Guy,

Great share. Thanks.

--
Mike Kanze

"Do witches run spell-checkers?"

- Old word processing joke


"Guy Alcala" wrote in message
. ..
Mike Kanze wrote:

Guy,

Thanks for reminding the more forgetful of us about Point Option. This
was
what I had in mind when I answered Al Dyke with the "DR" portion of my
response. In fact, that's what it is - a DR problem with a specific
name.

See my reply to W.D. Allen.

With GPS/INS, everyone knows where they are to within a few meters,
assuming everything's working.

Of course it helps mightily if you have a reasonably accurate fix from
the
ship before you launch - unlike the pre-launch (and pre-GPS) 40
nm-in-error
"fix" that the CORAL MARU gave a VA-95 crew during its 1975 cruise. (Sea
story previously shared in this NG.) If you don't know from where you
started, DR by itself isn't going to get you home.

Sure isn't.

Worse if you THINK you
know from where you started - like the VA-95 crew, but are wrong and
don't
know it.

FWIW, here's an account of 1980s tech, by a Sea Harrier on a single-ship
night
CAP mission from HMS Invincible during the Falklands War. SHARs didn't
have a
real INS at the time, they used a twin-gyro nav platform that was easier
to
align on board:

"As soon as I was turning and burning, I put the radar to 'Standby' to
warm up
and called 'On deck'.

"'Roger. Ship's head is 340; now, now, now! Your position is 55 deg. 05'
W and
51 deg. 12' S.' The communication link between Flyco and aircraft on deck
was
via a wire, not radio.

"The information passed was necessary for aligning the NAVHARS platform.
My HUD
had already showed me that the a/c was pointing 2 deg. to the left of the
ship's
centerline, and so on the third 'now' I entered 338 deg. into the system.
Geographical coordinates were also entered, and I was ready for launch . .
. .
[he flies an uneventful mission, actually the first night of the war while
the
Vulcan bombs Port Stanley airfield]

"Recovering to the ship was going to be a little different from usual, the
difference being that none of the ships would have any lights on at all --
including Invincible. The carrier would only switch on the dimmest deck
lighting when the Sea Jet [SHAR] was about 200 yards from touchdown.
Then, as
soon as the wheels touched the deck, it would be off with the lights and
back to
darken ship.

"I descended to low level and, using my NAVHARS, navigated through the
briefed
safety lane to where I expected Invincible's marshalling area to be.
Switching
my radar to transmit, I found what I thought was Invincible amongst the
many
contacts on my neat green radar display and called the Approach
Controller. '003
estimating 6 miles on the approach. 800 feet, gear down and locked, 2200
pounds.' I had stacks of fuel.

"Roger, 003, I have you at 5 1/2 miles. Ship's head 320. Wind over the
deck 18
knots."

And so on to recovery. And here's a night approach in poor weather a bit
later
in the war:

"By the time I began my final descent towards the Carrier Group I was back
amongst the clouds. They were massive and very turbulent. After I had
descended to low level and was running in to the expected position of the
ship
via the safety lane, I called, '004, on the way in. Estimating 280, 25
miles.
Over.'

"Tony was immediately on the air. 'Roger, 004, read you loud and clear.
I have
no contact on you, repeat no contact. Clutter from snow clouds too
intense.'
He was concerned. Good old Tony; there's a man you can really trust.
He'd do
anything to get his pilots down safely.

"'Roger. I'll conduct my own approach and call out my ranges to go.' I
was
feeling confident thanks to two important facts. Firstly, when Invincible
gave
a ship's estimated position for the recovery of aircraft, you could bet
your
pension on her being in that position when you returned from your flight,
especially in bad weather. So I was very sure in my mind that I could
find the
deck using my NAVHARS information. The second fact was that I had
practiced
self-homing to the deck on many occasions, and we had also carried out the
trials on the software for self-homing when ashore in the Trials Unit. It
was
no higher workload for the pilot than following instructions from the
ship's
precision approach controller.

On my radar screen, the Invincible 'position destination marker' that I
had
selected on my nav computer sat less than 2 miles from one of the ship
contacts
in view. I had already programmed the 'marker' with the ship's
pre-briefed
recovery course and speed and was happy to see it was holding good
formation on
the contact nearest to it. That had got to be Invincible -- I hadn't
enough
fuel left to make any mistakes. There was enough for one approach only.

"It was a simple matter to update the radar marker's position by fixing
the
radar onto the contact. The 'Self-Controlled Approach' programme in the
NAVHARS
computer software was provided so that pilots could safely carry out their
own
precision approach to a chosen destination. My chosen destination was the
ship,
and as I lined up 5 miles astern of what I thought was Invincible, I
selected
the precision approach mode on the HUD. I also locked the radar onto the
ship
to keep the 'destination' information as accurate as possible . . .

"'Five miles on the approach.' I called.

"'Roger, still no contact.' Tony must be sweating buckets down there. I
was at
800 feet and the world outside was black. Approaching 3 miles I prepared
to
commence descent. The radar was firmly locked on to the contact ahead.

"'Three miles.'

"'Still no contact.'

"Was I on the right ship? I began to wonder as I started down the slope.
My
jet was being tossed around a bit by turbulence from heavy clouds, which
would
certainly account for the clutter Tony had mentioned. There was no other
course
but to wait and see.

"'Have you now at 1 1/2 miles. On the glide slope.' Tony sounded
relieved. I
was relieved.

"Tony continued with his calls all the way to half a mile. He had passed
the
wind over the deck as 40 knots gusting 50. It felt like it in the
cockpit,
too. The buffeting increased as I got lower.

"'Half a mile.' My head-up information said the same. I delayed
selecting
hover-stop for a few seconds because of the strong head-wind, then nozzles
down,
power going on. At a quarter of a mile I called 'Lights'. And there,
behind
the radar cross in the HUD, appeared the ship's island. As usual the
cross was
just about on Flyco. Radar off and concentrate on controlling the jet.
As I
was moving sideways over the deck from alongside the wind backed through
30
deg. I ruddered the nose into it before settling onto the deck with an
uncharacteristic thud.

"'That's my excitement over for the night,' I thought. It was 0400 hours,
and a
long day lay ahead."

For anyone who's interested, all the above is from "Sea Harrier over the
Falklands: A Maverick at War," by Commander (ret.) Nigel 'Sharkey' Ward,
DSC,
AFC, RN.

Guy