737NG 皮托管加温的几点说明

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之前碰到的皮托管加温的一些问题，在这里总结一下。

01

皮托管加温与空地逻辑无关

这是之前有人问到的一个问题。

在PSEU置空中模式时，我们需要拨掉很多的跳开关，其中就有皮托管加温的：

AMM TASK 32-09-00-840-801

Prepare to Put the Airplane in the Air Mode

但是，在所有手册的30章中，并没有提到皮托管加温受空地信号的影响。

↑ 旧的OFF/ON控制面板

↑ 新的AUTO/ON控制面板，机队目前都是这种构型

为了防止机组忘记打开皮托管加温，导致皮托管结冰，波音推出了SB 737-30A1063，对皮托管加温系统进行了改装。

改装后的飞机使用了AUTO/ON构型的控制面板，当电门在自动位时，任一发动机起动时都会自动向皮托管加温系统提供电源。

从系统描述和原理图都能看出，不管新、旧皮托管加温面板的构型，皮托加温都与空地信号没有关系。

那么是手册错了么？于是我又去看了看32章的手册。

↑ SDS 32-09-00 Page 30

↑ SDS 32-09-00 Page 31

These are the ground mode relays:

• R591 for the automatic ground speedbrake control

• R595 for the pitot and probe heaters, the left and right pack valves, and power transfer unit (PTU)

• R596 for the nose wheel steering actuator.

再看SSM/WDM：

WDM里通过R595的C1/C2/C3触点连接到30-31-11，但是在WDM 30-31-11里却找不到相应的连接。

SSM中未标出到皮托管加温的相应连接。

经过询问波音得知，这个是手册错误。空地信号并不会影响皮托管加温，在 JUN 15/2018 的手册中将进行修订。

02

皮托管加温指示

驾驶舱皮托管加温控制面板通过互感线圈，监控皮托管内部加热器电流，当电流超出正常范围给出报警，点亮相应的皮托管加温灯。

案例：

某737NG飞机航前检查时发现皮托管加温电门放ON位后，P5-9面板上TAT和左AOA灯不灭。

↑ L ALPHA VANE 和 TEMP PROBE灯亮

复位跳开关无效。用手触摸TAT和左AOA探头加温正常，脱开加温面板插头重新安装后正常。

↑ 指示电源跳开关P6-3 F16/F18

正常情况下，拨出指示电源跳开关后，这些灯会熄灭。

如果探头加温正常，判断为指示故障后，可以按MEL放行：

注意：在检查是否能加温时，要和正常的比较来判断，发热量亮应该差不多。

03

DEU通电时不加温灯熄灭约5秒

参见737NG-FTD-30-16003，仅针对装有DEU-I （I型DEU）的飞机。DEU自检时会切换所有输出模拟离散，发动机运转信号会使皮托管加温系统工作。

Description

Operators have reported multiple lights on the Window and Pitot Heat Module momentarily extinguishing during DEU power up after the incorporation of SB 737-30-A1063 or if a delivered airplane has the Automatic Activation Air Data Sensor Heater System option installed and subsequently retrofitted with a DEU-I (P/N 4081600-930).

When the DEU is powered up or performs a self test, and engines are not running, approximately 80 seconds into the test, the Air Data Sensor Heater System momentarily turns on and the associated lights extinguishes for approximately 5 seconds and the Master Caution may be triggered. The annunciators are: CAPT PITOT, L ELEV PITOT, L ALPHA VANE,TEMP PROBE, F/O PITOT, R ELEV PITOT, R ALPHA VANE, and AUX PITOT.

Note: During airplane power up, before the engines are running, the lights on the Window and Pitot Heat Module associated with the Auto Activation Air Data Sensor Heater System are illuminated. The heating system should remain off and the lights illuminated until the engines are running.

Through troubleshooting and testing, Boeing has isolated the issue to be attributed to the DEU-I installed in conjunction with the Auto-Activation Air Data Sensor Heater System. The issue does not occur if two DEU-IIs (P/N 4081600-940) are installed.

Status

Boeing has researched and conducted testing with the DEU-I and DEU-II and has found the root cause for the difference in the Auto-Activation Air Data Sensor Heater System response to a DEU-I being installed. The Air Data Sensor Heater System uses an output analog discrete from the DEUs to determine if the engine is running. This engine running signal will energize the relays to automatically turn on the Air Data Sensor Heater System.

During power up and a self-test, the DEUs will very briefly toggle all of their output analog discretes. The DEU-I runs and toggles this output analog discrete slower than the DEU-II. The DEU-I toggles its output slow enough for the probe heat system to detect. This causes the Air Data Sensor Heater System to turn on momentarily and therefore causes the lights to extinguish for up to 5 seconds while the DEU reboots.

The issue does not happen if two DEU-II's are installed. The issue can happen if one of the installed DEU's are a DEU-I.

Interim Action

No Interim Action is necessary. See Final Action.

Final Action

Operators are to be aware of the condition where the lights on the window and pitot heat module will illuminate if a DEU-I is installed in conjunction with the Auto-Activation Air Data Sensor Heater System.

No maintenance action is necessary for the noted condition. There are no associated maintenance messages, the system will recover on its own and there is no potential damage being caused due to the Auto-Activation of the Air Data Sensor Heater System and associated lights extinguishing.

完

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