- Westinghouse AN/APQ-56 (modified) with a Teledyne AN/APN-79 Doppler set for navigation
- North American Aviation Autonetics Division’s NASARR (North American Search and Ranging Radar) which was being developed at the same time. This radar was optimized for the attack role and thus fit in nicely with the anticipated role of the AH-1 and the early F3H/F4H designs. The early F4H-1 models showed this pedigree with their 24-inch radome which had been designed around the NASARR radar requirements.
The 32-inch antenna would pose several engineering challenges. First came the fuselage redesign to widen the nose cylinder to allow for a 32-inch antenna. From FS 77.0 forward the fuselage was redesigned to deepen and widen the nose. (All future nose changes also took place from FS 77.0 forward like the RF-4, and F-4E)
Fuselage structure modifications forward of FS 77.0
After extensive research into the state of radome technology, McDonnell chose the Brunswick Company in Virginia (maker of bowling balls and fiberglass boats) to construct the new radome. The Brunswick engineers came up with a way to wind fiberglass filaments around a conical form provided by McDonnell in the exact shape of the radome. The filaments are wound in alternate layers which are 90 degrees from each other. One layer of filaments, called circs, are wound around the form circumference and the other layer of filaments, called longos, are wound around the radome lengthwise. The layers of filaments are then saturated with resin, to seal it from absorbing moisture, and baked in an oven until it is cured into a strong yet flexible cone. The engineers at Brunswick then constructed a grinder connected to a special meter that measured the phase shift of an electromagnetic wave as it passed through a section of the radome. The grinder would grind the thick or dense areas of the radome until the whole radome registered identical readings. The bonded fiberglass shape is then covered in a layer of neoprene to act as a rain erosion barrier and a small metal nose cap is affixed to the radome to prevent rain and airflow from peeling back the neoprene shell. (I have seen a pin hole on the neoprene peel half the radome like a banana when it came back from a flight.)
(Note: the lone exception to this process was the RF-4s which had a painted radome (epoxy enamel finish) with a fabric/neoprene boot only covering the first 12-inches of the radome.)
Please understand that this isn't a definitive list. I am having a hard time finding pictures to validate each aircraft. I have included BuNos. of the ones that I have been able to verify and will keep it updated as I find more information.
VARIATION 1 : All Metal 24-inch Nose with Metal Rib Structure (opens left)
Verified on BuNos: 142259a, 142260a, 143388a,
This was an all metal nose with internal metal rib structure not intended to be compatible with radar, so these aircraft were not equipped with radar while equipped this radome. Many of these aircraft had an instrumentation pallet in the nose where the radar would have been.
Internal Structure of the 24-inch metal nose.
|BuNo. 142259a with metal nose. Notice TAT probe installed later in test program.|
|BuNo. 143388a Showing to good effect the screw pattern on the metal nose.|
|BuNo. 143388a Showing screw pattern on metal nose.|
|BuNo. 143388a With radome open. Notice instrumentation pallet swings out to the right (just beyond the open radome).|
Verified on BuNos: 145307b,
Again, aircraft fit with this radome would not have had radar installed because of the metal rib structure that underlies it.
|BuNo. 145307b - The screw pattern can easily be seen showing the underlying structure.|
For some reason three aircraft had a modified radome which opened upward instead of to the left like the others. The radome was a new 24 inch glass fiber type, without internal structure other than the mounting ring so it would be compatible with a radar set. Externally I am not sure you would see any differences, just that internally it was hinged differently.
|Structural Repair manual shows a glass fiber radome which opens upward.|
Aircraft equipped with this radome could have had AN/APQ-50 radars installed because of the lack of internal metal structure.
|BuNo. 143389a with 24-inch fiberglass nose.|
Verified on BuNos: 143392a, 145311b
These aircraft had a much longer radome which actually was built over a 24-inch radome structure. The nose appears to be much straighter on top as well as being more symmetrical in shape than the eventual production noses. This nose was used to test out the aerodynamic qualities of the proposed 32-inch radome. Since it had two layers of metal ribs (one on each radome) and a test instrument boom installed, these aircraft did not have a radar installed.
|Illustration showing the outer structure built around the normal inner 24-inch structure.|
|BuNo. 143392a showing its 32-inch nose|
|BuNo. 145311b showing its 32" nose|
Verified on BuNos: 145313b, 146817c and subsequent aircraft.
|32-inch production radome|