The cool air from the Pacific Ocean lifts us gently from the runway leaving the busy city of Las Angeles behind. The deep blue water below is inviting. As we bank left back towards the white sand of Manhattan Beach and the rolling hills and palatial homes atop the Palos Verdes Peninsula all I can say is "nice".
The sunset illumination of Santa Monica Bay and the flight deck was calming, until the controller interrupted our relaxed state with an instruction to "climb to thirteen thousand comply with all restrictions". Now we needed to start looking at the charts again and ignore the grand spectacle outside our window.
Before departing runway 24 Left (24L) at Los Angeles International Airport (KLAX), we where issued a clearance from air traffic control (ATC) which included "Climb via the LOOP7 maintain 5000". The first altitude restriction on the LOOP7 is to cross the Santa Monica VOR 160 radial "at and below 3000" and "at or above 302 feet".
Referencing the chart, we see the next altitude restriction is to cross LAX VOR at or above 10,000 feet. Since our clearance was to climb via the LOOP7 maintain 5000 we do not have to comply with the 10,000 foot restriction, at least not now.
After a few miles we where issued a clearance to turn left to heading 250 maintain 5,000. Only few minutes later we where give another clearance to "turn left direct to LAX VOR; climb to thirteen thousand; comply with all restrictions".
With our new clearance we looked at our chart and saw that we must cross LAX VOR at or above 10,000 and then KEGGS at or above 13,000.
All is going well until we get our next clearance. As we are heading towards LAX VOR and climbing through 7,000 feet we are given the clearance to "maintain flight level 190 (FL190)". I then look at my co worker and say "that is odd". "I bet that he meant for us to comply with the restrictions. The Captain shook his head and said "I think that is what he meant".
There was confusion in our minds as to the clearance issued so we asked for clarification. The controller reissued his clearance to "Climb to FL190 and comply with all restrictions". Since we needed a maximum performance to meet the restrictions it was important to know if we needed to comply with the restrictions on the departure.
Climb VIA Clearance
Before we discuss amendments to altitudes, let us first review the climb via clearance. CLIMB VIA is an abbreviated ATC clearance that requires compliance with the procedure lateral path, associated speed restrictions, and altitude restrictions along the cleared route or procedure.
When issued a "climb via" clearance you will see a top altitude to maintain on the SID or if an altitude is not given you will receive an altitude to "maintain" in your initial clearance. For example, before departure received a clearance to "climb via the LOOP7 maintain 5,000". Therefore we must comply with all speed and altitude restrictions up to our cleared altitude of 5,000 feet.
Speed Restrictions on a Climb VIA Clearance
I know we are only discussing altitude changes during a climb via clearance but it is good idea to review speed restrictions. Similar to the Descend Via Clearance you will need to comply with all airspeed and altitude restrictions unless given an amended clearance. For further information please read What is a "Descend Via" Clearance? and What To Do When Given A Descent Clearance On A STAR.
Climb Via with an Altitude Amendment
Aircraft instructed to resume a procedure which contains restrictions (SID/STAR/FMSP, etc.) must be issued/reissued all applicable restrictions or must be advised to comply with those restrictions. This is why the air traffic controller told us to comply with all restrictions when he amended the altitude to 13,000.
Also, when a route or altitude in a previously issued clearance is amended, the controller will restate all applicable altitude restrictions. During our flight we where vectored off the SID requiring the controller to issue the clearance to "maintain 5000".
It is important for you to understand during a climb VIA clearance:
- Restating previously issued altitude to “maintain” is an amended clearance.
- Altitude restrictions are canceled if the altitude to “maintain” is changed or restated and previously issued altitude restrictions are omitted. This applies whether prior to departure or while airborne. This includes SID/STAR altitude restrictions if any.
- Crossing altitudes and speed restrictions on Obstacle Departure Procedures (ODPs) are mandatory and cannot be canceled by ATC.
Since we are pilots and don't normally carry around air traffic control policy let us look to one of the best references for pilots the Aeronautical Information Manual (AIM). "The guiding principle is that the last ATC clearance has precedence over the previous ATC clearance. When the route or altitude in a previously issued clearance is amended, the controller will restate applicable altitude restrictions. If altitude to maintain is changed or restated, whether prior to departure or while airborne, and previously issued altitude restrictions are omitted, those altitude restrictions are canceled, including departure procedures and STAR altitude restrictions."
The Climb Via clearance increases airspace efficiency because of they are preplanned routes, altitudes, and speeds. With efficiency comes a greater risk of mistakes when there is an amendment to the pre planed clearance.
When issued an altitude amendment during a climb via clearance you should expect to hear the controller issue a "climb via except maintain", "comply with all restriction", or a restatement of all the restrictions. If you are given a altitude amendment of "climb and maintain" you no longer must comply with the altitude restorations on the SID, but must comply with the speed restrictions.
If you are confused by a clearance or feel the controller may have made a mistake ask for clarification. You should never feel bad about asking for clarification when you don't understand a clearance since it should only take a few seconds an will enhance the safety of your flight.
Climb VIA Frequently Asked Questions (PDF file)