Aerodynamics: B-17 vs Avro Lancaster

[stona]

The 'Usual Bomb Load' for British bombers, including of course the Lancaster, was worked out from tables published by the Command taking all operational factors into account. Most obviously the amount of fuel (and reserve) carried might affect the weight of ordnance carried.
It is quite true that 12,000lbs was a typical load for the Lancaster.
When actual operational bomb loads were examined in late 1943 all sorts of variations were discovered between Groups and these had to be explained. I'll give a few examples. The usable load for the Lancaster IIs of Nos. 3 and 6 Groups was 1500lbs less than for the Lancaster Is of Nos. 1 and 5 Groups because the empty weight of the Lancaster II was higher. The Mk II also had a higher fuel consumption, requiring more fuel against bomb load in the tables, and 6 Groups bases were further from Germany.
All Groups tried to maximise their efforts. The investigation revealed that 1 and 5 Groups' aircraft were 'occasionally' overloaded and that 6 Group's were 'often overloaded', notably on long range raids when the high fuel requirements might otherwise reduce the bomb lift of the Group.
An ongoing shortage of SBCs meant that many aircraft did take off with less than the maximum bomb loads. This led to the recommendation I have mentioned elsewhere that
"on the first night after a blank night [without operations] Lancasters should carry as many SBCs as are needed to make up the permitted weight and they should not be withheld to cover the possibility of another operation the following night, since the number of occasions on which operations occur on consecutive nights is not sufficiently high to justify any reduction in efficiency on the first night."
These and many other factors mean that the average bomb load carried by the Lancaster throughout the war was slightly less than a usual load of 12,000lbs. The average load, weighted by various factors, was 9,186lbs.
Cheers
Steve

 

[wuzak]

These and many other factors mean that the average bomb load carried by the Lancaster throughout the war was slightly less than a usual load of 12,000lbs. The average load, weighted by various factors, was 9,186lbs.

Does that including mining operations Steve?

I guess it also skewed by missions that were at the edge of the Lancaster's range, where a full bomb load could not be carried so that all possible fuel could be.

 

[stona]

Not mining, but long range operations and PFF operations (certainly of 5 Group, not clear about 8 Group). The loads carried by path finder aircraft were largely pyrotechnic. Typical loads were 6 x 1000lb TIs and 4 x 500lb bombs (8000lbs) or 4 x 1000lb Tis and 4 x 1000lb bombs (8000lbs again). Space not weight was the issue with the TIs which were fitted with a long tail (as seen on the original 1000lb HE bombs) to give them stability and accuracy. In any case, both loads are well below the average.
Those are a couple of the more obvious factors that weight the average. Lancasters could and did fly with a 12,000lb load as a matter of course.

The Lancaster could carry all of these in various combinations (or alone).

Enough to give a B-17 armourer palpitations

Cheers

Steve

 

[wuzak]

Interesting that there is a 2000lb MC on the left, next to the 1900lb GP bomb. I didn't think such a device existed.

I looks similar in diameter to the 500lb MC bomb in the foreground. But it doesn't look big compared to the 1000lb MC. Maybe mislabelled? Possibly the 2000lb AP?

As for target indicators, did the Lancaster use the 250lb TI? The Mosquitoes used the 250lb TI predominately because they couldn't fit the 1000lb TI (same size as 1000lb MC) until the bulged bomb bay was fitted, and then they could carry one initially and then two later on.

Of the 10 bombs there I believe the B-17 could only carry 4 of them internally. That'd be the 500lb MC, 1000lb MC, 1900lb GP and "2000lb MC".

 

[wuzak]

Oh, I missed the 40lb GP bomb in the guy's hand.

 

[stona]

Harris wrote that though the 250lb TI typically scattered its pyrotechnic candles over an area of about 100 yards diametre, the Germans attempts to divert attackers from the correct aiming point became better and this was insufficient. The 1000lb TI was developed to "swamp all such attempts at 'spoofing' by employing markers in such quantity or of such size that no mistake should be possible." It was specifically designed in order "more economically to fill the Lancaster bomb stowages." This bomb also trebled the amount of candles carried on each bomb station.
It seems that the Lancaster could and did carry the smaller TI, but that later the larger one was preferred.
The first 250lb TIs were used in January 1943, I would guess that the larger 1000lb TI was developed some months later. Harris doesn't give a date for the first use of the larger TI, it might turn up somewhere else, but I don't remember reading this information before.
Cheers
Steve

 

[tomo pauk]

Thank, you people.
The pic of the different bombs with people between them is simply great.

 

[nuuumannn]

Can I ask, what was funny about this post?

The whole premise of it

Yes, Tomo, great picture.

 

[Icorps1970]

I once talked to a 8th AF B17 pilot. He said some interesting things. One that he refused to fly a B24 since he did not think it was safe. Another was that the B17s, in real life, were so slow that and Lancaster could not fly with their formations. Also said they lied to us and to the American Civilians about the losses they encurred. True? I dunno. I was not there. Why would be lie?

 

[Greyman]

I have nothing for the Fortress, unfortunately.

Drag Analysis - Lancaster I

Drag as % of Total Profile Drag

Profile Drag​

Wing - 25.5​

Body (excl. cabin) - 7.7​

Tail - 6.4​

Power Plant - 23.6​

Guns & Turrets - 12.6​

Radio - 1.1​

Roughness (excl. fit of panels) - 7.1​

Misc. - 10.5​

Leaks & Unaccounted - 5.6​

Gross Wing Area - 1297 sq. ft.
Total Profile Drag (DO 100 (lb at 100 fps) - 467
CDO - 0.0302
Approximate Total Wetted Area - 4500

 

[pbehn]

P pbehn

Post #6: 9/10/16
the Lanc needed complete air superiority for daylight raids it had insufficient defensive armament.


I assume this is mostly due to caliber?

s.

Not really calibre alone, very vulnerable to beam attack and no protection at all from below.

 

[Zipper730]

Not really calibre alone, very vulnerable to beam attack and no protection at all from below.

The Lancaster ironically did have a ventral turret, but they never installed it or some reason.

 

[pbehn]

The Lancaster ironically did have a ventral turret, but they never installed it or some reason.

Because it didn't work. aiming was done through a periscope, it could shoot down something that flew in formation long enough to be shot down. The RAF was already committed to night raids when the Lanc came into service. There was at least one raid in daylight by Lancasters and it was a disaster.

 

[Zipper730]

Because it didn't work. aiming was done through a periscope

So they didn't use the ball-turret like we did with some guy crawled up in side it?

 

[pbehn]

So they didn't use the ball-turret like we did with some guy crawled up in side it?

No it was much smaller I cant find a non copyrighted image but the net throws up a lot.

 

[Zipper730]

No it was much smaller I cant find a non copyrighted image but the net throws up a lot.

That explains a whole lot...

 

[pbehn]

That explains a whole lot...

Later it was the same place as the "village inn" radar warning equipment was installed.

 

[stona]

The Manchester originally had a retractable ventral turret, the 'low drag mid lower turret'. It's hard to spot on the ground (retracted), but I have a picture of L7282 of No. 207 Squadron in which it is clearly visible. I think it is an FN 21A. It seems to have been deleted fairly early.

The FN 64 ventral turret seems to have made it into some early Mk I Lancasters but was soon abandoned. Interestingly there is a picture of Mk I, R5727, complete with a mid lower turret, an aircraft that was sent to Canada as a pattern aircraft. It never went on operations and was converted to a transport aircraft by Victory Aircraft (Canada)

Later, I don't believe any Lancasters had such a turret, as opposed to a ventral gun position. Once the H2S radar installation became standard across the command there was no possibility or retro-fitting a ventral turret anyway.

Cheers

Steve

 

[Glider]

Its worth remembering that the B24's in Europe had their ball turrets removed around May in 1944 so there wasn't much difference in the ventral defence and they clearly flew daylight missions.

 

[Greyman]

Not really calibre alone, very vulnerable to beam attack and no protection at all from below.

The Lancaster had reasonable beam protection (calibre notwithstanding). The front and rear turrets could turn 90 and 92 degrees to either side, respectively. Also--unlike the Fortress--the mid-upper turret had a depression of 38 degrees when pointing sideways, and could make use of this since it wasn't positioned directly over the wings.

It was down to a combination of calibre and sighting. With regular sights you could argue no armament turned out to be sufficient in daylight - certainly not .303s. Reading what some were thinking at the end of the war - there were many that were up to trying the 'self-defending bomber' concept all over again once the gunners all had gyro sights.

Harris was unquestionably not going to commit his aircraft to 8th AF-like campaigns with .303s.

Concerning the Lancaster's under turret (FN64) - it worked fine, but wasn't fitted for two main reasons:

a) you can barely see anything underneath the horizon at night​

b) as stona mentioned, the spot was taken by the H2S installation - which was far more valuable for night operations. However; it wasn't impossible to switch back - and bomber command held many FN64 sets in case of a policy change and a switch to daylight operations was ordered.​

The single .50 under-defence position was also used by a lot more Bomber Command aircraft than people realize. A subject I'll have to get into down the road.