Best air->air radar WWII

[kitplane01]

I think I already knew everything you wrote .. but I don't mind the review.

For something like a P-61, where the radar is using to find/localize the target, a range longer than 5 miles might be useful. And range ambiguity is not a problem with 1940s technology if you're only ranging out to 5 miles.

I agree not every radar needs uber-range, but some airplanes might have liked a range grater than 5 miles! Even if they are getting vectors from the ground.

 

[Token]

I think I already knew everything you wrote .. but I don't mind the review.

For something like a P-61, where the radar is using to find/localize the target, a range longer than 5 miles might be useful. And range ambiguity is not a problem with 1940s technology if you're only ranging out to 5 miles.

I agree not every radar needs uber-range, but some airplanes might have liked a range grater than 5 miles! Even if they are getting vectors from the ground.

The SCR-720 had 4 range settings, there is conflicting reports as to exactly what, in range, these settings were. The control panel I saw was marked (hand marked at each switch position) for 3, 10, 25 and 100 miles, but I have also read things saying 1, 10, 20, and 100 miles were the selectable ranges, 5, 10, 20, and 120 miles, and another report that indicates "the system was capable of tracking to the 120 nautical mile limit of the B scope when in RACON". The 1946 Military Airborne Radar Systems, Vol 2, states "26,000 feet, 10, 20, and 100 miles" as the four display options. While I have seen an SCR-720 in operation, it was not in its original configuration, so I cannot speak to the range it might have originally had.

I have seen indicators that, in radar mode, the 720 was good to about 18 miles on large aircraft, and 5 to 8 on fighter sized aircraft, longer on a tight multi aircraft formation and shorter on small aircraft or fabric skinned aircraft. This conflicts somewhat with a Naval operator I talked with. The SCR-720 was put on several US Navy ships, to give in-close coverage at higher elevations. From what I have been able to find, those radars were not improved or modified, and should have had the same performance as other -720's in use. Many years ago I had the fortune to work with a technician / operator that had been involved, first hand, with one of those installations. He stated they could track an F6F at ~12-15 miles. He was a great guy, a good tech also, but his ranges just don't jive with any printed data I can find, and I can't help but wonder if he was remembering tracking a pair / flight of aircraft.

T!

 

[JDCAVE]

The SCR-720 had 4 range settings, there is conflicting reports as to exactly what, in range, these settings were. The control panel I saw was marked (hand marked at each switch position) for 3, 10, 25 and 100 miles, but I have also read things saying 1, 10, 20, and 100 miles were the selectable ranges, 5, 10, 20, and 120 miles, and another report that indicates "the system was capable of tracking to the 120 nautical mile limit of the B scope when in RACON". The 1946 Military Airborne Radar Systems, Vol 2, states "26,000 feet, 10, 20, and 100 miles" as the four display options. While I have seen an SCR-720 in operation, it was not in its original configuration, so I cannot speak to the range it might have originally had.

I have seen indicators that, in radar mode, the 720 was good to about 18 miles on large aircraft, and 5 to 8 on fighter sized aircraft, longer on a tight multi aircraft formation and shorter on small aircraft or fabric skinned aircraft. This conflicts somewhat with a Naval operator I talked with. The SCR-720 was put on several US Navy ships, to give in-close coverage at higher elevations. From what I have been able to find, those radars were not improved or modified, and should have had the same performance as other -720's in use. Many years ago I had the fortune to work with a technician / operator that had been involved, first hand, with one of those installations. He stated they could track an F6F at ~12-15 miles. He was a great guy, a good tech also, but his ranges just don't jive with any printed data I can find, and I can't help but wonder if he was remembering tracking a pair / flight of aircraft.

T!

Interesting thread! Token has summarized the technical details on theses units. It's useful to look through the late war operational records that describe how they were utilized:

1) Successful interceptions seem to indicate a realistic operational range of about 4-6 miles. It's unlikely that a fighter would be able to close on any contact further afield. The records indicate that the Nachtjagd were alerted to radar interception and took evasive measures. Source: 406 Squadron ORB for March 1945.

2) The 100-Group ORB's record the challenges with making contact with the Nachtjagd. The February 1945 record records:
"During the month most of the supporting fighter patrols were flown well away from the bomber stream owing to the difficulty of operating A.I. in the midst of Window and bomber echoes. A number of sorties were, however, flown in the vicinity of the target areas during and after bombing and it is interesting to note that of the 11 claims by high level fighters 5 took place near the bomber target, and within a few minutes either way of bombing."

For March 1945 the 100-Group ORB records: "A new plan for close escort of the bombers by the high-level Mosquitos, discussed in last month's summary was put into operation in the early part of this month. A.I. Mark X can be used with success in close escort of the stream, if the patrols are flown above the bombers where the interference from Window and H2S is least. Most of the victories during the month have been obtained in the immediate vicinity of the bombers."

This alludes to the difficulty in finding the "signal" in the "noise" of battle. Most airborne targets were bombers. Finding a fighter in the midst of the "noise" was a challenge. Note the comment about H2S interference. 8-Group radar was operating on the 3-centimetre band so would cause potential interference on the AI units.

More on this, March 1945: "The main problem of fighter support of the bomber is still however, finding the enemy fighter and the number of suspicious contacts reported is small compared with the number of sorties sent out. The number of fighters the enemy operations on a particular night is comparatively small but that does not mean they are not formidable. Even two or three A.I. fighter can do great execution if they get into the bomber stream without hindrance. As it is of course, electrical and Window jamming reduce the potency of those fighter which may contact the stream but there is an adage that "prevention is better than cure".
I found the following really interesting:

"A most encouraging feature of the fighter operations has been the success of Perfectos, the homer on the enemy I.F.F. Four victories resulted from initial Perfectos contacts…There are also some other points of interest in these reports. In both cases night glasses were used to identify the target aircraft. There is no doubt now of the great value of night glasses to the fighter crews. The second report deals also with the destruction of an aircraft first seen taking off, which was probably a jet-assisted HE.219 equipped with rocket projectors."

Night Vision Glasses? Who'd a thunk it!

BTW, the jet-assisted He.219 is false. The aircraft shot down was a Mosquito on fire.

My own "personal" experience with radar is on the water. In some years, I have spent several months a year on the water. My unit is a Furuno 4' open array operating on the 10 centimetre band. The marine experience is in the pretty much in 2D dimension. Height is not a factor, except as it pertains to distance and the curvature of the earth. Airborne "targets" are readily identifiable by their speed, which is considerably faster than those on the water. But airborne interception is complicated by the need to operate in 3 dimensions. It would seem to me that distance and height can be confounded. Range. It is logical to me that the set operator must have had some experience determining the height of a target at range.

Jim

 

[yosimitesam]

According to Bill Gunston ('Night Fighters: A Development and Combat History'), the SCR-720 wins the contest hands down. From his book:

 

[JDCAVE]

The AI Mk X was definitely operational on 100-Group Mosquitoes in 1945. W/C Gibb of 239 Squadron, together with his set operator F/O "Killer" Kendall shot down 2 Ju.88's in he vicinity of Bohlen/Chemnitz on night, 5/6-March-1945 and they were equipped with this unit.

Jim