dme arc approaches

[Max Steel]

Anyone know the formula for working the above out.

Regards

Max :eek: :cool: :D

[Rotorbike]

Ninety degrees to the radial you are crossing and turn 10 degrees every 10 degrees.

Does that make any sense???

:) :) :)

[doggonetired]

Can anybody remind me of the formulas for radius of turn at differing speeds and rates and distance travelled?
Many thanks in advance.

[Tinstaafl]

Rule of thumb: TAS/200 = lead distance to commence the turn to join the arc.

If joining from an outbound track you'll need to turn 90 deg + a bit more - say 100 deg.

If joining from an inbound track you'll need to turn 90 - a bit eg 80 deg.

Fly the arc in a series of short segments and not as a continuous turn.

Once in the arc a comparison of rate of closure vs DME dist can help you decide if you need to turn a bit more or a bit less to remain inside arc tolerance. Min rate of closure occurs at the point of closest approach.

Rule of thumb to find the lead radial/bearing to commence the turn to intercept the final (or any track for that matter):

Using the lead distance found earlier, on whiz wheel

Lead Distance = lead angle
------------- = ---------
DME arc dist. = 60

Another way to express this is to divide 60 by the DME arc dist then multiply by the Lead Distance eg a 12 DME arc, lead dist .6 nm.

60/12 = 5. 5 x .6 = 3.6 deg --> round up to 5 deg lead angle

[Warlock2000]

I find the best way is to let the autopilot do it!

[Dan Winterland]

Try remembering the formulae while flying a tricky procedure in real IMC and turbulence, you will probably find you can't. So try what I used to teach, the TLAR (That Looks About Right) method.

To approach the arc, just ease on if entry angle is less than 45 degrees. If more, give it about 2 DME anticipation at about 120 Knts. To maintain, point the VOR/ADF needle at the wingtip (imagination required for swept wing aircraft) and change heading towards the facility a few degrees every 15 - 20 secs.

To adjust - if you need to cut into the arc, point the needle just ahead of the wingtip until the DME is correct. To widen, needle behind the wingtip.

KISS.

[wysiwyg]

Agree with Warlock, draw a pretty picture using the FMC and engage LNAV.

[mustafagander]

If you lead your turn by 1% of G/S you will stay within your +/- 2nm tolerance. Allow a bit for wind if it's strong. Don't get too academic, K.I.S.S. Tracking inbound to the aid underturn a few degrees, outbound overturn a few. :)