B737-800
Maintenance Airframe; Maintenance Powerplant
Communication Breakdown; Time Pressure
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance
General Maintenance Action
Aircraft; Procedure; Manuals
Reference FIM (Fault Isolation Manual) Task 71-06-00-810-805-F00 and AMM (Aircraft Maintenance Manual) Task 71-00-00-800-804-F00. FIM portion '(b) If you find an EGT (Exhaust Gas Temperature) exceedance on the EXCEEDANCES display; then; do this task: Inspection After Engine Operations Above the Limits and High Engine Stress; AMM TASK 71-00-00-800-804-F00.REVNOTE: NOTE: If Takeoff EGT redline limit is exceeded and Primary Engine Display for EGT is boxed in RED; the CDU Engine Exceedance Page check will display time of the exceedance beyond the transient allowance (EGT between 950-960 degrees Celsius for 20 seconds). The time displayed on the CDU Engine EGT Exceedance page should be used for plotting points on Figure 602 of Inspection After Engine Operations Above the Limits and High Engine Stress; AMM Task 71-00-00-800-804-F00 step 4.F.(3). AMM portion ('Area A' Exceedance)'SUBTASK 210-032-F00 - (20031010)(4) If the point is in area A; do the corrective action as follows:(a) Do a visual inspection of the engine inlet and engine exhaust before the subsequent flight. (b) Identify and correct the cause for the EGT over temperature at the first available opportunity. 1. Refer to the Fault Isolation Manual to find the cause. 2. If a second over temperature occurs and you have not found the cause for the first over temperature; you must find; and if possible; correct the cause for the over temperature before the subsequent flight. 3. If you have found; but not corrected; the cause for the first or second over temperatures; you can have 10 more over temperatures in area A before you must correct the cause.'AMM portion ('Area B' Exceedance)'(5) If the point is in area B; do the corrective action as follows:(a) Do a visual inspection of the engine inlet and the engine exhaust before the subsequent flight. (b) Identify and correct the cause for the EGT over temperature at the first available opportunity. 1. Refer to the Fault Isolation Manual to find the cause. 2. If a second EGT over temperature occurs and you have not found the cause for the first over temperature; you must find; and if possible; correct the cause for the over temperature before the subsequent flight. 3. If you have found; but not corrected; the cause for the first or second EGT over temperatures; you can have 10 more over temperatures in areas A and B before you must correct the cause of the over temperature. (c) If you cannot find the cause for the over temperature; do these steps before the subsequent flight: 1. Do this task: HPT (High Pressure Turbine) Blades Borescope Inspection; TASK 72-00-00-200-807-F00. 2. Do an inspection of the Stage 1 LPT (Low Pressure Turbine) blades. To do this inspection; do this task: Stage 1-3 LPT Blades Borescope Inspection; TASK 72-00-00-200-808-F00. 3. You can defer the borescope inspections for up to 10 cycles if no more over temperatures occur. 4. Do this task: Test 5 - Power Assurance Check; TASK 71-00-00-700-813-F00. 5. If you have found; but not corrected; the cause for the first or second EGT over temperatures; you can have 10 more over temperatures in areas A and B before you must correct the cause of the over temperature. (d) If you cannot correct the cause for the EGT over temperature on-wing (this includes engine deterioration); do the next step. (e) You can have a maximum of 10 EGT over temperatures in areas A and B together before you must remove the engine for an EGT over temperature inspection. These are the tasks:Power Plant Removal; TASK 71-00-02-000-801-F00;Power Plant Installation; TASK 71-00-02-400-801-F00.NOTE: Use the CFMI Engine Shop Manual to do an inspection of the removed engine. 'Crew reported on shutdown both engine EGT indicators went red box with no actual temp. I spoke with outbound Captain; who informed me the inbound Captain stated the exceedance was most probably on takeoff; as there were no flight deck effects. I stated the exceedance warnings are inhibited on takeoff. I then retrieved exceedance data in accordance with AMM. Spoke with [the Crew Chief]; and we agreed that FIM required more than just inlet/exhaust inspection. Per AMM figure 6 chart; I considered Engine 1 an Area B exceedance; and Engine 2 and Area A exceedance. My logic is the AMM figure 602 has a thick line near the mid-point between 960 and 970 degrees; reasonably about 1 degree in temperature width. The next step was to utilize the FIM to determine the cause of the exceedance. Management at Terminal called aircraft out of service; rightly in my opinion; for further troubleshooting. Terminal Manager asked me and [the Crew Chief] to provide our findings and info to the Hangar manager and [Crew Chief].We spoke with a Hangar Manager who stated that he spoke with [Maintenance Control] who said the engines were 'good' and just needed an inlet/exhaust inspection and then a [more thorough inspection] to be accomplished later. I disagreed; and suggested that if he felt that way then manager could fly that [Maintenance Controller] up to sign off the AML. I then explained that the FIM required not just an inlet/exhaust inspection; but additional FIM work to determine the cause of the exceedance on each engine. Hangar Manager attempted to pressure me into accepting that this part could be deferred. I did not back down and explained that I saw no authority with the AMM/FIM to defer this work. Manager then indicated we should have done the 'Identify and correct the cause for the EGT over temperature at the first available opportunity.' portion of the AMM on overnight. I expressed my opinion that right now was a really good opportunity to evaluate the condition of the engines (AMM is not 100% clear on what 'first available opportunity' actually means; but I read this to mean the first time the aircraft is at a station with manpower and ability available; which would be right now). I later checked [our maintenance tracking software] and it appears the 'Identify and correct the cause for the EGT over temperature at the first available opportunity.' portion of the AMM requirement was either not accomplished on overnight; or was deferred; with the [Maintenance Controller] creating [logbook deferral] items to accomplish that portion of the AMM expectation for each engine. I do not see any authority for this deviation; in the form of an Engineering Authorization or other process.I am deeply concerned that the perception of many in management is still too focused on 'operational need' and not enough focus on the trained and FAA agreed to concepts of in accordance with and those compliance expectations. The AMM in this instance created a built-in dispute over what a seemingly simply definition meant. Have company provide approved structured training; with examples like this one; to clearly explain how and what is expected within the maintenance program when these types of opaque issues arise. Clearly define what 'first available opportunity' means from Boeing and/or CFM [engines]. Define whether that line in Figure 602 is a range or exact number; and then add that info to the figure.
The reporter stated that he was told that an action item was to be taken by Engineering to clarify the language in the maintenance manual. Presently nothing has changed yet. The reporter also stated as far as he knew the engines are still flying.
Aircraft Maintenance Technician reported that when B737-800 CFM engines exceed EGT limits. The AMM is not clear when the high pressure turbine EGT inspection is required to be accomplished.