Sciatica, Facebook, Aviation themed pages and a claim about B17 and Avro Lancaster...

[ThomasP]

Hey Geoffrey Sinclair,

re the ranges of the B-17 and B-24 in the report up-thread.

The model of the B-17 used was a B-17E with modifications to emulate the upcoming B-17F production with Tokyo tanks. The B-24 model was the B-24D with Tokyo tanks added. Basically, they were doing proof of concept tests for the upcoming long range bomber operations in Europe.

re the "6,300 miles at 156 mph" for the B-24D.

Where did you find that? It should be 3600 miles (I think).

 

[33k in the air]

The FN64 wasn't a Mk.II-specific thing. All Lancasters could mount one -- provided the H2S didn't get there first.

Only a few early production Lancaster I came equipped with the FN64; these were removed before the aircraft became operational. As far as I can tell, only some Lancaster II had the turret installed and used operationally.

According to some reference books I've read, most Lancaster II were built with bulged bomb bay doors, and it was thought the enlarged doors would interfere with H2S so the FN64 was installed instead. To what degree Mark II were built with bulged bomb bay doors and ventral turret installed does not seem to be documented anywhere, nor whether the turret was removed or installed at a squadron level.

Both Halifaxes and Lancasters were getting ad-hoc .5-inch under-defence positions just as H2S numbers were allowing widespread fitment in Bomber Command, and the preference was for the radar.

Certainly some Halifax bombers received the Preston Green ventral turret, as there are a few photos of Halifax aircraft so equipped. I'm not sure any Lancaster bombers were so equipped.

The matter of ventral defences is poorly documented.

The only way I found to track down which aircraft had some sort of ventral weapon was to go to the squadron ORBs and look at the aircraft which had eight crew assigned, with the eighth crewman's position listed as 'mid-under gunner'. I did this with 408 Squadron. The first recorded instance of a mid-under gunner being part of a crew was on the March 30/31, 1944, mission to Nuremberg (Lancaster II serial number DS727; this aircraft flew 22 operations with a mid-under gunner being explicitly listed as part of the crew).

 

[ThomasP]

I remember reading that all the Lancaster B Mk II variant had bulged bomb bays of one type or another. The original bulge was designed for the CSB (Capital Ship Bomb), while the later bulge types were for the 8000 lb (and 12,000 lb?) 'cookie' (I think).

 

[Greyman]

Only a few early production Lancaster I came equipped with the FN64; these were removed before the aircraft became operational.

I suppose the key / sneaky word in my sentence there was 'could'. Even though they weren't really used operationally -- FN64 turrets were kept on hand in case there was a overall shift to daylight operations. Lancaster I and IIIs could mount these turrets.

According to some reference books I've read, most Lancaster II were built with bulged bomb bay doors, and it was thought the enlarged doors would interfere with H2S so the FN64 was installed instead.

Ah, this might explain where the 'only the Mk.II could mount the FN64' came from.

Certainly some Halifax bombers received the Preston Green ventral turret, as there are a few photos of Halifax aircraft so equipped. I'm not sure any Lancaster bombers were so equipped.

The matter of ventral defences is poorly documented.

There were a couple of different improvised under-defence set-ups, the Halifax's 'Preston Green' station (I certainly wouldn't call it a turret) was the most developed, but one was cooked up for the Lancaster as well.

I have a good bit of information on this subject and though I've said so before and failed to do so -- I'll try to get a reasonable summary together in the near future.

 

[Snautzer01]

I'll try to get a reasonable summary together in the near future.

Please do!

 

[MikeMeech]

I suppose the key / sneaky word in my sentence there was 'could'. Even though they weren't really used operationally -- FN64 turrets were kept on hand in case there was a overall shift to daylight operations. Lancaster I and IIIs could mount these turrets.



Ah, this might explain where the 'only the Mk.II could mount the FN64' came from.



There were a couple of different improvised under-defence set-ups, the Halifax's 'Preston Green' station (I certainly wouldn't call it a turret) was the most developed, but one was cooked up for the Lancaster as well.

I have a good bit of information on this subject and though I've said so before and failed to do so -- I'll try to get a reasonable summary together in the near future.

Hi
On the 'Preston Green' Harris in his 'Despatch', page 109 states: "... a, single .5-in mounting was designed and introduced into the Command for use in aircraft not carrying special Radar equipment, and this under defence gun was used on operations to a limited extent in Lancaster aircraft of No. 3 Group, and in Halifax aircraft of Nos. 4 and 6 (RCAF) Groups."

And on the FN. 64, limited numbers produced for use in Stirling, Halifax and Lancaster aircraft, the reasons he gave for not using it much were:
(a) It proved useless for night work as it employed periscopic sighting.
(b) No means were provided for the gunner to determine in which direction his guns were pointing, relative to the direction in which his own aircraft was proceeding. The position originally provided for this under turret was later occupied by various Radar devices."

Mike

 

[Geoffrey Sinclair]

The model of the B-17 used was a B-17E with modifications to emulate the upcoming B-17F production with Tokyo tanks. The B-24 model was the B-24D with Tokyo tanks added. Basically, they were doing proof of concept tests for the upcoming long range bomber operations in Europe.

As far as I am aware the B-24D started out with the capacity for 2,814 gallons of fuel, the B-17F needed the Tokyo Tank upgrade to match this.

The B-24 is reported to have 10% more power available for a 2% increase in top speed, but at 70% power either the B-24 drag and/or the R-1830 fuel consumption is higher resulting in around 66% more fuel used than the B-17 R-1820 combination, drop to 60% power and it is 25% more. What was so fundamentally bad with the B-24 design and/or the R-1830 to cause such a divergence in performance above 50% power but still end up with similar top speeds?

The similar top speeds suggests the B-24 drag was comparable to the B-17, making the R-1830 the main suspect, the extra fuel consumption curve suggests it used twice or more the fuel of the R-1820 at full power. All those designs using the R-1830 could have had a quite useful increase in range by switching.

re the "6,300 miles at 156 mph" for the B-24D. Where did you find that? It should be 3600 miles (I think).

See attached.

 

[Jabberwocky]

There's a direct wartime comparison of fuel consumption between a B-17E and a B-24D at WWII Aircraft Performance:

http://www.wwiiaircraftperformance.org/B-17/B-17E_B-24D_Comparison.pdf

The B-17's range advantage is remarkable. Partial results from the above test:

At 10,000 feet and 60,000 lbs initial gross weight

Fuel load	Engine power	B-17E range	B-24D range
1500 gal	70%	1405 miles	870 miles
	60%	1680	1400
	50%	Not given	1575
2000 gal	70%	1892	1165
	60%	2236	1880
	50%	Not given	2150
2500 gal	70%	2400	1460
	60%	2910	2380
	50%	Not given	2735

The B-17G is either lower drag than the B-24D (despite the supposed performance advantage of the Davis wing) or the R-1830 has developed a heavy drinking problem compared to the R-1820.

Results from the above test were also given for both types of aircraft at the same engine power and fuel loads (with cruising speeds given as well). At the same hp per engine the B-17 has a range advantage of anywhere from about 6% through to 42%!

Also, if the B-17 is galloping along at 660 hp per engine and 202-218 mph, the B-24D only just betters the B-17's range but bumbling along at 550 hp per engine. That also puts the B-24D down in speed by 12-20 mph.

 

[gruad]

There's a direct wartime comparison of fuel consumption between a B-17E and a B-24D at WWII Aircraft Performance:

http://www.wwiiaircraftperformance.org/B-17/B-17E_B-24D_Comparison.pdf

The B-17's range advantage is remarkable. Partial results from the above test:

At 10,000 feet and 60,000 lbs initial gross weight

Fuel load	Engine power	B-17E range	B-24D range
1500 gal	70%	1405 miles	870 miles
	60%	1680	1400
	50%	Not given	1575
2000 gal	70%	1892	1165
	60%	2236	1880
	50%	Not given	2150
2500 gal	70%	2400	1460
	60%	2910	2380
	50%	Not given	2735

The B-17G is either lower drag than the B-24D (despite the supposed performance advantage of the Davis wing) or the R-1830 has developed a heavy drinking problem compared to the R-1820.

Results from the above test were also given for both types of aircraft at the same engine power and fuel loads (with cruising speeds given as well). At the same hp per engine the B-17 has a range advantage of anywhere from about 6% through to 42%!

Also, if the B-17 is galloping along at 660 hp per engine and 202-218 mph, the B-24D only just betters the B-17's range but bumbling along at 550 hp per engine. That also puts the B-24D down in speed by 12-20 mph.

So this is saying that the b17 could have done a lot of the long range maritime patrols better than the B24 did?