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Old 23rd Dec 2008, 20:42
  #2020 (permalink)  
Engines
 
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In discussing SRVLs for F-35B on CVF, one needs to appreciate the profound differences between this idea and trying it with Harriers on CVS (Invincible class).

Harrier can use partial nozzle braking (PNB) to quite good effect at higher landing speeds. The 10 degrees forward thrust, if used correctly, doesn't pose a major FOD issue at prepared bases, but it does make the aircraft lighter on the gear, and that is an issue. The Harrier is a fairly poor braking aircraft, as Nohoverstop correctly points out. Only 50% of the weight is on the main gears that only have a single set of brakes. Add in a wet surface. and the situation gets a lot worse. Directional steering on the Harrier is quite powerful (lots of weight on the front peg) , but it is not all that stable an aircraft directionally.

To get effective wing lift off a Harrier (especially the SHAR) you need around 80 knots plus airspeed. That probably raises the SRVL touchdown speed to around 60/70 knots, with the right wind and ship speed. At these sort of airspeeds, the Harrier is not an easy aircraft to fly, with marginal directional stability and VERY high pilot workloads to stay on a precision approach.

Finally, CVS doesn't have the space (lateral or lengthwise to foot of the ramp) required for SRVL in any normal configuration.

F-35B has a full tricycle gear, and I'd expect around 90% of the weight to be taken by the two main gears. Each leg has a very capable carbon fibre brake set, and a well sized wheel for braking. Finally, the brakes are controlled via dual redundant computer driven braking systems. However, it is not going to be a very effective PNB aircraft - only the rear nozzle can vector forward, meaning not all the thrust can help.

The 'B' has a LOT more wing than a Harrier. Likely SRVL airspeeds should be significantly lower than for a Harrier, reducing touchdown speed to the deck. Finally, CVF has much more space available for SRVLs - the deck area is actually quite close to the size of the USS Forrestal when she first entered service in the 50s.

Finally, the 'B' has a very advanced flight control system that should allow pilots to put it on the proverbial sixpence, reducing deck scatter and allowing touchdown much closer to the stern than for a conventional cat and trap approach. In the same vein, the propulsion system is going to be fairly 'Gucci', and restoring power for a 'bolter' won't necessarily depend on a big engine's spool up time.

Modern Elmo raises a very good point about the CVF deck layout. I've posted before that doing SRVLs axially is, in my view, not a good move as you end up rolling towards other stuff parked on deck, or the bottom of the ski jump, ruling put any bolter. CVF has the space to accommodate axial launches and angled recoveries, which in turn should allow the aircraft to perform a 'bolter' if required. (Note - two different versions were posted by 'GreenKnight 121' - the upper one is closer to the current configuration. Lower one is an old design).

As far as I know, there are no crash barriers on CVF. The JBDs have been shown on a number of pictures, they are there to allow greater use of the deck aft of a launching aircraft. They should raise and lower very quickly (~5 sec), so shouldn't get in the way of deck operations.

SSSETOWTF hits the nail on the head - F-35B SRVLs on to CVF are a totally different animal, and well worth looking at.
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