The Slot Delay That Eats the Reserve
Two pilots plan a private VFR flight in a PA-28-181 from an inland aerodrome to the coast, planned trip time 1 h 20 min at a planning burn of 34 L/h. The flight-plan figures are: taxi 6 L, trip 45 L, contingency 7 L, alternate 12 L, final reserve 30 min (17 L) - a total of 87 L. Usable tank capacity is 190 L, and the aircraft is dipped at 92 L. Before start, delivery advises a 40-minute flow slot on the ground. The right-seat pilot's Class 2 medical lapsed nine days ago; the left-seat pilot's is valid and current. The forecast is VFR throughout and the figures already include the 15 kt headwind at cruise level. Neither pilot holds an instrument rating.
1. Is the fuel state acceptable for departure once the slot delay is included, and how would you handle it?
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Arithmetic first. Planned requirement 87 L against 92 L on board leaves a surplus of only 5 L - about 9 minutes at cruise burn.
The slot is not free. Forty minutes of ground running (start, taxi, holding at the holding point, engine idling in the queue) at roughly 4–6 L/h consumes 3–4 L. That leaves 1–2 L of unplanned margin, i.e. effectively none.
The 5 L surplus is not a reserve - it sits on top of a plan that already assumes the forecast wind is correct, no re-route, no extra circuit, and a first-approach landing. Any one of those erodes the final reserve, which is the one figure that must remain intact at the destination.
Judgement. The flight is inside the planned numbers but outside sensible airmanship. Either refuel to restore a genuine margin (30–45 min above the planned total, roughly 20–25 L) or recalculate with the actual taxi burn and re-clear the slot. Departing on a 2 L cushion and then being surprised by a hold is how fuel incidents begin - the problem is created on the ground, not in the air.
2. Can the flight depart with the right-seat pilot's lapsed medical, and what documentation must be on board?
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Crew status. A lapsed medical removes the privilege to act as a required crew member: that pilot may not act as PIC, may not be a required co-pilot, and may not log the time as pilot flying. The aircraft is a single-pilot type, so the validly medically certificated pilot must be the sole PIC. The second pilot may travel as a passenger; briefing, radio work or hand-flying under the supervision of the PIC does not restore a crew privilege that the medical has removed.
Note that insurance cover is usually conditional on the named pilot holding a valid licence and medical - a lapsed medical can void cover even if the other pilot is legal.
Documents. In practice the on-board set is: certificate of registration, certificate of airworthiness, insurance certificate, flight/technical log or journey log as required, aircraft flight manual, weight and balance schedule, and radio station licence where applicable; both pilots carry licence and medical. Exact titles vary - confirm the current GCAA Civil Aviation Regulations rather than relying on memory, because the responsibility for carrying them rests with the PIC.
3. In flight, ATC places you in a 15-minute hold at destination. What is your response, and how does it differ from the ground-delay case?
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Cost the hold immediately. 15 minutes at 34 L/h = 8.5 L, against a departure surplus of about 5 L (less the 3–4 L already burned on the ground). The hold alone puts the aircraft below final reserve at destination. This is no longer a planning nicety; it is a fuel-integrity problem.
Options, cheapest first.
- Reduce burn: lean aggressively, slow to best-endurance speed - recovers perhaps 1–2 L over the hold, not 8.5 L.
- Refuse the hold: request the shortest approach or a visual; a hold accepted silently is a decision made for you.
- Divert: the alternate costs 12 L, which the plan already funded, but the surplus does not.
Declarations. If you are committed to landing at destination and cannot accept further delay, state MINIMUM FUEL early - it is advisory and buys priority. If the calculation shows landing with less than final reserve, the correct call is MAYDAY FUEL. Declaring late, when the tanks are already dry, converts an administrative inconvenience into an emergency. The ground-delay case allowed refuelling as a fix; in the air the only fix is an earlier decision.