FLIGHT CONTROLS MENU Normal law 1/36 FLIGHT CONTROLS MENU Normal law 2/36 For clarity in this module most references will be made to manual flight inputs. However, the references apply equally to automatic flight unless stated otherwise. In this module, we will be looking at how an A320 pilot and the aircraft computers interface to ensure safe and accurate flight with minimum workload for the crew. FLIGHT CONTROLS MENU Normal law 3/36 FLIGHT CONTROL COMPUTERS A side stick or an autopilot sends a message to the flight control computers demanding an aircraft maneuver. FLIGHT CONTROLS MENU Normal law 4/36 FLIGHT CONTROL COMPUTERS CONTROL SURFACES The flight control computers process the demand and send it to the control surfaces. The processing uses pre-set limitations and instructions called LAWS. FLIGHT CONTROLS MENU Normal law 5/36 AIRCRAFT RESPONSE TO SURFACE MOVEMENT CONTROL SURFACES FLIGHT CONTROL COMPUTERS The aircraft responds conventionally to the movement of control surfaces. FLIGHT CONTROLS MENU Normal law 6/36 Ground mode Ground mode Flight mode Flare mode Normal Law is modified depending on the phase of flight. It operates in 3 modes: Ground mode: • Operates on the ground when the aircraft is electrically and hydraulically powered. Controls are conventional. Flight mode: • Operates in the air after a gradual transition from ground mode just after lift off, • Will be discussed in detail as this module continues. Flare mode: • Modifies Flight Mode to introduce a conventional ‘feel’ to the landing phase. • Will be discussed later in this module. We will compare a conventional aircraft, an A310, with the fly by wire A320 in Normal law flight mode. FLIGHT CONTROLS MENU Normal law 7/36 Coonnvveennttiioonnaall aaiirrccrraafftt • Control surface deflection is directly proportional to control yoke deflection. • The same yoke input produces a: - Higher rate of pitch/roll at high speed, - Lower rate of pitch /roll at low speed. FLIGHT CONTROLS MENU Normal law 8/36 • Control surface deflection is not directly proportional to side stick deflection. • A side stick deflection gives a rate demand to the Flight control computers. • The Flight control computers set control surface deflection to meet the rate demand. For the same side stick input, the control surface deflections will be: - Large at low speed, but - Small at high speed. • A side stick input is a : - Rate of roll demand in roll, - Load factor (g) demand in pitch. • Yaw control is conventional. FFllyy bbyywiirree aaiirrccrraafftt Coonnvveennttiioonnaall aaiirrccrraafftt • Control surface deflection is directly proportional to control yoke deflection. • The same yoke input produces a: - Higher rate of pitch/roll at high speed, - Lower rate of pitch /roll at low speed. FLIGHT CONTROLS MENU Normal law 9/36 AIRCRAFT RESPONSE TO SURFACE MOVEMENT CONTROL SURFACES FLIGHT CONTROL COMPUTERS Remember, the A320 responds conventionally to the movement of control surfaces. However, unconventionally, the response information is fed back to the flight control computers. FLIGHT CONTROLS MENU Normal law 10/36 AIRCRAFT RESPONSE TO SURFACE MOVEMENT CONTROL SURFACES FLIGHT CONTROL COMPUTERS The computers process this feedback and adjust control surface deflection to ensure that the maneuver rate demand is executed accurately. This means that control surface deflections may be altered with no change in side stick position. FLIGHT CONTROLS MENU Normal law 11/36 FLIGHT CONTROLS MENU Normal law 12/36 In flight mode, if you wish to execute, for example, a descending left turn, you set the required attitude and then return the side stick to neutral. The neutral side stick position demands zero rates of pitch and roll. The flight control computers will maintain the set attitude until you use the side stick to demand an attitude change. Throughout the maneuver, there are no pilot trim inputs. FLIGHT CONTROLS MENU Normal law 13/36 Turn co-ordination and “Dutch roll” damping are automatically provided in Normal law.Pilot inputs on the rudder pedals are not required. FLIGHT CONTROLS MENU Normal law 14/36 Normal law provides a number of airborne pitch protections. They are: • Maneuver protection, FLIGHT CONTROLS MENU Normal law 15/36 •• Piittcchh aattttiittuuddee pprrootteeccttiioonn,, Pitch up limit Pitch down limit Normal law provides a number of airborne pitch protections. They are: • Maneuver protection, FLIGHT CONTROLS MENU Normal law 16/36 •• Piittcchh aattttiittuuddee pprrootteeccttiioonn,, •• Hiigghh aannggllee ooff aattttaacckk pprrootteeccttiioonn,, AIR FLOW Normal law provides a number of airborne pitch protections. They are: • Maneuver protection, FLIGHT CONTROLS MENU Normal law 17/36 •• Piittcchh aattttiittuuddee pprrootteeccttiioonn,, •• Hiigghh aannggllee ooff aattttaacckk pprrootteeccttiioonn,, •• Hiigghh ssppeeeedd pprrootteeccttiioonn.. Normal law provides a number of airborne pitch protections. They are: • Maneuver protection, FLIGHT CONTROLS MENU Normal law 18/36 In lateral control, there is only one protection which is for bank angle. Let’s take a closer look at these protections. FLIGHT CONTROLS MENU Normal law 19/36 MANEUVER PROTECTION In a conventional aircraft, pilots must insure that structural limitations are not exceeded. However, in the A320 family, Maneuver protection is available in Normal law. FLIGHT CONTROLS MENU Normal law 20/36 MANEUVER PROTECTION Maneuver protection prevents structural overstress by limiting control surface deflections through the flight control computers. Full side stick movement is always available. The structural limitations vary with configuration: • In clean configuration, between +2.5 g to -1 g, • Flaps extended, between +2 g to 0 g. FLIGHT CONTROL COMPUTERS FLIGHT CONTROLS MENU Normal law 21/36 PITCH ATTITUDE PROTECTION As with the Maneuver protection, if the aircraft reaches the Pitch attitude protection nose up limits, then the flight control computers will override pilot demands and keep the aircraft within the safe flight limits. The Pitch attitude protection limits are shown as small green dashes on the PFD. Note that the pitch up values vary depending on the aircraft configuration and speed between 30 and 20 degrees up. FLIGHT CONTROL COMPUTERS Pitch up limit FLIGHT CONTROLS MENU Normal law 22/36 PITCH ATTITUDE PROTECTION In the nose down case, the computers will limit the nose down attitude at 15 degrees. FLIGHT CONTROL COMPUTERS Pitch down limit FLIGHT CONTROLS MENU Normal law 23/36 HIGH ANGLE OF ATTACK PROTECTION High angle of attack limits The High angle of attack protection is designed to prevent the aircraft from stalling and to ensure optimum performance in extreme maneuver such as windshear or GPWS warning recovery. This protection takes priority over all others. This protection displays information against the PFD speed scale. AIR FLOW FLIGHT CONTROLS MENU Normal law 24/36 HIGH ANGLE OF ATTACK PROTECTION As speed decreases it reaches Vls, lowest achievable speed with autothrust engaged. With autothrust inoperative or not engaged, the speed can reduce to the first level of Angle of attack protection, V alpha prot which is shown as the top of the amber/black band (barber pole). The Flight control computers will maintain the speed at V alpha prot. If engaged, the autopilot will disconnect. Vls V PROT FLIGHT CONTROLS MENU Normal law 25/36 HIGH ANGLE OF ATTACK PROTECTION If the pilots override V alpha prot using the side stick, the speed can reduce to V alpha max. In Normal law, the flight control computers will maintain V alpha max, even if a pilot holds a side stick fully aft. Nose up pitch trim is inhibited. In the protection range, the Normal law demand is modified and side stick input is an Angle of attack demand, instead of a load factor demand. V MAX FLIGHT CONTROLS MENU Normal law 26/36 HIGH ANGLE OF ATTACK PROTECTION Provided the autothrust is serviceable, the speed is unlikely to reduce to V alpha max before the Alpha floor protection is triggered. This is indicated by an “A FLOOR” indication on the PFD FMA and also on the E/WD. FLIGHT CONTROLS MENU Normal law 27/36 HIGH ANGLE OF ATTACK PROTECTION If the pilot releases the side stick at V alpha max, the speed will return to, and maintain V alpha prot. VVMRAOXT FLIGHT CONTROLS MENU Normal law 28/36 HIGH SPEED PROTECTION High speed limits The protection we will look at now is the High speed protection. It is designed to prevent the aircraft from exceeding maximum speed. This protection limits are displayed on the PFD speed scale. FLIGHT CONTROLS MENU Normal law 29/36 HIGH SPEED PROTECTION VMO/MMO is shown as the bottom of the red/black barber pole. Green dashes indicate the speed at which the protection is activated. Protection VMO MMO FLIGHT CONTROLS MENU Normal law 30/36 HIGH SPEED PROTECTION When the airspeed/Mach increases above VMO/MMO, an overspeed ECAM warning is triggered, as shown in the Autoflight chapter. FLIGHT CONTROLS MENU Normal law 31/36 HIGH SPEED PROTECTION If the airspeed/Mach increases to the protection speed, the autopilot will disengage and the flight control computers send a pitch up command to the control surfaces to prevent further acceleration. The flight control computers will permit momentary exceedance of this speed for maneuvering if necessary, but will then return to the protection speed. FLIGHT CONTROLS MENU Normal law 32/36 HIGH SPEED PROTECTION Notice that the pilot cannot override the automatic pitch up . FLIGHT CONTROLS MENU Normal law 33/36 BANK ANGLE PROTECTION Bank angle limits Under Normal law, Bank angle protection limits the angle of bank to 67 degrees, shown by green dashes on the PFD. FLIGHT CONTROLS MENU Normal law 34/36 BANK ANGLE PROTECTION If the pilot holds full lateral side stick, angle of bank will increase and maintain 67 degrees. The flight director (FD) on the PFD will disappear if the angle of bank exceed 45 degrees. Max bank angle FLIGHT CONTROLS MENU Normal law 35/36 BANK ANGLE PROTECTION If the side stick is released at any time when the bank angle exceeds 33 degrees, the aircraft will return to and maintain 33 degrees bank angle. The FD will de displayed again on the PFD when the angle of bank reduces to less than 45 degrees. Autotrim is inhibited above 33 degrees. 33º bank angle FLIGHT CONTROLS MENU Normal law 36/36 BANK ANGLE PROTECTION Note, if High speed or Angle of attack protections are active, angle of bank is limited to 45 degrees and the aircraft will return to wings level if the side stick is released. We will now study the reconfiguration laws in the next module. NEXT Module completed FLIGHT CONTROLS MENU Normal law 37/36 HHIIGGHHAANNGGLLEEOOFFAATTTTAACCKKPPRROOTT.. LLIISSTTOOFFSSUUBBJJEECCTTSS EXIT AUDIO GLOSSARY FCOM RETURN PPRRIINNCCIIPPLLEESS PPIITTCCHHAATTTTIITTUUDDEEPPRROOTTEECCTTIIOONN HHIIGGHHSSPPEEEEDDPPRROOTTEECCTTIIOONN MMAANNEEUUVVEERRPPRROOTTEECCTTIIOONN BBAANNKKAANNGGLLEEPPRROOTTEECCTTIIOONN NNOORRMMAALLLLAAWW作者: show616 时间: 2011-4-22 11:50:08
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