B-24 performance, tactics

[islandee]

I have a scenario over Uttaradit, Thailand where eight RAF Liberators were attacking a railroad marshalling yard, their primary target being locomotives. They seem to have been meeting little opposition and were described by locals on the ground as attacking, then circling, and attacking again (repeatedly?) (perhaps carelessly?). The aircraft during a sweep on a target were flying at about 300 feet (stated in reports). I ask these questions because we're trying to locate a crash site that is variously reported as being from three or four miles north of the target to 14 miles south of it:

1. Regardless of potential opposition, I presume that the attacking aircraft would have gone in at maximum speed, ie, about 300 mph, to minimize exposure to potential hostile fire?
2. What was the turning radius of a fully loaded and undamaged B-24 (they were armed for strafing and bombing)?
3. With locomotives as targets, presumably stationary in a yard, it would seem as if attacking them broadside would provide a bigger target than attacking down a track? (Photos of the flak gun taken by crews appear to me to have been taken during approaches perpendicular to the yard.)

What the Liberator crfews weren't aware of was a newly improvised sight and mounting used on a machine gun at the yard. See details of the attack at 06 Oct 1944.

I thank you.

 

[WATU]

I don't know anything about pure bomber performance. I am adding a diagram from a Coastal Command manual that I am confident is early 1945. It shows the path that an aircraft such as a B24 would fly to drop a standard pattern of sonobuoys in an ASW hunt. The aircraft would be flying at about 300 feet and following such a tight course took some skill and concentration. Despite the pilot being the commander of the plane it was found best to allow him to concentrate purely on flying and the navigator effectively took control, issuing instructions to the pilot. Dropping the buoys quickly was essential to catch the escaping U-boat within the listening web. However I do not know what speed it would fly at.

 

[EwenS]

1. Regardless of potential opposition, I presume that the attacking aircraft would have gone in at maximum speed, ie, about 300 mph, to minimize exposure to potential hostile fire?

The speed would be nowhere near 300mph. That was the max speed quoted for a B.VI/B-24J-10-CF like EV940 at 30,000ft. Lower levels = lower speeds. You will find various figures quoted which would all depend on aircraft weight, configuration etc. But at sea level / few hundred feet the figures I have are all around 215-220mph max. In practice maybe a bit less to ensure bombing accuracy.

....They seem to have been meeting little opposition and were described by locals on the ground as attacking, then circling, and attacking again (repeatedly?) (perhaps carelessly?). The aircraft during a sweep on a target were flying at about 300 feet (stated in reports).....

2. What was the turning radius of a fully loaded and undamaged B-24 (they were armed for strafing and bombing)?......

Without aerial opposition the Liberators were free to take their time to maximise the level of destruction they could achieve. So I wouldn't describe their circling as being "carelessly" undertaken. And I think the turning circle of a Liberator is a red herring. More likely time would be taken to circle the target initially, assess it and figure out the best angle from which to attack. Then each aircraft would have intended to set up its bomb run individually (the Thai report talks of them attacking line astern but with no indication of how close they were to each other). Then, having bombed, pull off the target and out of range of any AA fire, rejoining the other circling aircraft until its next turn came up (depending on whether the target was already destroyed or on how many bombs it dropped the first time round, and how many bombs it had left) or until everyone had bombed when they would leave for home, the way they arrived, as a group for mutual defence. It seems to me that EV940 was hit just as it was pulling off the target and beginning its turn (the report talks about it having "steepened its climbing turn to 90" after being hit). Such a steep turn is not normal and suggests the aircraft was out of control by that point. the pilot probably having been killed.

3. With locomotives as targets, presumably stationary in a yard, it would seem as if attacking them broadside would provide a bigger target than attacking down a track? (Photos of the flak gun taken by crews appear to me to have been taken during approaches perpendicular to the yard.)

The reports you link all say that the bombs were dropped "across the target". But they give no indication as to whether that was from an angle perpendicular to the railway line on which the train was sitting, or at an angle approaching that of the railway line or somewhere in between.

Experience in attacking narrow targets that I know of, like submarines in WW2 or since, like an airfield runway in the Falklands, indicates that the best way of maximising the chances of a bomb / depth charge hitting the target is to make the approach run from a shallow angle to the line of the target and dropping a string of bombs down that line of approach. The best illustration of what I mean is from the Black Buck sortie to the Falklands, although they only just succeeded. The highlighted rectangle around the bomb craters gives the line of approach.

I can't find any specific references to RAF methods of attacking railway targets in SEAC in 1944/45 in my library. But looking more closely at the photos taken on the day in Oct 1944 suggests to me an approach at something like 45 degrees to the line of the track, which would fit with my comments above.

Typical bomb loads being carried by both RAF and USAAF Liberators in this period to a target in Thailand would be 10x500lb or 5x1,000lb bombs.

 

[WATU]

I would echo the moments above by EwenS on a diagonal approach. In ASW the operational research teams did a lot of sums around the probability of getting at least one depth charge close enough to a U-boat. A diagonal approach was deemed optimal with the proviso that it was critical to attack the U-boat on the surface or at worst within a few seconds of diving. Speed of attack while the target was visible trumped preferred angles. The pilots were a bit miffed when OR recommended doubling the depth charge spacing to extend the length of the stick to offset persistent pilot optimism on accuracy.

 

[islandee]

Thank you for the corrections and clarifications --- you provide perspective I don't have.

The lower speed involved would appear to reduce the radius for potential crash sites: that would make the one reported position 23 km (14 mi) unlikely.

The report's comment, "steepened its climbing turn to 90" after being hit: at this point, was the plane basically standing on a wingtip, looking like this from end-on: ┤?

 

[EwenS]

The report's comment, "steepened its climbing turn to 90" after being hit: at this point, was the plane basically standing on a wingtip, looking like this from end-on: ┤?

That is what it suggests to me.

 

[islandee]

I thank you.

 

[Greg Boeser]

Generally not an attitude within the aircraft's design limits.

 

[islandee]

To close this topic: we located the crash site last week: it is about 5km (3mi) almost directly north of the targeted Uttaradit Railway Station. We got lucky in finding in the on-line description of a nearby Uttaradit temple the comment that an aluminum container fashioned from a piece of wing of a plane that crashed on the date in question was on display. With that we were able to find people in the area that knew of the crash. No other aircraft has crashed near Uttaradit Town. The aircraft was RAF Liberator EV940 which crashed at Mon Din Daeng, now on the northern outskirts of an expanding Uttaradit Town.

 

[Thumpalumpacus]

As a follow-up: when attacking a surface target with a long, narrow profile, attacking along the length will reduce timing issues associated with off-axis attacks. For something like a train you'd need to hit fairly close, and you're more likely to be close with a string of bombs (or even just a couple) if you're attacking along the length of the train rather than across its beam. Timing matters a bit less then.

It's the same reason dive-bombers preferred attacking ships lengthwise rather than abeam. Even if you don't hit directly, you're likely to e closer, and if your timing is off a hair, your target is long enough that a hit may still land.