Re: Russians bomb Berlin 13 September 1942
 

Hello Paul
Which of the performance figures of the AM-35A powered TB-7/Pe-8 were low for a heavy night bomber by 1942? Maximum speed 443 km/h at 6,360 m, service ceilings 9,300 m, maximum bomb load 4,000 kg, maximum range with 2,000 kg bomb load and full fuel tanks 3,600 km.

Juha

Re: Russians bomb Berlin 13 September 1942
 

If you reffer to TB-7 models 1939 then they had serious problems with the
main supercharger units which severely affected the service ceiling of the
a/c and as such the TB-7 was then a low performance bomber.As of early
1940 the Plant 124 halted production.However later on the same year Mihail
Kaganovitch (brother of famous Lazar Kaganovitch ) who took over the plant ordered
the next 6 TB-7 to bee equipped with AM-35A powerplants producing 1200 HP
each .In parallel Charmosky Diesel engines M-30 and 40 series were produced
as an optional outfit.

On August 9th 1941 the bombers equipped with M-40 and led by famous Arctic
flyer Vodopyanov raided Berlin. By mid 1942 the TB-7 was equipped with Shvetsov
1800 hp M-82 engines consisting of twin superchargers air cooled radial engines.

While the first batch of M-82A engine run through infancy problems which were
eventually overcomed by 1943 the plant chief developing section was led by J.Nezval one
of the leading Tupolev assistants. By autumn / winter 1942 some of the aircrafts
developed some sort of tech problems due to manufacturing QC issues .In 1943
the Germans enhanced their night fighter ME-110 units which managed to shot down
4 TB-7's . On the same year due to extra asymetric power during take off run it
caused the bomber to veer off the runway an event which cause the loss of 6 TB-7
some of these incidents were also related to compressor bearing failures.

By late 1943 early 1944 the PE-8 was less powerful and ecconomical but more reliable
for the units which operated the a/c such as 746 AP ADD.


Generally speaking TB-7 was by mid 1942 anything but a low performance bomber, rather
a bomber which once in a while was put on AOG status not due performance but
messed up production QC issues .

Alex K

Re: Russians bomb Berlin 13 September 1942
 

Hello Juha,

I do not think there is any evidence that the figures that you cite were ever achieved by operational aircraft, with the exception of maximum bombload. The altitude performance is particularly exaggerated, even the Lancaster had an operational ceiling of just 22,000 feet.

Warm regards,

Paul

Re: Russians bomb Berlin 13 September 1942
 

Be a bit careful. The usually quoted service ceiling is not the same thing as a realistic operational altitude when fully loaded. It is quoted for an value of climb rate that is considered so low that simply isn't worth trying to get any higher. Nowadays that could be 250 ft/min or higher (sorry, it's been a few years since I did this): for WW2 aircraft it is likely to be lower, perhaps 100 ft/min or less. It will normally be calculated for a range of weights/configurations/conditions, but the one quoted will not be the one at maximum load/maximum drag/hottest day. Unless, of course, it actually states so, but that doesn't make good publicity and doesn't reflect the genuine capability of an aircraft.

A Lancaster will have a quoted service ceiling above its (normal, varied) operational ceiling: though Putnam's The British Bomber only quotes 24,500ft unloaded. The Pe8 will have an operational ceiling (as said above) below the quoted 9,300m, but that needn't imply no Pe8 ever got up there.

There are separate arguments about reliability, build and training standards, and how average aircraft in average service conditions with average crews will never match predictions or even test results.

Re: Russians bomb Berlin 13 September 1942
 

Hello
I'm well aware that the operational ceiling is a different figure than the service ceiling. But it isn't surprising that the AM-35A engined Pe-8 had higher ceiling than the Lanc because AM-35A was a high altitude engine, the same engine powered MiG-1 and MiG-3. Just look the altitudes at which the Pe-8 and the Lanc B. III achieved their respectively max speeds. Pe-8 had its problems and limitations but it wasn't a low performance plane.

Re: Russians bomb Berlin 13 September 1942
 

Hi,

The TB-7 WWII VVS operational records ( Russian language ) with AM-35A engines show anything but low performance , also keep in mind values such as TAS, CAS as into speed /payloads etc . The problems and limitations of TB-7 had nothing to do with low performance , as such Juha statements apply ,rest are presumtions .

Re: Russians bomb Berlin 13 September 1942
 

Graham, yoru description of the difference between service ceiling and operational ceiling is correct, of course. The operational ceiling is the one we are interested in here. The problem that I have with Juha's figures is that, in all likelihood, they refer to design bureau test results, not military acceptance trials of a production aircraft.

An added problem with the Pe-8 is that the production aircraft flew with an engine, the Mikulin AM-35A, which was not the originally intended powerplant. It is possible that the altitude of 9,300 m was reached by an early TB-7 with a fifth engine in the central fuselage, acting as a supercharger for the other engines. The concept was similar to that later used by the Hs 130E.

To cut to the chase, I think figures from the Pe-8 manual or, better still, from operational unit records need to be cited here. Otherwise, it's not possible to give credence to the performance figures above.

Juha, you are right that the AM-35A had a relatively high critical altitude. It needs to be demonstrated that this was sufficient to propel the heavy and aerodynamically conservative Pe-8 to a high altitude. I have my doubts.

Warm regards,

Paul

Re: Russians bomb Berlin 13 September 1942
 

If you can get a hold of the opersvodka ( Russian language ) of 746 AP ADD you will determine that the missions flown to Warsaw,Berlin, Bucharest,Danzig and Stalingrad
from Kratowo and Lipetsk were ranging at alt. from 23'000 ft to 29'000 ft .

Re: Russians bomb Berlin 13 September 1942
 

Thank you for the information, Alex. Were these the average altitudes at which the sorties were flown, altitudes over the target, or something else?

Warm regards,

Paul

Re: Russians bomb Berlin 13 September 1942
 

Paul

The 746 AP ADD opersvodka does not specify overhead where, when and how these altitudes
were flown , fact is that on the Luftwaffe's eyes possibly also on those of OSS and SOE
the PE-8 was an efficient high performance long range bomber . On that context I would
like to recommend you the book attached ( took a shot for you ) .Russian igenuity was not
underestimated and should not be contested.The problems affecting equipment performance
and their air personnel during WWII were from within and not from outside , something I
am certain you know .I am not certain where this book can be acquired ,coze I got mine
from USAF Maxwell AFB ( Air University )