The thing with VLO is that it partially renders your weapons useless too.

.. and this claim is based on…?

A number of reasons. Some of which are:

– Better adherence to Mach-Area ruling.
– Variable contour (moving) LERX/forebody for body lift at higher alpha, which also contributes to a triplane longitudinal control system. It also will contribute to trimming the aircraft for subsonic and supersonic flight without a significant amount of trim drag and without reducing the authority of the primary control surfaces.
– Thinner fuselage making greater contribution to lift.
– The round PAK-FA engine nozzles have better propulsive efficiency than square F-22 nozzles.
– All moving vertical stabilisers.
– 3D Thrust vectoring.
– Wider lateral engine spacing allowing roll augmentation from thrust vectoring.
– Variable geometry intake ramps

Add the whole lot up, and each little bit better becomes significantly better. There are no doubt other things, these are just off the top of my head.

Compared to the F-22, Suhkoi have compromised the PAK-FAs VLO characteristics – so you shouldn’t be surprised that they have a better aerodynamic platform.

Not sure if that’s Mach 2 necessarily, because we don’t know the conditions.

For ISA day:

@ 0ft – Mach 1.74 [almost certainly structurally limited to lower speeds here though]
@ 10 kft – Mach 1.81
@ 20 kft – Mach 1.88
@ 30 kft – Mach 1.96
@ 35 kft – Mach 2.01

Chances are (well, to be honest, I would be astounded if it were not) its above 35 kft so it will be Mach 2 flight.

Picture of the T-50 “50” model at Le Bourget, (c) BerrouLana @ forcesdz.com
https://fbcdn-sphotos-a-a.akamaihd.net/hphotos-ak-ash3/1013416_170930406417984_724405952_n.jpg

I note the engine nacelles are not changing… or at least, no hint of them changing.

But then, if the cruising speed talked about earlier in this thread is accurate and also it alludes to supercruise, that is, Mach 2 non-afterburning flight, then it doesn’t really matter if anyone can see you from the back three quarters, ‘cos add that speed to the Flanker endurance and there is virtually bog-all the detecting aircraft can do about it.

As an aside, to back up the Mach 2 supercruising claim – I have seen figures for the AL-41F thrust at 118kN dry and 175 kN afterburning. Or a ratio of 1.48. The ratio of the speeds Berkut has reported is 2610/2135 = 1.22.

1.22^2 = 1.49

Anyone that knows anything about aerodynamics will quite quickly realise the significance of those ratios broadly tying up.

I know, but you assess the reliability of guidelines by accounting for extraneous factors.

The problem with using these kind of approximation techniques for an aircraft with unknown technology is the guesstimation of error bands.

Do you go with a straight tolerance on every major sub-assembly? Lets say ±5%, given 20 sub-assemblies of similar mass, your error band is now -64%,+165% for the sum of those sub-assemblies.

Or do you go with a standard deviation on each? i.e., there is a 95% chance it’s mass is X kg ±2kg . But then your back to a 36% chance of accurately estimating the sum of those sub-assemblies with an error band of ±40kg!

About all you can do, without going into detailed modelling, is ensure that each approximation equation is being applied for a job it is applicable to (i.e. don’t use a metallic mass calc. for a composite structure) then consider the numbers rule-of-thumb only. At least, until you can start to calibrate your accuracy by getting information on individual sub assemblies. Which is obviously quite difficult for a confidential program.

Tomcat, you may want to read up on the research papers by the chief engineer of J-20. The design is highly maneuverable and the theory well-vetted academically.

I have read that paper.

Aerodynamics have moved on quite a bit from just LERXs for higher alpha lift. The J-20 uses three root extensions of sorts, (1) at the air intake and (2) at the canard leading edge root and (3) between the canard trailing edge and the wing leading edge. I suppose you could include the additional wingtip vortex from the canard itself, which will pass over the wing. Unfortunately, none are coupled, which will dissipate strength somewhat and would tend to lead to earlier vortex burst.

It’ll dance, but I wouldn’t expect it to dance with a PAK-FA.

1. Greater importance of instantaneous turn rates over sustained turn rates

That is not something I completely agree with – yes, the response rate and maxima are very, very important, but if your energy bleed at high turn rates is poor, you will always be at a disadvantage after a few turns – in both aggressive and defensive maneuvering.

If simulators are so splendiforious, why bother with trainers ?

What else did I say? Hmmmm.

That is not to be confused with proving the tactics for the aircraft, nor is it the same as proving the doctrine.

Also, g-loading doesn’t exist in simulators, hence my line on the training suits [I realise now that post is a bit disjointed – I changed it a bit before posting and didn’t spot I removed my sentence about the g-loading].

Furthermore, not many airforces have the simulators of this level of sophistication and there will always be a degree of resistance from pilots to using more simulation time over flight time.