Turret Fighters

[nuuumannn]

Thanks for that Dave. Aha. I found where I went wrong, I should have put that none of the P-61s delivered to the 422nd NFS at Charmy Down had turrets.

 

[GrauGeist]

Thanks for that Dave. Aha. I found where I went wrong, I should have put that none of the P-61s delivered to the 422nd NFS at Charmy Down had turrets.

No problem!

It is kind of confusing, because of all the types, some were equipped with a turret and some were not. Then, some of the turret equipped types were field modified by either having the turret removed or in some cases, had two of the four M2 MGs removed.

You'll also see in some cases, that an additional fuel cell was installed in the vacant turret well.

Here's a rough breakdown:
P-61A - 300 units.
Early series production: 180 units (all equipped with turret)
Late series production: 120 units (first 37 units with turret - remainder produced without turret option)

P-61B - 450 units.
Early series production: 200 units (produced without turret)
Late series production: 250 units (produced with turret)
P-61B-11 - 5 units: equipped with two .50 M2 in turret
P-61B-15 - 153 units: equipped with four .50 M2 in turret
P-61B-16 - 6 units: equipped with two .50 M2 in turret
P-61B-20 - 84 units: equipped with new GE turret with four .50 M2

P-61C - 41 units.
Turret application was a mixture in this series.

P-61D - 2 units.
Produced for high altitude research, no turrets.

 

[yulzari]

The turret fighter concept for the Boulton Paul Defiant had the turret guns, when locked forwards inclined above the airscrew disk, to be used by the pilot in a 'no deflection' mode whereby the drop of the rounds through gravity matched the sight for a given (adjustable) range so the sight merely had to be placed upon the target. This is why the pilot had the facility to fire the turret guns when so locked. No forward firing guns were seen to be needed as they were already there in this mode. Due to a variety of factors aircrews never had the appropriate sights, training, or indeed were made aware, of the intended forward firing method. All that they knew was that they could fire the turret guns when locked forward. When used in the nightfighter role the turret gunner both allowed fire from a variety of directions and gave two pairs of eyes to tell the difference between a Ju88/He111 and a Blenheim/Beaufighter. Also the gunners often had more gun training practice than some of the pilots. What it lacked was a 4x20mm cannon 'one burst, one kill' firepower.Six years previously 4x.303 machine guns were a good fighter weapon set. Six years later 30mm rotary breech HE cannons were pencilled in for new jet designs.

 

[stona]

Hi Milosh.

Mod. T 106. 22 May 1943

It meant that all Bf 110 night fighters leaving the production line or undergoing repair should be built to the following standard.

No GM-1 installation.

MG 17s in upper nose position to be replaced with MG 151/20s with flash suppressors.

MG 151/20s in lower nose to be replaced with MK 108s

MG 81Z in rear cockpit

2 x MG FF/M fitted in oblique firing (schrage musik) installation.

The ventral weapon tray was not to be fitted to aircraft built to this standard.

Cheers

Steve

 

[Stephan Wilkinson]

The original concept for the P-61 called for two turrets, one housed in the nose and one in the rear of the fuselage. Each turret was to have four .50 cal M2 Brownings.

Not believeable, since the original-original "concept for the P-61" required the nose to be filled not with guns but with the radar dish and ancillary equipment. There never was a P-61 concept that considered ordnance in the nose in place of the radar.

 

[GrauGeist]

Sorry that you have doubts, however the fact of the matter is, the P-61 went through several changes before it became the production series aircraft we are all familiar with.

Some of the changes to the original design were to place the two turrets above and below the fuselage. Then they changed again to placing a single turret atop the fuselage and placing the forward firing weapons (20mm cannon) in the wings. Eventually, they fitted the cannon in the fuselage.

The SCR-720 radar was of course, added and fitted to the nose during these changes.

What an aircraft design starts with is not always what the production aircraft ends up with...

 

[vikingBerserker]

The XP-61E had nose guns in place of radar.

 

[nuuumannn]

The turret fighter concept for the Boulton Paul Defiant had the turret guns, when locked forwards inclined above the airscrew disk, to be used by the pilot in a 'no deflection' mode whereby the drop of the rounds through gravity matched the sight for a given (adjustable) range so the sight merely had to be placed upon the target.

The thing is, as you mentioned, Yulzari is that the turret guns, when facing forward were not synchronised to the propeller and so the pilot ran the risk of shooting off his own propeller. To prevent the aircraft shooting off its own empennage, the turret had an ingenious mechanism that comprised a rotating drum that spun around at the same speed as the turret, which was driven by an electric motor. The drum had two brushes mounted vertically in it that made contact with slip rings, when the turret turned. These enabled the guns to fire and controlled each bank of guns to enable concentrated fire when the turret traversed past an obstructing part of the aircraft, the top controlled the right and the bottom the left guns. Patterns were cut out of the drum where brushes made contact with the slip rings where the aircraft obstructed the field of fire. This mechanism was fitted to all subsequent BP turrets including those on the Hudson and Halifax and worked quite well.

The Defiant's pilot did not have a gun sight. When trained forward, the turret's guns could not depress below 17 degrees above horizontal. Like I stated earlier, the gunner operated the master switch that controlled the turret and more often than not, the PILOT selection was wired off. Forward and aft of the turret were aerodynamic fairings, which were operated by actator arms worked by compressed air. These retracted automatically when the turret was turned.

Operation of the turret was simple. Once the gunner had strapped himself in and connected himself to the aeroplane; comms, oxy etc, he moved a lever to his left on the table in front of him forward from FREE to ENGAGED. This enabled the turret turning mechanisim to actuate. He would then switch on the sight, then switch on the safety switch from OFF to GUNNER and then switch on the main motor switch located above this to the gunner's right. A red warning light would indicate the system was energised. On the joy stick to his right, a trigger switch actually started the electric motor, which enabled the gunner to move the joy stick from left to right or foward and aft for rotation and elevation respectively. The trigger for firing the guns was a button located on the apex of the joystick and was actuated by pressing with the gunner's right thumb. There was also a high speed button, which enabled the turret to traverse at a faster than normal speed, located directly in front of the gunner on the table. This switched the electric motor on to a faster rpm to enable this, but it did not work for long as the gunner ran the risk of burning out the electric motor. The turret could also be operated manually by a crank handle, with gun elevation being controlled by tilting the gun butts up or down. The guns were mounted on their sides with the cocking handles facing upwards, which enabled the gunner to clear stoppages when required.

 

[Stephan Wilkinson]

The SCR-720 radar was of course, added and fitted to the nose during these changes.

The SCR-720 was hardly "added." It was the raison d'etre for the P-61 right from the outset. Whether or not somebody postulated putting guns in the nose is irrelevant. It was a dumb idea, and it's unimaginable why any engineer who knew what nightfighting was about would do it is hard to imagine. Any nightfighter crew that fired guns sited five or 10 feet directly in front of them would spend the next 10 minutes flying around like an old man tapping a white cane.

Yes, the XP-61E had guns in the nose, but it wasn't a nightfighter. It was proposed as a long-range escort dayfighter. which was also a dumb idea.

 

[wuzak]

Yes, the XP-61E had guns in the nose, but it wasn't a nightfighter. It was proposed as a long-range escort dayfighter. which was also a dumb idea.

IMO the P-61 would have been better if it had been set up like the XP-61E/F-15 Reporter with 2 crew, a bubble canopy, the 4 x 20mm cannon and, of course, the radar in the nose. It certainly would have performed better on the same power.

 

[Shortround6]

AH yes, but the trouble was that in the initial design stages the British were allowed to have input, sort of a joint specification in the fall of 1940, when the British were still enthralled with the turret fighter idea.

Of course by the time production examples became available the British had the Mosquito and forgotten (conveniently) about the turret fighter concept leaving the Americans stuck with it

Perfidious Albion strikes again

 

[GrauGeist]

Perfidious Albion strikes again

That in fact, is exactly the case. The British Purchasing Commission called for a "twin turret equipped" night fighter. Jack Northrop had started his design when the USAAC called for submissions shortly afterward. Jack abandoned the British request and went after the U.S. Army's request. This is where the P-61's design started evolving.

 

[yulzari]

the turret guns, when facing forward were not synchronised to the propeller and so the pilot ran the risk of shooting off his own propeller.

The Defiants pilot did not have a gun sight. When trained forward, the turret's guns could not depress below 17 degrees above horizontal. Like I stated earlier, the gunner operated the master switch that controlled the turret and more often than not, the PILOT selection was wired off.

Quite so Nuuumann. But the turret did have a 'pilot' selection and there was a provision for the pilot to fire the guns when so locked forward. The original concept would have had a pilots gunsight for 'no deflection' firing in this mode (e.g.the cannon armament in the Gloster 9/37) so as to allow the pilot to have fixed forward firing guns using the turret. Certainly the intention was to use the turret mode against unescorted bombers but the impetus to follow the forward firing mode through was not carried forward; possibly due to changes in staff. But the airframe/turret had the hardware. If the pilots had the training and gunsight the crews could have fought the Defiant in both turret and fixed gun modes without the extra weight of fixed guns in the wings.Essentially this was a human management failure, not a concept failure though the paucity of firepower and weight and drag of the turret was always going to make the turret fighter debatable at best.

 

[zoomar]

Back to the late 1930's, I've always wondered why the concept of a high-performance twin-engined fighter with a 4-cannon turret in the nose or immediately above the flight deck was not pursued more seriously by the British than it was. Mounted in this manner the 4 cannon were essentially a trainable nose armament that could be used in turning engagements with other fighters to compensate for the airplane's more limited manuverability. Or was the weight and complexity associated with a power turret just too much to make the concept practical?

 

[Shortround6]

There were drawings and models made of aircraft with such an arrangement.

The trouble was that most of the British firms could only handle 2-3 designs at the same time and they were already committed (or over committed) and building a real prototype would have taken too long, several years was the usual estimate.

 

[stona]

The trouble was that most of the British firms could only handle 2-3 designs at the same time and they were already committed (or over committed)

Most (if not all) the fighter specifications of the mid/late 1930s included the condition that the aircraft should be able to operate by night. Not much consideration was given to a specific, purpose built night fighter. No firm was going to go out on a limb developing something for which there was no clear need.
Was there a night fighter specification issued in the 1930s? The last one I can think of was back in the 1920s, 25/22, which resulted in the Hawker Woodcock. They were probably thinking more of Zeppelins than 200+ mph bombers
Cheers
Steve

 

[nuuumannn]

The original concept would have had a pilots gun sight for 'no deflection' firing in this mode

The spec for the Defiant came about as a result of the availability of the de Boysson turret for mass production by BP. Obviously, the pilot could control the guns, Yulzari, or the selector wouldn't have had a PILOT detent, but he did not have a gun sight. My point was that for the reasons stated it wasn't used in practise.

I've always wondered why the concept of a high-performance twin-engined fighter with a 4-cannon turret in the nose or immediately above the flight deck was not pursued more seriously by the British than it was.

There was the BP P.92 Boulton Paul P.92 - Wikipedia, the free encyclopedia

One Defiant was fitted experimentally with a turret that mounted a single 20 mm cannon, but it was not put into production, although later in the war BP did build cannon armed turrets for bombers.

Turrets enabled guns to be brought to bear quicker and more accurately than an unpowered gun position. From 1936 almost all bomber specs produced had them; B12/36, which the Stirling was a result of and P13/36, to which the Manchester was built specified powered turrets. At that time though, there were only two powered turret constructors that put powered turrets on aircraft in Britain pre-war, BP and Nash and Thompson, or Fraser Nash. Bristol turrets on Blenheims and Beauforts were not powered, nor were the Armstrong turrets on Ansons and early Whitleys. The Defiant was the design that was chosen for a turret fighter spec; did the British need another? Single seat fixed gun fighters were the major part of Britain's fighter defence; the turret fighter was designed solely for the destruction of enemy bombers.

They did come up with a few uses for turrets; In 1935 only one aircraft had a power operated turret, the BP Overstrand. The first design with a powered turret was the Sunderland, which was the first modern type, i.e. not an obsolescent biplane with fabric covering, like the Overstrand. Within three years, the Whitley IV had a powered tail turret and the Wellington I was fitted with them, but not all had turrets by the outbreak of the war. The Defiant did not enter service until December 1939 and part of the reason why was the usual British delays in prototype to production, but also because the turret took a while to get right for production. A variant of the Lysander was also fitted with a turret, the Delanne Lysander, which had a tail turret, so they were fitting them to what they could. Like I said earlier, the Air Ministry wanted Geoffrey de Havilland's high speed unarmed bomber to be fitted with a tail turret.

 

[Shortround6]

One of the "almosts" was the Boulton Paul P.92 which was supposed to mount four 20mm guns (+ four .303s?) in a 13 ft diameter low drag turret. It was ordered in prototype form but more urgent work delayed it but not before both a 2/7s scale model for wind tunnel tests and a just over 1/2 size piloted flying model were built.

Wind tunnel tests indicated that with the guns elevated 45 degrees and the turret turned 135 degrees drag increased by about 35% which may be one reason the big turret fighters never made it into the air.

 

[yulzari]

The spec for the Defiant came about as a result of the availability of the de Boysson turret for mass production by BP. Obviously, the pilot could control the guns, Yulzari, or the selector wouldn't have had a PILOT detent, but he did not have a gun sight. My point was that for the reasons stated it wasn't used in practise.

Forgive me Nuuumann. I should have been more specific. The concept of 'no deflection' aiming is that the round is fired at an angle above the horizontal. As it flies it drops at the same speed as if simply dropped without firing. By estimating the distance to the target the sight can be set to match the fall of the bullet at that distance. In the case of the Defiant they angled above the horizontal was 17 degrees so there was no need to synchronise them to the airscrew as they would pass above the disk.

I certainly agree that there was no such sight fitted but the concept had a certain hold in the Air Ministry in the mid/late 1930's and it was a recognised option for a fixed gun as proposed in the Gloster for example. What appears to have happened is that the impetus died out and the sights were never made, but they were originally pencilled in the Defiant design concept and such gun sight types were trialed. Albeit not in a Defiant. My point is that there was no technical reason why the pilots could not have had such a 'no deflection' sight to use the turret guns fixed forwards at 17 degrees elevation. Had they been fitted and the pilots trained to use them then the option to use the guns as fixed forward firing armament or as a mobile turret would have been available without added weight of extra guns in the wings.

It did not happen and we can only speculate what tactics would have been found best. I suspect that the gunner would have been the user in tackling bombers without close escort and the pilot when dealing with the escorts. The gunner being able to reassert control if the Defiant came under attack from the rear. One reason for the turret was for a gunner to be able to fire a more prolonged burst parallel to the bomber than a pilot closing at speed. The WW1 Bristol F2B Fighter gives an imperfect model of the technique.

This is the reason why there was a function in the Defiant for the pilot to fire the turret guns. A relic of a missed opportunity.

However, as I said above. There was no way a viable one burst one bomber kill firepower was going to be fitted into a viable fighter turret but the Defiant turret firepower matched contemporary fighters at the time it was designed. The Boulton Paul P.92 above shows that this was appreciated and the problems with turrets big enough to hold the necessary weapons. Even that was dwarfed by the 40mm gun turret trialled on the Wellington. Though that was more of a flying anti aircraft battery concept than a bomber hunter.

 

[wuzak]

The Gloster G.39 (F.9/37) was fitted with no allowance guns, in the lower fuselage and in the upper fuselage behind the cockpit.