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It is fairly well known that the SR-71 holds the record for highest speed for a traditional aircraft (not a rocket/able to land and takeoff under its own power). However since the SR-71 flies much higher than other aircraft its indicated airspeed is comparatively low.

I was wondering what the fastest indicated airspeed achieved is and by which aircraft?

FreeMan
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pirocks
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    The highest would probably be when Space Shuttle lands into the atmosphere deep enough to be called an aircraft. – h22 Aug 19 '19 at 10:17
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    Touch I would not call the Space Shuttle a "traditional aircraft"... – tsg Aug 19 '19 at 10:30
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    @tsg A flying (falling) brick with winglets is still an aircraft I guess. – GittingGud Aug 19 '19 at 10:42
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    There have been a few aircraft that could get well above speed of sound at sea level. – Zeiss Ikon Aug 19 '19 at 12:42
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    I've found this: https://www.airspacemag.com/daily-planet/sultan-speed-180970800/, which seams to indicate that the low altitude speed record is just under 1000 mph. – pirocks Aug 20 '19 at 10:43
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    define "traditional aircraft". By my definition the SR-71 would classify, by yours apparently not? – jwenting Aug 22 '19 at 04:08
  • Sorry If I was unclear. The SR-71 would classify by my definition, but since it flies so high its indicated air speed is low (maximum of 400 knots). – pirocks Aug 23 '19 at 21:50
  • By my definition, an SR-71 is not traditional because it is a hybrid between a turbojet and a ramjet with afterburner. What is incredible about the modified J58 is that it had more to give. Some say Mach 5. Limiting factor was heat of the airframe. – Craig May 25 '20 at 04:27

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The world low-altitude speed record was set by Darryl Greenamyer in a rebuilt F-104 on 24 October 1977 at 988.26 mph (869.67 kts; 1'590.45 km/hr) and it wasn't really at sea level (mud lake Nevada on a hot day density altitude can be quite high so we don't know KIAS exactly). That airplane is by most considered to be the fastest due to small wind and frontal area. And it might also become one of the fastest land vehicle ever as some clever guy thought that getting rid of the wings was a good idea...

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The SR-71 had a designed airspeed limit of 500KEAS. It was design for high altitude flight and they did not bother about structural strength to withstand low altitude fast flight or high g loads flight as you can see in the full flight manual.

Other jet fighter were known to fly fast at low altitude during mission like the F-4 with operating procedures of 1.34 Mach (863 mph, 759.5kts, 1,389 km/h).

Finally more recently the F-16, not known as a fast airplane was nonetheless designed the limit of 800KIAS in mind. The canopy was meant to melt at 850KIAS and the engine supposedly would blow up at 854KIAS. And numerous reports show that the pilot had to pull back the throttle in order not to exceed the 800kts limit at sea level.

The reason why we don't have higher speed recorded is just that there are no need for it, the aircraft where therefore not designed to exceed "reasonable" speed and no-one was willing to push the limit further. The risk versus benefits to bet on some engineers over-designing their aircraft so that they would fly above their limit speed is just not worth it. But I'm pretty sure if you where to "floor" a MiG-29/31 or a f15 up to failure you would certainly exceed those speed. It's like the longest flight, some records won't probably ever be tried again.

MaximEck
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    Re: "It's like the longest flight, some records won't probably never be tried again." Yep, just like sailplane endurance records, all you prove is that the wind can blow against a ridge for a really long time, and a pilot can stay awake for a really long time, until he doesn't. So no one keeps track of those records any more. – quiet flyer Sep 23 '20 at 20:13
  • Yeah but the 64days straight in a Cessna will remain my absolute favourite/supidest one ^^ – MaximEck Sep 23 '20 at 22:00
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    "won't probably never"? – DKNguyen Sep 23 '20 at 22:25
  • Typo, feel free to correct them by editing the answer if you find any more of them. – MaximEck Sep 23 '20 at 22:35
  • Practically all supersonic jets are speed-limited by structural strength rather than by thrust at low (and mid) altitudes. MiG-29 and 31 are too different to be written like 29/31; perhaps 25/31 would do, but like SR-71, they were designed for high Mach rather than high IAS. MiG-29, on the other hand, is officially limited to 1500 km/h, which is 810 KIAS. – Zeus Sep 24 '20 at 01:14
  • @Zeus correct, but we all know Russian engineering is all about stronger things. They still have rockets from the 60's flying perfectly well. So maybe we could excess the 810 KIAS design limit on the MiG29 as the structure might be a bit over-designed, and I added the MiG31 as even if it was meant to intercept SR-71, it had such oversized engines thrust wouldn't be the issue and the structure looks more sturdy than a SR71 – MaximEck Sep 24 '20 at 06:24