Fault Message:

FLAP SKEW SENSOR 4/ SFCU/ WRG

Fault Code:

2750033STD

Associated CAS:

SLAT FLAP BIT
(Advisory)

One of the conditions that follow occur:

• Slat/Flap Control Unit (SFCU) does not receive input from Left Wing Flap Skew Sensor 4 (reported by SFCU 1)
• SFCU does not receive input from the Right Wing Flap Skew Sensor 4 (reported by SFCU 2)
• Input received by SFCU 1 or SFCU 2 is not in the permitted range

• Slat/Flap Control Unit (SFCU) 1 (A124)
• Slat/Flap Control Unit (SFCU) 2 (A95)
• Left Flap Skew Sensor 4
• Right Flap Skew Sensor 4
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Skew values from SFCU 1 and SFCU 2 can be monitored by accessing CAIMS:

1. SYSTEM DIAG
2. 27-00 FLIGHT CONTROLS
3. SLAT/FLAP CONTROL UNIT #1 (2)
4. LRU TEST
5. SLAT/FLAP POSITION - RAW DATA - SFCU 1 (2)
6. CONFIRM
7. PAGE 2 OF 2

   The raw position of the skew sensor #4 can be calculated like this:

   (SKEW 3 count)-(3 Minus 4 count)=SKEW 4 count

   For Aircraft Pre SB 700-27-050
   	Skew 1	Skew 2	Skew 3	Skew 4
   Recorded Value	-	-	-	-
   Calculated Value	-	-	-	-
   Recommended Value	9545	9496	8779	9518
   Maximum Permissible	9575	9526	8809	9548

   For Aircraft Post SB 700-27-050
   	Skew 1	Skew 2	Skew 3	Skew 4
   Recorded Value	-	-	-	-
   Calculated Value	-	-	-	-
   Recommended Value	9545	9496	9387	9518
   Maximum Permissible	9575	9526	9417	9548

   

1. Swap SFCUs.

   1. If system checks are good, replace defective SFCU and do close out.
   2. If fault remains, continue with next step.

2. Perform resistance test of left skew sensor 4 and right skew sensor 4.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.
      NOTE: Resistance values for the skew detectors at ambient conditions (75 °F ±10 °F) or (24 °C ±4 °C).

      Left Flap Skew Sensor 4:

      From	To	Resistance Range P/N: GT415-5702-3 (5911043)/GT415-5702-5 (5913491)	Result
      A124CP1-48	A124CP1-49 (Excitation)	120 ±20% ohms
      A124CP1-39	A124CP1-51 (Va)	93 ±15% ohms
      A124CP1-52	A124CP1-51 (Vb)	123 ±15% ohms

      Right Flap Skew Sensor 4:

      From	To	Resistance Range P/N: GT415-5702-3 (5911043)/GT415-5702-5 (5913491)	Result
      A95CP1-48	A95CP1-49 (Excitation)	120 ±20% ohms
      A95CP1-39	A95CP1-51 (Va)	93 ±15% ohms
      A95CP1-52	A95CP1-51 (Vb)	123 ±15% ohms

3. Perform wiring checks between left skew sensor 4 and SFCU 1; and right skew sensor 4 and SFCU 2.

   1. If wiring checks are not good, repair defective wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

4. Replace Skew Sensor 4.
5. Do close out.