Posting in Tech Log re Airbus potential problems
Posting in Tech Log re Airbus potential problems
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When you enter the web site you will see among many others the title TECH LOG. Open it and scroll down until you see A310 / A320 Problems, One more time. Open that and yes you should be concerned. I will make a post to the mechanics/engineers regarding potential problems that may effect rrouble shooting of the A310 flap/slat system.
Open up the other pages of the techlog list of contents and you will find other postings on the same subject under my name.
Open up the other pages of the techlog list of contents and you will find other postings on the same subject under my name.
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During the design phase of the A310 I worked a technical consultant in the capacity of Manager of Reliability, Maintainability and Systems Safety. I worked for the German firm that was the lead contractor responsible for the design of the flap slat drive systems.
In the evaluation of the design I pointed out several areas where the design was in conflict with the then existing JARs. The design deficiency had to do with providing clocking keys on the electrical connectors to prevent the cross connection of similar sized and configuration electrical connectors.
The German firm refused to comply providing the following reasons. 1) The connectors were too expensive as opposed to purchasing identical connectors for each installation and 2) The lead time to obtain the connectors was too long relative to the delivery schedule of the drive systems.
This problem exists in the following areas:
Wing tip brakes
PPUs on the wing tips and on the PCUs
The PCU solenoids
The Command sensor units
The method chosen by Airbus is to use tiebacks on the electrical looms leading to the various units. The tiebacks limit the length of the individual leads that connect to the various devices so that cross connection can’t take place. However when maintenance is pulled in the areas where the tiebacks are, the tiebacks can be cut in order to facilitate maintenance access or the removal of one of the electrical components. The tiebacks are not always replaced or are not in the same place they were when the system was installed. On the Command Sensor Unit they identify the two connectors as A & B to limit the cross connection problem.
This can lead to operational problems as well as maintenance trouble shooting.
If the CSU connectors are cross-connected there are no adverse effects. However if a problem develops then troubleshooting can be a nightmare trying to trace the problem. The Flap / Slat computer can’t identify the problem.
If the PPU connectors are cross-connected the system won’t work, as the computer will stop all commands.
If the solenoids on the PCU hydraulic modules are cross connected the results could be incorrect commands to the PCU or force fighting between the two drive motors on the PCU or, slower than normal commanded speed.
The Flap Slat computer was not adequately tested during the development of the flap system and the manufacturer of the computer refused to create a Failure Modes and Effect Analysis saying, it was too expensive and too time consuming. By not creating the FMEA they have severely handicapped the maintenance types in troubleshooting the computer. Also, the computer can’t adequately test itself. Case in point. On the first revenue flight on a Lufthansa A 310 to Cairo the pilot could not retract the flaps after landing. Nobody could figure the problem and the “Dolls Eyes” on the computer did not register the problem nor, did it provide any hints as to where to start. They flew the aircraft back to Frankfurt in non-revenue status with the flaps extended.
Upon arrival at Frankfurt the best German minds could not diagnose the cause of the problem. They ended up disconnecting the system and manually retracted the flaps. They then reconnected the system and tested it and placed the aircraft back in service.
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The Cat
In the evaluation of the design I pointed out several areas where the design was in conflict with the then existing JARs. The design deficiency had to do with providing clocking keys on the electrical connectors to prevent the cross connection of similar sized and configuration electrical connectors.
The German firm refused to comply providing the following reasons. 1) The connectors were too expensive as opposed to purchasing identical connectors for each installation and 2) The lead time to obtain the connectors was too long relative to the delivery schedule of the drive systems.
This problem exists in the following areas:
Wing tip brakes
PPUs on the wing tips and on the PCUs
The PCU solenoids
The Command sensor units
The method chosen by Airbus is to use tiebacks on the electrical looms leading to the various units. The tiebacks limit the length of the individual leads that connect to the various devices so that cross connection can’t take place. However when maintenance is pulled in the areas where the tiebacks are, the tiebacks can be cut in order to facilitate maintenance access or the removal of one of the electrical components. The tiebacks are not always replaced or are not in the same place they were when the system was installed. On the Command Sensor Unit they identify the two connectors as A & B to limit the cross connection problem.
This can lead to operational problems as well as maintenance trouble shooting.
If the CSU connectors are cross-connected there are no adverse effects. However if a problem develops then troubleshooting can be a nightmare trying to trace the problem. The Flap / Slat computer can’t identify the problem.
If the PPU connectors are cross-connected the system won’t work, as the computer will stop all commands.
If the solenoids on the PCU hydraulic modules are cross connected the results could be incorrect commands to the PCU or force fighting between the two drive motors on the PCU or, slower than normal commanded speed.
The Flap Slat computer was not adequately tested during the development of the flap system and the manufacturer of the computer refused to create a Failure Modes and Effect Analysis saying, it was too expensive and too time consuming. By not creating the FMEA they have severely handicapped the maintenance types in troubleshooting the computer. Also, the computer can’t adequately test itself. Case in point. On the first revenue flight on a Lufthansa A 310 to Cairo the pilot could not retract the flaps after landing. Nobody could figure the problem and the “Dolls Eyes” on the computer did not register the problem nor, did it provide any hints as to where to start. They flew the aircraft back to Frankfurt in non-revenue status with the flaps extended.
Upon arrival at Frankfurt the best German minds could not diagnose the cause of the problem. They ended up disconnecting the system and manually retracted the flaps. They then reconnected the system and tested it and placed the aircraft back in service.
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The Cat
