Thanks BEagle, you've been really helpful.
He has detailed the SCA method here GuinnessQueen:
http://www.pprune.org/forums/showthr...hreadid=154455
Also, for convenience, I'll quote:
I use a version of the 1 in 60 termed the Standard Closing Angle method:
If you realise that you are a miles off track and wish to fly b miles back on to track, then you need to turn through an angle ö whose sine is equal to a/b. Now the 1 in 60 rule tells us that ö is more or less equal to (a/b)x60 and if you fly your distance b at v miles per minute for t minutes, then ö = (60/v)x(a/t). If a and t are made numerically the same, that is you fly for the same number of minutes as your number of miles off track, then a = t and a Standard Closing Angle ö of (60/v) can be used where v is expressed in miles per minute. Hence the SCA at 360 kts is 10°, at 120 kts it is 30° and at 90 kts the SCA is 40°.
With a SCA of 40 deg, along track velocity v cos ö is 0.766 v or roughly 3/4 of the original velocity; hence what would have taken 3 minutes now takes 4. The ETA should therefore be delayed by 1/3 of the time spent flying at the SCA.
It's so easy that many dyed-in-the-wool FIs won't trust it!
How far off track? 3 miles
Turn towards by 40 deg.
Fly for 3 minutes towards track and note that ETA at the end of the leg will be + 1 minute
Return to original heading, re-check DI synchronisation and slip ball.
What does HAAT stand for? Searched the forum/google.. doesn't come up.
