Cross At/Maintain Instruction

[Mark Hargrove]

Purely out of curiousity, does the directive

"Cross XXX at, maintain 6000"

also imply "proceed direct XXX" ?

Asked in a slightly different way (and to use a concrete example): say we've just departed SNA on an assigned heading of 270 degrees and an assigned altitude of 5000' (I'm just making this up; roll with it if that particular assignment would never happen from that particular airport).

ATC says "Cross Seal Beach VOR at, maintain 6000'"

Does this instruction imply 'proceed direct Seal Beach" as well as the altitude assignment and restriction? -- or would there be phraseology that got us turned toward SLI first, followed by the crossing restriction?

This question has nothing to do with any real- or simulated-world situation -- I'm just curious.

-M.

[Keith Smith]

the instruction is "Cross [fix] at and maintain [altitude]."

That aside, a crossing instruction does not have any bearing on any lateral navigation, it's purely vertical.

The instruction will ONLY be issued if your route of flight will already take you over said fix, and receiving the instruction doesn't change the priority with which you go to the fix.

[kullery]

The other day I heard this instruction issued to another aircraft and it didn't sound right to me.

"Cross APLES at and maintain 9000, cleared VOR/DME rwy 17 approach".

APLES is the IAF for that approach and the approach calls for 6600 between APLES and BYTHE. To me, it sounded like the clearance was giving conflicting altitude instructions and I think that I would have requested clarification if I had received it. I would have been left wondering if I was REALLY authorized to follow the decent information specified for the approach.

Is there some nuance to "at and maintain" that I am missing in this situation?

ken

[Peter Grey]

The "and maintain" should not have been part of that instruction. In that case clarification should be obtained for the reasons you state.

[Keith Smith]

Additionally, if the aircraft was on an airway leading to APLES, then no altitude need have been given at all.

[Ryan Geckler]

The MEA for most of the airways to APLES is 9000. Our minimum vectoring altitude is 8000. I'd issue the approach as "cross APLES at or above 9000, cleared VOR/DME rwy 17 approach". Alternatively, we can give direct APLES, which relieves you of the MEA on the airway, but we can only go down to 8000 at that point.

Keith/Peter, correct me if I'm wrong, but isn't the 6600 the lowest you can go on that segment of the approach? If you are given 9k until APLES, you can descend to 6600 once you reach it, correct?

[Keith Smith]

Correct, you can descend to the altitude for the initial segment after the IAF. However, if an aircraft is on an airway or feeder route, there is no operational need to give a crossing altitude at APLES. Only if an aircraft is operating off-airway does an altitude need to be given in the approach clearance.

[Mark Hargrove]

That was probably me being issued that instruction while flying the I-11. I was momentarily confused as well with the cross at/maintain 9000 instruction, but since the controllers last words were 'cleared for the VOR/DME 17 approach" I decided that instruction took priority. Once I reached APLES I descended to 6600 along the first part of the arc, and was comfortably at that altitude before reaching BYTHE.

Several small but odd things happened during that particular flight, starting with a plane (a drone?) landing at Corona Muni while I was waiting to take off. It appeared on my TCAS very near the airport and directly behind me, like it just appeared magically in the pattern. I'd already announced my taxi on the CTAF frequency and was just braking at the runway entrance for final setup and a last look around when the plane appeared on the TCAS. Since it was likely a drone, there were no radio announcements on the CTAF freq. The flight path on the TCAS sure looked like a pattern, so I just sat and waited with my nose angled a bit towards final so I could see it. Sure enough, a Piper landed a few minutes later on Rwy 25. I was getting a bit nervous because it was getting close to my void time for the clearance -- but I was airborne with a couple of minutes to spare.