Vietnam era F-4s Q

Radar beacon mode is a different animal altogether than the IFF
interrogators we've been talking about. The rendezvous beacon that tankers
carried and the one carried in F-4s (SST-181X, sometimes called "Skyspot
Beacon" though I don't know if that name's official) are interrogated by the
radar itself using a selected radar PW/PRF as I recall, not a separate
interrogator as with APX-76 or 81. The beacon in the F-4 had a code that
had to be preset before the flight by maintenance since it was dialed in on
the SST-181X itself, which was buried inside Door 19. I don't know what
kind of beacon the tankers carried or whether it was accessible in flight.
Lots of US military aircraft radars can interrogate rendezvous beacons.
Even the APN-59 radar in the C-130 could do it, though cargo Herks had no
IFF interrogation capability.
Scott Wilson

"Ed Rasimus" wrote in message
...
(Smartace11) wrote:


I presume you meant APX-76 for tanker join-ups? Combat Tree wouldn't
seem to
be
useful for them, unless our KC-135s were carrying Soviet IFF systems

At that time the whole system was called Combat Tree, as least by the
aircrews.
I was a dumb crew dog and just flew the things


I'll go with Guy on this one. The beacon mode of the E-model radar we
were using at Korat sure wasn't Tree. It worked on 100 and 200 mile
scope and was nice for finding your tanker. But it was strictly
"cooperative" target recognition.

I used to tweak Rod Bates, my back-seater after Linebacker II, to take
tanker "judy" as far out as he could. If he could get the tank to
squawk, he'd try to judy in the turn out of traffic. He got some
contacts at 125 to 150 miles and ran the whole intercept.

Of course, the beacon return on that long a range was a wide slash on
the scope. It got you going in the right general direction and you got
a refined return as you closed the range. By the time you got to skin
point you would be right on track.

Sorry bout this one, Steve, you're old memory is fading. CRS, I guess.



Ed Rasimus
Fighter Pilot (ret)
***"When Thunder Rolled:
*** An F-105 Pilot Over N. Vietnam"
*** from Smithsonian Books
ISBN: 1588341038

I mentioned...

At the time of its MiG Kill 66-7550 was sporting the red fin flash and
PN tail code of the 523d TFS from Clark. Did you guys give some of
your jets to them as well as the 555th and 13th TFSs?

Smartace11 posted:

I had left the Kun' a month before the planes were transferred (Apr 72) and got
to Holloman just in time to repack my bags for Tahkli. I was under the
impression that all of then went to the 555th but that is just an assumption.
The Combat Sage guys at Clark could have had their hands on one for testing.

From the handi-dandi aircraft cards (microfiche) on file at
Maxwell...wing assignment and effect date for #66-7550

15th TFW 23 MAR 67,
4th TFW MAY 68,
432d TRW JUN 70,
405th FW MAY 71, (MiG-21 Kill 16 APR 72 13thTFS/432d TRW crew)
3d TFW NOV 72,
8th TFW SEP 74,
51st CW DEC 81,
465th TFS DEC 82,
89th TFS JAN 89,
ZW 31 OCT 89 (removed from service)

According to the maintenance accounting the jet went from Udorn to
Clark (May 71) then to Kunsan (Nov 72). But if your log says
otherwise...most confusing.

Juvat

Guy Alcala posted:

Just to help the confusion along, Thornborough shows the 523rd being transferred in
its entirety from Clark (405th TFW) to Udorn (432nd control) under Constant Guard,
on April 9th 1972.

Not responding simpy to be pedantic...it was the 405th FW (no Tactical
in the Lineage between Mar 1959 and Sep 1974) and the 523d TFS was
attached to the 432d TRW in TDY status (Constant Guard).

I was in high school at Clark and the father of one of my best buds
was the 523d CO (Farrell Sullivan). He was KIA over Hanoi on 27 Jun 72
while flying an E model belonging to the 308th TFS/31st TFW. I vividly
remember Mike telling me he was moving back to the States because his
Dad had just been shotdown by a SAM over Hanoi.

Juvat

Guy Alcala wrote:


Wihtout knowing just how the F-4 was set up, I'd assume it was interrogating the
tanker's IFF transponder rather than its radar (and not the SST-181X Sky Spot
transponder either). All I can find is the F-4C/D Comm-Nav-Ident package listed
as AN/ASQ-19, so the transponder is presumably included in that. The comparable
sheet I have for the F-4E appears to have a misprint/typo in its listing for the
same item, so it doesn't help.


The maintenance coding for interrogator responses (code IV, as I
recall) was done through a panel in the nose wheel well, not door 19
which was on the aircraft spine behind the R/C/P.


FWIW, in Rosenkranz "Vipers in the Storm", he describes getting set to go on his
first mission. The plane captain asks him what his Mode 2 is, and Rosenkranz
gives him the four digit code which the chief then sets in the nosewheel well
while Rosenkranz gets settled. Later, during the mission, Rosenkranz writes that
the Mode 1 setting, 51, is due to change automatically to 43 at a certain time,
and he calls up the appropriate page on his UFC to make sure it did and then
makes a call to his flight members to remind them to check, because he says the
F-15s will be interrogating Mode 1 as the strike egresses. I have no idea what
Mode 4 is, other than knowing it exists and that the on/off switch is on the
transponder control panel. Mode 3/A is the standard 4-digit ATC transponder,
with Mode C being altitude encoding (at least in the civil world), but that's all
handled in the cockpit.


Mode 1 is a 2 digit (octal, 0-7) military transponder signal which
is set in the cockpit. Actually, according to my -1, the second
digit is only 0-3, but these each appear twice on the rotary wheel.
Use in theater will vary, typically changing in 2, 4, or 6 hour
increments per theater instructions.

Mode 2 is set on the ground, and is typically not changed in flight.
In some aircraft/installation packages, this may be changed in flight,
but there is typically no need to do so.

Mode 3 and C are the same systems used by civil ATC. A 4 digit octal
code is selected by thumb wheel, pushbutton, or other entry system, and
the aircraft replies with this code. Mode C includes pressure altitude
return (uncorrected for altimeter setting, which is why ATC will often
query/update your altimeter setting if you are cruising at say, 300 ft
off altitude).

Mode 4 is an encrypted system, whereby interrogations will be ignored
unless they meet the encryption criteria stored in the mode 4 computer.
These are typically changed on a 24 hour cycle, and the system will hold
2 codes to allow for changeover which (typically) occurs at zulu day
changeover. In some aircraft, the computer may be loaded in flight,
but others can only do so on the ground. Most systems have warning
indications to tell the crew if the load is bad/missing, or if the
aircraft is being interrogated and not replying for some reason- a
useful warning, as the failure of this system could result in being
misidentified as a bad guy to someone with the ability to ruin your
day.

Mike

Juvat wrote:

Guy Alcala posted:

Just to help the confusion along, Thornborough shows the 523rd being transferred in
its entirety from Clark (405th TFW) to Udorn (432nd control) under Constant Guard,
on April 9th 1972.

Not responding simpy to be pedantic...it was the 405th FW (no Tactical
in the Lineage between Mar 1959 and Sep 1974)

You're right, and so's Thornborough. My brain/fingers inserted the 'T' out of habit.
Was that Yeager's outfit at one point ('67 I guess, as he was the president of
Broughton's court-martial), flying B-57s in SVN?

and the 523d TFS was
attached to the 432d TRW in TDY status (Constant Guard).

I was in high school at Clark and the father of one of my best buds
was the 523d CO (Farrell Sullivan). He was KIA over Hanoi on 27 Jun 72
while flying an E model belonging to the 308th TFS/31st TFW. I vividly
remember Mike telling me he was moving back to the States because his
Dad had just been shotdown by a SAM over Hanoi.

Not something you're likely to forget.

Guy

But Ed, he is correct in that the beacon tracked by the F-4 radar was the
SST-181 and the F-4 (in fact I think all aircraft had one) had a SST-181
switch in the back seat that turned on the beacon for use by the Combat
Skyspot, or a tanker, or any other radar that could track it.

In the F-4, you had to select Beacon on the radar, which put the system in a
mode where it looked only for beacons and skin paints were not possible.
The trick in the backseat was to know when the "paint" was strong enough
that you could switch back to T/R and get a "contact".

In the AC-130A we had to remove the entire SST-181 transmitter before we
left for Desert Shield/Storm, because for some reason it would radiate at
low power even when turned off, and it was an EMCON hazard.
--
Les
F-4C(WW),D,E,G(WW)/AC-130A/MC-130E EWO (ret)

Guy Alcala wrote:

Ed Rasimus wrote:

The tanker rendezvous system had the F-4 radar interrogating the
tanker radar to generate an enhanced return on the fighter's radar
display.

Wihtout knowing just how the F-4 was set up, I'd assume it was interrogating the
tanker's IFF transponder rather than its radar (and not the SST-181X Sky Spot
transponder either).

A slip of the flying fingers typing lexicon. Yes, we interrogated the
tanker transponder, not the tanker's radar.



Ed Rasimus
Fighter Pilot (ret)
***"When Thunder Rolled:
*** An F-105 Pilot Over N. Vietnam"
*** from Smithsonian Books
ISBN: 1588341038

In beacon mode in the F-4 we interrogated the tankers SST-181 beacon, not
his IFF beacon. The tanker had to turn on the SST-181 and sometimes we had
to request it.

If the F-4 was APX-80 equipped (if it was working) you could interrogate the
IFF also.
--
Les
F-4C(WW),D,E,G(WW)/AC-130A/MC-130E EWO (ret)


"Ed Rasimus" wrote in message
...
Guy Alcala wrote:

Ed Rasimus wrote:

The tanker rendezvous system had the F-4 radar interrogating the
tanker radar to generate an enhanced return on the fighter's radar
display.

Wihtout knowing just how the F-4 was set up, I'd assume it was
interrogating the
tanker's IFF transponder rather than its radar (and not the SST-181X Sky
Spot
transponder either).

A slip of the flying fingers typing lexicon. Yes, we interrogated the
tanker transponder, not the tanker's radar.



Ed Rasimus
Fighter Pilot (ret)
***"When Thunder Rolled:
*** An F-105 Pilot Over N. Vietnam"
*** from Smithsonian Books
ISBN: 1588341038

In the F-4, you had to select Beacon on the radar, which put the system in a
mode where it looked only for beacons and skin paints were not possible.
The trick in the backseat was to know when the "paint" was strong enough

Good put, best yet. I knew there was a reason I didn't care for it but had
long forgotten.

Steve

According to the maintenance accounting the jet went from Udorn to
Clark (May 71) then to Kunsan (Nov 72). But if your log says
otherwise...most confusing.

Juvat

Not sure that is all that unusual though.

We may have been loaned the plane as a part of the Combat Tree ops testing.
Like I said, about I knew was that I was supposed to fly whatever was on the
scheduling board. I need to go to the base and check the full tail number. I
live a mile from the post the bird now sits in front of the other side of
thebase from the Museum.

Ever wonder where the name Juvat came from?