Vickers Viscount engine geometry

[JuanitaF]

Hoping an engineer with intimate knowledge of the Vickers Viscount might be able to clarify a little confusion around the engine angle.
All the Vickers drawings seem to indicate the engine centrelines are parallel to the fuselage waterline, however, nowhere in the documentation I have found do they actually specify the engine c/l angle.

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.
I am currently working on a detailed drawing of the Viscount 700 & 800.

Hoping someone can set me straight.

Juanita

[DaveReidUK]

What is the point of starting a second thread on the same subject ?

Did you not like the answers in your earlier thread ?

http://www.pprune.org/aviation-history-nostalgia/589632-vickers-viscount-those-engines-bent.html

[Uplinker]

The point is nobody gave a sensible answer on that thread, that's why.

[JuanitaF]

I put this topic up again in this area because its a more technical section of the forum.
As Uplinker pointed out, I'd had no luck in the 'historic' section.

I have asked around both directly and via various forums and have drawn a complete blank...which leads me to conclude that there was no angle on the Viscount engines, they were parallel to the fuselage centre line.

The appearance of a negative angle angle in some photos must be an optical illusion, probably created by the shape of the cowl.

Problem solved, question answered by the lack of answers :-)

Juanita

[Chris Scott]

Whom you need would be the 1950 equivalent of our Owain Glyndwr. Don't think even he was in the design offices then. :eek:

PS: there's got to be some give in those nacelles. Seen them wobble in turbulence.

[peekay4]

If you haven't yet your best bet might be to contact the researchers / volunteers at Vickers Viscount Network (http://www.vickersviscount.net). If they don't know then no one knows.

[Major Cleve Saville]

I recall that the engines were noticeably canted down. Whether it is the reason for some of the Viscounts slightly stranger handling characteristics I am not sure but at top of descent it was normal practice to disconnect the autopilot before 'fuel trimming' the engines back as the autopilot could not cope with the subsequent pitch up with power reduction. This characteristic also seemed present in the flare when closing the thrust levers also gave a small pitch up (as did selecting 100% flap in the flare).

[DaveReidUK]

I have asked around both directly and via various forums and have drawn a complete blank...which leads me to conclude that there was no angle on the Viscount engines, they were parallel to the fuselage centre line.

Problem solved, question answered by the lack of answers :-)

On the contrary, you were told, in the other thread (and subsequently confirmed in this one) that:

the thrust line is not the same on different marks of the aircrafthttp://www.avgen.com/Viscount2a.jpg

http://www.avgen.com/Viscount3a.jpg

http://www.avgen.com/Viscount4a.jpg

Coming onto a professional forum to ask a technical question and then ignoring the responses seems a rather strange thing to do.

The appearance of a negative angle angle in some photos must be an optical illusion, probably created by the shape of the cowl.A visit to Specsavers, or the Australian equivalent, might be in order. :O

[Uplinker]

Why are you being so mean and insulting to the OP?

What you actually wrote was:

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.

......which is vague and does not answer the OP's question, which was:

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.
I am currently working on a detailed drawing of the Viscount 700 & 800.

Hoping someone can set me straight.

[boguing]

On the other thread Terry Dactil suggested that the engine incidence angle may have been changed.

I'm wondering if the wing incidence angle was reduced (either because it had an unplanned negative deck angle in some flight regime, or due to the fuselage stretch) and that re-levelling the engines was thought unnecessary?

[DaveReidUK]

I'm wondering if the wing incidence angle was reduced (either because it had an unplanned negative deck angle in some flight regime, or due to the fuselage stretch) and that re-levelling the engines was thought unnecessary?

Yes, that may well turn out to be the answer.

I don't pretend to be a Viscount expert (I've only worked on, and flown on, the 800 series but not the earlier marks).

I've seen various references on the Net to wing incidence being 2°30' and also 1°30' - though that might simply be the washout difference between root and tip.

In any event, those photos look more like a 2-3° difference in the thrust line when comparing the 700 to the 800 IMHO.

I do know that the 800 had a different tailplane incidence, not that that helps. :O

[boguing]

Looking at these pictures of the prototype and a 701, I can convince myself that the tip incidence is changed.

http://www.vickersviscount.net/images/Photos_Medium/100082.jpg

https://upload.wikimedia.org/wikipedia/commons/a/ac/Viscount701_CambrianAirways_Bristol.jpg

And, DaveReid, I think the tailplane is is nodding to your recollection.

[boguing]

Looking at these pictures of the prototype and a 701, I can convince myself that the tip incidence is changed.

http://www.vickersviscount.net/images/Photos_Medium/100082.jpg

https://upload.wikimedia.org/wikipedia/commons/a/ac/Viscount701_CambrianAirways_Bristol.jpg

And, DaveReid, I think the tailplane is is nodding to your recollection.