032 AEROPLANE PERFORMANCE - The Airline · PDF file4/1/2000 · Engine Performance...

032 AEROPLANE PERFORMANCE
G LONGHURST 1999 All Rights Reserved Worldwide
mailto:[email protected]://www.click2ppsc.com/

COPYRIGHTAll rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or
transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior permission of the author.
This publication shall not, by way of trade or otherwise, be lent, resold, hired out or otherwise circulated without the author's prior consent.
Produced and Published by the
CLICK2PPSC LTD
EDITION 2.00.00 2001
This is the second edition of this manual, and incorporates all amendments to previous editions, in whatever form they were issued, prior to July 1999.
EDITION 2.00.00 1999,2000,2001 G LONGHURST
The information contained in this publication is for instructional use only. Every effort has been made to ensurethe validity and accuracy of the material contained herein, however no responsibility is accepted for errors ordiscrepancies. The texts are subject to frequent changes which are beyond our control.
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TABLE OF CONTENTS
Basic Aerodynamics
Engine Performance
Surface Load Bearing Strength
Contaminated Surfaces
Aerodrome Surface Dimensions
Miscellaneous Definitions
Speeds
The Effect of Variables
Legislation Background
Take-off Class B Aeroplanes

TABLE OF CONTENTS
The Take-off Climb Class B Aeroplanes
En-Route - Class B Aeroplanes
Landing - Class B Aeroplanes
Performance Class A Aeroplane Take-Off
The Take-off Climb - Class A Aeroplanes
En-Route - Class A Aeroplanes
Landing - Class A Aeroplanes
Reduced Thrust Take-off - Class A Aeroplanes
Increased V2 Procedure - Class A Aeroplanes

032 Aeroplane Performance
Basic Aerodynamics
Level Flight
Climbing Flight
The Effect of Altitude on Climb Performance
The Buffet Onset Boundary Chart
Descending Flight

Basic Aerodynamics
Chapter 1 Page 1 G LONGHURST 1999 All Rights Reserved Worldwide
1Basic Aerodynamics
Level Flight1. In level, unaccelerated flight there are four main forces acting on an aeroplane. They are lift,weight, thrust and drag. To maintain level flight these forces must remain in equilibrium. Lift mustbe equal and opposite to weight and thrust must balance drag.
FIGURE 1-1The Forces in Level Flight

Basic Aerodynamics
2. To graphically depict the variations in strength of any force against speed then IAS, or morecorrectly EAS should be used because compressibility must be accounted. However, to show thevariation of power, the rate of doing work, against speed then TAS must be used.
Lift3. Lift may be defined as that force acting on an aeroplane which is at right angles to thedirection of the airflow. It can be calculated for level flight at any specified weight and altitude bythe formula:
Lift = CLV2S.
Where CL = the coefficient of lift; = air density; V = free air velocity; S = wing area.
4. The coefficient of lift is a mathematical factor that varies with the angle of attack (up to thestalling speed). To maintain level, unaccelerated flight the formula must remain in balance. If theweight and altitude are fixed then the only remaining variables in the formula are the coefficient oflift and the free air velocity. The coefficient of lift is dependent on the angle of attack for itsmagnitude. Thus if the speed is increased the angle of attack must be reduced to maintain levelflight, otherwise the aeroplane will climb. Similarly if the speed is reduced then the angle of attackmust be increased or else the aircraft will descend. All angles of attack have a corresponding IAS.Level flight can only be maintained if the formula remains in balance.

Basic Aerodynamics
5. Lift is generated by an aerofoil and is that force which acts upward at right angles to thedirection of movement of the aerofoil. It acts through a point on the aerofoil referred to as the centreof pressure (CP). This point moves forward with increasing angle of attack up to the stalling anglewhere it moves abruptly backward. The normal movement is between 30% and 20% of the chordline from the leading edge. A point, approximately 25% along the chord line from the leading edge,known as the aerodynamic centre is where, no matter what the angle of attack, the pitchingmovement remains constant at its zero lift value. Lift depends on the following factors:
(a) Forward speed
(b) Air density
(c) Viscosity of the air
(d) Wing shape
(e) Wing area
(f) Angle of attack
(g) Condition of the wing surface
(h) The speed of sound
The value of lift can be calculated from the formula:
Lift CL.1/2V2
.S=

Basic Aerodynamics
Where , the coefficient of lift is a numerical factor
is the density of the air
V is the forward speed of the aerofoil
S is the wing area which remains constant.
If = indicated airspeed, then lift = .
6. The coefficient of lift, is affected by the weight, the angle of attack, the wing shape, the
Reynolds number and the condition of the wing surface. An increase of weight causes the inducedand profile drag to increase resulting in an increased total drag and VIMD, the velocity of minumum
drag. The angle of attack affects the value of . With a low angle of attack, the drag is mostly
profile and will reduce but with high angles of attack, the drag is mostly induced, resulting in a
high . Its value will continue to increase up to the stalling angle at which point it will suddenly
reduce.
7. The angle of attack also affects the forward speed or vice versa. If the lift formula is toremain balanced, a low IAS requires a high angle of attack and a high IAS needs a low angle ofattack. Should the V in the formula be IAS then, for level flight, the angle of attack will be the sameat all altitudes provided the IAS remains constant, because lift and drag will be unchanged.However, if the V is a TAS, then in a normal atmosphere, the TAS will increase up to the tropopausefor a given IAS.
CL
1/2V2 CL IAS wing area
CL
CL
CL
CL

Basic Aerodynamics
8. Climbing at a constant IAS will therefore require the angle of attack to be maintainedthroughout the climb. However, if the climb is conducted at a constant Mach number, then both theIAS and TAS will reduce in a normal atmosphere and it is then necessary to increase the angle ofattack.
9. For a given angle of attack, the IAS changes in direct proportion to the square root of theweight of the aeroplane.
10. In a descent at constant Mach no., the TAS and IAS increase in a normal atmosphere and inthe angle of attack must be decreased progressively with altitude which wil

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