Sid star confusion

[Henry Wallace]

Hi,

Just wondering why on this example there are two waypoints, both FL270 or above and in between it says FL200?

Thanks

[Kirk Christie]

The altitude between the fixes are the lowest safe altitude for that section.

The altitude at the fix is a requirement of the STAR to cross that fix at or above 270.

If you are told to descend via the STAR you would plan to cross ABASN at or above 270. If the controller canceled the level requirements of the STAR you could descend below 270 ABASN but not below the 200 on that section.

 

[Mike Sweeney]

As above, pilots refer to the altitudes/flight level on a STAR with a line above, below, or both.
For 'descend via' clearance, cross ABASN at/abv FL270
Other altitudes (the min route altitudes on a segment of the SSKII arrival) are not relevant for a 'descend via' clearance,
 

.... as a side note for US airspace, questions have been raised by rw pilots and re-visited by the FAA.
The criteria for determining an MEA on an en-route chart may not be the same as a minimum route altitude for a segment published on a STAR.
- MEA (Minimum Enroute IFR Altitude) 'lowest published altitude between radio fixes that ensures acceptable navigational signal coverage and meets obstacle clearance requirements between those fixes'.
- On a STAR (or SID), minimum route altitudes for a segment may have been "artificially raised to support ATC separation needs/traffic management".
(pilot may reference in the event of an aircraft emergency + radio failure/ lost comms ... additional in two links above.)

In case useful ...
- Aeronautical Chart User's Guide (pages 119, 123)
- Aeronautical Information Manual (check 5-4-1, Standard Terminal Arrival (STAR) Procedures; "descend via" examples)

Edited April 28, 2020 at 07:19 AM by Mike Sweeney