Date: 201403
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: EC145
Operator: Air Taxi
Operating under: Part 135
Mission: Ambulance
Flight phase: Parked
Aircraft component: Turbine Engine
Component problem: Malfunctioning
Reporter organization: Air Taxi
Reporter function: Technician
Reporter qualification: Maintenance Powerplant; Maintenance Airframe
Human factors: Communication Breakdown; Confusion; Troubleshooting
Second reporter function: Lead Technician
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew; Person Maintenance
When detected: In-flight
Result: Flight Crew Inflight Shutdown; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Company Policy; Aircraft; Human Factors; Weather
Primary problem: Human Factors

Narrative: The original discrepancy was # 1 Engine overspeed and shut down on approach to roof top helipad of hospital. Upon landing; Pilot X; the on-duty pilot; called our Lead Mechanic (Lead Mechanic X). He informed Lead Mechanic X of what had occurred. Lead Mechanic X called me early evening and informed me to gather tools and head toward the hospital. During travel; I was in touch with Lead X who informed me that he was in contact with our Regional Manager. Lead X briefed me prior to arrival of what he and the Regional Manager came up with for me to begin trouble shooting engine shut down cause. Upon arrival; I met and was briefed by Pilot X as to what had transpired. I proceeded to complete task that was relayed to me. I performed a complete Visual Check of Engine and Airframe with no defects noted. I notified Lead X and was told to have Pilot X start # 1 Engine and to monitor the engine indications for erratic indications of abnormalities. After engine start; there were no issues. I proceeded to do Power Check; Beep Checks and Engine Overspeed Checks with no faults or discrepancies. After runs; I was able to get someone in the hospital to log me onto a computer and I researched in the BK-117 Maintenance Manual (M/M) Engine Overspeed Inspection and found that there was no inspection listed. I was then told to finish with that for the night and that Lead Mechanic X and the Regional Manager were going to call the Honeywell Engine Technical Representative the next morning. The next morning I contacted Lead X and he told me he was in contact with Technical Representative and that the Representative would get back on how to proceed. Approximately mid-day; I was told to report back to the hospital and meet up with Lead Mechanic X. I diverted to our Company Base 145 Repair Station ZZZ1 and acquired an engine governor and fuel control that I was told is what the Technical Representative wanted us to inspect/change. When I arrived; Lead X was in the process of removing the governor per the Technical Representative. Lead X then installed the governor I had brought. We then leaked check the Engine Air System and reinstalled the cowl to prepare for engine run. Lead Mechanic X and Pilot X ran the aircraft and performed Beep Checks which were found to be within limits. Lead X was then in contact with the Regional Manager and the Engine Manufacturer Technical Representative. The final word was sign-off the work that was performed and release the aircraft back to ZZZ airport; due to weather inbound and the fact that we had scheduled inspections that we were planning on doing the next day in the hangar under weather. The aircraft was flown to ZZZ1 for refuel where we informed Pilot X to wait for my arrival. I arrived at ZZZ1 Repair Station did a Visual Check of the # 1 Engine; no discrepancies noted. Pilot X then returned back to ZZZ Airport and put the ship in the hangar. The next morning; Lead Mechanic X and I arrived and began to do the scheduled inspection. Throughout the day Lead X was fielding calls about what had happened and I was researching answers to the questions. While researching; I found in the Honeywell LTS 101-B Engine Maintenance Manual (M/M) an Inspection Checklist for Engine Overspeed. I informed Lead X and we reviewed the checklist and found out that the engine required Topping and a Dye Penetrant (Pen) Inspection of the turbine wheel; all of which had not completed before I returned the aircraft to service the prior evening. We relayed the info to the Regional Manager. After more research and calls to technical representatives; we found out that the Dye Pen Inspection [procedure] results in an engine change due to the level of dye penetrant required by the Manual. We have ordered the parts to change the engine. When we informed the Regional Manager what had happened; he told us to complete this form. [Recommend] we receive better back support from the Regional Manager or Aircraft Maintenance Manual (AMM) when inareas that have limited; to no internet access. I should have slowed down and asked more questions about what was researched instead of taking for granted that all other parties involved had already made sure I was covered; in the maintenance I was told to perform. In hindsight; I should have pushed the issue of limited; to no internet access and made sure someone had researched the Engine Manual; as I had already researched the Airframe Manual myself. Flight canceled. While reading manuals the next day at maintenance hangar for the root cause of engine shut down; due to no internet at hospital helipad; found checklist for overspeed.

Callback: Reporter stated he has 14-years experience on Eurocopters. The BK-117 is a proven workhorse for a helicopter; when properly maintained. The on-duty pilot originally reported the # 1 Engine went to overspeed and all the needles went 'Sky-high'; before the Honeywell LTS 101-B Engine shutdown in-flight; approximately 200 FT above the hospital helipad. The Engine Overspeed Control Unit (OCU) was suppose to oscillate the engine below max speed; preventing an overspeed and than stabilize the power until a control input was initiated. The Engine Manufacturer and OCU Computer Manufacturer said that failure of the OCU was not uncommon. The overspeed unit; governor and fuel control were sent out for analysis and found Serviceable. The collective handle controls both engine governors through the engine fuel control units by using engine bleed air as muscle; to 'push' the fuel control units. Reporter stated that since they could not duplicate the same conditions reported by the On-Duty Pilot and the Dye Penetrant (Dye-Pen) Inspection would require removing the turbine disc; his Air Carrier decided to replace the engine.

Second narrative: March 2014; early evening; local time; I received a phone call from our Duty Pilot; Pilot X; who was on a flight into a hospital landing pad. I was advised that # 1 Engine went into Overspeed and than; Offline 200-300 FT AGL while on final approach; uneventful landing. We discussed the event and I immediately contacted Supervisor X and soon after; the Regional Manager. On-call Mechanic X was dispatched to the helicopter and instructed to visually inspect the airframe; engines and if no issues noted to start # 1 Engine and perform Power Check; Beep Range Check and Overspeed Check. The same checks were accomplished on the # 2 Engine; with no defects found on either engine. The following morning; I contacted Honeywell [Engine] Technical Support Representative to discuss the event and provided him a copy of the pilot's report. After many discussions between our Air Carrier personnel and Honeywell; it was recommended by the Technical Representative that the PT Governor should be changed and air lines Leak Checked. The tasks were completed; and the aircraft was repositioned to ZZZ1 for fuel; then relocated to ZZZ airport and hangared for other scheduled maintenance the following day. The following morning we started the scheduled maintenance and throughout the day; between phone calls and more research into the engine shutdown; we discovered and confirmed through the Technical Representative Honeywell; that the Overspeed Inspection requirements were not mentioned or followed in the Honeywell Maintenance Manual (M/M). There was discussion throughout the day about one of the required inspection items with the Honeywell Technical Representative; and also with a Representative from an Engine Turbine Repair Station; whether or not the Power Turbine (PT) wheel Non-Destructive Testing (NDT) applied to the solid PT disc or the segmented PT disc and was determined that the inspection applied to either disc. I contacted the Regional Manager and we discussed how I missed the additional inspection requirements and started planning the repairs.The aircraft being parked on top of the hospital; blocking their [vehicle] parking pad; needing to get their pad cleared and the forecasted snow arriving early the following morning; may have played a part in not double checking and researching the policies and manuals to make sure nothing was missed; as is normally accomplished. The technical support we received was greatly appreciated and helpful; but I took the information for granted; since no other special inspections were mentioned; [that] we were good to go. I understand it is my responsibility to ensure all procedures are followed before the aircraft is returned to service. I have learned from this event not to let stress levels elevate to the point where it may cloud your judgment and to ask for additional help when conditions as this happen. Found other inspection criteria while reviewing follow up paperwork.


Synopsis: Two Aircraft Maintenance Technicians (AMTs) describe factors that contributed to their not accomplishing an Overspeed Checklist after a BK-117 Eurocopter pilot reported the indicator needles on #1 Engine had gone 'Sky-high.' The Honeywell LTS 101-B Engine had shut down inflight; approximately 200 FT above a hospital helipad.