NTSB issues safety alert for multi-engine pilots on partial engine failures

The National Transportation Safety Board (NTSB) has issued a new safety alert for multi-engine pilots dealing with partial engine failures. The alert highlights the necessity of promptly feathering the affected engine’s propeller before its rpm drops below the critical threshold where start locks engage.

SA-091 indicates that current pilot training and checklists for multi-engine piston airplanes primarily focus on total engine failures, neglecting partial engine power loss. The NTSB cautions that this gap in training can result in improper management and an increased risk of losing control during single-engine operations.

Although feathering the propeller of an inoperative engine is recommended, once the propeller rpm falls below the speed at which the start lock engages, it becomes impossible to feather it. Agency officials note that the crucial threshold to secure an inoperative motor and feather the affected propeller generally ranges from 1,000 to 800 rpm but varies by make and model. Some manufacturers provide this information in their propeller owner’s manual, while others do not.