Clearance Conflict on a Night Departure from Tehran
You are captain of a night IFR flight from Tehran Mehrabad (OIII) to Tabriz (OITT) in a twin-jet. The OIII ATIS gives runway 29 in use, wind 290/08, visibility 10 km, QNH 1010. The published SID for runway 29 requires a climb on 292° to 5,000 ft before turning right to intercept the 310° radial. Shortly after take-off, ATC clears: 'ABC123, climb FL200, direct PAX.' PAX is 40° right of the current heading and only 12 nm ahead. The aircraft is at 3,200 ft, climbing 2,200 ft/min. MSA in the area is 9,700 ft. The first officer reads back the clearance and begins a right turn. You have terrain displayed on the ND. Fuel is normal and destination weather is VMC.
1. What should you do immediately when the first officer begins the turn, and what is your responsibility as pilot-in-command?
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Immediately call STOP TURN or take control and maintain the 292° heading. The clearance is not automatically unsafe, but at 3,200 ft with MSA 9,700 ft and PAX only 12 nm ahead at 40° right, a direct turn reduces the horizontal distance available to climb and may cut inside the protected SID area. The PIC remains responsible for terrain clearance even when ATC issues a clearance. The correct response is to tell ATC UNABLE DIRECT PAX AT THIS TIME and request to maintain the SID until 5,000 ft or until a safe direct routing is confirmed. Do not let the first officer continue the turn while you resolve the clearance; use positive exchange of controls if necessary.
2. Which items in the clearance require a full readback, and what should the readback have included?
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Requires full readback: route clearance, altitude, heading, speed, frequency, SSR code, and any hold-short or take-off/landing clearance. The first officer's readback of climb FL200, direct PAX was technically correct but incomplete in context: it omitted the constraint that the aircraft was still below the SID turn altitude and did not state that the crew was maintaining the SID. A safer readback would be: Climbing FL200, maintaining runway heading to 5,000 ft, unable direct PAX, request amended clearance. The readback must be unambiguous and must not imply acceptance of a clearance the crew cannot safely execute.
3. Draft the ATC request you would make and the follow-up if ATC insists on the direct routing.
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Request: ABC123, request maintain 292° to 5,000 ft, then direct PAX, due terrain and MSA. If ATC insists on direct PAX, state UNABLE DIRECT PAX DUE TERRAIN, request alternate routing or maintain SID. If the controller cannot amend, declare UNABLE and continue the SID; the PIC has final authority for terrain clearance. Later, file an occurrence report if the clearance created a genuine safety risk and debrief the first officer on challenging ambiguous clearances.