DAVID G. ULLMAN
Integrated Distributed Electric-Augmented Lift
Electric airplanes are coming. In the near future they will fill many missions: urban taxi, personal air vehicle, inter-urban commuting, and others still evolving. It is too soon to know what these vehicles will look like and, more importantly, what technologies they will include. Some believe they will take the form of multi-copters or Vertical Take-Off and Landing (VTOL) aircraft, but these need very high power, are inefficient and will most likely be noisy.
While much current effort is going to VTOL development, there are other technologies that may offer better solutions for some missions. One such technology, Propulsion Airframe Interaction (PAI), may result in aircraft that have good handling qualities at very slow speed, reducing or virtually eliminating low-speed Loss Of Control (LOC).
PAI is a recent concept that is made possible providing propulsion with many small electric motors. This allows the propulsion to be distributed affecting the airflow around the airframe in ways not possible in the past, with one or a few large propulsors. PAI is, for the most part, a new concept, but has its root in the 1940s. That said, research on PAI is early and its potential only beginning to be appreciated.
The IDEAL (Integrated Distributed Electric-Augmented Lift) project makes use of multiple Electric Ducted Fans (EDFs) mounted, so they not only propel the aircraft but shape high-velocity air over the top surface of the wing.
IDEALs use of PAI promises to increase aircraft performance and controllability, especially at low airspeed and may have significant impact in reducing Loss Of Control (LOC) incidents through four aerodynamic enhancements: 1) increasing the lift curve slope giving higher lift at lower airspeeds; 2) reducing the potential for separation increasing the maximum lift and delaying stall; 3) increasing flap effectiveness resulting in higher lift at even lower airspeeds; and 4) managing the spanwise lift distribution improving control at low airspeeds. The October 2018 patent, Distributed Electric Ducted Fan Wing (10,099,793) issued to the authors specifically addresses controllability as a feature of the system.
IDEAL has been extensively studied over three years in wind tunnel testing and analytic modeling. Recently, a modified Jabiru, the JabirWatt has been outfitted with the IDEAL technology and flight tests begun. These tests will show the use of IDEAL on existing aircraft and its potential for custom designed craft.
This work on IDEAL was fueled by two articles published in 2009 and 2010 about the potential of electirc propulsion.