Ravendale, CA, USA
N420WT
Textron Aviation TTX Inc. T240
The instructor pilot reported that during takeoff about 100 ft above ground level (agl) and near the end of the runway, the engine sustained a sudden loss of engine power. The pilot lowered the nose and extended the flaps for the off-airport forced landing. The airplane impacted the snow-covered terrain. Postaccident examination of the airplane indicated that the right induction tube connecting the turbocharger compressor outlet to the intercooler inlet had separated from the turbocharger compressor outlet flange. Two inches of the induction tube was installed into the 3-inch-long rubber coupling, leaving only 1 inch remaining to be installed on the turbocharger compressor outlet flange. It is likely that when the engine was at high RPM during the takeoff climb, the improperly installed lower rubber coupling separated from the turbocharger compressor outlet flange, resulting in the loss of engine power. The engine was installed on an engine test stand and it ran successfully at various RPM settings. The engine test run revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Maintenance records indicated that the last 100-hour inspection was performed two days before the accident. During this inspection the induction tubes would have been removed and inspected.
On January 28, 2022, about 1443 mountain standard time, a Textron Aviation T240 airplane, N420WT, was substantially damaged when it was involved in an accident near Ravendale, California. The two pilots and one passenger onboard were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 instructional flight. The instructor pilot reported that they had flown earlier in the day and the flights were uneventful with no anomalous engine readings. During the accident flight, they conducted a go-around during the approach followed by an uneventful landing. They taxied back for takeoff on runway 17 and had planned to do a short field takeoff. The pilot reported that the wing tanks contained about 20 gallons per side and that he departed with the right tank selected. During takeoff, about 100 ft agl and near the end of the runway, they experienced a sudden loss of engine power. The instructor pilot took control of the airplane, lowered the nose, and extended the flaps for the off airport forced landing. The airplane touched down on snow-covered terrain, impacting brush as it came to rest after about 80 feet of sliding. The pilots and passenger egressed the airplane and the fuselage sustained substantial damage. The airport elevation at O39 is 5,306 ft above mean sea level (msl) and the density altitude at the time of the accident was calculated to be 5,084 ft msl. A video recording with sound was provided by the pilot and it showed an over-the-shoulder view of both front seat occupants of the airplane. The video showed the airplane traveling down the runway and then the airplane starting to pitch up. The left-seated instructor pilot stated, “yeah pull it off come on.” As the instructor pilot called for rotation, the primary flight display (PFD) displayed a yellow caution message, and a tone was audible. The PFD annunciated in yellow: STALL WARN COLD PITOT COLD. The yellow caution remained for the rest of the recording until the camera’s view was changed at impact. As the airplane began to climb out there were no anomalies noted on the multi-function display (MFD). The airspeed increased to 80 knots and the airplane continued to climb and accelerate. The PFD showed the pitch attitude was about 14° nose up at an airspeed of 85 knots and an altitude of 5,300 ft msl. Soon after, the manifold pressure, RPM, and exhaust gas temperatures (EGT) for all cylinders began a rapid decrease. At this time, the airspeed was about 87 knots and the airplane’s pitch attitude was about 12.5° nose up. The instructor pilot took control of the airplane and entered a left bank and began flying toward a gravel road. The PFD showed the airplane was about 10° nose up, in about a25° left bank, at an airspeed of 74.5 knots, and at an altitude of 5,370 feet msl. The pilot brought the airplane to wings level as the airplane approached the gravel road and he flared the aircraft before impacting the terrain. During the postaccident examination of the wreckage, the right induction tube, which connects the turbocharger compressor outlet to the intercooler inlet, was found separated from the turbocharger compressor outlet flange. The examination revealed that two inches of the induction tube was installed into the 3-inch-long rubber coupling, leaving only 1 inch remaining to be installed on the turbocharger compressor outlet flange. The lower rubber coupling, and band clamps remained attached to the induction tube. A required heat shield was not attached to the lower clamps. Figure 1.Right side induction tube and rubber coupling. The left side induction tube connecting the turbocharger compressor outlet to the intercooler inlet remained attached to both. The required heat shield was attached to the lower clamps. The engine was installed on a test stand and it ran successfully at various RPM settings. The engine test run revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Maintenance records indicated that the last 100-hour inspection was performed on January 26, 2022. During this inspection the induction tubes would have been removed and inspected. Continental Motors Service Bulletin SB94-3A states the following, “WARNING…Loss of induction system coupling will result in a loss of turbo boost and subsequent loss of engine power.” According to Title 14 Part 43 Appendix D, during an annual inspection, lines, hoses, and clamps should be checked “for leaks, improper condition and looseness” and all systems should be checked for “improper installation, poor general condition, defects, and insecure attachment.”
The inadequate maintenance and inspection of the engine induction system, which resulted in the separation of the right induction tube from the turbocharger compressor outlet and the subsequent loss of engine power during departure.
Source: NTSB Aviation Accident Database
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