EMB ERJ 170/175 ER/LR
Maintenance Airframe; Maintenance Powerplant
Communication Breakdown; Situational Awareness; Training / Qualification; Troubleshooting; Confusion
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Procedure; Aircraft; Human Factors; Manuals; Chart Or Publication
While performing Fire Bottle Job Card; referencing Aircraft Maintenance Manual 26-21-00-700; it was discovered that the fire bottle cartridges were installed in the incorrect locations allowing the left engine bottle 'A' to be discharged to the right engine and the right engine bottle 'A' to be discharged to the left engine in the event of an engine fire.  This bottle had been installed on the aircraft [in this configuration] for several years. To compound the issue; the wiring on the aircraft has sufficient slack to allow the [electrical] connectors to be installed incorrectly and the Maintenance Manual Task to replace the bottles and cartridges is not clear enough to prevent incorrect assembly. The aircraft is assembled in a manner in which cross-connection of the electrical connectors for the 'A' and 'B' engine fire bottles is possible. In an absolute worst case scenario; if both bottles are affected; neither engine would have fire protection with extreme risk for loss of life. I would suggest that Embraer generate a Service Bulletin to shorten the length of the connectors to prevent incorrect installation; and re-write the Maintenance Procedure to emphasize the correct installation of the connectors.
Reporter stated he is a Maintenance Supervisor and there are two fire bottles total (bottle 'A' and bottle 'B') that provide fire suppression for both engines. The bottles are mounted in a forward and aft position in the right stub wing area. Engine fire handles are located at the overhead panel and each fire handle has an 'A' and 'B' position that can be selected.Reporter stated one of their Technicians was performing a Functional Check of the Fire Suppression System that requires a specific voltage reading from the left or right engine fire handle to each electrical connector at the end of the wire harnesses. Each connector is then attached to a specific squib cartridge on the bottles. The same Technician noticed that a wiring harness connector was going to a different squib connection than what she was accustomed to seeing. Although the voltage check passed; the wire harness connector from the Left Fire Handle for the 'A' or 'B' selections were connected to squibs incorrectly positioned on Fire Bottle 'A'. In that configuration; if the 'A' or 'B' position was selected at the Left Fire handle; the Halon 1301 fire extinguishing agent would be distributed to the opposite engine. The EICAS display would not have shown a malfunction because the fire bottle had discharged; even though the Halon would have gone to the wrong engine.Reporter stated another Mechanic had been working in the cockpit on a different ERJ-170 aircraft performing the same type of Functional Check when he accidently bumped his head on the Overhead Fire handle and discharged one of the Fire bottle's. That's when he (the Mechanic) noticed the bottle had fired off to the opposite engine.  The electrical connector and squib were found in the opposite position on the Fire bottle from where the squib should have been positioned.  Three more ERJ-170 aircraft in the Hangar with similar cross-connected harness positions were also identified. No labeling exists on Fire Bottles 'A' or 'B'; identifying the left or right engine squib cartridge positions. The bottles are identical; interchangeable; have the same Part Numbers; come new from the Manufacturer; or overhaul Vendor; with the squib cartridges and discharge nozzles already installed. Two discharge nozzle outlets are screwed into each Fire bottle; use a common thread; are interchangeable and can be installed on either Fire bottle. There are two different Part Numbers (P/N). Two nozzles have 'Coarse-threads' and the other two nozzles have 'Fine-threads' that will only accept a specific squib with similar threads. There are also two different Part Numbers (P/N) for the four squibs; two with 'Coarse' threads and two with 'Fine' threads. The electrical connectors are also keyed to a similar squib.Reporter stated the discharge nozzles determine which squib can be installed. They are finding nozzles with associated squibs installed at incorrect positions on the Fire bottles. He suggests the harnesses be shortened; or zip-tied similar to the ERJ-190s; to prevent an electrical connector meant for bottle 'A' from reaching bottle 'B'. The wire harnesses are routed to the Fire Bottles from different directions. The ERJ-170s involved had been flying for several years and had gone through at least one C-Check without the discrepancies being noticed.  Only aircraft that had Fire Bottles replaced prior to a 2010 Revision of the Fire Bottle Component Maintenance Manual (CMM) appear to be involved. He and the Inspection Manager developed a Job Card to verify that all company ERJ-170s going through C-Checks have connectors and discharge nozzles in the correct positions.Reporter stated Embraer had issued a Service Bulletin in the past for their EMB-145 aircraft resulting from; he believes; similar problems with cross-connections of wiring harnesses. Embraer went to a colored coded system. Mechanics from other Operators of the ERJ-170s have informed him they were dealing with similar problems.
A Maintenance Supervisor reports an Aircraft Maintenance Technician (AMT) discovered that the left and right engine fire bottle cartridges had been installed at incorrect locations; allowing the left engine bottle 'A' to be discharged to the right engine and the right engine bottle 'A' to be discharged to the left engine in the event of an engine fire. The ERJ-170 had been flying for several years in that configuration.