An Inspector and Mechanic describe how the lack of a standard method of marking and disassembling the inlet fan blade positions on a BMW Rolls Royce BR710 engine for a Gulfstream V aircraft led to vibration exceedences and damage to the engine inlet abradable liner after reassembly.
Synopsis
An Inspector and Mechanic describe how the lack of a standard method of marking and disassembling the inlet fan blade positions on a BMW Rolls Royce BR710 engine for a Gulfstream V aircraft led to vibration exceedences and damage to the engine inlet abradable liner after reassembly.
Narrative
I was acting as RII Inspector on the inspection. A previous night weekend crew disassembled the right-hand engine fan blades. Fan blades were laying on the table numbered; when we came into work. During reassembly of the right-hand engine we found the Hub to be marked with a felt tip marker 24; 1; 2; 3; 4; 5. Myself; as Inspector/Mechanic X; and mechanics Y and Z all agreed that this is where the blades should go. The Computerized Maintenance Program (CMP) Jobcard calls out to label the blades with a felt tip marker. We also replaced two Annulus fillers during the process which may have contributed to the vibration. Over the following weekend the engine was run and resulted in a N1 Vibration Exceedance and damage to the Abradable Liner. The weekend crew disassembled the engine and claimed that we had assembled the fan blades approximately 180 degrees off. There were scribed marks on the hub which we did not see. One; with an arrow pointing Counter-Clockwise (CCW); [positions] 2; 3; it is not clear who put the numbers on the hub with felt tipped marker. The same crew reassembled the engine in what they thought was the correct location of the blades. [Several days later] January 2012; I and three other mechanics disassembled the right-hand engine and found the blades to be clocked-off by one position. (# 1 blade was in # 24 position). Night turn [Night shift that evening] reassembled [the blades] in the correct position. Suggest creating a standard method of marking and disassembling for each type of engine. Marking the Number One position or Top Dead Center (TDC) on the hub and taking a picture before disassembly. Print picture and have it in the Work Order (W/O) package. Have the same crew reassemble the engine that disassembled it; if at all possible. There were already photo illustrations of the correct procedure for marking the hub that someone had created for this engine. They were not at the aircraft during the process. Most of the people were not aware that the photos existed. I got a copy of the photos January 2012. The process to do it correctly was already created; it just wasn't available during this inspection.
Second reporter narrative
When I got to work a Gulfstream V fan blades; retainer ring; rotating fairing; and nose cone were all on the table. I was told by my Lead to reinstall everything. Inspector/ Mechanic X was RII and he watched all work done. Started by verifying all Part Numbers (P/N) and Serial Numbers (S/N) matched the Gulfstream Computerized Maintenance Program (CMP) Job Cards. All the blades and annulus fillers were clearly marked with felt tip marker as stated to do so in their Removal Jobcards. The fan hub was clearly marked with a felt tip marker [showing the numbers] #24; 1; 2; 3; 4; 5. Inspector/Mechanic X and Mechanic Z both witnessed the hub markings. There was no question as to the orientation of the fan blades; the Gulfstream V CMP Jobcard; #72XXXX; tells you to mark it [the hub] with a felt tip marker; there is no mention of any other markings on the Fan Hub. I finished installing fan blades; annulus fillers; retaining ring; nose cone and rotating fairing. Inspector/Mechanic X did the RII [Inspection] and bought back [signed-off] my paperwork. Two of the annulus fillers had to be replaced due to cracks found by Non-Destructive Testing (NDT) inspections. Concerns were brought up about vibration due to the parts change; Inspector X called Rolls Royce; [the engine manufacturer] and they said we might have to balance the engine if the vibration is not within limits. We wrote-up the engine for a vibration check and I went home. My next work day was several days later and that's when I was informed the engine vibration was so bad that the fan blades dug into the [abradable] liner and that they suspected the fan blades position was not correct. Upon further investigation we found that the mechanics that removed the fan blades did not mark the hub and they were going by a different starting mark. The Gulfstream Computerized Maintenance Program Jobcard # 72XXXX; just states to use a felt tip marker; we need a common practice for marking the blades and the hub; or the reference material should state if there is another point of reference.
NASA callback
Reporter stated his company's operation uses Gulfstream's Computerized Maintenance Program (CMP); which was built from an Avtrak Maintenance Tracking Compliance Program for maintaining their Gulfstream V aircraft. Inspectors and mechanics log onto their computer system program under a specific Gulfstream tail number and can pull up the CMP for the aircraft.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.