I see that many fighter jets are capable of top speeds of Mach 2 or the like, but under what circumstances would this actually be needed? AIUI, this is almost never done because of the high rate of fuel it burns and also possible damage to the engine.
The only situations that come to mind are:
Needing to disengage from a fight, when you have to put as much distance between you and your foes as possible so you can go home;
An urgent intercept situation - say, something like 9/11, where a hijacked airliner is heading for the White House and you have to get to the airliner ASAP;
Some situation where friendlies on the ground need close air support ASAP and you have to cover the distance as quickly as you can.
Getting to the fight quickly is also important. The more time you spend over enemy territory, the more you risk getting shot at and possibly shot down. You want to get in quickly, do whatever you need to do, and get out quickly. If you can get in and get out at supersonic speeds, that’s an advantage all-around.
The ability to “supercruise” (cruise at supersonic speeds without guzzling unreasonable amounts of fuel) is important enough that it was a requirement during the development of the F-22.
A lot of older fighters can go supersonic, but only for short periods of time because they weren’t designed to supercruise and suck down far too much fuel to sustain supersonic speeds.
While supercruising is a fairly new thing for fighter jets, it is otherwise not new at all. The SR-71 could supercruise, as could the Concorde.
The reasons you give in your question are all correct. Another reason is to prevent anti-air missiles from getting to your aircraft. Rockets fast enough to catch you burn a lot of fuel fast so this gives them a limited range so if you can run fast for a short amount of time the anti-air missiles won’t catch up before they run out of fuel. Anti-air rockets can often go much faster than mach two.
Aside from missiles, anti-aircraft cannons have a harder time hitting you the faster you go. And also the faster you go the less duration of time you have to be under attack from them.
In general there are no tactical circumstances where a fighter jet would reach Mach 2. This is because:
(1) Almost all fighters rated for Mach 2 cannot reach that while carrying external stores (IOW missiles or fuel tanks). Yet without weapons and tanks the plane has almost no tactical value.
(2) To reach Mach 2 in a “clean” configuration requires a specific flight profile. IOW the plane must take off with full internal fuel, carefully climb to the optimal altitude for the attempt (typically around 35,000 ft), accelerate in afterburner in a mild descent. Almost immediately upon reaching Mach 2 the plane is in a “bingo” fuel state and must promptly descend and land. Yes they could take off with tanks, climb to altitude, jettison them or use air-to-air refueling, then make the Mach 2 attempt. But it still burns so much fuel within about 10-15 min. it would have to land or refuel again.
To my recollection the only military aircraft ever certified for Mach 2 flight with external tanks were the F-104 with tip tanks and the B-58 Hustler bomber.
I think the B-1A could reach Mach 2 at high altitude and it didn’t need external tanks. But it was never a production aircraft, and certainly not a fighter.
The F-22 uses internal weapons and I think can reach Mach 2.0 if not carrying external tanks. So that is one possible exception. But it can reach about Mach 1.8 without afterburner, so the large additional fuel consumption to reach and maintain Mach 2 wouldn’t make sense.
Wouldn’t the SR-71 design be capable of serving as a fighter? Presumably it would be scaled up for more payload capacity (and modernized with more advanced engines), but in principle you could mount the radars and a couple air to air missiles where the spy equipment goes.
Obviously such an aircraft wouldn’t be designed for a dogfight, it would be used to intercept enemy aircraft where it engages them with missiles from tens of miles away and then heads back to base for rearming and refueling.
The extreme speed of the aircraft would mean it would be very difficult to shoot down from the opposing jet.
An SR-71 variant known as the YF-12 was built as an interceptor. As the name implies, this was a variant of the A-12, which was the CIA version of the SR-71. They modified the nose to fit a fire control radar system, added another crewman to operate the air-to-air missile targeting system, and replaced a bunch of reconnaissance equipment with missiles.
They built 3 for testing, and these worked so well that the Air Force ordered close to a hundred more. The order was placed on hold due to the costs of the Vietnam War at the time, and when the war came to an end, priorities had shifted and the YF-12 was cancelled.
Two of the YF-12s were destroyed. The third is in the National Air Force Museum in Dayton, OH.
Hmmm. The F-14 and F-15 couldn’t reach Mach 2 with any external stores? I can see not making it with tanks, but neither could with any ATA loadout? Did conformal tanks for the F-15 enable it to reach near Mach 2? As you note, it sort of kills the point for a Mach 2 interceptor if it can’t do any shooting once it gets out to where the threat is.
FWIW, e_c_g, I thought the trapeze deployment for theAIM-47 Falcon for the YF-12A (or the F-108, which was supposed to go nearly as fast) would have worked a lot better in theory than in reality. Not surprising, as the AIM-4 Falcon, that the AIM-47 was a derivative of, was a titanic piece of shit.
Still, IIRC, Kelly Johnson or Ben Rich was bragging in one of their books about a successful test the F-12 performed that was similar to the famous one the F-14/AIM-54 combination did a few years later: killing multiple targets at widely divergent speeds and altitude. And they did score 6 kills out of 7 shots during testing. The last kill was launched from 75,000 feet at Mach 3.2, and it smoked a bomber-sized drone 500 feet off the ground.
Amazing capability on paper. But I guess not multi-service capable, which is what I think McNamara and his successors were going for, in light of their advocating the F-111 project.
The YF-12 could definitely exceed Mach 2 but it’s such a special case I don’t think it qualifies for the OP question. His question was “under what circumstances would this be needed?” – IOW what special circumstances would a regular fighter do this.
The SR-71 cruised at Mach 3 on every normal mission and had the YF-12 been in production it would have probably done likewise. There was no normal circumstance when they would not do that since they operated most efficiently in that regime.
Re regular fighter planes, I don’t have the references but there are many factual accounts in the aviation literature of them reaching Mach 2. But – in every case I can remember it was a rare situation involving special effort. So few pilots did that they sometimes had an informal “Mach 2” club with a special shoulder patch or framed certificate.
In general the planes had to be clean and not carrying tanks or other external stores. The effort depleted the fuel within a few minutes and subjected the aircraft to great aerodynamic heating. Ejection at anywhere near Mach 2 was usually fatal, so there was risk. That is why the planes that were actually designed to sustain Mach 2 and higher (B-58, XB-70, B-1A, etc) all had cabin or capsule ejection systems. The SR-71 pilots wore space suits and flew so high the dynamic pressure was low enough the special ejection seat would give them a chance at surviving. Modified SR-71 ejection seats were used on the first four space shuttle missions.
The F-14A had a max allowable speed of Mach 2.04 at 50k ft, according to official data (translating kts to Mach at the specific altitude) in its ‘Standard A/c Characteristics’ booklet of 1977, which was the same clean or with 4*AIM-7 (so was presumably due to some strength or temperature limit of airframe or engines). Top speed M 1.8 with pair of 280 gal drop tanks rated for supersonic flight. The F-14D had an imposed speed limit slightly below M 2 in any condition, per its booklet of 1985.
The F-15C has a top speed of M 2.34 with 4AIM-7 at 45k ft, M 1.96 with conformal tanks and 4AIM-7 at 35 k ft, per SAC’s of 1992. The highest speed given in any condition in that booklet was M 2.37 at 45k ft, with three tank pylons but not the tanks.
But as mentioned seldom are/were M2+ speeds directly tactically relevant.
War emergency power would have been used with the old century series fighters needing to get up north to shoot down bombers crossing the pole. Its been a while since I read the reason for the Avro Arrow specs and why we required a mach 2+ speed
Arguably the main advantage of fighters is maneuverability. Maneuvering causes drag losses which can leave an aircraft in a vulnerable low-energy state; Not something you want in a dogfight or when dodging missiles. You want to be able to maneuver hard, get your speed back up, maneuver hard, get your speed back up.
“Capable of Mach 2” doesn’t necessarily mean it’s intended to be used that way. If you want to give a fighter the ability to accelerate quickly when it wants to get its speed back up after hard maneuvering, you’ll need engines that give your plane a high thrust-to-weight ratio which could end up being capable of Mach 2 even if you don’t really care about having a Mach 2 top speed.
In 1956, the pilot of a Grumman F-11 Tiger fired his cannons during a test, then entered a descent and hit the afterburners. He ended up hitting something that shattered his windshield and knocked out his engine. He thought that it was a bird strike, but the accident investigation concluded that he overtook his own bullets and basically shot himself down.
I just wanted to say “Thanks” for the detailed cites. For the F-14A, those tanks are maybe 20% of total fuel capacity. At a calculated 32.5 lb/sec fuel consumption at max thrust in burner, (from here, on the TF-30 engine: Redirect Notice ) and 6.8 lbs per gallon for JP-5, those two tanks would be drained quickly. I get around two minutes of burner time with the fuel in the tanks. To get another 10 miles a minute-ish over regular cruising speed.
I guess if that extra distance is the difference between the inbounds getting to release their payloads or not, it’s worth it.
I don’t understand the question. My point about payloads was in reference to the situation where the interceptors are trying to defend against an attack from missile-carrying aircraft. If the interceptors can kill the attacking aircraft before the aircraft can launch, it really cuts down on the number of targets the total air defense system has to cope with. Enough so that it probably will be the difference between the base surviving or not.
So, if boosting out at Mach 2 allows the interceptor to gain a few minutes advantage in firing their weapons versus not using afterburners, and those few minutes are the difference between the attacking aircraft launching their missiles at the interceptors’ base or not, then going at Mach 2 has serious advantages. Even if by doing so means the interceptors no longer have sufficient fuel to return to base.
Couple of data point to throw out…Mach is not a fixed speed. It varies by altitude. Mach 1 at 50,000 feet is considerably slower than it is at 500 feet.
Some of the things mentioned above are not accurate. I filmed multiple missile launches from an F-16 going about 1.5 mach (and also pulling slightly over 7 G) for test purposes, so yes, both F-16s and F-15s are capable of going over the speed of sound while carrying air to air missiles. I filmed AMRAAM launches mostly at those speeds. Seems Like I may have done some of the later AIM 9 models, too.
When we were doing to missile shots, we’d get only one pass per tank of gas, so we’d climb up to altitude, either flip flop or roll in to the dive, push through the mach, start the pull, jockey for position…and if everything wasn’t right, I’d call “Skip it” and we’d slow it down, hit the tanker, and try another run.