1st operational AMTI radar on ?

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I will try to find a copy of "AWACS and Hawkeyes" by Edwin Leigh Armistead, MBI Publishing, ISBN 0-7603-1140-4.

As for the APS-26 Butterfly and APS-27 Firefly, they were originally developed by the MIT Radiation Laboratory as Project Butterfly and Project Firefly. They were transfered to the services when the RadLab was disestablished in 1945-6. The services passed the technology on to the ARL you mentioned and to others. Those folks undoubtedly made improvements, leading to potential disagreement over who "invented" what.

The APS-26 was eventually operational in 1951 as a close-in targeting radar for the Douglas F3D Skyknight while the APS-27 was eventually operational in 1952 on the Boeing B-52 Stratofortress.

There is, though, at least one claim they were operational before the end of WWII. Failing that, they may have been far enough along in development for air trials. If either is true, I would like to know the platform(s) used.

Not that it is important for me to know. I just find it frustrating that one can find so much information about the APS-20 but not the APS-26 or APS-27 until 1951/2. Seems like the information must be out there somewhere, mouldering away.

Thanks again,

The topic originator's initial posting had a VERY specific question.

"The first AMTI (airborne moving target indicator) radar, admittedly a noncoherent implementation, was operational by the end of WW II."

This is in fact NOT true.
The early AEW radars did not include any type of MTI. The wartime radar was the AN/APS-20.

NOT the AN/APS-27 which was mentioned in the initial posting.

American wartime aircraft that were being developed as AEW platforms included ...

Cadillac I Airborne Early Warning (AEW) Radar

In an effort to overcome the range limitations on low flying planes caused by the horizon, the MIT Radiation Laboratory began work on an Airborne Early Warning (AEW) system.’ The result was a one megawatt S-band radar with an eight foot antenna. This system was named Cadillac I after the radar test site on Mount Cadillac in Maine. The radar designated the AN/APS-20 was manufactured by General Electric. It was mounted in a TBM3W aircraft which was manufactured by a division of General Motors.


When operating at an altitude of ten thousand feet, the horizon is at about 120 miles. ship. The radar and IFF video were transmitted over a radio link and displayed aboard ship. A beacon on the control ship allowed an operator to track own ship’s position and to ground stabilize the displays of companion PPIs. Also, in order to control fighters beyond the ship’s radio horizon, a repeater installed in the aircraft could retransmit the VHF voice signal received from the ship to the fighters, and vice versa. The first AEW detachments, using these radars in TBM-3Ws, were being deployed to the Pacific theater when the war ended.

They saw NO action.

Also ...

During the war the Navy had begun using picket ships equipped with long range radar. These were stationed 50 to 100 miles from a task force in the direction from which targets were likely to approach. The picket ship had its own CIC to support its fighter aircraft in the interception of enemy targets. During the Okinawa campaign, the U.S. sustained heavy losses of the picket radar ships that were stationed off Okinawa to give early warning of Kamikaze raids.

As a result of this situation, the Navy decided to exploit the Cadillac AEW technology to provide airborne picket CIC stations for the invasion of Japan planned for November, 1945. B-17G aircraft were obtained from the Army Air Force for conversion by the Naval Air Development Unit at Weymouth, Mass. to airborne CIC’s. The antenna was mounted on the underside of the aircraft and the APS-20 radar was put in the radio room. The bomb bay was configured as the CIC room. This project started in February of 1945 and it was planned to have a squadron in operation nine months later. The crews and maintenance personnel were to be trained at AAF schools while the aircraft were being modified and deployed. The war ended before the first aircraft was completed. Eventually twenty aircraft were obtained and used at the Naval Air Station at Patuxent River, Maryland, to evaluate the radar and develop tactics.


Again they saw NO action. Nor were they Airborne MTI's. Nor were they the first AEW or AWACS platforms, developed or fielded during the war.

Sorry Yanks. but it was the British who first conceived, and made what is today AWACS.

The following passage is from "The History of the British Nightfighter 1935-1959. pages 089-190.

[The subject is countering air launched V-1's.]

"Although pulled back to airfields in Germany, KG 53 was not quite finished with the air launched missile programme. Firings continued throughout December and drew in another innovation as a counter to their attacks on Britain. Throughout 1941 and on into 1942 and 1943, the Telecommunications Research Establishment (TRE) had conducted a series of operational experiments using a Wellington bomber in the 'Air Control of Interception' (ACI) role, or what today would be called 'Airborne Early Warning' (AEW). First mooted in August 1941 by Watson Watt in his capacity as DCD, as a means of directing fighters onto the Focke Wulf Fw 200 Condor patrols in the North Atlantic, TRE had equipped Wellington Ic, R1629, with a rotating Yagi dipole array, an ASV Mk.II receiver, a special high powered transmitter and a nine inch (23cm) PPI display. Successfully trialled several times in 1942 and 1943, but dismantled in April 1943, R1629 was written off in a ground accident the following October. During January 1945 the Fighter Interception Development Squadron (FIDS), a part of the recently created Central Fighter Establishment (CFE) which was raised to supersede Fighter Interception Unit (FIU) in October 1944, undertook a series of trials at Ford and Manston in the ACI role under the codename Operation Vapour.

Using an ex-Coastal Command Wellington fitted with an ASV Mk.VI radar and PPI display, these trials were practised in the Channel during the hours of daylight in early January 1945 and flown operationally off the Dutch coast at very low level, in the company of five Mosquito night-fighters. Using the Rebecca/Eureka beacons system to maintain a formation, the set-up was controlled by a New Zealand civilian scientist, Mr E.J. Smith, from the Wellington, who provided vectors to likely targets for the accompanying Mosquitoes. Overall, the results proved disappointing since the sea returns restricted the ACI's maximum range when flying at low level, but ranges of 14 miles (22.5 km) were recorded at higher altitudes - which were twice as good as the Mosquito's AI Mk.X. However, at the critical point the Luftwaffe ceased air-launching operations on 14 January and the ACI project was allowed to fall into abeyance."

And now some images from - Radar Development to 1945, about the installation in the Wellington that was mentioned in the passage above.







There is also some information of the Wellington install of Air Control of Interception in the book - Pioneers of Radar, starting on page 168.
Any idea as to why on earth they dismantled this in April 1943? At first glance it looks as if we had continued we could have had something very special by mid-late 1944
Any idea as to why on earth they dismantled this in April 1943? At first glance it looks as if we had continued we could have had something very special by mid-late 1944

It was felt that the development of centimetric ACI would give much better results (it did eventually) but the US took control of that project. Continuing the development of metric ACI would give a useful system and good experience in actually getting around some of the problems leading to an easier transition to better ACI.
It was felt that the development of centimetric ACI would give much better results (it did eventually) but the US took control of that project. Continuing the development of metric ACI would give a useful system and good experience in actually getting around some of the problems leading to an easier transition to better ACI.

That is a pretty good suggestion, and I don't think that there is any fault with it. But I don't think that there is ever a single reason for anything, especially a decision. I don't think it explains why they did not continue to use the ACI Wellington. I think that there is something else involved. When AI moved to centimeter wavelength, the older sets were still employed and did useful work.

Recalling that they implemented the lashup in the first place to counter long range Luftwaffe aviation. (I.E. Fw-200 Condors etc.) I would suggest rather that the need for the setup was negated by the greater availability of suitable long range aircraft to counter the threat. For example Liberators of Coastal Command came into service in greater numbers. Or perhaps it was merely that the long range luftwaffe threat had diminished to the level of nuisance.

From the Luftwaffe War Diaries p 259 (the entire chapter actually. You can read most of it in the online preview via Google books if you do not have the book or cannot get it from your local library.)

"The Condor crews had to operate at the limit of their capacity. They represented Ihs cream of the bomber training schools, where trial crews were put together and their performance judged. And they learnt much from their senior colleagues, who as former Lufthansa pilots were already expert at blind and long-distance flying. Most successful operationally were Lieutcnam-Colonel Petersen —soon to command ihe whole KG 40 Geschwader—then his Gruppen and squadron commanders Verlohr, Daser, Buchholz. Jope and Mayr. The last iwo are still chief pilots with Lufthansa today.

Yet no string of individual performances could disguise the fact the main job of providing effective recconaissance for the U-boat arm could never be carried out so long as the number of serviceable aircraft could be counted on the fingers of one hand. In 1941 the monthly production of Focke-Wulf Condors amounted to only four or five, which represented no net increase. As the U-boats still sailed blindly through the seas, the following dialogue would take place each morning at
Donitz's war-room at Lorient between himself and his chief of operations, Commander Eberhardt Godt:

Donitz: "Are there any reconnaissance flights today?" Godl: "Jawohl, Herr Admiral,"
Donitz: "By how many aircraft?"
Godl: "By one. Heir Admiral."

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