Time of crossing/passing calculations
Time of crossing/passing calculations
Join Date: Nov 2000
Location: Scandiland
Posts: 480
Likes: 0
Received 0 Likes
on
0 Posts
I'm really crap at mental math, so I allways bring a small calculator incase I get a block preventing me from thinking!
Otherwise it's, distance/time = speed.
If you follow the track drawn on the map ( I allways draw out tracklines and write down all little details I might need, heading and TT, on the map)and note the time between landmarks, you can use the distance on the map as a time reference. For example, if it takes five min between a lake and a mountain marked on the chart, just measure the distance between your fingers and "walk" along the chart. Then you have to take into account the W/V. When it comes to that I just guess! Usually works... Then you might need more accurate ways to calculate this, but it works fine for VFR-daytrip-use.
But allways make a flight plan and work out everything that you can work out on the ground before T/O. Being accurate then is no problem, because you've got ample space to measure distances and use calculators of different types. Allways make sure you've got enough time for planning before you get airborne. Making a complete flight plan and checking stuff out, may take as much as five hrs. Depends though where you're going...
regards/lns
(appologies for grammar and spelling mistakes...
)
[ 31 July 2001: Message edited by: low n' slow ]
[ 31 July 2001: Message edited by: low n' slow ]
Otherwise it's, distance/time = speed.
If you follow the track drawn on the map ( I allways draw out tracklines and write down all little details I might need, heading and TT, on the map)and note the time between landmarks, you can use the distance on the map as a time reference. For example, if it takes five min between a lake and a mountain marked on the chart, just measure the distance between your fingers and "walk" along the chart. Then you have to take into account the W/V. When it comes to that I just guess! Usually works... Then you might need more accurate ways to calculate this, but it works fine for VFR-daytrip-use.
But allways make a flight plan and work out everything that you can work out on the ground before T/O. Being accurate then is no problem, because you've got ample space to measure distances and use calculators of different types. Allways make sure you've got enough time for planning before you get airborne. Making a complete flight plan and checking stuff out, may take as much as five hrs. Depends though where you're going...
regards/lns
(appologies for grammar and spelling mistakes...
)[ 31 July 2001: Message edited by: low n' slow ]
[ 31 July 2001: Message edited by: low n' slow ]
Guest
Posts: n/a
This method works OK if you are on reciprocal tracks.
Aircraft A reports XXX at 0330 ETA YYY 0415
He then hears Aircraft B reporting YYY at 0340 ETA XXX 0430 (Slower and going the other way).
To work out crossing time you must convert all times to a common base, add them together and then divide by 4.
For the above example 30 + 75 + 40 + 90 = 235
235/4 = ~59 so time of passing will be at 0359.
If the times are over a 2 hour frame you will have to add 120 mins to the latest time ie 0505 would be 125.
Don't ask me about the math behind it!! I don't know.
Aircraft A reports XXX at 0330 ETA YYY 0415
He then hears Aircraft B reporting YYY at 0340 ETA XXX 0430 (Slower and going the other way).
To work out crossing time you must convert all times to a common base, add them together and then divide by 4.
For the above example 30 + 75 + 40 + 90 = 235
235/4 = ~59 so time of passing will be at 0359.
If the times are over a 2 hour frame you will have to add 120 mins to the latest time ie 0505 would be 125.
Don't ask me about the math behind it!! I don't know.
