P-61 Gun-Laying Radar

[Zipper730]

There was a member here named Dana Bell who had been researching the P-61 since the 1970's: He talked about the P-61 being intended to have a type of gun-laying radar that would have constituted an effective blind-shooting system had it only worked.

Does anybody else have anything regarding why the gun-laying radar didn't work?

 

[Shortround6]

Ideas often outrun technical capability by years, sometimes decades.
Why couldn't they build a jet engine in 1910? They had the idea.

 

[wuzak]

The British hadn't told them how to make it yet....

Automatic Gun-Laying Turret - Wikipedia

 

[Capt. Vick]

Oh snap!

 

[Robert Porter]

Sneaky brits keeping the good stuff for themselves!

 

[Shortround6]

For the P-61 there are a number of questions.

1. Does the gun-laying radar have to be a separate unit from the search radar?
2. if so what is the drag of the new aerial/radar dome (at the tail of a four engine bomber the added drag is minimal.)
3. The gun-laying radar would only work on the turret mounted guns (four .50s) leaving the main armament (four 20mm cannon) unused.
4. if the forward "gunner" is tracking and trying to get firing solution using the gun laying radar and turret, who is watching the search radar?

 

[Dana Bell]

Hi all,

To be fair, I started researching American Mosquito night fighters back in the '70s; I was lucky enough to trip over a bunch of reports and memos on problems with the P-61.

I can't answer the first three of Shortround's questions, but the radar operator's original position was aft of the wing. There was a good bit of correspondence about moving the R/O forward to the gunner's seat when the turret was eliminated or fixed in place.

Despite a fascination with the P-61, I've still to start a serious dig into its full history - I'd need to drop some other project first, line up a publisher, and spend 10 to 12 full-time weeks digging through the National Archives citations I've found so far. Perhaps one day, if I'm lucky...

Cheers,


Dana

 

[Shortround6]

Thank you for the correction on the R/O seat.

 

[wuzak]

1. Does the gun-laying radar have to be a separate unit from the search radar?

I would suspect yes.

The SCR 720 radar had a conical field of view ahead of the aircraft. Using this would severely restrict the use of the gun-laying function.

I'm not sure if the P-61 had a tail warning radar, but it would also run into the same issues. And there is the matter of changing from one to the other.

Even with the main radar and rear warning radar being used together for gun laying there would be significant blind spots for the turret, which could cover 360° in azimuth and 90° in elevation, having a whole hemisphere of coverage.

The Lancaster installation above is ok as the gun laying radar would mach, or nearly enough, the range of motion of the turret and guns.

 

[XBe02Drvr]

The British hadn't told them how to make it yet....

Sneaky brits keeping the good stuff for themselves!

Do you ever wonder how people so advanced in their thinking they can come up with stuff like jet engines, fire control radar, angled carrier decks, optical landing systems, steam catapults, hydraulic arresting gear, etc, etc, etc,...ad infinitum, before anybody else, yet can't master such basic stuff as gaskets that don't leak and reliable generators, voltage regulators and aircraft and automotive electrical systems?
Cheers,
Wes

 

[Robert Porter]

Does make you think!

 

[Zipper730]

For the P-61 there are a number of questions.

1. Does the gun-laying radar have to be a separate unit from the search radar?
2. if so what is the drag of the new aerial/radar dome (at the tail of a four engine bomber the added drag is minimal.)
3. The gun-laying radar would only work on the turret mounted guns (four .50s) leaving the main armament (four 20mm cannon) unused.
4. if the forward "gunner" is tracking and trying to get firing solution using the gun laying radar and turret, who is watching the search radar?

1. Gun-Laying Radar & Search Radar Position: I thought the gun-laying radar was part of the P-61's main antenna?
2. Lancaster AGLT Radome: That has to do with the Avro Lancaster, not the P-61.
3. P-61 & Turret: I figure the turret could be used as a forward-firing blind-shooting system if it was pointed dead-ahead. My guess is that the azimuth and elevation would be combined with data including the aircraft's speed, g-load, and possibly the rate at which the turret is being moved. I could be wrong...
4. P-61 Crew Positions: The pilot sat up front, the gunner sat above and behind the pilot, and the radar operator sat in the rearmost seat at the back of the gondola. A transparency sat there.

To be fair, I started researching American Mosquito night fighters back in the '70s

I thought the USAAF only used the Mosquitos as photo-reconnaissance?

The SCR 720 radar had a conical field of view ahead of the aircraft. Using this would severely restrict the use of the gun-laying function.

1. What extent did the British have in the design of the SCR-720?
2. When you say "conical field of view" do you mean a spin-scan? I've never heard that before...

 

[fubar57]

USAAF 416th Night Fighter Squadron

 

[fubar57]

Not a happy ending I'm afraid...

MT482 - Missing 22.4.1945
Mosquito MT482, belonging to the 416th Night Fighter Squadron, missing in action on 22 April 1945 in North Italy. As stated by MACR #14065 <<2Lt. Wesley E. Kangas, pilot, and his radar observer, 2Lt Jack C. Herron, took off from Pontedera Air Base, Italy at 11:10 hrs 22 April 1945 for an armed recce of the Po Valley covering the Parma, Piacenza and Mantua area. Lt Kangas and his observer were due back at base at approximately 13:00 hours. When they did not return, 62nd Fighter Wing was notified by 3-2, this headquarters. 62nd Fighter Wing in turn notified Rhubarb and Blue Sector. Rhubarb tried to call them but received no answer. Lt Kangas and his observer were last sighted on take off at 11:10 hrs, 22 April 1945. No serach was conducted by this unit. No reports received by this headquarters from other aircraft covering same area.>>
Crew:
2Lt. (O-767265) Wesley Edward KANGAS (pilot) USAAF - killed
2Lt. ( O-870849) Jack Copeland HERRON (nav.) USAAF - killed

 

[wuzak]

1. What extent did the British have in the design of the SCR-720?
2. When you say "conical field of view" do you mean a spin-scan? I've never heard that before...

1. Ever heard of the cavity magnetron? Without it the SCR 720 would not have been possible. And the British gave the US one in 1940 in exchange for extra access to US industry.

[An early 10 kW version, built in England by the General Electric Company Research Laboratories, Wembley, London (not to be confused with the similarly named American company General Electric), was given to the US government in September 1940. The British magnetron was a thousand times more powerful than the best American transmitter at the time and produced accurate pulses. At the time the most powerful equivalent microwave producer available in the US (a klystron) had a power of only ten watts.

Cavity magnetron - Wikipedia

2. No, I did not mean that.

Search
Ranges: 1, 10, 20, and 100 statute miles. Azimuth Search: 180° forward sector. Elevation Search: operator may select any one of 4 sectors: 0° to 0° (level), -5° to +5°, +5° to +20° and +20° to +50°. In later models the ranges are changed to 5 miles, expanded sweep (dog leg), 10 20, and 100 statute miles.

US Night Fighter Radars of WWII

So, while not exactly conical, it was a limited field of view. And it certainly did not cover the turret's field of fire.[/QUOTE]

 

[wuzak]

P-61 & Turret: I figure the turret could be used as a forward-firing blind-shooting system if it was pointed dead-ahead. My guess is that the azimuth and elevation would be combined with data including the aircraft's speed, g-load, and possibly the rate at which the turret is being moved. I could be wrong...

If the target was dead ahead then why wouldn't you use the 4 x 20mm cannon? The pilot had his own viewer for the radar when he got into shooting range.

Not sure if the pilot's gun sight had some sort of indicator from the radar on it.

 

[Zipper730]

USAAF 416th Night Fighter Squadron

Did we call this airplane the F-8? Or something else?

 

[wuzak]

Lancaster AGLT Radome: That has to do with the Avro Lancaster, not the P-61.

Yes, but it is an example of a working WW2 gun laying radar system.

FWIW, America's Hundred Thousand does not mention a gun laying radar for the P-61. Both the gunner and radar operator could control the turret, each having a reflector gunsight.

 

[XBe02Drvr]

For the P-61 there are a number of questions.

1. Does the gun-laying radar have to be a separate unit from the search radar?
2. if so what is the drag of the new aerial/radar dome (at the tail of a four engine bomber the added drag is minimal.)
3. The gun-laying radar would only work on the turret mounted guns (four .50s) leaving the main armament (four 20mm cannon) unused.
4. if the forward "gunner" is tracking and trying to get firing solution using the gun laying radar and turret, who is watching the search radar?

We should get Token on here; he's a radar professional. Based on my 45-year-ancient experience with interceptor radars and my 50-year-old memory of P-61 magazine articles written when their veterans were still alive, here's my take on this radar.
1. The technology to put enough power into a small aerodynamically acceptable dish to be useful (The magnetron alluded to in this thread) was brand new on this side of the pond, and the implications and capabilities (like spin-scan and lock-on) were still being worked out. The earlier night fighter radars (forest of TV antennas type) could show you there was something out there and give you an approximate range and elevation, but it was up to the eagle eyes of the pilot to achieve a firing solution. The so-called "gun laying radar" was most likely what would be called today a fire control radar, and probably didn't integrate well with the search radars of the time. Thirty years and a lot of evolution separated those early radars from the integrated search-acquire-track-fire systems of my day.
2. Dish antennas are always a trade-off between drag and radiated power. If it's confined to finding a firing solution for 8 forward firing guns (turret locked), it doesn't need much power nor much angular flexibility, so it can be in a pretty small radome.
3. The utility of the swiveling turret in night fighter ops is limited to two scenarios: "bandit in our six", and "Get under the target and give 'em 'schrage musik'!" There's not going to be a radar-guided furball style dogfight at night. The technology is just not there. In visual conditions that swiveling turret could be devastating in a dogfight. There was a P-61 instructor on the west coast who used to take on (single-handed) four plane flights of any single engined fighters who wanted to come out and play. Scored camera "kills" on all four.....every time!
4. Not a concern. If the gunner needs to unlock the turret to deal with a bandit, he's strictly visual, as the radar is facing forward. Ditto for "schrage musik".
Cheers,
Wes

 

[Shortround6]

The SCR 720 radar in the P-61 could scan the forward 180 degrees horizontally but only about 25-30 degrees vertically at a time. The vertical travel could be adjusted to look below the horizontal. Max vertical travel seems to be from +20 degrees to + 50 degrees ??

If you want a radar gun sight for the turret covering any other arcs (the rear 180 degrees) you need a new radar scanner and black boxes.

And if you try to use the forward scanner/dish as a gun sight radar (it may be possible, I don't know) then it it is not scanning the sky looking for other aircraft during the time it is trying to be a radar gun sight.