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Bates106
24th Jul 2009, 13:13
I have heard many different names and different ways of calculating it, post your name and your way of calculating it: when your track is 090 degrees and there is a wind at 11 knots from the North, and your flying at a speed of 100mph, what is your heading with the wind and still gonna end up at the destination!

Keygrip
24th Jul 2009, 14:44
083°, mentally

A Very Civil Pilot
24th Jul 2009, 17:57
A bit to the left.

24Carrot
24th Jul 2009, 22:06
TAS sin(wca) = WS sin(wd-trk)

TAS = True Air Speed
wca = Wind Correction Angle
WS = Wind Speed
wd = Wind direction
trk = Track
so 6.315 degrees or so to the left because
100 sin(-6.315) = 11 sin(0-90)

But in real life, I do MaxDrift times the clocked angle rounded to the nearest 5 degrees because the wind forecast is never right anyway.

PS just a PPL, not an FI, sorry. :(

what next
25th Jul 2009, 10:53
Hello!

But in real life, I do MaxDrift times the clocked angle rounded to the nearest 5 degrees because the wind forecast is never right anyway.

PS just a PPL, not an FI, sorry.

But in real life, I steer so that the "track" figure euqals the "desired track" figure on my GPS readout. And if ever one of my students pulls out an E6B (or whatever) flight computer and starts fiddling with this thing in flight instead of looking outside, I will take it away from him and throw it out of the window. Promised!

Greetings, Max

PS: Just a FI, not a PPL ;)

Tinstaafl
26th Jul 2009, 00:36
Try chucking my Jepp. CR computer out while I'm using it in flight and I'll make sure you follow it to retrieve it.

212man
26th Jul 2009, 02:43
100mph is about 90 kts (just under) so maximum drift with 11 kts of wind will be 11 *60/90 which is 22/3 or 7.33 degrees. So, with a Northerly wind and a track of 090, you will experience 'max drift' so need to head 082-083 (like what Keygrip said :ok:)

24Carrot
29th Jul 2009, 11:58
I mis-read the 100mph as 100kts, so the theory says
86.9 sin ( -7.27) = 11 sin (0-90), ie 7.27 degrees left.

Obviously Max Drift is just as good in practice, and much
easier to calculate in flight, not least if both E6B and FI
just exited stage right...

Duchess_Driver
29th Jul 2009, 12:53
Don't throw it out the window....

...on the back seat is safest! :ok:

2close
29th Jul 2009, 22:17
At that speed:

Max Drift = 6 degrees of into wind correction per 10 knots of windspeed
Then for every 20 degrees off heading, subtract 1/4 of the correction, i.e. up to 20 degrees off the nose / tail = 1/4, 20 - 40 degrees = 1/2, 40 - 60 = 3/4, 60 + = ALL

For speed:
For every 20 degrees off heading or reciprocal, add or subtract 1/4 of the wind speed,
i.e. up to 20 degrees off the nose / tail = ALL, 20 - 40 degrees = 3/4, 40 - 60 = 1/2, 60 + = 1/4

(Some use 0-15, 15-30, 30-45, etc. but I find that the 20's work just as well with minimal difference and are easier for people to cope with the mental gymnastics)

In the above situation, I'd have corrected 7 degrees into wind and flown 83 degrees True with 2 - 3 knots on the TAS to give GS ~ 90 knots - a very convenient 1.5 NM per minute.

These are only rules of thumb but are very quick to do in your head on the fly and accurate enough for practical flying - a 2 degree correction error translates into only a 2 NM off-track error over 60 NM and can be easily monitored in flight.

During the CPL my instructor insisted on all pre-flight and in-flight calculations being done on Max Drift with no use of CRP. It certainly helped me and has helped my students since.

chrisbl
31st Jul 2009, 18:40
Three kinds of drift, 5,10 and 15 degrees.

Tinstaafl
1st Aug 2009, 00:25
In Shetland it was more like 15, 30 or 45. :p

SASless
1st Aug 2009, 23:42
Fly the measured track.... for the estimated time of enroute to your destination....turn into wind...guess/figure the distance you would be off course and Bob's yer Uncle! The only trick was having enough Vis to be able to see your Rig, Platform, or Well Head within the circle of error caused by the wanderings of your heading/airspeed control, deviation in the Compass, and misjudgement of wind speed and angle. At least when you got out into the field you knew which way to turn to find what you were looking for. Otherwise you fetched up in the middle of no where looking at an empty ocean wondering where the rig had run off to and no idea which way to go to find it.

Learned in the old, old, old, days of mag compass, clock/watch/airspeed only for finding yer way around the oggin.

Ah yes.....ILS approaches looking out the side window for the runway!