CASR

- Canadian Defence Policy, Foreign Policy, & Canada-US Relations -

In Detail —— the CF18 Hornet fighter ——

by Allan Ng M.Eng., P.Eng.

CF18 Index

In Detail Home

CASR Home

Contact CASR

Canadian Defence Procurement  –  November 2003 The CF18 Hornet fighter aircraft  –  In Detail    (Part 6) Allan Ng examines the evolution and development of the CF's fighter Out of Sight  ...  Beyond Visual Range Combat Medium-Range or Beyond Visual Range (BVR) air-to-air combat became possible with the introduction of reliable radar-guided missiles in the 1960s. Fighter aircraft could now launch a missile and destroy an adversary before either aircraft is even seen.  In BVR air combat, the fighter that can detect its adversary first obviously has the advantage. So, good BVR fighters must have a very capable sensor suite. The primary long-range sensor for fighter aircraft is the modern multi-mode radar. Next, the fighter aircraft must be able to carry, launch, and direct multiple long- or medium-range air-to-air missiles (MRAAMs). So, if one has a large radar and MRAAM then the engagement is decided right? Not exactly.  Aircraft performance is still import. Good engine thrust, as measured by the thrust-to-weight ratio (T/W), is an important factor in BVR engagements. A high T/W helps an aircraft manoeuvre quickly into favourable firing positions for the MRAAM.  It also improves the aircraft's acceleration giving the MRAAM extra energy to extend its range and get the missile to the target faster.  On the other hand, a fighter aircraft's turn-performance comes into play when attempting to escape enemy missile fire. A typical MRAAM can easily out-turn any fighter aircraft.  However, the missile is only able to maintain this level of performance through specific portions of its flight envelope. The missile's rocket motor delivers maximum thrust at the start of the missile's flight.  Missiles are most manoeuverable during this phase – aircraft caught within this stage of the missile's flight envelope will likely be destroyed. This part of the envelope is, appropriately, called the 'no-escape zone'. However, due to size and weight restrictions, missiles carry severely limited fuel. Eventually the rocket propellant is exhausted, the missile runs out of thrust, and must coast towards its target.  Most medium- and long-range engagements end with missiles gliding on their stubby wings as guided darts. Decreasing speed not only lessens the chances of catching up with an intended target, it also has deleterious effects on the missile's aerodynamic control surfaces.  This is the point where the fighter aircraft under attack has the opportunity to out-turn the intercepting missile and escape its own destruction. In other words, many of the same characteristics that make for a good dogfighting aircraft, also proved to be vital in the BVR arena. As we've seen, the CF18 has a better than average thrust-to-weight ratio matched with relatively low wing loading. The aircraft had a very capable multi-mode radar in the Hughes APG-65 set that provided guidance for its AIM-7 Sparrow MRAAMs.  This combination of radar and missile made the CF18 quite capable in BVR combat. Baseline CF18s had somewhat reduced BVR capabilities compared with the F-14 Tomcat and F-15 Eagle (both of which had much larger radar antennae [1] ).  But, CF18s did provide BVR capabilities that early F-16s simply did not possess.  The CF18 was an excellent compromise.