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Landing Distances
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| Category: | General | 
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| Content source: | SKYbrary | 
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| Content control: | EUROCONTROL | 
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Definitions
The terms Landing Distance Required (LDR) and Landing Distance Available (LDA) are not defined for fixed wing aeroplanes in ICAO SARPS.
ICAO SARPS define the Landing Distance as follows: the horizontal distance traversed by the aeroplane by the aeroplane from a point on the approach path at a selected height above the landing surface to the point on the landing surface at which the aeroplane comes to a complete stop. (ICAO Annex 8 Part IIIA Paragraph 2.2.3.3. and Part IIIB Sub-part B Paragraph B2.7 e)). This is generally referred to as the Landing Distance Required (LDR).
The Landing Distance Available (LDA) is the length of the runway which is declared available by the appropriate Authority and suitable for the ground run of an aeroplane landing. EU-OPS 1.480 (a)(5).
Calculation of LDR
Put simply, the LDR must be less than the LDA.
EU-OPS 1 Sub-part G specifies safety factors that must be applied in determination of the LDR (see below).
The LDR depends on a number of factors, principally:
- The aircraft landing mass;
- The surface wind and temperature;
- The runway elevation and slope;
- The runway surface conditions (dry, wet or contaminated); and,
- The condition of aircraft braking systems.
Aircraft performance (LDR and landing speed) is calculated by the pilots using printed tables or a computer. This calculation takes account of the above factors, including the safety factor. It is assumed for these calculations that the aircraft will be at a specified height (normally 50 ft) crossing the runway threshold at the correct speed, and that aircraft handling will be in accordance with procedures detailed in the AFM and company SOPs.
Safety factors vary according to the aircraft type (turbo-jet or turbo-prop), the runway conditions (dry, wet or contaminated) and in pre-departure planning, whether the airfield is the destination or an alternate.
Special provisions apply to steep approaches and to short landing operations.
Factors Affecting Actual Landing Distance
Handling.
Landing an aircraft is a difficult process requiring considerble manual dexterity. The pilot must achieve the following goals:
- On passing the runway threshold:
- 50 ft above runway threshold;
- Aircraft configured for landing (landing gear, flaps and slats, etc.);
- Correct and steady forward speed;
- Correct and steady descent rate;
- Appropriate power setting;
- Wings level.
- On touch-down:
- Brakes applied;
- Power reduced;
- Additional devices deployed (thrust reversers, lift dump, etc.);
- Directional control maintained.
Unserviceability of any of the devices which affect the aircraft braking (brakes, anti-skid, reverse thrust, lift-dump, etc.) can have a serious effect on landing performance. (Note: landing performance calculations normally assume that reverse thrust is not available)
Major unserviceability (e.g. engine malfunction) complicates handling considerably; however, any unserviceability, even if not serious on its own, may add to control difficulties.
The complexity of the task (even with Autoland) is such that even in ideal conditions, a perfect landing is virtually impossible, while any deviation from the ideal adds to the actual landing distance.
Runway Conditions.
The maximum landing mass and the landing speed depend on the runway braking conditions. If these have been inaccurately reported or if the runway is wet or contaminated when its condition was reported as being dry, the landing distance achieved will be increased.
The presence of standing water, snow, slush or ice on the runway has a particularly serious effect on landing performance and if it cannot be cleared, it must be reported as accurately as possible. Special techniques must be used by pilots when landing on contaminated runways.
Weather Conditions.
The maximum landing mass and landing speed is calculated based on the reported wind and temperature. Significant changes to the reported conditions will affect the landing distance achieved.
Strong cross-winds, turbulence and wind shear make handling difficult and are likely to result in an increased landing distance.
Effect of Factors on Landing Distance
Flight Safety Foundation (FSF) Approach-and-landing Accident Reduction (ALAR) Briefing Note 8.3 — Landing Distances contains the following diagram which shows the approximate effects of various factors on landing distance:
- Figure 2 - Landing Distance Factors
Related ICAO Provisions
- Annex 14, Volume I - 3. Calculation of declared distances - 3.1
- Annex 14, Volume I - 3. Calculation of declared distances - 3.2
- Annex 14, Volume I - 3. Calculation of declared distances - 3.3
- Annex 14, Volume I - 3. Calculation of declared distances - 3.4
- Annex 14, Volume I - 3. Calculation of declared distances - 3.5
- Annex 14, Volume I - 3. Calculation of declared distances - 3.6
- Annex 14, Volume I - 3. Calculation of declared distances - 3.7
Related Articles
Further Reading
ICAO Annex 8: Airworthiness Part III Chapter 2;
EU-OPS 1: Sub-part G, especially EU-OPS 1.510 - EU-OPS 1.520 and associated AMCs and appendices relate to Performance Class A operations. Sub-parts H and I contain provisions relating to Performance Group B and C aircraft respectively.
Flight Safety Foundation
The Flight Safety Foundation ALAR Toolkit provides useful training information and guides to best practice. Copies of the FSF ALAR Toolkit may be ordered from the Flight Safety Foundation ALAR website http://www.flightsafety.org/current-safety-initiatives/approach-and-landing-accident-reduction-alar