Extra fuel & tankering

033 Flight PlanningChapter 5

Beyond mandatory fuel, operators may carry extra fuel for commercial or operational reasons — subject to mass limits and the fuel penalty of carrying additional weight.

Extra fuel vs additional fuel

Definition — Additional fuel

Legally required when trip + contingency + alternate + final reserve is insufficient for pressurisation failure or engine-out scenarios.

Definition — Extra fuel

PIC discretion — not legally mandated. Includes fuel tankering when cheaper to uplift at departure.

Fuel tankering

Key fact

Fuel tankering — carrying extra fuel because fuel is cheaper at departure than at destination. Consider when:

• Weather at destination is below minima (may need holding/diversion margin), or
• No suitable fuel at planned destination

Definition — Fuel penalty

Extra fuel burned because of the weight of carrying that extra fuel. Reduces the net benefit of tankering.

Formula — Fuel Price Ratio (FPR)

FPR = Price at Departure ÷ Price at Arrival

Tankering is only worth considering when FPR is less than 1 (departure price lower than arrival price).

Exam trap

FPR less than 1 means departure fuel is cheaper. FPR greater than 1 means arrival is cheaper — tankering from departure is not economically attractive.

Calculating extra fuel capacity

Formula — Step 1 — actual masses

Actual ZFM = DOM + Traffic Load

Actual TOM = Actual ZFM + Take-off fuel

Actual LM = Actual TOM − Trip fuel

Actual ramp mass = Actual TOM + Taxi fuel

Formula — Step 2 — limiting extra fuel

Most limiting (lowest) of:

• MTOM − ATOM
• MLM − ALM (= uncorrected extra fuel, before penalty correction)
• Max ramp mass − actual ramp mass
• Tank capacity remaining (Tank capacity − taxi − take-off fuel already on board)

Formula — Fuel penalty correction

Corrected extra fuel = (Uncorrected extra fuel ÷ fuel penalty difference) × 1000

Where fuel penalty difference is given in kg per 1000 kg or equivalent exam data.

Key fact

Max permitted take-off fuel = Limiting take-off fuel plus trip fuel (when question defines limiting TOF as the structural cap at rotation).

Traffic load vs fuel load terminology

Key fact

If the question states additional load, it means traffic load: MZFM − Actual ZFM.

If the question states fuel load, it means extra fuel load beyond mandatory planning fuel.

Landing mass limits with fuel

Key fact

At destination, landing mass = ZFM + fuel remaining. Minimum planned fuel at destination = Alternate + Final Reserve (lowest case). At alternate: Final Reserve + Contingency as applicable.

Formula — Piston range check (useable fuel)

Useable fuel = Block − Taxi − Alternate − 45 min holding − 5% contingency

Range = (Useable fuel ÷ fuel consumption) × GS

Centre tank transfer failure

Key fact

If centre pump fails, fuel is consumed from wings first while fuel transfers from centre to wings:

• Transferred fuel = Transfer rate × time
• Remaining fuel = (Transferred + wing fuel) − (consumption × time since failure)
• Endurance left = Remaining fuel ÷ fuel consumption

Exam trap

Always identify the most limiting mass — exam questions give four caps and expect the lowest uncorrected extra fuel, then optionally apply fuel penalty correction. Forgetting taxi fuel in tank capacity calculations is a common slip.