"Guy Alcala" wrote in message
. ..
John R Weiss wrote:

"Guy Alcala" wrote...

When you come to a F-18 / F-35 STOVL loadout, there could be a LOT of
F-18
tankers supporting 1+30 cycles for the F-35, or the cycle times will
be
reduced
to 1+15 or less.

Don't see why. The F-35B will have considerably more internal fuel
than an
F-18A-D
with similar weight, a single engine and no need for 3-5,000 lb. of
recovery
fuel
reserve. Marine profile mission radius (KPP) is 450nm from a 550' STO
(590nm
for
the USAF F-35A mission profile; 600nm for the USN F-35C mission
profile), with
a VL
bringback of .2 x 1k JDAMs and a pair of AIM-120s, plus reserve fuel.

What are the comparative thrust and specific fuel consumptions of the 2
airplanes' powerplants?

Fuel burn for F35 in landing configuration is said to be close to double
that of the AV-8.


Actual thrust numbers, SFC, BPR, pressure ratio etc. are all still
unavailable for
the F135 and 136; basic layout (turbine and compressor stages) is about
all that you
can find. P&W & GE both just say "40,000 lb. thrust class." I've seen
somewhere
(but can't find it) that Rolls-Royce mentioned ca. 34,000 lb. dry, 56,000
lb. wet
for the F136, but that may include the lift fan. The F136 is based on the
F120
design, and IIRR that engine was variable-cycle. The use of the lift fan
eliminates
the Harrier problem of needing a very high bpr to generate sufficient lift
for VTOL,
screwing the SFC in throttled back cruise or at high CAS.

As to the F-18A-D, off the top of my head F404-400s were rated at about
10,800 lb.
mil (or maybe that was the internal fuel), 16,000 lb. A/B, with the -402
boosted to
17,600 lb. max. A/B.

What will the fuel burn be for a typical approach and
vertical landing for the F-35?

Considering how low it was for the Harrier, with the F-35B being easier to
control,
it should be minimal. Harrier transition and landing takes a minute (or
two at the
outside), with max. fuel burn (wet) of 220 lb./minute for the -406, and
presumably a
bit more for the -408. The F-35B probably has between 50 and 100% more
power in the
hover, with a newer engine design and using an optimized lift fan plus a
less-optimized core engine, so you can make your own estimates.

Why will there be a significantly lesser fuel reserve requirement?

Boarding rates are very high -- Unless somebody takes their own waveoff,
"foul deck" usually means the jet is held in the hover abeam the intended
landing spot until the spot is cleared.


Because there's no little need for multiple looks at the deck -- no
bolters, no
fouled decks. Enough fuel for one go-around seems to be about the max
required, at
least in wartime. Peacetime requirements will undoubtedly be greater, but
still
considerably less.

Will the
bingo fuel requirement be less for a STOVL airplane than a CTOL
airplane?

Are you referring to bingo fuel to the beach, or mission bingo? You have
little
need for the former. In Sherman Baldwin's book "Ironclaw," he describes
the Midway
trying to get a single F-18 back on board at night just prior to DS, while
they were
running at 30 knots or so, directly towards Iranian territorial waters.
IIRR they
tanked the guy a couple of times, and spent an hour getting him aboard.
Just about
the time they were going to have to bingo him because they had to change
course to
stay out of Iranian waters, they got him aboard. None of that would have
been
necessary if he'd been flying a STOVL a/c. The Midway could have been
cruising
along at any speed above steerage way, and he would have recovered on the
first
pass.

For mission bingo, it has been less for Harriers. As John Shinal alluded
to, during
the Falklands war, the CO of 801 Squadron told his pilots that if they
landed back
on board with more than 800 lb. of fuel from a CAP mission, he'd "put his
boot up
their arse." Average fuel at land on seems to have been under that, in
the 600 lb.
range, with several landings with 400 lb., and in at least one case, when
the
visibility was perhaps 50 feet in fog and the pilot in question made one
missed
approach and then had the carrier shine a spotlight straight up,
descending
vertically next to it and landing on without ever seeing the deck or the
island (or
they him), 200 lb. Flight ops had already been shut down prior to his
recovery.

Over Bosnia, USN F-18s were originally operating with 5,000 lb. landing
reserves,
subsequently cut to 3,500 lb. to increase weapons bringback. Even being
really
generous, it's hard to see why an F-35B would need more than 2,000 lb.
landing
reserve. Night landings, even Case III, just aren't the same
white-knuckle affair
that they are when you have to trap.

I disagree with that last sentence Guy. Because Harriers use NVGs for
shipboard takeoffs and landings, STOVL Night Case I is dramatically
easier -- when conditions are conducive to NVG ops. Night Case III around
any ship is a white knuckler regardless of what you're flying. It is no
different in the AV-8 -- in addition to all that wonderful glideslope and
course control, you get to manually control a progressive deceleration to a
hover. It is THE most difficult thing to do in the Harrier -- bar nothing.
The F35 should change that due to automated systems that shift some of the
cockpit tasking to the machine.


The F/A-18 hasn't met fuel specs yet, to my knowledge. The A/B/C/D
never met
the original requirements, and the C/D specs were "adjusted" so much
from the
original requirements that it is almost impossible to make an
apple-apple
comparison.

The F-18E/F supposedly meets the original F-18A spec. The threshold
radius for the
F-35B is greater than that.

So far, I believe the combination of cost and performance requirements
for the
F-35 are hopelessly optimistic...

Aren't they all? But they are paying a lot more attention to cost
ceilings on the
program than they've done in the past; that is indeed one of the prime
drivers.
We'll just have to see how the performance falls out.

Guy