B744 Body Gear Steering ?

[SMOC]

Is there a way to monitor if the body gear is locked or unlocked?

The Classic had the light on P2, can you get something from the 744 CMC?

Cheers.

[MATMAX]

basically messages ...
maybe ACMS ...

[sinkingship]

From, AMM Step 2 normally none.

B. Body Gear Steering Fault Indication (Figure 4)
(1) The takeoff aural warning horn will sound if takeoff is attempted with body gear steering actuators not centered and locked.
(2) Normally there is no indication of body gear steering operation. In the event of a fault in the system, advisory and status messages are displayed on EICAS. The hydraulic control modulepressure switches, arming switch and arming relays are monitored directly by the EIU. Actuator unlock signals come from the proximity switch electronic unit (PSEU).
(3) Advisory and status message BODY GEAR STRG will be displayed when either of the following conditions exists:
(a) Both the primary and alternate landing gear subsystem inputs from the PSEU indicate a body gear steering actuator unlocked without a steering command.
(b) A hydraulic control module pressure switch indicates pressure without a steering command.
NOTE: The status message is in non-volatile memory.

[gas path]

As stated a BODY GEAR STRG status msg will show for an unlocked condition (uncommanded)
The status of individual switches can be seen on the EXISTING FAULTS and FAULT HISTORY pages.
Individual switch performance can also be checked on the ACMS with 'input monitoring'.:8

[spannersatcx]

CMC input monitoring.

[gas path]

CMC input monitoring.
Yep! Correct!:ok:

[spannersatcx]

If you really want to know what each switch is doing then:

Bit Condition 0(unlocked/open/no pressure) 1(locked/closed/pressure)
Switch__________________Port/Label____Bit
R BODY GR STRNG LEFT PRI_ E/070/271/00 26 UNLOCKED LOCKED
R BODY GR STRNG RIGHT PRI E/070/271/00 27 UNLOCKED LOCKED
L BODY GR STRNG RIGHT PRI E/070/271/00 28 UNLOCKED LOCKED
L BODY GR STRNG LEFT PRI_ E/070/271/00 29 UNLOCKED LOCKED
R BODY GR STRNG LEFT ALT_ E/070/273/00 26 UNLOCKED LOCKED
R BODY GR STRNG RIGHT ALT E/070/273/00 27 UNLOCKED LOCKED
L BODY GR STRNG RIGHT ALT E/070/273/00 28 UNLOCKED LOCKED
L BODY GR STRNG LEFT ALT_ E/070/273/00 29 UNLOCKED LOCKED
BODY GEAR STRNG ARM_____C/026/003/10 16 OPEN CLOSED
L BODY GEAR PRESS________C/026/005/10 15 NO PRESSURE PRESSURE
R BODY GEAR PRESS________C/026/004/01 15 NO PRESSURE PRESSURE

After you put the port/label in you then read the relevant BIT in the 2 lines of code if it's a 0 then it's unlocked/open/no pressure if it's a 1 then it's locked/closed/pressure

[SMOC]

Hey Spanners,

Did it today, problem I came across is counting the 26th BIT? It was a 0 and should have been a 1 for LOCKED.

Is there a special way to count BITs? Single digits or pairs?

Cheers SMOC

[jimpy1979uk]

Hi,

Counting bits is as straight forward as counting backwards from LSB to MSB. Top line per sample is bit 32 on the LHS then read accross and then step down a line and the bit on that line on the RHS is bit 1.

As for input monitoring, its great when you've got a fault with the contacts monitored by the PSEU which is where in the input monitoring gets its information from.

But if you get certain faults with the contacts in the primary switches it can be possible for it to look all fine on the input monitoring but there's still a turning fault usually just one direction. This is because the contacts used in the primary switches to signal the Body Gear Steering Control Module in the LH Body Gear Bay are different from the contacts used by the input monitoring.

Have a look at the wiring diagrams the next time you get to see them.


So if looks all good on the input monitoring but there's still a fault then wiring diagrams out and get up and check the switches from the control module in the LH body gear bay.

Jimpy