Vectored off a descend-via arrival, then an unachievable crossing restriction
You are single-pilot in a TBM 930 cruising at FL280 on an IFR flight. ATC issues: 'Descend via the HAWKZ TWO arrival, expect the ILS runway 16L.' The arrival publishes restrictions: cross HAWKZ at or below FL240, cross JOZEP at 12,000 and 250 kt, and cross RADDY at 8,000. You are 8 NM west of HAWKZ at FL280 when ATC says: 'Turn right heading 360, vectors for spacing, maintain 8,000.' At the turn you are level at FL270, about 7 NM from JOZEP, and you begin descending. Two minutes later, while still off the arrival path, ATC says: 'Cross JOZEP at 12,000 and 250 knots.' You are then 6 NM from JOZEP at 19,000 ft, indicating 300 KIAS, with a 40-kt tailwind. The minimum vectoring altitude is 7,000 ft. You have not been given a route back to the arrival.
1. What happens to the descend-via clearance when you are vectored off the arrival, and what altitudes and speeds must you fly now?
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The descend-via clearance is tied to the lateral path of the arrival. When ATC vectors you off that path, the clearance is canceled and you fly the last assigned altitude, which here is 8,000 ft; the published restrictions at HAWKZ, JOZEP, and RADDY no longer apply, and neither do the charted speed restrictions unless ATC restates them. You may descend to 8,000 ft but not below it, and you should not assume the arrival's bottom altitude of 6,000 ft is authorized; it is not. The 250-kt speed restriction is also canceled, but the regulatory speed limit below 10,000 ft still applies, and you should be slowing anyway because you are approaching the terminal area. 'Expect the ILS runway 16L' is information, not a clearance, so it does not change any of this. Practically, expect ATC to keep issuing altitudes on vectors and to re-clear you onto the arrival or to an intercept later, and do not let the moving map tempt you into resuming the arrival's descent profile before you are cleared back onto it.
2. Evaluate the crossing restriction: cross JOZEP at 12,000 and 250 kt from 6 NM out at 19,000 ft and 300 KIAS. What do you say to ATC?
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The restriction requires losing 7,000 ft in 6 NM, which is over 1,100 ft per NM, and the machine is also 50 kt too fast at the moment the restriction is issued. With a 40-kt tailwind, ground speed is roughly 400 kt, so 6 NM is less than one minute of flight; even ignoring the speed reduction, that would demand a descent rate in the thousands of feet per minute. It is not achievable, and the speed reduction alone takes longer than the distance available. The right response is immediate and specific: 'Unable the crossing restriction at JOZEP from our present position, request cross JOZEP at 15,000' or ask for a vector or a turn to lose altitude. Saying 'unable' is not a refusal to comply; it gives the controller time to build a new plan. The wrong response is to accept, dive at the barber pole, and then miss the restriction, which strips away both altitude and speed margins and puts the controller's spacing plan at risk without warning.
3. Which parts of these clearances must be read back, and what do you do if you are unsure whether 'maintain 8,000' still applies after the crossing restriction?
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Read back every altitude assignment, the heading, any speed assignment, and the crossing restriction, using the fix, altitude, and speed in the correct order. Altitude readbacks are mandatory, and the descend-via clearance itself should be read back in full because it contains multiple restrictions. When ATC issues a crossing restriction that modifies an earlier assigned altitude, the two are compatible only if you level at the crossing altitude and later continue, so there is genuine room for confusion. Never guess. If you are unsure whether 8,000 ft is still the assigned altitude after the cross-JOZEP instruction, ask: 'Confirm maintain 8,000 after JOZEP.' Similarly, confirm whether the 250-kt restriction is a speed to cross the fix with or a speed to maintain, and confirm when and where you will be re-joined to the arrival. A brief query costs a few seconds; an incorrect assumption about an assigned altitude in terminal airspace is a much more expensive mistake.