Exploring Why Modern Jets Occasionally Seem Slower Than 1960s Aircraft

The Evolution of Air Warfare: From F-4 Phantom to F-35 Lightning

Have you ever wondered why an F-4 Phantom is somehow faster than the F-35? Fighter jets haven’t gotten faster in the past 50 years, and here’s why.

The Vietnam War went on for twenty years. During the conflict, both the US Air Force and Navy used various models of the F-4 Phantom to go up against Vietnam’s MiG-21s – both planes had a max speed of Mach 2.2.

Military analysts reviewed more than a thousand of flight data from sorties flown by the American fighters over North Vietnam. It was found that none of these F-4s flew at Mach 1.8 and above during combat.

Regardless, a few minutes were flown at Mach 1.4 while there were several hours of flight time at Mach 1.2.

During the two World Wars, one of the advantages of high speeds was escaping enemy fire. However, the interaction of air-to-air and surface-to-air missiles completely changed the strategy on the battlefield.

Now, air-to-air missiles like the AIM-120 have a top speed of Mach 4, while some variants of Russia’s S-300 missile can reach a top speed of Mach 7.

Supersonic speeds are rarely advantageous in modern warfare, even when flying into a combat zone. That’s because flying at such speeds consumes a lot of fuel.

A study done by Northrop Grumman tackled a multitude of intercept cases and found that speeds above Mach 1.1 severely reduced combat range. In fact, increasing an F-4 Phantom’s cruise speed from supersonic to Mach 1.5 reduced its combat range by about 70%.

However, maximizing the turn rate also means driving down the speed to about Mach 0.7.

The emphasis on stealth further reduced the importance of speed.

An aircraft flying at supersonic speeds will suffer an increased heat signature, making them an easy target for SAMs. In addition, the use of afterburners and the aircraft’s body heating up due to increased air resistance make it easier for infrared sensors to detect the aircraft.

That’s why the F-22’s maximum sustained speed was reduced from Mach 1.8 to 1.6 – to reduce the heat load on the leading edge of the composite wings.

An F-104 Thunderchief had a speed of over Mach 2 but suffered from a smaller combat range and could carry less armament.

In comparison, the F-35’s top speed is “only” Mach 1.6, but it can carry more missiles, is stealthier, and has a bigger combat range.

Simply put, the new generation of fighters is designed for marathon, not sprints.

It’s safe to say that this change in aerial warfare is planned and accounted for. There’s no doubt that American can make a faster aircraft, but its viability might be compromised.

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