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本期來(lái)聊聊「X-BLD」邏輯
1.故障現(xiàn)象
737NG飛機(jī)撤逢,偶爾會(huì)碰到起飛爬升過(guò)程中,機(jī)組反映發(fā)動(dòng)機(jī)參數(shù)正常粮坞,某一臺(tái)發(fā)動(dòng)機(jī)N2指示框上出現(xiàn)X-BLD指示笛质。
偶爾也有在關(guān)車后出現(xiàn)的,如下圖捞蚂,兩臺(tái)發(fā)動(dòng)機(jī)N2指示框上都有X-BLD指示:
很明顯,這是一個(gè)假的指示跷究。
然而姓迅,更令人驚奇的是……
AMM&FIM&SSM&WDM,翻遍了哪一本手冊(cè),都沒(méi)能找到X-BLD出現(xiàn)的條件和邏輯丁存。
唯一知道的是:
In flight, an amber X-BLD START message appears above the N2 indication if starter assist is required.
2.故障原理
問(wèn)波音后肩杈,得知X-BLD出現(xiàn)的邏輯如下:
The exact logic schematics of the information processed by the DEU cannot be provided. The DEU looks at: Air/Ground, Start Lever, Fire Handle, Altitude, Airspeed, and N2.
The X-BLD message will be displayed if the subject engine fuel control switch is in cutoff and the aircraft is in the cross bleed start envelope; or if the engine's N2 RPM falls below the minimum windmilling N2 speed; which is 11% N2.
The X-BLD message is driven by the DEU and one of the logic requirements is dependent on the air seeking air/ground relays. If one of the air seeking air/ground relays sends a signal that the airplane is in air, it is possible that the X-BLD message may appear. The X-BLD message requires the engine fuel control switch to be in cutoff and that the engine fire switch not be pulled, before it determines whether the engine or air data parameters are within the X-BLD envelope.
總結(jié)如下,當(dāng)飛機(jī)在空中解寝,且下列條件都滿足時(shí)扩然,X-BLD出現(xiàn):
1. 飛機(jī)在空中
2. 發(fā)動(dòng)機(jī)滅火手柄未拉出,發(fā)動(dòng)機(jī)起動(dòng)手柄在CUTOFF位聋伦,當(dāng)前在交輸引氣起動(dòng)包線內(nèi)夫偶;或N2轉(zhuǎn)速降低至最低風(fēng)車起動(dòng)轉(zhuǎn)速以下(11%)
所以,可以看出觉增,當(dāng)發(fā)動(dòng)機(jī)參數(shù)正常時(shí)兵拢,如果出現(xiàn)X-BLD信息:
1. 飛機(jī)在空中時(shí)出現(xiàn),最可能是發(fā)動(dòng)機(jī)起動(dòng)手柄信號(hào)問(wèn)題逾礁,本來(lái)在IDLE位说铃,DEU的信號(hào)是CUTOFF位。
2. 飛機(jī)在地面關(guān)車后出現(xiàn)嘹履,最可能是空地信號(hào)問(wèn)題腻扇,此時(shí)DEU得到的空地信號(hào)還是飛機(jī)在空中,而且此時(shí)一般都是雙發(fā)同時(shí)出現(xiàn)X-BLD信息砾嫉。
3.排故總結(jié)
如果發(fā)動(dòng)機(jī)參數(shù)正常幼苛,可與機(jī)組溝通是一個(gè)假故障,航后排故焰枢。
故障處理可先看EEC和PSEU自檢代碼蚓峦,沒(méi)有可參考FIM 76-05 TASK 809排故。
X-BLD Indication Displayed Over N2 Indicator during Normal A/C Operations - Fault Isolation:
X-BLD message illuminates over Engine N2 indicator during normal operations and when?engine start lever is in the IDLE or RUN position.
這個(gè)FIM主要針對(duì)的是空中出現(xiàn)的情況济锄,可能原因:
1. 起動(dòng)手柄A通道繼電器, R566(L)或 R568(R)
2. DEU1或DEU2及線路
3. EEC
4. 起動(dòng)手柄電門組件
一般繼電器或起動(dòng)手柄電門可能性較大暑椰。
對(duì)于地面關(guān)車后出現(xiàn)的故障,PSEU空地信號(hào)可能性較大荐绝,可以采取整機(jī)斷電一汽,或者復(fù)位PSEU跳開(kāi)關(guān):
P6-2:
C15-HYD SYS LDG GR SYS XFR VALVE SEC
C16-HYD SYS LDG GR SYS XFR VALVE PRI
P6-3:
B17-LANDING GEAR LATCH & PRESS WARN
C15-LANDING GEAR AIR/GND SYS 2
C16-LANDING GEAR AIR/GND SYS 1
D1-PSEU PRI
D2-PSEU ALTN
問(wèn)題:
我們平時(shí)在PSEU上人工將飛機(jī)置于空地模式時(shí),為什么不會(huì)出現(xiàn)此信息呢低滩?
SSM31-62-14
去SSM32-09-11/12里可以看到PSEU給DEU的空地信號(hào)邏輯:
邏輯信號(hào)之前有一個(gè)非門召夹。
在AMM?TASK 32-09-00-860-801,Put the Airplane in the Air Mode里恕沫,開(kāi)始有如下提醒:
NOTE:
Using the PSEU BITE procedure to simulate air mode is the recommended method.Using deactuators or jacking the airplane are the alternate methods. The use of?deactuators or jacking the airplane will cause nuisance faults.
這個(gè)故障本身排故其實(shí)很簡(jiǎn)單
關(guān)鍵要搞清楚背后的邏輯
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