Mount Comfort, IN, USA
N15VJ
CIRRUS DESIGN CORP SF50
The pilot reported that he engaged the autopilot (AP) and autothrottle (AT) just after takeoff. Shortly thereafter, he received landing gear up warnings, and the airplane pitched up and engine thrust reduced uncommanded. He stated that he unsuccessfully attempted to disconnect the autopilot and manually override the nose-up pitch and throttle position, but he felt resistance in the control yoke, and the throttle returned to the idle position when he released it. After receiving a stall warning, he chose to activate the airframe parachute system (CAPS). The CAPS deployed and the airplane descended under canopy, coming to rest in a retention pond. Data recovered from the airplane indicated that the CAPS AP mode activated just after takeoff about 226 ft above ground level (agl). CAPS AP mode is designed to slow the airplane by commanding idle thrust with AT, leveling the wings, and increasing the airplane’s pitch attitude in order to bring the airspeed within CAPS deployment parameters. The landing gear warnings the pilot received were due to the airplane’s low altitude and reduced engine power. Although the pilot reported that he pressed the AP disconnect button on the yoke, recorded data showed that the pilot attempted to override the AP and AT servos with manual inputs to the control yoke and throttle lever, and did not press the AP disconnect button until about 27 seconds after CAPS AP mode activated. By this time, the airplane’s pitch trim was in the full nose-up position, and some aileron trim would have been applied in order to level the wings; this is consistent with the pilot’s statement that the airplane pitched up and rolled, which he interpreted as a stall, and resulted in his decision to activate the CAPS at an altitude about 570 ft above ground level. In CAPS AP mode, manual throttle inputs would not decouple AT, and the AP disconnect button was required to disengage AT. Examination and testing of modules from the CAPS activation system showed corrosion on electronic components. Further testing revealed that a momentary interruption of electrical power or ground to the electronic modules in the CAPS would result in the generation of a “CAPS Activated” signal, even if power was restored to the modules. It is likely that the corrosion of electrical components in the CAPS activation system resulted in a transient power or ground interruption, which resulted in generation of the “CAPS Activated” signal and subsequent uncommanded activation of the CAPS AP mode. The pilot likely did not recognize the situation, even though the autopilot status bar indicated the autopilot was in CAPS mode and believed that the airplane was in an unrecoverable flight condition, which resulted in his decision to deploy the CAPS.
On November 25, 2022, about 0800 eastern standard time, a Cirrus SF50 airplane, N15VJ, was substantially damaged following deployment of the airframe parachute system near Mount Comfort, Indiana. The pilot was not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 positioning flight. The pilot reported that the preflight and pre-takeoff checks were normal, and he proceeded to take off from runway 25 at Indianapolis Regional Airport (MQJ), Greenfield, Indiana. After takeoff, he retracted the landing gear and flaps, and around 800 ft above ground level (agl), engaged the autopilot (AP) and autothrottle (AT). A short time later, he received audible and visual gear unsafe warnings; the airplane then pitched up and the engine power reduced uncommanded. The pilot stated that he first attempted to disconnect the AP using a press and release of the yoke-mounted autopilot disconnect button, followed by pressing and holding the button. He also attempted to disconnect the AT system using the button mounted on the center console. Also, during this time, he attempted to manually override the nose-up pitch and throttle position, but he felt resistance in the control yoke that he attributed to the AP pitch servo, and the throttle returned to the idle position when he released it from full forward. He did not believe that the AP or AT had disconnected, and the airplane continued to pitch up and slow down. He said that the airplane was close to an aerodynamic stall and the left wing dropped. At this time, the pilot pulled the handle to deploy the Cirrus Airframe Parachute System (CAPS). The parachute deployed and the airplane drifted down under canopy and landed in an industrial area retention pond (see figure 1). Figure 1: The airplane at the accident site. (NTSB Photo) The airplane came to rest upright with the nose and right wing resting on the bank of the pond. The CAPS parachute had been deployed. The airplane was mostly intact with all flight and control surfaces still attached. The airplane was moved further onto the bank to facilitate examination. The fuselage was intact, but was missing hatch covers on the nose section that housed the CAPS. The landing gear was retracted. The airplane’s top-mounted engine was displaced about 40° to the right. There was a vertical tear in the left side of the engine cowling consistent with one of the CAPS straps pulling the engine to the right during the accident sequence. The wing was intact from tip to tip and remained attached to the fuselage. It had been displaced slightly left during the impact sequence as evidenced by differences in the gaps between the flaps and fuselage on either side of the fuselage. The flaps and ailerons were still attached to the wing. The right aileron had been displaced inboard during the impact sequence. The empennage remained intact. Flight control continuity was established by actuation of the cockpit control and observing movement of the associated flight controls. No anomalies with the primary flight controls were detected. Recoverable Data Module The airplane’s Recoverable Data Module (RDM) recorded the event. The data showed that takeoff was initiated with the flight director (FD) in takeoff (TO) mode. Shortly after takeoff at an altitude about 226 ft agl, the yaw damper (YD) engaged and the flight director FD modes simultaneously changed to CAPS/CAPS, consistent with activation of the CAPS mode. The pitch, roll, and yaw servos all became active as confirmed by torque indications in the RDM data. The AT system retarded the throttle toward idle, and the pitch servo started applying up commands for a target 30° nose-up pitch attitude, also consistent with engagement of the CAPS mode. About 5 seconds later, the Crew Alert System (CAS) generated a “LDG GEAR IS UP” alert. This message could be displayed when the landing gear is retracted and throttle position is below 18.9%. About this time, the throttle was advanced to the takeoff position and remained there for about 2 seconds before the throttle rebounded to the idle position, consistent with the pilot manually advancing the throttle, then letting go. This is also consistent with CAPS mode, which does not disengage AT with manual pilot inputs. About 11 seconds after the initial YD engagement, another “LDG GEAR IS UP” CAS message was generated, because engine N1 speed was below 60% at this time. About 4 seconds later, the throttle advanced, then reduced back to idle, again consistent with the pilot manually advancing the throttle and then releasing it. A few seconds later, the throttle advanced and remained advanced, consistent with the pilot holding the lever in the takeoff position. About 20 seconds after the initial YD engagement, a single stall warning was generated and was active for 1 second as N1 increased past 60% and the landing gear warning extinguished. About 26 seconds after the initial YD engagement all servo torques reduced to zero, the automatic flight control system transitioned to “not engaged,” and the flight director modes were cancelled, consistent with the AP disconnect switch being momentarily pressed. At this time, the airspeed was 116 kts and altitude was about 570 ft agl. Shortly thereafter, the recorded RDM data was consistent with CAPS deployment. The maximum altitude achieved before CAPS deployment was less than 700 ft agl. Once the autopilot entered CAPS mode, the autopilot status indicator at the top of the primary flight display (PFD) would have changed from the selected mode to “CAPS.” The PFD is positioned directly in front of the pilot on the upper portion of the instrument panel. It is unclear if the CAS displayed a “CAPS ACTIVATED” message. CAPS Activation and CAPS Autopilot Mode The pilot activates the CAPS system by pulling the activation handle located in the cabin ceiling above the pilot’s right shoulder. If the airplane is within the CAPS deployment envelope (calibrated airspeed below 135 kts or true airspeed below 145 kts), the CAPS will deploy. If the airspeed is not within deployment parameters, the CAPS Autopilot (AP) mode will engage to decelerate the airplane before CAPS deployment. CAPS AP mode is engaged when the “CAPS system activated” signal is active and the autopilot is engaged or the altitude is greater than 200 ft agl. Upon CAPS activation, the lateral and vertical FD modes will change to CAPS/CAPS, and the AT servos will engage, annunciated by AT in the AP mode annunciation panel (the active AT mode is also annunciated as CAPS). To slow the airplane, the FD will command wings level and a nose-high attitude of 30° and the AT will command idle thrust. The parachute will deploy after the CAPS deployment envelope has been achieved. The CAPS AP Mode will attempt this sequence several times if initially unsuccessful in slowing the airplane. If the system is ultimately unable to bring the speed within the deployment envelope, the CAPS will deploy regardless of speed. The AP will continue commanding the nose-high attitude until the indicated airspeed decreases to below 60 kts indicated airspeed. At this point, the FD will command a 0° pitch angle. The AP servo actuators will remain engaged throughout the descent under canopy, or until the AP is disconnected. If the discrete signal from the CAPS stays active, the AP will automatically try to re-engage CAPS AP mode if the AP is disengaged. The pilot can override this capability by holding the AP DISC button for 5 seconds continuously. The Airplane Flight Manual (AFM), under the Emergency CAS Procedures section with the heading “CAPS Activated,” stated: If message is displayed but CAPS handle is NOT pulled: a. AP DISC Button..............................PRESS AND HOLD 5 SECONDS According to Cirrus, the autopilot disconnect button on the yoke disconnects the AP and AT simultaneously, inhibits the YD while depressed, and inhibits other functions, such as the stick shaker/pusher, while depressed. The RDM data showed that the pilot did not depress the AP DISC button until 26-27 seconds after CAPS mode engaged. CAPS Timer Card The CAPS activation system included the control box assembly (CBA) located in the aft avionics bay. The CAPS primary power holdover timer card (CAPS timer card) provided primary electrical power to the CBA once secondary power was energized and 1 hour thereafter in order to ensure that the CBA retains electrical power in the event of an aircraft electrical failure. Examination of the CAPS timer card from the accident airplane revealed that several areas displayed corrosion or residue. Postaccident testing revealed that the timer card operated nominally, but any moisture that was present on the circuit cards during the accident sequence had since evaporated. Postaccident testing of the CBA revealed that a momentary power interruption or grounding would result in generation of the “CAPS Activated” signal. Once the power or ground interruption returned to a nominal state, the “CAPS Activated” signal persisted in a latched state. As a result of the investigation, Cirrus Aircraft implemented changes to the design circuitry of the CAPS CBA to ensure that neither power nor ground transients will trigger a nuisance “CAPS Activated” signal. Cirrus Aircraft also designed an enclosure and plans for potting the CAPS timer card to protect against corrosion.
The uncommanded activation of the CAPS autopilot mode due to corrosion of the system’s electrical components. Contributing to the accident was the pilot’s failure to identify the CAPS autopilot mode and promptly follow the procedures in the airplane flight manual.
Source: NTSB Aviation Accident Database
Aviation Accidents App
In-Depth Access to Aviation Accident Reports
