Challenger CL604
Maintenance Inspection Authority; Maintenance Powerplant; Maintenance Airframe
Maintenance Lead Technician 20; Maintenance Technician 9
Communication Breakdown; Troubleshooting; Situational Awareness; Confusion
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Chart Or Publication; Human Factors; Manuals
Our Challenger 604 was going to ZZZZ airport near ZZZZ2. When the aircraft was passed from ZZZZ Control to ZZZZ1 Control; the Tower notified the flight crew that they were not reading the Transponder. The crew switched to the #2 Transponder which they could not read either. The crew turned and when back into ZZZZ airspace and ZZZZ Control reported that they could read the [Transponders] with no problem. ZZZZ1 Control allowed the aircraft to continue on and land at ZZZZ1. The next day the local ZZZZ1 Maintenance facility performed a Transponder functional test and found the system to be working properly. We decided to do a test flight to be sure. After takeoff again the ZZZZ1 Tower could not read the transponders. We returned to the Maintenance facility for some more troubleshooting. We learned that this foreign country had recently switched to a new ATC surveillance system. In 2006; Bombardier had issued a Service Bulletin 604-34-054 to address this issue. I complied with the Service Bulletin in 2007 with a functional test of the system with no problems. It required the removal of one wire from Pin-21 on Plug 1P1RF for Transponder #1 and Plug 2P1RF for Transponder #2. It was found that Pin-21 had been removed from Plug P2; for both transponders; instead of Plug P1. Pin 21 was reinstalled in Plug P2 and removed from P1. We did other flight test and all systems worked OK. I did some research to see how Pin-21 could have been removed from the wrong plug. What I found was that the Bombardier Service Bulletin indicated the right hand plug as viewed from the front and the Rockwell Collins TDR-94D Manual shows it as the left hand plug as viewed from the front. I went by the Rockwell Manual because it has a picture of the pin numbers on it. They are small and hard to see on the aircraft.Corrective action: Make sure that the Rockwell Manual and the Bombardier Service Bulletin both indicate the correct plug. At the present time there is no way to test that the country's ATC surveillance system is working properly on the ground. They need to come up what a procedure to do this on the ground. Otherwise you won't know that it is not working until you are in their airspace. The current functional test is unable to test that system.
Reporter stated their CL-604 aircraft never had any Transponder reading difficulties with any ATC Tower; domestic or foreign; after he had complied with the Bombardier Service Bulletin for the wire removal from Pin-21 on both Transponders. The #1 and #2 Transponders are mounted in a electrical rack; one above the other; against the sidewall on the co-pilot's side. Rockwell Collins TDR-94D is the Model number for the Transponders.Reporter stated the Service Bulletin and Rockwell Collins Manual both reference the two connector plug positions on each transponder as Plug-1 and Plug-2. He used the Rockwell Collins Manual because he could read the pin number locations easier on their connector pin layout diagrams. The Service Bulletin only showed a picture of the connector Plug; not the Pin position layouts on the connector. He later realized after the ZZZZ1 ATC Control incident; that the original Bombardier Service Bulletin had properly identified the Right-Hand (R/H) plug as the correct plug to remove the Pin-21 wire. He thought Rockwell Collins was considering revising their Model TDR-94D Transponder Manual to match the Service Bulletin's Plug positions.
An Aircraft Maintenance Technician (AMT) reports he had used a Transponder Manufacturer's Maintenance Manual instead of the Aircraft Manufacturer's Service Bulletin to identify and remove an electrical wire from connectors on #1 and #2 Transponders on a Challenger CL-604 aircraft.