AN/APR-24 C/S/X-BAND RADAR HOMING AND WARNING SYSTEM (RHAW)


The AN/APR-24 system was a development of the proven and fairly successful AN/APR-23 system used on the A-4 Skyhawk.  The F-4Bs operating over North Vietnam were increasingly hampered by their lack of any RHAW gear.  As one air wing commander put in his post action summary, “Because the F-4 aircraft of VF-14 and VF-32 were inadequately equipped with electronic warning and jamming equipment, it became extremely hazardous to send them on armed recce missions inland without the company of A-4 Iron Hand aircraft.  It is strongly recommended that future F-4 aircraft deployed to S.E. Asia contain electronic warning equipment similar to the A-4E.”

The AN/APR-24 provided the pilot both visual and audio information about the electronic threat environment.  The system was installed using two fairings on the vertical tail fin to mount the antennas and amplifiers.  The signal was then sent to the black boxes and displayed on the Azimuth Indication Display and with audio signals in the pilot’s headset.  It covered C-band (4,900-5,900 MHz), S-band (2,700-3,600 MHz), and X-band (8,500-10,250 MHz).

Perhaps as an indication of the rush to get this system into the combat squadrons, there doesn’t seem to be an AFC (Air Frame Change) order issued to install this equipment. We do know that the Navy purchased 50 units from Melpar Inc. intending to equip four to five F-4Bs in each squadron as they were deploying to Vietnam. Their intention was that the AN/APR-24 aircraft would fly as either pathfinders or hunters leading killer aircraft to the offending radar for destruction. 

The problem was that the APR-24 just never worked out in the F-4.   It was temperamental and difficult to keep working.  In the VF-14 Command report after their Vietnam cruise of 21 Jun 1966 to 21 Feb 1967, they reported "Four aircraft were equipped with APR-24.  Upon completion of the mod program and during the transit period prior to ORI, only one or two aircraft were considered to have operationally ready weapons systems.  During the ORI, aircraft availability was considered poor.  A large amount of electrical and weapons system discrepancies occurred, many of which were directly attributable to incorrect and careless wiring during modification."  Or as an electronics shop summary put it, “Four of our aircraft were configured with the APR-24; the remaining eight were configured with APR-27.  As was the case with the majority of the participating squadrons, innumerable problems were encountered with the APR-24.  Estimates of “down” time range upwards of 90%, and none of our units could be classified as totally “up”. A so-called “Get Well” program at NAS Cubi Pt failed to achieve desired results.”

Other problems could be attributed to a lack of training the aircrews and technicians received on the new equipment because it was rushed into service so quickly. Again the VF-14 Command Report states, “The problem was twofold, inadequately trained personnel and a critical shortage of APR-24 parts within the supply system.”  It also states, "Four airplanes were equipped with the APR-24 passive and warning gear immediately prior to deployment.  This equipment, due to its low reliability, lack of spare parts and trained AO/AT's to maintain it, and coupled with the extremely "dirty" EW environment of North Vietnam, provided little or no improvement in operational capability of the F-4 weapons system."

 To be fair, rushing any electronic piece of equipment into service without thorough testing on an airframe is dicey at best, and it would appear that the APR-24 never benefited from a lengthy and careful development program.  Just because its predecessor worked well on the A-4 was no guarantee that it would work on the F-4 which had a much larger electronic footprint.  Perhaps it may have been successful if they could have worked the kinks out; but at this stage of the war everyone was on a very steep and fast learning curve and success was the only saving grace of the systems designed to protect aircraft from the SAMs.

Needless to say the system was not the answer the Navy was looking for and when the squadrons rotated out of the warzone, the equipment was removed and never seen again.  Today only one aircraft survives with the APR-24 antennas installed; it is BuNo. 152256 at Wings of Eagles Discovery Center at Horseheads, New York.

There is photographic evidence to verify the following aircraft were equipped with AN/APR-24 installed on these cruises:

CVA-42 USS Franklin D. Roosevelt (21 June 1966 - 21 February 1967)
     VF-14:             152229, 152318, 152323, 152327
     VF-32:             152210, 152314, 152320, 

CVA-43 USS Coral Sea (29 July 1966 - 23 February 1967)
     VF-21:             151502, 152256, 152260
     VF-154:           150485, 152304

USS Constellation (12 May 1966 - 03 December 1966)
     VF-151:            
     VF-161:            152216, 152316

CVA-63 USS Kitty Hawk (05 November 1966 - 20 June 1967)
     VF-213:
     VF-114:           153000, 153005, 153008

CVAN-65 USS Enterprise (19 November 1966 - 06 July 1967)
     VF-92:            150996, 151417
     VF-96:           151001, 152219, 152227, 152235, 152992


(click picture to enlarge)
AN/APR-24 Azimuth Indication Display 


External differences can be identified by a boxy forward and aft antenna fairing located on the vertical tail fin cap.


(click picture to enlarge)
AN/APR-24 Antenna Fairings
1. Forward Hemisphere Antennas
2. Aft Hemisphere Antennas




Revision History:
  • 02 May 2014 - Added information about aircraft equipped with AN/APR-24  
  • 13 MAR 2014 - Original Post
Sources:


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