by Allan Ng
Canadian Defence Procurement – December 2003
The CF18 Incremental Modernization Program – In Detail
Details, details, ... the Nitty-Gritty Behind Boeing's ECP 583
Allan Ng reviews DND's CF18 fighter aircraft
modernization plan (Part 2)
Engineering Change Proposal 583 includes the addition of the following:
Raytheon AN/APG-73 multi-mode radar
The AN/APG-73 is a development of the original AN/APG-65. The APG-73
has all of the modes available to the earlier radar set but with triple the processing speed and memory
capacity, and the addition of Terrain Following and Terrain Avoidance modes. The latter features are
critical for any ground attack missions. For air-to-air missions the APG-73, unlike the APG-65, is capable of
guiding state-of-the-art AIM-120 AMRAAM active homing missiles.
The APG-73 is now a mature radar system – having entered US service in 1994 – and is
standard on later model F/A-18C and on the new F/A-18E/F Super Hornet. (There is some irony in the
APG-73's late entry into CF service, this radar having originally been a joint US-Canadian development.)
A possible future upgrade to the radar is an option that will allow the APG-73 to produce high
resolution radar ground maps useful for ground attack missions or for reconnaissance. 
BAE Systems AN/APX-111 Combined interrogator and transponder
Also known as IFF (Identification Friend or Foe), this device is used to determine whether any
electronically-interrogated aircraft are 'friendlies' or unknowns. (Depending on the rules of
engagement, any unknown tracks could be declared to be 'hostiles'.) Basically, the interrogator
portion of the APX-111 demands the correct coded response from a targeted aircraft. If that interrogated
aircraft is also fitted with an APX-111, the transponder will send back an appropriate coded signal to the
interrogator. Signals are only sent to interrogators the system recognizes. In other words, the
APX-111's transponder will either identify itself as 'friend' or it will not respond at all.
The APX-111 transponder unit is also compatible with civilian mode S functions and, presumably, mode C.
Both modes are required for flight in civilian airspace. The AN/APX-111 will bring the CF18 up to current NATO
standards for combat identification and will allow the AIM-120 AMRAAM missiles to be used out to their
maximum range while reducing the risk of 'friendly-fire' incidents. The CF18 was already equipped
with a transponder but, by combining the function of both interrogator and transponder in one unit, APX-111s
save weight and volume.