B-17 vs. He-177 vs. Lancaster

[syscom3]

Also consider the airframe itself. Was their room for growth? The B29 added a crew member with specialized eqmt (radar and ECM) AFTER the design had been frozen and it was in production. Could the German design do that? It looked awfully cramped in there. Hardly any room to add all new weapons systems and additional aircrew.

What about the bomb bay? Could it handle oversize bomb loads without airframe modifications? The B29 could handle internal stowage of any bomb the allies had, save two.... the Grand slam and A-Bomb.

[delcyros]

Originally Posted by Juha

Hello Delcyros
a bit strange that Novarra gives exactly 100km/h greater max speed than that given in Griehl's and Dressel's book or in matter of fact in Brown's book. From G's & D's book is clearly seen that they have went through a lot of original technical documents on He 177. In my copy of Brown's book I have noted on mariginal that on p. 207 of Roderich Cescotti's Kampfflugzeuge and Aufklärer in Die Deutsche Luftfahrt series, which I have understood is rather authorative book, gives the same specs than those in Brown's book but some ammo figures plus some extra info, propeller diameter etc. Now I cannot recall exactly what the He 177 pages looked in Cescotti's book but I recall that in Do 17 part he had reproduced pages from original pilot's notes and speed graps because some of them were the same that can be found from Finnish Air Force papers. What's your opinion on Cescotti's book?

Juha

Hi Juha,

I don´t think the numbers necessarely contradict each other. That´s because the payload isn´t specified but has a huge impact on top speed. The He-177 tested in England was reported to have a top speed of 483 Km/h at something like 80% gross weight at slightly different altitude. I could imagine that the Nowarra figure belongs to top speed in it´s original sense (i.e. without payload, as none is specified-he specified the load on other bombers), while other figures belong to loaded conditions. This would be in within typical margins of other bombers. However, as I pointed out above, the flight instruction manual, which I haven´t seen so far, contains the information You want to get.

best regards,
delc

[Juha]

Thanks Delcyros
I'm still a bit sceptical. IMHO the weight itself should not have very big influence on speed, but of course I might be wrong. 177A-3 usually carried its bombs internally, IIRC only 2*SC2500 load was carried externally, so dropping the bombs should not have very big effect on speed. But not being expert on this I can be in error. I'm very busy now so I don't have time to check but IIRC max speed of Do17Z-2 at max load was 425km/h and 433km/h at 75% load according to German tests. So the speed difference wasn't big. It was different thing with a/c carrying most of their load externally, again IIRC Ju88A-4 max speed at max weight was 435km/h but after dropping its bombs its max speed was 475km/h.

Best Regards
Juha

[FLYBOYJ]

Originally Posted by syscom3

Also consider the airframe itself. Was their room for growth? The B29 added a crew member with specialized eqmt (radar and ECM) AFTER the design had been frozen and it was in production. Could the German design do that? It looked awfully cramped in there. Hardly any room to add all new weapons systems and additional aircrew.

What about the bomb bay? Could it handle oversize bomb loads without airframe modifications? The B29 could handle internal stowage of any bomb the allies had, save two.... the Grand slam and A-Bomb.

good points...

[delcyros]

Originally Posted by Juha

Thanks Delcyros
I'm still a bit sceptical. IMHO the weight itself should not have very big influence on speed, but of course I might be wrong. 177A-3 usually carried its bombs internally, IIRC only 2*SC2500 load was carried externally, so dropping the bombs should not have very big effect on speed. But not being expert on this I can be in error. I'm very busy now so I don't have time to check but IIRC max speed of Do17Z-2 at max load was 425km/h and 433km/h at 75% load according to German tests. So the speed difference wasn't big. It was different thing with a/c carrying most of their load externally, again IIRC Ju88A-4 max speed at max weight was 435km/h but after dropping its bombs its max speed was 475km/h.

Best Regards
Juha

You are welcome. I don´t want to convince anybody, just proposing what I have read. Everybody is free to draw his own conclusions, of course.
Adding 7t. of weight will have notable effects on performance. More if aerodynamic drag is induced by external loads. However, not weight per see reduces performances but cog-shift and, more important, the amount of power necessary to achieve a cruise speed / cruise altitude profile. This can be seen on the B-29 charts provided by HoHun.
A further notable difference is that the powersetting is not known for the top speed figures. I doubt that the DB-610 was ever cleared for 110% WEP, it was to troublesome (I might be wrong here), and it isn´t impossible that early engines possibly might have been limited even further artificially. I haven´t the necessary knowledge on this matter. A thoroughly made study of the engine and primary sources of the He-177 would be highly welcome to clear this. Perhaps someone can obtain a copy from the instruction manuals of the He-177 from the Luftarchiv Hafner.

[HoHun]

Hi Juha,

>I'm still a bit sceptical. IMHO the weight itself should not have very big influence on speed, but of course I might be wrong.

The size of the influence strongly depends on the altitude as well as on the relative load difference.

I just made a quick calculation based on a top speed of 520 km/h @ 5.7 km for a 31 t Heinkel He 177A-5/R2 using 1.3 ata/2600 rpm - these figures are from Heinkel datasheets, reprinted in the datasheet collection "Heinkel" (Aviatik-Verlag, no author/editor attribution).

With no payload, 50% fuel, 50% oil, I get a weight of 23915 kg, which gives a top speed of 545 km/h @ 5.8 km at the same power settings as above. (Ram effect is responsible for the slight increase in best altitude.)

However, if we look at altitudes above full throttle height, the difference is even more striking - at 31 t, the He 177 does 440 km/h @ 8 km according to my calculation, but at 23915 kg the possible top speed increases to 510 km/h at this height.

The reason for this large difference is that the large coefficients of lift necessary for flight at high altitude and heavy weights translate into very high induced drag, and getting rid of this weight increases the available excess power considerably.

If you ever wondered why high-altitude aircraft tend to have large wings - this is it

(From the perspective of performance analysis, the large influence of flying weight makes it very difficult to come up with accurate figures as there are few good sources that give the complete data required for an accurate analysis. So take my speeds for the He 177 as illustrations for the principle only, I don't really have enough data on the type to make any bullet-proof statements.)

Regards,

Henning (HoHun)

[Udet]

Syscom...can you confirm the figure for B-29s produced during ww2?

[syscom3]

Originally Posted by Udet

Syscom...can you confirm the figure for B-29s produced during ww2?

The figure is very accurate. Its from my B29 production book thats a trove of information. production essentially ended in Sept 1945. I beleive the AAF was already comtemplating production of the B-50 and saw no reason to build the B-29 as it was.

[Juha]

Thanks a lot Delcyros and HoHun
your answers made things clearier. I had wondered why they gave 80% of max weight performance but after reading HoHun's message I saw the light.

I had time to take a brief look on Do17Z and my memory had made one trick, the 433km/h speed wasn't for 75% load but for 7400kg which is nearer to 85% of max weight. And I admit that Do17Z was a bit different a/c than He177A.

Thankfully
Juha

[albion]

Best ww 1 bomber Vickers Vimy.First plane to fly non stop across the Atlantic.

[FLYBOYJ]

Originally Posted by albion

Best ww 1 bomber Vickers Vimy.First plane to fly non stop across the Atlantic.

Brilliant! Just Brilliant!

[Watanbe]

I think people in general read far to much into the defensive arguments on bombers, if trying to avoid interception speed and altitude are the crucial factors IMHO. For example take a look at arguably the Allies hardest planes to intercept. The Mosquito (speed) and the B29 (altitude). Obviously air superiority is the most important factor and even the heavily armed B17's were massacred before adequate fighter support.

Kurfust I agree that the Lancaster was a bomb truck. However in IMO that's what makes a good bomber. The Lancaster dropped a lot of bombs over Europe in WW2 and it gets my vote.

Personally I don't see the point in a lot of the 'heavy bombers'. The B17 had a crew of 10, normal bomb load of 4000lbs and a speed of 500km/h give or take, while a plane such as the Mosquito had a crew of 2 and could carry the same payload at 550 km/h give or take? Why not send faster more agile Mossies and save yourself the risk of losing 8 more trained crew members.

[kool kitty89]

The B-29 was pretty fast as well.

It should be noted that the B-17 could fit in the "altitude" category as well, (technically) being able to operate at the same high altitudes as the B-29 (the B-17 actually had a higher ceiling), but the operating conditions were much worse for the B-17 crews. (particularly for the gunners)


The defensive armament vs performance argument for bombers is an interesting one in its own right, something I'm not quite sure on, but I tend to lean toward the performance side.

However, besides smaller, agile aircraft like the Mossie, you could still argue the "performance" issue for aircraft like the B-17. Given it's fairly impresseve speed performance at altitude, immagine it stripped of all armament, reduced to minimum crew and possibly a pressurized cabin. Performance and range would significantly increase, and the crew would be half (or less).

[Watanbe]

That is true, but they didn't operate operational in that specification. It would be very interesting. The only thing counting against the B17 is its payload. You also mentioned the altitude capabilities of the B17, was the B29 able to fly higher than the bulk of German late war interceptors? I know the Japanese really struggled to find a fighter with altitude to intercept the B29. I think the Germans had the perfect idea with the Arado 234.

[panthergreen]

lancaster for bombload, range and quality of engines.