F-22 Speed Vs Fastest

Anything goes, as long as it is about the Lockheed Martin F-22 Raptor
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rowbeartoe

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Unread post05 Sep 2017, 21:17

HI everyone. I've read a lot about the F-22 vs F-15 and from what I'm understanding it's not about the actual top speed. For example, At altitude with minimum if any weapons, the F-15 is Mach 2.5+, Mig 25 is Mach 3.2, Mig 31 is Mach 2.8, F-14 is Mach 2.3, F-22 is Mach 2+, F-18 is Mach 1.8, SR-71 is Mach 3.3+ etc. What I gathered was that in a big part because of afterburner and fuel, The fastest speeds for these Jets outside of the SR-71 was for a brief time and in all likelihood not the main contributor to being the best interceptor (a Jet that can investigate a bogie as quickly as possible). Obviously "super cruise" would give an advantage over afterburner for extreme distances. So with all that said and without disclosing anything classified, is it safe to say the F-22 is the fastest interceptor around? Meaning, can the F-22 intercept a bogie faster than an F-15C? Also, could the F-15C intercept faster than a Mig 31 or MIg 25? And Lastly, for our great Navy, without the F-14 and Phoenix Missiles, how have they managed with a fleet of Jets unable to even reach Mach 2 or launch weapons from over 50 miles away? I've never understood that. Thank you everyone!
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alloycowboy

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Unread post06 Sep 2017, 00:05

What most people do when they look at aircraft specifications is look at the specified top speed of aircraft and get all excited. I use to do this when I was a kid and was new to aviation. However once I took some physics courses I realised that speed or velocity is a certain distance travel over a duration of time. Or to put more plainly it is an average speed.

So when an aircraft is flying an intercept on an enemy aircraft it wants to reach the target as fast as possible in order to prevent it from releasing ordinance on target. However the intercepting aircraft has to make sure it has sufficient fuel to return to base or get to the trailing tanker.

All third and forth generation fighter have to go full afterburner in order to go supersonic which greatly reduced their combat radius probably to about a third or a a quarter depending the profile being flow.

According to Wikipedia,

"The F-22 Raptor's supercruise capabilities are touted as a major performance advantage over other fighters, with supercruise being demonstrated up to at least Mach 1.7[14] Virtually all current and past jet fighters, prior to the F-22, cruise at approximately Mach 0.8–0.9 with a militarily significant weapons load.[15] However, supercruising uses more fuel to travel the same distance than at subsonic speeds, with the Air Force Association estimating that use of supercruise for a 100-nautical-mile (190 km) dash as part of a mission would cut the F-22's combat radius from about 600 nautical miles (1,110 km) to about 450 nautical miles (830 km). This reduction is unconfirmed because the altitude and flight profile are classified, as are most of the F-22's capabilities, but it is still far less of a reduction than would result from the use of afterburner."
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alloycowboy

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Unread post06 Sep 2017, 00:21

Additionally this was released on Newatlas today:

Royal Navy test fires supersonic interceptor missile

http://newatlas.com/royal-navy-test-sea-ceptor/51185/
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viper12

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Unread post06 Sep 2017, 01:19

The specified top speed of fighter jets (of previous generations) is a pretty meaningless metric in most scenarios ; if you look around a bit on the net, the highest speed that's ever been achieved in combat is Mach 1.4 IIRC. There are multiple reasons why it's so low compared to the specified top speeds :

1) Drag in combat configurations ; to be useful, fighter jets need weapons and fuel, which can increase drag substantially and significantly reduce the top speed.
2) Reaction time ; unless you can detect enemy aircraft from very very far, think at least 100NM, you likely won't have enough time to accelerate to your top speed, especially considering 1).
3) Obviously, this can cost a pretty significant amount of fuel to reach your top speed, which is why you don't really want to do it.

For example, take the Greeks' F-16CJ Block 52+ with CFTs, with a drag index of 50 at 40,000ft and a gross weight of 28,000lb, on page 666 : https://info.publicintelligence.net/HAF ... lement.pdf

On page 489, you can check the drag index values, so if I got this right, 6 AIM-120B's with their launchers and adapters would give a total drag index of 40 already, so DI=50 should represent a relatively lightly loaded F-16. Anyway, as you can see on the chart on page 666, with the settings mentioned above, it already takes 239 seconds, 49.2NM and 1,765lb of fuel to accelerate from Mach 0.82 to Mach 1.67. If you check page 487, you'd have 10,172lb of internal fuel on this plane, so you can see this dash uses quite a lot of fuel already when you take into account the takeoff, climb and possible patrolling time before the dash.

This is of course just for the F-16C+ Block 52, but based on what you can find for other 4th gen fighters, you'd see that they're all pretty far from their top speeds with any significant weapons load.

5th generation aircraft such as the F-22 and the F-35 (It's a little known fact but the specs of the F-35 call for it being able to reach Mach 1.6, with a full internal weapons load.) don't suffer from this extra drag (except the little extra induced drag created by the weight of the weapons), so you can expect them to accelerate more quickly and use a smaller percentage of their internal fuel when doing that. But even then, flying fast isn't necessarily tactically smart, because of aerodynamic heating, as shown on pp. 37-39 (49-51 in the PDF) in this CSBA report : http://csbaonline.org/uploads/documents ... eport-.pdf
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sprstdlyscottsmn

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Unread post06 Sep 2017, 01:42

viper12 wrote:
For example, take the Greeks' F-16CJ Block 52+ with CFTs, with a drag index of 50 at 40,000ft and a gross weight of 28,000lb, on page 666 : https://info.publicintelligence.net/HAF ... lement.pdf

On page 489, you can check the drag index values, so if I got this right, 6 AIM-120B's with their launchers and adapters would give a total drag index of 40 already, so DI=50 should represent a relatively lightly loaded F-16. Anyway, as you can see on the chart on page 666, with the settings mentioned above, it already takes 239 seconds, 49.2NM and 1,765lb of fuel to accelerate from Mach 0.82 to Mach 1.67. If you check page 487, you'd have 10,172lb of internal fuel on this plane, so you can see this dash uses quite a lot of fuel already when you take into account the takeoff, climb and possible patrolling time before the dash.

You actually didn't go quite far enough there. Looking At page 487 and down, you can see that the 28,000lb weight you used to calculate the acceleration and the payload you specified only leaves 4,015lb of fuel when you begin accelerating and only 2,250 remaining afterwards.
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viper12

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Unread post06 Sep 2017, 02:11

Oops. :oops:

Yeah, more realistic figures would involve using the 32K or 36K gross weight columns, which give even worse acceleration times, distances over which the acceleration takes place and fuel consumption.

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