The Lancaster as a potential nuclear bomber in 1945

[Dash119]

There's no edit from #2 engine start, to #3 engine start.

The starting order in the video is 3-4-2-1. So in that sense you are correct, there is no edit between turning 4 and turning 2. However, there are edits between turning 3 and turning 4, between turning 2 and turning 1, and during the removal of the start cart. Frankly, I think it is possible the Lancaster could carry Fat Man, but not while dragging the start cart...

 

[GrauGeist]

Says the guy who claimed 20% fuel burn prior to TO... and couldn't see the obvious error in that statement.

You have absolutely ZERO idea how much fuel is consumed under full power in an overload condition, ZERO.
Additionally, you have provided absolutely no other credible data that would indicate otherwise, so you really should quite while you're ahead.

In regards to this idiotic fantasy that a Lancaster could nuke Japan - it didn't.
End of story.

 

[RCAFson]

You have absolutely ZERO idea how much fuel is consumed under full power in an overload condition, ZERO.
Additionally, you have provided absolutely no other credible data that would indicate otherwise, so you really should quite while you're ahead.

In regards to this idiotic fantasy that a Lancaster could nuke Japan - it didn't.
End of story.

From the B-29 Pilot's and flight engineers training manual...(page 107)

"INFLIGHT OPERATION
Takeoff
You begin to use Cruise Control as soon as
the engines are started. However, so little fuel
is used during ground operations preceding
takeoff that the fuel flow meters will not regis
ter. Therefore, although fuel flow meter read
ings should normally be used for accurate com
putation of fuel consumption, it is a practical
expedient in the case of ground operation to
assume a fuel flow of 3 gallons per minute and
20 gallons per minute for takeoff power, until
initial climb settings are established.
The time lapse between engine starting and
the beginning of the initial climb after takeoff
is small—seldom greater than 15 minutes. Expe
rience has shown that it's safe to predict a fuel
consumption of approximately 100 gallons for
this series of operations."

 

[buffnut453]

Putting it (very) simply, drag is about the shape of the object, its physical size and frontal area and how it moves through the air. Other complexities include the viscosity of the air, the speed of the object etc. With an increase in speed comes an increase in drag, which correspondingly reduces acceleration and increases workload to maintain specific values. Basically, the faster you go, the greater the amount of resistant force on the aircraft and therefore the greater the amount of work required to maintain those values. Acceleration decreases and the engines have to work harder, which means a higher fuel consumption as the aircraft accelerates on take off and into establishing the climb. With aircraft that are heavily laden, around 20 percent of their total fuel load is used just to get off the runway (a value roughly calculated in a class exercise using a 747, its total fuel load and its MTOW versus its speeds and acceleration).

Yes, I'm familiar with the "speed squared law" as it applies to drag, as well as the different types of drag: form, induced, friction, parasitic.

By even fitting a streamlined bulge to the underside covering the Fat Man would be like increasing the frontal area of the Lancaster by nearly twice its value since the bomb is almost the same diameter as the aircraft.

How did you work out that carrying a Fat Man would double the frontal area of a Lancaster? Yes, the bomb is almost the same diameter as the Lanc...but the Lanc fuselage was racetrack-shaped and had a depth of 8ft 2in. If we add the canopy onto that (let's say 8in which is not unreasonable), then you have an (approximate) flat-sided oval of height 9ft and width 5ft.

Also bear in mind that 50% of the Fat Man will fit into the standard Lanc bomb bay, which means only 50% of the bomb is exposed to the airstream. This is based on the fact that the 4000lb Cookie had a diameter of 30in and that fitted into the Lanc bomb bay without bulged doors...although there's an assumption that any Fat Man bomb shackle didn't add more distance between the weapon and the bomb bay ceiling than was the case for the 4000lb Cookie.

All of the this ignores other sources of form drag...minor things like the wings, engines, propellers, tail surfaces etc. Given the above, carrying a Fat Man wouldn't come near to doubling the frontal area of a Lancaster.

Oh and Mark, as an engineer as you've pointed out, since you don't know the exact content of what Ramsey revealed to Chadwick, it's best not to presume until you do.

I'm not presuming. I'm working on a balance of probabilities. Another poster commented that "of course Chadwick would say the Lanc could carry the weapon." I'm afraid I just don't see that as a realistic scenario. You have one engineer, Ramsey, asking another engineer, Chadwick, an engineering question. Even if Chadwick did make the claim without doing calculations, would Ramsey have accepted it...as an engineer? The far more likely scenario is that Chadwick did some rough calculations, based on data provided and some agreed assumptions, and that Chadwick confirmed, to Ramsey's satisfaction, that the statement about the Lancaster's ability was sufficiently solid.

In all reality, we'll probably never know exactly what information was exchanged. It's highly likely details of bomb size and weight were provided verbally, that any calculations were done pretty quickly and then immediately destroyed. I simply find the idea that 2 engineers would discuss an engineering problem without diving into the mathematics somewhat ridiculous.

For all the criticism of the "Lancaster Unicorn" (and, trust me, I fully accept that the Lancaster would need extensive modifications and acknowledge that performance would absolutely be affected), let's not swing the other way in seeking for nonsensical arguments just to prove a point. I think arguments about what information Chadwick may or may not have obtained fall into that category and can never be positively resolved because the records likely don't exist. Weight clearly wasn't an issue so the only question is whether an adequate carrying shackle could be designed to accommodate Fat Man's girth given the Lancaster's fuselage width. We're into a balance of probabilities but, ultimately, the Lancaster's chief designer said the weapon could be carried and, unless there's evidence that Chadwick ever was economical with the truth, he should get the benefit of the doubt.

We also need to bear in mind that when Chadwick was asked the question, the targets for the weapons hadn't been selected. We do need to be careful of not applying the retrospectroscope and automatically applying the same Silverplate mission profile to the Lancaster. Again, with no B-29 in the mix, the decision calculus changes fundamentally. However, there were engineering solutions already in play as early as September 1944 to allow Lancasters to reach Japan.

At the Quebec Conference in September 1944, Churchill proposed to transfer a force of forty bomber squadrons to the Far East, of which 20 would act as airborne tankers. The tankers would use the Cobham AAR technique had been successfully trialed in 1935 - this was proven, rather than emerging, technology. Frankly, the last few pages of discussion on how much fuel gets burned during engine start-up and take-off are irrelevant. Tiger Force planned to use AAR so why overload a nuke-carrying aircraft on the ground? Much safer to keep the weight down for take-off then refuel in the air.

Roosevelt accepted Churchill's offer because, at that time, it was still unclear who long the war would continue. Ultimately, the RAF bombers weren't needed because the US was able to roll over Japanese defences and muster sufficient combat power on its own. However, if the B-29 programme had failed, Lancaster-based options were certainly available. It would have involved more aircraft and certainly would have been more complicated, with consequent increase in risk. However, I have no doubt it could have been done...had it been needed.

For me, there are 2 critical unanswered questions regarding the Lancaster's ability to successfully complete a nuclear weapon mission, and both are related to safe release of the weapon:
1. Could the Lancaster have attained sufficient altitude to drop the weapon?
2. Could the Lancaster have escaped the target area sufficiently quickly to protect the crew from the blast?

 

[DerAdlerIstGelandet]

Final warning. Tone down the snarkiness. Everyome.

 

[FLYBOYJ]

The Lancaster has a Flight Engineer to assist, along with the Navigator.

Not the same as having a dedicated, trained and qualified co-pilot.

 

[Peter Gunn]

This is probably apropos of nothing but in regards to fuel consumption etc. - for the Lancaster I have no clue but...

I got a digital copy of my uncle's diary he kept whilst on Guam, in it he mentions that a B-29 on an Empire strike did not start engines until 6 minutes before the ship took off, no engine run ups prior to takeoff like say a B-17. The flight engineer would do those checks in the first one-third of the takeoff run to prevent excessive cylinder head temperatures. Also mentioned were three "power settings", power setting one was takeoff followed by power setting two once they were airborne until he mentions airspeed 225 at which time they went to power setting three.

Not much data on the fuel consumption on the ground except one entry that seems to corroborate post 563 in that fuel flow was "minimal" until they really got going down the runway and then initial climb rate.

Now I admit, that's a fully loaded "Stripper" B-29 on a standard Empire strike, things may have been totally different with Enola Gay.

 

[FLYBOYJ]

1. Could the Lancaster have attained sufficient altitude to drop the weapon?
2. Could the Lancaster have escaped the target area sufficiently quickly to protect the crew from the blast?

At the end of the day I'd say yes to both but would have reservations about #2.

I did some rough calculations and come up with a ground fuel burn between 90 and 100 gallons for start up, taxi and take off, roughly 2 - 5% of the fuel load

 

[RCAFson]

As best I can determine, Guy Gibson, on the Dam Buster raid started engines at 2125 and TO at 2130.

Bricknell's The Dambusters states 2125 for Gibson's engine start and Falconer, The Dam Buster's Story states TO at 2130.

 

[FLYBOYJ]

As best I can determine, Guy Gibson, on the Dam Buster raid started engines at 2125 and TO at 2130.

Bricknell's The Dambusters states 2125 for Gibson's engine start and Falconer, The Dam Buster's Story states TO at 2130.

Well if if this time table is correct, Gibson managed to get the oil temp to 15C, oil Pres 90 lb/sq inch and the coolant to 60C (quite do-able) as indicted in the pilot's notes. I also believe that for all Merlins, RR recommended a 2 to 4 minute warm up (of course with fighters on alert, this all went out the window). If you're taxiing down an 8000' runway, that alone could take 5 minutes unless you're taxiing like a bat out of hell.

 

[RCAFson]

Well if if this time table is correct, Gibson managed to get the oil temp to 15C, oil Pres 90 lb/sq inch and the coolant to 60C (quite do-able) as indicted in the pilot's notes. I also believe that for all Merlins, RR recommended a 2 to 4 minute warm up (of course with fighters on alert, this all went out the window). If you're taxiing down an 8000' runway, that alone could take 5 minutes unless you're taxiing like a bat out of hell.

It's in agreement with post 567.

 

[FLYBOYJ]

It's in agreement with post 567.

Yes and no - I believe those occurrences happened but they are also out of operational norms for those aircraft. IMO there was probably an operational requirement to "light up and go" (risk of an enemy airstike at takeoff?) and because it more than likely deviated from the flight manual, at a minimum had to be approved by the squadron commander.

 

[ThomasP]

I do not know if this will help, but the following is from the Hiroshima mission record:

0112: Trucks pick up the crews of the two observation planes, The Great Artiste and Necessary Evil.
0115: A truck picks up the crew of the Enola Gay.
0227: Enola Gay's engines are started. [ie all 4 are running]
0235: Enola Gay arrives at her takeoff position on the runway.
0245: Enola Gay begins takeoff roll.
[Enola Gay lifts off after using almost all of the 8400 feet of runway, this would take about 80-90 seconds?]
0247: The Great Artiste takes off.
0249: Necessary Evil takes off.

My comments in [ ].

 

[RCAFson]

I do not know if this will help, but the following is from the Hiroshima mission record:

0112: Trucks pick up the crews of the two observation planes, The Great Artiste and Necessary Evil.
0115: A truck picks up the crew of the Enola Gay.
0227: Enola Gay's engines are started. [ie all 4 are running]
0235: Enola Gay arrives at her takeoff position on the runway.
0245: Enola Gay begins takeoff roll.
[Enola Gay lifts off after using almost all of the 8400 feet of runway, this would take about 80-90 seconds?]
0247: The Great Artiste takes off.
0249: Necessary Evil takes off.

My comments in [ ].

OK, so start up was at 0227 and take off was at ~0246. Lets call it 20min. According to the B-29 manual we can expect to use 3USG/minute during warmup and and 20USG/min for TO. Let's go with 18min for warm up and 2 minutes for TO (full power) = 18 x 3USG and 2 X 20USG = 94USG out of ~8000USG total or about 1.2% of total fuel.

 

[FLYBOYJ]

OK, so start up was at 0227 and take off was at ~0246. Lets call it 20min. According to the B-29 manual we can expect to use 3USG/minute during warmup and and 20USG/min for TO. Let's go with 18min for warm up and 2 minutes for TO (full power) = 18 x 3USG and 2 X 20USG = 94USG out of ~8000USG total or about 1.2% of total fuel.

And I can agree with these fuel numbers but if want to take the times noted to the bank, there is a 10 minute pause on the runway before he took off, IMO to do ground runs, Mag checks and other pre-takeoff tasks. I find this all SOP in lieu of firing up engines and launching into the air within 5 minutes.

 

[ThomasP]

In the Nagasaki mission report it mentions the pilots doing 'engine checks' during the time in question.

 

[Conslaw]

Why are we even arguing about the Lancaster's specific fuel consumption? As was discussed early in this thread, the contingent British strategy for using the Lancaster involved in-air refueling. Testing showed that it could work. If the Lancaster had to be used, the crews and technical people would have had several months at least to work on the details and protocols. You could refuel the plane on the way out and on the way back, and even if you missed the rendezvous on the way back, the mission was important enough to sacrifice the aircraft anyway.

 

[FLYBOYJ]

Why are we even arguing about the Lancaster's specific fuel consumption?

Because there are some who believe that the Lancaster "could have" completed this mission without aerial refueling.

 

[nuuumannn]

How did you work out that carrying a Fat Man would double the frontal area of a Lancaster?

I didn't work it out, Mark, re-read what I said - it's almost the same diameter, NOT SHAPE, SIZE, PROFILE etc, but diameter, the bomb is around five feet, the Lancaster fuselage width is roughly the same at the bomb bay.

Also bear in mind that 50% of the Fat Man will fit into the standard Lanc bomb bay, which means only 50% of the bomb is exposed to the airstream.

Only if you remove the fins, which are 1.5m square by 1.5 metre square. That won't fit in the bomb bay, so it has to be suspended below the aircraft.

In all reality, we'll probably never know exactly what information was exchanged. It's highly likely details of bomb size and weight were provided verbally, that any calculations were done pretty quickly and then immediately destroyed. I simply find the idea that 2 engineers would discuss an engineering problem without diving into the mathematics somewhat ridiculous.

Again, you are missing my point. Only if we know exactly what was exchanged can we be absolutely certain of that. Anything else is merely presumption, Mark. I'm sorry, but I'm not working on presumption, but evidence and what is physically known and there is no evidence that Chadwick said the Lancaster could carry Fat Man. None. He was offered shapes and descriptions and even the sources provided here state that he was not advised that these were nuclear weapons.

Why are we even arguing about the Lancaster's specific fuel consumption? As was discussed early in this thread, the contingent British strategy for using the Lancaster involved in-air refueling. Testing showed that it could work. If the Lancaster had to be used, the crews and technical people would have had several months at least to work on the details and protocols. You could refuel the plane on the way out and on the way back, and even if you missed the rendezvous on the way back, the mission was important enough to sacrifice the aircraft anyway.

No RAF equipped Lancaster was capable of in-flight refuelling by mid 1945 in reality, although this presumption of this raid as dreamed up on this thread suspends reality, but it could not have carried it out. Lancasters had carried out IFR in trials in 1944, but the RAF was still a wee while before it had operational capability.

For the fictionalists here, there is what might equate to a solution. I recently found out that Avro had drawn up plans for Manchesters to be converted into IFR tankers and receivers, so Avro were thinking about extending the range of its bombers at least. Perhaps RCAFson can add a fleet of Manchester tankers to his Lancaster VIs and Silverplate Lincolns, but of course these are not needed because both types can carry out the raid without IFR.

 

[nuuumannn]

Says the guy who claimed 20% fuel burn prior to TO... and couldn't see the obvious error in that statement.

Says the guy who STILL hasn't read and acknowledged why I posted it DESPITE it having been pointed out to him - I'm seeing a pattern here - you only accept your opinion and no one else's even when they repeat themselves.

The fact is that an Lancaster VI can fly either of the historical missions, using a Tinian->target->Okinawa flight plan.

Historically, no it can't. It was not in service in 1945 for starters, and it had neither the range nor the reliability and the final reason was that it wasn't American and Arnold had emphatically stated that the B-29 was going to be used, so, yeah, nah.

In your fictional scenario however, probably. Anything is possible in that world and as long as we accept that, we are fine with it.