Aeroplane performance in the planning phase: take-off, climb, cruise, descent and landing
Domain 5 covers aeroplane performance as used in planning: field requirements, climb limitations and the climb, cruise and descent figures that feed the flight plan.
Take-off and landing
- Declared distances: TORA, TODA (TORA + clearway), ASDA (TORA + stopway) and LDA; the take-off mass must give a take-off distance within TODA and an accelerate-stop distance within ASDA.
- Charts are entered with pressure altitude, temperature, mass, wind, slope, runway condition and configuration; apply each correction exactly as the chart directs.
- Headwind credit is normally limited (often 50% of the reported headwind), while a tailwind penalty rises steeply and is typically limited to about 10–15 kt.
- Landing mass is checked against LDA at destination and alternate, using the expected runway condition and permitted reverse-thrust credit.
Climb, cruise, descent
- Certification climb gradients: second segment 3.3% for twins, 2.4% for three engines, 2.0% for four; en-route gradient 1.1%, 1.4% and 1.6% respectively.
- Cruise speed is chosen as long-range, maximum-range or cost-index speed; descent planning uses a 3° path, which is about 318 ft/NM, or roughly 3 NM per 1,000 ft.
Worked example
An 800 NM sector at FL350. Climb: 130 NM, 20 min, 1,800 kg. Descent from FL350 to 3,000 ft on a 3° path needs 32,000 / 1,000 × 3 = 96 NM and 13 min, burning 400 kg. Cruise distance = 800 − 130 − 96 = 574 NM. At TAS 460 kt with a 50 kt tailwind the ground speed is 510 kt, so cruise time = 574 / 510 = 1.13 h = 68 min. Air time = 20 + 68 + 13 = 101 min. At 2,400 kg/h cruise flow, cruise fuel = 2,720 kg, so trip fuel ≈ 1,800 + 2,720 + 400 = 4,920 kg.
Traps
- Reading a chart at indicated altitude instead of pressure altitude.
- Assuming the full reported headwind can be credited.
- Using a flat 300 ft/NM for all descents without checking the charted figure.
- Forgetting that landing performance must also be checked at the destination alternate.
- Ignoring the effect of anti-ice or packs on climb gradient and fuel.