Technological Institute of Aeronautics

São José dos Campos - São Paulo - Brazil

Requirement 1: Landing Field Length (LFL)

Background

landing distance, landing field length, landing distance available

The landing distance (LD) is defined in the aviation regulations:

JAR 25.125 Landing.
(a) The horizontal distance necessary to land and to come to a complete stop from a point 50 feet above the landing surface must be determined ... as follows:
(1) The airlane must be in the landing configuration.
(2) A stabilized approach, with a calibrated airspeed of not less than 1.3 VS, must be maintained down to the 50 foot height.

For jet powered aircraft, the landing field length (LFL) is 1/0.6 = 1.667times the landing distance and must not be more than the landing distance available (LDA). This follows from JAR OPS 1.515:

JAR - OPS 1.515 Landing - Dry Runways
(a) An operator shall ensure that the landing mass of the airplane ... allows a full stop landing from 50 ft above the threshold:
(1) Within 60 % of the landing distance available at the destination aerodrome and at any alternate aerodrome for turbojet powered airplanes ... .

The landing distance available has to be less or equal than the safety landing field length.

Figure 1: animation of landing field

Typical landing field lengths

Equations

The landing field length requirement determines an upper limit for the wing loading. The equation for the wing loading is calculated from four basic equations.

1. equilibrium (weight = lift):

2. Loftin'statistic:

3. minimum approach speed:

4. mass ratio:

These equations combined and solved for the wing loading m_MTO /S_W yields
result equation

with a factor k_L = 0.119 kg/m³, the density at sea level = 1.225 kg/m³.
Lift-coefficient c_L,max,L, landing field length s_LFL
and mass ratio m_ML/m_MTO are chose from statistics.

A click on a variable/equation informs about the background.

Data

Maximum landing lift-coefficient:

The maximum landing lift-coefficient depends on the type of the high lift systems. Several systems were developed to increase the lift coefficient with the intention to decrease the approach velocity. The values of the lift coefficient range from 1.3 for a clean profil and to 3.0 for a profil with Fowler flaps and slats. Today's aircraft have maximum landing lift-coefficients of around 2.6. For details see e.g. Dubs 1987 or Roskam 1989.

Statistics of lift-coefficient

Typical wing loading

The wing loadings of existing aircraft are provided below for comparison purposes.

wing loading and approach speed of selected aircraft Jane's 1995-98

Aircraft	Airbus A 300-600B	A 310-300	A 340-300	Antonov AN 124	Boeing B 737-600	B 777	Learjet 60	McDonnell Douglas MD11	Tupolev TU 204
Wing loading [kg/m²]	634.6	684.9	707.8	644.9	520.7	567.2	433.8	806.4	518.6
Approach speed [m/s]	69.2	69.4	N/A	63.8-72.2	64.7	71.1	71.4	N/A	61.1

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