03/02/21
Message Overview:
Message Description:
Flap Control Unit (FCU) detected a flight cycle count overflow (23 cycles) for Flap Transmission Brake (FTB) Check.
Possible Causes:
- Flap Control Unit (FCU) (A124)
- Left Flap Transmission Brake (FTB) (A203)
- Right Flap Transmission Brake (FTB) (A204)
- Input/Output Concentrator (IOC) (A4-IOC)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin: None
Forum Articles/Infoservice/Newsletter:Customer Forum & Newsletter - July 30th 2008
Automatically after each 20 flight cycles, the flap system conducts a Flap Transmission Brake (FTB) operational test. The test is conducted during flap retraction from 10 degrees to 0 degree under the following conditions: Weight on Wheel & Airspeed less than or equal to 70 knots.
Quick Links:
| Removal of the Flap Transmission Brake | AMM 27-52-19-000-801 |
| Installation of the Flap Transmission Brake | AMM 27-52-19-400-801 |
| Operational Test of the Flap Transmission Brake | AMM 27-52-19-710-801 |
| Removal of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-000-801 |
| Installation of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-400-801 |
| Operational Test of the Input/Output Concentrator Unit (IOC) | AMM 31-45-05-710-801 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
| Electrical Connectors - Maintenance Practice - ALL | SPM 20-20-00-02 |
Troubleshooting Recommendations:
- Perform an operational test of the Flap Transmission Brake per AMM.
- If system checks are good, do close out.
- If fault remains, continue with next step.
- In MDC, check for NO L-GP-5 BUS INPUT or NO R-GP-5 BUS INPUT messages.
- If message shows, do wiring check of LH / RH-GP-5 to FCU per WM.
- If fault remains, continue with next step.
- Do FTB resistance check as follow:
- Remove connectors from Flap Transmission Brake and record resistance of Solenoid Coils using print 27-52-19.
FTB Left Side FCU A124AP1 Or FTB A203: Typical Reading A203P1 Solenoid # 1 6J to 5J Pins 1-2 = (Normal ≈ 58Ω) A203P2 Solenoid # 2 6G to 5G Pins 1-2 = (Normal ≈ 58Ω) FTB Right Side FCU A124BP1 Or FTB A204: A204P1 Solenoid # 1 7C to 6C Pins 1-2 = (Normal ≈ 58Ω) A204P2 Solenoid # 2 7E to 6E Pins 1-2 = (Normal ≈ 58Ω) NOTE: All are the same P/N and LRU replaceable.
- Replace defective parts as necessary.
- Remove connectors from Flap Transmission Brake and record resistance of Solenoid Coils using print 27-52-19.
- Do FTB voltage check as follows:
- Release the Flap Transmission Brake with the MDC and record voltages at each connector. Check each with Normal and Alternate flaps. Should be approximately 28 VDC.
FTB A203 Left Side Normal Flaps: Alternate Flaps: A203P1 Solenoid # 1 Pin 1 to ground ____VDC ____VDC A203P2 Solenoid # 2 Pin 1 to ground ____VDC ____VDC FTB A204 Right Side Normal Flaps: Alternate Flaps: A204P1 Solenoid # 1 Pin 1 to ground ____VDC ____VDC A204P2 Solenoid # 2 Pin 1 to ground ____VDC ____VDC NOTE: Solenoid #2 powered with Normal Flaps selected and solenoid #1 powered with Alternate Flaps.
- Replace defective parts as necessary.
- Release the Flap Transmission Brake with the MDC and record voltages at each connector. Check each with Normal and Alternate flaps. Should be approximately 28 VDC.
- Do close out.
