Climb Via SID Except Maintain, Then a Crossing Restriction You Cannot Make
You are departing IFR at night in a single-pilot twin turboprop from a Class C airport. Clearance is: 'ABC123, cleared to Delta via the RIVET2 departure, climb via the SID except maintain 5,000, squawk 4271.' The RIVET2 chart requires 6,000 ft at RIVET (12 DME) and 210 kt below 7,000 ft. You read back the clearance in full. In IMC at 8 DME ATC asks your altitude; you are level at 5,000 ft. ATC then says: 'ABC123, climb and maintain 7,000, expedite, traffic 12 o'clock, 4 miles, opposite direction at 6,500.' You climb at 1,200 fpm and pass the traffic at 6,700 ft. Later, level at FL 190, ATC clears you: 'ABC123, descend via the ARRIVAL, expect 250 kt at the 30 DME fix.' You are running the arrival 2,000 ft above the nominal profile and 15 kt fast, at ISA+18, and the aircraft has no speedbrakes.
1. Was levelling at 5,000 ft correct, and what should you have done about the 6,000 ft requirement at RIVET?
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Interpret the clearance. 'Climb via SID' obliges you to follow the published track and to comply with the published altitude and speed constraints on the SID. 'Except maintain 5,000' is an explicit level-off instruction that caps the climb. The two only reconcile in one way: the 6,000 ft at RIVET constraint lies above your cleared level and is therefore not applicable until you receive further clearance; constraints below 5,000 ft remain binding.
So levelling at 5,000 ft was correct. Climbing to 6,000 ft to satisfy the chart would have been a level bust and, with opposite-direction traffic in the area, a genuine collision risk. The full readback was your protection: it puts the clearance on the record.
What you should have done better. Ten seconds on the delivery frequency: 'Confirm maintaining 5,000 until further advised, RIVET restriction not applicable?' Where the chart and the clearance appear to conflict, the conflict is usually in the pilot's interpretation, not in the clearance - and if the SID's minimum safe altitude in that sector were above 5,000 ft, the correct response would have been 'unable'.
Generalisable rule: the last explicit altitude instruction overrides the vertical profile; published constraints below the cleared level still apply; ambiguity is resolved on the ground, not at 8 DME in IMC.
2. Traffic opposite direction at 6,500 ft while you are cleared to 7,000 ft and told to expedite. What are your considerations and what do you say?
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Comply, then manage the risk. The clearance is to climb and maintain 7,000 ft; 'expedite' asks for the best rate consistent with the aircraft's limitations, not for a rate beyond them. You are climbing through the other aircraft's level, so the exposure is real even though ATC owes you separation in Class C.
Threats to manage. Single pilot, night, IMC - workload is at its peak. Prioritise: fly the aircraft, use the autopilot if it reduces load, select external lights, keep the TCAS display in view. An opposite-direction aircraft at 6,500 ft should pass down your left side; if the traffic appears on the wrong side or the TCAS shows a TA, that is information, not a nuisance.
Phraseology. If 1,200 fpm is the best you have, nothing needs saying. If you cannot achieve a reasonable rate - engine limit, icing, weight - say so early: 'ABC123, unable to expedite, climbing 700 feet per minute.' Early is the operative word; a report after the traffic has passed is useless. If separation looks inadequate, say so: 'ABC123, we passed close, estimate 300 feet, request traffic details' - that protects the next aircraft as well.
If a TCAS RA occurs: respond immediately, even against the clearance, call 'TCAS RA', then 'clear of conflict' when returning.
3. Descend via the arrival, expect 250 kt at 30 DME, and you are high and fast. Can you comply, and what do you transmit?
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What the clearance obliges. 'Descend via the ARRIVAL' clears you to descend on the arrival's lateral path and to meet all published altitude and speed restrictions. 'Expect 250 kt at 30 DME' is an expectation, not yet a restriction - but you should plan as if it will become one, because it usually does.
Can you do it? Run the numbers before you answer. You are 2,000 ft above profile and 15 kt fast, ISA+18 (reduced descent performance), no speedbrakes. The required descent gradient exceeds what an idle descent can deliver, and the speed will not decay to 250 kt by 30 DME without help. So the honest answer is: not as currently positioned.
What to transmit - early. 'ABC123, unable 250 knots at 30 DME from present position, request 280 knots or vectors for a wider descent.' Alternatives to offer: a later speed restriction, a vector to lengthen the track, a hold, or a lower speed at a later fix. ATC has other traffic behind you; the earlier they know, the cheaper the fix.
What not to do. Say nothing and hope; take a shortcut off the arrival to make the profile (that breaks the 'descend via' lateral path); or arrive fast and high and then dump the aircraft onto the runway. A level bust or a speed violation here is a separation problem for the aircraft behind, not just your own unstable approach. Report the event through the SMS if the restriction was actually missed.