Jet Fighter Performance! Is it CRITICAL to be FAST??
Jet Fighter Performance! Is it CRITICAL to be FAST? It’s not always as cut and dried why you need powerful engines and why the performance is important. Even if speed is the only consideration to a given aircraft design. Military jets don’t always require to fly fast but they must be powerful. There job often requires carrying large amounts of fuel to deliver from 1000 to possibly 10,000 lb of weapons to a target. This requires a lot of power combined with the aircraft to overcome the weight and drag penalties to lift off a runway. Once in the air the aircraft must lift the aircraft and weapons generally to higher altitudes where the air is thinner and the aircraft can cruise at a higher ground speed.
Often a strike mission requires a high, low, high flight profile so an aircraft takes off and heads to say 30,000 ft flies the cruise portion of the mission before defending to a lower altitude to deliver weapons before returning to a high altitude to transit home.
BVR Air Combat Speeds
Times where being very fast and high which requires a lot of power is the air to air BVR (Beyond Visual Range) fight. Launching missiles like the AMRAAM AIM-120 D from an F-15 at say 10,000ft at a cost altitude target may only get 20NM at 450 knots.
This is OK but if you were supersonic at say 900 knots you add the energy of the F-15 to the launch speed of the AMRAM-120. The AMRAM-120 is reported to have a Mach 3 capability bit if you launch at Mach one then the initial max speed of the missile will be over Mach 4 with the combined missile and aircraft speed. The range could extend to 35 miles again at low altitude launch.
Take this a step further and fly the F-15 at Mach 2.5 at 50,000 feet the speeds now climb to Mach 5 launch speeds and the super thin air at this altitude reduces drag on the missile enormously. The lower drag and speeds take the max range of the missile, the Aim-120 D out to around 80NM!
The figures I use are an approximate difference in performance as a guide. Actual figures change in real life but the Aim-120 D is reported to have 80 nm real life range. Likely its more than this with newer motors. I know missiles I worked on had training motors but the War shot motors had much more range.
Jet Fighter Performance
Getting back to aircraft performance, for a long time the doctrine in cold war times was low level penetrative with terrain following radar (TFR) and remaining fly under the radar at under 100ft agl if required. TRF on the F-111 had 100, 200 to 500 ft steps in altitude and with it’s swing wing could fly very fast at night and in cloud with its powerful TF-30 Turbofans.
At low level the British designed Tornado is reported to be the fastest low level aircraft produced. The Tornado was a great aircraft to work on and when the aircrew had done super low level fast runs often it could lose paint in the leading edges of the wing and other surfaces.
Fast Jet Fighters.
Somewhere about 950 knots is as fast as most aircraft can fly at low level with the top speed of aircraft being Mach 3 with the Mig-31 being the fastest. At Mach 2.85 with sprints of 3.2 are possible but reported to damage engines on occasion. It’s cruise speed of Mach 2.25 is super impressive with a service ceiling of 82,000ft.
These performance figures can only be achieved with very powerful engines. The F-15C by comparison has performance that is pretty good, but not as fast as the Foxhound. A max speed of Mach 2.5 and ceiling of 62,000 ft it does not match the Foxhound in these areas.
Conclusion.
The question is Jet fighter performance important it depends on the application. Pilots always want more power like racing drivers. It gives you so many more options from flying fast low or even faster up high! You can carry more weapons and get there faster. Its all about performance isn’t it but horses for courses.
Flying fast under the radar in TFR mode like a Tornado IDS or F-111 Aardvark or carrying a ton of Mavericks and bombs to support troops in your A-10 Thunderbolt. Its all relative to the task in hand!
Author.
Brendon McAliece in a 23 year veteran on fast jets from the Mirage III to the F-18 and F-111 as well as many trainers, helicopters and training aircraft. He spent 13 years in the Middle East working on BA Tornado IDS & ADV aircraft. He holds a Sport Pilot License and has flown Jabiru 160,170 & 230 aircraft as well as Diamond DA-20.
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