2009-10 · NASA ASRS report 854582
Two Mechanics report difficulty in getting a DHC-8-Q400 right Main Landing Gear (MLG) Stabilizer Strut Brace (H-member) to lock in the 'Down' position manually or with the Alternate Extension hydraulic pump.
I received a turnover from graves; on the disassemble of the right hand (R/H) MLG Stabilizer Strut ('H' member); to perform Non-Destructive Testing (NDT); then a reassemble after NDT. After Inspection was finished with the NDT; I had begun the reinstall of the 'H' member using the original hardware and after removing the parts from the parts bags tied to the correct location from the removals; there were two washers attached to both Stabilizer Brace pins; one small thin washer still coated with grease attached to the head of the bolt; and a larger one which went on the nut side. Both bolts had the exact same stack ups. During installation; I installed the bolts the only possible way that they could be installed; since the 'H' member had an anti-rotation tab on it to prevent the bolt from spinning. I left the smaller washer on the head side of the bolt; which still allowed the anti rotation tab to work; and the larger washer under the nut; torqued and safetied; by Inspector. Then I turned over the rest of the install to swing shift. The operational checks of the gear was not complied with until day shift the following day; when they realized the R/H gear was not locking 'Down' during the Alternate Extension Operations Check; even after attempting to pump it to the 'Down' and locked position. I then went over and told them I had put it together the day before and explained to them what I had done. Mechanic realized that the washer on the nut side was tight; and that as far as he knew; it wasn't always tight after torquing; and that it maybe was over torqued; binding it up and not allowing it to lock 'Down.' When he took it apart to do a re-torque; he noticed the washer under the head side of the bolt; that he didn't remember ever seeing there before. I told him I wasn't sure if it was installed for shimming purposes; but they were there during removal. They looked it up in the Component Maintenance Manual (CMM); and it did not show the washer. We looked at the left hand (L/H) gear and there were no washers under the bolt head; so they removed the washer and re-torqued; performed the Operational Check and it passed. That's when I found out that; there shouldn't be a washer under the head of the bolt; even after flying in that way. I then walked over to the aircraft I was working on; for a clarification and realized that the L/H gear on another -Q400 (aircraft Y); also had washers under the heads of both stabilizer bolts; this is when the big question came up. So we all confronted Leads and Supervisors of the problem. Because someone else had installed it incorrectly prior to my reinstall of original hardware.
In the morning; two other mechanics and myself were doing Main Landing Gear (MLG) swings and MLG door Fit and Fare Checks on a DHC-8-Q400; (aircraft X). When we came to the Alternate Extension part of the Check; the right hand gear failed the check because the gear would not lock in the 'Down' position; either Manually or with the Alternate Extension hydraulic pump. After attempting the Operational Check a few times; we re-torqued the pins (Illustrated Parts Catalog IPC 32-11-16 fig.1 pg.2 item 30) on the Stabilizer Brace assembly to ensure they were reinstalled correctly. After we re-torqued the bolts; the right hand MLG still failed the Alternate Extension Operations Check. At this time I went to the left hand gear and looked at the Stabilizer Brace assembly to compare with the right hand side. I noticed that the left hand gear side pins (IPC 32-11-16 fig.1) had two threads protruding from the nut and the right hand side only had one thread protruding out past the nut. Then I looked closer at the right hand gear side and noticed washers under the head of the pins that were not present on the left hand side. This washer is not shown in the IPC; or in the Component Maintenance Manual (CMM); under the head of the pin (IPC 32-11-16 fig.1). We removed the washers from the right hand side and reinstalled and torqued the pins. Then we performed another Alternate Extension Check that; this time; the MLG passed. After all the paperwork was done it was brought to my attention that another -Q400 (aircraft Y); just in for Special Federal Aviation Regulations (SFAR) modifications (mods); left hand gear also had washers installed under the pins on the Stabilizer Strut. At this time; Mechanic Z and I gathered some references together and proceeded to go upstairs and inform the day shift Supervisor; swing shift Supervisor and Heavy Check Manager what we had found.I am not exactly sure why the extra washers were placed under the head of the pin. In my opinion it could be partially caused by the Mechanic looking at the IPC 32-11-16 fig.1 pg.2 and becoming confused with the illustrations and installing the washer under the head of the pin where it should not be.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.
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