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1、A320前轮转弯系统介绍及维护 一车间 李辉,一、背景介绍,The steering system uses the green or yellow hydraulic system to operate a steering actuating cylinder,which changes the direction of the NLG wheels.,飞机在地面滑行时的方向控制，几乎完全依赖于前轮转弯系统NWS来操作完成。如果前轮转弯系统出现故障，机组将无法掌控飞机的滑跑方向，从而使飞机偏离或冲出跑道、滑行道，轻则损伤飞机设备，严重的甚至会造成人员的重大伤亡。因此，对于前轮转弯系统相关故
2、障，必须按手册谨慎处置。,Jetblue Airbus performs a low pass for the LGB tower for a nose gear inspection,and as you can see the nose gear is in a 90-degree position.Following the flyby,the aircraft spent the next 2 hours flying over the Pacific Ocean just off Long Beach burning fuel before diverting to LAX for
3、an emergency landing,which happily was a succesful one without injuries.,Jetblue A320-232(N536JB)前起落架减震支柱上支撑防转凸耳损伤被剪切断裂,导致前轮空中偏置90度，于Los Angeles airport(LAX)执行应急着陆。,JetBlue 292 BUR-JFK makes its emergency landing at LAX.The front gear was turned perpendicular to the runway causing the sparks and smo
4、ke.,LTE International Airways A320-214 在着陆滑跑过程中因前轮转弯系统故障，导致偏离跑道，前轮陷入跑道旁边的草地。,二、系统介绍,SYSTEM OVERVIEW,The steering system receives hydraulic pressure in the following conditions:,-A/SKID&N/W STeeRinG switch is in ON position,-towing control lever is in normal position,-at least one ENG MASTER switch i
5、s ON,-aircraft is on ground.,The steering system is controlled by the BSCU,which receives order from:,-the steering hand wheels(orders added algebraically),-the rudder pedals,-the autopilot.,前轮转弯角度限制,Handwheels,During taxi,and more generally at low speed,through action on a handwheel.There are two i
6、dentical handwheels:one for the Captain,one for the First Officer.In the event of simultaneous operation,the orders that the handwheels give are algebraically added.The maximum travel of the wheels is plus or minus 74 deg.The maximum corresponding travel of the handwheel is plus or minus 75 deg.The
7、law between these two travels is not linear.,The steering angle is limited as a function of the aircraft speed.,（手轮偏转角度与前轮转弯角度比例关系）,（手轮操作时前轮转弯角度与飞机速度的限制关系）,20KTS以内，最大行程操作,速度高于70KTS，使用手轮转弯无效,Rudder pedals,During takeoff or landing,and more generally at high speed：-either through action of the Captain
8、(or First Officer)on the rudder pedals,-or automatically through the autopilot(yaw control).,In the event of simultaneous operation,the orders that the handwheels and pedals give are algebraically added.,PEDALS DISC按钮可在以下情况脱开脚蹬对前轮转弯的控制：During rudder ground check.The runway is icy.Pilot can disconnec
9、t the control through the pedals from the steering control.,When the aircraft speed is above 130 knots,the steering is not available,（脚蹬操作时前轮转弯角度与飞机速度的限制关系）,Nose Wheel Steering Servo-Control(6GC)enhanced type,图示为增强型A320系列飞机，区别在于选择活门位置与classic 不同,液压使用的是黄系统,Nose Wheel Steering Servo-Control(6GC)classi
10、c type,传统型的6GC将选择活门作为部件嵌入到整体中。液压选用的是绿系统。,Nose Wheel Steering Servo-Control(6GC),Selector valve,Bleed screw,Anti-shimmy accumulator,Servovalve,Nose Wheel Steering Servo-Control(6GC)main components,An electrically-operated selector valve and its slaved valve.When the selector valve is energized,the pr
11、essure is applied to the servovalve.A servovalve of the deflection-jet type,equipped with a LVDT sensor which detects the position of the slide valve.An adjustable diaphragm located on each output line of the servovalve,this diaphragm is used to adjust the flow to each actuating cylinder chamber and
12、 consequently the wheel steering speed.A by-pass valve which interconnects the two chambers of the steering cylinder in the event of hydraulic system depressurization.An anti-shimmy accumulator with a built-in pressure-relief valve,It can supply fluid pressurized to 15 bars in case of cavitation in
13、one chamber of the cylinder,initiated by the shimmy.A screw for the bleeding and/or depressurization of the hydraulic block.,对于传统型A320飞机，由于前轮转弯系统使用的是来自前起落架舱门关闭油路的绿系统液压压力，因此，在飞机执行重力放起落架的程序后，前轮转弯系统将无法工作，需用拖车拖回停机坪。,使用重力放起落架的英航A320-214在近进阶段,Nose Wheel Steering Feedback Sensor(3GC,4GC),P/N:E21336000,P/N:
14、C24763000(ON A/C 001-013),Nose Wheel Steering Feedback Sensor(3GC,4GC),Two identical RVDT sensors give the position of the rotating tube.The RVDT sensor is driven by a reduction gearbox attached to the landing gear strut.3GC is part of the electrical channel of the steering control,4GC is part of th
15、e monitoring channel.,The control channel acts on the servovalve as a function of the difference in position between the handwheel(in the cockpit)and the wheels.The monitoring channel delivers in a similar manner a signal which represents the position of the slide valve in the servovalve.,3GC for co
16、ntrol,4GC for monitoring,NWS系统工作原理,swivel selector valve,When the landing gear starts to retract,the swivel selector valve cuts the hydraulic power supply and connects the hydraulic block to the reservoir return line.,旋转选择活门与前起落架收放支点同轴，前起放下使活门内部液压流向前轮转弯作动系统。,steering actuating cylinder,转弯作动筒内部为：活塞推动
17、齿条与前起落架转动筒的半齿轮机构啮合作动，通过后部的上、下扭力臂驱动前起落架减震器完成转弯动作。,anti-shimmy valve,减震支柱从前起落架内拔出后，可以看出前轮转弯作动筒驱动的是中间的旋转筒。,前起落架减震支柱被拔出，扭力臂的下端仍然在位。,三、维护要点,1、关于3GC、4GC的维护,由前面的介绍可知：3GC、4GC的反馈信号的准确性对整个转弯系统的工作起到了决定性的作用。针对机组反映的滑行中无法保持直线（偏左或偏右）的问题，在排除了侧风、道面状况、机轮状态以及机组操作方面的原因后，需要对3GC进行微调。调节或更换传感器，请严格遵守AMM程序！,前轮转弯不当或系统故障将导致轮胎的
18、过量磨损，甚至爆胎,AMM手册关于前轮转弯0位的调节提供了9种程序，其主要区别就是采用了不同的基准参考数据和3GC、4GC调节工具：基准数据：1Rudder Trim Angle as Reference 2NLG Centering Cams as Reference 3Nose-Wheel Alignment Tool 调节工具：For P/N C24763000：F26630200 或 M46196-100F26792000For P/N E21336000：F26792000,AMM 32-51-00-820-00 x,1、Adjustment of the N/WS Zero Pos
19、ition with the Adjusting Tool F26630200 for A/C with N/WS Sensor(3GC,4GC)P/N C24763000,Rudder Trim Angle as Reference 2、Adjustment of the N/WS Zero Position with Adjusting Tool M46196-100 for A/C with N/WS Sensor(3GC,4GC)P/N C24763000,Rudder Trim Angle as Reference 3、Adjustment of the N/WS Zero Posi
20、tion for A/C with N/WS Sensor Box(3GC,4GC)P/N E21336000,Rudder Trim Angle as Reference 4、Adjustment of the N/WS Zero Position with the Adjusting Tool F26630200 for A/C with N/WS Sensor(3GC,4GC)P/N C24763000,NLG Centering Cams as Reference 5、Adjustment of the N/WS Zero Position with the Tool M46196-1
21、00 for A/C with N/WS Sensor(3GC,4GC)P/N C24763000,NLG Centering Cams as Reference 6、Adjustment of the N/WS Zero Position for A/C with N/WS Sensor Box(3GC,4GC)P/N E21336000,NLG Centering Cams as Reference 7、Adjustment of the N/WS Zero Position with the Adjusting Tool F26630200 for A/C with N/WS Senso
22、r(3GC,4GC)P/N C24763000 with the Nose-Wheel Alignment Tool 8、Adjustment of the N/WS Zero Position with Adjusting Tool M46196-100 for A/C with N/WS Sensor(3GC,4GC)P/N C24763000 with the Nose-Wheel Alignment Tool 9、Adjustment of the N/WS Zero Position for A/C with N/WS Sensor Box(3GC,4GC)P/N E21336000
23、 with the Nose-Wheel Alignment Tool,前起落架支撑主结构与旋转筒之间有一个前轮定中的目视指示标记，上下刻度标志线对齐的时候为飞机支线滑行（前轮转弯0位）。注意：此标记仅仅作为维护中的快速参考标记，在对转弯系统的调节中不作为前轮定中的参考标准，AMM无此标志线作为定中参考的调节程序！,转弯系统测试对辅助设备的要求,注意：在AMM和TSM中，关于在地面对前轮转弯进行操作测试时都必须使用辅助设备以减小轮胎与地面的摩擦力矩对转弯操作精准性的影响。可以采用：1、用两块平面钢板，中间涂抹足量润滑油脂，之后铺入前轮与机坪地面之间。此法方便实用，比较常用。2、使用千斤顶的组合
24、，将前轮推离地面。此法较为复杂，对设备要求较高，较少使用。,P/N C24763000传感器的调节,传感器齿轮箱调节工具：F26630200安装于传感器与齿轮箱之间，通过微调减速齿轮的位置来得到正确的传感器0位（通过F26792000传感器电压测试装置得出的U1、U2电压值在合适的比例范围内）,传感器电压测试装置：F26792000安装于BSCU线路与传感器3GC或4GC之间，借助电压表可读出RVDT内部U1、U2两级线圈的电压值，调0工作就是围绕这两个电压差值进行齿轮箱内传动齿轮的微调,传感器齿轮箱调节工具：M46196-100调节原理与前面所提工具相同，但无法与传感器3GC（4GC）同时安
25、装，调节齿轮箱后需要拆下，才能用电压测试装置读取U1、U2,P/N E21336000传感器的调节,传感器电压测试装置F26792000安装于BSCU线路与传感器3GC或4GC之间，借助电压表可读出RVDT内部U1、U2两级线圈的电压值。传动齿轮的调节也是在位调节。,CAUTION:IF THE SENSOR BOX HAS P/N E21336000,NEVER REMOVE THE SENSOR FROM THE GEARBOX.THE SENSOR AND THE GEARBOX ARE AN ASSEMBLY THAT YOU MUST NOT DISASSEMBLE ON THE A
26、IRCRAFT.IF YOU REMOVE THE SENSOR FROM THE GEARBOX:-YOU WILL CAUSE DAMAGE TO THE SENSOR BOX-THE ADJUSTMENT OF THE SENSOR BOX WILL NO LONGER BE CORRECT.,如果U1、U2数据不在范围内，则需要调节RVDT上部的传动齿轮机构，对调节蜗杆（worm screw)进行调节之前需要松开图中2的四个固定螺栓（内六角），以脱开传感器与齿轮机构的啮合，否则无法作动调节蜗杆。,调节蜗杆Worm screw,松开四个固定螺钉后就可以对调节蜗杆5进行旋转调节。首先将调节
27、蜗杆端部覆盖的密封胶刮去，注意不要刮伤部件表面。露出蜗杆头后，再用小一字刀轻轻旋转，同时在电压表上观察U1U2的变化情况，确认U1=U2 plus or minus 20 mV，调节完成。注意：调节蜗杆非常灵敏，轻微旋转即可改变RVDT电压值，严格按照程序操作，切忌蛮力拧紧或松。,调节蜗杆Worm screw,3GC、4GC传感器的拆换,对于P/N C24763000传感器的拆换：传感器与传动齿轮箱是相互独立的部件，传感器需要单独拆装，更换相对简单，安装新件后需重新验证0位电压。AMM 32-51-41也提供了齿轮箱的拆换程序，安装的时候需要用到前面提到的校准工具配合调节。对于P/N E213
28、36000传感器的拆换：传感器与传动齿轮组为一个整体部件，传动齿轮机构加载有弹簧偏置力，拆换或串件时必须注意机构0位的调节和推杆锁销的使用。,一架IBERIA 的A320-214在推出后，前轮转弯系统故障，前轮偏转90度，无法操作。,拆换P/N E21336000传感器时应严格按照AMM程序进行,推杆锁销pushrod 在传感器的安装过程发挥很重要的作用：新的传感器的传动齿轮组在内部弹簧偏置力的作用下通常是处于最大行程的一侧（已超出前轮转弯最大角度），安装前必须利用前面所提调节工具人工调回0位，然后按入推杆销锁定齿轮组（内部齿轮保持在调节完毕的0位），再装在前起落架的底座上，安装完毕，拉出推杆
29、销解除对齿轮组的锁定。,推杆锁销pushrod,对于B2403和B2374飞机,由于这两架飞机的BSCU与深圳公司A320/319机队其他飞机的件号不同，功能比其他飞机要先进，在对这两架飞机的3GC和4GC进行调节或更换时，可以借助CFDS进入BSCU的SPECIFIC DATASTEERING DATARVDTCOM&RVDTMON进行两个传感器参数值的对比和快速调节，可以减少排故时间，具体参照AMM。RVDTCOM为3GC探测到的前轮转弯角度值RVDTMON为4GC探测到的前轮转弯角度值,2、对于Nose Wheel Steering Servo-Control(6GC)的排故,以B239
30、3前轮转弯失效为例：10/15航后B-2393滑行到位时，出现前轮转弯故障，自检有前轮转弯控制盒信息；10/25杭州短停有BSCU信息，滑行手轮操作有较大偏差，飞机由拖车拖到机位，地面复位BSCU跳开关后正常；10/30短停机组反映早上从深出发时，在滑行道上转弯时，有前轮转弯故障信息，无法转弯，机组刹车后重置前轮转弯防滞电门，正常，后续及回程都正常。短停查PFR曾有“STEERING ELEC BOX 5GC”信息，做BSCU测试正常。,针对NWS FAULT 的ECAM警告和STEERING ELEC BOX 5GC故障信息，TSM 32-51-00-810-833给出了详细排故程序：1、做
31、系统测试，确认故障现象和信息2、根据测试结果选择排故方向,BSCU测试正常，根据TSM程序就要通过MCDU读取BSCU内的TROUBLE SHOOTING DATA，根据故障代码再继续明确排故方向和重点：B2393的BSCU故障代码为 90,（此图中FAULT CODE为B8）关于读取BSCU内排故数据和相关数据的解释请参照TSMD/O32-42-00-030.,针对故障代码90，TSM将排故重点放在了6GC内伺服活门上，并提供如下测试程序：,-Do a check of the servovalve-Put the aircraft in the necessary configuratio
32、n to let the nosewheels move freely to the left or the right其目的是通过实际操作前轮转弯系统进行作动，通过查看并比较6GC内伺服活门“定中位”的电流值（SSV CURRENT parameter ISV1或ISV2）是否处于正常范围内来判断故障。ISV1脚蹬操作完全左转6度后恢复定中位伺服活门电流值ISV2脚蹬操作完全右转6度后恢复定中位伺服活门电流值,伺服活门在6GC中的位置与结构,伺服活门电流值ISV1或ISV2,对于ISV1和ISV2数值的正确范围如下：-0.5 X(ISV1+ISV2)is less than or equal
33、 to plus or minus 0.5 mA.-(ISV1-ISV2)is less than or equal to plus or minus 0.50 mA.B2393测出ISV1和ISV2分别为-0.74和-0.75，经计算已经超出上面所列范围，可以判断出：伺服活门在前轮转弯处于定中位时（无操作信号），其内部线圈的电流值已经超出正常工作范围。更换6GC后做功能测试转动前轮正常，继续对6GC做测试，得出ISV1和ISV2为+0.00，+0.01,BSCU转弯数据说明,SELV ORDER:Nose Wheel Steering(NWS)electro-distributor stat
34、us(OPEN or CLOSED),SSV CURRENT:NWS servovalve current(-10 mA SSV CURRENT+10 mA),STEER ORDER:Commanded steering angle(-75 deg.STEER ORDER+75 deg.),CAPT ANGLE:CAPT steering handwheel angle(-75 deg.CAPT ANGLE+75 deg.),FO ANGLE:F/O steering handwheel angle(-75 deg.FO ANGLE+75 deg.),PEDAL ANGLE:ELAC angl
35、e(-75 deg.PEDAL ANGLE+75 deg.),NWS ANGLE 3GC:RVDT COM angle(-75 deg.NWS ANGLE 3GC+75 deg.),SSV SPOOL:LVDT spool position(-0.6 mm SSV SPOOL+0.6 mm).,故障总结,由于在前期的排故过程中没有重视MCDU中提供的TROUBLE SHOOTING DATA，只是简单的根据故障现象和故障信息更换了BSCU和5GC，造成了后来故障的重复发生。在类似故障排除过程中应该有意识的读取TROUBLE SHOOTING DATA并按TSM提供的排故思路指导排故工作。,日常
36、维护,日常维护中应严格按照工卡要求进行，尤其对于前轮的气压检查应更加注意，这也是引起转弯系统故障一个重要因素。对于机组反映的转弯异常响声等等，应及时报告并润滑转弯机构和测试。关注转弯系统液压管路和部件的渗漏并及时排除。,推飞机注意1、Do not tow the aircraft if the dimension H is more than 300 mm(11.8110 in.).If you do,you can cause damage to the cams that make the nose gear wheels go back to the center position.,2、不要超出最大转弯角度，如出现角度过大现象必须及时提醒拖车司机。,谢谢观赏祝大家工作顺利、开心一车间 李辉2009/02,
