Design Questions

[Zen]

Not sure where to put this, hope those who know about aircraft design can help me here.

Some time ago Geoff B kindly let me see his copy of the 1963 RAE report where they examined four aircraft to meet AW406. The RNs requirement for a Sea Vixen successor.

At first I took it for what it claims to be, an unbiased scientific report that seems to suggest the UK should look at either a twin Spey powered Vg machine of a smaller RB153 powered VG machine.
It clearly poors a lot of cold water on the P1154 which is compared with those VG machines.

...

However there is also a 'reference' machine, a fixed wing aircraft with twin speys, and as I look at their data thats where I have come to be suspiciuous of this report.

For I suspect its deliberately scewed in favour of the VG machines and I can name several reasons why. In comparison of the Spey fixed wing and the Spey Vg I see discrepencies.

1. both VG machines have wings of 400sqft, but the fixed wing machine as a wing of 500sqft. While that helps with take off and landing speeds on the face of it, it raises the wetted area and structural weight of the fixed wing machine, masking the weight gains of the Vg machine.
A small wing produces less drag and requires less power to overcome it, while a larger wing raised the ceiling of the fixed wing machine it also slows it down.
Suggesting that one can burn less fuel to achieve the same speed, and that can result in a lower weight, a benvolent cycle in design terms, reducing drag, reduces fuel burn which reduces weight, which can reduce size and thus drag and so on.

2. both Vg machines have roughly 70% more bleed air taken from the engines than the fixed wing machine. 10.5lb/sec for the fixed wing, 17.5lb/sec for the VG types.
This has the effect of bolstering the low speed characteristics of the VG machines while masking a proper comparison. If the fixed wing machine had that level of blow over its wing, its take off weight would rise, while its landing speed would be lowered further.

3. there is tellingly no comparison of the scaled spey VG machine with a scaled spey fixed wing machine.

I find these discrepencies such that I can only suspect deliberate bias by the authors of this work to justify their desire to produce a VG machine. Clearly it was 'favour of the week', in fact of the decade if we're honest.
This report makes a exagerated case for the benefits of VG, which if they where perhaps more honest would show its gains are more marginal compared to the costs.

But it leaves me suspecting that a fixed wing machine can be designed to fullfill much of AW406.

[Zen]

If this is the wrong place to ask these questions could someone direct me to where I could get answers please?

[Geoff_B]

Zen

Good question as to where it should go possibly alt-history section.

As for the original question, it does appear rather biased, i have a feeling the fixed wing aircraft they are talking about is probably based upon the Phantom specs at the time as it was taken as a base line for the Sea Vixen replacement.

Couple that with Barnes Wallis's Swallow research with Vickers and the US propossing the TFX as the Phonton replacement and you can sort of see the bias of the period. However they got usurped by the even newer VTOL trend that really spoilt the whole oppertunity.

It would be interesting to see if Vickers had designed fixed wing variants of its VG projects they would need to be Mach2+ capable , so thin wings possibly coupled with the developments of the buccaneer wing technology to improve carrier performance.

I imagine they would probably have ended up looking like smaller sized Vigilantes, with an internal missile bay somthing similar to the fixed wing versoin of the UKVG that appeared a few years later.

Cheers

Geoff