9. approach and landing
- 1. 9. APPROACH AND LANDING Performance JAR 25
- 2. APPROACH AND LANDING Approach definition Approach and landing speeds • Maximum speeds • Minimum speeds • Final approach speed Landing weight limitations Climb requirements Landing distances Factors affecting landing distance Charts
- 3. APPROACH The approach is defined as a flight phase where the aeroplane configuration is changed from clean configuration to landing configuration, and the aircraft is positioned in such a way that it can safely touch down at the correct part of the runway on landing. Landing limitations are usually less constraining than takeoff ones. This may lead to a minimisation of the importance of landing checks during dispatch.
- 4. SPEEDS MAXIMUM SPEEDS Maximum speeds are established for the operation of some movable devices of the aircraft, in order not to damage them. These speeds are usually included in the speeds placard, which is placed somewhere in the cockpit. Some of these speeds are: Maximum speed brakes speed: In most aircraft this speed is equal to the Vmo / Mmo speed. Maximum flaps extension speed (Vfe): It is the maximum speed at which slats/flaps can be operated. Maximum landing lights extension speed: Some aircraft (MD-80) have to deploy the landing lights since they are not allocated in the airframe. Thus, a speed limitation exists in order to extend the lights. Maximum Wiper operation speed: Sometimes a maximum speed for wipers operation is established.
- 5. SPEEDS Maximum landing gear operating speed: This is the maximum speed at which the landing gear can be extended or retracted. Sometimes the speed limit for extension is different from the one for retraction. Maximum landing gear extended speed: The maximum speed with the landing gear down. Be careful, sometimes it is greater than the landing gear retraction speed.
- 6. SPEEDS MINIMUM SPEEDS For a given weight and configuration, two minimum speeds are established: 1. Minimum manoeuvring speed (VMAN): It is the minimum speed which permits banks of up to 30º with a given configuration. For clean configuration, this speed is known as VCLEAN. If we want to fly below this speed, bank angle must be limited to 15º; or, to keep full manoeuvrability, slats/flaps must be extended. VMAN = 1.5 Vs1
- 7. SPEEDS 2. Reference speed (VREF): It is the steady landing approach speed at the 50 feet point for a defined landing configuration. It is used as a reference (hence its name) for calculating the final approach speed and the landing distance. VREF = 1.3 · VS0 = 1.23 VS1g
- 8. SPEEDS FINAL APPROACH SPEED (VAPP) VAPP is the actual aircraft speed during landing, 50 feet above the runway surface. The flaps/slats are in landing configuration, and the landing gears are extended. It is based upon the reference speed. To calculate VAPP, we will increase VREF in 5 kts, plus a value depending on the wind. This value is calculated in a different way for each aircraft. An additional correction may be made with some systems inoperative: VAPP = VREF + 5 kts + ΔVwind and/or gusts + ΔVsystems inoperative
- 9. LANDING WEIGHT LIMITATIONS Every flight must be planned in such a way that the actual landing weight is less than the operational landing weight: ALW ≤ OLW ≤ MLW The OLW is affected by these factors: Climb requirements in approach configuration. Climb requirements in landing configuration. Runway length Braking capability and tyre limitations. Pavement limitations.
- 10. CLIMB REQUIREMENTS In case of performing a missed approach procedure, the aircraft must be able to climb with a minimum gradient. Two different minimum gradients have been established, one for approach configuration and another for landing configuration: APPROACH CONFIGURATION • Gear up • Flaps approach • 1 ENG OUT • TOGA thrust • Speed = 1.5 · VS1 APPROACH 2 ENGINES 3 ENGINES 4 ENGINES MIN GRADIENT 2.1 % 2.4 % 2.7 %
- 11. CLIMB REQUIREMENTS LANDING CONFIGURATION • Gear down • Full flaps • All engines operative • TOGA thrust • Speed = 1.3 · VS0 LANDING 2 ENGINES 3 ENGINES 4 ENGINES MIN GRADIENT 3.2 %
- 12. CLIMB REQUIREMENTS 3.2 % 2.1 % - 2 ENG 2.4 % - 3 ENG 2.7 % - 4 ENG 1 ENG OUT ALL ENGINES
- 13. LANDING DISTANCES LANDING DISTANCE It is the distance measured between a point 50 feet above the runway threshold, and the point where the aircraft comes to a complete stop. 50 ft Landing distance VREF
- 14. LANDING DISTANCES The landing distance is measured under certain conditions: Standard temperature. Landing configuration. Stabilised approach at VREF over the threshold. Determination on a level, smooth, dry, hard-surfaced runway. Acceptable pressures on the wheel braking systems. Usage of spoilers. No use of reverse thrust. Additional landing distances are also certified with degraded braking means (spoiler inoperative, one brake inoperative…).
- 15. LANDING DISTANCES LANDING DISTANCE AVAILABLE It is the length of runway which is declared available and suitable for the ground run of an aeroplane landing. It is also a declared distance, and it will be equal to the TORA if there is no displaced threshold. Stopways are not included in the LDA.
- 16. LANDING DISTANCES The landing distance available (LDA) may be shortened due to the presence of obstacles under the landing path, noise abatement, etc. When there is no obstacle within the approach funnel, as defined below, it is possible to use the runway length to land.
- 17. LANDING DISTANCES However, if there is an obstacle within the approach funnel, a displaced threshold is defined considering a 2% plane tangential to the most penalizing obstacle plus a 60 m margin. In this case LDA = TORA – Displaced threshold
- 18. LANDING DISTANCES LANDING DISTANCE REQUIRED (JET) A turbo-jet aircraft must be able to land within 60% of the LDA*. 50 ft Landing distance required (60 % LDA) Landing distance available (LDA) * Another way of expressing it is LDA = 167 % LDR.
- 19. LANDING DISTANCES LANDING DISTANCE REQUIRED (TURBOPROP) A turboprop aircraft must be able to land within 70% of the LDA. 50 ft Landing distance required (70 % LDA) Landing distance available (LDA) * Another way of expressing it is LDA = 143% LDR.
- 20. LANDING DISTANCES LANDING DISTANCE REQUIRED (WET RUNWAY) If the runway is wet, then the landing distance required is 115% of the corresponding LDR for a dry runway. 50 ft Landing distance required (dry runway) Landing distance available (LDA) Landing distance required (wet runway) = 115% LDR (dry)
- 21. FACTORS AFFECTING LANDING WEIGHT If weight is increased, VREF will be higher, giving as a result a longer landing distance. DENSITY ALTITUDE Since VREF is expressed in terms of IAS, an increase of DA will increase TAS, so the landing distance will be increased as well. A rule of thumb is: an increase of 1000 ft in DA produce a 2% increase of the landing distance. RUNWAY SLOPE Since maximum slope is 2%, its effect on the landing distance is considered negligible.
- 22. FACTORS AFFECTING LANDING WIND Since wind changes ground speed, it is obvious that headwind will reduce the landing distance and tailwind will increase it. Take into account that performance charts compute 50% of headwind and 150% of tailwind, as a margin for safety reasons. FLAPS Flap setting will change VREF, and therefore landing distance. High flap settings will give short landing distances, while lower flap settings will result in longer distances.
- 23. FACTORS AFFECTING LANDING FLYING TECHNIQUE One of the factors that most affect landing distance in a real flight is the flying technique. If landing speed is not properly maintained, glide path is too steep or the height above threshold is higher than usual, the landing distance may be increased dramatically. Therefore it is essential to fly a good approach in order to have a good landing. INOPERATIVE SYSTEMS If some of the braking systems is inoperative (spoilers, one of the brakes, anti-skid…), the landing distance will also be increased. It is important to check LDA in such cases.
- 24. LANDINGDISTANCES
- 25. LDR