P-61 Gun-Laying Radar

[Shortround6]

Had they ever expressed a lack of interest in the turret? Retroactively, I know their interest had faded with time...

There was a mock up of a Mosquito with a turret and one if not Beaufighters were built with turrets.

One could use the same argument for the NF Mosquito... as time goes on, it's generally natural to try and squeeze as much speed and altitude out of a design. This is for numerous reasons, the first being that threats improve with time.

The Mosquito didn't get a two stage supercharger for several years. Altitude performance of a single Stage Merlin was good but critical height (FTH) was around 21-22,000ft.

[QUOTE ] Additionally, I figure a turbocharger would add range[/QUOTE]
It turns out they they did but that was unknown during the planning stages.

[QUOTE ] I honestly have little knowledge as to the P-47's issues with its turbocharger.
That's a good observation, I missed that: Regardless, the P-47M was available by 1944 right?[/QUOTE]

Most of the troubles were in the P-47B version which stayed stateside as trainers (and development aircraft) The P-47 was the first version to go overseas after more than 500 "B"s were built.
Even as a rush job the first P-47Ms didn't make to England until Dec of 1944. And they had so much trouble with them that they weren't declared operational until March or April of 1945.

We have to be careful with the "Retrospectoscope". We know when different engines or fuels became available. In 1941 when decisions on which engine to use had to be made they had no practical experience with either engine and no firm idea when improved models would be available.

 

[Token]

I'm guessing RAND took over from 1945-1958?

RAND was, and is, not a government entity or office, it is essentially a civilian think tank, partially funded by the US Gov. OSRD and NDRC, and later DARPA, were / are government offices.

So it had to do with being able to maintain the bigger picture...

Possibly, as I said, conjecture. Given the limitations of the day I would probably opt for the AI radar myself, vs the AGL, in a fighter application.

Was this known to be a limitation as it was being developed? Because I'm just thinking about the whole turret-fighter, and it seems completely absurd without auto-track (and the limitations make auto-track less than ideally desirable).

Possibly, or maybe they thought it was something they would evolve past in short time. But again, did they know how a turret fighter would be used? Did the facts of how they were used change during the development phase of the P-61?


You can sometimes have seemingly great ideas in the early phases of a project, only to find that there are easier and less complex ways to achieve the same end goal or another end goal that is just as effective in the long run.


US military technological application during WW II was an example of risk management and logistical returns on investment. The US did not always field or go with the most advanced systems, rather tended to go with the most advanced that could be fielded in the largest numbers the quickest and for the best cost. 20,000 decent fighters by a certain date and cost often beats 1,000 outstanding fighters by the same date and cost.


Talking about fighters specifically, I think the above is what happened with the P-51 vs the P-38 in Europe. The P-38 was more capable early on, but the P-51 was less expensive and easier to make, and would be less expensive and easier to maintain. It made more sense to develop the P-51 into the long range escort fighter it would eventually become rather than to try to do the same thing with the P-38, even though there is no doubt the P-38 could have been made to get the ranges needed.

You wrote in reply #112


"Between the Rad Lab, Bell Labs, and Western Electric they moved pretty quick.


From very early 1941 on auto tracking radar was a done deal, it was just a matter of refinement, so planning for an auto tracking radar in the P-61 in late 1940 / early 1941 was ambitious, but not beyond reason or even particularly risky, although the final form would not yet be known. Planning for one in early 1942 was very safe, the techniques had already been proven and were now ready for production in another system, essentially all that had to be done was trim down the equipment for use in an aircraft. At this point a fairly clear picture of what the equipment on the aircraft would eventually look like had to exist."


I figured, what you said in reply #112, that they basically had a fairly clear picture of what the radar-equipment would look like.

What I wrote in #112 had to do with generalities, how the system would basically function and that the process was possible. To standardize, modularize, etc, you need a deeper understanding.


Look at where I said " although the final form would not yet be known". You can't standardize if you have no concept of the final form. I also said "At this point a fairly clear picture of what the equipment on the aircraft would eventually look like had to exist." By this I meant that they knew they could do it in a parabola of X size, with displays of Y and Z types. But that does not tell you how to modularize the transmitter, the HV section, the receiver, etc.


Naturally you CAN drive those parameters with design specifications, tell the vendors "you must produce a transmitter in this many square inches, using these connectors and mounting points". However that will generally delay delivery. The vendor must first overcome the technological issues, and then meet your packaging specifications rather than just generally making it fit. Not hard to do with mature technology, a major pain in the butt if you are the first one ever to do it.


WW II was not about delaying delivery, if at all possible.

So confusion is better to obscure numbers, deception is to avoid getting shot once they realize you are present?

As a general statement, sure. But in the world of EW you want to keep clear of sweeping, defining, statements like that. What applies in one situation may not in another. Adaptability is a key.

Okay, so you use the optics to triangulate the range coordinate and the X & Y from the radar and pop off the SAM?

I don't think anyone ever used such a solution in a fielded SAM system, but I do know it was used in some gun systems. Optics have been and are used in SAM systems, but I can't think of one that used optical range finding.


T!

 

[Zipper730]

RAND was, and is, not a government entity or office, it is essentially a civilian think tank, partially funded by the US Gov.

That I actually know, but I just figured the functions of NDRC were fulfilled by RAND.

OSRD and NDRC, and later DARPA, were / are government offices.

How did OSRD compare to NDRC?

What was the point of RAND? There didn't seem to be anything they could do that a think-tank under more direct governmental control could achieve.

Possibly, as I said, conjecture.

True enough

Given the limitations of the day I would probably opt for the AI radar myself, vs the AGL, in a fighter application.

Unless you had some kind of mix of hunter-killer teams where the SCR-720 equipped aircraft were the hunters and the APG-2's were the killers.

Possibly, or maybe they thought it was something they would evolve past in short time.

If they figured the limitations could be overcome it makes a little more sense that they would go with it (if they didn't, it'd be rather hard to excuse).

But again, did they know how a turret fighter would be used?

Didn't the RAF tell us that?

You can sometimes have seemingly great ideas in the early phases of a project, only to find that there are easier and less complex ways to achieve the same end goal or another end goal that is just as effective in the long run.

That's why it's important to adjust as you go develop. From what I remember, the F-15 originally had a much more complicated electronic warfare system: Intelligence data on the USSR showed it was unnecessary.

US military technological application during WW II was an example of risk management and logistical returns on investment. The US did not always field or go with the most advanced systems, rather tended to go with the most advanced that could be fielded in the largest numbers the quickest and for the best cost. 20,000 decent fighters by a certain date and cost often beats 1,000 outstanding fighters by the same date and cost.

This is known as the quality vs quantity issue.

Talking about fighters specifically, I think the above is what happened with the P-51 vs the P-38 in Europe. The P-38 was more capable early on

That's not entirely accurate...

• In terms of top-speed, critical altitude, and service ceiling: The P-38 was better early on
• In terms of turn-rate: The P-38 didn't have a particularly remarkable rate of turn flaps-up; the P-40 and P-51 were considerably better (with the P-51 superior to the P-40 for the same percentage fuel load); starting with the P-38, the maneuvering flaps entered the equation, turn-rate was said to be equal or superior (the P-51 under at least some conditions was more responsive, but would dump speed faster) to the P-51.
  
• In terms of dive-speed: Starting with the P-38E, wing filleting was added would see a critical mach-number to Mach 0.65, with significant mach effects occurring around 0.67 indicated (0.68 actual) and a considerable reduction of maneuvering performance, with loss of control at 0.74 (it was possible to use various tactics such as doing relatively shallow spiral dives with the propellers flat-plated as the enemy aircraft dove; then power up and zoom climb after them as they came back up); the P-51B/C (unsure if the A was different) had a placard limit of 0.75, with a maximum dive speed of 0.84 giving it a major advantage (which was the highest in the USAAF). Eventually, with the P-38J: Dive-flaps would be fitted and increase the maximum mach (unsure how it compared to the P-51).
• Human factors: The P-38's cockpit was quite cold, the air conditioning system never quite worked right, and there was a tendency sometimes for the canopy to frost over. The fact that the plane had more switches and buttons simply owing to two engines made it even worse when you felt like you were going numb; the P-51's cockpit seemed to be warmer (not sure if it was the air-conditioning system or the simple fact that the engines put out some heat that radiated in).

The P-51's top-speed, critical altitude and service ceilings came with the Merlin 60 series: The V-1650-3 would be able to reach a critical altitude of 29,800 feet (and a top speed of 447 mph), and the V-1650-7 was (if I recall... if you're there wuzak, feel free to correct me) around 24,000 feet, with a superior rate of climb to the V-1650-3 at lower altitudes; the P-38's top-speed also increased with up-rated V-1710's.

Both the P-38 and P-51's range increased with the use of drop-tanks (the bomber-guys were really opposed to drop-tanks for escort aircraft), and increased fuel capacity (The P-38J used a new inter-cooler which freed up room in the outboard wings for extra fuel, though some of the first lacked it; the P-51B/C had radio equipment repositioned early on to free up 85-gallons of space for an extra fuel tank): While the P-38 combat radius was impressive almost from the outset (particularly when drop-tanks were involved), it only applied when flown at speeds that weren't tactically useful over the skies of Europe (typically around 300 would be a good starting point), and one had to use a continuous series of S-turns (or just 'essing') to stay with the slower bombers (240-255 mph) so you'd need to fly around 1.25 times further than you'd theoretically expect; it wasn't until the -J that it was able to achieve the range while flying fast enough and essing.

In both cases the extra fuel came with caveats: The P-51 had it worse because the center of gravity was right up on the neutral-limit with the 85-gallon tank filled. As a result, one would for short range/medium range flights use just the wing-tanks with a reduced (intercept) or full-load; full wing-tanks and drop-tanks for longer ranged flights; full wing-tanks, center-tank filled, and drop-tanks for the longest: To avoid pitch-ups, one would burn the center tank either down to at least 30-gallons, if not totally dry; then tap off the drop-tanks until they either ran dry or you encountered combat; then punch them off and proceed.

The P-38J had a slight center of gravity issue as well, but not as bad; still it was prudent to burn off a little bit of the wing-tank fuel before going to drop-tanks.

What I wrote in #112 had to do with generalities, how the system would basically function and that the process was possible. To standardize, modularize, etc, you need a deeper understanding.

Okay, I follow

As a general statement, sure.

That's largely what I was going for, though I read about the rest that you wrote about the need to avoid sweeping general statements when possible.

I don't think anyone ever used such a solution in a fielded SAM system

I was just making a guess due to the mention of optics being used. My knowledge of optical sighting systems is very limited (I have a telescope from when I was a child, and a few binoculars -- definitely not very sophisticated ).

 

[Zipper730]

There was a mock up of a Mosquito with a turret and one if not Beaufighters were built with turrets.
View attachment 470132

When did the RAF let De Havilland part with the turret?

It turns out they they did but that was unknown during the planning stages.

That's something I find surprising: The whole reason turbochargers were pursued with such vigor was because it allowed one to maintain full horsepower at higher altitude, and the result of this would be that you'd have more power relative to drag: One could hold the same indicated airspeed on the same power setting, and achieve a higher true airspeed in practice: The ability to hold a higher speed for a similar amount of time means greater range.

Most of the troubles were in the P-47B version which stayed stateside as trainers (and development aircraft) The P-47 was the first version to go overseas after more than 500 "B"s were built.

I did some checking, firstly only 171 P-47B's were built; secondly the P-47C's were first operational by March, 1943.

 

[fubar57]

I have 170 (or 171 depending on the website or book) -Bs and the -Cs going fully operational on 8 April 1943, and seeing its first combat on 15 April. (not wiki)

 

[Koopernic]

So, this attitude seemed more prevalent in the naval community than the RAF?
So either Dana Bell was wrong about the aircraft being designed to ultimately have a gun-laying radar, or that was an ultimate-wishlist item?
And they were around in 1943 or 1944?
Oh, I thought it was just because you know where the original path was and at least can extrapolate where it could go from where it first was spotted...
So it's just blasting out signal not blasting out signal then receiving what hasn't been absorbed or dispersed?
So the image looks like a jiggly bouncing glob?
When you say "a function of the display settings" do you mean like how I can make my monitor light up or dim a bit? Or do you mean the amount of power you're deciding to send out?
Walks off?
So you make it look like it's somewhere it's not really located?
So it's tracking empty space?
So you either mimic the return in such a way as to deceive the scanner or you just brighten it so much that it hides the plane in all the static?
So it produces errors in timing the location of the aircraft as it's getting different returns at different times?

"Walks off?"

The radars timers used to auto track the target in range will have filters to exclude Target position, speed and acceleration changes that are implausible. So the jammer creates a false return located at the same range and has to kind of slowly gently walk of in the sense of creating false pulses that slowely move away. Technically it's not really noise jamming, it's seduction

The radar can have other circuits such as dithering the pulse to stop it being regular and predictable, frequency changes phase change monitoring (Doppler) information.


In regards to exotic alloys they were required for the turbine, turbine housing and exhaust ducting to feed the turbine housing. The alloys while available in reasonable quantitatives still had to be rationed.

 

[wuzak]

When did the RAF let De Havilland part with the turret?

Bear in mind that the Mosquito was never intended to have a turret, and certainly could not have one in the bomber role.

The MAP were at de Havilland to put some sort of rear defence on the Bomber/PR version, but that went nowhere.

The turret fighter came up after the fighter conversion was proposed. Two of the three fighter prototypes were to be turret fighters, but in the end only W4053 flew as such.

Construction of W4053 started in May 1941 and finished in September. Its first flight was in September. It went to the RAF for trials flights in December 1941 where it was determined that the turret wasn't necessary.

Note that the turret fighter was not a night fighter. It had no radar equipment.

In early 1942 the turret was removed and faired over, W4053 being converted to serve as the prototype T.III dual control trainer.

The original prototype, W4050, was flown with a dummy turret to investigate the effects on the aircraft's aerodynamics. It was found that there was a significant loss of speed.

To answer the question, the RAF (actually the Ministry of Aircraft Production) allowed de Havilland to part with the turret as soon as it was flown in trials.

 

[Shortround6]

Yes the P-47B was only built to 170-171 aircraft. Sorry guys.

Northrop was actually a small company. Jack Northrop being on his 3rd company in about 10 years. He had a great reputation but the size of the company he had in 1940-41 was small. The Northrop company that had built the Alpha, Delta and Gamma aircraft and the predecessors to the Dauntless dive bomber and A-17 attack aircraft had by this time become the El Segundo division of Douglas Aircraft.

The new Northrop company had built one prototype/proof of concept flying wing and 24 single engine float planes for Norway when they started work on the P-61.

As far as this goes

" That's something I find surprising: The whole reason turbochargers were pursued with such vigor was because it allowed one to maintain full horsepower at higher altitude, and the result of this would be that you'd have more power relative to drag: One could hold the same indicated airspeed on the same power setting, and achieve a higher true airspeed in practice: The ability to hold a higher speed for a similar amount of time means greater range."

yes and no, the original specification/thoughts for the P-61 called for about an eight hour "Loiter time." not quite the same as long range. Early night fighting tactics and theory being a bit different than what was used later. In 1940-41 the operational heights thought to be needed may not have been in the 25,000-30,000ft range for night fighting, unlike day fighting.

Trying to stay airborne for anything close to eight hours with a pair of R-2800s is going to take a lot of fuel. Zipping around at high speed, even high cruising speeds is going to suck up a lot of fuel. Even max lean mixture could use 105 gallons on hour on an early P-47. or 210 gallons an hour on a "turbo" P-61. this requirement may have gone out the window later on.

Night fighters (at least the twins) were not scrambled at the approach of enemy aircraft. They mostly flew standing patrols at relatively low speeds, if you are already at 15-20,000ft and 200mph or so when ground radar tells you that something is coming you only need a few more minutes to get up to combat speeds and maybe climb a bit more.

Here is a chart for the P-61 powerplant;

Please note that while they shift the auxiliary supercharger from neutral at around 5000ft in WEP and around 7000ft in military power they are still using neutral at 14,000ft at max lean cruise. They could probably go several thousand feet higher in neutral at less than max lean cruise. The turbo offers no real advantage in such a situation. It does offer improved cruise at higher altitudes but there is a balance between improved boost and higher back pressure. Turbos are not quite the free horsepower some people claim. They do offer more power for the least cost to the engine in power needed to drive them but that is not FREE. One book claims that a turbo 1000hp engine looses 80hp at 20,000ft due to the increased back pressure of the exhaust system. Now 80hp is much less than the power required to drive the extra stage of a two stage mechanical supercharger but it is not "free". Under cruise conditions the power loss would be less.
P-61s may have used one of the best exhaust systems used on the R-2800. From what I can find (but could be wrong) it seems they used 9 exhaust pipes pairing one front and one rear cylinder. The pipes are short and pointed almost directly rearward giving the P-61 the most advantage from exhaust thrust. Or perhaps I should say the most exhaust thrust as best advantage also includes the best match between velocity of the exhaust gases and the velocity of the aircraft.
A turbo has little or no exhaust thrust.

The P-61C gained about 1 ton in weight. While not all of this can be attributed to the turbos I would guess that perhaps 1/2 was.
There were two P-61Ds which were converted P-61As using the "C" series engines with large turbos, they gained well over 1000lbs in empty weight. The "D" was canceled in favor of the "C".

 

[wuzak]

Unless you had some kind of mix of hunter-killer teams where the SCR-720 equipped aircraft were the hunters and the APG-2's were the killers..

I don't know how that would work.

And I'm not sure that the gun-laying machines would be any better at shooting down bombers than the "hunters". Because the 4 x 20mm cannons were, surely, the first choice weapon to use. And when they got in range they could use optical sights.

Maybe if they implemented the AWACS system or ground control it could work. But without that the search radar was the better option.

 

[Shortround6]

I think they tried the "Hunter-Killer" system with the Douglas Havoc Turbinlite.

Granted the accompanying gunships didn't have any radar of their own. But the co-ordination needed between separate aircraft given the radios-electronics of the time was a major handicap to the system.

anytime you violate the KISS principle you better have a damn good reason. All too often fancy complicated solutions failed in rather spectacular ways.

 

[Koopernic]

When did the RAF let De Havilland part with the turret?
That's something I find surprising: The whole reason turbochargers were pursued with such vigor was because it allowed one to maintain full horsepower at higher altitude, and the result of this would be that you'd have more power relative to drag: One could hold the same indicated airspeed on the same power setting, and achieve a higher true airspeed in practice: The ability to hold a higher speed for a similar amount of time means greater range.
I did some checking, firstly only 171 P-47B's were built; secondly the P-47C's were first operational by March, 1943.

Engines with two stage superchargers generated considerable jet thrust. The Merlin about 300lbs the Jumo 213E about 200kg. These late war engines should have been given ehp or equivalent horse power ratings as a modern turbo prop is given. Instead we focus only on the shp or shaft horse power.

On the basis of that 300lb thrust figure I had for the WW2 Merlin and the boost ratio of some Reno racers which would almost quadruple mass flow these aircraft would have over 1000lb jet thrust. They could probably fly without a propellor.

 

[Token]

Talking about fighters specifically, I think the above is what happened with the P-51 vs the P-38 in Europe. The P-38 was more capable early on, but the P-51 was less expensive and easier to make, and would be less expensive and easier to maintain. It made more sense to develop the P-51 into the long range escort fighter it would eventually become rather than to try to do the same thing with the P-38, even though there is no doubt the P-38 could have been made to get the ranges needed.

That's not entirely accurate...

You are reading too much into what I said, and then saying about the same thing I said. Look at what I said, "early on". Keep in mind I am working from memory here, so there might be slight errors in months, but should be pretty close.


In March of 1942, which, P-38 or P-51, was the more capable long range escort fighter? Not that long range escort missions were happening, but if you had to have one that day, what aircraft would you use?


In August, 1942, when the concept of unescorted bombers proved to be too costly, which of the two was the more capable long range escort fighter with the range needed to get the bombers to the target for most missions? The P-38 or the P-51? In August of 1942 the P-38 was already getting long range kills, the P-38F was in service, the P-38G was in production, and the XP-51B was just making its first flight. The operational P-51A's just were not as good at long range escort duties as the operational P-38's were.


In October 1943, what operational aircraft in usable numbers with the 8th AF was the most capable long range escort fighter? Ask the 55th FG, although I am sure the P-47 bubbas would argue. I think it was not until Dec 1943 that the 9th AF P-51's started regularly flying escort for 8th AF bombers, and not until Feb 1944 that the 8th AF P-51's got in the mix.


Yes, the P-51 was the smarter choice for improvement to support this tasking, as I said, but early on the P-38 already had very nearly the range needed to support all bomber missions and efforts were already under way to increase the P-38's range. The other issues you point out were eventually resolved just as the comparatively short legs of the early P-51 were also resolved. And that was my point, early on the P-38 was the better bird in the hand, but the P-51 was the smarter future.


It was the less wise decision, and so it did not happen (for several reasons, not the least of which was the need for P-38s in other theaters), but what if the decision had been made to stick with and improve the P-38 and make it the premier long range escort fighter? Is there any doubt that it would have excelled? None that I know of. However the aircraft took longer to build, cost roughly twice as much as the P-51, was nearly twice as complex, and had a much thicker logistics tail. And production of the Merlin engine could commence without reduction in the production of the Allisons, allowing the existing Allison designs to evolve and production of those aircraft to continue at higher rates.


The P-38 in the ETO often gets swept under the rug. But it did contribute, and in a good way. It was, after all, the first allied fighter escort over Berlin, even if by the slimmest of margins.


T!

 

[Zipper730]

Bear in mind that the Mosquito was never intended to have a turret, and certainly could not have one in the bomber role.

Actually, I thought the rear-turret idea had simply been replaced with a top-turret for the same purpose. I know a long-ranged fighter was proposed, but I figured it was just an excuse to keep funding flowing.

With the aircraft completed in May, completed and flown in September: It seems there was some serious bureaucratic inertia on the turret fighter

To answer the question, the RAF (actually the Ministry of Aircraft Production) allowed de Havilland to part with the turret as soon as it was flown in trials.

I understand that the point of the turret-fighter was so that the turret would permit ease of aiming against bombers that could potentially fly higher than them: Early turret fighters were day-designs and human vision is fine for that purpose; at night, one's visual acuity is much less and you can't aim until you're much closer (unless you have a radar system, but that still depends on the ability to in some way display the position of the plane or track it) unless the plane was sluggish and needed the turret to get the guns where they need to be.

Yes the P-47B was only built to 170-171 aircraft. Sorry guys.

No problem

Northrop was actually a small company. Jack Northrop being on his 3rd company in about 10 years. He had a great reputation but the size of the company he had in 1940-41 was small. The Northrop company that had built the Alpha, Delta and Gamma aircraft and the predecessors to the Dauntless dive bomber and A-17 attack aircraft had by this time become the El Segundo division of Douglas Aircraft.

Oh, I figured that El Sagundo pinched back off into Northrop again.

yes and no, the original specification/thoughts for the P-61 called for about an eight hour "Loiter time." not quite the same as long range.

I know the difference between endurance and range

Night fighters (at least the twins) were not scrambled at the approach of enemy aircraft. They mostly flew standing patrols at relatively low speeds

I understand how standing patrols work, since you're already up at altitude you don't have to waste time warming up and climbing all the way to the bombers height, just from your height to theirs and to combat speed: It does reduce the speed margin required for intercept.

Regardless: And the radar can spot targets at around 110-125 miles out right?

P-61s may have used one of the best exhaust systems used on the R-2800. From what I can find (but could be wrong) it seems they used 9 exhaust pipes pairing one front and one rear cylinder. The pipes are short and pointed almost directly rearward giving the P-61 the most advantage from exhaust thrust. Or perhaps I should say the most exhaust thrust as best advantage also includes the best match between velocity of the exhaust gases and the velocity of the aircraft.

I did not know it was that efficient -- all I knew was that it was a twin-supercharger...

A turbo has little or no exhaust thrust.

That's one thing I'm aware of

The P-61C gained about 1 ton in weight. While not all of this can be attributed to the turbos I would guess that perhaps 1/2 was. There were two P-61Ds which were converted P-61As using the "C" series engines with large turbos, they gained well over 1000lbs in empty weight.

Seems like a likely culprit!

I think they tried the "Hunter-Killer" system with the Douglas Havoc Turbinlite.
View attachment 470157

Well, it was sort of a hypothetical than a serious idea...

 

[wuzak]

Actually, I thought the rear-turret idea had simply been replaced with a top-turret for the same purpose.

The rear turret for the Mosquito was never a serious proposition. Other ideas had a fixed rear facing gun poking out the tail cone, but that also did not find traction.

This was largely because many at the RAF and MAP could not accept the idea of an unarmed bomber.

An upper turret was not contemplated as it would cut the size of the bomb bay in half, reducing the bomb load from 1000lb (original load) tp 250lb.

I know a long-ranged fighter was proposed, but I figured it was just an excuse to keep funding flowing.

In 1940 funding of military aircraft in Britain was not the issue it was in the US. Funding the aircraft that were required was, however. In 1940 that meant that many projects had to be cancelled or postponed in favour of Spitfire and Hurricanes. The Mosquito escaped cancellation a few times, partly because it used wooden construction and did not interfere much with production of the main fighters.

The initial contract was for 50 bombers (including the prototype). But the needs of the RAF dictated changes, so that it ended up a mix of bombers, photo-recon and fighters.

I don't believe fighter versions were considered much before the prototype first flew.

There were to be 3 prototype fighters and 22 production fighters and 4 production trainers.

With the aircraft completed in May, completed and flown in September: It seems there was some serious bureaucratic inertia on the turret fighter

W4050, the bomber prototype, flew on November 24 1940 (with the civilian registration E0).
W4052 was the fighter (F.II) prototype. It flew on 15 May 1941.

In April 1941 the Ministry for Aircraft Production (MAP) instructed de Havilland to complete two of the three fighter prototypes as turret fighters.

de Havilland commenced construction of W4053 in May 1941 and completed it in September 1941. On 14 September 1941 Geoffrey de Havilland Jnr flew W4053 from Salisbury Hall (where it was constructed) to Hatfield (site of de Havilland's factory).

Factory trials were undertaken before handing it over to RAE Farnborough on December 29. There it underwent operation trials and it was determined that the turret was unnecessary.

W4050 was fitted with a mock turret and test flown on 24 and 25 July 1941.

The turret Mosquito idea lasted less than a year.

I understand that the point of the turret-fighter was so that the turret would permit ease of aiming against bombers that could potentially fly higher than them: Early turret fighters were day-designs and human vision is fine for that purpose; at night, one's visual acuity is much less and you can't aim until you're much closer (unless you have a radar system, but that still depends on the ability to in some way display the position of the plane or track it) unless the plane was sluggish and needed the turret to get the guns where they need to be.

As I understand it, the turret concept was to hit the bombers with a broadside.

 

[Zipper730]

The rear turret for the Mosquito was never a serious proposition. Other ideas had a fixed rear facing gun poking out the tail cone, but that also did not find traction.

This was largely because many at the RAF and MAP could not accept the idea of an unarmed bomber.

Basically

An upper turret was not contemplated as it would cut the size of the bomb bay in half, reducing the bomb load from 1000lb (original load) tp 250lb.

Didn't know that...

W4050, the bomber prototype, flew on November 24 1940 (with the civilian registration E0).
W4052 was the fighter (F.II) prototype. It flew on 15 May 1941.

In April 1941 the Ministry for Aircraft Production (MAP) instructed de Havilland to complete two of the three fighter prototypes as turret fighters.

So why couldn't 1 of the P-61's be completed without turret? Or was this because these were day fighters?

As I understand it, the turret concept was to hit the bombers with a broadside.

So the idea was to go head on at them and cut 'em apart as you merged? Or was this a rear-chase?

 

[Koopernic]

There could be a number of solutions. The obvious one is to add a conical scan capable dipole to the P61 radar.
1 a FuG 244 "awacs" on the Ar 234P5 which also has a conventional nose radar.
2 A Hellcat with a AN/APQ 6 Radar. This radar was blind fire capable. Spiral as opposed to conical scan scan meant it was no good for aiming the P61 turret except directly ahead.
3 and 4 A B29B with AN/APQ 15. Not sure if this was range only but I expect it had a spiral or simple circular scan so could be used for blind fire..

 

[fubar57]

So why couldn't 1 of the P-61's be completed without turret? Or was this because these were day fighters?

From the 38th aircraft on, all P-61As were delivered without a turret. This continued into the early -61Bs. This was due to a serious tail buffeting problem and the need for turrets on the B-29 program. All the required equipment on the inside of the aircraft to operate the turret was still in place

 

[Token]

There could be a number of solutions. The obvious one is to add a conical scan capable dipole to the P61 radar.

If you do this you essentially have the APG-1/2, and the same limitations as the APG-1/2. A possible solution would be to add an APG-1/2 to an aircraft in addition to the SCR-720. In this way you have the situational awareness of the AI radar and the auto track gun laying of the AGL radar. A technique could even be developed to cue the AGL from the AI radar, speeding up the track initiation when switching targets. However, this solution cost you twice as much weight. And I am not sure if the filter technology of the day was up to 2 radars so close in frequency on one aircraft.

2 A Hellcat with a AN/APQ 6 Radar. This radar was blind fire capable. Spiral as opposed to conical scan scan meant it was no good for aiming the P61 turret except directly ahead.

I assume you mean the AN/APS-6? It was "blind fire" in the aspect it could tell you when your aircraft was pointed directly at a target when the radar was in its shortest range modes. In the longer range modes it could not tell you elevation, so you did not know if the target was above or below you, only that it was ahead of you at X range and Y azimuth/bearing.


The APS-6 achieves this two different modes of tracking by using two different types of scans, depending on range setting. At longer ranges it is spiral scan covering a cone of +/- 60 degrees, at shorter ranges, and the "blind fire" mode to tell when your guns / aircraft centerline is on target, they use a conical scan with about a 15 degree arc.

3 and 4 A B29B with AN/APQ 15. Not sure if this was range only but I expect it had a spiral or simple circular scan so could be used for blind fire.

I assume you mean AN/APG-15? The APQ-15 was a jammer designed to counter Freya. The APG-15 radar used a conical scan.


The center of the APG-15 con scan was aligned with the gun axis, the turret motion moved the tracking beam in space. In this case the dish was wobbled (spun offset from axis) and the feed is fixed. The dish was skewed roughly 4 degrees off center, creating a beam just under 8 degrees off center. So the conical scan width (to the 3 dB points) was probably on the order of 30 degrees (I have seen numbers of 25 to 30 degrees used for this system).


T!

 

[Zipper730]

There could be a number of solutions

The AWACS idea isn't so crazy: The US Navy did in fact modify a B-17 derivative with a HUGE antenna. I figure if you have that, you have the hunter element; with the P-61's with the APG-2 as the killer side...

I assume you mean the AN/APS-6?

When did the AN/APS-6 come out?

It was "blind fire" in the aspect it could tell you when your aircraft was pointed directly at a target when the radar was in its shortest range modes.

How short? Because if that range is around 400 yards, that puts you within an effective gun-range firing solution...

The APS-6 achieves this two different modes of tracking by using two different types of scans, depending on range setting. At longer ranges it is spiral scan covering a cone of +/- 60 degrees, at shorter ranges, and the "blind fire" mode to tell when your guns / aircraft centerline is on target, they use a conical scan with about a 15 degree arc.

The tighter the arc, the more gain right?

 

[wuzak]

I assume you mean the AN/APS-6? It was "blind fire" in the aspect it could tell you when your aircraft was pointed directly at a target when the radar was in its shortest range modes. In the longer range modes it could not tell you elevation, so you did not know if the target was above or below you, only that it was ahead of you at X range and Y azimuth/bearing.


The APS-6 achieves this two different modes of tracking by using two different types of scans, depending on range setting. At longer ranges it is spiral scan covering a cone of +/- 60 degrees, at shorter ranges, and the "blind fire" mode to tell when your guns / aircraft centerline is on target, they use a conical scan with about a 15 degree arc.

So doesn't provide gun trajectory information?