Was the B-29 Superfortress a Failure?

[GrauGeist]

At 22,000lbs, its not as if they can be dropped separately either, is it?

That on top of the penalties you describe, makes its difficult to imagine a sensible operational reason for carrying two Grand Slams. I suspect this was primarily and engineering challenge and a propaganda opportunity.

They were intended to be used against hardened Japanese positions but the war ended before they could be used.

Nothing "propeganda" about it.

 

[EwenS]

Well who knows when they might have become operational with the USAAF given that the Tallboy tests only started in Feb 1945. That photo dates to 1946 IIRC.

For Operation Olympic the RAF Special Missions Wing of Tiger Force was expected to be in place on Okinawa. That comprised 9 and 617 Lancaster quadrons equipped with Tallboy. IIRC proposed targets included the rail tunnel between Kyushu and Honshu completed in 1942.

 

[SplitRz]

They were intended to be used against hardened Japanese positions but the war ended before they could be used.

Nothing "propeganda" about it.

I'm very much aware of the point and purpose of a grand slam bomb.

But why for the sake of Pete carry two? Given they're mounted to either side of the centreline of the aircraft, you'd have to release both at the same time which (along with being potentially catastrophic I would have thought in the case of one hanging-up) seems more than a *just a little* redundant. And if the don't both drop at precisely the same moment, you're also going to throw the trim of the aircraft (to put it mildly!) and put accuracy way off - and that was one of the fundamental merits of the bomb.

Why not carry one, faster and further (and more safely and effectively) ? Because the twin bomb-bays of the B29 demand external carriage under the wings?

Carrying two for a total of 44,000lbs probably brings the B29 down in performance to the range and speed of a Lancaster carrying a tallboy, which, given I've not been previously aware of extensively hardened Japanese positions looks like a massive case of over-egging the pudding.

I think EwenS's post illustrates the issue perfectly:

"Well who knows when they might have become operational with the USAAF given that the Tallboy tests only started in Feb 1945. That photo dates to 1946 IIRC."

To me this smacks of doing something to prove it could be done, but probably after the practicalities of whether it was the best way had ceased to be important.

Its interesting to note that the B36 went on to be tested carrying two T12s. I might have a dig about there to see the whys and wherefores - and hw well it worked out in practice.

 

[pbehn]

This photo that has appeared many times has always puzzled me. With two Grand Slams totalling 44,000lb aboard, just how much fuel was it carrying? And therefore what was its potential range? Were they even filled with explosives or sand ballast or effectively just aerodynamic test shapes?

I dont know the answer but what I do know is it took an age to put the explosive a bucket full at a time in and allow it to cool, according to wiki there were 4,200Kg of explosive in the Grand Slam's 10,200 total weight. Below pics of the bombs before explosive and tail added.
.

 

[Dash119]

Tallboy(12,000lb.) tests - Feb 1945 - In time to be of use during the war.
Grand Slam(22,000lb.) tests - 1946? - Post-war testing?

 

[SplitRz]

Tallboy(12,000lb.) tests - Feb 1945 - In time to be of use during the war.
Grand Slam(22,000lb.) tests - 1946? - Post-war testing?

That's about the measure of it regarding B29 carriage.

Of course both were used operationally by the RAF in Europe.

 

[wuzak]

Could it be that teh B-29 testing two Grand Slams in 1946 had upgraded engines of ~2,800hp, compared to the wartime production B-29s with 2,200hp engines?

That is a 27% increase in power.

 

[EwenS]

Tallboy(12,000lb.) tests - Feb 1945 - In time to be of use during the war.
Grand Slam(22,000lb.) tests - 1946? - Post-war testing?

Read the official report I posted in post #239. Tests STARTED in Feb 1945. The report was dated 30 JUNE 1945 and recommended training of a special unit to drop them and modifications to future aircraft conversions. So no way were they going to be capable of being used by the USAAF in a WW2 ending as historical in Aug 1945. It would have been 1946 before they could have been deployed.

 

[GrauGeist]

I believe development of the U.S. version of the Tallboy, the T-10 (which was further developed into the M121), was started in late 1944 - the VB-13 "Tarzon" started in February 1945.

 

[EwenS]

I believe development of the U.S. version of the Tallboy, the T-10 (which was further developed into the M121), was started in late 1944 - the VB-13 "Tarzon" started in February 1945.

By Oct 1944, US Tallboy monthly production had reached 110, rising to 150 per month by the end of the year with more in 1945. I'm not sure when it started. Production methods were different in the USA. Without US production the squadrons would have run out of bombs to drop.

In total 835 Tallboys were aimed operationally at targets in WW2, plus 8 more dropped accidentally inbound / outbound from the target plus 29 jettisonned or abandoned plus 7 in aircraft shot down without dropping them. Total ependiture 879 plus a few for trials. By just 2 squadrons.

Grand Slam cases were ordered from the USA in Sept 1944 and were expected to start arriving in the UK by the end of the year. After much chopping & changing 200 were ordered in the USA and 25 at home. All were to be filled in Britain.

40 Grand Slams were aimed at targets and 2 jettisoned. Total 42 plus trials weapons. The first operational drop was on 14 March 1945.

 

[GrauGeist]

I recall reading about the U.S. versions of the Tallboy/Grand Slam bombs in Bill Gunston's book (don't remember the title, but I'll search for it) and he covers development of the T-10, T-12, T-14 and their derivatives in pretty good detail.

 

[EwenS]

I recall reading about the U.S. versions of the Tallboy/Grand Slam bombs in Bill Gunston's book (don't remember the title, but I'll search for it) and he covers development of the T-10, T-12, T-14 and their derivatives in pretty good detail.

Not sure how much development was left for the US to do. Construction methods were changed to ease mass production. IIRC British manufacturers had difficulties welding the steel thicknesses involved in making these bombs.

Links to T-10 here.

Bomb, 12000 lb GP, T10

Description British Tail Pistol No. 58 Mk 1 is used at present, but these will eventually be replaced with the Air Arming Fuzes T723, placed 120º apart in the base plate. The fu

bulletpicker.com

A note in the US Bombs and Fuses manual of 1945.
“The T-10 is the American designation for the British 12,000lb D.P. (Deep Penetration) ‘Tallboy’ bomb”

And T-14

Bomb, 22000 lb GP, T14

Description Three British Tail Pistols No. 58 Mk 1 are used at present, but these will eventually be replaced with the Air Arming Fuzes T723, placed in a straight line across th

bulletpicker.com

Again from the linked manual
“The T-14 is American designation for the British 22,000 lb D.P. ‘Grand Slam’

Now the 12,000lb VB-13 Tarzon and the 44,000lb T-12 Cloudmaker were US developments.

Edit:- the T-10 & T-14 even continued to use British fuzes.