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Uncontrolled copy not subject to amendment Principles of Flight Principles of Flight Learning Outcome 2: Understand how the stability of an aeroplane is maintained in flight and how manoeuvrability is controlled Part 1 Principles of Flight A Ship C Tower A Bourne H Copter B Loons R Way Dan Winterland S Huttle I Flyum Revision Questions What is the force called that drives an aircraft forwards? Lift Weight Drag Thrust Questions What is the force called that resists the forward motion of an aircraft? Lift Weight Drag Thrust Questions If your speed is doubled, by how much would the Drag be increased? x2 x4 x6 x8 Questions If Thrust = Drag and Lift = Weight then the aircraft is: Climbing Flying Straight & Level and Accelerating Flying Straight & Level an Decelerating Flying Straight & Level at Constant Speed Stability Objectives: 1. Identify the Axes of Rotation for an Aircraft. 2. Identify the Planes of Movement for an Aircraft. 3. Describe and Explain Stability in the 3 Planes of Movement. 4. Explain Dihedral and Anhedral and how they affect Stability. OW!! Stability What would happen to this dart when thrown? What would happen now? Something is needed to “Stabilise” the Dart (Aircraft). Stability Airflow Centre of Gravity (CG) Airflow ‘Body’ Ahead of CG is Destabilising. ‘Body’ Behind CG is Stabilising. Basic Stability Stable Unstable Neutral Basic Stability Stable Forms of stability •Static •Dynamic - initial reaction - subsequent reaction Basic Stability Stable Forms of stability •Static •Dynamic - initial reaction - subsequent reaction Basic Stability Stable Forms of stability •Static •Dynamic - initial reaction - subsequent reaction Basic Stability Stable Forms of stability •Static •Dynamic - initial reaction - subsequent reaction Basic Stability Stable Forms of stability •Static •Dynamic - initial reaction - subsequent reaction Application to Aircraft Static Stability Unstable Neutral Stable Application to Aircraft Statically Stable Dynamic Stability Dynamically Neutral Dynamically Unstable Dynamically Stable Planes of Stabilisation Pitch (Longitudinal) Yaw (Directional) Longitudinal Axis Roll (Lateral) Lateral Axis Normal Axis Stabilisation Axis Longitudinal Plane Stability Rolling Lateral Stability Stabilisation Axis Plane Stability Longitudinal Rolling Lateral Lateral Pitching Longitudinal Stability Stabilisation Axis Plane Stability Longitudinal Rolling Lateral Lateral Pitching Longitudinal Normal Yawing Directional Stability Directional Stability Directional Stability Stabilising Influence of fin: 1. Value of Lift 2. Moment Arm CG Flight Path Lift Enhancement features: A large finSomething and/or a long moment arm to yaw causes the aircraft CofG Considerations An aft CofG requires a large Fin The strange case of the ever growing fins MOD Longitudinal Stability Longitudinal Stability Lift Flight Path Weight To explain this stability, we assume that the CP and CG are coincident. Longitudinal Stability Lift Lift Flight Path Weight Something causes the nose to rise Lift wings - Destabilising Stabilising influence of Tailplane: Lift tailplane - Stabilising Area x Moment Arm = Tail Volume Lateral Stability Lateral Stability Lift Resultant Sideslip Weight Lateral Stability Hdg Aircraft sideslips in this direction All design features for lateral stability rely on the fact that bank results in sideslip Lateral Stability Methods 1. Large Fin of high aspect ratio (a big tall fin). Lift from fin rolls wings level Lateral Stability Methods 2. Dihedral: Due to new direction of relative airflow – lower wing has higher AoA than upper - more lift - tends to roll wings level. Lift Lateral Stability Methods 3. Sweepback Span More Chord Less Aspect Ratio Lift Higher Less More Lower More Less LOW WING Lateral Stability Methods 4. High wing Less Lift More Lift Air flow near wing roots affected by fuselage - Increases AoA on Low Wing -Decreases AoA on High Wing Relative Airflow Lateral Stability Methods 1. High Fin. 2. Dihedral. 3. Sweepback. 4. High Mounted Wing But too much Lateral Stability (High wing and Sweepback) very undesirable in fighter aircraft. Therefore anhedral to reduce the excess Any Questions? Stability Objectives: 1. Identify the Axes of Rotation for an Aircraft. 2. Identify the Planes of Movement for an Aircraft. 3. Describe and Explain Stability in the 3 Planes of Movement. 4. Explain Dihedral and Anhedral and how they affect Stability. Questions What are the 3 planes of an aircraft’s movement? a. Pitching, Lateral and Rolling. b. Pitching, Rolling and Yawing. c. Yawing, Longitudinal and Rolling. d. Longitudinal, Lateral and Normal. Questions Which one of the following will REDUCE Lateral Stability? Dihedral. A Large Fin. Sweepback. Anhedral. Questions What are the 3 Axes about which an Aircraft can move? a. Pitching, Lateral and Longitudinal. b. Pitching, Rolling and Yawing. c. Yawing, Longitudinal and Normal. d. Longitudinal, Lateral and Normal. Questions Which 3 Terms describe Static Stability? a. Stable, Neutral and Unstable. b. Stable, Rolling and Unstable. c. Yawing, Neutral and Stable. d. Neutral, Unstable and Pitching.