aerosandbox.library.field_lengths
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Module Contents#
Functions#
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Performs a field length analysis on an aircraft, returning a dictionary of field length parameters. |
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Attributes#
- aerosandbox.library.field_lengths.field_length_analysis_torenbeek(design_mass_TOGW, thrust_at_liftoff, lift_over_drag_climb, CL_max, s_ref, n_engines, atmosphere=None, CD_zero_lift=0.03, obstacle_height=35 * u.foot, friction_coefficient=0.02, V_obstacle_over_V_stall=1.3, minimum_V_liftoff_over_V_stall=1.2, V_approach_over_V_stall=1.3, maximum_braking_deceleration_g=0.37, inertia_time=4.5, approach_angle_deg=3)[source]#
Performs a field length analysis on an aircraft, returning a dictionary of field length parameters.
Citations:
“Torenbeek”: Egbert Torenbeek, “Synthesis of Subsonic Airplane Design”, 1976. (Generally, section 5.4.5:
Takeoff)
- Parameters:
design_mass_TOGW (float) – The takeoff gross weight of the entire aircraft [kg].
thrust_at_liftoff (float) – The thrust of the aircraft at the moment of liftoff [N].
lift_over_drag_climb (float) – The lift-to-drag ratio of the aircraft during the climb phase of takeoff [dimensionless].
CL_max (float) – The maximum lift coefficient of the aircraft [dimensionless]. Assumes any lift-augmentation devices (
e.g. –
slats –
deployed. (flaps) are) –
s_ref (float) – The reference area of the aircraft [m^2].
atmosphere (aerosandbox.Atmosphere) – The atmosphere object to use for the analysis. Defaults to sea level.
n_engines (int) – The number of engines on the aircraft. Used during balanced field length calculation,
assumption. (which involves a single-engine-failure) –
CD_zero_lift (float) – The zero-lift drag coefficient of the aircraft [dimensionless].
obstacle_height (float) –
The height of the obstacle clearance [m].
Note
FAR 23 requires a 50 foot obstacle clearance height.
FAR 25 requires a 35 foot obstacle clearance height.
friction_coefficient (float) –
The coefficient of friction between the wheels and the runway.
0.02 is a good value for a dry concrete runway.
0.045 is a good value for short grass.
V_obstacle_over_V_stall (float) – The ratio of the airspeed while flying over the obstacle to the stall airspeed.
minimum_V_liftoff_over_V_stall (float) – The minimum-allowable ratio of the liftoff airspeed to the stall airspeed.
V_approach_over_V_stall (float) – The ratio of the approach airspeed to the stall airspeed.
maximum_braking_deceleration_g (float) –
The maximum deceleration of the aircraft during braking [G].
This is used when calculating the “brake” portion of the “accelerate-brake” balanced field length, as well as the braking during normal landing.
Standard brakes are around 0.37 G on dry concrete.
Advanced brakes with optimum brake pressure control, lift dumpers, and nosewheel braking can be as high
as 0.5 G on dry concrete.
inertia_time (float) – The time it takes for the pilot and aircraft to collectively react to an engine failure during
of (takeoff [seconds]. This is collectively the sum) –
The pilot’s reaction time
The time it takes the other engines to spool down, in the event of a rejected takeoff and deceleration
on the ground.
approach_angle_deg (float) –
- Returns:
“takeoff_ground_roll_distance”: The distance the aircraft will roll on the ground during a normal
takeoff before liftoff [meters].
”takeoff_airborne_distance”: The distance the aircraft will travel in the air during a normal takeoff [
meters]. This is after liftoff, but before the aircraft has reached the obstacle clearance height.
”takeoff_total_distance”: The total field length required during a normal takeoff [meters]. This
includes both the ground roll itself, as well as the airborne distance before the obstacle clearance height is reached.
”balanced_field_length”: The field length required for takeoff and obstacle clearance when one engine
fails at “decision speed” [meters]. Decision speed is the speed during the ground roll at which, if an engine fails, the aircraft can either continue the takeoff or brake to a complete stop in the same total distance.
”landing_airborne_distance”: The distance the aircraft will travel in the air during a normal landing
before touchdown [meters]. Note that a normal landing involves passing the runway threshold at the specified obstacle clearance height.
”landing_ground_roll_distance”: The distance the aircraft will roll on the ground after touchdown
during a normal landing [meters].
”landing_total_distance”: The total field length required during a normal landing [meters]. This
includes both the airborne distance beyond the threshold that is required for obstacle clearance, as well as the ground roll distance after touchdown.
”V_stall”: The stall speed of the aircraft at its takeoff gross weight [m/s].
”V_liftoff”: The airspeed at the moment of liftoff during a normal takeoff [m/s].
”V_obstacle”: The airspeed when the aircraft reaches the obstacle clearance height during a normal
takeoff [m/s].
”V_approach”: The airspeed when the aircraft reaches the runway threshold during a normal landing.
”V_touchdown”: The airspeed when the aircraft touches down during a normal landing.
”flight_path_angle_climb”: The flight path angle during a normal takeoff at the point when the airplane
reaches the obstacle clearance height [radians].
”flight_path_angle_climb_one_engine_out”: The flight path angle during a critical-engine-out takeoff at
the point when the airplane reaches the obstacle clearance height [radians]. If this number is negative, engine failure results in inability to climb.
- Return type:
A dictionary of field length parameters, including
- aerosandbox.library.field_lengths.field_length_analysis(design_mass_TOGW, thrust_at_liftoff, lift_over_drag_climb, CL_max, s_ref, n_engines, V_engine_failure_balanced_field_length, atmosphere=None, CD_zero_lift=0.03, obstacle_height=35 * u.foot, friction_coefficient=0.02, minimum_V_liftoff_over_V_stall=1.2, maximum_braking_deceleration_g=0.37, inertia_time=2, approach_angle_deg=3)[source]#
- Parameters:
design_mass_TOGW (float) –
thrust_at_liftoff (float) –
lift_over_drag_climb (float) –
CL_max (float) –
s_ref (float) –
n_engines (int) –
V_engine_failure_balanced_field_length (float) –
atmosphere (aerosandbox.Atmosphere) –
CD_zero_lift (float) –
obstacle_height (float) –
friction_coefficient (float) –
minimum_V_liftoff_over_V_stall (float) –
maximum_braking_deceleration_g (float) –
inertia_time (float) –
approach_angle_deg (float) –
- Return type:
Dict[str, float]