Chad Irby wrote:

:In article ,
: Fred J. McCall wrote:
:
: Trapping at max take off weight is not the usual thing. I would think
: that the ability to do so would indicate that either the max take off
: weight was held unrealistically low or it's going to be difficult to
: trap.
:
:Max takeoff weight for the F-35 is about five tons lower than the
:F-18E/F *normal* attack mission takeoff weight. They get huge weight
:savings from not having to haul around an extra two or three tons of
:fuel (plus tanks).

And you obviously miss the point of my original remark. Why am I not
surprised by that?

Total gross takeoff weight of any particular airplane (or even gross
'bring back' weight) are not the issue. The issue is a particular
airframe's gross takeoff weight compared to its maximum 'bring back'
weight, not the trap weight of any particular airframe. I'll try to
explain, just in case you actually read something someone else said
for a change.

Let me put it like this. Generally, max takeoff weight is a function
of low speed lift and power and how hard the catapult can throw you.
You try to make it as large as possible compared to dry weight, since
that way more of your weight is expendables that you aren't going to
bring back.

'Bring back' is a different issue. In an ideal world, you'd like to
be able to take off with max internal fuel plus max weapons up to max
gross takeoff weight and get back down with the same weapons and
something like 25% of max internal fuel. If you size structure to be
able to trap at max gross takeoff weight, your dry structure is far
heavier than it needs to be, which makes you a much less efficient
airplane in actual operational use.

In the case of the F-35C (using weights from FAS), what one gets is
some 24,000 lbs dry weight plus 16,000 lbs max internal fuel plus some
10,000 lbs of ordnance (for a total of 50k lbs max gross takeoff
weight). Your earlier claim is that the F-35C will be able to trap at
this weight. However, what I would expect is that at most it would
only be able to trap at around 38k-40k lbs, some 5 tons lighter than
your claim. If it can actually trap at unnecessarily heavy vehicle
weights (you can always vent fuel if you need to get right back down
after launch), then the dry structure of the vehicle is too heavy and
could be lightened, allowing more ordnance to be carried.

[Actually, I would expect it to be even 'worse' than that, as trapping
with that much ordnance is practically always going to be unnecessary,
since if you're launching with that large an ordnance load you ARE
planning on leaving it somewhere - for 'patrol' flights you'd carry
much less ordnance). I quoted 'worse' above, because it isn't,
really. It just means that the weight of structure has been properly
judged to give the most useful airframe possible. Your position seems
to say that they've made the aircraft structures unnecessarily heavy,
which I find dubious thinking at best.]

Oh, as another small hint, max takeoff weight may be 50k lbs, but if
they launch with max ordnance (17k lbs) and short fuel, the first
thing they'll do is tank up at the rally point outbound. So your
earlier claim really amounts to being able to trap with MORE than max
takeoff weight, which is profoundly silly.

Take your time and think it through for a change.

--
"Some people get lost in thought because it's such unfamiliar
territory."
--G. Behn