Airliner speed/altitude
Thread Starter
Airliner speed/altitude
This is obviously a very hypothetical question, but there is a good reason for it.
If it was possible to fly a medium sized airliner straight and level very close to the ground, say about 50ft, in still air, would there be a threoretical maximum airspeed it can go at this altitude and would it differ greatly from its max at a higher altitude?
Thanks
If it was possible to fly a medium sized airliner straight and level very close to the ground, say about 50ft, in still air, would there be a threoretical maximum airspeed it can go at this altitude and would it differ greatly from its max at a higher altitude?
Thanks
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Are you talking about airspeed or mach no.?
Indicated airspeed doesn't vary with altitude as it's a relative measurement, but mach number will.
At high altitudes you will reach a given mach number at a lower airspeed than you would at a lower altitude. This is because mach no. is relative to the speed of sound, which will vary according to air density and temperature. Since both are lower at high altitudes, sound will propagate quicker, hence mach numbers will be achieved at lower airspeeds.
As for how fast an aircraft will go at 50ft, very fast! In fact it is likely the aircraft will start to fall apart before it reaches a finite speed.
Indicated airspeed doesn't vary with altitude as it's a relative measurement, but mach number will.
At high altitudes you will reach a given mach number at a lower airspeed than you would at a lower altitude. This is because mach no. is relative to the speed of sound, which will vary according to air density and temperature. Since both are lower at high altitudes, sound will propagate quicker, hence mach numbers will be achieved at lower airspeeds.
As for how fast an aircraft will go at 50ft, very fast! In fact it is likely the aircraft will start to fall apart before it reaches a finite speed.
Thread Starter
Thanks Regor,
yes I guess I mean Mach number. I have a job getting my head round these different figures
You mention that the aircraft would break up before it reached a given speed, and thats what this thread is about really. I have a 'friend' who has been reading some sensationalist crap about low flying airliners doing, and I quote '500mph just above the rooftops blah blah' (so I guess he's talking about groundspeed
).
Just wanted to get my facts straight before I put him right.
Cheers
yes I guess I mean Mach number. I have a job getting my head round these different figures
You mention that the aircraft would break up before it reached a given speed, and thats what this thread is about really. I have a 'friend' who has been reading some sensationalist crap about low flying airliners doing, and I quote '500mph just above the rooftops blah blah' (so I guess he's talking about groundspeed
).Just wanted to get my facts straight before I put him right.
Cheers
I REALLY SHOULDN'T BE HERE
Also at 50ft it is quite likely that in an a large aircraft you would start getting into ground effect so you will get a higher airspeed (theoretically) for a given thrust setting.
sr
sr
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This wouldn't have started the discussion, would it??
http://www.pentagonstrike.co.uk/flash.htm#Main
http://www.pentagonstrike.co.uk/flash.htm#Main
Thread Starter
Originally Posted by eyeinthesky
This wouldn't have started the discussion, would it??
http://www.pentagonstrike.co.uk/flash.htm#Main
http://www.pentagonstrike.co.uk/flash.htm#Main
No unfortunately its not. Its actually a local 'reporter' who has published a piece on 'low flying airliners travelling at 500mph ripping roof tiles off of houses'etc etc
. I was putting a letter together for our papers editor and I just wanted to get my facts straight first. My point being that a mid sized airliner wouldn't be able to physically go that fast at that altitude.
I wouldn't dignify the topic with a response AeroSpark. If there really were airliners doing 500mph at 50' (or even 1000'), the CAA would be quick to stop it. It would also be a topic on PPRuNe within about 40 secs.
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A little background information helps! No civil aeroplane would be at anywhere near that speed. What was in the hack's mind, no doubt, were occasional reports of rooftiles being ripped off near airports when vortexes from larger aeroplanes on final approach come to earth. Infrequent. The whole idea is to try and not build houses near airports.
