Was there produced Il-4 "strielka" - with sloped leading edge?

[JWM]

Hi,

In a Polish monograph of Ilyushin Il-4 (DB 3/DB 3F) there is said that the 1944 production (~700) has sloped leading edge of external parts of wings - so similar like late variants of Il-2, to improve stability. I have not found any confirming of this info besides those drawings

https://www.ebay.com/itm/PLS-72039-1-72-Ilyushin-DB-3F-Il-4-bomber-Full-Size-Scale-Plans-A1-format-page-/282401572270

however here the description is that the one with sloped leading edges was a single machine with wooden wings and rear of fuselage.

Please, is  there any expert on Il-4 to clarify this (confirm/denide)?

Regards

J-W

 

[Jure Miljevic]

Hello Jerzy-Wojtek

I am hardly an expert on Il-4, but after a brief search through a special edition of Авиация и космонавтика magazine Дальний бомбардировщик ДБ-3-Ил-4 I came across the same drawing. It represents the one-off machine No 2314, built by Zavod No 23 and evaluated in 1942. According to an accompanying table her engines were of M-88B type, she had higher empty and take-off weights and significantly longer range than standard Il-4 (4265 km compared to 3300). There is probably more, but unfortunately I am an awfully slow reader of texts, written in Russian alphabet.

That E-bay drawing looks very much like those usually published in Ukrainian aviation magazine Авиация и время. If you have an access to this magazine, try to find the number in which it had been published. Cheers

Jure

P.S.: Found it! Авиация и время 1998-1 and an accompanying article also includes two photos of 2314.

Edited July 7, 2019 by Jure Miljevic
P.S. added

[JWM]

Thank you Jure!

5 hours ago, Jure Miljevic said:

P.S.: Found it! Авиация и время 1998-1 and an accompanying article also includes two photos of 2314.

I have found this article in net and downloaded it! I will go throught it...

Regards

J-W

 

[Massimo Tessitori]

Hi, 

interesting question. I have compared some photos years ago, and I am prone to agree that Il-4s built in 1944 had sloped metallic outer panels.

Some photos show the sloped edges indeed, but it can't be excluded that the photos show some of the few wooden wings Il-4s whose prototype is well photographed.

An important Soviet book described the modification with sloped metallic wings as it was introduced in 1943 to compensate the moving back of the cg due to the addition of a man for the ventral gun, and increase the thickness of the wings to add further fuel tanks.

The thing is yet in doubt. It was discussed on Sovietwarplanes years ago. Perhaps one can have a further look to existing photos to disclose planes of 1944 with arrow wings. From photos on the ground, they are very difficult to distinguish.

At present time, I think that none dared to draw a 3 views drawing of an Il-4 with sloped metallic wings.

Regards

Massimo

[Learstang]

According to research I did for my forthcoming book WARNING: SHAMELESS SELF-PROMOTION called 'Soviet Bombers of the Second World War', I concluded that from 1942 some Il-4s were produced with swept-back mainly wooden wings. The wing sweep back was done, as Massimo states, to deal with the addition of the ventral gunner (similar to what happened with the Il-2 with the addition of the rear gunner and the swept-back 'arrow' wings). The wings, like the 'wooden-wing' Il-2s, still had metal spars, but the rest of the outer wing structure was wooden. I was unable to determine how many were produced or even how long this version was produced. The matter, even examining Russian material, is not very clear. Looking at those drawings, however, it appears that the wings are supposed to be wooden, with metal spars, which agrees with the material I have read.

 

Best Regards,

 

Jason

Edited July 8, 2019 by Learstang
Additional comment added.

[JWM]

12 hours ago, Massimo Tessitori said:

Some photos show the sloped edges indeed, but it can't be excluded that the photos show some of the few wooden wings Il-4s whose prototype is well photographed.

An important Soviet book described the modification with sloped metallic wings as it was introduced in 1943 to compensate the moving back of the cg due to the addition of a man for the ventral gun, and increase the thickness of the wings to add further fuel tanks.

The thing is yet in doubt. It was discussed on Sovietwarplanes years ago. Perhaps one can have a further look to existing photos to disclose planes of 1944 with arrow wings. From photos on the ground, they are very difficult to distinguish.

 

12 hours ago, Learstang said:

The wing sweep back was done, as Massimo states, to deal with the addition of the ventral gunner (similar to what happened with the Il-2 with the addition of the rear gunner and the swept-back 'arrow' wings). The wings, like the 'wooden-wing' Il-2s, still had metal spars, but the rest of the outer wing structure was wooden. I was unable to determine how many were produced or even how long this version was produced. The matter, even examining Russian material, is not very clear. Looking at those drawings, however, it appears that the wings are supposed to be wooden, with metal spars, which agrees with the material I have read.

Dear Massimo and Jason,

Many thanks for your comments. I think there isalso  a difference in wings in aileron/flap span  among different production series. Maybe it is related one to another ?

If you have Squadron on Il-4, the two right photos on page 31 (especially that od staring machine with white "78") are the only one I know on which someone can feel/guess that wings leading edge is a bit sloped... 

Regards

J-W

 

 

[Learstang]

It's hard to tell on those photographs for certain, J-W. That's a problem even with the Il-2 arrow - from certain angles it's very difficult to distinguish the swept-winged variant from a late model straight-winged variant. That top right Il-4 does appear to have a 'kink' in the leading edge, though. Straight-winged or swept-winged, I just wish someone would come out with a new injection-moulded kit of the Il-4 in 1/72nd scale.

 

Regards,

 

Jason

[JWM]

There is something deteiled about it in the article on Ilyushin Il-4 in Aviatsia i Vremia from No 1 of  1998! Thank you @Jure Miljevic for qoting this article. It is available in Net here:

http://hobby.rudic.ru/zhurnal-aviacija-i-vremja

Namely, in a is description of construction of wing it is said, that (my translation from Russian):

"On some series of Il-4 instead of all metal outside parts of wings  covered with playwood were installed, which were different also by its geometry. In particular the slope angle was increased by 3 degree, the dihedral was 5 degree 40 minutes (instead of 4 deg. 40 min.)  and profile was NACA 230 (instead of Clark-YH 15)"

 

Unfortunately only "some series" and no clear if wing span was exactly the same and if  aileron/flaps were different? And next detective work is to distinguish now on photos which kind of wing is installed on given airplane!

Regards

J-W

 

Edited July 9, 2019 by JWM

[KRK4m]

So mating together these 3 sources gives the following idea:

- the plywood-covered (although still with metal spars) outer wings had 3 deg. more leading edge sweep, 0.92 deg (5*40' instead of 4*45') more dihedral and NACA airfoil instead of Clark (source: Avyatsya i Vremya drawings)

- the wing area and the fuel capacity of arrow-winged Il-4 was increased with no increase in wing span (figures in table accompanying the drawings mentioned above)

- since 1944 the wing flaps area was increased (Squadron Signal booklet, A+V drawings)

However the question how many of these arrow-winged Il-4s were built remains with no answer yet...

Cheers

Michael

[Massimo Tessitori]

Hi, 

the plane in Moscow seems to have a sloped wing. 

https://airmuseum.ru/galereya/vy-stavka-tehniki-na-poklonnoj-gore-g-moskva/nggallery/image/il4_1

One has to check if the plane was mounted in correct way or was not manipulated. I think to remember that its wings were cutten to transport it. 

Regatds

Massimo

[Learstang]

Michael, I believe that's a good summary. Massimo, since this Il-4 was restored from a wreck, it's hard to be certain about the accuracy of the restoration, although the fuselage appears to have been well-restored. Looking at some photographs I have of this aeroplane, I noticed that the wingtips are slightly blunt. In the photograph I have of the wooden-winged Il-4 'arrow', the wingtips appear to be slightly blunt also, although perhaps I'm seeing what I want to see.

 

Regards,

 

Jason

[Massimo Tessitori]

Hi, 

for what I remember the wing is metallic. Anyhow some observation should be made on the real plane. Even if they have cutten the wings, it's difficult that they remounted them in sloped position, eventually they could have easily missed the dihedral.

Regards

Massimo