Help needed: Loadout on TBM-3 with Fido and Radar

[Conslaw]

I'm trying to find out what a typical loadout would be for a late-war TBM with a Mk 24 "fido" homing torpedo. Specifically, how was the Fido carried, and what else could be carried at the same time? Would TBM-3s from escort carriers carry HVAR rockets on anti-sub patrols? What about droptanks?

 

[YGBSM]

The first distinction to make is between the plural of TBM-3 (an upgraded base model which had many variants) and the specific model TBM-3S, which was a post-war ASW variant. The TBM-3S is most recognizable due to the removal of the rear turret and the installation of a rear cockpit in its place for the radar operator.

The type which operated from escort carriers during the war would have been the TBM-3 (in general) and the TBM-3D and TBM-3E which you can remember by thinking (additional) "electronics" - this is the wartime version equipped with the APS-4 radar, hung under the right wing. The TBM-3D was an upgraded ASW variant from the TBM-1D type, fitted with an ASD radar built into the right wing and often a searchlight hung from the left wing.

The British Fleet Air Arm equivalent model TBM-3 / TBM-3 D/E was designated the Avenger III. As you can imagine, the addition of a radar was quite helpful to discover surfaced subs charging their batteries at night or even detecting their periscope / snorkel instrumentation under the right conditions. The base TBM-3 model is where the hardpoints for drop tanks and rockets were introduced. I believe British penetrator rockets were used first for ASW which were then replaced by the HVAR rockets when they became available.

Keep in mind that a set of four 350lb depth charges were much more likely to be used than the Mk 24 torpedo - I just looked and only 340 Mk 24s were launched in the entire war, including both theaters of war and all aircraft which used them (I know PBY Catalinas / Cansos) used them in addition to the Avengers... not sure if any other types did. As you can imagine, that pales in comparison to the number of aerial depth charges dropped....

That said, if equipped with a Mk 24 torpedo, there wouldn't be any issue with equipping rockets and drop tanks assuming a 'late war' TBM-3D or E was used (the tanks were hung inboard of the rockets). The torpedo of course would be held in the bomb bay - the Mk 24 was quite a bit shorter than a standard Mk 13 as well as lighter, so there technically should have been room and weight capacity to perhaps carry a depth charge to two in addition. That said, I haven't heard of mixed armaments being used, as the attachment points in the bay would also need to be modified to do that. These attachment points were already quite complex to handle two very different torpedo types, depth charges, various bomb configurations, and even smoke tanks. Note that on the 3E variant, the APS-4 would have been hung in lieu of the rocket mounts on the right wing. I'm not sure if it was common practice to hang rockets from the other wing, although it technically would be possible.

This cutaway can give you an idea of the general layout of the ordnance. But you can see starting from the outside of the wing, working inward:
(1) attachment point for externally mounted radar (APS-4 as carried on the 3E variant) or four rockets - on the 3D I believe this space was still available for rockets on the right wing as the APS-3 radome was built into the leading edge of the wing at that location.
(2) center pylon which could carry a depth charge, small bombs, or a 58gal or 100gal drop tank
(3) internal bomb bay with either four depth chrages, one Mk 13 or Mk 24 torpedo, or a smoke tank.

Source: conceptbunny.com


This will give you an idea of a 3D configuration with the APS-3 and searchlight combo plus rockets. Add the Mk 24 into the bomb bay, and you're good to go.

Source: U.S. Navy Aircraft History: Post-War Eastern TBM Variants


Hope that helps!

 

[Conslaw]

Thanks for the info.

This picture looks like it has a Yagi antenna on the left wing, and the standard APS-4 radome on the right as well as at least one rocket.

The first distinction to make is between the plural of TBM-3 (an upgraded base model which had many variants) and the specific model TBM-3S, which was a post-war ASW variant. The TBM-3S is most recognizable due to the removal of the rear turret and the installation of a rear cockpit in its place for the radar operator.

The type which operated from escort carriers during the war would have been the TBM-3 (in general) and the TBM-3D and TBM-3E which you can remember by thinking (additional) "electronics" - this is the wartime version equipped with the APS-4 radar, hung under the right wing. The TBM-3D was an upgraded ASW variant from the TBM-1D type, fitted with an ASD radar built into the right wing and often a searchlight hung from the left wing.

The British Fleet Air Arm equivalent model TBM-3 / TBM-3 D/E was designated the Avenger III. As you can imagine, the addition of a radar was quite helpful to discover surfaced subs charging their batteries at night or even detecting their periscope / snorkel instrumentation under the right conditions. The base TBM-3 model is where the hardpoints for drop tanks and rockets were introduced. I believe British penetrator rockets were used first for ASW which were then replaced by the HVAR rockets when they became available.

Keep in mind that a set of four 350lb depth charges were much more likely to be used than the Mk 24 torpedo - I just looked and only 340 Mk 24s were launched in the entire war, including both theaters of war and all aircraft which used them (I know PBY Catalinas / Cansos) used them in addition to the Avengers... not sure if any other types did. As you can imagine, that pales in comparison to the number of aerial depth charges dropped....

That said, if equipped with a Mk 24 torpedo, there wouldn't be any issue with equipping rockets and drop tanks assuming a 'late war' TBM-3D or E was used (the tanks were hung inboard of the rockets). The torpedo of course would be held in the bomb bay - the Mk 24 was quite a bit shorter than a standard Mk 13 as well as lighter, so there technically should have been room and weight capacity to perhaps carry a depth charge to two in addition. That said, I haven't heard of mixed armaments being used, as the attachment points in the bay would also need to be modified to do that. These attachment points were already quite complex to handle two very different torpedo types, depth charges, various bomb configurations, and even smoke tanks. Note that on the 3E variant, the APS-4 would have been hung in lieu of the rocket mounts on the right wing. I'm not sure if it was common practice to hang rockets from the other wing, although it technically would be possible.

This cutaway can give you an idea of the general layout of the ordnance. But you can see starting from the outside of the wing, working inward:
(1) attachment point for externally mounted radar (APS-4 as carried on the 3E variant) or four rockets - on the 3D I believe this space was still available for rockets on the right wing as the APS-3 radome was built into the leading edge of the wing at that location.
(2) center pylon which could carry a depth charge, small bombs, or a 58gal or 100gal drop tank
(3) internal bomb bay with either four depth chrages, one Mk 13 or Mk 24 torpedo, or a smoke tank.

View attachment 501011
Source: conceptbunny.com


This will give you an idea of a 3D configuration with the APS-3 and searchlight combo plus rockets. Add the Mk 24 into the bomb bay, and you're good to go.

View attachment 501012
Source: U.S. Navy Aircraft History: Post-War Eastern TBM Variants


Hope that helps!

 

[Conslaw]

The FIDO was very effective.

Some Statistics on the Mark 24 "mine" a/k/a "Fido homing torpedo: About 4000 were produced. (Planned production was 10,000, but they decided they had all they needed at 4,000.) It was successful in about 22% of its attacks.

Number of attacks in which Mark 24s were launched 264
Total number of Mark 24 torpedoes launched - all targets 340
Number of Mark 24s launched against submarines 204
Number of Mark 24 attacks on submarines by US aircraft 142
Number of Mark 24 attacks by Allied (primarily British) aircraft 62
Number of German U-boats sunk by FIDO 31
Number of German U-boats damaged by FIDO 15
Number of Japanese submarines sunk by FIDO 6
Number of Japanese submarines damaged by FIDO 3
Total number of submarines sunk by FIDO (German & Japanese) 37
Total number of submarines damaged 18
General characteristics

Source - Wikipedia

 

[CORSNING]

I think YGBSM pretty much nailed it Conslaw. If you want a little
bit more information on the TBM-3 go to
Standard Aircraft Characteristics Arcive and scroll down a little.
, Jeff

 

[YGBSM]

Thanks for the info.

This picture looks like it has a Yagi antenna on the left wing, and the standard APS-4 radome on the right as well as at least one rocket.

As far as I'm aware, the APS-4 was only slung under the wing in a pod. The APS-3 was built into the leading edge of the wing. If you deleted the rockets from the right wing and hung the APS-4 there, you would have a good representation of a 3E model loadout.

EDIT: I did some more reading, and the presence of the YAGI antennas on the top of both wings meant that an ASD-1 radar had been mounted in the starboard wing radome (replacing the earlier APS-3). Avengers mounted with the ASD-1 were designated TBF-1D or TBM-1D and later TBF/TBM-3D. Not all 1D examples carried the YAGI antennas, as they were not part of the ASD system but in addition carryovers from the original ASB radar system.

The FIDO was very effective.

Some Statistics on the Mark 24 "mine" a/k/a "Fido homing torpedo [...]

I did not mean to imply that the Mk 24 was ineffective, just that it was relatively rare compared to how many depth charges were used. It did indeed have an impressive kill ratio.


Out of curiosity, are you planning to build a model?

 

[YGBSM]

Some additional info regarding the Mk4 and Mk5 rocket launchers as well as the Mk 54 depth charges:

Source (for all three): Squadron Signal - Aviation in Action #1082

The picture I posted previously of the 3D model with the searchlight is equipped with the Mk 5 / HVARs system.

A couple more notes:
1. A camera was sometimes hung outboard of the rocket rails in order to capture footage of rocket attacks on submarines.
2. The standard USN Atlantic ASW color scheme was Dark Gull Gray and Insignia White.
3. This will give you a general idea of what they would have looked like:

Source: Squadron Signal - Aviation in Action #1082

 

[fubar57]

Any idea what the camera looked like? I've searched high and low in books and on the web. I've found similar looking camera but not the right one
The photo below is from here as well as many other sites...Tailhook Topics: World War II ASW Schemes versus the Norfolk Scheme

​

...and grabbed this off the web a long time ago...

 

[YGBSM]

There were a few types of cameras used:
1. A 35mm camera mounted fore of the cockpit windscreen - this would be used as a typical gun camera.
2. A camera mounted in lieu of the ventral machine gun - this would be used primarily for recording rocket attacks. It would be difficult to visually identify an Avenger with this option, so historical notations must be relied upon.
3. The pictures you posted both are good examples of the external cameras used to record rocket attacks. As shown, the camera was typically mounted just outboard of the rocket mounts on the port wing.
4. Various handheld cameras used inside the cockpit by the crew. I doubt these had much use in recording attacks in progress, but they could be used to record target damage after the attack.
5. The 3P variant with camera equipment installed in the bomb bay. This variant's primary mission would be photo recon, so it would be identifying targets for later raids as well as recording results afterwards.


Interestingly, here is the photographic basis for the art you posted:

Source: Squadron Signal


If you're asking for a close-up on the camera itself... I'm not sure exactly which cameras were used. As a general representative of what might be used, here is a Fairchild K-20 aerial camera (shown as handheld here):

Source: airandspace.si.edu

What's shown above would need to be modified for the external mount. Also, I believe the Royal Navy FAA did not necessarily use the same camera equipment as the USN, so there's that factor too. I wouldn't be surprised if many camera types were used with many of them falling under 'field modifications' to make what was available work for the task at hand.

 

[YGBSM]

In a pilot's handbook, I found a diagram of how a Mk 13 torpedo would be mounted in the bomb bay. A Mk 13 was ~161 inches while the Mk 24 was about half that at 84 inches. Diameters were similar at 22-1/2" and 19" respectively. I haven't seen any diagrams with the Mk 24 specifically. I haven't seen any discussion whether the Mk 24 required modifications to the bomb bay; it would be desirable to minimize any such modifications, so I think it's a safe assumption that the Mk 24 would use the same bomb bay hardware and would roughly be centered in the bay or perhaps be a bit aft of center.

Source: AN 01-190EB-1 TBM-3 Pilot's Handbook

 

[YGBSM]

NOTE: the images wouldn't display when I tried to edit them into the post above.

An illustration of what the bomb bay would look like with two 500lb bombs (four total could be carried).

Bomb bay with the torpedo sway braces installed (view from the front looking aft):

Source (both): TBM/TBF Avenger in Detail

 

[pinehilljoe]

There were a few types of cameras used:
1. A 35mm camera mounted fore of the cockpit windscreen - this would be used as a typical gun camera.
2. A camera mounted in lieu of the ventral machine gun - this would be used primarily for recording rocket attacks. It would be difficult to visually identify an Avenger with this option, so historical notations must be relied upon.
3. The pictures you posted both are good examples of the external cameras used to record rocket attacks. As shown, the camera was typically mounted just outboard of the rocket mounts on the port wing.
4. Various handheld cameras used inside the cockpit by the crew. I doubt these had much use in recording attacks in progress, but they could be used to record target damage after the attack.
5. The 3P variant with camera equipment installed in the bomb bay. This variant's primary mission would be photo recon, so it would be identifying targets for later raids as well as recording results afterwards.


Interestingly, here is the photographic basis for the art you posted:

View attachment 501364
Source: Squadron Signal


If you're asking for a close-up on the camera itself... I'm not sure exactly which cameras were used. As a general representative of what might be used, here is a Fairchild K-20 aerial camera (shown as handheld here):
View attachment 501365
Source: airandspace.si.edu

What's shown above would need to be modified for the external mount. Also, I believe the Royal Navy FAA did not necessarily use the same camera equipment as the USN, so there's that factor too. I wouldn't be surprised if many camera types were used with many of them falling under 'field modifications' to make what was available work for the task at hand.

interesting, my Mother's wartime job was working for Fairchild in NYC assembling cameras

 

[Barrett]

Tremendous response, guys. As the Brits would say, Pukka Gen.

It's worth noting that almost every advancement in torpedo technology during the war came from industry, not BuOrd let alone the Newport Torpedo Station. Hedy Lamarr, apart from being arguably the most beautiful female of her generation, became co-holder on the technology that led to acoustic homing and frequency-agile radios. (He first husband was an Austro-Hungarian ordnance baron. Or something.)

We all know about the egregious situation that persisted within the USN ordnance fiefdom. It went way back: later Fleet Admiral Wm. Leahy had run BuOrd when most of the WW II generation of torps were designed. He was recalled to duty as FDR's briefcase carrier. (A former DC staffer insisted that Leahy got his 5th star so the Brit field marshals would return his calls.)

One of my occasional email colleagues is "Gummi" up there in Iceland, webmaster of Uboat.net which makes the finals for title of best naval website. Long ago he mentioned that some of the KM ordies who designed defective torpedo detonators went to prison. I had to admit that ours made admiral...

 

[Conslaw]

Some additional info regarding the Mk4 and Mk5 rocket launchers as well as the Mk 54 depth charges:

View attachment 501358

View attachment 501359

View attachment 501360
Source (for all three): Squadron Signal - Aviation in Action #1082

The picture I posted previously of the 3D model with the searchlight is equipped with the Mk 5 / HVARs system.

A couple more notes:
1. A camera was sometimes hung outboard of the rocket rails in order to capture footage of rocket attacks on submarines.
2. The standard USN Atlantic ASW color scheme was Dark Gull Gray and Insignia White.
3. This will give you a general idea of what they would have looked like:
View attachment 501361
Source: Squadron Signal - Aviation in Action #1082

YGBSM - Thanks for this info. I didn't realize that they used a cammo pattern especially for ASW operations - but it makes sense since the did research on active cammoflage in the "Yahudi" project earlier. It makes sense that they would at least implement whatever passive cammoflage that they could.

 

[Conslaw]

Thanks to everybody who has commented on this thread.

I kind of got distracted from this thread and just got back to it. Going back to the focus of my original question, If I was taking off for a routine ASW mission, say fall of 1944, what would I likely be carrying. For example, could I carry a couple rockets, a bomb, a depth charge and a Mk 24? If not, what could I carry together? Also, what about Sono Buoys? Where would they go? what would they displace? How many were carried? Whose job was it to listen to them. I'll quit before I start sounding even more like Mr. Richard Fader from Fort Lee, New Jersey.

 

[fubar57]

PM sent

 

[fcorsair]

The Mark 24 was designed to have roughly the same dimensions as a 1,000lb bomb and was usually carried in the forward part of the TBF/TBM's bomb bay.

Typical loadout for late 1943 and 1944 was a pair of depth bombs at the rear of the bay, six AN/CRT-1 sonobuoys, three on each side at the front, and a Mark 24 in the centerline position between the sonobuoys. Here' s a picture with the Mark 24 removed (it was top secret and photographing them was absolutely forbidden):

File:TBM bomb bay w sonobuoys.jpg - Wikimedia Commons

 

[Conslaw]

The Mark 24 was designed to have roughly the same dimensions as a 1,000lb bomb and was usually carried in the forward part of the TBF/TBM's bomb bay.

Typical loadout for late 1943 and 1944 was a pair of depth bombs at the rear of the bay, six AN/CRT-1 sonobuoys, three on each side at the front, and a Mark 24 in the centerline position between the sonobuoys. Here' s a picture with the Mark 24 removed (it was top secret and photographing them was absolutely forbidden):

File:TBM bomb bay w sonobuoys.jpg - Wikimedia Commons

Thanks for the info. Were the sonobouys toggled like bombs? How did the pilot choose what to drop at a given time? As I understand it, this type of sonobuoy was a passive sonar - diredtional microphone based, that would broadcast a radio signal of the sounds heard that the operator could receive on his earphones. When you dropped multiple buoys, how did you choose between them for sounds? How did you use them to determine the location of the submarine?

 

[fcorsair]

Thanks for the info. Were the sonobouys toggled like bombs? How did the pilot choose what to drop at a given time? As I understand it, this type of sonobuoy was a passive sonar - diredtional microphone based, that would broadcast a radio signal of the sounds heard that the operator could receive on his earphones. When you dropped multiple buoys, how did you choose between them for sounds? How did you use them to determine the location of the submarine?

A standard attack on a U-boat was supposed to go something like this:

An Avenger out on patrol would spot a U-boat either visually or on radar. If possible the pilot would work his way round to try and make his initial attack out of the sun, using rockets to try and damage the sub to the point that it couldn't submerge.

If the sub did manage to dive, the Avenger would make a second run and drop both depth charges 'ahead of the swirl', that is at the point where the boat would probably be given its forward motion after diving. The DCs were usually set fairly shallow, say 50ft, the idea being to hit the sub before it managed to get too far away from its initial diving point and before it got too deep.

Then, the Avenger pilot would drop the sonobuoys. Each buoy was identified by a colour, shorthanded as POBRY: purple, orange, blue, red, yellow. The sixth AN/CRT-1 was green, and that was kept as a a backup in case one of the others failed, or if more verification of a contact was needed. Each sonobuoy included a dye marker in the same colour so it was more visible from the air, and transmitted on its own frequency. The Avenger would fly a 'shamrock' pattern like so to drop the buoys in a cruciform shape:

In the Avenger the radio operator had a multi-channel radio receiver called an AN/ARR-3, which was pre-tuned for the six buoys. When the pattern was laid, the operator would flip through the channels and try to pick up the sounds of the U-boat. The buoy which picked up the strongest sounds was presumably closest to the U-boat, and the Fido would then be dropped somewhere close to the buoy so it could do its thing. The sonobuoys had a cardboard section which would become waterlogged and disintegrate, causing them to sink after a few hours.

 

[Conslaw]

A standard attack on a U-boat was supposed to go something like this:

An Avenger out on patrol would spot a U-boat either visually or on radar. If possible the pilot would work his way round to try and make his initial attack out of the sun, using rockets to try and damage the sub to the point that it couldn't submerge.

If the sub did manage to dive, the Avenger would make a second run and drop both depth charges 'ahead of the swirl', that is at the point where the boat would probably be given its forward motion after diving. The DCs were usually set fairly shallow, say 50ft, the idea being to hit the sub before it managed to get too far away from its initial diving point and before it got too deep.

Then, the Avenger pilot would drop the sonobuoys. Each buoy was identified by a colour, shorthanded as POBRY: purple, orange, blue, red, yellow. The sixth AN/CRT-1 was green, and that was kept as a a backup in case one of the others failed, or if more verification of a contact was needed. Each sonobuoy included a dye marker in the same colour so it was more visible from the air, and transmitted on its own frequency. The Avenger would fly a 'shamrock' pattern like so to drop the buoys in a cruciform shape:
View attachment 534390
In the Avenger the radio operator had a multi-channel radio receiver called an AN/ARR-3, which was pre-tuned for the six buoys. When the pattern was laid, the operator would flip through the channels and try to pick up the sounds of the U-boat. The buoy which picked up the strongest sounds was presumably closest to the U-boat, and the Fido would then be dropped somewhere close to the buoy so it could do its thing. The sonobuoys had a cardboard section which would become waterlogged and disintegrate, causing them to sink after a few hours.

So by "listening" to the buoy, they were looking at signal levels and not listening for the character of the sound? That makes sense in context.

It seems like this type of pattern would be easy to fly in a single-piston-engined plane like the Avenger, but after the war, esp, the anti-submarine warfare role went more and more to larger aircraft. I imagine to fly the same pattern in multi-engined aircraft involved some intense manouvering.