Perhaps I can help explain this report.
I've previously posted about STOBAR take off performance limitations - even the Chinese Navy went public with their problems. Perhaps it might help to recap and explain why STOBAR has these problems.
The answer lies in how different types of aircraft can use a ski jump. A powered lift aircraft (e.g. Harrier, F-35B) has the ability to vector its engine thrust through a range of angles from right aft to vertical. That means that it can leave the end of the ramp well below wing borne flying speed by using jet thrust, and indeed just below jet borne flying speed by using a ramp - and this is the key to the performance gains.
A powered lift aircraft will leave the ramp with a positive rate of climb, and increasing speed. Rate of climb will start decreasing on exit (remember the aircraft is below flying speed), but the rate of decrease will be slowed by suitably vectored thrust, plus increasing wing lift. Note that the angle of the jet thrust can be optimised independently of the wing's angle of attack. At a point some way out from the ramp exit (around a kilometre), rate of climb will reach a minimum, (the Harrier used 400 feet per minute) and the aircraft will climb away until it can go to full wing borne lift. So, it's climbing all the way from ramp exit.
Powered lift aircraft also have very high power to weight ratios to be able to land vertically. That gives them good power to weight ratios even when fully loaded.
Finally, powered lift aircraft have flight control systems that work down to zero airspeed (e.g. Harrier reaction controls). That mean that the aircraft is fully controllable right through the launch and fly out.
All these factors mean that a powered lift aircraft can launch from a ramp with a given deck run more slowly, so with more payload and/or fuel than from a flat deck STO. It also means that ski jump launches are a very safe and low workload affair, especially at night.
STOBAR aircraft launches have a much more restricted envelope. The aircraft has to launch at a speed and weight at which wing lift (plus a component of jet thrust from high exit angles of incidence) is sufficient to keep it up and accelerate it. Of course, as the thrust can't be vectored, the only way to increase its vertical component is to pitch up - that increases drag and will at some stage reduce wing lift.
Minimum STOBAR launch speed is usually driven by the need for the flight controls to work - with a fixed deck run, that means another limit on take off weight to get the necessary end speed. The STOBAR Typhoon proposal eventually had to include an additional reaction control system to address the issue. Of course, that in turn reduced engine thrust, so.....
All these factors mean that STOBAR aircraft can't launch at anything near MTOGW. It's notable that every video I've seen of STOBAR launches appear to show light weapon loads, and I would hazard a guess that fuel loads are also restricted. I've also been told that some STOBAR launches involve allowing the aircraft to lose height (not just rate of climb, actual altitude) soon after ramp exit, and then to recover back to a climb some way off. That's got to be tasty at night.
This STOVL/ski jump stuff is, as with most aspects of naval jet aviation, harder than it looks and also amenable to damn good ideas. Us Brits have had quite a few, and the ski jump is just one of them.
Hope this helps,
Best Regards as ever to all those flying off the deck, however they do it,
Engines
Last edited by Engines; 30th Nov 2016 at 19:02.