Vickers Viscount : Are those engines bent?

[JuanitaF]

Hoping there might be an engineer with intimate knowledge of the Viscount who can help clarify a little confusion around the engine angle.
All the Vickers drawings seem to indicate the engine centrelines are parallel to the fuselage waterline, although they don’t actually specify the angle anywhere.

Looking closely at photos it appears the engines have a negative angle of somewhere around 0.5 to 1.0 degrees on most models. Some later aircraft appear to have the engine parallel to the fuselage waterline, such as V 808 (G-BBDK) and V 806 (G-AOGY).

I can’t work out if this is an optical illusion created by the shape of the cowls, or whether there was an angle to it.

Hoping someone can set me straight.


Juanita

[Terry Dactil]

Maybe it indicates the number of heavy landings :E

[JuanitaF]

:-)
Or flex in the wings!

[India Four Two]

I've noticed same thing on ATRs.

What's the reason for mounting engines with the thrust-line tilted downwards?

[PAXboy]

Angle of attack?

[DaveReidUK]

There seems little doubt, looking at the many photos of Viscounts on the Net, that the thrust line is not the same on different marks of the aircraft.

[Terry Dactil]

I always had the idea that the aircraft designers had a design cruise speed with the wing around 3º AoA, then tried to build all the other bits pointing directly into the wind for minimum drag

Maybe it was due to rising fuel costs at the time leading to adopting a slower, more economical design cruise speed.
Changing the wing/fuselage angle on later versions would be a major item, but re-alighning the engines would be fairly easy.

[Midland 331]

No CAD/CAM back in the days of men in brown dustcoats in Weybridge or Hurn, hand-crafting against drawings.

I've read that the difference in handling between members of the BMA Viscount fleet was marked.

G BMAT was a sort of "cut and shut" from G-AZLT (written off at Leeds) and G-BAPE (I think), put together with care by the lads at the Castle Don. hangar.

By luck or judgement, I heard that it handled better than any on the fleet.

And those nodding nacelles! As a youth, I used to think they were about to drop off.

[megan]

I agree in some photos the aircraft do seem to have the thrust line pointed in a downward direction, optical illusion or not I don't know.

It may be that the centre of gravity is above the thrust line, therefore an increase in power would tend to make the aircraft pitch up. The thrust line is then pointed down as a means of controlling the pitch up.

Just a blind guess, look at a photo of a T-28 to see a very prominent downward pointing thrust line.

As john_tullamarine says elsewhere, "Design is a compromise to make a lot of conflicting task and systems needs all fit and work reasonably well together.

Unless you have a list of all the relevant considerations which went into the design configuration definition exercise, there is no way you can infer much at all with any real confidence".