Junkers Ju 52/3m engine mounting angle

[GrahamB]

Over recent weeks and months I have been delving into the complex history and development of the Luftwaffe’s incredibly resilient and hard-working Junkers Ju 52. Reference books on this aircraft are amazingly inconsistent in the details of the structural changes and camouflage (see my other posting) although the recent Classic Colours Transporter has got very close. There is one major feature that I think is wrongly presented in almost all cases: a Heller 1/72 Ju 52 on my workbench seemingly has deformed outer engine cowlings, so that the rear profile is not a perfect circle, as one might assume. Also, the cowling shape is asymmetrical, not what one would expect if the engine was mounted parallel to the swept-back wing leading edge. The consistent impression and presentation in illustrations and plans (e.g. Squadron/Signal, AirDOC, Profile Publications, Model Fan, Flugzeug Profile, Classic Colours ‘Transporter’ volumes, and even the RLM camouflage diagram itself!) is that this was the case – the radial engines were mounted parallel to the leading edge, giving them an outward cant of about 6 degrees. I was suspicious about this because I was not convinced by looking at many photographs (all photographs from a front angle of multi-engined aircraft will show the wing cowlings apparently divergent). As cameras do not have perception one has to account for the camera angle when interpreting photographs and using other features as a control. In the case of the Ju 52, the undercarriage is a useful guide. As is usual, finding photographs that would definitely solve the problem was difficult. Fortunately there is one in Squadron/Signal ‘In Action’, page 29 lower left of a Ju 52 floatplane. The camera view appears to be directly in line with the starboard engine nacelle but the cowling is clearly not aligned symmetrically but is angled inwards. On page 41 of ‘Transporter vol.1’ taken from behind and above, the photo also shows the asymmetric alignment and Heller’s cowling shape to perfection, as does the colour print on page 78. Other photographs in the references mentioned show this less well.

I think this is pretty convincing proof that Ju 52 3/m aircraft with BMW 132 engines had them mounted perpendicular to the line of flight. In fact, this is actually stated in ‘In Action’ on page dealing with the Civil Variant Ju 52/3m ge! It is strange how this has eluded everyone else – although Don Greer’s fine paintings on the book’s covers seem correct.

[edNorth]

Hi;

Outward cant was to reduce yaw if opposite engine failed, reducing or eliminating the need for opposite rudder trimming, and the CASA 352 indeed also had not round rear of nacelles, due to exhaust routing etc., also line was not straight viewed from side, cowling cord was thinner at bottom. I can not attach images, but I have them.

cheers
ed

[GrahamB]

Thanks Ed.

While you may be right in stating the design purpose of the outward cant, I think that the photographic evidence of BMW-powered Ju 52 aircraft was that this was eliminated. There is another excellent print in Classic's 'Transporter Vol 2, page 134. Again, the photographer was more or less in perfect alignment with the starboard engine nacelle, with the cowling fixed at a highly asymmetrical position and clearly angled inwards (relative to the wing leading edge). Other standard views from positions ahead of the wings do not show the outward cant that would be exagerrated if the observer was in front of the outer engines. Using the angle of the undercarriage (wheels) will show that the cowling front is parallel to them - it usually seen with an orientation between that of the wheels and the central cowling - which is what one would expect. Some photographs that imply that the observer was directly perpendicular to the front of the central cowling are the best - the outer cowling front is just visible, mirroring the slight apparent dispacement of the wheels, and certainly not showing the amount expected of the 5-6 degrees of backsweep of the wing leading edge.

Best wishes

Graham

[ArtieBob]

IMHO, after trying to make drawings from aircraft photos, it is very difficult to determine either linear or angular dimensions accurately. In the case of most WWII LW types the manuals are available, which should answer most questions similar to this one. I only have at hand the Kennblatt Ju 52/3m (see) g4e BIS g8e, g10e, g14e dated 27.4.1944. It seems pretty clear from the 3 view drawing that the propellor arc is parallel to the aft swept leading edge of the wing and is not perpandicular to the fore and aft centerline of the fuselage.

Best regards,

Artie Bob

[George Hopp]

Here is how Junkers saw this aircraft. From Teil 0 of the manual on the Ju 52/3m g5e.

[GrahamB]

Hi George,

many thanks for this - it looks as if I am on a hiding to nothing with this one, although I remain unconvinced but happy to retire hurt in the face of what seems overwhelming 'official' evidence and previous literature. If Junkers is calling the figure a 'g5e' then there is something wrong with previous accounts. According to Manfred Griehl in the Flugzeug Profile 24 (= english translation version Schiffer Profile14) the g5e was introduced in 1941, a transport version well after the time when Aunti Ju was a bomber with a ventral dustbin turret. Stapfer, Mau and Punka in the Squadron/Signal 'In action no 186) say 1939 was the year of production for this variant - again after the bomber role had been changed to transport. All a bit confusing. I suspect that the manual's drawing is only basic and generic.

Why I am tearing my hair out over this is a mystery!

Kia ora

Graham

[George Hopp]

I have noticed this with other a/c manuals. Once they draw up an a/c; unless it really changes, they just keep using the same drawing.

[pstrany]

Okay, the examples I will cite are from a Spanish version of the Ju 52, but I think they can safely be applied to most German-built aircraft as well.
Picture #1 will show that the nacelle and cowling ar indeed an odd (and misleading) shape. The nacelle is almost perpendicular to the line of flight, but the cowling does angle outward. The mating of the two is very strange, I had to stare at it a while to get it.
Picture #2 will show that while the center engine is perpendicular to the line of flight, the left engine does cant outward. This was shot from a distance with a zoom, which helps to eliminate the distortion found in close-up shots.
These pictures were taken of the Spanish-built Ju 52 at the US Air Force Museum in Dayton, Ohio.

Paul

[GrahamB]

Hi Paul,

thanks for the two photos! I can't say that they really help - the one from the rear of the nacelle could be interpreted the other way: the corrugations are parallel to the line of flight (fact) while the nacelle is slightly canted outwards (fact), probably at the 6 degrees to make the front end parallel to the wing leading edge (6 degrees backsweep) - the cowling is similar but not identical to the German BMW versions and to my currently biased mind appears aligned in with the line of flight. Perhaps its asymmetry leads to the misperception and is what got me interested in this aspect anyway.

The second photo merely shows what would be expected if photo is taken ahead of the outer cowling - note apparent angle of the undercarriage. Maybe the slight angle involved (6 degrees) is just not resolvable with this photographic material. I wish I could transport myself to an authentic Ju 52, with original engine mounting - perhaps it was capable of being adjusted according to trim requirements of the individual aircraft?

There are many more issues to do with the Ju 52's morphology (engine intakes/exhausts/de-icing systems particularly - many variations and combinations) that have been poorly dealt with in the literature, although the beautiful illustrations in Classic's Transporter volumes are almost (not quite) spot on.

Cheers

Graham

[ArtieBob]

Dear Graham,

I truly believe you are beating a dead horse. I looked through a few (approx. 200 photos) of Ju 52s. IMHO ( but over 60 years of looking fairly closely at aircraft of all types), the outboard engines are canted as every official drawing of Ju 52s I have seen shows. Please read my first post, it is very difficult to accurately measure (or interpret) linear or angular dimensions of aircraft from photographs. In the case of the Ju, in some photos the leading efge of the wing appears to be perpendicular to the direction of flight. This is not true, as IIRC. all versions of the Ju 52 have double tapered wings, but I believe the dihedral in the wings creates an optical delusion that makes it appear the leading edges of the right and left wing are parallel. Of course, since you don't accept any information offered thus far, one may then go and look at the example at the USAF museum and convince yourself .

Best regards,

Artie Bob