What fixed wing, and motor, plane or jet, has the largest range between its minimum and its maximum airspeed by which it can safely fly for prolonged periods?
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3$\begingroup$ "Speed" is an ambiguous word when it comes to aircraft. Can we assume you're asking about true airspeed? $\endgroup$– PondlifeFeb 3, 2021 at 22:40
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3$\begingroup$ The question title asks for speed ratio (i.e. vmax/vmin) , the body asks for speed range (i.e. vmax - vmin). What do you want? The winner of the ratio contest will have a very low minimum speed, the winner of the range contest will have very high maximum speed. $\endgroup$– DeltaLima ♦Feb 3, 2021 at 23:05
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6$\begingroup$ What is a "prolonged period"? The F-35 can hover in flight, and has a top speed of mach 1.6 (1066 knots)... $\endgroup$– Ron BeyerFeb 4, 2021 at 0:29
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1$\begingroup$ Even notwithstanding the F-35, anything with a TWR > 1 can, to some degree or another, do this. $\endgroup$– J...Feb 4, 2021 at 16:56
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1$\begingroup$ I'd love to reopen this, but... not until the disconnect between "range" and "ratio" is resolved, the upper end being in TAS or IAS is specified, and VTOLs + gliders (and the Space Shuttle) being clearly ruled in or out. Until then, "needs clarity" remains the problem. $\endgroup$– Ralph J ♦Feb 11, 2021 at 4:42
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3 Answers
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The radio-controlled model sailplane that recently exceeded 540 mph while dynamic soaring has to be a contender. Minimum speed in this flight (immediately after launch) may have been as low as 10 mph, which probably could have been sustained by staying on the front side of the ridge.
Link to You Tube video--
Though any plane capable of routine flight at 0 mph would automatically win I suppose-- e.g. pretty much any hang glider or sailplane given the right conditions.
Or did you mean airspeed? The radio-controlled sailplane in the video may well be one of the top contenders.
answered Feb 3, 2021 at 22:29
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$\begingroup$ I admit it, having a little fun with opening up the box on what the meaning of "prolonged periods" might be, and a few other possible issues with the original question-- but the wind can likely blow longer than the typical fuel payload will last--! $\endgroup$ Feb 4, 2021 at 2:04
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The highest range of speeds will basically match up with a list of highest top speeds... take ~200 knots off of the top speed of the SR-71, and you probably have your answer. Or if the question is for currently flying jets, unless your #1 and #2 have top speeds so close that the delta in their landing speeds is greater than the delta in their max speeds, #1 is still first, #2 is second, and so on.
As for ratio, if VTOL jets aren't ruled out by the "fixed wing and motor" constraint (and actually, the nozzles pivot, not the motor, in most cases), you have to deal with an infinite ratio for a min speed of zero.
The dynamic soaring answer is inventive (and that video is amazing), and nothing else is likely to touch a 54X ratio (!!!), but the "and motor" constraint probably rules that one out too.
Even with VTOL ruled out, lowest landing speed is probably going to trump everything else; the garden-variety STOL single-engine prop with a range of 30-150 gets a ratio of 5x without even trying; the number of jets that land at 100 and reach 500 knots indicated is awfully small.
Oh, and for one more complication, are we talking KIAS or KTAS at the high end? That can make a difference too!
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$\begingroup$ I actually misread or mis-interpreted the question to be asking about "ratio" rather than "range" -- some parts of my answer make more sense with that in mind. Since the question says "range", this is a better answer -- except that the title says "ratio". Really we should have asked for the question+title to be clarified/ improved before offering any answers... $\endgroup$ Feb 4, 2021 at 13:46
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The Space Shuttle (or "Space Transportation System (STS)") reportedly re-entered the atmosphere from low Earth orbit at about 17,500 mph, and touched down as low as 214 mph, for a ratio of 81.77.
https://www.nasa.gov/mission_pages/shuttle/launch/landing101.html
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7$\begingroup$ Not sure the full speed range would count here. Until the lift-to-drag ratio gets above 1, the Shuttle can't be said to have been flying; at most, it would have been falling with style. $\endgroup$– MarkFeb 4, 2021 at 9:36
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1$\begingroup$ @Mark Not to mention that the shuttle wasn't generally powered on the way down, so not really any more of a contender than that model glider. $\endgroup$– MikeBFeb 4, 2021 at 16:29
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1$\begingroup$ @MikeBrockington How about on the way up? It's powered then, its thrust vector points straight backwards, and it starts flying with a speed just above zero, while ending up at orbital velocity. :) Of course, if it weren't for the "plane" constraint, then it still wouldn't win, due to other vehicles having exceeded escape velocity. $\endgroup$– reirabFeb 4, 2021 at 18:14
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$\begingroup$ @reirab Don't think it counts as an aeroplane on the way up - 99.9% ballistic, if not 100%, so not really 'flying', is it? $\endgroup$– MikeBFeb 5, 2021 at 10:54
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$\begingroup$ @MikeBrockington I mean, it's still an airplane... just one that happens to not be using its wings to generate lift at the time. :) Similar to a fighter or aerobatic plane with TWR > 1 standing on its tail or accelerating straight up. $\endgroup$– reirabFeb 5, 2021 at 16:10