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

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