CEN16LA223 · Cirrus Design Corp SR22

The commercial pilot was conducting a local flight when he noted a lower-than-normal oil pressure indication and engine roughness. The engine subsequently experienced a partial loss of power and the airplane could not maintain altitude. The pilot deployed the Cirrus Airframe Parachute System (CAPS) at an estimated 472 ft above ground level, and the airplane impacted rough terrain under canopy in a nose-low, upright attitude. A test run of the engine and review of recorded data did not reveal the reason for the partial loss of engine power.

Examination of the airframe parachute system revealed that, during deployment of the CAPS, the rocket separated from its lanyard in overstress. Fracture testing of the lanyard revealed that it did not exceed the minimum value in several tests, and the examined lanyard sections did not fully conform to specification; however, it is unlikely that these anomalies resulted in the overstress fracture.

Features observed on the CAPS retaining harness suggested that some resistance was encountered when pulling the incremental bridle from the sleeve during the deployment. The cover flap from the retaining harness had discoloration and heat damage consistent with abnormal exposure to the rocket exhaust, and pulled stitches were noted in the vicinity of the sleeve where the incremental bridle was stowed. It is likely that the incremental bridle was not released immediately from the sleeve, which kept the rocket closer to the retaining harness and placed abnormal loads on the lanyards. At some point, the incremental bridle was released from the sleeve and loaded to separate the stitches in the incremental bridle as designed.

During a nominal CAPS deployment, the airplane enters a nose-low attitude before leveling off, a stage of deployment referred to as "tail drop." For tail drop to occur, the deployment must be initiated to allow adequate time and/or altitude. During the accident, the parachute inflated fully; however, the abnormal CAPS deployment, as well as low deployment altitude resulted in the airplane touching down in a nose-low attitude before tail drop occurred.

Based on static pull tests in the lab, the orientation of the incremental bridle within the sleeve can significantly affect the force required to release the incremental bridle from its stowed position. A review of parachute packing procedures revealed that the orientation of the incremental bridle as it was inserted in its sleeve was not specified. In the absence of any specific procedure for orienting the incremental bridle in the sleeve, it would be possible for the incremental bridle to be inserted in either orientation. The investigation could not determine whether the incremental bridle had been inserted in an unfavorable orientation or if such an orientation would have resulted in the lanyard fracture. Based on review of the parachute deployment and subsequent testing, an exact cause for the abnormal CAPS deployment could not be determined.

Verbatim NTSB analysis and probable cause from the NTSB dataset