Prescott, AZ, USA
N44AZ
Thomas D. Parkes Lancair ES
The airline transport pilot was departing in the experimental, amateur-built airplane. During the initial climb, the engine experienced a partial loss of power. The pilot performed a precautionary landing on a taxiway, during which the airplane departed the paved surface and the nose landing gear collapsed. Postaccident examination of the engine turbocharger revealed reddish-white discoloration of the turbine wheel, which suggested excessive engine exhaust gas temperature. Likewise, discoloration observed on the turbine end shaft journal was consistent with high temperature. The combination of high exhaust temperature and the rotational speed of the turbine wheel likely caused the blade material to creep and the wheel diameter to increase until the blade tips rubbed against the turbine housing. This eventually caused blade tip failures, which resulted in a rotating imbalance. It is likely that the combination of wheel rubbing and imbalance and caused the turbocharger to slow or stop, which in turn resulted in the loss of engine power. The reason for the excessive engine temperature could not be determined during the investigation based on the available information.
On March 10, 2016, about 1533 mountain standard time, a Thomas Parkes Lancair ES, N44AZ, was substantially damaged following a forced landing due to a reported partial loss of engine power at Ernest A. Love Field (PRC), Prescott, Arizona. The airline transport pilot, the sole occupant and owner of the airplane, was not injured. Visual meteorological conditions prevailed for the proposed local flight, which was being operated in accordance with 14 Code of Federal Regulations Part 91, and a flight plan was not filed. The flight was originating at the time of the accident.In a report submitted to the National Transportation Safety Board (NTSB) investigator-in-charge (IIC), the pilot reported that as he advanced the throttle for takeoff he checked the initial engine acceleration, which appeared to be normal and smooth; manifold pressure (MAP) was set at 31 inches, with normal turbocharger spool-up noted as the secondary injectors cut in during acceleration. The pilot opined that this was a normal turbo-normalized installation with a manual waste-gate spring loaded to 5 psi. The turbo relief valve was set for a maximum MAP of 3.2 psi to provide sea-level power at PRC's elevation of 5,000 ft. The pilot reported that he lifted off about 75 to 80 knots (kts) with the engine running smoothly, but acceleration seemed to taper off as the airplane approached 100 feet above ground level. The pilot stated that the MAP was still reading 31 inches, but he needed to reduce his pitch attitude slightly to maintain 80 kts. The pilot further stated that previous experience had led him to expect a vigorous rate of climb with a manual reduction in propeller rpm, but at this point he realized that the engine had a power issue, at which time he pushed the throttle full forward. The pilot reported that he had sufficient runway to land the airplane, but without sufficient runway to stop before contacting a berm at runway's end. Additionally, he realized that there was a self-serve fueling station in his path, which prompted him to make a slight left turn in order to line up for a precautionary landing on taxiway Charlie. However, as the taxiway began slowly rising in the windscreen, he quickly altered the turn, lowered the flaps, and landed on the edge of taxiway Bravo adjacent to the ramp, missing all aircraft that were tied down in that area. The airplane quickly ran out of ramp area and impacted the rough terrain approaching taxiway Foxtrot. The pilot stated that the airplane bounced a few times before the nose gear collapsed and skidded across runway 12, coming to rest upright in the grass just beyond the runway. According to the pilot, the nose landing gear, propeller, cowling, and firewall were damaged as a result of impact with a newly installed Precision Approach Path Indicator's four vertical pipes, control boxes, and lights. A Federal Aviation Administration (FAA) aviation safety inspector's postaccident examination of the airplane revealed a compromised engine mount and damage to the firewall. On April 26, 2016, the NTSB IIC met with the pilot/owner at his hangar at PRC to discuss the accident, as well as to perform a cursory inspection of the engine. During the inspection, the IIC observed that the engine's crankshaft rotated freely, with no binding noted. No indications of a catastrophic engine event was observed. The pilot stated that he did not feel that there was a problem with the engine itself, however, that the issue centered around the turbocharger (serial number CCN00246, OEM part number LW-12689, part number 406610-9020). An external examination of the turbocharger revealed hard scraping on the hot side, two blades were observed chipped, two additional blades were cracked, and the impeller was tight. The pilot reported that he initially purchased the engine in 1999 from Atkins Rotary, located in Eatonville, Washington, and that there were no historical records available for the engine. The pilot subsequently installed the turbocharger to the engine, with its first flight being in 2003. The NTSB IIC had the turbocharger removed from the engine, retained custody of the component, and on May 5, 2016, shipped the component to the facilities of Hartzell Engine Technologies, Piqua, Ohio, where a detailed examination and analysis would be performed. On May 20, 2016, under the supervision of a FAA aviation safety inspector assigned to the FAA's Cincinnati Flight Standards District Office, Cincinnati, Ohio, a Hartzell Engine Technologies technician performed an examination of the subject turbocharger. The technician's findings revealed that the turbine wheel and blades had indications of being overtemped (EGTs greater than approximately 1,650 degrees F) and possible overspeed. The technician revealed that the reddish-white discoloration of the turbine wheel suggested excessive exhaust gas temperature, and that the discoloration of the turbine end shaft journal was consistent with excessive temperature. The technician reported that a combination of high exhaust temperature and wheel speed caused the blade material to creep (high temperature plastic deformation), and wheel diameter to increase until the blade tips rubbed against the turbine housing. The technician also reported that blade tip rub and creep eventually caused blade tip failures, which resulted in a rotating imbalance that damaged the compressor-bearing bore, compressor wheel rub, and introduced debris/particles into the oil bearings. The technician concluded that a combination of imbalance and wheel rub likely resulted in the turbocharger rotation to slow or stop, and thus the resultant loss of boost and engine power. (Refer to the Hartzell Engine Technologies Turbocharger Examination Findings report, which is appended to the docket for this accident.) During the investigation, the pilot revealed that the airplane was equipped with an EGT gauge that would alert him when the temperature exceeded 1,600 degrees F. However, during the accident sequence he did not observe an overtemperature warning light, nor did he know when the temperature probe was last calibrated. Additionally, the pilot reported that since the accident occurred, he had sent the engine to a repair facility, which to date has not been able to determine what precipitated the overtemperature condition.
A partial loss of engine power due to an over-temperature event, which thermally damaged the blade tips of the turbocharger wheel and resulted in a slowing or stoppage in the rotation of the turbocharger.
Source: NTSB Aviation Accident Database
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