Hot-day departure from Be'er Sheva with four adults
You are planning a midday VFR departure from Be'er Sheva (LLBS) to Eilat Ramon (LLER) in a four-seat single-engine piston aeroplane. Basic empty mass is 735 kg and MTOM is 1,150 kg. The OAT is 34°C, QNH 1008 hPa, and aerodrome elevation is about 920 ft. The AFM take-off chart for 1,150 kg at 30°C and 1,000 ft pressure altitude shows a ground roll of 620 m and a 50 ft obstacle distance of 1,080 m. The declared take-off distance available is 1,150 m on dry asphalt with a 0.7% upslope. Your loading is pilot 82 kg, three passengers 88 kg, 76 kg and 91 kg, baggage 35 kg, and 160 L avgas at 0.72 kg/L. Planned cruise burn is 32 L/h, trip time 1.4 h, and reserve 30 min. No refuelling is available at LLER. You have 25 minutes before the airport closes for a military movement.
1. Calculate the take-off mass and determine whether the flight is legal as loaded.
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Basic empty mass 735 kg + pilot/passengers 337 kg + baggage 35 kg = 1,107 kg. Fuel is 160 L × 0.72 = 115.2 kg, so take-off mass is 1,222.2 kg, which is 72.2 kg above MTOM. The flight is therefore not legal as loaded. Now check the minimum fuel needed: trip fuel is 32 L/h × 1.4 h = 44.8 L; reserve is 16 L; total 60.8 L = 43.8 kg. Even with only that fuel, mass would be 1,150.8 kg, still about 0.8 kg over MTOM. In practice you must offload at least a few kilograms and reduce fuel to about 60 L, but that leaves no taxi, climb, headwind or delay contingency. A safer decision is to offload 20–30 kg of baggage or one passenger, then recompute mass and CG.
2. Evaluate the take-off performance at the actual temperature and runway slope, and state whether the available distance is sufficient.
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Pressure altitude is about 920 ft + (1013 − 1008) × 30 ft ≈ 1,070 ft. ISA temperature at that altitude is about 13°C, so 34°C is roughly ISA +21°C. The chart already shows 1,080 m to 50 ft at 30°C and 1,000 ft; at 34°C the distance will be roughly 10–15% greater, about 1,190–1,240 m before slope. A 0.7% upslope adds further distance, so the effective requirement is likely above 1,250 m. That exceeds the 1,150 m TODA. The ground roll may still fit, but the 50 ft obstacle distance does not. Performance is therefore not acceptable even if the mass is reduced slightly; a cooler time of day or a significant mass reduction is needed.
3. What would you do about the 25-minute closure deadline?
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The closure deadline is operational pressure and must not override mass-and-balance or performance limits. Departing overweight or with insufficient obstacle clearance to save a slot is not justified. The correct decision is to delay or cancel, or to offload enough mass and recalculate both WAT performance and fuel. If a delay means the airport closes before departure, use the next available window or depart from another aerodrome. Notify the operator or passengers, and do not rush the before-take-off checks. A useful cross-check is to compare the recalculated 50 ft distance with TODA plus a personal margin, not just with the bare chart figure.