RMIT飞行训练课件－Stalling RMIT 飞行训练失速课件

航空发表于 2010-7-30 15:20:43

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航空发表于 2010-7-30 15:21:09

RMIT Flight Training Stalling RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 1 Brief 8 STALLING Aim: To learn the principles and considerations of an aircraft approaching a stall, to recognize the symptoms, and how to correctly recover with a minimum of height loss. Application: - Inadvertent stall recovery, high AoA / low IAS operations such as take-off and landing. Revision:  Aerofoil and Lift  Drag  Lift Distribution A S I A O A Relative airflow Angle of attack Chordline Slow Fast DRAG AIRSPEED Induced Drag Parasite drag Minimum Drag TOTAL DRAG Best L/D Ratio Pressure distribution + _ Aerodynamic Force Centre of pressure RMIT Flight Training Stalling RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 2 Brief 8 Definitions:  Critical Angle - The AoA where the CL (the lifting ability of the wing) is at a maximum; beyond that CL decreases markedly.  Stall - Occurs when the AoA exceeds the critical angle.  Stall Speed (VS ) - The speed at which the aircraft stalls in the following configuration:- MTOW @ mean sea level, idle power, straight and level altitude and the most forward CoG position.  Streamline Airflow - Smooth airflow that remains attached to the surface of the aerofoil.  Turbulent Airflow - Airflow that cannot remain attached to the aerofoil, creating drag.  Separation Point - Where the streamline airflow becomes turbulent airflow.  Boundary Layer - The closest layers of air to the surface of the aerofoil which have reducing velocities due to both the skin friction and the viscosity of the air. It is initially laminar then transitions to become turbulent.  Transition Region - Where the laminar boundary layer becomes a turbulent boundary layer.  Stagnation Point - Point on the aerofoil where the airflow comes to rest relative to the aerofoil. Normally occurs at the LE and the TE.  Load Factor - LF = L/W, measured in ‘g’ numbers. AoA CL RMIT Flight Training Stalling RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 3 Brief 8 Principles: Let’s take a closer look at an aerofoil at varying AoA’s:  4 AoA - Airflow is streamlined with the transition and separation occurring well aft. Referring to the pilot’s lift formula, most of the lift produced is due to high airspeed, whilst only a small amount is due to the AoA.  8 AoA - With the increased AoA comes a further decrease in Pstatic over the leading section of the aerofoil. Hence the average pressure moves forward (acting through the CoP), thereby causing an earlier transition region and separation point.  16 AoA - At the critical AoA, the lift produced due to the AoA is a maximum and the CoP is the furthest forward. This causes even earlier separation, creating more drag and an adverse pressure gradient towards the trailing edge.  16 AoA - Whilst the aerofoil is still creating some lift, but is insufficient to sustain the weight. Most of the airflow is turbulent with a rearwards shift in CoP position, causing a nose drop and loss of altitude IAS IAS IAS IAS CL CL CL CL L L L L W W W W 110kt 4o 70kt 8o 44kt 16o <44kt >16o IAS AoA RMIT Flight Training Stalling RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 4 Brief 8 RMIT Flight Training Stalling RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 5 Brief 8 The stall AoA can be associated with a particular airspeed, since we can’t directly read AoA (Performance = Power + Attitude): VS0 = 33KIAS (full flap) VS1 = 44KIAS (clean) Usual Symptoms: 1. High nose attitude 2. Low IAS 3. Reduced control effectiveness 4. Stall warning 5. Control buffet Considerations:  Manoeuvres - When pulling out of a dive, applied back pressure,  AoA,  L hence LF. - The stall speed in a manoeuvre can be calculated using VNS = VS  LF - In addition to that, the load factor in a turn can be calculated using LF = 1 / Cos(AoB) eg. In a steep turn: AoB = 60  LF = 2g so, VNS = 62KIAS A stall occurs at an AoA, not an IAS Actual Stalled Flightpath Attempted 3G Pullout Planned Flightpath Increased Stall Speed 1G 2G 3G 4G 2.0 1.8 1.6 1.4 1.2 1.0 “g” load RMIT Flight Training Stalling RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 6 Brief 8  Weight - As weight increases, lift must also increase. When both aircraft achieve the critical angle the heavy aircraft must fly at increased IAS to produce the additional lift required.  CoG - Forward movement of the CoG will increase the strength of the nosedown couple between lift and weight as a result increase the amount of downforce required on the tailplane - In effect this increase of downforce is similar to an increase in weight and therefore a forward CoG will lead to an increased stall speed.  Ice - Ice disturbs the streamline airflow causing earlier separation. - Also  W, which requires  L hence  VS. L L W W 16o 16o 40 kt 44 kt RMIT Flight Training Stalling RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 7 Brief 8  Flap - Lowering flap increases the aerofoil’s camber and AoA for the same attitude. Therefore at the same AoA (ie. critical angle) the flaps allow the aircraft to fly at  IAS with a lower nose attitude. - With flap, more lift is generated on the inboard portions of wing (closer to CoG), reducing lateral stability and becoming more susceptible to a wingdrop.  Power - Slipstream re-energises the airflow over the inboard sections of the wing, delaying separation. Also the vertical component of thrust assists in counteracting the weight. - Like flaps, the wingtip may stall first (due less airflow) causing a wingdrop.  Stability in the Stall - Reduces the angle of incidence on wingtip compared to the wing root. - Ensures the wing root stalls first providing control buffet on the elevator and a more stable stall. 16o 16o Relative Airflow High Nose Attitude Lower Nose Attitude Thrust TH TV Smaller AoA Relative Larger AoA Airflow Cross-Section at Wing Tip Cross-Section at Wing Tip RMIT Flight Training Stalling RMIT Instructor Rating Mass Briefs Issue 1 /2004 Page 8 Brief 8 Air Exercise:  Pre-Stalling Checks - Height sufficient to recover by 3000ft - Hatches/Harnesses secure. - Engine Temperature & Pressure. - Location – not above a populated area. - Loose articles secure. - Lookout (360 turn)  Entry - Pick a reference point (maintain with rudder not ailerons) - Retard throttle, maintaining height. - Note previously discussed symptoms.  Stall - Nose pitches down. - Note height loss  Recovery - Lower nose to horizon. - Speed increases through 65KIAS, full power. - Climb out.  Wing Drop Recovery - Apply opposite rudder to stop yaw. - Lower nose to unstall attitude. - Passing 65KIAS, full power. - Climb out. Airmanship: - INADVERTANT STALLS SHOULD NEVER OCCUR! - Lookout (conduct 90 turn after each stall). - Smooth co-ordinated control input – especially during recovery. - Correct Handover/Takeover procedure. - Monitor engine gauges.

cdzfk 发表于 2010-9-21 09:41:22

谢谢分享了。不错，收藏了

colgategaowj 发表于 2010-10-5 20:04:29

kankan ~~~

猪也能飞 发表于 2013-10-28 19:11:06

感谢楼主万分感谢感谢万分

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RMIT飞行训练课件－Stalling RMIT 飞行训练失速课件