coriolis and pilot correction
Thread Starter
coriolis and pilot correction
From the manual of aviation meteorology-put out by the commonwealth bureau of meteorology in Oz.
After a very un-comprehensive definition of what it is they state "Pilots must make navigational corrections to allow for Coriolis effect"
I have never intentionally done that....what are they talking about. What is the adjustment? Is it in the planning stages, the inflight stages etc.
Help would be appreciated.
After a very un-comprehensive definition of what it is they state "Pilots must make navigational corrections to allow for Coriolis effect"
I have never intentionally done that....what are they talking about. What is the adjustment? Is it in the planning stages, the inflight stages etc.
Help would be appreciated.
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
cwc - I think you can relax. I have got away with it for years. IF you conduct your navigation on a space-frame orientation you will probably need to correct for Coriolis. IF, however, you navigate between points on the earth's surface using earth-based references (heading, track, 'normal' INS, drift etc) you should be OK. If, however, you consistently find yourself missing your destination to the left in Oz, I would tweak it a couple of degrees right.
Any chance of a link to the "commonwealth bureau of meteorology" article? I'm always looking for a new drift on ideas.
Any chance of a link to the "commonwealth bureau of meteorology" article? I'm always looking for a new drift on ideas.
Join Date: Aug 1999
Location: England
Posts: 1,050
Likes: 0
Received 0 Likes
on
0 Posts
I've wondered about this.
As a 'northern hemisphere guy' I have noticed that students seem to be more liekly to end up off track to the right. But of course that could be due to some other factor - maybe a sub conscious tendancy to want to unmask the area beneath the left hand side of the nose.
I guess it would be worth calculating it.
ISTR reading that it's a significant factor in long range gunnery. So if its a factor for guns firing shells at ? several hundred metres a second for a few miles, it ought to be a factor for aeroplanes travelling a bit slower but far further.
I might do some sums later
pb
As a 'northern hemisphere guy' I have noticed that students seem to be more liekly to end up off track to the right. But of course that could be due to some other factor - maybe a sub conscious tendancy to want to unmask the area beneath the left hand side of the nose.
I guess it would be worth calculating it.
ISTR reading that it's a significant factor in long range gunnery. So if its a factor for guns firing shells at ? several hundred metres a second for a few miles, it ought to be a factor for aeroplanes travelling a bit slower but far further.
I might do some sums later
pb
Moderator
.. then again, for those with my standard of navigation excellence ... Coriolis considerations tends to get lost in the scatter .. and, as I recall, I've never ended up more than just a teensy bit lost for a minute or so.
Join Date: Aug 2003
Location: Sale, Australia
Age: 80
Posts: 3,832
Likes: 0
Received 0 Likes
on
0 Posts
I've never ended up more than just a teensy bit lost for a minute or so
Moderator
Must be the consummate aviator JT
Not at all, Brian .. just had a very sheltered and protected life.
Plus, in periods of navigational terror, time slows right down .. maybe I embellished the story a tad ... the worst might have been that time where I had not the slightest idea where I was during a tow from A to B with two on lines ... had to outfield and ask a farmer where I was .. thank heavens for the flexibility of SuperCubs ... we'd been running around thunderies and in and out of scud for the previous couple of hours or so. We knew where we were probably to an accuracy of 40 or 50 miles but that wasn't much use on the day ... so an outfielder it was ...
Sometimes I wonder how any of us survive being young, overconfident, stupid and overflowing with testosterone.
The best tale, although I can't recall the TP's name just now, was the fellow who observed in respect of the SR71 .. "you ain't never been lost ... until you've been lost at Mach 3".
Not at all, Brian .. just had a very sheltered and protected life.
Plus, in periods of navigational terror, time slows right down .. maybe I embellished the story a tad ... the worst might have been that time where I had not the slightest idea where I was during a tow from A to B with two on lines ... had to outfield and ask a farmer where I was .. thank heavens for the flexibility of SuperCubs ... we'd been running around thunderies and in and out of scud for the previous couple of hours or so. We knew where we were probably to an accuracy of 40 or 50 miles but that wasn't much use on the day ... so an outfielder it was ...
Sometimes I wonder how any of us survive being young, overconfident, stupid and overflowing with testosterone.
The best tale, although I can't recall the TP's name just now, was the fellow who observed in respect of the SR71 .. "you ain't never been lost ... until you've been lost at Mach 3".
Join Date: Mar 2005
Location: Uh... Where was I?
Posts: 1,338
Likes: 0
Received 0 Likes
on
0 Posts
I had a Navigation teacher from the Air Force who was considered the expert of the experts. He used to say:
"When you have applied a wind correction angle you have also allowed for Coriolis" because the wind direction and speed was determined by Coriolis effect and the airplane is "inside" the wind.
He added that, unlike the artillery guys, pilots did not need to allow for Coriolis. Maybe he just wanted us to stop making questions on that matter...
Maybe it has to do with time? A shell from a gun gets from A to B in a very short time, and moves real fast. Let's suppose that the air mass within which it moves has not the time required to make the shell drift as it would make it if it remained a longer time in the air. Airplanes, however, stay in the air for hours so they are drifted (and "Coriolisized") by the wind.
What do you think?
"When you have applied a wind correction angle you have also allowed for Coriolis" because the wind direction and speed was determined by Coriolis effect and the airplane is "inside" the wind.
He added that, unlike the artillery guys, pilots did not need to allow for Coriolis. Maybe he just wanted us to stop making questions on that matter...
Maybe it has to do with time? A shell from a gun gets from A to B in a very short time, and moves real fast. Let's suppose that the air mass within which it moves has not the time required to make the shell drift as it would make it if it remained a longer time in the air. Airplanes, however, stay in the air for hours so they are drifted (and "Coriolisized") by the wind.
What do you think?
Join Date: Jun 2009
Location: The North
Posts: 41
Likes: 0
Received 0 Likes
on
0 Posts
In my simple world there are 2 big differences between artillery and aircraft which make it not worth worrying about Coriolis effect in the latter.
Firstly once a shell is fired that's where it's heading so all the calculations beforehand have to take everything into account, whereas an aircraft can be constantly corrected until the destination.
Secondly, a shell is relatively small, dense and fast compared to most aircraft and so the effect of wind, etc will be relatively less and other effects relatively greater. In an aircraft wouldn't the wind effect make any Coriolis effect negligible ?
Cue someone to tell me I'm talking rubbish
Firstly once a shell is fired that's where it's heading so all the calculations beforehand have to take everything into account, whereas an aircraft can be constantly corrected until the destination.
Secondly, a shell is relatively small, dense and fast compared to most aircraft and so the effect of wind, etc will be relatively less and other effects relatively greater. In an aircraft wouldn't the wind effect make any Coriolis effect negligible ?
Cue someone to tell me I'm talking rubbish
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
As JT says
The effect is all due to the rotation of the earth in space and your motion around an object. The black magic' involved in constraining the space-frame references to the earth-frame are wondrous..(refer Newton's First Law).
If you were able to 'hover' over a point on the equator for 12 hours, starting facing east and making NO changes to your 'space' attitude, you would finish up inverted and pointing west.
Similarly, if you started 'hovering' at 60 North, facing north and made no changes, you would arrive inverted and severely 'nose-up' after 12 hours but still 'pointing' north.
Setting off from the UK, pointing east (with a space referenced attitude) and aiming to fly to a point 'due east' you would see that point gradually move to the left of your nose as the earth rotates until it arrives behind you after 12 hours. This is the dilemma the poor old shell faces since its motion vector is 'in space'. Since your aircraft's motion is also a vector 'in space', you are a little like the shell. However, unless we are planning a long period of 'DR', as JT says, the Coriolis effect is lost in the constant corrections you make to stay 'on track' with wind changes, heading deviations and the like, not to mention using 'magnetic' directions with varying variation............. To stay pointing 'east' (magnetic) requires constant changes in some or all of pitch, roll and yaw to maintain - again fixed changes due to earth's rotation and variable according to your speed. Once you start following a 'line on the map' or tracking a radial or following an INS track, the 'corrections' required just 'happen'. The line on the map and the radial are all based on an earth reference and thus correct automatically. The INS has built in corrections to its space reference for earth rotation (earth rate) and your movement across the surface (profile rate) so it 'knows' the corrections it needs to apply to your space attitude to 'allow' for earth rotation and your motion across it. If I were Sir Francis Chichester in 'Gypsy Moth' aiming for that little island in the Pacific 10 hours away, yes, I would allow for it. For 'modern' flying, as I said, just relax
Phew!
Coriolis considerations tends to get lost in the scatter
If you were able to 'hover' over a point on the equator for 12 hours, starting facing east and making NO changes to your 'space' attitude, you would finish up inverted and pointing west.
Similarly, if you started 'hovering' at 60 North, facing north and made no changes, you would arrive inverted and severely 'nose-up' after 12 hours but still 'pointing' north.
Setting off from the UK, pointing east (with a space referenced attitude) and aiming to fly to a point 'due east' you would see that point gradually move to the left of your nose as the earth rotates until it arrives behind you after 12 hours. This is the dilemma the poor old shell faces since its motion vector is 'in space'. Since your aircraft's motion is also a vector 'in space', you are a little like the shell. However, unless we are planning a long period of 'DR', as JT says, the Coriolis effect is lost in the constant corrections you make to stay 'on track' with wind changes, heading deviations and the like, not to mention using 'magnetic' directions with varying variation............. To stay pointing 'east' (magnetic) requires constant changes in some or all of pitch, roll and yaw to maintain - again fixed changes due to earth's rotation and variable according to your speed. Once you start following a 'line on the map' or tracking a radial or following an INS track, the 'corrections' required just 'happen'. The line on the map and the radial are all based on an earth reference and thus correct automatically. The INS has built in corrections to its space reference for earth rotation (earth rate) and your movement across the surface (profile rate) so it 'knows' the corrections it needs to apply to your space attitude to 'allow' for earth rotation and your motion across it. If I were Sir Francis Chichester in 'Gypsy Moth' aiming for that little island in the Pacific 10 hours away, yes, I would allow for it. For 'modern' flying, as I said, just relax
Phew!
Moderator
Three observations ..
(a) BOAC knows a lot more about Coriolis than I
(b) all roads lead back to Einstein
(c) all wisdom may be found neatly encapsulated within one limerick or another .. while the following is probably more useful when talking about wormholes and time dilation considerations, it must be relevant to Coriolis somewhere along the way ..
There once was a lady named bright
Who traveled much faster than light
She departed one day in a relative way
and came home the previous night.
(a) BOAC knows a lot more about Coriolis than I
(b) all roads lead back to Einstein
(c) all wisdom may be found neatly encapsulated within one limerick or another .. while the following is probably more useful when talking about wormholes and time dilation considerations, it must be relevant to Coriolis somewhere along the way ..
There once was a lady named bright
Who traveled much faster than light
She departed one day in a relative way
and came home the previous night.
Join Date: Jun 2002
Location: Vega Constellation
Posts: 286
Likes: 0
Received 0 Likes
on
0 Posts
Mmmhh... I thought Coriolis was applied to moving systems, not fixed ones..as far as I remembered.
But what BOAC presented, although entirely correct, seems to be "just" gyroscopic precession, not Coriolis effect, which in itself does not exist for a fixed object, but applies to a moving system, like the curve induced on a bullet trajectory (thought minimal) or a weather system.
Please correct as needed,
Flex
But what BOAC presented, although entirely correct, seems to be "just" gyroscopic precession, not Coriolis effect, which in itself does not exist for a fixed object, but applies to a moving system, like the curve induced on a bullet trajectory (thought minimal) or a weather system.
Please correct as needed,
Flex
Join Date: Jul 2007
Location: Germany
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
I know long range artillery make corrections for it, not sure about us though....
Artillery and Coriolis
Its all to do with reference frames, so probably has an effect on INS?
Coriolis effect - Wikipedia, the free encyclopedia
Artillery and Coriolis
More recent developments in the science of ballistics make the Coriolis effect more significant. For instance, a German gun of 21-cm bore called �Big Bertha� was used in 1918 to shell Paris from a distance of 122 km. Over such distances the inclusion of the Coriolis effect is at least as important as the consideration of deflection by the wind.
Coriolis effect - Wikipedia, the free encyclopedia
Per Ardua ad Astraeus
Join Date: Mar 2000
Location: UK
Posts: 18,579
Likes: 0
Received 0 Likes
on
0 Posts
Yes - I'm stunned too
Flex - NB I did include "your motion around an object" but the point I was trying to make was, as JT said, that the Coriolis effect, for controllable objects (unlike Big Bertha - she was wild) is effectively lost in all the other 'tweaks' we automatically make every second or so. EG did you realise that as you fly around the globe at, say, 450kts you need to keep adjusting your pitch nose down by 0.125 degrees a minute? I guess not. Heading north from the equator there will initially be a similar correction required in roll - all due to our 'motion' being relative to a space frame, but conducted in an earth-frame. All of this, of course, taken care of by our attitude reference systems (be they Mk I eyeballs, gyro Art Horizons, IRS or a black cat sitting on the coaming with its tail hanging over the panel) which are artificially 'tied' to the earth frame and we just do not see it. The ISS and Shuttle do not care much for all of this and generally maintain their 'space' attitude. Now convince me we will 'notice' the Coriolis effect!
Incidentally, it is the other gyro 'property' - 'rigidity' - not 'precession' that we are talking about. If I may summarise - Coriolis effect is there. It does affect our motion around the earth. It is just not really relevant for normal flights. None of the above applies to artillery shells, wind or black balls on blue turntables.
If you want to 'blow your brains' further, the Wiki reference is comprehensive and good, and will tell you that due to the Eötvös effect you can get away with eating more crew food when east-bound than west-bound.
Typo edits
Flex - NB I did include "your motion around an object" but the point I was trying to make was, as JT said, that the Coriolis effect, for controllable objects (unlike Big Bertha - she was wild
) is effectively lost in all the other 'tweaks' we automatically make every second or so. EG did you realise that as you fly around the globe at, say, 450kts you need to keep adjusting your pitch nose down by 0.125 degrees a minute? I guess not. Heading north from the equator there will initially be a similar correction required in roll - all due to our 'motion' being relative to a space frame, but conducted in an earth-frame. All of this, of course, taken care of by our attitude reference systems (be they Mk I eyeballs, gyro Art Horizons, IRS or a black cat sitting on the coaming with its tail hanging over the panel) which are artificially 'tied' to the earth frame and we just do not see it. The ISS and Shuttle do not care much for all of this and generally maintain their 'space' attitude. Now convince me we will 'notice' the Coriolis effect!Incidentally, it is the other gyro 'property' - 'rigidity' - not 'precession' that we are talking about. If I may summarise - Coriolis effect is there. It does affect our motion around the earth. It is just not really relevant for normal flights. None of the above applies to artillery shells, wind or black balls on blue turntables.
If you want to 'blow your brains' further, the Wiki reference is comprehensive and good, and will tell you that due to the Eötvös effect you can get away with eating more crew food when east-bound than west-bound.
Typo edits
Last edited by BOAC; 25th Sep 2009 at 10:52.
Thread Starter
BOAC-thanks.
Had a last minute flight last night...just me and two engineers off to fix a stranded boat. Midnight, quiet night, and conviently flying 3 hours north on the same heading( quite convient actually- and boring). Your post was great and I suddenly clicked to how it all worked as I sat there looking at my instruments and thinking how it all worked with relation to what you had written. My mind can now rest.....
Ive never been one that can settle for the "becasue it just is that way". Thank goodness there are smarter people than that out there that can explain it to those of us who dont get it first time round, or fourtieth for that matter.
Thanks again.
Had a last minute flight last night...just me and two engineers off to fix a stranded boat. Midnight, quiet night, and conviently flying 3 hours north on the same heading( quite convient actually- and boring). Your post was great and I suddenly clicked to how it all worked as I sat there looking at my instruments and thinking how it all worked with relation to what you had written. My mind can now rest.....
Ive never been one that can settle for the "becasue it just is that way". Thank goodness there are smarter people than that out there that can explain it to those of us who dont get it first time round, or fourtieth for that matter.
Thanks again.
Last edited by cwc; 25th Sep 2009 at 21:34. Reason: still tired and made lots of mistakes in grammer and spelling
Thread Starter
I found the airport, that had the helicopter that flew the guys out to the boat. The boat just conviently broke something as it was passing near an a strip.