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Lesson 7 · Flight Performance & Planning

Fuel Planning

The Part-NCO fuel blocks, the final-reserve rule, and planning fuel you can trust — EASA PPL theory

⏱ ~20 min ✈ SEP · VFR 📋 EASA Part-FCL

1 — Fuel Is Time, and Fuel Is Mass

Fuel exhaustion is one of the most preventable causes of accidents — it is an arithmetic problem, not bad luck. Two ideas from earlier lessons meet here: fuel is time (litres ÷ fuel flow = hours, from Lesson 4) and fuel is mass (litres × density = kg, which you loaded in Lesson 6).

Usable vs unusable
Only usable fuel counts for planning. A litre or two is trapped in the system and unusable — never plan to burn into it, and never plan to burn into your final reserve.

2 — The Fuel Blocks

Part-NCO builds your total — the block fuel — from named pieces. Everything except extra is the legal minimum to depart.

The fuel you carry — block by block
Final reserve 15 L Alternate 12 L Contingency 4 L Trip 45 L Taxi 3 L Extra 9 L Final reserve — planned never to be used Minimum required to depart Block (total) fuel: 88 L
  • Taxi — fuel to start, taxi and run up before takeoff.
  • Trip — climb, cruise and descent to the destination.
  • Contingency — a margin for the unexpected (winds, routing); commonly about 5% of trip fuel.
  • Alternate — trip fuel on to an alternate aerodrome, when one is planned.
  • Final reserve — the protected block you must still have on landing (next section).
  • Extra — discretionary fuel the pilot-in-command adds on top.

3 — The Final Reserve Rule

The final reserve is the line you never plan to cross. Under EASA Part-NCO (NCO.OP.125) for an aeroplane:

Final reserve — the fuel you cannot plan to touch
VFR by day 30 min at normal cruising altitude
VFR by night 45 min at normal cruising altitude
IFR 45 min at normal cruising altitude

NCO.OP.125. The newer fuel-scheme guidance also frames final reserve by engine: ~45 min piston / 30 min turbine at 1 500 ft.

Plan to land with it untouched
The final reserve is a planning minimum, not “spare fuel”. If your plan would land you with less than the final reserve, the plan is illegal — and if in flight you expect to land below it, that is a reason to divert and may warrant a PAN/MAYDAY fuel call.

4 — Plan Your Fuel

Every block comes from the same arithmetic: fuel = time × fuel flow. Set a trip and watch the blocks add up, against 120 L of usable fuel:

Plan your fuel
ItemLitres
—
— · —

Illustrative figures (taxi 3 L, 120 L usable). Real planning uses your aircraft’s POH and the current Part-NCO rules.

If it doesn’t fit
When the minimum block exceeds usable fuel, you cannot legally or safely make the trip as planned — reduce trip distance, add a fuel stop, or reduce load. You do not raid the reserve.

5 — Worked Example & the Golden Rules

Trip 80 min at 30 L/hr, 5% contingency, no alternate, VFR by day, taxi 3 L:

  1. Trip: 80 ÷ 60 × 30 = 40 L.
  2. Contingency: 5% × 40 = 2 L.
  3. Final reserve (day): 30 ÷ 60 × 30 = 15 L.
  4. Taxi: 3 L. Minimum block = 3 + 40 + 2 + 15 = 60 L (≈ 43 kg — carry that figure into your weight & balance).

The golden rules
1. Fuel = time × fuel flow. 2. Plan to land with the final reserve intact (VFR day 30 min, night 45 min). 3. Only usable fuel counts. 4. The fuel you plan is mass — feed it back into weight & balance.

Knowledge Check

Question 1
Under EASA Part-NCO, the final reserve for an aeroplane flying VFR by day is fuel for:
Question 2
The same flight is now planned VFR by night. The final reserve becomes:
Question 3
Cruise fuel flow is 28 L/hr. A 90-minute trip leg needs trip fuel of about:
Question 4
Your plan would land you with exactly 5 L less than the final reserve. You should:
Question 5
Which blocks make up the legal minimum fuel to depart?

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