have realized I had an interest in this if you hadn’t mentioned it.

  2. I didn’t know any of that, except for Loran, which we used before GPS, which is a very late arrival. Thank you for the history lesson.

    The B-29 missions over Japan, the development of the runway infrastructure that would handle the beasts, and the rapid development of the military machine necessary to beat the Japanese (such a different war than the one in Europe) is astonishing in its detail.

    • Those arrows are still a favorite of ‘Ancient Alien’ freaks who believe they were put in place by the USAAC and CIA and OSS to provide directions for UFOs and Nazis flying their own circular repulsion vehicles. Seriously. Not kidding.

      No matter how many times people point out the truth, the freaky alien people still continue to ‘believe’ as ‘the truth is out there.’

      Gak. Gag.

      As to fixing the nav system, the Navy worked very hard to have ships in place to serve as beacons at appropriate locations for both bombers, fighters and the rescue planes. Kind of like the radar picket ships, but navigation picket ships. Not a very workable system with enemy subs all over the place, but, wartime, ya gotta do what ya gotta do.

  3. And all of this children is why we have enlisted AC’s (Air Traffic Controllers) to tell Ossifer’s; mostly college educated, but some Academy trained, pilot’s where to go. Any idiot can land on 12,000 feet in broad daylight, the Air Farce does it all the time, but it takes a real wacko to land in 300 feet on a moving, pitching and rolling island in the middle of nowhere a night in a Cat 5 hurricane (BTDT,I got a night trap (was supposed to be a “pinkie”) in an A6 one time. FLY NAVY!

  4. So the Pommy H2S radar and Pathfinder stream marker method didn’t make it to the game, but somehow Tokyo later got firebombed anyway to the largest Bodycount of any air-attack (sans meaningful FlaK/NF opposition), ok at 10,000ft at night…..;

    Please, continue this narrative, and include the benefit of total economic paralysis on account of unrestricted submarine warfare (Bad when the enemy almost does it, but never as well!!), and political manipulation of the record, and what’s a burnt Jap family worth against FDR’s pawns to save Unca Joe?

    How far along were embryonic Loran systems at this time, and the copied German systems? Were all those Radar Picket subs and cans really only there to protect against kamikazes, or did they do a little traffic directing? The white hat looks a little greyer, when one looks a little closer…

  5. Interesting stuff.
    In the EH60s we had a built in inertial nav system as part of the DF system, the pilots didn’t care what kind of flight mission it was, they always wanted one of us MI Geeks sitting in that seat so they could use it, even when they started installing a GPS unit up front.
    Those early GPS units were a pain to use, we had the “plugger” and the “slugger”, which IIRC, were “Platoon” and “Squad”, respectively. The Slugger could be handheld and was battery powered, but the Plugger required vehicle or “shore” power. They both had little tiny text-only displays, and the Plugger read out was so small that even after I got my first pair of bifocals I couldn’t make out what it said when mounted.
    (And then there was the tendency to as-you-me that any Senior NCO — especially an MI Geek! — already knew this high speed stuff and didn’t need to be trained on it…)
    This was all before “W” lifted the restrictions on civilian use of GPS with accuracy better than 100 meters, or whatever it had been. Garmin should have him on their Christmas Card list…

  6. When I was young (I’m really old), we used to carry and use the cat and duck method of controlled flight into bad weather conditions, in other words when ground reference were lost. We’d try to avoid the bad weather, but sometimes we were overcome by events (OBE), and when the situation was hopelessly grim, we’d toss the cat out first. As you know, cat’s always land on their feet, so it was immediately clear which way was up. Next, out goes the duck. Ducks fly north in summer, and south in winter, so instantly, we knew which way to go. I still have stains and scratches in my flight jacket to prove it!

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