getting to grips with aircraft performance 如何掌握飞机性能 2(3)

曝光台 注意防骗 网曝天猫店富美金盛家居专营店坑蒙拐骗欺诈消费者

In the next chapters, we will specify landing requirements based on airworthiness rules, and dispatch conditions. A final chapter will address the flight management and the choice of a diversion landing airport.
2. LANDING DISTANCE AVAILABLE (LDA)
2.1.  With no Obstacle under Landing Path
In this case, the Landing Distance Available (LDA) is the runway length (TORA). The stopway cannot be used for landing calculation.

2.2. With Obstacles under Landing Path
The landing distance available (LDA) may be shortened, due to the presence of obstacles under the landing path.
Annex 8 of ICAO recommendations specifies the dimension of the protection surfaces for landing and approach (Approach funnel).
When there is no obstacle within the approach funnel, as defined below (see Figure E2), it is possible to use the runway length to land.

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 (Figure E3).

In this case, the Landing Distance Available (LDA) is equal to the length measured from the displaced threshold to the end of the runway.
3. LANDING PERFORMANCE

 

3.1. Operating Landing Speeds
Originally, the speeds defined in next chapters were manufacturer or operator operating speeds. Today, most of them (as the term VREF the reference landing speed for example) are widely used and understood operationally. The JAR authorities found it convenient to use the same terminology in stating airworthiness requirements and have, indeed, been used in recent requirement amendments.

3.1.1. Lowest Selectable Speed: VLS
As a general rule, during flight phases, pilots should not select a speed below VLS (Lowest Selectable Speed), defined as 1.23 VS1g of the actual configuration.
 VLS = 1.23 Vs1g g
* The 1.23 factor is applicable to the fly-by-wire aircraft (1.3 for the others).
This rule applies for landing. During landing, pilots have to maintain a stabilized approach, with a calibrated airspeed of no less than VLS down to a height of 50 feet above the destination airport.

3.1.2. Final Approach Speed: VAPP
VAPP is the aircraft speed during landing, 50 feet above the runway surface. The flaps/slats are in landing configuration, and the landing gears are extended.
VAPP is limited by VLS:
VAPP ≥
 VLS
It is very common to retain a margin on VLS to define VAPP. For Airbus aircraft, in normal operations, the VAPP is defined by:
 VAPP = VLS + wind correction
Wind correction is limited to a minimum of 51 knots, and a maximum of 15 knots. VAPP is displayed on MCDU APPRoach page.
The FMGS and managed speed is used to define the VAPP TARGET. It gives efficient speed guidance in approach with windy conditions, since it represents:
VAPP TARGET = GS mini + actual headwind
　
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
本文链接地址：getting to grips with aircraft performance 如何掌握飞机性能 2(3)