Innovators at NASA's Glenn Research Center have developed an engine control mode that improves an engine's responsiveness to throttle commands during emergency landing conditions. The high speed idle (HSI) control mode increases the speed of the engine's fan and core shafts, allowing faster response and increased maneuverability during landing conditions when engines are in a low-power state. The innovation uses existing engine actuators to change the engine operating point to allow for faster engine response. Use of HSI increases fuel consumption, but it is anticipated to be used only in emergencies where the additional engine performance will help improve aircraft survivability.
Faster engine response has been shown to have the potential to improve the survivability of the aircraft in emergency landings. During approach and landing, the pilot has the throttle at or near flight idle. While at flight idle, the performance of the engine is limited by the control system to prevent a mismatch between the fan and core shaft speeds (and the resulting mismatch in compressor flow rates) to protect against compressor surge. NASA Glenn's HSI control mode would be activated on approach when an aircraft has experienced an emergency. The HSI mode will increase the speed of the engine's fan and core shafts while operating actuators off-nominally to maintain the desired low thrust level.
This is an early-stage technology requiring additional development. Glenn welcomes co-development opportunities. This technology can be used in spacecraft engines, and military and commercial aircraft engines.