FLIGHT CONTROLS MENU Reconfiguration Laws 1/29 FLIGHT CONTROLS MENU Reconfiguration Laws 2/29 A single failure can not result in the loss of Normal law. However, multiple failures of flight control, hydraulic, or electrical systems may result in a degradation of the flight control law. The level of degradation will depend on the severity of the failures. Degradation of the flight control laws is sometimes referred to as reconfiguration. We will study these degraded laws in order of increasing severity. FLIGHT CONTROLS MENU Reconfiguration Laws 3/29 Ground mode Ground mode In Alternate law: Ground mode is as in Normal law. Flight mode: • Pitch control: load factor demand as in Normal law. • Roll control: conventional, surface deflection is proportional to side stick deflection, - Roll sensitivity is proportional to airspeed, - Feels more sensitive. • Yaw control: turn coordination is lost, - Damping available with limited authority. Landing mode: Direct law when landing gear is selected down (discussed later). DDiirreecctt llaawwaattLL//GGddoowwnn Flight mode Flare mode Conventional control in roll & alternate in yaw FLIGHT CONTROLS MENU Reconfiguration Laws 4/29 Degradation to alternate law is indicated by the ECAM caution F/CTL ALTN LAW (PROT LOST). You will see this caution in detail in the abnormal operation module. Under alternate law, most protections are lost. Some are replaced by stabilities. We will continue by studying the loss of protections. FLIGHT CONTROLS MENU Reconfiguration Laws 5/29 Pitch limits Pitch protections lost Pitch attitude protection is lost and the flight control computers will not limit the nose up or nose down pitch attitude.. On the PFD, the green dashes which mark the protection limits in Normal law, are replaced by amber crosses. FLIGHT CONTROLS MENU Reconfiguration Laws 6/29 Bank angle protections lost Bank angle protection is lost. On the PFD, the green dashes are replaced by amber crosses. FLIGHT CONTROLS MENU Reconfiguration Laws 7/29 The Maneuver protection is similar to Normal law. So we will go straight to the differences between Normal and Alternate high angle of attack protection. MANEUVER PROTECTION FLIGHT CONTROLS MENU Reconfiguration Laws 8/29 Low speed stability LOW SPEED STABILITY In Alternate law, the High angle of attack protection is replaced by a Low speed stability. V alpha prot and V alpha max are replaced by a stall warning speed (Vsw), indicated by a red and black barber pole. AIR FLOW FLIGHT CONTROLS MENU Reconfiguration Laws 9/29 As speed approaches Vsw a gentle progressive nose down pitch input is introduced to lower the nose and prevent further speed loss. The pitch input can be over ridden by pilot input on the side stick. Vsw LOW SPEED STABILITY FLIGHT CONTROLS MENU Reconfiguration Laws 10/29 At Vsw, an aural “STALL ! STALL !” warning is triggered. The aircraft will stall if the warning is ignored. Alpha floor protection is inoperative in Alternate law. LOW SPEED STABILITY FLIGHT CONTROLS MENU Reconfiguration Laws 11/29 In Alternate law, High speed stability replaces High speed protection. The green dashes are replaced by amber dashes on the speed scale. Above Vmo or Mmo, a nose-up input is introduced to raise the nose and prevent further speed increase. This pitch tendency can be over ridden by the pilots. HIGH SPEED STABILITY FLIGHT CONTROLS MENU Reconfiguration Laws 12/29 As in Normal law, if VMO/MMO is exceeded the over speed warning is triggered. HIGH SPEED STABILITY FLIGHT CONTROLS MENU Reconfiguration Laws 13/29 AIR FLOW Pitch limits Note that according to the failures, an Alternate law without reduced protections can exist. In this case, only the Maneuver protection is provided. The High speed and Low speed stabilities are also lost. Stall and over speed warnings are still operative. FLIGHT CONTROLS MENU Reconfiguration Laws 14/29 Direct law is the lowest level of computer flight control. Pilot inputs are now sent to the control surfaces unmodified. Because of the large number of failures required to degrade to Direct law, it is unlikely to occur during normal flight. It is most likely to be encountered when the landing gear is lowered after an inflight degradation to Alternate law. FLIGHT CONTROLS MENU Reconfiguration Laws 15/29 In Alternate law, when the landing gear is extended, the control law will degrade to Direct law.You will get an ECAM warning as shown, and additional messages on the PFD. We will study them later on. FLIGHT CONTROLS MENU Reconfiguration Laws 16/29 Direct law, as the name implies, gives a direct relationship between side stick movement and and the deflections of all surfaces. In effect, the A320 behaves like a conventional aircraft and control sensitivity will depend on airspeed. FLIGHT CONTROLS MENU Reconfiguration Laws 17/29 AIR FLOW In Direct law, there are no protections available although stall and over speed warnings will sound at the appropriate speeds. Pitch limits FLIGHT CONTROLS MENU Reconfiguration Laws 18/29 Auto-trim is not available. The crew must trim the aircraft manually. “USE MAN PITCH TRIM” is indicated on the PFD. FLIGHT CONTROLS MENU Reconfiguration Laws 19/29 Auto turn co-ordination and “Dutch roll” damping are also lost. All yaw control in direct law is through the rudder pedals. FLIGHT CONTROLS MENU Reconfiguration Laws 20/29 In the worst case of failures, such as complete loss of flight control computer power supply, the aircraft will revert to mechanical back-up mode. FLIGHT CONTROLS MENU Reconfiguration Laws 21/29 In this mode, the only method of control in pitch is manual adjustment the THS using the pitch trim wheel, provided either green or yellow Hyd. system is available. To indicate this a “MAN PITCH TRIM ONLY” appears in red on the PFD. FLIGHT CONTROLS MENU Reconfiguration Laws 22/29 Lateral control is achieved in this mode using the rudder pedals and their mechanical linkage to the rudder provided at least one Hyd. system is available. FLIGHT CONTROLS MENU Reconfiguration Laws 23/29 In most cases (e.g. by resetting the flight control computer), you will be able to recover from mechanical backup to either alternate or direct law depending on the type of failure. We will now see a brief summary of the different laws and their associated protections. FLIGHT CONTROLS MENU Reconfiguration Laws 24/29 AIR FLOW Pitch limits MMaanneeuuvveerrpprrootteeccttiioonn PPiittcchhaattttiittuuddeepprrootteeccttiioonn HHiigghhaanngglleeooffaattttaacckkpprrootteeccttiioonn BBaannkkaanngglleepprrootteeccttiioonn HHiigghhssppeeeeddpprrootteeccttiioonn In Normal law, all the protections are available. FLIGHT CONTROLS MENU Reconfiguration Laws 25/29 AIR FLOW In Alternate law, the Pitch attitude protection and the Bank angle protection are lost. Maneuver protection is kept. High and low speed stabilities are introduced. Pitch limits MMaanneeuuvveerrpprrootteeccttiioonn PPiittcchhaattttiittuuddeepprrootteeccttiioonn HHiigghhssppeeeeddpprrootteeccttiioonn HHiigghhssppeeeeddssttaabbiilliittyy LLoowwssppeeeeddssttaabbiilliittyy HHiigghhaanngglleeooffaattttaacckkpprrootteeccttiioonn BBaannkkaanngglleepprrootteeccttiioonn FLIGHT CONTROLS MENU Reconfiguration Laws 26/29 HHiigghhaanngglleeooffaattttaacckkpprrootteeccttiioonn AIR FLOW In Alternate law without reduced protections, the High speed and the Low speed stabilities are also lost. the only remaining protection is the Maneuver protection. Pitch limits MMaanneeuuvveerrpprrootteeccttiioonn PPiittcchhaattttiittuuddeepprrootteeccttiioonn HHiigghhssppeeeeddpprrootteeccttiioonn HHiigghhssppeeeeddssttaabbiilliittyy LLoowwssppeeeeddssttaabbiilliittyy BBaannkkaanngglleepprrootteeccttiioonn FLIGHT CONTROLS MENU Reconfiguration Laws 27/29 HHiigghhaanngglleeooffaattttaacckkpprrootteeccttiioonn AIR FLOW In Direct law, all the protections are lost and the aircraft handles as a conventional aircraft. Pitch limits MMaanneeuuvveerrpprrootteeccttiioonn PPiittcchhaattttiittuuddeepprrootteeccttiioonn HHiigghhssppeeeeddpprrootteeccttiioonn HHiigghhssppeeeeddssttaabbiilliittyy LLoowwssppeeeeddssttaabbiilliittyy BBaannkkaanngglleepprrootteeccttiioonn FLIGHT CONTROLS MENU Reconfiguration Laws 28/29 In mechanical backup, no protection exists. The pitch control is performed via the pitch trim wheel and the lateral control through the rudder pedals thanks to their mechanical linkages, provided the appropriate Hyd. systems are available. FLIGHT CONTROLS MENU Reconfiguration Laws 29/29 You have seen all the different laws and protections. May be you wonder how to recover if extreme conditions cause the aircraft to leave the protected envelope? (e.g. You have been flipped over by a very severe turbulence) Here is the answer. If the limits of Normal laws are exceeded, Abnormal attitude laws become active. This is a safety feature to ensure that the flight control computers will never prevent the pilots recovering from an abnormal inflight attitude. The flight control laws operate in Alternate law without protections and stabilities except for load factor protection. After recovery, controls remain in Alternate law without protections but with auto trim. There is no reversion to Direct law when the gear is extended. After all theses emotions, you will now see the Normal operation modules... NEXT MMoodduullee ccoommpplleetteedd FLIGHT CONTROLS MENU Reconfiguration Laws 30/29 LLIISSTTOOFFSSUUBBJJEECCTTSS EXIT AUDIO GLOSSARY FCOM RETURN AALLTTEERRNNAATTEELLAAWWSS DDIIRREECCTTLLAAWW MMEECCHHAANNIICCAALLBBAACCKKUUPP SSUUMMMMAARRYY AABBNNOORRMMAALLAATTTTIITTUUDDEELLAAWW作者: bocome 时间: 2011-7-31 08:58:26