Loneliest cruising altitude
Thread Starter
Loneliest cruising altitude
People often try to avoid flying at 'standard' altitudes, and a little while ago there was a discussion about the best cruising altitude if you don't want to meet people coming the other way. What altitude would you be most likely to choose? Please don't over-think the question - just pick the number that seems best to you.
Poll - EasyPolls.net
Poll - EasyPolls.net
Last edited by abgd; 18th Apr 2013 at 07:00.
Thread Starter
p.s. please don't discuss the poll until results are in to avoid biasing other respondents. I'll report them on this thread in due course.
Thread Starter
@phiggsbroadband -
Do you mean I missed out the whole numbers of thousands? e.g. xn00, (x+1)n00, (x+2)n00?
I did so intentionally - it would have made the poll too big if I had included them. Also, we all have different aircraft with different capabilities, and we may fly with very different goals. Including the thousands would just muddy the waters.
Do you mean I missed out the whole numbers of thousands? e.g. xn00, (x+1)n00, (x+2)n00?
I did so intentionally - it would have made the poll too big if I had included them. Also, we all have different aircraft with different capabilities, and we may fly with very different goals. Including the thousands would just muddy the waters.
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Hi abgd, it's just that my favourite level is somewhere between 7000ft and 9000ft... just above the tops if I can get there and maintain vfr. It is also the most efficient height for my normally aspirated plane. Vis is usually 50+nm and I have yet to see any other aircraft heading towards me.
By choosing just the hundreds, you can have a dozen or more planes stacked separately by 1000ft each, and yet they would never bump into each other.
There is also a factor of the wind gradient to take into account; There is little point, on some days, of climbing into very strong headwinds, when the lower winds are backed and calmer.
But where in GB can you put a straight line of over 100nm on your Chart at 9000ft, without bumping into Controlled Air Space?
By choosing just the hundreds, you can have a dozen or more planes stacked separately by 1000ft each, and yet they would never bump into each other.
There is also a factor of the wind gradient to take into account; There is little point, on some days, of climbing into very strong headwinds, when the lower winds are backed and calmer.
But where in GB can you put a straight line of over 100nm on your Chart at 9000ft, without bumping into Controlled Air Space?
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Don't forget on a day with good thermals, in class G there will be a raft of gliders as high as they can get, and definitely not operating at set altitude intervals. But they'll be below cloudbase and not above the tops.
I always felt that the Grob Tutor/glider midair near Didcot the other year may have partly resulted from the Grob pilot thinking that he was at a "safe" height for some aerobatics
I always felt that the Grob Tutor/glider midair near Didcot the other year may have partly resulted from the Grob pilot thinking that he was at a "safe" height for some aerobatics
Last edited by astir 8; 18th Apr 2013 at 23:18.
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the secret
in the US there are high altitude ATC sectors (enroute) and low altitude sectors....ifyou fly shorter routes (say less than 500 miles) the secret to jet direct is to fly at the highest altitude in the low altitude sectors (22-23) and getting direct!~
Many years ago I remember being in London Mil when a rather exotic callsign was being worked. He did not have mode charlie on but said he would select mode C when descending through FL600 which he duly did. I dont think he was worried about conflicting traffic in the cruise!
Astir 8.
And don't forget that on a day with good wave, gliders will be happily cruising at 9,000-10,000ft and well above the tops.
And don't forget that on a day with good wave, gliders will be happily cruising at 9,000-10,000ft and well above the tops.
Last edited by snapper1; 19th Apr 2013 at 18:17.
And don't forget that on a day with good wave, gliders will be happily cruising at 9,000-10,000ft and well above the tops
OBTW and on-topic the 17,800 ft altitude was completely deserted.
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Effective Cruising in GB.
Hi, just as a bit of an exercise I tried to find some routes on the Southern UK Chart where you could Cruise VFR for 100nm at FL090. There seem to be just two...
Coal Aston to Ipswich/Monewden, 119nm.
and
Lands End to Swansea, 109nm.
These would require you to reach and descend from FL090 in 19 and 9nm resp.
There may be longer routes from Lands End into Caernarfon, but this requires a lot of Danger Zone and Water Crossing.
Coal Aston to Ipswich/Monewden, 119nm.
and
Lands End to Swansea, 109nm.
These would require you to reach and descend from FL090 in 19 and 9nm resp.
There may be longer routes from Lands End into Caernarfon, but this requires a lot of Danger Zone and Water Crossing.
Thread Starter
OK... I'm sorry for the delay in posting results. Sometimes life gets busy. I quite agree with the frustration some people feel when confronted with such an odd question. However, I did have a halfway sensible rationale behind it. It relates to a trick many pilots use to reduce the risk of a mid-air collision, which is to fly at a 'random' altitude, the assumption being that most other pilots will be flying at 'round' altitudes such as 2000 feet, or 1500 feet.
There's a children's game where if you ask someone to think of a vegetable under time pressure, almost everybody thinks of a carrot. If you ask people to think of a flower, most people think of a rose. But what if you ask people to think of a random number - for example a random altitude?
There's unfortunately surprisingly little research on this, though what little I've seen tends to suggest that we also have prototypical 'random' numbers that we prefer. And intuitively 2300 feet somehow seems more random than 2000 feet or 2500 feet, doesn't it? It does to me, though of course I know that 'randomness' occurs in the process of selecting an altitude, not in the individual result.
In my polls, I randomised the order of presentation of the altitudes to try and avoid any bias due to page position, and posted different versions of the same quizes on several fora. I'm not particularly serious about this question and I'm sure I could have carried out the questionnaires more rigorously, but it's a start. And the results were significant, both in practical and statistical terms.
This first graph shows the altitudes pilots select if they consciously choose to pick a 'random' cruising altitude.
"Many pilots try to pick 'random' cruising altitudes in order to reduce the risk of mid-air collisions.
Ignoring all other considerations, if you were trying to use this strategy on a VFR flight, which altitude would you be most likely to pick?"
182 responses - risk of collision 150% greater than the theoretical optimum.
The result is clearly biased towards '3' and '7', which I had predicted, though '2' and '8' surprised me in their popularity. '2' was only really popular on one forum, which made me wonder whether someone was possibly trying to fiddle the results. However '3' was popular on every forum where I posted the quiz, whatever order the options were presented in.
However, not every pilot knows the 'trick'. What altitudes do people actually fly at? The best way to do this would be to sit watching mode-C returns over Wales or Scotland - somewhere where people choose altitudes on the basis of preference rather than compulsion - we often don't have much choice. However, that's not something I currently have the time to do so I posted a separate poll elsewhere asking people to pick an altitude.
"It's a fine day for a VFR flight, and you can choose to fly at whatever level you want. Pick your favourite cruising altitude, and select the whole number of hundreds-of-feet on the poll below. Thanks!"
112 responses altogether. Risk of collision 152% greater than the theoretical optimum.
The result - to my eye - shows a mix of 'random' cruising altitudes, with the big round numbers of thousands of feet, or five-hundred foot increments. Perhaps surprisingly here, people have tended towards lower numbers rather than higher numbers. i.e. x200 feet seems much more popular than x800 feet.
~~~~
Working from the reasoning that the risk of collision increases with the square of traffic density, it's possible to calculate a theoretical optimum if traffic were evenly spread throughout ten possible cruising levels offered as options... which begs the question 'why only ten options'. It's a good question to which I don't have a ready answer, except to point out that most of us are limited in our altitude-keeping ability. I realistically keep within about +/- 100 feet most of the time. Perhaps some of you do much better. However, there's no advantage to aiming to fly at 10 foot increments if we're straying so far from our allotted altitude. Really I picked hundreds of feet simply because that's how we normally report our altitude. I never heard anybody say they were currently at '1775 feet'.
Whenever traffic is spread unevenly, risk of collision increases above the optimum. e.g. if pilots fly at whole 1000s of feet, the risk is 10 times greater than the optimum (assuming 100 foot increments).
Someone on another forum quite reasonably pointed out that there are advantages to flying according to quadrantal rules - though under EASA I understand that we're moving towards the semicircular rules in line with the rest of the world. If we restricted ourselves to 500 foot increments, our theoretical risk of collision would be 5 times greater than the 'optimal' risk. Of course it's mitigated by the fact that we are now less likely to meet another pilot on a reciprocal heading (though closing speeds may remain quite substantial). Does this mitigation outweigh the relatively large risk increase by confining ourselves to just two levels per 1000 feet? Quite possibly. I don't know.
Perhaps the ideal would be to combine the two techniques:
Take the last digit of the day of the month in your birthday - e.g. 16 february. Add or subtract 5 - whichever leaves you with a positive, single digit answer. You now have two single digits, 1 and 6. Fly quadrantal rules, but instead of flying at x000 feet, fly at x100 feet. Instead of flying at x500 feet, fly at x600 feet. If everybody did this you would be relatively unlikely to meet anybody going the opposite direction, and you would also spread out the traffic almost evenly over the available airspace.
~~~~~
Another point is simply that en-route mid-air collisions are vanishingly rare and not really something to worry about unduly.
So arguably fairly pointless, but I had fun anyway. Thanks to everyone who filled in the polls.
There's a children's game where if you ask someone to think of a vegetable under time pressure, almost everybody thinks of a carrot. If you ask people to think of a flower, most people think of a rose. But what if you ask people to think of a random number - for example a random altitude?
There's unfortunately surprisingly little research on this, though what little I've seen tends to suggest that we also have prototypical 'random' numbers that we prefer. And intuitively 2300 feet somehow seems more random than 2000 feet or 2500 feet, doesn't it? It does to me, though of course I know that 'randomness' occurs in the process of selecting an altitude, not in the individual result.
In my polls, I randomised the order of presentation of the altitudes to try and avoid any bias due to page position, and posted different versions of the same quizes on several fora. I'm not particularly serious about this question and I'm sure I could have carried out the questionnaires more rigorously, but it's a start. And the results were significant, both in practical and statistical terms.
This first graph shows the altitudes pilots select if they consciously choose to pick a 'random' cruising altitude.
"Many pilots try to pick 'random' cruising altitudes in order to reduce the risk of mid-air collisions.
Ignoring all other considerations, if you were trying to use this strategy on a VFR flight, which altitude would you be most likely to pick?"
182 responses - risk of collision 150% greater than the theoretical optimum.
The result is clearly biased towards '3' and '7', which I had predicted, though '2' and '8' surprised me in their popularity. '2' was only really popular on one forum, which made me wonder whether someone was possibly trying to fiddle the results. However '3' was popular on every forum where I posted the quiz, whatever order the options were presented in.
However, not every pilot knows the 'trick'. What altitudes do people actually fly at? The best way to do this would be to sit watching mode-C returns over Wales or Scotland - somewhere where people choose altitudes on the basis of preference rather than compulsion - we often don't have much choice. However, that's not something I currently have the time to do so I posted a separate poll elsewhere asking people to pick an altitude.
"It's a fine day for a VFR flight, and you can choose to fly at whatever level you want. Pick your favourite cruising altitude, and select the whole number of hundreds-of-feet on the poll below. Thanks!"
112 responses altogether. Risk of collision 152% greater than the theoretical optimum.
The result - to my eye - shows a mix of 'random' cruising altitudes, with the big round numbers of thousands of feet, or five-hundred foot increments. Perhaps surprisingly here, people have tended towards lower numbers rather than higher numbers. i.e. x200 feet seems much more popular than x800 feet.
~~~~
Working from the reasoning that the risk of collision increases with the square of traffic density, it's possible to calculate a theoretical optimum if traffic were evenly spread throughout ten possible cruising levels offered as options... which begs the question 'why only ten options'. It's a good question to which I don't have a ready answer, except to point out that most of us are limited in our altitude-keeping ability. I realistically keep within about +/- 100 feet most of the time. Perhaps some of you do much better. However, there's no advantage to aiming to fly at 10 foot increments if we're straying so far from our allotted altitude. Really I picked hundreds of feet simply because that's how we normally report our altitude. I never heard anybody say they were currently at '1775 feet'.
Whenever traffic is spread unevenly, risk of collision increases above the optimum. e.g. if pilots fly at whole 1000s of feet, the risk is 10 times greater than the optimum (assuming 100 foot increments).
Someone on another forum quite reasonably pointed out that there are advantages to flying according to quadrantal rules - though under EASA I understand that we're moving towards the semicircular rules in line with the rest of the world. If we restricted ourselves to 500 foot increments, our theoretical risk of collision would be 5 times greater than the 'optimal' risk. Of course it's mitigated by the fact that we are now less likely to meet another pilot on a reciprocal heading (though closing speeds may remain quite substantial). Does this mitigation outweigh the relatively large risk increase by confining ourselves to just two levels per 1000 feet? Quite possibly. I don't know.
Perhaps the ideal would be to combine the two techniques:
Take the last digit of the day of the month in your birthday - e.g. 16 february. Add or subtract 5 - whichever leaves you with a positive, single digit answer. You now have two single digits, 1 and 6. Fly quadrantal rules, but instead of flying at x000 feet, fly at x100 feet. Instead of flying at x500 feet, fly at x600 feet. If everybody did this you would be relatively unlikely to meet anybody going the opposite direction, and you would also spread out the traffic almost evenly over the available airspace.
~~~~~
Another point is simply that en-route mid-air collisions are vanishingly rare and not really something to worry about unduly.
So arguably fairly pointless, but I had fun anyway. Thanks to everyone who filled in the polls.
Last edited by abgd; 25th Jun 2013 at 00:59.
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I never heard anybody say they were currently at '1775 feet'.
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Now this example of is valid in the the US mostly, but anything above oxygen level (12500ft), but below the flight levels (FL180) is pretty much empty. I went back at 14500ft for close to 5hrs the other day and didn't have a single traffic call from ATC. I assume it's similar in Europe and I seem to recall Peter337 always mentioning that's the case on his Euro travels.
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Actually, I believe your assumptions are incorrect.
If we are all flying VFR, then there's no issue, and you may be correct, however when you have planes travelling IFR then you have issues, because your idea of picking some random flight level means that you could be choosing one that is head-on with another plane. Head-on is much harder to see and avoid than parallel.
If we are all flying VFR, then there's no issue, and you may be correct, however when you have planes travelling IFR then you have issues, because your idea of picking some random flight level means that you could be choosing one that is head-on with another plane. Head-on is much harder to see and avoid than parallel.
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Most of the traffic I talk to in my day job at "Scottish Information" sits in the not above 3500ft bracket...and on nice days there is an awful lot of traffic around at those levels......very rare indeed to talk to much above those levels!......so the moral of the story is keep a VERY good look out and if your not talking to ATC why not consider giving us a call as I am only able to advise traffic of other traffic if you have told me your there in the first place! 
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Ironically, of course, your study will no longer be valid as the results will change the altitudes chosen. Me I'm off for the 900s from now on!
Interesting study abgd, thanks for sharing.
BB
Interesting study abgd, thanks for sharing.
BB