"Climb via" question

[pstan]

I have been reading the US AIM (Apr 3 2014) on “climb via” SIDs, this starts at para 5-2-8 e 5, page 5-2-9 . There is one paragraph I am having trouble understanding how it is applied, it is para 5 (b) which states:

5……clearance to “climb via” authorizes the pilot to:

para (b) “when vertical navigation is interrupted and an altitude is assigned to maintain which is not contained on the published procedure, to climb from that previously-assigned altitude at pilot’s discretion to the altitude depicted for the next waypoint”

So….if I’m on a "climb via" SID climbing through 6000 feet, proceeding from A (5000 feet) to B (10,000 feet), and ATC now says to “maintain 9000 feet”, then I expect to level off at 9000 feet. However, what is the intention of para 5(b)?


Or is there a better example to illustrate what para 5(b) intends

Thanks

Stan

 

[Gucci Pilot]

It is worded awkwardly. Basically the way I take it is saying, if you are given a "climb via" SID clearance after having been told to maintain 9,000, you can then continue to climb to 10,000(assuming waypoint A is 5,000 and B is 10,000 in your example).

 

[poadeleted20]

If you're cleared to "climb via" this SID, but once airborne the controller says "Maintain 9000", you are correct that you continue your climb via the SID but only to 9000, and then stop there until another altitude instruction is issued. This is shown in Example 7 from that section:

7. (An aircraft was issued the Bbear Two departure, “climb via SID” in the IFR departure clearance. An interim altitude of 16,000 was issued instead of the published top altitude of FL 190). After departure, ATC is able to issue a top altitude of FL300 and still requires compliance with the published SID restrictions. The clearance will be: “Climb via SID except maintain flight level three zero zero.”
NOTE-
In Example 7, the aircraft will track laterally and vertically on the Bbear Two departure and initially climb to 16,000; Once re­issued the “climb via” clearance the interim altitude is canceled and the aircraft will continue climb to FL300 while complying with published restrictions.

As for what paragraph (b) means:

Clearance to “climb via” authorizes the pilot to:
...
(b) When vertical navigation is interrupted and an altitude is assigned to maintain which is not contained on the published procedure, to climb from that previously­assigned altitude at pilot's discretion to the altitude depicted for the next waypoint.

...I'm confused, too. It's hard to understand and appears to contradict both Example 7 and the rest of the guidance on "climb via".

 

[poadeleted20]

It is worded awkwardly. Basically the way I take it is saying, if you are given a "climb via" SID clearance after having been told to maintain 9,000, you can then continue to climb to 10,000(assuming waypoint A is 5,000 and B is 10,000 in your example).

That's correct -- if you were told to "climb via" the SID, then told "maintain 9000", and then again told "climb via SID", you would leave 9000 to make the rest of the altitudes on the SID good, and leaving 9000 would be at pilot's discretion as long as you do so in time to make the next altitude restriction. But once told to "maintain 9000", you'd stay there until you get another altitude instruction.

And if that's the intent of that paragraph, it's really badly worded.

 

[pstan]

Thanks Ron and Gucci.

Gucci, I think your explanation makes sense.

Stan

 

[kayoh190]

If you're cleared to "climb via" this SID, but once airborne the controller says "Maintain 9000", you are correct that you continue your climb via the SID but only to 9000, and then stop there until another altitude instruction is issued.

Minor point here, but what I'm expecting to hear from the controller for your example is "Climb via the xxx departure, except maintain 9000."

If I hear "Climb and maintain 9000", I'm no longer required to comply with any of the altitude restrictions on the SID.

 

[poadeleted20]

Minor point here, but what I'm expecting to hear from the controller for your example is "Climb via the xxx departure, except maintain 9000."

You could get that before takeoff, but even if just cleared to "climb via the XYZ departure" before takeoff, you could still get "maintain 9000" halfway up the SID. In that case, you stop at 9000 until further instructed.

If I hear "Climb and maintain 9000", I'm no longer required to comply with any of the altitude restrictions on the SID.

Yes, if you are told "climb and maintain 9000", that's true. But not if you're told merely "maintain 9000" after being cleared to "climb via" the SID -- in that case, you climb via the SID until reaching 9000 and then stay there until further instructed.

 

[kayoh190]

You could get that before takeoff, but even if just cleared to "climb via the XYZ departure" before takeoff, you could still get "maintain 9000" halfway up the SID.

I would expect (and indeed, it's what happens) to hear this once in the air. That or "Climb and maintain xxx". I don't believe I've ever been instructed by a controller to merely "Maintain xxxx" while climbing via a SID.

 

[poadeleted20]

I would expect (and indeed, it's what happens) to hear this once in the air. That or "Climb and maintain xxx". I don't believe I've ever been instructed by a controller to merely "Maintain xxxx" while climbing via a SID.

Perhaps not, but that's what Example 7 appears to anticipate, and definitely what the OP's question asked about. So if you received that instruction while climbing via a SID, would you not do just as discussed above?

 

[kayoh190]

Perhaps not, but that's what Example 7 appears to anticipate, and definitely what the OP's question asked about. So if you received that instruction while climbing via a SID, would you not do just as discussed above?

I'm not convinced that such an instruction ("Maintain 9000") will ever be given - I don't see that phraseology anywhere. Or perhaps we're simply misunderstanding each other. If I'm in the climb and ATC wants to modify my target altitude but still have me honor the restrictions, I expect to hear "Climb via the SID, except maintain xxxx." If I hear only "Maintain xxxx", I'd get some clarification. Example 7 shows how I'd expect it to happen.

That said, I understand what the OP is saying. That paragraph could be worded better, but Gucci's interpretation is how I see it.

 

[poadeleted20]

I believe you are correct as to how a controller is supposed to say it according to FAA Order 7110.65:

b.​

When route or altitude in a previously issued​

clearance is amended, restate all applicable altitude​

restrictions.
...

2. ​

(An aircraft is cleared to climb via a SID with published​

altitude restrictions. Shortly after departure the top​

altitude is changed to FL 230 and compliance with the​

altitude restrictions is still required, the controller issues​

an amended clearance as follows):

“Climb via SID except maintain Flight Level Two Three​

Zero.”​

NOTE​

−​

1.​

Restating previously issued altitude to “maintain” is an​

amended clearance. If altitude to “maintain” is changed or​

restated, whether prior to departure or while airborne and​

previously issued altitude restrictions are omitted, altitude​

restrictions are canceled, including SID/STAR altitude​

restrictions if any.

So, the controller should either say "Climb and maintain 9000" (in which case the "climb via" restrictions are cancelled and you climb normally straight to 9000), or "Climb via SID except maintain 9000" (in which case the SID restricted altitudes still apply on your way to 9000). And if they just say "maintain 9000", you would be correct to obtain clarification as to whether you should climb straight up or climb via the SID.

 

[Kritchlow]

While most situations are self explanatory, I have run into a few that can get very tricky. I just ask.

 

[Henning]

That's correct -- if you were told to "climb via" the SID, then told "maintain 9000", and then again told "climb via SID", you would leave 9000 to make the rest of the altitudes on the SID good, and leaving 9000 would be at pilot's discretion as long as you do so in time to make the next altitude restriction. But once told to "maintain 9000", you'd stay there until you get another altitude instruction.

And if that's the intent of that paragraph, it's really badly worded.

Really really poorly worded. I agree that's what they meant to say, they just left it out.

 

[Henning]

Minor point here, but what I'm expecting to hear from the controller for your example is "Climb via the xxx departure, except maintain 9000."

If I hear "Climb and maintain 9000", I'm no longer required to comply with any of the altitude restrictions on the SID.

The only way I see this happening is you get cleared on a SID, switch to departure they give you "maintain 9000" for Traffic needs then comes back with "Climb via xxx" to put you back on your own V nav to the SID.

 

[poadeleted20]

The only way I see this happening is you get cleared on a SID, switch to departure they give you "maintain 9000" for Traffic needs then comes back with "Climb via xxx" to put you back on your own V nav to the SID.

Except if they want to do that, 7110.65 gives them different, less ambiguous, phraseology to use. Just saying "maintain 9000" isn't in their book. So, I'm convinced by kayoh190's post that the proper response to a simple "maintain X thousand" while on a "climb via SID" clearance should be a request for clarification as to whether you should climb straight to that altitude or climb via the SID to that altitude.

 

[kickbackkid]

As controllers, there are only two ways to state this:

"climb via SID, except maintain XXX altitude". The pilot must comply with all published restrictions, with a new top altitude.

Or:

"climb and maintain XXX" The pilot will climb at their discretion to the altitude issued.

Anything else is incorrect, and should be questioned.