P-61 Gun-Laying Radar

[XBe02Drvr]

That's why I shot trap: one of them BBs hit the bird 91% of the time

Ayup, and if that WWII Z-730 night fighter had a couple of Vulcans mounted in shock absorbing wobble mounts, it might even score a few hits, even with the primitive radar it had. That's assuming it was real close to its target. I don't think I'd want be that close behind a target I can't see, especially if I'm about to start causing it to shed pieces of airplane.
Cheers,
Wes

 

[Zipper730]

You're right, the radar can give you the range, azimuth, and elevation of your target, but not precisely enough to land your rounds on target with the technology of the time.

With day fighting you would generally fire and then walk the rounds onto the target. At night that would probably not work unless you had tracers that were fairly dim.

You clearly haven't done much shooting in the real world.

I've never fired a gun at all.

 

[XBe02Drvr]

I've never fired a gun at all.

Well, it's about time you learned. I bet your local Police Department or Sheriff offers a firearms safety course, or can refer you to one. In today's gun-saturated world, everyone should know and understand about guns and how to handle them safely, even if they're not interested in shooting for sport. Like it or not, a gun is apt to touch your life someday in some way you'd never expect. You're safer if you have some idea what they're about and know how to deal with them wisely. Just a thought.
Cheers,
Wes

 

[Token]

With day fighting you would generally fire and then walk the rounds onto the target. At night that would probably not work unless you had tracers that were fairly dim.

Not for the "better" pilots. Your intent is to be as accurate as possible with the first burst, and then correct IF necessary. Short, controlled burst, maximizing the number of engagements and damage.


One of the things that separated the good pilots, and the aces, from the average was gunnery. Being able to accurately aim a deflection shot and to kill / injure / disable the target in the first burst was important.


Some pilots flew with fewer, or even no, tracers. Tracers work both ways, it can help you correct, but it also tells the enemy he is being fired on.


You would not want a gun layer in a fighter with fixed guns. It has no advantage, and several disadvantages, over an AI radar in such an application.


A tracking radar can indeed give you AZ, EL, and Range to the target, but so can an AI radar. But the tracking radar (at least until the advent of TWS, Track While Scan) can only track one target at a time. The APG-1/2 could only track one target at a time, meaning you lost all SA to other aircraft, targets or friendlies, that might be in the area.


A scanning radar like the SCR-720 scanned a chunk of sky. How large a chunk depended on the settings selected. It showed the pilot the relative position, in AZ and EL, of everything in that chunk of sky. The pilot (in the case of the P-61) did not have range, but the gunner / RO did have range, as well as AZ/EL.


The pilots C-scope for the SCR-720 looked something like this:

The above picture only shows a single target, but it would display all targets in the selected field of view. The center is on the nose, vertical relative position to the horizontal line is above/below the nose, horizontal relative position to the vertical line is left/right of the nose.


Put the desired target in the center of the display, by pointing the nose of the aircraft, and you are headed right for it, it is on the nose. But you can still see the other targets that might be ahead of you.

T!

 

[Zipper730]

Not for the "better" pilots.

True

You would not want a gun layer in a fighter with fixed guns. It has no advantage, and several disadvantages, over an AI radar in such an application.

Well, at night it would allow you to track the position of the plane continuously and compute lead to plunk rounds on target from a greater distance. The issue is that you'd lose situational awareness to other aircraft.

A tracking radar can indeed give you AZ, EL, and Range to the target, but so can an AI radar. But the tracking radar (at least until the advent of TWS, Track While Scan) can only track one target at a time. The APG-1/2 could only track one target at a time, meaning you lost all SA to other aircraft, targets or friendlies, that might be in the area.

That does raise a few questions

1. Why did the USN use the APG-1 on night-fighters then?
2. While it might not have been called a TWS, the radar used on the F3D did have such a capability: Why did later aircraft seem to lose this capability until the F6D and F-14?

The pilots C-scope for the SCR-720 looked something like this:

View attachment 504094

For some reason I thought you had one scope for elevation, one for azimuth...

 

[XBe02Drvr]

While it might not have been called a TWS, the radar used on the F3D did have such a capability: Why did later aircraft seem to lose this capability until the F6D and F-14?

That time period almost exactly coincides with the era of the gunless missile-only fighter. Do you suppose there's a reason?
Cheers,
Wes

 

[wuzak]

For some reason I thought you had one scope for elevation, one for azimuth...

Earlier systems did.

AI Mk. IV radar - Wikipedia

[The Mk. IV display system consisted of two 3-inch (7.6 cm) diameter cathode ray tubes connected to a common timebase generator normally set to cross the display in the time it would take to receive a signal from 20,000 feet (6.1 km). The displays were installed beside each other at the radar operator's station at the rear of the Beaufighter. The tube on the left showed the vertical situation (altitude) and the one on the right showed the horizontal situation (azimuth)./QUOTE]

 

[Zipper730]

That time period almost exactly coincides with the era of the gunless missile-only fighter. Do you suppose there's a reason?

The United States first started looking into guided missiles either right at the end of WWII or post WWII. This applied to both the USAAF/USAF and the USN. The bulk were generally designed to destroy bombers in both cases (Ironically the AIM-4 was designed as a bomber-defense weapon, but they decided they'd use it against bombers instead), and it seems many radar developments were built around tracking targets at long-range and guiding missiles into them, then gunnery.

That said, some of the early night-fighters did use varying types of gun-laying radar and, while I cannot speak for the early F-89's and F-94's, the F3D was based around tracking and engaging aircraft simultaneously. The F-89 ended up ditching the guns for one of the following reasons

1. The misguided idea that the rockets would be good enough
2. The larger radar and it's electronic boxes displaced the ammo for the guns
3. A desire to increase range and endurance lead to a desire to trim off things they didn't think mattered (that sort of includes #1).
4. A mix of 1-3

The USN seemed slower to ditch the guns because their night-fighter designs more successful and their interceptor needs were somewhat different than the USAF's, while both needed aircraft that could be started, get airborne rapidly, climb and accelerate to high-speed and altitude

• The USN could essentially be facing anything from nuclear-equipped bombers, to reconnaissance and fighter aircraft: Early on this would have encouraged the need for guns instead of just rockets.
• The USAF would be unlikely to face off against fighters (except possibly Alaska, and I'm not totally sure about that), which would limit the incentive to put guns on their aircraft.
• The USN would find it fairly easy to determine what the target would be -- the Carrier itself. While the USN could execute dog-leg maneuvers that could greatly complicate the intercept, the target is clearly known.
• The USAF would find it more difficult to ascertain exact targets as there could be military bases, power-plants, targets of value within cities, and the cities themselves: Dog-leg maneuvers would not just complicate the geometry of intercepts: They would also be able to obscure the intended target too. This would favor an aircraft with greater performance and greater range.
• The USAF was known to have an "all-or-nothing" mentality

 

[Token]

Well, at night it would allow you to track the position of the plane continuously and compute lead to plunk rounds on target from a greater distance. The issue is that you'd lose situational awareness to other aircraft.

Lets not lose track of the timeline here. When I said "You would not want a gun layer in a fighter with fixed guns. It has no advantage, and several disadvantages, over an AI radar in such an application." I was talking about what was available at the time of the SCR-720 or the APG-1 and that could be put in a fighter size aircraft.


The APG-1/2, as far as I can tell, had no computation ability. Later system, late in the war, did have such ability.


The SCR-584 could be tied to a gun computer to direct AA, but the mechanical computer it used was the better part of a 30 foot trailer.

That does raise a few questions

- Why did the USN use the APG-1 on night-fighters then?

- While it might not have been called a TWS, the radar used on the F3D did have such a capability: Why did later aircraft seem to lose this capability until the F6D and F-14?

I was not aware the USN ever used the APG-1 in night fighters?

The USN did use things like the AN/APS-4 and -6, but these were not AGL or GL radars, they were AI and search radars, similar in function to the SCR-720.

The F3D achieved what it did with the radar by using 3 separate and distinct radars. One for search, one for track, and one for tail warning. Each radar had its own designation. The combination of radars had one designation, the APQ-35 or 36, in addition to the individual radar designations.

Not sure what you mean by later aircraft losing the capability. Many aircraft between the F3D and the F-14, assuming their roles called for it, had similar capability.

For some reason I thought you had one scope for elevation, one for azimuth...

Note that I specifically said "The pilots C-scope for the SCR-720 looked something like this". The pilot had a C-scope that functioned as the picture I posted. In the P-61 it was square instead of round, but the function was the same. The nice thing about such a scope is it integrates Azimuth and Elevation into one simple scope. Up and down is elevation, and right and left are Azimuth.

But the radar operator in the back had a different display, with more detailed information, including range. So there were two sets of displays in the P-61, the BC-1151 for the operator and the BC-1152 for the pilot.

Some radars did have separate displays for elevation and azimuth.

T!

 

[XBe02Drvr]

The USN could essentially be facing anything from nuclear-equipped bombers, to reconnaissance and fighter aircraft: Early on this would have encouraged the need for guns instead of just rockets.

In the mid to late 50s USN was very concerned by the Soviets doctrine of compensating for their lack of carriers by equipping fast long range bombers with standoff missiles to take out carrier task forces. The F4D Skyray was essentially a point defense interceptor and the F3H Demon had neither the speed nor the reach that this new development required.
Enter the F4H Phantom, designed above all else to go far, get there quick, and detect and destroy inbound intruders as far from the ship as possible. In-close dogfights were not part of this picture, as the attackers would be far outside the range of any possible escort fighters. Hence no gun. Navy F4s had a prodigious powerful radar with a detection and tracking range unheard of for an AI set at the time, designed to function without surface or airborne intercept control or support.
It wasn't until Vietnam forced a number of different aircraft to function outside their original design missions that the need for those extra features and the miniaturization to make them feasible was recognized and incorporated in the F-teens generation fighters.
Cheers,
Wes

 

[Zipper730]

Lets not lose track of the timeline here. When I said "You would not want a gun layer in a fighter with fixed guns. It has no advantage, and several disadvantages, over an AI radar in such an application." I was talking about what was available at the time of the SCR-720 or the APG-1 and that could be put in a fighter size aircraft.

Okay, though I should point out the P-61 was more a bomber-sized aircraft than a fighter-sized one (it just maneuvered very well for its size), the F4U and F6F's carried their radars in either a pod in the wings or underneath the fuselage in a modified bomb-pod or drop-tank (forgot which).

The APG-1/2, as far as I can tell, had no computation ability. Later system, late in the war, did have such ability.

From what I remember the P-61's entered service in 1944, and so did the USN's night-fighters. I don't know when the P-61B's were tested with the gun-laying radar, but the impression I always got was that it was at some point during the P-61's test program or around the time the P-61B's were entering service.

I was not aware the USN ever used the APG-1 in night-fighters?

The F6F-N variants used the APG-1 far as I know...

Not sure what you mean by later aircraft losing the capability. Many aircraft between the F3D and the F-14, assuming their roles called for it, had similar capability.

It seemed the F2H-2N (had just guns), F4D (guns/rockets/missiles), and F3H (guns/missiles) all had radars that provided gun-laying capability, but it seems none had the ability to do both functions.

 

[Zipper730]

In the mid to late 50s USN was very concerned by the Soviets doctrine of compensating for their lack of carriers by equipping fast long range bombers with standoff missiles to take out carrier task forces. The F4D Skyray was essentially a point defense interceptor and the F3H Demon had neither the speed nor the reach that this new development required.

The F4D and F3H took a considerable amount of time to enter service due to the J40 engine. While I'm not sure how the SFC of the J57 compared to the J40, there were complaints about the range of the F4D. I'm not sure if this had to do with a change in the desired intercept radius, whether the engine bay modifications ate into some fuel-space, and/or the J40's SFC (or listed SFC) figures were quite low. The aircraft was fitted with a pair of streamlined supersonic drop-tanks.

The F3H as originally designed was pretty impressive, but as time went on, the changes to make it into an all weather plane did exact some penalty in performance and, in order to increase it's payload and range further, it managed to accrue a respectable amount of weight. To compensate for the weight change, the wing-area was considerably enlarged to make up for it. I'm not sure how much performance was lost in the process -- some said it was a subsonic plane (one that was supposed to do at least 1000 mph), others say it was supersonic but performed lower than desired.

While intercepting Soviet bombers were important, the fundamental fact was that the USN's doctrine revolved around power-projection and this meant that they could be called upon to deliver attacks almost anywhere in the world. The carriers mobility allows it's aircraft to be greatly more effective for their size, but it also means that you're closer to the enemy too, and you are not just within range of the longest range bombers with/without cruise-missiles, but shorter ranged aircraft including fighters. It makes the bombing-run more effective, and you have to tangle with them too. So it was perceived as important to retain an air-to-air capability.

Enter the F4H Phantom, designed above all else to go far, get there quick, and detect and destroy inbound intruders as far from the ship as possible. In-close dogfights were not part of this picture, as the attackers would be far outside the range of any possible escort fighters. Hence no gun.

The F4H and XF8U-3 were both designed with aerial combat in mind to some extent. Interception was the primary role, but it was expected to engage in aerial combat.

That said, they greatly overestimated the capabilities of their missiles and operated under the premise that they would be able to engage outside of visual range most of the time. Unfortunately, they couldn't read the enemy IFF. I'm not sure if this had to do with newer Soviet IFF, or a difference in IFF used by export countries. Regardless, without the ability to properly assess aircraft, you could blow your own people up by accident. So the fights were dragged into visual range instead.

Navy F4s had a prodigious powerful radar with a detection and tracking range unheard of for an AI set at the time, designed to function without surface or airborne intercept control or support.

I'm not sure if I'd say unheard of, but it was pretty impressive. The F-106A had similar absolute range, but I could be wrong (the F-106A underwent numerous modifications), but the F-4B had better engagement ranges.

It wasn't until Vietnam forced a number of different aircraft to function outside their original design missions that the need for those extra features and the miniaturization to make them feasible was recognized and incorporated in the F-teens generation fighters.

I'm not totally sure about that: The XF8U-3 could carry a blister underneath the rear fuselage that would have made a gun-pack possible. I'm also not entirely sure why we couldn't build something that could read the enemy's IFF.

It was possible to do it as early as WWII...

With a 20,000 word limit... I leave you off here and start below.

 

[Zipper730]

The USN & USAF had differences in the roles of air-to-air and air-to-ground planes too

1. USAF
   • WWII to 1950
     1. Fighter
        • Point-Defense Interceptor: Covered rapid climb-performance and high-speeds, along with altitude to allow the rapid destruction of enemy bombers. Examples would include the XF-91 Thunderceptor. Would eventually be folded into the All-Weather Interceptor Category.
        • Day-Fighter/Fighter-Bomber: Covered fighters that were capable of performing offensive or defensive/offensive operations. They generally were also fighter-bombers in that they had a secondary air-to-ground role. Examples would include the F-47, F-51, F-80, F-84, F-86. Since some of them had exceptional range, they would also be used as bomber-escorts.
        • Bomber-Escort/Penetration Fighter: Basically, they were fighters designed with ranges that regular fighters couldn't always achieve. The F-47, F-51 proved quite able to do these job in WWII, but some bombers made even those aircraft less than ideal and, as jets came around, they were outperformed in speed. The range of jets proved to be a problem, particularly when combined with demands for speed, rate of climb. Escorts were designed to cover the bombers while flying a few thousand feet above them, whereas penetration fighters were designed to surge ahead of the bombers as to draw up enemy air defenses and shoot-them out of the sky. They usually had a secondary air-to-ground role like the standard day-fighter requirement. Examples would include the XP-81, F-82, XP-83, and XF-88 Voodoo. These designs were either cancelled or repurposed into other roles.
        • Night Fighters: Were radar-equipped and designed to be used defensively for standing-patrols against enemy bombers, and offensively for night-intrusion operations against enemy fighters and bombers; often included air-to-ground ordinance for attacks on enemy air-fields, making them all-weather fighter-bombers. Examples would include the Beaufighter, Mosquito, P-61, F-82, and F-89. They were later repurposed for the all-weather interceptor mission because of the nuclear bomber threat (the fact that jets performed better in terms of high-speed climb over propeller driven aircraft helped).
        • All-Weather Interceptor: Included the point-defense interceptor mission, the standing-patrol mission (typical night-fighter), and transitioned from aircraft that were originally designed around guns/cannon, to aircraft that were designed to carry cannon or rockets, or just rockets. Examples would include the F-86D, F-89, XF-91, and F-94.
     2. Attack
        • Dive-Bomber: Often single-engined aircraft that were designed to release bombs in a dive-angle of 60-90 degrees. There generally was a desire for more firepower than either the USN or other nations demanded in their aircraft. There was also a preference for internal weapons bays, at first for carrying a whole bunch of 20 pound blast-fragmentation bombs (which would produce too much drag to carry externally), and later out of habit, and the fact that bigger engines allowed for faster and larger designs that could carry heavier payloads without issue. Such aircraft ranged from having a rear-gunner for defensive firepower to none at all. The interest in these designs largely disappeared as the P-47 proved capable for this mission, and the A-26 performed well at low altitude, had two engines (they really were fixated on that), and a variant or two were being developed with improved cowlings, and a jet-engine mounted in the aircraft to higher speed over the target area. It was decided when the USAF became an independent service to delete the entire attack category, with single-engined designs either cancelled or re-designated as fighters (as bizarre as this sounds, the A-24 was redesignated as F-24). Examples of these aircraft would include the A-24, A-25, A-31/35 (used operationally by the RAF, but US built), XA-32, XA-33 (used by the Norwegians, but US built), A-36, XA-39, XA-40 and XA-41.
        • Light-Bomber/Strafer: These were multi-engined aircraft that were designed to carry relatively light payloads over short-distance (by bomber distances), often at low/moderate altitudes (the exception was the unlettered A-20, which was fitted with a turbocharger -- it didn't work out). They had arrangements that included a bombardier nose (which either had forward firing armament or not) or a gunship nose (which had no bombardier and a whole lot of firepower) as a general rule. These aircraft were generally fitted with a degree of defensive armament, which ranged from a dive-bomber style gunner arrangement, to powered turrets. Examples would include the A-20, and A-26.
        • Gunship: Similar to above except they lacked bomb-carrying capacity as far as I know. The only design I can readily think of that has this criteria is the XA-38 Grizzly, which was cancelled.
     3. Bomber
        • Light-Bomber: This category seemed to blend so well into the attack category that the attack category kind of became largely superfluous designation. They were basically built for low/medium altitude bombing that were often tactical in scope. They usually had at least one rear/upper gunner. Since the desire for attack planes to be multi-engined, aircraft in this category with single engines were generally retired (the A-24 ironically was classified as a fighter), or were re-classified as bombers.
        • Medium-Bomber: They were designed to be level-bombers able to carry a medium payload a medium distance. Since most of these designs were built to operate at low/medium altitudes, they seemed to basically be huge light-bombers with better defensive armament. Examples included the B-25 and B-26. Many aircraft in this category seemed to have been retired or reclassified as light-bombers as larger aircraft appeared.
        • Heavy-Bomber: This category included aircraft that were designed to fly large distances and capable of carrying heavy bomb-loads. This formed our strategic-bomber force. These aircraft were generally designed around heavy defensive-armaments. Examples would include the B-17 and B-24. As time went on the Heavies would eventually be retired, reclassified as medium or even light-bombers.
        • Very Heavy Bomber: This included bomber designs like the B-29, B-32, and B-36 that were so huge that evidently, "Heavy" didn't really do it justice. They were designed for exceptional range with exceptional payloads. They were very well defended (the B-29 had two top turrets, two bottom turrets, and a tail-gunner). As time went on these aircraft would be reclassified anywhere from Heavy to Medium, far as I know.
   • 1950 to 1961
     1. Fighter
        • All-Weather Interceptor: These aircraft ranged from the earlier rocket-equipped point-defense aircraft, to highly sophisticated designs that used missiles and nuclear-tipped rockets as their primary armament. They often possessed a very good rate of climb and acceleration, with a high top-speed. The earlier designs only possessed short-range, but the later designs included the ability to perform both point & area-defense. Since the requirement for taking out bombers was the overarching concern, they rarely carried any guns, and were not equipped to carry bombs. Examples would include the F-102 and F-106.
        • Fighter-Bomber: These were aircraft that were designed to, in theory, be effective air-superiority fighters as well as be able to be tactical-bombers. Some designs worked out quite well (F-86), others not so much. This either owed to the design not measuring up, or due to the misguided belief that air-superiority would not be needed (F-105). Designs that were configured to deliver nuclear weapons via a low altitude attack were usually called nuclear-strike.
        • Bomber-Escort/Escort-Fighter: For a brief period of time, due to the experiences of the Korean War, there was a brief revival in the idea of escorting bombers at high altitudes with fighters. With more powerful engines it seemed reasonable to expect long-range while possessing great performance, particularly with drop-tanks and in-flight refueling. The development of supersonic bombers probably made this a short-lived endeavor, and the design produced (the F-101) didn't really prove an effective design at high altitude. This aircraft ended up being folded into the all-weather fighter interceptor (as the F-101B), and nuclear strike aircraft (F-101A/C).
        • Lightweight Fighter: Basically, the Korean War inspired the idea of producing a simple fighter that could climb-like a rocket and out fly any aircraft. At first the USAF seemed generally interested. Unfortunately, the USAF decided that they wanted a day interceptor out of this (which is odd), and continuous Mach 2.0 performance. It set the shape of the aircraft from that point on. The aircraft produced was the F-104. It proved a better fighter than one would expect, though it's low speed maneuverability left a lot to be desired. It was used as a point-defense interceptor, and a nuclear-strike aircraft.
     2. Bomber
        • Light: The definition of light-bomber had resulted in an aircraft that had to have two-engines (whether it was needed or not), and the similar conceptual framework for payload and range (light payload carried over a short range). The problem was that the definition of short-range was such that, it probably precluded any aircraft that were really well suited for some of the tactical-bombing missions (particularly close air support, and even some of the interdiction roles), though the USAF seemed to have little interest in CAS. It seems that, for most purposes, aircraft designs like the A-4, A-6, or A-7 couldn't have been seen in the USAF at that time because of the fact that, two of the three designs have only one engine, and I'm not even sure if the A-6 had the range. Since the combat realities demanded such an aircraft, the role was folded into the fighter-bomber designation. The results were that we'd see airplanes like the F-105 (a fine attack plane, but not a very good fighter -- though it did better than I'd have thought).
        • Medium: The definition of medium-bomber seems to basically be anything that's too small to be a heavy and too heavy to be a light: It produces interesting results with the smallest possible category being around 12000 pounds (AJ & A3D, while US Navy aircraft, fit the objective designation as medium) and the highest being 32000 pounds (XB-49). The range requirements seemed to be acceptable admittedly.
        • Heavy: The heavy bomber basically included the aircraft with intercontinental range and the heaviest payloads. Using the B-36 as a starting point you'd be carrying 10,000 pounds of bombs a distance of something like 4950 nm, with heavier loads for shorter distances (the B-36's maximum load was around 72000 pounds off the bat, and later increased to around 86000 pounds). Interestingly, range and payload seemed to go down with the B-52 (range of around 8800 nm, maximum payload of around 43000 pounds in internal load).
2. USN/USMC
   • WWII to 1950
     1. Fighter
        • Day Fighter: Covered fighters that were capable of offensive and defensive air-to-air operations. They generally had some air-to-ground capability though it would steadily grow until these designs were effective fighter-bomber aircraft. Examples would include the F4F/FM, F4U, and F6F
        • Interceptor: Covered fighters that included a defensive role. This often involved a good rate of climb, acceleration, and altitude so as to allow them to destroy both fighters and bombers. Superior firepower was also sought (including the idea of dropping small 5.2 pound bombs on enemy bomber formations), and the desire for range remained. It seemed that what they were looking for was basically their own counterpart to the P-38 lightning. This continued after the war to an extent until the need for supersonic performance demanded changes. Examples would include the XF5F, F4U, FD/FH, and F2H
        • Night-Fighter: A fighter that was equipped with specialized navigation equipment and radar. Generally these were modified day-fighters (F4U, F6F and F7F), though the USMC had toyed with buying the P-61 (F2L).
        • Escort-Fighter: Though not pursued with the vigor of the USAAF, the USN did pursue aircraft with long-range to allow for bomber escort. Two examples would include the XF8B-1 and derivatives of the P-51.
     2. Bomber
        • Scout/Dive: These were basically dive-bombers that also had scouting capability built into their design. Since their goal was to sink ships, they generally were built around carrying one large bomb (1000 pounds) over a whole bunch of smaller bombs (that said, some had the ability to carry several bombs). Like most nations, they had a pair of forward-firing guns and a defensive gunner. As time went on, the idea of internal weapons bays, powered turrets, and nose-gears entered the picture. Examples would include the SBD, SB2C.
        • Torpedo/Level: These were level-bombers that could carry torpedoes as well. The need to lay a torpedo into the water at low speed usually meant they handled well at low speed (as is the need to land on a carrier-deck). The effectiveness of level-bombing on ships was fairly poor unless you were very lucky, or caught them all in the harbor and, US torpedoes had serious reliability issues until 1944. Torpedo-bombers often found themselves used outside their intended roles such as ASW, an airborne command-ship, AEW, and COD. That said, their level-bombing capability was not useless, and they were used effectively against land-based installations and cities at the end of the war. Inertia kept the development of these designs going until around 1945, with aircraft such as the TB2D (essentially a single-engined B-17) and TB2F (a twin-engined design with a maximum weight of around 43000 pounds ) making their first flights.
        • Bomber/Torpedo: It was basically a dive-bomber that could carry torpedoes. There were proposals for newer generation dive-bombers with internal-weapons bays, remotely controlled powered-turrets, and tricycle gears that actually flew (XSB2D). Since dive-bombers might very well have enjoyed better survivability than torpedo-bombers and, with level-bombing being largely unnecessary for anti-ship operations, the decision was made to combine the two roles together. In the name of maximizing performance, they decided to remove the turrets in order to increase speed and range (the SB2D became the BTD), and ionically, they removed the internal weapons bay (though it made the plane a little bit slower on the way in, it made for more speed on the way out, and allowed for greater range). The ultimate product of this was the XBT2D.
        • Torpedo/Scout: It was designed as a torpedo bomber with superior speed, and a scouting capability. The only one example was the XTSF-1, and it was designed to overcome the shortcomings the XTB2F had (namely it was too big, and might very well have been a little slower than desired). The fact is that this design was based on the F7F and, while both boasted excellent performance, it was a very large aircraft. It would probably have only been useful off the biggest carriers then in service (Midway-Class). This design like the torpedo-bombers would be abandoned in favor of the bomber-torpedo design, which by 1946 would be redesignated as attack.
     3. Attack: Basically, starting in 1946, the scout-bomber, torpedo/level-bomber, and bomber-torpedo categories were all merged into the attack category. These designs fit into several categories
        • Dive-Bomber/Torpedo: As before they were aircraft that were essentially dive-bombers with the ability to carry torpedoes. Their superior speed also made them similar to the older USAAF's attack category.
        • Early ASW Aircraft: These were aircraft that were basically torpedo-bombers fitted with specialized equipment. Usually one aircraft operated as the hunter, the other as the killer.
        • Level-Bombers: They were largely intended for carrier-based nuclear-bombing. While they could carry conventional ordinance as well as be used in tactical roles, they were designed predominantly to keep the USAAF from establishing itself as a nuclear monopoly. Though a flying-boat would permit more latitude for size: A combination of the USN's strike force being based around the carrier, and the fact that there's nothing that explicitly forbids a land-based aviation arm from operating seaplanes (or seaplane tenders), lead them to base it aboard the carrier. For the same reason that the USAAF roundly disliked carriers, the USN benefited from having a nuclear carrier-based bomber: They are aviation assets that cannot be controlled by anybody except the USN. Examples would include the AJ.
   • 1950 to 1961
     1. Fighter:
        • Day Interceptor: These included aircraft designed with a rapid rate of climb and high-altitude to allow them to effectively fight-off bomber aircraft. This category would become increasingly phased out in favor of all-weather capability. Some of the aircraft involved here had limited air-to-ground capability, and others were capable of other roles as well. Examples would include the F8F (off CVE's), FH, F2H, and FJ-4F.
        • Night Fighter: These were fighter aircraft designed with specialized navigation equipment and radar to allow them to hunt-down enemy aircraft at night. Some were dedicated for this role from the outset, and others were modified to perform this mission. Examples of a dedicated night-fighter would be the F3D (though it first flew in 1948), and F3H. Examples of modified aircraft to fulfill the mission would be the F4U, F6F, F7F, F2H-2N, and F7U-3N.
        • All-Weather Interceptor: These were similar to night-fighters, but they were often built around quick-response, rapid climb, and high altitudes. They also didn't necessarily have the same range. An example would include the F4D, F8U-1E/2/2N, F4H-1.
        • General Purpose Aircraft: This would be a category of aircraft that would include the ability to be used for both defensive and offensive roles, enough range to provide escort over a strike-group, and if need be, take part in the strike. The night-fighter would sort of become merged with this role. Aircraft that would fit into this category include the FJ-1, F9F, FJ-2/3, F2H-2B, FJ-4B, F11F, F3H-2N, F4H-1
     2. Attack: These included all the carrier-based bombers from tactical bombers all the way up to strategic bombers. Examples included the AD, AJ, A3D, A4D, A3J
     3. Anti-Submarine Warfare: Designed for the dedicated mission of tracking and sinking submarines. Examples would include the S2F Tracker

 

[Token]

Okay, though I should point out the P-61 was more a bomber-sized aircraft than a fighter-sized one (it just maneuvered very well for its size), the F4U and F6F's carried their radars in either a pod in the wings or underneath the fuselage in a modified bomb-pod or drop-tank (forgot which).

I think in both cases it was generally a pod on the starboard wing.

From what I remember the P-61's entered service in 1944, and so did the USN's night-fighters. I don't know when the P-61B's were tested with the gun-laying radar, but the impression I always got was that it was at some point during the P-61's test program or around the time the P-61B's were entering service.

The P-61 may have entered service in mid 1944 (I don't know the date of entry to service), but it is a pre-war program. And the 6 P-61B-25-NO aircraft that were fitted with the APG-1/2 were, I believe, ordered in 1942.

In the case of the P-61, the APG-1/2, and a computer, the APG-1/2 was, apparently (data is very scarce on the details, but several sources reference the radar feeding a computer) connected to an external analog computer for lead prediction. The computer itself was not part of the APG-1/2 (this was similar to the ground SCR-584 radar / computer setup). It was possible in the P-61 for a couple of reasons. The P-61 had room for such a computer, unlike most other fighters. And the P-61 had a turret, not fixed guns. So the computer just had to predict lead and bias the turret, just like ground AA systems did. And I have never heard or read any results of how well this system performed. For all I know this is the thing that killed the APG-1/2 in the P-61, and kept the SCR-720 in them until the end. Indeed, the B-25-NO aircraft were, as far as I can tell, stripped of the APG-1/2 and generally retrofitted with the SCR-720.

Doing that in a fighter with fixed guns is a different story. You either need to develop a sight that works with the computer and radar to predict lead, or you have to tie it to an auto pilot to direct the guns. Both of those are separate developments than the lead predicting turret / AA gun type things that were being developed for both ground based AA and bomber turrets.

I think you are missing a key point here, gun laying radars are generally part of a turret / moving gun system. You "lay" a gun by elevating and rotating the azimuth axis to cause the projectiles to fall where you want them. If they are fixed guns you are not "laying the gun". Fire Control Radars are used for other types of systems, such as fighters with fixed guns. Other than the APG-1/2, a system that, as near as I can tell, was never operationally fielded and produced in VERY limited numbers, I don't think any US fighters ever really got GL or AGL radars. And after the war they received FCRs, which is what such radars are still called today, be they used for firing guns or missiles.

The F6F-N variants used the APG-1 far as I know...

Got a reference of that? While it is certainly possible one or two were tested with the APG-1/2, not that I remember though, the F6F-N aircraft I have heard/read/researched about generally had either the APS-4 or the APS-6. Very late in the war and after the war some of these were outfitted with the APS-19 or other advanced (for the day) radars.

It seemed the F2H-2N (had just guns), F4D (guns/rockets/missiles), and F3H (guns/missiles) all had radars that provided gun-laying capability, but it seems none had the ability to do both functions.

Unless I have lost track of what is being said, are you saying these aircraft had gun laying radars (lets call them by their correct term, Fire Control Radars, FCR) but no ability to search? I am pretty sure that is not correct. They may not all have had radars capable of both search and track at the same time, but they did have radars that could both search and track.

For example, the F2H-2N had the APS-19 radar, a radar described in the 1946 Type Test as "a light-weight airborne radar capable of performing four different functions; namely, intercept for detection and location of aircraft; aim for firing of fixed guns by use of the indicator as a sight; search for detection and location of land, sea, air targets and navigation; and beacon for 'homing' purposes". Other versions of the F2H had other radars, such as the APQ-41, APG-37, APG-51, radars capable of both track and search.

The F4D had the APQ-50 radar, capable of track and search.

The F3H had the APG-30 and APG-51 radars, capable of track and search.

Most "all weather" fighters, from that point on, had radars that could both search for, and track to intercept / engage, targets. They had the ability to both search and track. Some may not have been able to do both at the same time, you could search or track, but not both, while others could multitask. Generally if they could do both at the same time they had more than one radar on board. Even when it was called one radar, like the APG-35 of the F3D-2 mentioned earlier in this thread, it was actually multiple radars working as an integrated unit. It was not until the fielding of phased array radars that single radar TWS really became common in aircraft.

T!

 

[Zipper730]

The P-61 may have entered service in mid 1944 (I don't know the date of entry to service), but it is a pre-war program. And the 6 P-61B-25-NO aircraft that were fitted with the APG-1/2 were, I believe, ordered in 1942.

So the system was connected to an additional computer that provided lead computation and so on.

You either need to develop a sight that works with the computer and radar to predict lead

Yeah, you'd take the data and project it onto a reflector site so you could simply put the reticle on target.

I think you are missing a key point here, gun laying radars are generally part of a turret / moving gun system.

True enough, and I guess that's a fire-control radar.

Unless I have lost track of what is being said, are you saying these aircraft had gun laying radars (lets call them by their correct term, Fire Control Radars, FCR) but no ability to search? I am pretty sure that is not correct. They may not all have had radars capable of both search and track at the same time, but they did have radars that could both search and track.

Then why was track while scan so big a deal? If these designs could both search and track simultaneously, isn't that the whole point?

 

[XBe02Drvr]

Then why was track while scan so big a deal? If these designs could both search and track simultaneously, isn't that the whole point?

You're just not getting it. Your basic AI radar right up to the advent of the F-teens generation fighters could search and could track (lock), but couldn't do both simultaneously. The difference is due to the antenna designs. Conventional AI radars had antennas that projected a radar "beam" from the center axis of the antenna dish and swept the sky ahead in a pattern of azimuth and elevation not unlike the scan pattern of an old CRT TV. This was accomplished by swinging the entire dish side to side and up and down while the operator watched for a momentary blip on the screen when the beam swung across a target. If a target was spotted the operator could take manual control of the antenna and its beam, focus it on the target and lock it on. Once locked on, the beam is no longer scanning, hence blind to any other targets out there, but does provide illumination of the target for the benefit of a radar guided missile. It's the signal generated by the locking (tracking) and illumination functions of the beam that sets off the missile warning alarms in the target's ECM gear.
The final generations of the F4 class fighters started to see phased array radars, which were the beginnings of "multitasking" track-while-scan radar. These units had a matrix of elements forming a fixed flat plate antenna rather than a moving parabolic dish. A beam could be electronically steered across a scan pattern by phase shifting the signal sent to the various elements of the plate's matrix. In this way, multiple beams could be generated tracking multiple targets while still having a functioning scan. Needless to say this didn't become feasible until huge advancements in miniaturization and computer circuitry had been achieved. I'm told today's Super Hornets have radars that combine the functions of the F4 and the A6 of my time, plus all this multi- tasking stuff, but over longer range at 1/3 the size, weight, and power consumption of either of those dinosaurs of my day.
Cheers,
Wes

 

[XBe02Drvr]

The F3H as originally designed was pretty impressive, but as time went on, the changes to make it into an all weather plane did exact some penalty in performance

When I was in, there were still pilots around who remembered the F3H, and called it "Delta Oscar Golf! Yeah, it was supersonic....balls-to-the-walls downhill with a tailwind. And by the time you got 1.01 on your machmeter you better be pointed towards homeplate, cause you're bingo fuel."
I don't know what the published stats were, but that was the pilot perspective.

The carriers mobility allows it's aircraft to be greatly more effective for their size, but it also means that you're closer to the enemy too, and you are not just within range of the longest range bombers with/without cruise-missiles, but shorter ranged aircraft including fighters.

When the F4H was in development, the shorter range air superiority (gun) fighter role was already being addressed by the F8U. The Phantom was intended to deal with long range mid ocean standoff missile attacks of the 4Bs variety (Beagle, Badger, Beauty, Blinder), as well as the nuclear delivery mission. Dogfighting just wasn't in the picture.

Unfortunately, they couldn't read the enemy IFF. I'm not sure if this had to do with newer Soviet IFF,

It had to do with the Soviets being more adept at intelligence and data collection than they were with electronics technology. While they weren't as advanced in raw technology, they were very good at copying and countering ours. They recorded and analyzed all kinds of electronic emissions and figured out how to ape them and fox them. Many a controller, suspicious of a transatlantic airliner that appeared on his scope a few minutes too soon, sent interceptors out to discover a Bear or a Backfire squawking the airliner's code and flying the airliner's flight planned route and speed. Once the bomber was intercepted and directed to squawk standby, the airliner's transponder would become visible a few miles in trail.
Also, it was not unheard of for US intelligence assets to use Soviet IFF codes.
Definitely not the scenario the F4 was designed for. BVR Verboten!

The F-106A had similar absolute range, but I could be wrong

The F106, while it had impressive radar range for a land based interceptor, was quite a different beast entirely. It was designed to operate in a totally GCI environment under SAGE control, so had narrower field of view in both elevation and azimuth, and its maneuvering gimble limits were tighter. Because the pilot had to fly both the airplane and the radar, task saturation had to be taken into account when laying out the operating options of the radar set. Again, the intended target was heavy bombers.
Cheers,
Wes

 

[Token]

Then why was track while scan so big a deal? If these designs could both search and track simultaneously, isn't that the whole point?

Read what I posted again, I did not say these could search and track at the same time, what I said was "They may not all have had radars capable of both search and track at the same time, but they did have radars that could both search and track". I also mentioned that the few who could do both simultaneously generally did this using multiple radars, not a single radar.

So until the advent of single radar TWS, as a general rule, if you had one FCR radar on board (most fighters had one FCR, and it was often a fight to find the space and weight for that one) you could either be in a search mode or in a track mode, but not both at the same time.

Even after single radar TWS and phased array, most radars really don't really do booth simultaneously, although they may appear to. See below for what I mean by that.

In this way, multiple beams could be generated tracking multiple targets while still having a functioning scan.

A minor correction here. Agree with all you said except for some minutia.

Most phased array radars do not really produce multiple beams at one time. Since there is no inertia to the virtual dish they form to make a beam they can move a beam location near instantly. This allows them to rapidly sequence from one location to another. For example if a radar is tracking 2 targets "at one time" it generally is really tracking one target at a time, but rapidly stepping back and forth between the two it has in track, so that in a human time scale it appears simultaneous.

A radar that has a dwell time of 5 msec and a frame time of 100 msec could potentially track 20 targets "simultaneously" (really one at a time, rapidly) and still provide target updates to the computer for each target 10 times a second. Or it could form a single target track beam while forming 19 search beams that same 10 times a second, this would allow an execution quality track while still looking in 190 different beam locations for search during one second. To a human it would look like search and track were happening at the same time, but the reality is it is rapidly sequencing.

It was not until the advent of AESA that multiple simultaneous beams really became a thing. And even then there are disadvantages to doing such. If you have an array / system capable of X power on target, and you make two equal beams to track two targets, you now have X/2 power on target. You have just significantly reduced your tracking range and probability of detection. It is generally still preferred to hit your potential targets with all you have to give, and rapidly sequence through them.

T!

 

[Zipper730]

You're just not getting it. Your basic AI radar right up to the advent of the F-teens generation fighters could search and could track (lock), but couldn't do both simultaneously.

I misinterpreted several different things that seemed to be contradictory.

a pattern of azimuth and elevation not unlike the scan pattern of an old CRT TV.

While this is totally off topic -- it's kind of amazing how complicated and fast acting the technology was needed just to create a workable TV. I mean taking an image, and then turning that into a signal that includes the basic data and transmitting it to a device that turns that into a whole bunch of lines that vary in light level and color across their widths about 24-30 times every second (old analog) in reliable detail.

This was accomplished by swinging the entire dish side to side and up and down while the operator watched for a momentary blip on the screen when the beam swung across a target. If a target was spotted the operator could take manual control of the antenna and its beam, focus it on the target and lock it on. Once locked on, the beam is no longer scanning, hence blind to any other targets out there, but does provide illumination of the target for the benefit of a radar guided missile. It's the signal generated by the locking (tracking) and illumination functions of the beam that sets off the missile warning alarms in the target's ECM gear.

That I get

When I was in, there were still pilots around who remembered the F3H, and called it "Delta Oscar Golf! Yeah, it was supersonic....balls-to-the-walls downhill with a tailwind. And by the time you got 1.01 on your machmeter you better be pointed towards homeplate, cause you're bingo fuel."

So it was supersonic in a very limited perspective...

When the F4H was in development, the shorter range air superiority (gun) fighter role was already being addressed by the F8U. The Phantom was intended to deal with long range mid ocean standoff missile attacks of the 4Bs variety (Beagle, Badger, Beauty, Blinder), as well as the nuclear delivery mission. Dogfighting just wasn't in the picture.

Are you sure about that? I was under the impression that the decision to use the F8U for close in combat was more of a decision based on the limits of the F4H? Regardless, I remember being told that the idea was to have the F4H's used (even in that case) to blow away a whole bunch of aircraft; then let the F8U's go in with their missiles and guns and cut-apart whatever was left?

The XF8U-3 had much of the agility of the F8U-2, but with greater speed, longer overall range, and similar radar to the F4H, but lacking an internal gun also (it could carry a gun-pack if need be, but the USN might not have had much interest -- the RNFAA was the one with that).

It had to do with the Soviets being more adept at intelligence and data collection than they were with electronics technology.

Actually I'm not sure that's true regarding the NSA, unfortunately I'm not sure if they told policy makers what they found (it seems to have little value to collect information when you have no intention to give it to the policy makers to make decisions based on).

While they weren't as advanced in raw technology, they were very good at copying and countering ours. They recorded and analyzed all kinds of electronic emissions and figured out how to ape them and fox them.

Like how if I didn't know the exact details how something worked but if I knew that "if I do this, then that and this -- this happens?"

Many a controller, suspicious of a transatlantic airliner that appeared on his scope a few minutes too soon, sent interceptors out to discover a Bear or a Backfire squawking the airliner's code and flying the airliner's flight planned route and speed. Once the bomber was intercepted and directed to squawk standby, the airliner's transponder would become visible a few miles in trail.

So they were jamming the airliner, then duplicating it and rebroadcasting it as their own? Not cool that it was done to us, it was pretty awesome in creativity.

Also, it was not unheard of for US intelligence assets to use Soviet IFF codes.

Like for reconnaissance operations? Smart...

To be honest, you could launch an absolutely awesome sneak-attack with something like that. You wouldn't even need the fastest aircraft, just one or two that could pass for airliners. Once through you could have some kind of malfunction occur (which isn't a malfunction but a series of maneuvers), and basically a whole bunch of chaff would be pumped out in a level never seen before, and the bombs would come off at the same time. Then a massive strike would follow while they're figuring out what happened.

In 1963 there was a claim that we could have built a 35 megaton warhead that could fit on a Titan II warhead, a 50-70 megaton warhead that could fit on a B-52, or a 100-megaton weapon that could be carried on a C-130 type aircraft based on existing knowledge.

Definitely not the scenario the F4 was designed for. BVR Verboten!

That decision was based on the start of the Vietnam War. Prior to that, the premise was BVR would be allowed for fighters too. Unfortunately, we couldn't read their IFF: If I recall, starting in 1962, we couldn't read the Cuban's IFF's (which is why I wondered if it was an export or communist block variant of the IFF, as I don't recall the F-106 drivers having any trouble).

The F106, while it had impressive radar range for a land based interceptor, was quite a different beast entirely. It was designed to operate in a totally GCI environment under SAGE control, so had narrower field of view in both elevation and azimuth, and its maneuvering gimble limits were tighter. Because the pilot had to fly both the airplane and the radar, task saturation had to be taken into account when laying out the operating options of the radar set. Again, the intended target was heavy bombers.

I'm not entirely sure about the gimbal limits, but I do remember the F-102 did have a terrain contour mapping feature as a navigation aid which seems to indicate it can aim at the ground.

SAGE basically guided the aircraft to a position where it would be able to carry out the intercept using it's own radar without using normal radio communications. That said, it had many different modes that included steering the aircraft into position by direct control of the autopilot (the throttle would be pilot controlled), with the pilot taking over to carry out the intercept (control would be resumed after); or simply displaying a steering dot for the pilot to superimpose his flight path on, with the intercept carried out by the pilot; voice-control to tell the pilot where to fly, the pilot radioing back, until into visual range.

The F4H-1 as intended didn't appear to be designed to use anything like SAGE, but during the development of the F4H-1 and XF8U-3, there was the USC-2 Datalink, which allowed the ability to remotely signal and maneuver an aircraft into a firing position (possibly command the firing), as well as auto-land features (SAGE could be used for auto-land as well). I'm not sure how often the USC-2 datalink was used on the F-4's, though there were some auto-throttle set-ups for landing in some cases.

Read what I posted again, I did not say these could search and track at the same time, what I said was "They may not all have had radars capable of both search and track at the same time, but they did have radars that could both search and track".

Sorry, I misread...

I also mentioned that the few who could do both simultaneously generally did this using multiple radars, not a single radar.

Is that why the F3H's had a beam-emitter separate from the radar to guide missiles (the AAM-N-2 was a radar-beam rider, and was slaved to the optical sight).
[quoteSo until the advent of single radar TWS, as a general rule, if you had one FCR radar on board (most fighters had one FCR, and it was often a fight to find the space and weight for that one) you could either be in a search mode or in a track mode, but not both at the same time.[/quote]I'm curious why they objected to this limit in WWII but not after?

Even after single radar TWS and phased array, most radars really don't really do booth simultaneously, although they may appear to. See below for what I mean by that.

Which means it would be rapidly switching from search to track and back and forth at such an incredibly fast rate that to the human brain it would seem like it was all happening simultaneously.

It was not until the advent of AESA that multiple simultaneous beams really became a thing. And even then there are disadvantages to doing such.

You end up divvying up power to produce the multiple beams?

 

[XBe02Drvr]

It is generally still preferred to hit your potential targets with all you have to give, and rapidly sequence through them.

Thanks for the detailed explanation. I was going to get into an analogy of chopped scan/alternate scan on an Oscope, but decided my complexity quotient was already getting out of hand. You made it clear and concise. Thanks.
Cheers,
Wes