Lancaster as an escorted, daylight bomber ala B-17/24?

33k in the air · Apr 20, 2021

buffnut453 said:
Thanks for the clarification on B-17 bomb loads. I'll admit I seem to have slightly underestimated the weight of ordnance. Regardless, the details you provided still destroy the myth that the B-17 could carry 10,000lbs to Berlin under operational conditions.

The maximum weight of internal load for the B-17 was 12,800 lbs consisting of 8 x 1,600 AP bombs. Needless to say, armor piercing bombs are of limited value in attacking industrial sites. According to Roger Freeman's works on the 8th AF, the external racks on the B-17 were only used on a few missions. The additional drag and handling penalties associated with the external ordnance was judged to outweigh the benefit of the additional striking power.

33k in the air · Apr 20, 2021

Milosh said:
This should give a general indication what other bomber carried, 303rd BG Combat Missions and Reports

This is one of the (few, unfortunately) sites with USAAF bomb load data. Here are some others I've come across. Some of these sites have additional material, such as the actual mission reports showing flight paths, mission details, etc.

91st Bomb Group (B-17) - download the "Dailies" PDF files for the three squadrons listed from the menu on the left side
398th Bomb Group (B-17) - details for only one specific aircraft
451st Bomb Group (B-24)
458th Bomb Group (B-24)

320th Bomb Group (B-26, MTO)
340th Bomb Group (B-25, MTO)
416th Bomb Group (A-20 and A-26)

fastmongrel · Apr 20, 2021

Many of the Bomb weights were actually nominal weights. The actual weight could be quite a bit less. The RAF MkI 4,000lb Cookie HC blast bomb actual weight was 3,930lbs.

nuuumannn · Apr 20, 2021

RCAFson said:
A photo caption from page 98, of Mason's The Secret Years:

"136 Left: Halifax II V9985
in February 1943 with
swollen bomb doors to
accommodate the 8,000 lb
'Cookie' bomb.

P. 96 in my copy. The bulged bomb doors were not often used operationally on the Halifax; I dunno if they entered operational service at all, most likely because of the nature of the modification. The Halifax bomb doors were significantly more complex than the Lancaster's. The latter had two doors, one each side, the former had eight, four each side. The Halifax doors were divided both longitudinally and vertically. There was an upslope in the contour of the lower fuselage that warranted the doors to be segmented with two distinct sections, but each of those comprised four doors apiece. upper and lower. The upper doors on opening slid against the outer fuselage side, but the lower, curved doors slid inside the bomb bay to sit against the inner wall. Fitting bulged doors was no mean feat because of this; they would have taken up valuable space in the bomb bay. How the experimental bulged doors worked I don't know, but they weren't put into common use - Halifaxes in service had to carry the big diameter bombs with their doors open, as per the picture on an earlier page. This induced drag and lowered the type's performance. The Halifax II Series Ia was the first of the type modified to carry the 4,000 lb 'Cookie' with the doors left hanging in the breeze, in 1942.

nuuumannn · Apr 20, 2021

Koopernic said:
A second problem with the Mk II was that it could only carry 14,000 lbs of bombs, compared to the 18,000 of the Mk I.

The Lanc II gets a bit of a bad rap because of its lower altitude, but in fairness, actual test data by the A&AEE shows that yes, it did have lower altitude at which its cruise speed was at its most efficient, different types of Hercules engines fitted redressed the balance somewhat compared to the Halifax at least. The Lanc II had a faster rate of climb and better handling than the Merlin engined Lanc Mk.I and maintenance-wise required less time spent on its engines. On introduction into service the Lanc II also had a greater maximum take-off weight compared to the standard Lancaster I (unmodified for carrying the special ordnance, which required a raft of modifications and made the type a dog to fly). During trials the main issues encountered were flame damping and inadequate cooling of the engines. The Lanc II with the Herc VI had a service ceiling of 21,000 ft and a maximum speed of 273 mph during trials, but with the Herc XVI its ceiling was less, but climb was quicker and performance marginally increased. The Lanc III performance was superior still.

33k in the air · Apr 20, 2021

fastmongrel said:
Many of the Bomb weights were actually nominal weights. The actual weight could be quite a bit less. The RAF MkI 4,000lb Cookie HC blast bomb actual weight was 3,930lbs.

Indeed. Even a different explosive filling can change the actual bomb weight. I've downloaded several munitions documents and they all list slightly different actual weights even for the same bomb type. (I presume there must be some degree of natural variation.)

33k in the air · Apr 20, 2021

nuuumannn said:
P. 96 in my copy. The bulged bomb doors were not often used operationally on the Halifax; I dunno if they entered operational service at all, most likely because of the nature of the modification. The Halifax bomb doors were significantly more complex than the Lancaster's.

The Halifax also had wing bomb bays, although these were limited to a maximum bomb size of 500 lbs. (A total of 6 x 500 lb bombs could be carried in the wing bomb bays.)

nuuumannn · Apr 20, 2021

33k in the air said:
The Halifax also had wing bomb bays, although these were limited to a maximum bomb size of 500 lbs. (A total of 6 x 500 lb bombs could be carried in the wing bomb bays.)

Over time these weren't so commonly used owing to the problem suffered from the doors not sitting flush with the lower wing surfaces and sagging in the slip stream in flight, which caused drag. Again, it wasn't until the Halifax II Series Ia that this was cured. They could only carry 500 pounders.

The early Merlin engined Halifaxes suffered from poorer than predicted performance and load-carrying capability caused by high drag and heavier than predicted weights, which affected operations.

JDCAVE · Apr 20, 2021

33k in the air said:
The Halifax also had wing bomb bays, although these were limited to a maximum bomb size of 500 lbs. (A total of 6 x 500 lb bombs could be carried in the wing bomb bays.)

I sent you a pm on Petrol Loads.

Jim

JDCAVE · Apr 21, 2021

33k in the air said:
I read somewhere that eventually about one-third of the Lancasters in Bomber Command were fitted with such bulged bomb bay doors. Does anyone have any hard data on the squadrons which fielded such modified Lancasters and the numbers involved?

Some of the early Lancaster X's delivered to 419 Squadron had bulged doors when delivered however I don't think these a/c ever carried any of the 8,000 bombs. Later I think they switched these doors out. Certainly photos reveal slimmer a/c. I'm not certain but wonder if the bulged doors affected the signal from the H2S. Also, I had heard these doors were plywood, but cannot confirm. I'll drag out the colour photo of KB.712. Dad flew a "sea-search" on this a/c October 16,1944. Here she is, looking a little plump!

33k in the air · Apr 21, 2021

JDCAVE said:
Some of the early Lancaster X's delivered to 419 Squadron had bulged doors when delivered however I don't think these a/c ever carried any of the 8,000 bombs. Later I think they switched these doors out.

The Bomber Command Museum of Canada has a page with information on all the Lancaster X's which were built: Canadian-built Avro Lancasters

According to that, the first 155 were constructed with the bulged bomb bay doors (KB700-854) and the option for the fitting of the mid-under turret (not sure if was fitted as standard armament). Starting with KB855, normal bomb bay doors were fitted, and the dorsal turret fitted was a U.S. Martin model armed with two .50-cal machine guns. (This heavier turret necessitated it being moved forward to just behind the trailing edge of the wings.)

JDCAVE said:
I'm not certain but wonder if the bulged doors affected the signal from the H2S.

That's what I've read. Bulged bomb bays interfered with H2S, so it wasn't fitted on such aircraft.

JDCAVE said:
I sent you a pm on Petrol Loads.

I knew there was something I had forgotten to do today! Yes, I saw that, thanks. Will send a reply tomorrow.

JDCAVE · Apr 21, 2021

33k in the air said:
That's what I've read. Bulged bomb bays interfered with H2S, so it wasn't fitted on such aircraft.

But nearly all of these aircraft carried H2S. So did they switch these door out?

jim

33k in the air · Apr 21, 2021

JDCAVE said:
But nearly all of these aircraft carried H2S. So did they switch these door out?

I would presume so, but I don't know for certain. I've only seen general comments on the degree to which H2S was fitted to Bomber Command aircraft; another area where it would be great to have hard data on the numbers of aircraft in each squadron so equipped on a monthly basis.

Some of the Halifax squadrons in 6 Group had the mid-under Preston-Green turret fitted; these turrets were eventually removed and H2S mounted instead.

Greg Boeser · Apr 21, 2021

pbehn said:
Without an escort anything in broad daylight was unsustainable, the first use of B-26 in Netherlands lost all aircraft. T

That's a LIE! It was the second mission. Everybody got back the first time. But then they thought it would be a good idea to go back the next day...

ThomasP · Apr 21, 2021

It looks like somewhere between 10% and 30% of Lancasters were fitted with the bulged doors for the 38" diameter bombs.

". . . this involved constructing a bulge in the bomb doors. It was later found out that this interfered with the installation of radar equipment so only 10% of Lancaster's were to be modified to carry the 8000 lb high capacity bomb, but by this time the material for the doors had already been ordered so a compromise of 30% was made."

There were ~1150x 8000 lb HC bombs produced beginning with 32 delivered to BC in 1942

There were only 170x 12,000 lb HC bombs produced from 1944.

AVIA 46/285, AVIA 46/163

"http://www.wwiiequipment.com/index.php"

Thumpalumpacus · Apr 22, 2021

fastmongrel said:
Many of the Bomb weights were actually nominal weights. The actual weight could be quite a bit less. The RAF MkI 4,000lb Cookie HC blast bomb actual weight was 3,930lbs.

Seventy pounds here, seventy pounds there, pretty soon we're talking real sterling.

JDCAVE · Apr 23, 2021

Concerning modifications of the Lancaster to accommodate the Grand Slam: Transcript of Syd Grimes WOp with 617 Squadron:

"AG: They checked me in they thought I had better be legitimate. So I, I was with 617 from the September '44 through 'til April 1945. We had been flying the Barnes Wallis Tall Boy bomb which was 12000 pounds. And then he came up with a much bigger invention, the Grand Slam which was 22000 pounds. In order to accommodate the big bomb they had to take the bomb doors off, and they took the mid upper turret off, and they took all the armour plating out. They really did a modified Lancaster which only took a crew of five. Took all the wireless equipment out except for a VHF transmitter, RT. So I was surplus so I said to the flight commander. ' I have only got three more trips to do can I fly in the astrodome as a fighter observer or something like that?' He said. 'Under no circumstances, we are trying to find reasons for loosing weight.' And he said. 'You want to go and fly.' He wouldn't let me and the crew got shot down on the very next trip. So they got hit by and anti aircraft shell on the port wing and it shot it completely away. So they were on the bombing run at that time which was the dicey part of the trip. Because eh, the special bomb sight that we had, we had to fly straight and level. It was gyroscopically controlled, so you had to fly very accurately with height, speed and all the outside temperatures. And all that kind of thing which you fed in to this computer. So they was, the squadron flew in what was called a gaggle. A geese gaggle you know? The way that they fly in the sky."

Interview with Syd Grimes · IBCC Digital Archive (lincoln.ac.uk)

For clarification, the ORB records that PD.117 carried a Tall Boy bomb to the target Dreys [sic, actually Dreye] hit by flak in the target area and exploded on the ground.

Jim

pbehn · Apr 24, 2021

33k in the air said:
Note that the distance versus load tradeoff applies not only to aircraft but to the individual bomber groups. 6 Group (RCAF), being the furthest north of all the Bomber Command groups, was generally flying the longest distances regardless of the particular aircraft type used by it.

Reading this on the Halifax, the most produced MkIII version may have been on par with a Lancaster but it only started being produced in late 1943 issued to squadrons and operational early 1944, but by then there were a huge number of jobs that needed doing and squadrons that needed old planes to be replaced. This gives an idea of the problems with the Halifax early in its life Halifax Bomber

Koopernic · Apr 25, 2021

Milosh said:
And didn't give the reference source, again.

Everyone is saying the Halifax is crap. When I ask why I get crickets. When I suggest the inferiority of the Hercules (high drag, poor altitude performance) I hear crickets. and folks attack me for no quoting a mainstream internet source. I'm not writing academic papers.

Why did the Halifax have inferior performance.

fastmongrel · Apr 25, 2021

It might just be that the Lancaster was so good, sometimes a sweet spot is hit with a design that's just better than any other similar aircraft. Without the Lancaster the Halifax might have been known as the best night bomber of the war (apart from the B29).

Lancaster as an escorted, daylight bomber ala B-17/24?

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