Development of MAT and HAT (Monoplane- and Hinged Air Tail)

[GreatDaeld]

Greetings!

I have been going through available information regarding the development of Monoplane Air Tail (MAT) in the RN/RAF.

From what i have gathered the MAT itself is based on the patent for a mechanical aid called "Bull Gear", invented by Captain J.A. Bull of the Royal Norwegian Navy. See attached patent. Controlled descent by means of pivoted rods controlled by air vanes on the sides of the torpedo. This was tested and used with the Vildebeest from 1935 and onwards. But the overall experience proved costly, and some further development was found to be needed.

The MAT themselves were first Mk I's through III, where the design changed some, but the overall function was the same. The descent of these MATs were controlled by a Drum Control Gear (DCG) stored in the torpedo-carrying aircraft. The torpedo was controlled by the DCG by two 18-foot wires attached to each horizontal rudder. This way the initial descent of the torpedo could be controlled so the nose would fall faster than the rear, thus gaining a favourable attitude for the optimal water-entry. The air tail would maintain the attitude after the wire would be expended, and detach itself from the torpedo upon entry into the water. The wires would also control any initial roll after release. The MATs gave some limitations to the carrying aircraft due to its span. Most aircraft did not carry their torpedoes externally but rather recessed or internally. Some aircraft were modified so the MATs could be fitted, while other solutions were made for aircraft like the Vickers Wellington.

The Hinged Air Tail (HAT) was designed as to fit inside the bomb bay of the Vickers Wellington. The HAT was controlled by the DCG, almost the same as the MAT Mk I-III. The difference was that the HAT only used one 18-foot wire per torpedo.

The downside of the use of the DCG for both the MAT Mk I-III and HAT was that the aircraft had to maintain its attitude until the 18-foots of wire had been expanded, thus leaving the aircraft and its crew extremely exposed. To overcome this, the MAT Mk IV was designed with its own gyroscope. The gyroscope would control the horizontal rudders in the air, and the mechanism was engaged upon release from the aircraft. This ensured that the torpedo aircraft could release their torpedoes and immediately begin maneuvering away.

A further development, the MAT Mk V, came as result of the increased performance of the carrying aircraft and the increased danger associated to launching torpedo attacks. The MAT Mk V was an MAT Mk IV upgraded with a drogue parachute to enable the aircraft to launch torpedoes at higher speeds and altitude than before.

MAT Mk VI i have seen mentioned as the title of a AVIA 16 ATDU report, but i have not found anything related to a post-war development of the MATs anywhere else. AVIA 16 in question: https://discovery.nationalarchives.gov.uk/details/r/C2378298.


TIMELINE

Bull Gear: 1935, the control mechanism was built into the aft section of the torpedo.


MAT Mk I: unknown year, 50-inch neutral air-foil, see photo below.

MAT Mk II: Unknown year, have not found any photos or information regarding specifics for this one.


MAT Mk III: Unknown year, wedge-section wings with adjustable flaps and endplates. Likely the most numerous type of the MATs. See photo below.

HAT: Unknown year, i have been unable to find much more information regarding the HAT.


MAT Mk IV: ~1943, horizontal stabilizers controlled by a gyroscope.


MAT Mk V: ~1945, MAT Mk IV fitted with a drogue parachute

MAT Mk VI: 1947, post-war development with unknown result.



The photos and most of the information i collected from RAF Historical Society Journal 45, attached.



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I would greatly appreciate any inputs towards this matter, as i am very interested to learn more!

 

[EwenS]

As as you will be aware, page 128 of the RAF Historical Society Journal has a photo of the Bull Gear as fitted to the Mk.XIV torpedo and notes

"This expensive and complicated fitting was mainly
associated with the fast but equally complicated and therefore disliked
Mk XIV torpedo of 1935 and was associated almost exclusively with
the RAF's Vildebeest biplane. The Mk XIV torpedo was some 220 lbs
heavier and 30% faster than the Mk VIII it replaced, and carried
slightly more explosive."

The last Vildebeest squadrons in the RAF were in Malaya and flew operationally against the Japanese in Dec 1941 / Jan 1942 (36 & 100 squadrons). Navweaps has a note for the Mk.XIV torpedo:-

"Almost the entire stock of this model was lost with the surrender of Singapore. Considered to be less robust than the Mark XII. Use methylated spirits as fuel."

World War II Torpedoes of the United Kingdom/Britain - NavWeaps

www.navweaps.com

I'm not aware of the RN ever having used the Mk.XIV. They moved from the WW1 era 18" Mk.VIII torpedo to the Mk.XI designed in 1934, which entered service in 1936, to the improved Mk.XII designed in 1935 as an improved Mk.XI, which entered service in 1937. This became the main air launched torpedo for both the RN & the RAF in the first half of WW2. It was superseded by the Mk.XV designed in 1942 which entered service in 1943 with both services.

Regarding carriage of torpedoes, RN aircraft like the Swordfish, Albacore and Barracuda and the RAF Vildebeest all carried their torpedo externally. The bomb bays of both the Wellington and the Hampden had to be modified to allow torpedo carriage.

There is an RAF training film about the operation of the Mk.XII torpedo dated 1942 that I have posted before that shows:-
1. The operation of the MAT from about 16.40 and,
2. The MAT being fitted to a Mk.XII torpedo after the torpedo had been loaded onto a Beaufort from 32.00 onwards.

The purpose of The Drum Control Gear was simply to stabilise the torpedo for the very short period of time that it was subject to the disturbed airflow around the dropping aircraft. Given the effects of gravity on an object like a torpedo falling clear of an aircraft, it would only have been a matter of just over a second before the reels unwound their 18ft of wire. After that the air vane attached to the side of the torpedo in conjunction with the servo motor (part of the depth keeping mechanism after the torpedo enters the water) and connected to the MAT kept the torpedo in the correct attitude.and The film probably explains it better.

View: https://www.youtube.com/watch?v=L9ooDSXtlHc

While the RN fitted MAT to torpedo carrying Barracudas, I've never seen a MAT equipped torpedo on a Swordfish or Albacore. Barracudas only undertook one operational torpedo dropping sortie, despite the years of training the crews put in.

The necessity for the later MAT gear versions for faster aircraft largely disappeared with the end of WW2. For the RAF plans to re-equip Coastal Command strike squadrons with the Bristol Brigand TF.1 died in early 1946. Post-war the torpedo dropping function in the RN moved to the Firebrand, but existing equipment proved adequate for it. While the Westland Wyvern was designed as a successor, by the time it became operational it was designated as a Strike aircraft using bombs and rockets.

 

[GreatDaeld]

As as you will be aware, page 128 of the RAF Historical Society Journal has a photo of the Bull Gear as fitted to the Mk.XIV torpedo and notes

"This expensive and complicated fitting was mainly
associated with the fast but equally complicated and therefore disliked
Mk XIV torpedo of 1935 and was associated almost exclusively with
the RAF's Vildebeest biplane. The Mk XIV torpedo was some 220 lbs
heavier and 30% faster than the Mk VIII it replaced, and carried
slightly more explosive."

The last Vildebeest squadrons in the RAF were in Malaya and flew operationally against the Japanese in Dec 1941 / Jan 1942 (36 & 100 squadrons). Navweaps has a note for the Mk.XIV torpedo:-

"Almost the entire stock of this model was lost with the surrender of Singapore. Considered to be less robust than the Mark XII. Use methylated spirits as fuel."

World War II Torpedoes of the United Kingdom/Britain - NavWeaps

www.navweaps.com

I'm not aware of the RN ever having used the Mk.XIV. They moved from the WW1 era 18" Mk.VIII torpedo to the Mk.XI designed in 1934, which entered service in 1936, to the improved Mk.XII designed in 1935 as an improved Mk.XI, which entered service in 1937. This became the main air launched torpedo for both the RN & the RAF in the first half of WW2. It was superseded by the Mk.XV designed in 1942 which entered service in 1943 with both services.

Regarding carriage of torpedoes, RN aircraft like the Swordfish, Albacore and Barracuda and the RAF Vildebeest all carried their torpedo externally. The bomb bays of both the Wellington and the Hampden had to be modified to allow torpedo carriage.

There is an RAF training film about the operation of the Mk.XII torpedo dated 1942 that I have posted before that shows:-
1. The operation of the MAT from about 16.40 and,
2. The MAT being fitted to a Mk.XII torpedo after the torpedo had been loaded onto a Beaufort from 32.00 onwards.

The purpose of The Drum Control Gear was simply to stabilise the torpedo for the very short period of time that it was subject to the disturbed airflow around the dropping aircraft. Given the effects of gravity on an object like a torpedo falling clear of an aircraft, it would only have been a matter of just over a second before the reels unwound their 18ft of wire. After that the air vane attached to the side of the torpedo in conjunction with the servo motor (part of the depth keeping mechanism after the torpedo enters the water) and connected to the MAT kept the torpedo in the correct attitude.and The film probably explains it better.

View: https://www.youtube.com/watch?v=L9ooDSXtlHc

While the RN fitted MAT to torpedo carrying Barracudas, I've never seen a MAT equipped torpedo on a Swordfish or Albacore. Barracudas only undertook one operational torpedo dropping sortie, despite the years of training the crews put in.

The necessity for the later MAT gear versions for faster aircraft largely disappeared with the end of WW2. For the RAF plans to re-equip Coastal Command strike squadrons with the Bristol Brigand TF.1 died in early 1946. Post-war the torpedo dropping function in the RN moved to the Firebrand, but existing equipment proved adequate for it. While the Westland Wyvern was designed as a successor, by the time it became operational it was designated as a Strike aircraft using bombs and rockets.

Thank you for the informative reply!

I have seen that training film, it is really thorough and a good addition to the thread! It looks to me as the MAT portrayed is the Mk III, with its endplates. Interestingly, the air vane can also be seen on the Bull Gear, marked as number 15 on the patent sheet. Its called the "auxiliary rudder".

Regarding the Bull Gear and Vildebeests, I am of the opinion that it is rather dubious whether the Bull Gear was kept operable until the surrender of Singapore. As it was stated to be an expensive mechanism and other, more affordable designs appeared. But then again, I am not certain the MATs could be used for the Mk XIV torpedo.

The figure showcasing the MAT Mk I above was borrowed from the RAF Society Historical Journal 45, page 130, with the description: A Mk I Monoplane Air Tail (MAT) fitted to a Mk XII torpedo on a Swordfish with its Drum Control Gear (DCG) discernible within the fuselage. I have also found a photograph with what looks like a MAT Mk III: Swordfish. I believe the development of the MATs and similar were considered a secret during the war, hence very few photographs were taken of these devices.

Also found some photos of Albacores with what could be MATs with endplates: Albacore 1, Albacore 2. Some weird colours/shadows, but could be explained by a differing colour between the MAT and the torpedo itself.

Yes, the Journal 45 described the relationship between the torpedoes and the torpedo-aircraft well: the performance of the aircraft always being one step ahead of the torpedoes it was supposed to carry. This chase came to an end some time after the end of the second world war for different reasons.

 

[EwenS]

Thanks for the photos.

The one of the Swordfish triggered a memory of where I had seen it before. It is of either Swordfish II serial DK747 or HS671 (probably the latter) during RATOG trials at RAE Farnborough during Dec 1943. Info taken from "Farnborough and the Fleet Air Arm" by Geoffrey Cooper who was employed at the RAE in WW2 and beyond. You can see the stubs of the RATOG rockets under the trailling edge of the wing with the rocket blast extending aft of the aircraft which is just at the point of becoming airborne. The variety of aircraft in the background, including an Avenger, and the distinctive buildings reinforce the location.

So a trials aircraft not an operational one. Aircraft used for that purpose could be fitted to carry all sorts of non-standard equipment.

By December 1943 the Swordfish had been superseded in the torpedo bomber role by the Barracuda TBR.II. By then they were being used from escort carriers and MAC ships in the ASW role using rockets or depth charges, or attached to Coastal Command operating over the southern North Sea and English Channel in the anti-shipping role (particularly anti E-boat) using rockets or 250lb bombs.

I'll look into the Albacore photos more deeply tomorrow.

 

[GreatDaeld]

Yes, it does look like it is fitted with the ring on the nose, instead of a pistol. I imagine the wide MAT could be a cause for concern, so it may very well be testing of the RATO gear in unison with the MAT. Interesting read, the chapter regarding the RATOG!

Swordfish, here is another photo. The torpedo is fitted with a pistol, and what resembles a MAT Mk I can be viewed in the back. Again, not a perfect photo!