How do carrier-based planes find the ship after a mission ?

Today, we primarily use Tacan. However, knowing where the boat should be is
always a good preflight brief item to write down on your kneeboard card.
You never know when the "cake dryer" needs that "common" part that seems to
exist in the guts of the Tacan system.(or the ACLS/ICLS). However, the next
generation of carrier is supposed to have differential gps-like signal that
is transmitted so that aircraft don't need to be in T/R on the new nav
system. I think the name is JPALS (joint precision aircraft landing
system?). Eventually, all ships that have aircraft flying off of them
would have JPALS retrofitted onto the ships. Of course, it, much like other
procurement items, may not come to fruition.

"Rich" wrote in message
om...
(Al Dykes) wrote in message
...
As an armchair admiral, I've always wondered how A/C in WWII knew how
to find the carrier after being away for a couple hours on a mission.
I assume the pilots were told, roughly, where the carrier plans to be,
but sh*t happens. I always assume the carrier doesn't broadcast any
radio signals.

How do they do it, today ?

Well, for WWII USN carriers, generally pilots got a "Point Option"
that would give them a general idea where their carrier was supposed
to be. Then it became a matter of sorting out the homing signal.
Presume the RN worked the same way as they had similar homing
equipment. Don't think the Japanese used homing signals.

Rich

"Mike Kanze" wrote in message
...
How do they do it, today ?


Probably using GPS.

"Al Dykes" wrote in message
...


How do they do it, today ?


In the late 70's, you just looked for the biggest cloud. The ship was
usually under it.

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.

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

--
Mike Kanze

"Do witches run spell-checkers?"

- Old word processing joke


"Guy Alcala" wrote in message
. ..
Al Dykes wrote:

As an armchair admiral, I've always wondered how A/C in WWII knew how
to find the carrier after being away for a couple hours on a mission.
I assume the pilots were told, roughly, where the carrier plans to be,
but sh*t happens. I always assume the carrier doesn't broadcast any
radio signals.

Surprised someone hasn't explained how "Point Option" works, but they were
typically given a mean line of advance and a mean speed of advance of the
carrier, e.g. 240/20 kts, and the point along that line where the carrier
expected to be at their ETA. So they'd fly to that point, then if nothing
was around, head back along the line of advance, and presumably the
carrier would be within a few miles of the line. This allowed the carrier
to maneuver relatively freely, provided they made good their mean
course/speed. Point Option generally allowed considerable time for
detours, to allow the carrier to still make it barring major damage or
attack.

All of this assumes that their navigation was good, which is one reason
why they typically flew at low altitudes early in the outbound leg and
during the return leg, so they could see the wind on the water and take
that into account. Given the often large uncertainties remaining, USN
strike radius missions included a 1 hour reserve for rendezvous, landing,
and milling around while deciding "I think maybe the carrier is over in
that direction".

In the mid/late '30s, finding the carrier was made considerably simpler
for US and British pilots. Both countries developed directional VHF radio
beacons, which could be used relatively freely in tactical situations
because they were line of sight, whereas MF/HF beacons could be DF'ed over
the horizon. I forget the details of the RN version (Type 79), but AIUI
the US YE beacon broadcast a different Morse letter for each 15 degree
segment (keyed to the ship's gyrocompass) around the ship. So the pilot
listened on his ZB receiver for the Morse letter, looked up on his code
card for the day which 15 degree segment the Morse letter referred to, and
then flew the reciprocal course. ISTR range was something like 45nm at
1,500 feet, which was more than adequate to eliminate all but the grossest
navigation errors. TACAN was the postwar UHF equivalent (VOR being the
civilian VHF version), which presented directional info visually and also
(with DME) showed range.

Of course, that assumes that both beacon and receiver are working -- HMS
Victorious' beacon was down when her strike returned from attacking the
Bismarck in poor visibility and twilight, and her Captain began shining
searchlights off the clouds until told to stop by the admiral. He then
began to make a very long signal by light, using his largest signal
projector. Fortunately, all of her Swordfish got back despite their
mostly inexperienced crews (some had made their very first carrier landing
the day the ship sailed to look for the Bismarck), although some of her
Fulmar fighters sent up to shadow Bismarck didn't find her or Victorious
and subsequently ditched.

Once VHF beacons were introduced, VHF radars and VHF voice radio weren't
far behind with the same LOS-only advantages, so the carrier could also
home lost a/c by radar and radio directions, without making herself
particularly vulnerable. Anyone with a VHF DF receiver was theoretically
able to pick up the radar transmissions as well as radio ones so the risk
was the same, and they had to face the possibility of a radar-directed CAP
showing up.

Finally, by 1943 both USN and RN strike a/c had surface search radar,
which served the same purpose of localisation but didn't require the
carrier herself to broadcast.

How do they do it, today ?

I imagine Point Option is much the same, but given the advantages of
modern navigation/detection systems and the much higher speed of jets plus
their shorter endurance, a carrier won't move as far in relative terms
during a sortie as was the case in the piston-engine era. Nowadays the
carrier is typically programmed as a moving waypoint with the given course
and speed into the a/c's nav. system. With GPS/INS, everyone knows where
they are to within a few meters, assuming everything's working. All the
WW2-era systems and methods have their modern analogues.

Guy

"W. D. Allen Sr." wrote:

Good summary, Guy. I didn't realize how much I had forgotten.

It's a lot easier for me, as it's all just book larnin' with absolutely zero
personal experience. I've got nothing to forget, so it's easy to remember only
the details I want to ;-)

Guy

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

Harriet and John wrote:

Anybody remember YE/YG beacons?

I know YG was the backup to YE, smaller and less powerful I believe, but I
don't know if it otherwise operated the same.

Guy

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

We were doing blue water ops, and launched on an alert. I was a nugget
null-P in the E-2. The CAPC makes a big deal about grabbing an accurate
chart that's up to date before we going flying. We get airborne and he
opens the chart up...and it's all blue. Top to bottom, left to right. He
looks at it for a second, closes it back up and sticks it in the navbag
and says, "I guess we're there!"

In article , nafod40
wrote:

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

We were doing blue water ops, and launched on an alert. I was a nugget
null-P in the E-2. The CAPC makes a big deal about grabbing an accurate
chart that's up to date before we going flying. We get airborne and he
opens the chart up...and it's all blue. Top to bottom, left to right. He
looks at it for a second, closes it back up and sticks it in the navbag
and says, "I guess we're there!"

The INS on the ICAP II Prowler was actually pretty good, aligned well,
rarely lost it's platform or ran away too badly (except when really
needed of course). But when getting a CV alignment you often found the
ship had given you the wrong position. The problem here is that you
need an accurate INS position to the real geography to steer the
jammers and give valid steering data to the HARM. So....... launch,
manually degrade the INS and get an accurate update off of something,
apply manual mag var and winds to keep the system as tight as possible,
then when it's time to go home to an EMCOM mom, upgrade to INS mode
again and even though it's not accurate to the real world, point 0 is
still reasonably close to where you left and then apply the recovery
PIM and hopefully the auto dawg machine was where you thought it was.
And when it's not, fess up and call the Hummer or look for the nastiest
thunderstorm around and the boats under it.......

Pugs

How do they do it, today ? BRBR

We had a Tacan.....most of the time that is.
P. C. Chisholm
CDR, USN(ret.)
Old Phart Phormer Phantom, Turkey, Viper, Scooter and Combat Buckeye Phlyer