Questions about the Yak-9M

[kolya1]

Hello,

Could somebody give me a few precisions about this one ?

From what I could read, it was essentially a Yak-9D wing (with fuel tanks) matched with a Yak-9T's lengthened fuselage, along with a few other refinements, and was produced (from May 1944) in 20mm and 37mm-armed variants, and with M-105PF and M-105PF2 engines...

Could somebody help me about the "other refinements" (I read something about the engine-radiator controls...) ?

And my second question is related to this airplane's performances, The figures I could get gave speed and climb figures which were somewhat lower than those observed on 1942 Yaks (less than 520 km/h at sea level, not even 580 at altitude), and I wondered :

- If they were not higher, why was such an airplane produced so much from mid-1944, when much higher performance soviet planes were already appearing ?

- Was there a significant difference for the planes equipped with the upgraded M-105PF2 engine ?

Many thanks in advance,

Kolya.

[Graham Boak]

As I understand it, the 9M was a standardised variant with advantages from different earlier variants. The 9K did not have a lengthened fuselage, but a more rear-set cockpit.

As for why the aircraft was still in production when better types were available: this is something that can be seen in all airforces. Why were Merlin-engined Spitfires still being produced when Tempests and Griffon-engined Spitfires were being made? This is because it takes time and effort to change a production line from one type to another. In this time no aircraft are being made: it is better to build a useful if imperfect type than nothing. Plus the new types require new engines, and other new components: there is no way that these can be created in large numbers instantly. There simply were not enough better engines to equip more advanced airfames, even had these been available. These things take time.

[kurlannaiskos]

M stands for Modifitsirovanniy meaning modified.
the M wing has two distinct differences from the Yak-9D wing.
1. although it has the same four fuel cells it only has two fill ports
in the middle position.
(Yak-9D has them inboard and middle)
2. due to a de-skinning problem (that also effected the La-7) the wooden skins were made a little thicker and a thicker layer of glue was applied.
it was discovered that inconsistent batches of the components of the glue caused them to separate when exposed to heat and moisture.
some pilot's lost their live to this problem

this M wing was retro-fitted to some Yak-9T's that were found to have bad wings,later machines were manufactured with them already in place.
as for the Yak-9K...possibly!
the production period for these two types do overlap...

as for your other technical questions... I will have to find my A.T. Stepanets documents to be sure.
he was senior test engineer at LII at the time so he was very familiar with these planes.
I don't believe the M ever got the PF2, AFAIK just the Yak-3.
it did get a new propeller and spinner. (the quickest way to spot the differences)

[Jens]

My Materials about soviet planes are at home, so i cant answer properly, but what i know from mind is:

Yak-9M indeed had the bad perfomance, all sources confirm that. It was like a mass plane for great parts of fighter air force. In a way it was also a multirole plane

[kurlannaiskos]

Originally Posted by Jens

My Materials about soviet planes are at home, so i cant answer properly, but what i know from mind is:

Yak-9M indeed had the bad performance, all sources confirm that. It was like a mass plane for great parts of fighter air force. In a way it was also a multi-role plane

please don't make the same mistake I did when my post last night was from memory...
that's the first thing to go.

according to another source I checked the Yak-9M did indeed start receiving the VK-105PF-2 beginning on October 1944.
the only test data I can find states that in December 1944 a Yak-9M was tested at NII and found to weigh 3,095 KG and could fly at 528 KM/H at sea level and 573 KM/H at 3,750 M

the Yak-9M is a follow-on to the Yak-9D , it fulfills the same role.

[Jens]

But these are bad perfomances, a Yak-9D run ~540 @ SL and a Yak-3 567 @ SL. Even a Yak-7B with PF2 was faster.

[yogybär]

- Concerning the radiator: It was possible to use it in "Auto"-mode, so that the pilot was relieved from that task
- 9M was integration of 9D and 9T into a standardized fuselage. Even higher mass production was the target here, not high performance.
- Enginewise, the SU had a problem anyway: No better V-engine (VK107), too late change from ASh82F to FN etc.

Jens, what kind of multirole was the Yak9M? IMHO, basically it was a fighter and maybe some were used for Reccon, but above that?

[kolya1]

Many thanks for everybody's answers...

Originally Posted by Jens

But these are bad perfomances, a Yak-9D run ~540 @ SL and a Yak-3 567 @ SL. Even a Yak-7B with PF2 was faster.

An so did late series LaGG-3s.

Indeed, It doesn't seem very high, I wonder whether the example tested was a M-105PF or M-105PF2-engined one...

Anyway, the Yak-9U had better aerodynamics, even with a M-105 engine, it would probably have been a better solution, I wonder whether they didn't produce it more because of industrial problems or lack of metals, or because they were simply waiting for the VK-107...

[kurlannaiskos]

what is your point in all this?
you are confusing me.
are you asking for a set of specs or the reasons for it's creation and experience in it's use?

the info I have does not state if it is PF or PF-2.
with those stated numbers my guess would be PF
but, if the PF-2 was so much better then why not test it too?
also if the M were in production from April '44 why not test it till December?
if this plane had such poor performance then why would they build 4,239 of them from April 1944 to May 1945 ?

[kolya1]

Originally Posted by kurlannaiskos

if this plane had such poor performance then why would they build 4,239 of them from April 1944 to May 1945 ?

That is exactly where my interest is.

I had read (on the net, because books didn't help me much on this) figures similar to the ones you just mentioned (except that at sea level they mentioned 518 km/h instead of 528), and found them very low for 1944.

So, I wondered : 1- whether the performances were really so poor, and if so, 2- whether they concerned the majority of production airplanes.

Which finally leads me 3- to your question that I quoted above.

Your answers were very helpful in that they seem to confirm the low performance figures, and this makes the other questions all the more interesting...

Kolya.

P.S. : I also found it puzzling that this version of Yak-9, while being the most produced of all, is also AFAIK, one of the least documented ones.