Accident Overview
On April 13, 2022, at 0704 mountain daylight time, a Cirrus Design SR22 airplane, registered as N112TR, sustained substantial damage during an accident near Twin Lakes, Colorado. The pilot, the sole occupant, reported minor injuries. The flight was conducted as a personal flight under Title 14 Code of Federal Regulations Part 91.
Pilot's Account
The pilot stated that after leveling off at 17,000 ft msl, he requested and received clearance to climb to FL210 and then FL230 to remain above cloud tops. The climb segments were performed at full power and full rich mixture with the fuel pump set to low boost. During the climb from FL210 to FL230, the pilot observed a brief alternate air indication on the primary flight display; engine performance remained normal. Upon leveling, he reduced power to about 65% to 75% and adjusted fuel flow, and the indication extinguished. The pilot noted that he had seen this indication before and typically reduced power slightly to clear it.
At approximately 0657, the pilot noticed a drastic reduction in engine power to 10%–15%. He immediately set the mixture to full rich and the fuel pump to high boost, then adjusted the power lever without effect. During the subsequent descent, the flight reentered instrument meteorological conditions. After declaring an emergency with Denver Center and establishing best glide airspeed, the pilot turned toward a valley east of his position. Around that time, smoke entered the cabin, and he concluded that restarting the engine was unlikely. As the airplane descended through the minimum safe altitude for the mountainous area, a terrain indication appeared on the multi-function display. The pilot then set the mixture to idle/cutoff and deployed the Cirrus Airframe Parachute System. After the parachute fully deployed, he turned off the electrical system and secured the cabin for touchdown, contacting the ground hard a few seconds later. The airplane came to rest upright in a mountain valley with rocky terrain and low brush. The left wing was damaged at the main landing gear mounting point during the parachute-assisted touchdown.
Postaccident Examination
A postaccident examination of the engine revealed no anomalies. The induction air filter and ducting were intact and unobstructed. The alternate air door in the induction system remained closed when magnetically latched but opened with applied pressure. The right turbocharger assembly was intact and unremarkable. The left turbocharger exhibited curled compressor vanes with corresponding scraping damage on the housing inlet, consistent with contact while rotating. The turbine vanes were intact with no scraping, and the shaft rotated freely with slight axial play.
Engine Data Analysis
Data from the recoverable data module showed several distinct reductions in engine power before the final loss. Around 0636, engine speed dropped from about 2,625 rpm to 2,460 rpm with corresponding decreases in manifold pressure and fuel flow, lasting about two minutes before recovery. This event coincided with leveling at 17,000 ft msl. A second reduction occurred around 0641 during the climb to FL210, lasting about one minute. A third reduction around 0644 lasted about nine minutes and coincided with leveling at FL230. At 0657, a final loss of power occurred: exhaust gas temperatures dropped from 1,300–1,400°F to about 150°F, turbine inlet temperatures dropped from about 1,550°F to 150°F, manifold pressure fell from 30 in Hg to 11 in Hg, and fuel flow initially dropped from 35 gph to 9–15 gph before increasing to about 25 gph. The airplane descended from FL230 to about 16,500 ft msl, and airspeed decreased from 125 knots to 100 knots. From 0659 to 0703, intermittent recovery attempts were observed, but the engine ultimately lost power when the pilot shut it down for CAPS deployment.
Aircraft System Limitations
The airplane was equipped with a turbonormalizing system featuring a magnetically latched alternate air door. According to the Pilot’s Operating Handbook supplement, the door may become unlatched during unusual engine power surges at high altitude, and can be relatched by momentarily retarding the throttle. The Airplane Flight Manual supplement includes the limitation: "Do not reduce manifold pressure below 15 inches when above 18,000 ft msl." The emergency procedures for unexpected loss of manifold pressure advise adjusting power to the minimum required for continued flight and adjusting mixture to maintain exhaust gas temperatures between 1,300°F and 1,400°F. Additionally, the abnormal procedures warn that retarding the power lever to idle at or near full rich mixture above 18,000 feet may cause engine combustion to cease, and that using high boost with the power lever near idle may prevent engine restart.