N255JPCirrus Design SR22 · 2008

On January 21, 2024, at 1320 central standard time, a Cirrus SR22, N255JP, was destroyed when it was involved in an accident near Little Rock, Arkansas. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations (CFR) Part 91 personal flight.

The airplane was kept in an unheated hangar at Bill and Hillary Clinton National Airport/Adams Field (LIT), Little Rock, Arkansas. On the day of the accident, the pilot called a fixed-base operator (FBO) at LIT to move the airplane outside; at the time, the outside air temperature was about 28°F. When the pilot arrived, he attempted to start the airplane’s engine fourteen times, then ceased further attempts because the battery died. The pilot’s flight instructor stated that he received text messages from the pilot asking, “Tricks for starting the cirrus in the cold?” and stating that the pilot flooded the engine and there was fuel on the ground. An additional message stated that the FBO was taking “forever” to get a ground power unit (GPU). After FBO personnel connected a GPU, the pilot then started the airplane’s engine after five additional attempts.

A witness, who was inside the FBO, said once the accident airplane’s engine started, the GPU was disconnected, the wheel chock was removed, and within two minutes the accident airplane started taxiing and turned onto taxiway A. He said that the pilot of the airplane did not allow the engine to warm after engine start and before taxiing. He said that typically on cold days, he must wait at least 6–8 minutes before taxiing his airplane. He did not know if the pilot of the accident airplane performed a run-up before departure. He said he did not think enough time had elapsed from the time the accident airplane’s engine was started to the time of the accident for the engine oil to have warmed up enough.

The flight took off from runway 4L and reached a maximum altitude of about 425 ft mean sea level (msl), shown in figure 1; the airport elevation was 266 ft msl. During the departure climb, the pilot transmitted that he lost the engine. The airplane entered a right bank, descended, and impacted the ground near the airport fire station.

Figure 1. Departure flight track with ground speeds and altitudes.

The investigation was unable to locate any logbooks that showed the pilot’s total experience flying turbocharged airplanes. A flight instructor provided a statement for the pilot’s airplane insurance application attesting that he provided the pilot with ground instruction and 10 hours of flight training, including 10 takeoffs and landings, in the airplane on October 3 and 17, 2023, and on January 4 and 11, 2024. The pilot reported on the application that he had logged 15.2 hours in a Cirrus SR22. The pilot’s estimated total flight times were based upon the insurance application.

The airplane was powered by Teledyne Continental Motors model IO-550-N, fuel-injected, direct drive, air-cooled, horizontally opposed, 6-cylinder, 550 cubic inch displacement engine, rated at 310 horsepower. IO-550-N engines are equipped with non-congealing oil coolers that have a vernatherm (bypass) valve, which directs oil into the oil cooler when the engine warms up to about 160–180oF; otherwise, oil is routed around the cooling fins and into the oil cooler galley.

The engine was modified by the addition of a Tornado Alley Turbonormalizing System, through a STC. The Tornado Alley Flight Manual supplement provided a turbocharger system description, which stated:

The absolute controller and wastegates work in conjunction with each other to provide proper boost pressure to the engine. The wastegate is actuated using engine oil pressure to actuate a small hydraulic cylinder which redirects the engine by-pass exhaust flow around the turbochargers. The absolute pressure controller utilizes an aneroid bellows and spring connected to a valve that regulates the amount of oil flowing out of the wastegate actuator hydraulic control cylinder. The aneroid bellows are located inside a housing that is connected to the output air produced by the compressors.

The control lines for the turbocharger system were connected to the oil cooler galley, and the engine oil temperature sensor was connected to the oil output of the oil cooler.

In the Tornado Alley Turbo Continued Airworthiness Manual for Cirrus Design SR22 Series Airplanes Turbonormalized per STC’s SA10588SC and SE10589SC, the post-engine overhaul/installation instructions noted that target fuel flow is achieved with an engine oil temperature not less than 170°F.

The Cirrus SR22 Pilot’s Operating Handbook and FAA Approved Flight Manual list engine and fuel limitations for SR22 airplanes not certified with a turbocharged engine, as shown in figure 2.

Figure 2. Cirrus SR22 engine limitations (top) and fuel limitations (bottom).

The Tornado Alley Flight Manual supplement specified changes to some of these limitations, as shown in figure 3. The oil temperature limitation was unchanged.

Figure 3. Tornado Alley flight manual supplemental limitations.

The Tornado Alley Flight Manual supplement added steps to Cirrus’s SR22 takeoff procedures, stating that engine parameters should read in the green during takeoff and manifold pressure may temporarily increase to 31–32 inches of mercury with an associated increase in fuel flow due to cooler oil temperatures. If the manifold pressure exceeded 32 inches of mercury, then the corrective response was to reduce power, shown in Figure 4.

Figure 4. Tornado Alley flight manual supplemental procedures.

The Tornado Alley Flight Manual supplement did not have a section for turbocharger emergency procedures as specified in the General Aviation Manufacturers Association (GAMA) Specification for Pilot’s Operating Handbook (GAMA Specification No. 1, Revision No. 2, October 18, 1996), which states that Revision No. 2 “incorporates NTSB suggestions for inclusion of emergency procedures for supercharger/turbocharger failure” and that “procedures shall be provided for coping with emergencies involving” turbocharger systems. Manufacturers may use GAMA Specification No. 1 to fulfill the aircraft flight manual requirements in 14 CFR Part 23.

The airplane was powered by Teledyne Continental Motors model IO-550-N, fuel-injected, direct drive, air-cooled, horizontally opposed, 6-cylinder, 550 cubic inch displacement engine, rated at 310 horsepower. IO-550-N engines are equipped with non-congealing oil coolers that have a vernatherm (bypass) valve, which directs oil into the oil cooler when the engine warms up to about 160–180oF; otherwise, oil is routed around the cooling fins and into the oil cooler galley.

The engine was modified by the addition of a Tornado Alley Turbonormalizing System, through a STC. The Tornado Alley Flight Manual supplement provided a turbocharger system description, which stated:

The absolute controller and wastegates work in conjunction with each other to provide proper boost pressure to the engine. The wastegate is actuated using engine oil pressure to actuate a small hydraulic cylinder which redirects the engine by-pass exhaust flow around the turbochargers. The absolute pressure controller utilizes an aneroid bellows and spring connected to a valve that regulates the amount of oil flowing out of the wastegate actuator hydraulic control cylinder. The aneroid bellows are located inside a housing that is connected to the output air produced by the compressors.

The control lines for the turbocharger system were connected to the oil cooler galley, and the engine oil temperature sensor was connected to the oil output of the oil cooler.

In the Tornado Alley Turbo Continued Airworthiness Manual for Cirrus Design SR22 Series Airplanes Turbonormalized per STC’s SA10588SC and SE10589SC, the post-engine overhaul/installation instructions noted that target fuel flow is achieved with an engine oil temperature not less than 170°F.

The Cirrus SR22 Pilot’s Operating Handbook and FAA Approved Flight Manual list engine and fuel limitations for SR22 airplanes not certified with a turbocharged engine, as shown in figure 2.

Figure 2. Cirrus SR22 engine limitations (top) and fuel limitations (bottom).

The Tornado Alley Flight Manual supplement specified changes to some of these limitations, as shown in figure 3. The oil temperature limitation was unchanged.

Figure 3. Tornado Alley flight manual supplemental limitations.

The Tornado Alley Flight Manual supplement added steps to Cirrus’s SR22 takeoff procedures, stating that engine parameters should read in the green during takeoff and manifold pressure may temporarily increase to 31–32 inches of mercury with an associated increase in fuel flow due to cooler oil temperatures. If the manifold pressure exceeded 32 inches of mercury, then the corrective response was to reduce power, shown in Figure 4.

Figure 4. Tornado Alley flight manual supplemental procedures.

The Tornado Alley Flight Manual supplement did not have a section for turbocharger emergency procedures as specified in the General Aviation Manufacturers Association (GAMA) Specification for Pilot’s Operating Handbook (GAMA Specification No. 1, Revision No. 2, October 18, 1996), which states that Revision No. 2 “incorporates NTSB suggestions for inclusion of emergency procedures for supercharger/turbocharger failure” and that “procedures shall be provided for coping with emergencies involving” turbocharger systems. Manufacturers may use GAMA Specification No. 1 to fulfill the aircraft flight manual requirements in 14 CFR Part 23.

The airplane was destroyed by impact forces and a postcrash fire. The wreckage path preceded the main wreckage on a southerly track and contained two of three propeller blades; the third propeller blade was located about 100 ft west of the initial impact point. The propeller blades were separated near their blade roots, exhibited damage consistent with overload separation and had chordwise scratches consistent with rotation.

A foreign object debris check of runway 4L and its runway edges revealed no parts or pieces associated with the airplane.

Postaccident examination of the flight control system confirmed flight control continuity. The wing flaps were in the retracted position.

Examination of the engine did not reveal any anomalies that would have precluded operation. However, the engine and most of the engine accessories sustained accident-related impact and thermal damage, which precluded functional testing at the system and component level.

The airplane was equipped with a crash-hardened data storage unit installed in the tail of the airplane. The unit recorded flight, engine, and autopilot parameters. Data was logged once per second and stored inside the crash-hardened enclosure.

Recorded data showed 18 engine start attempts, with the last occurring about 1302:00, which was then followed by sustained engine operation at 1,000–1,200 rpm until the beginning of takeoff. About 1313:16, engine oil temperature reached 100°F, and the accident takeoff began about 1315:25. From engine start to takeoff, there was no engine rpm increase to 1,700 rpm, consistent with an engine run-up as prescribed in the Cirrus SR22 Pilot’s Operating Handbook and FAA Approved Flight Manual before takeoff checklist.

About the beginning of takeoff, oil temperature and pressure were 108°F and 47 lbs per square inch (psi), respectively. After takeoff, the following maximum engine parameters were attained: fuel flow of 37.9 gallons per hour, manifold pressure of 32.5 inches of mercury, and oil pressure of 58 psi. The engine oil temperature at this time was 115°F and the GPS altitude was 393 ft. The increases and decreases in engine parameter values were positively correlated. Following these maximum values, there was a general decay in engine parameter values. A stall warning, which began at a GPS altitude of 433 ft, was recorded during the last five seconds of the recording.

The Arkansas State Crime Laboratory performed an autopsy of the pilot. According to the autopsy report, the cause of death was multiple injuries, and the manner of death was accident.

The pilot’s autopsy identified mild coronary artery and aortic plaque. The heart was described as appearing mildly enlarged. Visual examination of the heart did not identify other significant disease.

The pilot’s last aviation medical examination was on April 6, 2023. At that time, he reported a history of high blood pressure, which was noted to be qualified under Conditions Aviation Medical Examiners Can Issue (CACI) criteria. The pilot reported using lisinopril and nebivolol, which are prescription medications that can be used to treat high blood pressure. The choice of nebivolol for treatment of high blood pressure sometimes is prompted by the presence of other cardiovascular conditions, but no such conditions were reported. The pilot was issued a second-class medical certificate limited by a requirement to use corrective lenses to meet vision standards at all required distances.

FAA Forensic Sciences Laboratory postmortem toxicological testing detected diphenhydramine in heart blood at a low level (less than 12.5 ng/mL, according to an FAA forensic toxicologist) and in urine at 207 ng/mL. FAA Forensic Sciences Laboratory postmortem testing measured elevated glucose of 813 mg/dL in urine. (The laboratory considers values above 100 mg/dL to be abnormal.) Vitreous glucose was measured at 58 mg/dL. (The laboratory considers values above 125 mg/dL to be abnormal.) Hemoglobin A1c (HbA1c) was elevated at 9.1% (normal is less than 5.7%) in heart blood.

Diphenhydramine is a sedating antihistamine medication widely available over the counter in multiple sleep aids and cold and allergy products. Diphenhydramine can result in cognitive and psychomotor slowing and drowsiness and often carries a warning about driving and operating machinery. The FAA states that pilots should not fly within 60 hours of using diphenhydramine, to allow time for it to be cleared from circulation. In a typical living person, the elimination half-life of diphenhydramine is about 3–14 hours, and the concentration of the drug in plasma is about 1.3 times that in blood. One small study of healthy adult males estimated that drowsiness may occur at plasma diphenhydramine concentrations above about 30–40 ng/mL, and mental impairment may occur at plasma diphenhydramine concentrations above about 60 ng/mL. Comparing diphenhydramine concentrations in postmortem blood to established ranges in living individuals must be done cautiously, because diphenhydramine has significant potential for postmortem redistribution.

Glucose is the main sugar that provides energy to the body. HbA1c is an indirect measure of a person’s average blood glucose over about the preceding 3 months; HbA1c of less than 5.7% generally is considered normal, while HbA1c of 6.5% or higher diagnoses diabetes. HbA1c of 9.1% corresponds to an estimated average blood glucose over the prior few months of 214 mg/dL. For many adults with diabetes, recommended pre-meal blood sugars are between 80 mg/dL and 130 mg/dL, and recommended peak after-meal blood sugars are less than 180 mg/dL.

The FAA Airplane Flying Handbook (FAA-H-8083-3C), Chapter 18: Emergency Procedures, Engine Failure After Takeoff (Single-Engine), states:

Continuing straight ahead or making a slight turn gives the pilot time to establish a safe landing attitude, and the landing occurs under control and as slowly as possible (assuming a takeoff made into a headwind). This minimizes the risk of injury and usually represents the option with the lowest risk—i.e. the safest option. Turning back requires a more complex analysis and consideration of risk. At some urban airports, there may be numerous hazards in the departure path. In that case, the pilot might turn back, but only if certain the airplane can reach the field from its current position and the pilot has trained and practiced the turn back maneuver.

Turning back to an airport after a low-altitude engine failure, also known as “the impossible turn,” presents many challenges, and a pilot who attempts to turn back without due consideration and training will need considerable luck to prevent disaster. If the airplane strikes the ground during the turn, cartwheeling could occur. If the pilot does not lower the nose sufficiently during the turn, an accelerated stall and fatal crash may occur. Even after executing a successful turn, a return to the airport often results in a downwind approach. The increased ground speed could rush a pilot not properly trained for landing downwind. The increased ground speed and associated increase in kinetic energy also raise the likelihood of serious injury if unable to make the field.

The NTSB conducted a review of available publications, in addition to the Tornado Alley Flight Manual, to determine the available information discussing cold oil temperature effects on turbocharging control systems. Engine oil serves as an information control medium between turbocharging system control components. These publications, as follows, do not discuss resultant excess fuel flow due to excessive boost or the control system’s sensitivity due to cold oil thickening and oil flow reduction.

The FAA Pilot’s Handbook of Aeronautical Knowledge (FAA-H-8083-25C), Chapter 7, Aircraft Systems, only contains a discussion of turbocharged engine overboost and does not address the associated fuel mixture becoming excessively rich due to cold oil temperatures:

Although an automatic waste gate system is less likely to experience an overboost condition, it can still occur. If takeoff power is applied while the engine oil temperature is below its normal operating range, the cold oil may not flow out of the waste gate actuator quickly enough to prevent an overboost. To help prevent overboosting, advance the throttle cautiously to prevent exceeding the maximum manifold pressure limits.

The FAA Aviation Maintenance Technician Handbook – Powerplant (FAA-H-8083-2), discussed turbocharger systems and their component function, but did not discuss the effects of cold oil temperature on overboost and fuel mixture.

Continental Aircraft Engine Service Bulletin M67-12 (May 31, 1967), discusses the overboost of Continental turbocharger systems without reference to the effects of rich mixture. The service bulletin states, in part:

All turbocharged engine installations which are equipped with controller systems automatically control the engine power within prescribed manifold pressure limits. Although these automatic controller systems are very reliable and eliminate the need for manual control through constant throttle manipulation, they are not infallible. For instance, such things as rapid throttle manipulation (especially with cold oil), momentary waste gate sticking, air in the oil system of the controller, etc., can cause over boost.