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1、2,Airline Transition Course,ATP Chapter 5 Aerodynamics and Flight Characteristics,3,First of all - what is aero? What is aeronautics? What is the difference between aircraft after V1, takeoff must be continued. For safety considerations, V1 VMCG, since at and after V1, the airplane is committed to t
2、ake off.,65,Takeoff Profile Segments,Runway,1,2,Grnd Roll,Vr,35ft,Acceleration,1500ft,Final,2nd Segment: from 35 AGL to 400 AGL. V2 is maintained during this segment, called the 2nd segment, since it is the second airborne segment. Adequate climb capability in this segment requires a 3.0% climb grad
3、ient (30 altitude per 1000 of horizontal distance) with 3 out of 4 engines operating. a 2.7% climb gradient (27 altitude per 1000 of horizontal distance) with 2 out of 3 engines operating. a 2.4% climb gradient (24 altitude per 1000 of horizontal distance) with 1 out of two 2 engines operating.,400f
4、t,66,V2Takeoff Safety Speed,FAR 25 Definition: the speed after takeoff that gives an adequate climb angle (adequate climb capability) from 35 AGL to 400 AGL with an engine inoperative. For large swept wing jet transport airplanes (but not for light twins), V2 is typically less than VXSE or VYSE. V2
5、must be at least 1.2 VS (1.15 VS for some airplanes) for takeoff flaps setting, and at least 1.10 VMCA.,67,Takeoff Profile Segments,Runway,1,2,Grnd Roll,Vr,35ft,Acceleration,1500ft,Final,400ft,Acceleration Segment; sometimes subdivided into 3rd and 4th Segments): segment where airplane accelerates f
6、rom V2 to 1.25 Vs (clean) at 400 AGL. The 3rd Segment ends when flaps are retracted. The 4th segment ends when the first throttle reduction occurs.,68,Takeoff Profile Segments,Final Segment; also sometimes called the 5th Segment: clean configuration climb from 400 AGL to 1500 AGL at a speed no lower
7、 than 1.25 Vs. Adequate climb capability in this segment requires: a 1.7% climb gradient (17 altitude per 1000 of horizontal distance) with 3 out of 4 engines operating. a 1.5% climb gradient (15 altitude per 1000 of horizontal distance) with 2 out of 3 engines operating. a 1.2% climb gradient (12 a
8、ltitude per 1000 of horizontal distance) with 1 out of 2 engines operating.,69,Factors Affecting: Vr,VR 1.10 VMU (minimum unstuck speed), or VR 1.05 Vmu (engine out minimum unstuck speed) to avoid getting airborne at a speed where the airplane probably will not fly out of ground effect. VR 1.05 VMCA
9、, to preclude inadvertent loss of control. VR V1, for safety reasons. Abort after rotate is a risky undertaking.,70,VMUMinimum Unstick Speed,VMU - slowest airspeed where the airplane can be forced off the ground with all engines operating. At this speed, the airplane will fly in ground effect but st
10、all out of ground effect and the settle back toward the ground. Vmu - slowest airspeed where the airplane can be forced off the ground with one engine inoperative,71,VMCMinimum Control Speeds,VMC minimum control speed due to asymmetrical thrust with one engine inoperative. This speed is subdivided i
11、nto: VMCG minimum control speed during takeoff ground roll with the nose wheel still on the ground. VMCA minimum control speed in the air or on the ground with the nose wheel off the ground after rotation for takeoff.,72,Accelerate-GoandAccelerate-Stop,accelerate-go distance distance an airplane use
12、s to accelerate to V1, experience a critical engine failure, then continue accelerating, lift off, and achieve an altitude of 35 AGL. accelerate-stop distance distance an airplane uses to accelerate to V1, then decelerate to a stop using only brakes and spoilers.,73,Balanced Field Length,Balanced fi
13、eld length is the runway length where, for a given gross weight, elevation, and takeoff configuration, accelerate-stop distance and accelerate-go distance are the same . if an engine failure occurs prior to V1, the aircraft will have adequate runway remaining to stop when an abort is initiated. If a
14、n engine failure occurs at or above V1, the aircraft will achieve 35AGL by the end of the runway if the takeoff is continued. Contd,74,Balanced Field Length,Balanced field length is the runway length where, for a given gross weight, elevation, and takeoff configuration, accelerate-stop distance and
15、accelerate-go distance are the same . if an abort is initiated after V1, the aircraft will overrun the runway. if an engine failure occurs prior to V1 and takeoff is continued, the aircraft will not achieve 35 AGL by the end of the runway .,75,An airplane should never attempt to depart from a runway
16、 shorter than the balanced field length for its particular gross weight, elevation, and takeoff configuration, since a decision to abort just below V1 will result in runway overrun. a decision to continue just above V1 will result in achieving less than 35 AGL by the end of the runway. If V1 is chan
17、ged from the V1 corresponding to balanced field length, the runway length to depart safely increases, since when V1 decreases, accelerate-go distance increases, and takeoff commitment occurs at V1. When V1 increases, accelerate-stop distance increases, and a commitment to abort exists below V1. The
18、balanced field length concept ordinarily should be used to determine decision speed V1.,76,Factors AffectingV1 and Balanced Field Length,slippery runway a slippery runway is one where poor braking action (rain, freezing rain, very light ice or packed snow) increases accelerate-stop distance but not
19、accelerate-go distance. An increase in balanced field length will occur as a result. V1 must be decreased to allow a greater abort rollout. VR and V2 remain unchanged. cluttered runway a cluttered runway is one where precipitation on the runway increases accelerate-go distance but not accelerate-sto
20、p distance. Balanced field length will increase, as will V1, because it takes longer to achieve a ground speed compatible with reaching V2 and 35 AGL by the end of the runway.,77,Critical Engine,The critical engine of a twin engine airplane is the one with the center of thrust closest to the center
21、line of the fuselage.,78,In the picture to the left the critical engine has failed. The pilot notices that the aircraft is yawing to the left. He/she will respond by applying right rudder. The amount of rudder applied must be just enough to produce a yawing moment from the tail which is equal but op
22、posite to the one produced by the right engine. Once the correct amount of rudder has been applied the aircraft will stop yawing.,79,Airworthiness manual 523.149 states: Vmc is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control
23、 of the airplane with that engine still inoperative and then maintain straight flight at the same speed with an angle of bank of not more than 5 degrees. The ability to maintain straight and level flight at Vmc in a static condition with bank angle of not more than 5 degrees must also be demonstrate
24、d. The Airworthiness manual also goes on the specify the following conditions for Vmc.,80,Vmc may not exceed 1.2 Vs1 determined at the maximum take-off weight Maximum available take-off power or thrust on the engines The most unfavorable center of gravity The airplane trimmed for takeoff The maximum
25、 sea level takeoff weight or any lesser weight necessary to show Vmc The most critical takeoff configuration with landing gear retracted The airplane airborne but not in ground effect The inoperative engine wind milling unless an auto feather system is installed,81,Vmc and Altitude,Vmc decreases wit
26、h altitude on airplanes without supercharged engines.,82,Question,What effect, if any, does altitude have on Vmc for a normally aspirated airplane? None Increases with altitude Decreases with altitude,83,Answer,What effect, if any, does altitude have on Vmc for a normally aspirated airplane? C. Decr
27、eases with altitude,84,High Altitude Flight,Why so high? Benefits and Drawbacks of High Altitude flying Airspeed Review Standard Atmosphere Temperature Pressure Density,85,High Altitude is Hazardous,Cold Low Pressure Low Mach Why go high? TAS,86,Know,Indicated Read off the Airspeed Indicator Calibra
28、ted Indicated corrected for position and installation error Equivalent Calibrated corrected for compressibility effect True Equivalent corrected for air density,87,Why so high?,True Airspeed,88,Questions?,89,High Speed Flight,Mach Mach Number Categories of Mach Numbers Compressibility Mach Considera
29、tions Shockwaves Mach Tuck High Speed Buffet Coffin Corner Operating Envelopes,90,What is Mach?,Mach is the ratio of the speed of sound to the speed the aircraft is moving. Mach is proportional to temperature.,91,Mach Number,Ratio of the aircrafts airspeed to the speed of sound in the current condit
30、ions. Example: A/S 600 KEAS Speed of sound 750 knots Mach Number: 600/750=0.8 80% of the speed of sound,92,Categories of Mach Numbers,Subsonic Flight All airflow is subsonic. Mach 0 to 0.75 Transonic Flight Some airflow is supersonic, some is subsonic Mach 0.75 to 1.2 Supersonic Flight All airflow i
31、s supersonic Above Mach 1.2,93,Compressibility,Air is incompressible. FALSE At high airspeed air IS compressible. Air does not have time to get out of the way. Air piles up.,94,Shock Waves,The maximum speed of a pressure wave is the speed of sound. In subsonic flight pressure waves radiate out. Once
32、 the speed of sound is reached these waves can no longer get out of the way and build up.,95,Shock Waves,The air forward of the shock wave has different characteristics than the surrounding air. Increased Temperature Increased Pressure Increased Density,96,At sea level a plane must exceed 741 mph to
33、 break the sound barrier, or the speed at which sound travels. The change in pressure as the plane outruns all of the pressure and sound waves in front of it is heard on the ground as an explosion or sonic boom. The pressure change condenses the water in the air as the jet passes these waves. Altitu
34、de, wind speed, humidity, the shape and trajectory of the plane - all of these affect the breaking of this barrier.,97,98,99,Shock Waves,The air behind a shock wave has the following characteristics: Cooler than in front of the shock wave Low pressure Low density,100,TAT and SAT,TAT=Total Air Temper
35、ature. Shows the temperature as read by the temperature probe. This temperature will be higher than static air temperature due to compressibility. SAT=Static Air Temperature. TAT corrected for compressibility. Outside Air Temperature.,101,Mach Tuck,In subsonic flight the center of pressure of the wi
36、ng lies at 25% MAC In transonic and supersonic flight the center of pressure moves to 50% MAC This is caused by airflow separation behind the shock wave. When transitioning into transonic flight the airplane will pitch down. As airspeed increases the aircraft will continue to pitch down.,102,Swept W
37、ings in Supersonic Flight,Swept wings are the second option an aircraft designer has to minimize the drag caused by the bow wave. Earlier we learned that swept wings raise the critical mach number thus making modern airliners more efficient at high subsonic speeds. Now we will see that even more swe
38、ep will reduce the effect of the bow wave in supersonic flight.,103,Swept Wings in Supersonic Flight,Every part of the airplane which strikes the airflow and slows it to subsonic speeds will produce a shock wave (the bow wave.) This shock wave will sweep back at an angle known as the mach angle (The
39、 mach angle is simply 1/Sin(M) where M is the Mach number of the aircraft. IE, an aircraft flying at mach 2 will produce shock waves which trail back at a 30 degree angle.) These are of course Oblique shock waves.,104,Swept Wings in Supersonic Flight,Airflow behind an Oblique shock wave is still sup
40、ersonic. although it is slowed down. However, the component of the airflow at flight angles to the Oblique shock wave will always be subsonic. This concept is shown in the diagram to the left, if a wing is placed behind the shock wave as shown above, then the air flowing at right angles over that wi
41、ng will be .,105,Swept Wings in Supersonic Flight,subsonic, even though the aircraft is flying faster than the speed of sound. Therefore, a subsonic airfoil, with round leading edges can be used without creating a bow wave.,106,Question,What is the result of a shock induced separation of airflow occ
42、urring symmetrically near the wing root of a swept wing aircraft? A high speed stall and sudden pitch up. A severe moment or “tuck under” Severe proposing.,107,Answer,What is the result of a shock induced separation of airflow occurring symmetrically near the wing root of a swept wing aircraft? A se
43、vere moment or “tuck under”,108,CG Compensation,Supersonic aircraft compensate for the center of pressure moving aft by moving the CG aft. The Concorde, for instance, pumps fuel from the forward tank to the aft tank to compensate.,109,High Speed Buffet,The air behind a shock wave is turbulent The di
44、sturbed air affects the horizontal stabilizer which causes it to buffet Feels like a stall buffet What happens if the pilot reacts with a stall recovery and not a high speed recovery?,110,Coffin Corner,Does stall speed change with altitude? NO Indicated stall speed remains constant. Does Mach change
45、 with altitude? YES Mach decreases with altitude.,111,Coffin Corner,At coffin corner you will either experience high speed or stall buffet. If you attempt to recover from a high speed condition you will stall the aircraft. If you attempt to recover from a low speed condition you will overspeed the a
46、ircraft.,112,Altitude Capability,113,Maneuver Capability,114,Know,Critical Mach Number (Mcrit) is the Mach number at which supersonic flow begins to form on the aircraft. Maximum operating speed is referred to as Mmo, (Mach Max Operating.) Limiting Mach Number is the highest speed the aircraft can o
47、perate before becoming uncontrollable.,115,Swept WingsWhy we do it.,Swept wings create less drag than a comparable straight wing. Increases lateral stability, about the vertical axis. Increases Mcrit,116,Swept WingsNot all good,A swept wing stalls near the tip unless aerodynamic twist is employed Du
48、tch roll can be prevalent The aircraft tends to roll opposite the direction of yaw.,117,Questions?,118,Flight Controls,Ailerons Trim Tabs Control Tab Elevator Trim Tab Servo Tab Anti-Servo Tab Wing Altering Devices Flaps Slats Yaw Damper,119,Ailerons,Some jet transports use both inboard and outboard
49、 ailerons. Outboard ailerons are used at low airspeeds for roll control. This is due to a greater moment arm between the aileron and center of gravity. At high airspeeds aerodynamic forces are too great to use outboard ailerons. Inboard ailerons are used for both low speed and high speed flight.,120
50、,Ailerons,When are outboard ailerons normally used? Low speed flight High speed flight All speeds,121,Ailerons,When are outboard ailerons normally used? Low speed flight,122,Trim TabsControl Tabs,Control Tab used on some transport aircraft as a manual backup. It is a small tab on a larger flight control. It moves to force the larger flight control to move. Used in emergency. Called Manual Reversion.,123,Trim TabsElevator Trim Tab,Elevator Trim Tab used to reduce or eliminate flight control pressure.,124,Trim T
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