Date: 201409
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B757-200
Operator: Air Carrier
Operating under: Part 121
Mission: Passenger
Aircraft component: Normal Brake System
Component problem: Design; Malfunctioning
Reporter organization: Air Carrier
Reporter function: Technician
Reporter qualification: Maintenance Airframe; Maintenance Powerplant
Human factors: Communication Breakdown; Time Pressure; Other / Unknown
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Maintenance
When detected: Routine Inspection
Result: General Maintenance Action
Contributing factors: Aircraft; Human Factors; Manuals
Primary problem: Human Factors

Narrative: On our air carrier B757s there are two kinds of brakes installed on the aircraft; both with the same part number. There is one kind; which is prone to cracking; I presume due to heat distress; and one that isn't prone to cracking. Most aircraft are slowly getting the type that doesn't crack; but there are still many of the type that does crack installed on the fleet. At about mid-morning; I was assigned to ride brakes on a Boeing 757; which was being moved from one gate to another at the terminal. I started my walk-around and noticed that this aircraft had one of the 'bad' brakes installed. I bent down and saw a crack in the brake; I then took a closer look and saw more cracks. Later on that day I went to deliver another 757 from the hangar to the terminal; aircraft at approximately one hour later. This too had a cracked brake; so I informed management. I was then informed that had I not been going to lunch; that I would be changing that bad brake. After lunch; and several aircraft later; I was again given another 757 to deliver. This aircraft too I viewed as having a cracked brake installed; with several of the cracks visible. The word was then passed to the Manager on duty; who came running out and informed me in no uncertain terms that I shouldn't be looking at that part of the brakes; and the walk-around I was doing was too detailed. He told me; I shouldn't be bending down to look through the spokes on the wheels; and only a general inspection should be performed to look for obvious damage. The Manager on Duty also informed me; that as I had found it; I would be changing it; and they'll get someone else to 'ride brakes'. He then told me [that what] 'I'm doing is a disservice to the night shift guys; and the overtime mechanics.'  I set about to change the brake; which; it turns out; had five cracks in it. The new replacement brake from stock showed up; but this too was of the 'cracking type' and indeed had five cracks in it also.  Of note: this new one had an airworthiness tag on it. It was only upon the delivery of a second brake from stock; was I able to use it to replace the bad brake on the aircraft; as this newer one was the type that doesn't crack. I was also informed by the manager on duty; that three guys on night shift would be getting company letters; a form of discipline; as a result of my diligence. Today I was informed by another member of the management compliance team; a Mr. X; that my inspections are too detailed and [that I] should not be looking that closely; and bending over to look at brakes; [because that] was not what a 'general' inspection should be covering. The next day I was also given the brake Manufacturer's maintenance manual showing that cracks are permitted. Unfortunately I don't have any way of accessing this manual; nor does anyone else except; it seems; the manager of the brake shop. Our air carrier Maintenance Manual does tell me to look for cracks when the wheel is off; the compliance manager told me that 'The statement; when the wheel is off would be my out at a hearing.'

Callback: Reporter stated his Management was trying to make him feel guilty for finding cracked brakes that other mechanics had missed. His Supervisor showed him a Component Maintenance Manual (CMM) from the brake Manufacturer (MFG) that said cracks in the backing plates from lighting holes was acceptable. But he could not sign-off the cracked brakes because his air carrier's Maintenance Manual (M/M) says no cracks allowed.Reporter stated his air carrier revised their M/M to allow cracks in the shaded areas on the Brake Assembly. The MFG has re-designed the B757 Main Landing Gear (MLG) brake with a heavier (thicker) backing plate supposedly to handle the brake's heat buildup.  Letters of discipline to the three mechanics for missing the cracks were rescinded; since their company revised their M/M.



Synopsis: An Aircraft Maintenance Technician (AMT) reports that after finding numerous cracks on several B757 Main Landing Gear (MLG) brake backing plates; he was informed he should not be looking at that part of the brake during his walk-arounds. His air carrier Maintenance Manual (M/M) did not allow any cracks; but the Brake Manufacturer did.