B767 Undifferentiated or Other Model
Maintenance Airframe; Maintenance Powerplant
Maintenance Technician 15
Situational Awareness; Training / Qualification; Confusion; Troubleshooting; Communication Breakdown
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
General Maintenance Action
Aircraft; Chart Or Publication; Procedure; Manuals; Human Factors; Company Policy
While performing lock-out procedures to 'Install Elevator Power Control Actuator Lock Tool' per Aircraft Maintenance Manual (AMM) 27-31-05-022-001; I misunderstood the procedures as they were poorly written. I installed the lock tool on the [Power Control] Actuator (PCA) with hydraulics 'On' and elevator full 'Up'. When I told my Partner on the flight deck to slowly lower the elevator; the lock tool was damaged. I immediately told my Partner to stop and hold the elevator back; [to] full 'Up'. I removed the damaged lock tool and inspected the PCA for damage. No damage was found. Realizing I was doing something wrong; I called my Supervisor and asked for assistance. He sent out a Lead Technician who agreed with me that the procedures were poorly written. He assisted me in correctly installing another lock tool. The Lead submitted a publication change request to improve the procedures and safety. The broken lock was reported to the Tool Room and the plane flew two days later without incident. There is an unfortunate mindset among mechanics that they should know how to do every job; even ones they have never done before; without asking for help. This particular Supervisor belittled me when I asked him to send someone out to help. 'You need help installing a lock on an actuator?' were his exact words. I didn't care and I'm glad I did; as it avoided costly damage to the aircraft. Lack of experience in task.
As a Lead Technician; I was called to assist two mechanics that were having difficulty installing the Elevator locking tools on a B767 per Aircraft Maintenance Manual (AMM) 27-31-05 (the locks prevent movement of the elevator control surface; during routine maintenance). Prior to my arrival; Aircraft Maintenance Technician (AMT) # 1 was on a lift truck at the [aircraft's] tail section and AMT # 2 was in the cockpit. A brief examination of the Control Lock Tool that was previously installed on the Center Power Control Actuator (PCA) revealed deep gouges into the tooling. When inquiring AMT # 1 [as to] what happened; he said that he had installed the lock with the elevator control surface positioned in the nose-up condition. However; when he asked AMT # 2 to release the Control Yoke; the Elevator PCA overcame the Control Lock and pushed it over the threaded end of the horizontal bolt that attaches the elevator's middle [Center] PCA rod end to the aircraft structure. Fortunately; according to AMT # 1; no damage was done to the aircraft when the tooling slipped off. When asked if the hydraulic pressure was applied at the time of Control Lock installation; he responded in the affirmative. Reviewing the paperwork revealed that the initial steps of the procedure require that Hydraulic Systems are depressurized and the Tail Hydraulic Switches are moved to the 'OFF' position. However; later in the procedure; it states to move the Control Column to the full Aft limit and then to simply install the actuator lock tool. It does not state how to install the lock; it merely refers you to Figure 201. The procedure does not explain that by moving the column Aft with hydraulics systems depressurized; hydraulic fluid will bypass to return; allowing the AMT to lift the elevator by hand; and thereby allowing access to install the locks. The AMTs were convinced that the only way to install the lock was to pressurize the hydraulics and move the elevator surface up [using the Control Column]. This is very dangerous!! If the Control Column is relaxed while attempting to install the locks; severe bodily injury is imminent. Further review of the procedure revealed that there [are] two distinct different types of locks. However; the same Nomenclature and Part Number (P/N) are used for each (Elevator Actuator Lock; SPL-12766). The first lock to be installed is actually a Bushing Assembly Lock that is installed on the elevator middle bellcrank with a pip-pin to prevent input rod movement to the bellcrank. The other type of lock is a Flat Plate Lock with 'U' bolts that is attached to the PCA to keep the elevator from sagging down while work is accomplished. The PCA locks are installed at two or three different locations; depending on what type of maintenance is being accomplished. It was not until re-reading the procedure several times that I realized the locks the AMTs were attempting to install were out of sequence; because the bellcrank Lock had not yet been installed. It is my opinion that the paperwork requires revision to accomplish the following:#1) Early in the procedures; warn the AMT of the dangers of installing the locks with hydraulic system power applied and prohibit the AMT from accomplishing the same.#2) Clarify the lock-out tool part numbers and be more specific regarding the location and purpose of each.#3) Re-arrange the sequence of events so that the Control Column is not released until all of the applicable locks are installed. Although the systems are depressurized when accomplished correctly; the elevator begins to creep downward as soon as the person in the cockpit releases the control column. Changing this sequence would prevent the elevator from sagging until all personnel and equipment are clear. I have made recommendations to our Engineering Department and expect that Boeing will implement the changes at the next manual revision.
A Mechanic and a Lead Mechanic describe various factors that contributed to an Elevator Power Control Actuator lock-out tool being installed incorrectly on a B767 aircraft.