Shenyang FC-31 / J-31 Fighter Demonstrator

gelgoog said:

If you compare the specifications of the Russian air force MiG-35 and the naval MiG-29K you can also see that the MiG-29K has more wing area. In that regard it is similar to the F-35A vs C.

Given the MiG-29K or the Rafale M's specs I think the FC-31 has too small of a wing to be usable as a naval airframe. The wing area is too low. But I could be wrong since the fuselage of the FC-31 might provide more of a lifting body effect than a MiG-29 or Rafale based design. I would not be surprised if things like the landing gear were already optimized for the naval role in the FC-31 prototype. However the wings, those I think would need to be larger. Perhaps even foldable. The fact that the design is built using modern manufacturing methods might mean that both versions of the FC-31 could be more different than something like the MiG-35 and the MiG-29K which seem to have the same basic fuselage to increase parts commonality. You would preferably design a naval version to have larger fuel tanks to increase range. You would want a lighter airframe on the frontal aviation fighter, not strengthened for hook landings, so you can increase the combat payload.

A carrier fighter needs to support lower landing speeds and it also needs to have more range than a comparable frontal aviation fighter. Thus a higher larger area makes sense.
A frontal aviation fighter will put more emphasis in maneuverability. So you use a smaller wing area.

So I think China is making a design which they can sell to foreign air forces, might be purchased in limited numbers by the PLAN, or the PLANAAF in land based formations, and a modified version optimized for the naval role. This is the scenario which seems to fit the available information better in my opinion.

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Brumby said:

A carrier based aircraft must be capable of a lower landing speed and more precise flight control during landings than required for a land based aircraft. This is the reason why the F-35C has a bigger wing area than the F-35A. It requires that the aircraft has to fly in a controlled prescribed approach path some four degrees below the horizontal to the flight deck at a precise, not-to-exceed speed into the arrestor wire as the wires have a limiting load beyond which they will break. This is an extremely challenging requirement and drives the design of the aircraft. The standard USN approach speed is around 130 to 135 knots, which delivers stable approaches and minimum ‘trap intervals’ (essential when numbers of aircraft are being recovered) at a speed that the arresting cables and engines can cope with. This speed delivers precision approaches, so that the ship needs only three cables for reliable ‘traps’. It also allows the aircraft to cope with the ‘burble’, which is the area of turbulent air immediately behind the ship, through which the aircraft must fly. The four degree downward approach path minimises the ‘burble’ effects and ensures that the aircraft will not fly into the stern of the carrier if it is pitching. Finally, this approach allows the aircraft, should it fail to engage the wire, or suffer a wire or hook failure, to accelerate immediately and take off again (a bolter) within one second of touching the deck.

Deck landing into arrestor wires requires precise control of speed, aircraft attitude and glide path. Any diversion from the prescribed approach parameters can and does result in various undesirable effects:
a) Too high an approach speed can cause the hooked wire to break leaving the aircraft with not enough residual speed to take off again but too much speed to stop on the deck: resulting in the loss of the aircraft.
b) Aircraft attitude (the angle of attack that the aircraft wings are presented to the air stream) must be accurately controlled. Too high a nose attitude at the prescribed speed will cause the loss lift from the wing surfaces and the aircraft will rapidly sink towards the stern of the ship. Too low a nose attitude will result in an increase in air speed, giving the aircraft to much inertia for the arrestor wire to cope with – and the latter will break.
c) Maintenance of the prescribed glide path is necessary to ensure that the hook does indeed catch a wire. If you are too low on the glide path, the hook can bounce over all the wires (or you may crash into the stern of the ship. If you are too high on the glide slope, your hook will miss the wires.

In other words, the correct air speed, attitude/angle of attack and glide slope must be maintained in a stable fashion all the way down the approach path to the deck. This means that the inertia of the aircraft, both horizontal and vertical, remains constant to the touchdown point: there is no reduction in rate of descent of the aircraft (as with landing on an airfield) and the forces that the aircraft under-carriage has to contain are markedly higher resulting from any pitching deck and “ship heave”.

The prescribed glide path for deck landing is steeper than that experienced ashore. On land, the prescribed glide path is 3°. But the land is stationary. With the ship moving at up to 30 kn away from the aircraft on the approach, the deck landing sight it is set at 4° which gives the aircraft an approach path through the air of just 3°. If the ship’s deck is pitching 2°, this leaves only 1° of clearance between the aircraft flight path and the stern of the ship.

The design has to balance a landing configuration weight and at speeds requiring very advanced flight controls. I suspect the J-15 crashes are connected to these issues and probably requiring the design to be tweaked if it is at all possible. Bottom line is even if you can check off 99.0 % of the boxes but if the design doesn’t allow for a safe aircraft recovery you don’t have a design – period.

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latenlazy said:

Wing area isn’t calculated by the area of the wing excluding the body, but the area of the entire fuselage in between the wings.

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Totoro said:

I must say I am not getting much from that. Is it just a rumor? if so, by whom? Is it a more official statement? If so, whose is it?

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SinoSoldier said:

Could someone translate what Pupu-2012 is saying about the FC-31/J-35? Better yet, does anyone have the direct link?

View attachment 51170

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Air Force Brat said:

Actually wing area is calculated from the wing root fairings to the tips, it is a hard number, fuselage lift is measured as a value depending on chine area, airspeed, cg, vortex generation...

So when you figure weight and balance, all these factors including fuel load, fuel burn, cg changes with fuel burn? (which often mandate pumping fuel from one tank to another to maintain the aircraft within cg limits longitudinally and laterally)..., weapons, and how launching weapons also impacts cg...

I think your point that the F-31 generates far more lift when you add the "lifting body" effect into the total equation is true.... however wing area is a hard number, and does not include a numeric figure from the lift generating devices on the fuselage...

feel free to correct me if I'm wrong, but that is my understanding, that's why the F-35A produces and "ungodly" amount of lift in relation to its wing area, and no doubt that would also apply to the FC-31....

however the C does have a considerably larger wing and horizontal tail surface area.... the Navalized F-31 will likely follow suit...

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