RNAV SID Divergence

[Krag]

My question has to do with 5-8-3. Is the 10 degrees for RNAV SID departures still allowed even if the controller has to issue a heading initially? If so, what makes the initial controller assigned heading for this so special compared to every non RNAV SID that requires 15 degrees?

The reference simply says:

5-8-3 c. When both aircraft are flying an RNAV SID: 1. Between successive departures from the same runway– 1 mile if courses diverge by 10 degrees or more immediately after departure. (See FIG 5−8−1.)

 

[eltors0]

The reference litterally answers your initial question. As far as why you need 15 degrees over the 10, I have no idea and it seems rather trivial after seeing how bad some of the crews goof up the climb via but it’s just the standard we have to apply.

 

[Dues For Booze]

RNAV course is the airplane's computer flying/displaying the predetermined course over the ground within a tolerance limit (1.0NM 95% of the time for RNAV 1 SIDs). A heading can vary due to the tolerance limits of the compass, or a gust of wind, or a pilot not paying attention, or anyone of the several instrument variations of deviations.

Take a look at the wider dispersal of headings versus RNAV tracks in ATL.