B-17 and B-24: plausible upgrades?

[tomo pauk]

The 4-engined work horses that bore the brunt of daylight bomber effort vs. Axis countries, conceived under belief that high altitude cruise and numerous defensive MGs would enable them to destroy enemy targets with impunity, even if the enemy is technically tactically adept. The realities of war proved that reasoning to be mostly wrong, it took friendly fighters to make heavy bombers viable again vs. LW, while the B-29 took the fight to Japan proper.

So what plausible upgrades could USA undertake, in order to make the B-17 and B-24 better suited for the tasks, even if planes taking those tasks might be contested by enemy actions? There was one real-life upgrade to the B-17, namely the version with V-1710s, so that might get the ball rolling.

 

[fastmongrel]

I think the main problem was a low cruising speed so anything to get that up is good maybe even start stripping the guns off. I know thats controversial but surely a shortened time over the continent is better than a leisurely 180 which I believe was the usual speed. What was the cruise speed of the V1710 version and did it have turbos.

 

[tomo pauk]

Yes, the XB-38 was using turbos. The B series of turbos was used on P-38, B-17 and B-24. The performance, from Wikipedia:

Maximum speed: 327 mph (284 knots, 526 km/h)
Cruise speed: 226 mph (197 knots, 364 km/h)
Range: 3,300 mi (2,870 nmi, 5,310 km)
Service ceiling: 29,600 ft (9,020 m)

 

[gjs238]

With the benefit of hindsight, embrace the Schnellbomber concept and abandon the fortress concept.

 

[Shortround6]

Then you need entirely new airplanes, not an upgrade. Ditching the turrets might only gain you 20-30mph. Not enough to give immunity from interception. Formation flying requires lower speeds and streaming un armed or lightly armed bombers across Europe at around 260mph in daylight is setting up a shooting gallery even worse than what was done.

http://www.zenoswarbirdvideos.com/Images/B-17/17FOIC.pdf

Please note that any fuel above 2800 gallons required bombbay tanks.

 

[cimmex]

Why upgrade old models when new designs (B-29, B-32) are almost ready.
cimmex

 

[tomo pauk]

The key word is 'almost'. Allies needed heavy bombers in overwhelming numbers in 1942-45, not in 1945-46. The better bombers, the better.

 

[T Bolt]

The key word is 'almost'. Allies needed heavy bombers in overwhelming numbers in 1942-45, not in 1945-46. The better bombers, the better.

Bombers needed in 'overwhelming numbers' is an impotent phrase. Some of the major upgrades of those bombers that were in the works were not followed through with because it would have slowed down production so minor upgrades were settled for that did not disrupt the production lines.

 

[drgondog]

If the cruise speed for B-17G could be increased for same bombload to say 190mph IAS at 25000 feet - it would be a huge benefit. The figures on the XB-38 are unclear regarding whether 226 is TAS with a load.. 226mph is only 20mph TAS over 150IAS at 25000 feet.

I would strip both waist guns, the two lateral 50's next to Bombadier/Navigator, and the radio operator hatch 50... reduce crew to 8 to help get there. That would be ~ minimum 1300-1400 pounds (keep half the ammo for another 400+ pounds)

Boosting the speed to that level (240mph TAS) drastically reduces the Essing cycle for the escorts, conserving fuel for them. Moving along at 190 at that altitude reduces the number of passes an Fw 190 and 109 can make if they start with head on pass.. If coming in trail they are exposed to more firing solution time from the B-17s because the closing speed is less. Makes it tougher for Me 110's and Ju 88's to maintain contact from favorable position of their choice. Tougher (and shorter time) tracking solutions for flak batteries, more flexible mission planning due to less air time over Europe, probably a lot less fuel and oil consumed per mission. After bomb load gone, the B-17 would really be moving right along making for tougher intercepts.

Is it a major advantage vis a vis losses in August/October 1943? I don't think so. 1944 - definitely.
Disadvantages - only so much capacity for Allison, different logistics set up, Additionally the Allison/glycol cooling system is more vulnerable which probably increases loss % as a function of battle damage.

If I had the latitude I would make the following defensive changes. Reduce defensive gun stations to four.

Eliminate the G chin turret and replace with B-29 type 2 Gun turret for lower drag. Replace the top (manned) turret with a four gun B-29 top turret. Replace Ball turret with two gun B-29 lower turret and install the B-29 tail turret so that all gun stations are controlled by same fire control system.

Gunner stations (five - Bombadier, new blisters (3) with Primary at radio hatch but both waist positions can be manned later, and Tail). The Central fire control area is dominated by the one replacing radio hatch. The Engineer moves there. The radio operator can man either of the waist systems or back up engineer. The 'Radio hatch blister is same size as the YB-40 turret there. He can control upper turret with option to control lower for beam attacks or tail in case the tail gunner taken out. The tail gunner has primary control of tail turret and lower turret. The bombardier has chin and top and lower for company front attacks.

There is a complete lack of coverage for a cone below the new B-17 due to lack of visibility at any gun station. For all practival purposes that is meaningless. For head on attacks the bombardier has 8 .50's slaved to his sight. For trail attacks the tail gunner has lower and tail with 4x.50's slaved.

This system was installed in first prototypes so was available in 1942 but certainly in late 1943. The 'lull period' would have been a good time to retrofit at Service Centers.

This concept with computing gunsights and lower drag, fewer crews, ability to mix and match your best gunners at controls and put most firepower in one hand should be of benefit.

 

[razor1uk]

In the samilar way to how Stalin said and ordered Shturmoviks like bread for the soviet army, so constant 'B' production could be thought of for the USAAF until the end of the war was insight.

Thats why the infuriating slow production build up and of Willow Springs (Mile-Long?) plant caused congressional inqueries public/media outrage, possibly with some threats of jail-time or off-to-the-front to some employees along its way to building staff skills/knowledge and production momentum.

 

[tomo pauk]

The demand for V-1701s was less in 1944, than in 1943. The P-40 P-39 were nearing cancellation, the P-51 already switched to Packard Merlin. Because of that, Allison delivered just a tad less engines in 1944 than in 1943, contrary to other engine manufacturers, despite the production lines beginning to reap the benefits of mass production.
Thanks for pointing out the often overlooked threats for the B-17s, Bill. The Flak and heavy fighters would not like the faster B-17, that's for sure.

Bombers needed in 'overwhelming numbers' is an impotent phrase. Some of the major upgrades of those bombers that were in the works were not followed through with because it would have slowed down production so minor upgrades were settled for that did not disrupt the production lines.

Sorry that you feel that is an impotent phrase.
The bombers were flown by airmen. That little thing might one have in mind when deciding whether is 50 or 100 bombers more produced is worth 200 or 300 airmen killed, missing or POW.
The B-17 (with V-1710s) cruising at 220-230 mph will be above German-held Europe maybe 4 hours, while the other, cruising at 180 mph, will be there 1 hour more. That's 25% more time the Germans have the opportunity to kill the slower bomber.

 

[T Bolt]

Sorry that you feel that is an impotent phrase.
The bombers were flown by airmen. That little thing might one have in mind when deciding whether is 50 or 100 bombers more produced is worth 200 or 300 airmen killed, missing or POW.

I didn't say I agreed with that line of thinking, I just believe it was a large factor in which upgrades to incorporate into bomber production. My father's B-24 was shot down by anti-aircraft fire and he spent some time as a guest of the Third Reich, so my feeling is that any upgrades that could have been made to the heavies to increase there survivability should have been made regardless of a possible drop in the number of bomber coming off the assembly lines.

 

[tyrodtom]

I've seen the B-29 turret control system talked about, but how effective was it in real use.
It's hard to say if it was really given much of a test over Japan, and later over Korea, it evidently wasn't much help against the Migs.

 

[dobbie]

Instead of going to water cooled Allisons, why not move to a larger radial engine instead? Some of the old Privateers-a modified B-24, were upgraded from the P&W 1830 to the Wright R2600 and used for water bombing for quite a while. Dont know if the B-17 could be modded to accept them, but seems logical. I would rather see an R2800 but Im not sure thats feasible.

 

[drgondog]

Tyrod - the fire control system for the B-29 with the centralized capability apparently was 'more effective' but I don't offhand know how to quantify the increase.

Two factors were different - one the armor plating and top speed of most of the Japanese fighters were less than German counterparts. The second was all power turrets which was a more stable gun platform not only for firing but also for being slaved to hand held post mounted gunsight - making turret slew and gun elevation changes slaved to the computing gunsight. The latter was really important - eliminating the required hand/foot co-ordination of the manned turret.

The intangible factor - the high speed of the B-29 made a pursuit curve approach much more difficult - making only head on and trail attacks feasible, reducing most shooting to low deflection shots from the bomber.

The problem in Korea was the same as B-17/Me 262 issues in ETO. The MiG 15 and Me 262 were too fast for the slewing speed of the turret to track when the deflection angle opened up due to a high speed pass.

If the 'imaginary' retrofit had been feasible I believe it would have been far more effective to have up to 8 forward firing 50's blasting at a fighter making a head on pass - all under control of one person with computing gunsight. Having said that, the computing gunsight could never account for a high speed break as the wing span ring would have no meaning whatsoever for keeping a firing solution on a deflection shot on a high speed head on pass as the fighter breaks off.

On the other hand, that firepower would be equivalent to a P-47 from each B-17 in range, shooting low deflection for a couple of seconds.

From the stern, only four but shooting at 1/4 the closing speed - a much longer relative time with concentrated fire from tail and ball or from 'ball', tail and top (when rudder interrupter isn't engaged).

 

[tomo pauk]

The B-24 was supossed to cruise faster than B-17. Data from Wikipedia:

Maximum speed: 290 mph (250 kn, 470 km/h)
Cruise speed: 215 mph (187 kn, 346 km/h)
Stall speed: 95 mph (83 kn, 153 km/h)
Range: 2,100 mi (1,800 nmi, 3,400 km)
Ferry range: 3,700 mi (3,200 nmi, 6,000 km)
Service ceiling: 28,000 ft (8,500 m)

The max continuous power was 1100 HP per engine, ie. same as in turbo V-1710, and 100 hp more than B-17's Cyclones.

 

[cimmex]

I don't think changing the motors of an aircraft is an easy task. I'm sure there are fixed contacts between aircraft manufacturers and the motor supplier. You cannot simply cancel such a contract without losing a lot of money. Don't forget even during war this is a financial business. But these things are often forgotten in those hypothetical scenarios.
Cimmex

 

[dobbie]

Its certainly not easy, but can and had been done. Probably the most famous swap was the P 51 changing from Allisons to Packard-Merlins. The Curtiss C46 was originally supposed to have the R2600 but was changed to the P&W R2800. P-40F models swapped the Allison and used the Packard Merlin with a single stage supercharger. The original B 17 used P&W Hornets before the Wright Cyclones. Im sure theres more examples......

 

[Shortround6]

Instead of going to water cooled Allisons, why not move to a larger radial engine instead? Some of the old Privateers-a modified B-24, were upgraded from the P&W 1830 to the Wright R2600 and used for water bombing for quite a while. Dont know if the B-17 could be modded to accept them, but seems logical. I would rather see an R2800 but Im not sure thats feasible.

The B-17 and B-24 both grew in weight quite a bit from early models until late but there is an upper limit somewhere before you have to beef up a considerable amount of structure ( redesign the aircraft).

46,250 pounds gross for a British Liberator II? First delivery June 2, 1941

B-24D; 32,605 pounds empty, 55,000 pounds gross, Maximum takeoff weight 64,000 pounds.
B-24J; 38,000 pounds empty, 56,000 pounds combat, 71,200 pounds maximum overload.
PB4Y-2 Privateer: 39,400 pounds empty, 64,000 pounds gross

The water bombers saw the elimination of several tons of guns, turrets, ammo and armor, self sealing tanks may have been removed and replaced with normal fuel cells/tanks. The Mission profile was also quite different. Water bombers don't usually fly 400-800 miles one way from their base to make drops? Even in the Rocky Mountains operational heights are thousands of feet lower than flying over Europe.

For some reason the R-2600 was never fitted with turbos ( at least not more than a handful). This means a non-turbo R-2600, while quite useful for getting a loaded plane off the runway ( and pulling up to avoid a ridge after dropping a load of water) overs very little power advantage over a turbo R-1830 at 20,000ft and above. It WILL burn more fuel. The engines and props alone will go 1 1/2-2 tons more than the R-1830s.

 

[Shortround6]

Swapping engines could be done, a lot of these planes were contracted for in batches. Company "A" might be told they were getting on order for 2000 planes all on one day but the actual contract might state that the first batch of 400 had to finished by a certain date. later Batches could be modified. Republic got contracts for the P-47B and P-47C on the same day.

BUT engine swaps cannot be done with a just a few weeks notice and you have to be sure that the engine swap is going to do what you think it will. Again swapping a bigger non-turbo engine for a smaller turbo engine may not give the performace you want were you want it.