How long at high altitude.
 

Today I watched a Tornado pass over at high altitude.
It took 'longer' to move out of my field of view than if it had been 'just skimming the rooftops' (which is the usual transit where I live on a low-flying corridor).

My question is simple - ignoring the time taken to get to altitude (and descend), is there a difference in time taken between A and B at 50,000 ft and 500 ft?

What is the limit of cruising speed at 500 ft and 50,000 ft - does the speed of sound limit how fast aircraft can travel at altitude?

That would typically be true of any aircraft, it's just a function of how a given angle of view covers a lot more of an aircraft's flightpath at altitude compared to low level (think similar triangles).

The Tornado can manage around M1.2 (clean) at sea level. Max speed at altitude is about M2.2.

Thanks for your reply - I realise that 'perceived' time is greater at higher altitude, but is there a real difference in journey time - ie is it further at higher altitude, or is this just an impression?

I also accept that the potential speed of a Tornado is in excess of the speed of sound, but normal operations are at subsonic speeds (there was no sonic boom), but is there a limit (either physical or legislative) of actual speed between 500 ft and 50,000 ft?

Yikes...

Simple answer is a mile is a mile, high or low, and journey time is simply journey distance/average Speed over the ground (aka ground speed).

If the aircraft can maintain the same ground speed at both 500 feet and 50000 feet then journey times should be the same. I never flew the Norfolk land shark but I would have thought it could maintain a high subsonic ground speed of say 500-550 knots at both 500 feet and 50000 feet.

There is big difference in journey time.

If the do a bit of geometry on this you get two triangles -a high level one and low level one but the angles are the same in both. ( Easier to draw it but doing that on PP is beyond my abilities)

The distance line in the 50,000 feet case will be much much much longer than the lower level line.

However the difference in speed is at best only about 2 or 2.5 times for high versus low and this cannot compensate for the much greater distance flown.
indeed this iswhy since WW2 military aircraft have flown at low level so the transit time and reaction time from Triple A or missiles is extremely small compared to being able to track and aim carefully at something much higher up even if it is going a lot faster

PB

Given pax's answer maybe the OP needs to clarify whether the distance he is asking about is angular ( re the sightline - which pax answered ) or linear across the ground - how long to get from A to B (which I must admit is how I read it).

BTW pax unless my PC is playing up you might want to go and have a quick look at the "Regulating the BBC" thread.

My question is (or was) intended to be simple.

Travelling from (say Lossiemouth) to Marham, at whatever subsonic speed is possible, (and neglecting the time taken to reach 50,000 ft), would it take longer to travel at altitude rather than at 500 ft?

Considering the Earth and the space above it to be a sphere, the suggestion seems to be that flying higher would be further, but the difference relative to the circumference of the Earth suggest that the difference in distance would be negligible.

There is the complication that the speed of sound reduces with altitude due to the decrease in temperature, but there might be legislative limits to maximum speed at 500 ft.

Speed of sound at sea level 760 mph, speed of sound at 50,000 ft 670 mph (or thereabouts).

No problem, made me rethink it... and IMHO it's the answer I gave in my previous post:

"If the aircraft can maintain the same ground speed at both 500 feet and 50000 feet then journey times should be the same. .... I would have thought (a Tornado) it could maintain a high subsonic ground speed of say 500-550 knots at both 500 feet and 50000 feet."

TBF before someone points it out the realities - some aircraft can't maintain high ground speeds at low altitude, (e.g. airliners,) but will bat along at perhaps 500 knots plus ground speed at high level, other types would struggle flying lower ground speeds at high level ( thin air), but from flying something fast and pointy in a previous life I'd suspect/guess something like a Tornado or similar military fast jet should be OK both high and low.

Correct, but for most purposes and shorter ranges that difference is generally ignored.

Yes, 50,000 ft is approximately 15 km, compared to the Earth's radius of just under 6,400 km, so travelling anywhere at that altitude adds about 0.2% to the equivalent sea level distance

But the extra distance is massively outweighed by the fuel saved. :O

I am impressed that a Tonka can actually achieve a 'High Altitude' :cool:

It was obviously 'moving' with the wings swept back (which was my identification).

Unusual, as, I stated we are on a low-flying corridor from the Otterburn ranges so we usually just hear them rather than seeing them - though if they travel in pairs you can sometimes catch a glimpse of the wingman.

My best 'spot' was what I thought at first was an EE Lightning (though I knew that was impossible in 2004).
It was a very very brief glimpse at rooftop level which left me puzzled.
Then my 1950s ATC recognition days came to mind with the word 'Fitter'- it turned out to be a Polish Su-22 on a farewell tour (Lone Cat) to Coltishall.

Having got two answers to your question is it the same distance youare referign to or is it the time it remains in sight between two relatively close landmarks-I read it the latter way because you referred to rooftops

Wiggy

Yes, as you politely point out the question can be read both ways.

How I managed to simultaneously post it here and on the BBC thread I don't know but given the theme of that thread I thought I should 'make it relevant'

As you have probably gathered its an answer to another thread how it got posted on two seperate ones I don't know because it is on the one it is meant to be.

However it has got me thinking that I assumed the aircraft in question was transiting left to right which some JB readers may feel is unfairly biased against people who naturally assume the aircraft in question is flying from right to left. As the aircraft in question is a RAF Tornado and therefore publicly funded they may also feel that it shouldnt become involved in any such discussion anyway

Yeah, you can get into trouble over there - I suspect some would remove the red from the the RAF roundel if they could....or maybe the blue ....

:ok:

It has been a long time since that was possible for the GR; briefly in the late 1970s during the test programme and maybe as late as 1985 or '86. The undernose LRMTS knocked it down to Mach 1.4 max ( drag and kinematic heating ) and the deactivated intake ramps knocked another 0.1 off that. Once they're loaded-up with the Hindenburg tanks, self-defence pods and whatever ordnance for which they can find space they are strictly subsonic. One of the least efficient ways yet devised to deliver a Paveway.

Wiggy,

On JB I think the outcome would be to remove the Red from roundel and tail flash. Some there would remove the left wing of aircraft too, although I suspect they are happier calling it port wing for all sorts of reasons