B-17 and B-24: plausible upgrades?

GregP said:

I don't believe the chart above. If it were true, we'd surely have reports of 10,000 pound bomb loads being used in the war from B-17's on a regular basis. I daresay they might have flown a few, but not many. Once we had airfields in France, if the chart were true, we'd be regularly hauling 10,000 pound bomb loads to Germany ... and we didn't, even at the end of the war, when we surely were within range.

Click to expand...

wuzak said:

I wonder if the 10,000lb "bomb load" is actually 10,000lb military load, including nearly 6000 rounds of ammo?

Click to expand...

B-17G Range vs Bomb Load

This shows 13,000lb internal load @ 1100 mile range, and just over 4000lb at 2500 mile range. It also states that the bomb load includes 2000lb for crew, 1080lb for oil and 1368lb for ammunition. That totals at 4448lb, so the 13,000lb bomb load really is 8552lbs, and the 2500mile range can only be for ferrying.

10,500lb (real bomb load 6000lb) gives a range of 1500 miles,

Same objection applies. We didn't ... why not?

I know it COULD carry 10,000 pounds, but not at the range in your post. I am given to understand that at 10,000 pounds the entire range was less than 600 miles, so the radius would be less than 300 miles minus whatever it took for reserves, explaining why we didn't bomb with 10,000 pounds very often. This comes from B-17 verterans who were crew members in WWII. We have 2 - 3 in our volunteer group. All said they never flew or heard of anyone else flying with 10,000 pounds in the bomb bay. But they DID hit the target with what they had.

Alas, I still didn't manage to find the B-17 manuals today again. But I DID get the covers and hatches back on the Bell YP-59A and it will be on display at our airshow in all it's glory. We are all in airshow mode at this time (May 4 5). We are almost done with the windscreen and finished the sliding canopy more than a year and half ago. Closing in on it .... and can't wait for it to start and taxi and fly under its own power. Hopefuly sometime SOON. I KNOW its close when Steve Hinton is reading and studying the pilot manual for the aircraft. It won't make this year's show as a runner, but will in 2014 ... even if it just taxies. Hopefully, 2014 will be its debut as an airshow performer.

If not, then something extraordinary would have to happen to postpone it. It's that close to being done. The port aileron is being reskinned now and the starboard one is next ... then the instrument panel had to be made and populated. The rest is just about all done.

If it doesn't happen, the culprit will most likely be leaky fuel cells ... but we all hope not. We'd have to de-rivet the wing skins to change them ...

GregP said:

Same objection applies. We didn't ... why not?

I know it COULD carry 10,000 pounds, but not at the range in your post. I am given to understand that at 10,000 pounds the entire range was less than 600 miles, so the radius would be less than 300 miles minus whatever it took for reserves, explaining why we didn't bomb with 10,000 pounds very often. This comes from B-17 verterans who were crew members in WWII. We have 2 - 3 in our volunteer group. All said they never flew or heard of anyone else flying with 10,000 pounds in the bomb bay. But they DID hit the target with what they had.

Click to expand...

You seem to have glossed over the fact that the chart shows that 4448lbs of "bomb load" was actually men, oil and ammo.

It is also my understanding that the B-17 could not be configured to carry 10,000lb of bombs internally. The closest is, maybe, 6 x 1600lb bombs.

It was actually rated for eight 1600lbs internally

B-17F, -G, Fortress Mk. II Pilot's Flight Operating Instructions.pdf‎

Available in the manuals section of this website.

See pages 53 55.

Also see page 98. Basic (NOT empty)weight for B-17F was 41,300lbs:

Including:

Crew nine
nine .50 cal guns
3500 rounds of .50 cal ammo.
144 gallons of oil
1500lbs of wing tankage. (not fuel)

See condition II.

65,000lb gross.

6,000lb inside
4,000lb external
2280 gallons of fuel.

Offhand I don't recall seeing any 8th AF mission with more than 6,000 pound bomb load (2x2000 + 2x1000) for early missions on sub pens 1942-early 1943. After that, probably 95% w/5000 for intermediate, and mostly 4000 pounds for Berlin and beyond.

I do know some experiments were made with bombs on wing bomb racks but the drag penalty was too high to be useful - hence the Aphrodite program.

Shortround6 said:

It was actually rated for eight 1600lbs internally

B-17F, -G, Fortress Mk. II Pilot's Flight Operating Instructions.pdf‎

Available in the manuals section of this website.

See pages 53 55.

Also see page 98. Basic (NOT empty)weight for B-17F was 41,300lbs:

Including:

Crew nine
nine .50 cal guns
3500 rounds of .50 cal ammo.
144 gallons of oil
1500lbs of wing tankage. (not fuel)

See condition II.

65,000lb gross.

6,000lb inside
4,000lb external
2280 gallons of fuel.

Click to expand...

Interestingly page 55 shows only 6 stations can take a 1000lb bomb, racks 1 4 able to take the 1600lb bomb, but not the 1000lb bomb. I wonder if that is because the 1600lb bomb is SAP and is narrower than the 1000lb bomb?

Individual stations did not have load ratings. The maximum load raiting for outboard racks was ~2000lb and ~5000lb for the inboard racks. This link list a good number of homogeneous bomb loads. Note that the chat lists stations 7/28, 10/31, 18/39 for the 1600lb AP bomb. But the hoisting diagram shows the more common 8/29, 11/32, 16/37. My take is the chart lists a load that maximizes space for smaller bombs on the outboard racks. The maximum heterogeneous internal bomb load may be as high as 13,200lbs or six 600lb and six 1600lb AP bombs.

wuzak said:

Looking at the numbers on Wiki the R-2000 gained about 150hp over the R-1830, and around 300lbs. Is changing the B-24 from R-1830s to R-2000s going to be worth it?

Click to expand...

It wouldn't be available until late in the war. R-2180 seems to be a very similar engine with a longer stroke, first run in 1936. As far as I can tell, Pratt abandoned it just because they had too many projects on the go. Seems the like perfect upgrade engine for so many planes. B-17, B-24, F4F, maybe Devastator.

Kurt said:

It wouldn't be available until late in the war. R-2180 seems to be a very similar engine with a longer stroke, first run in 1936. As far as I can tell, Pratt abandoned it just because they had too many projects on the go. Seems the like perfect upgrade engine for so many planes. B-17, B-24, F4F, maybe Devastator.

Click to expand...

In marketing terms the R-2180 had been upstaged by Wrights R-2600.
There was nothing really wrong with the R-2180 but there wasn't anything really right about it either.
It used the same cylinders as the R-2800, just fewer of them, but this means the R-2180 was the same diameter as the R-2800 so you had less power for the same frontal area/drag (roughly). The R-2180 was about 1in smaller in diameter than the R-2600 but about 6 in bigger than the R-1830. By 1939 the R-1830 was good for 2700rpm vs the 2500rpm of the R-2180. With more development they could have gotten more RPM out of the R-2180 but P&W was betting on the R-2800. They wanted to beat the R-2600, not be a distant 2nd place in the market place.
The R-2000 engine was something of an oddball. It started as an engine that would make the same power as the R-1830 engine except that it would do it on lower grade fuel. Turns out that the 100/130 fuel was being produced in quantities that allowed the transport aircraft to use it and not be restricted to 87-91 octane fuel. A lot of it's reason for being had disappeared. It seems (most articles/books don't actually say) that they used a lot of R-1830 parts or engineering. The R-2000 engine made 150-250hp more at take-off than the R-1830 engines using the higher octane fuel but they never gave it a supercharger that allowed the engine to make much more power at altitude.
The R-2180 reappeared after WW II using about 1/2 of the 28 cylinder R-4360 and pretty much proved the P&W Market men correct. Nothing really wrong with it, used a lot of common parts with the 28 cylinder engine. Found one commercial buyer, SAAB. In the US Convair and Martin went for the R-2800 to power large twin engine commercial aircraft.
By 1944 P&W was making 1350hp R-1830s (needed new cylinders with better cooling) and Wright was making 1350-1425hp R-1820s but both of these required a lot of new tooling. You could not make the Wright engines on machinery that had made the 1200hp R-1820s.
Devestator never got even a 1000hp R-1830 let alone a 1200hp version. Devastators were old.

B-17 and B-24: plausible upgrades?

The both had some, especially B-17 before and during the war. Compare B-17D to B-17F.

The B-17D was an early-war stopgap, with basic upgrades over the C (self-sealing tanks, armor) but insufficient armament and range for 1942's intense combat. The B-17G, the final major variant, was a battle-proven fortress with 13 machine guns (including chin and Cheyenne turrets), stronger airframe, and extended range, dominating strategic bombing from 1943-1945. The D saw limited Pacific action, while the G was the iconic workhorse of Europe's air war, far surpassing the D in survivability and effectiveness.

But beyond that -- the plausible upgrade of the B-17 was the B-29, and of the B-24 to the B-32.

That seems to be a pattern. It should be noted that the specs for the next generation warplane were usually written before the current type had even started production

OK, since the ghost of the B-38 was stirred, put aside the minimal speed improvement over the B-17F, but what if anything close to the claimed 3300 mile range could be achieved? A 60% increase in range is nothing to sniff at. This performance far exceeds anything the B-24 could do and rivals the B-29, albeit with a far lighter long range bombload. Until the B-29 is available, the B-38 might have been very useful in the Pacific. The slight decrease in service ceiling would matter less in the Pacific and is still better than the B-24.

How about long range photo-recon and maritime patrol versions of the B-38? These could be useful in the island hopping and interdiction campaigns. If somehow Wake could have been held or retaken, using it as a forward staging base for B-38 extreme long range bombers to conduct an enhanced harassment campaign of the Mandates could have become a real thorn in the Japanese side.

tomo pauk said:

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?

Click to expand...

How about pressurization and thus capable of higher altitudes and higher speeds? The B-17 derived Boeing 307 Stratoliner, first flying in 1938 was pressurized. The twin engined, pressurized Lockheed XC-35 was introduced in 1937, so might also provide some key learnings. We needn't wait for the B-29 to give the USAAC a pressurized four engined bomber. Accurate bombing from over 30,000 ft will be a challenge to be overcome.

Admiral Beez said:

How about pressurization and thus capable of higher altitudes and higher speeds? The B-17 derived Boeing 307 Stratoliner, first flying in 1938 was pressurized. The twin engined, pressurized Lockheed XC-35 was introduced in 1937, so might also provide some key learnings. We needn't wait for the B-29 to give the USAAC a pressurized four engined bomber. Accurate bombing from over 30,000 ft will be a challenge to be overcome.

Click to expand...

What about using the remote turrets being developed for the B-29, but with a simpler control system?

Specifically replace the ball turret with a remote turret, and change the waist gunners to be the turret operators.

Remote belly turrets had been tried on the B-17E. The technology wasn't up to snuff.

Douglas A-26 used remote turrets. Success was ????

In part because they only had one gunner and he had to switch between the lower periscope and the upper. Turns out that periscopic sights are not a good idea. Too much disorientation of the gunner.

Next question is production capacity. They could build the turrets. At what point could they deliver enough remote sighting systems?
First B-29 operations (june 5th 77 planes out of 98) were in June of 1944 and the summer of 1940 (or even late spring) of 1944 is not early enough to make a large change in US bomber operations over Europe. 2-300 B-17s in June of 1944 with remote turrets?

A problem with larger radial engines on the B-17 & B-24 was it wasn't simple engine swaps. It was a powerplant swap. you need different cowls for cooling, you may need a different turbo (or slight change) to suit the increased airflow (or accept slightly lower ceilings). You are certainly going to need larger intercoolers to handle the air flow.
The water bomber B-24s that used R-2600s got rid of the turbos and intercoolers and ducting.

Next thing to consider with B-17s and B-24s is that very often they were running at well over initial design weight. A lot of the B-17 overload conditions came with restrictions until certain parts were upgraded, at which point the AAC increased the overload weight limit again and the restrictions (or new ones) came back. I don't know about the B-24 but I guess there was a similar progression.
A few of the B-17 restrictions were no pivot turns over a certain weight. Depending on runway surface the pivoting leg could bury itself and/or snap. Use of the Tokyo tanks (outer wing fuel tanks) came with a few restrictions. Sometimes at the higher bomb loads the outer wing tanks had to be used instead of filling the inner wing tanks to spread the load out. Too much weight in the fuselage and inner wing between the landing gear could over stress the wing.
Using bigger engines may increase performance (speed/climb) but using the extra power to increase gross weight may require a lot of changes. Greater engine weight without changes in structural weight may mean lower payload for the same gross weight. Either less fuel (less range) or lower bomb load (more missions for 1000 tons dropped). Maybe it works out and maybe it doesn't?

The early B-17E production (112 aircraft) used the Sperry remote turret in the belly position (not the Bendix turret as usually stated). Details and photos here. The gunner's location was odd to say the least.

There was also a Bendix remote turret fitted in the B-25B to G.

Then there was the Bendix chin turret in late B-17F and B-17G

And then we have the General Electric system as fitted in the A-26.

Shortround6 said:

Douglas A-26 used remote turrets. Success was ????
View attachment 848703

Click to expand...

That reminds me of the Lancaster's.