A bit tough to follow but an RC glider hit 548 mph doing something called dynamic soaring. The glider is hard to see in the video but seems easy to pick up just as it crosses the peak of the hill.
Random note: the world speed skiing record is 158 mph.
Kinda curious, are we talking airspeed or groundspeed ?
Big difference.
article implies groundspeed; not sure though
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Kinda curious, are we talking airspeed or groundspeed ?
Big difference.
Laden or unladen?
African or European?
Not sure l follow …
Monty python
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Not sure l follow …
Monty Python.
As far as amateur / remote aeronautics go, I still think that the drone that flew up to 33,000 feet above Siberia is pretty impressive
Kinda curious, are we talking airspeed or groundspeed ?
Big difference.
And if it is airspeed, what airspeed? CAS?
It is recorded ground speed with radar. The airspeed varies greatly within the lap. That day the wind was gusting to 65.
The plane is 130 inches in wingspan and weighs about 350 oz.
Kinda curious, are we talking airspeed or groundspeed ?
Big difference.
Measured with radar, so ground speed.
The article said the glider "*hit the record breaking 548 miles per hour, or Mach 0.71. *Wind gusted to 65mph and temps were 45-50F."
I don’t know for sure whether they are talking about ground speed, indicated airspeed, or true airspeed, but Mach 0.71 would work out to 535 mph TAS at 50 degrees F. Maybe the 548 mph was the groundspeed?
At any rate, Mach 0.71 is pretty impressive for a glider with a high aspect ratio straight wing. For reference, if I pointed an A-10 straight down with full power at 20,000 feet, I could get up to the limiting mach number of 0.75, but it wouldn’t go any faster.
This might be a better article…
https://newatlas.com/aircraft/dynamic-soaring-speed-record-spencer-lisenby/
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It is strange that they would quote a mach number with groundspeed, as the mach no. varies with altitude …
https://www.youtube.com/watch?v=liIlW-ovx0Y&t=84s
come on, man.
The speed of sound depends on the temperature of the air. An airplane’s mach number changes with altitude for a given airspeed, but that’s because the temperature changes with altitude. Sound travels slower in colder air. It was no problem to go supersonic (707 mph) at 20,000 feet in an F-4 (colder air (-13 degrees F) along with less dense air). It wasn’t easy to go supersonic (761 mph) at sea level (58 Degrees F) in an F-4 when we had external tanks and bomb racks on the aircraft. The second article does a good job explaining how and why they use groundspeed as their measuring stick, but I thought the mach number was an interesting reference point.
The structural strength of this RC glider is incredible. According to the second linked article, "Nothing off the shelf could come close to handling the constant 60-80 G-loadings these things experience, with spikes as high as 120 g." 120 g’s! If it was a solid brick, that would be one thing, but they’ve got movable flight control surfaces along with the servos and actuators. That’s one heck of an engineering and construction challenge.
Kinda curious, are we talking airspeed or groundspeed ?
Big difference.
Laden or unladen?
African or European?
“How is it you know so much about swallows?â€
“You have to know these things when you’re a king.â€
(corrected)
As said by Alvin, mach (the speed of sound) in air varies pretty much with air temperature, and only slightly with density.
But, about the glider, if this is a groundspeed record, it seems odd for them to quote a mach no. for ground speed, that is not typically done. In any case, the gliders are impressive, but l would be far more interested to know what max indicated airspeed they hit …
Actually, its not about temperature. Mach varies with air density.
Sure, air density varies with temperature. But, as you know, air density also varies with altitude. So mach also varies with altitude completely independent of temperature.
You’re on the right track, but here are a couple of quotes from this linked paper.
“The speed of sound is a constant within a given gas and the value of the constant depends on the type of gas (air, pure oxygen, carbon dioxide, etc.) and the temperature of the gas.”
“The speed of sound in air depends on the type of gas and the temperature of the gas. On Earth, the atmosphere is composed of mostly diatomic nitrogen and oxygen, and the temperature depends on the altitude in a rather complex way. Scientists and engineers have created a mathematical model of the atmosphere to help them account for the changing effects of temperature with altitude.”
As you get higher, the air density does decrease (along with the temperature). Among other things, this affected how much “smash” or indicated airspeed we could get with our airplanes. Flor the A-10, there were calculations we could do, but mostly we would just go with some simple but pretty accurate estimates. For example, we could fly 300 KIAS at sea level and that would work out to about 300 KTAS. At 30,000 feet, you could only get an A-10 up to about 200 KIAS in level flight, but that would still work out to about 300 KTAS. (And you only burned about half as much gas cruising at high altitude.) And in the A-10, we didn’t worry about the mach number!