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Aeronautics - David G. Ullman

Comparing Air Taxi Visions

A simple analytical model is used toestimate range based on type of vehicle, battery characteristics and number of passengers. Accuracy of the model verified by comparing its results to other models and limited real-world data. The model is used to compute sky-taxi potential for VTOLs, rotor-craft ((helicopters and multi-copters) and USTOLs (Ultra Short Take Off and Landing) craft. Results show:

  1. Electric rotor-craft such as the eHang 184 and the VoloCopter 2X have very limited range even with next-gen batteries.
  2. VTOL aircraft need to be very large to be effective (UBER is focused on 5000lb machines). Further, the high power needed, as with the rotor-craft, imply inefficiencies that may not be overcome with any foreseeable batteries and sound levels that may be unacceptable.
  3. USTOL aircraft have high potential. They are perhaps the least developed of the three classes considered but can operate on near future batteries and very small “pocket” airports..
  4. Clearly the use of batteries for air taxis is problematic. Even next-gen batteries are limiting. Other forms of energy storage need to be explored and developed.
  5. It is possible to use a fairly simple model to compare and contrast different classes of air vehicles without getting caught up in the details. 

Click here for a full PDF copy of the paper.

Click here for the equations



 Compare fig


Integrated Distributed Electric-Augmented Lift


The synergy between Distributed Electric Propulsion (DEP)  and aerodynamics offers previously unrealized potential STOL aircraft with efficient cruise.  This concept IDEAL,  Integrated Distributed Electric-Augmented Lift.


To read an introduction to IDEAL click here.


Begining in 2015, Ullman focused on designing methods to use distributed electric ducted fans as a superior approach for electiric airplanes.  This work was fueled by two articles he wrote in 2009 and 2010 about the potential of electirc propulsion.

Hear the Hum? An introduction to Electric Airplanes, KitPlanes, Nov. 2009.

The Electric Powered Aircraft: Technical Challenges, EAA Experimenter, May 2010.




New book!!

"What Will Your Grandchildren See When They Look Up?"

2nd Edition

This book explores the future of aviation. It was developed by students in a class titled “The History of Aviation 1800-2200” offered in 2016 through the Honors College at Oregon State University. The course reviewed the history of atmospheric flight and, in parallel worked with the students to generate a vision of the future, specifically at a time when their grandchildren become aware of objects in the sky - about 2050.

The students make predictions about the future of drones, autonomous flight, supersonic passenger flight, the use of new materials and other topics driving the evolution of aviation in the twenty first century.

For a copy of this 174 page book go to Amazon.  Price $6.05.

Notes for faculty considering having their students write a book can be found here.


Wind Tunnel

To study Ducted WIngs he built a wind tunnel.  Specs:

  • Test section 2' x 2' (600mm x 600mm)
  • Speeds 40 - 80 mph (60-120 ft/sec)
  • Measure Lift, Drag and Pitching Moment
  • Hot Wire anemometer
  • Smoke for visualization
  • Models built by hand or on 3-D printer (in-house)



Vortex Generators for Canard Cooling

In 2012 Ullman finished building a Velocity SEFG.  This effort took him six years and was built in a garage.  It now lives in a hangar behind his house at an airpark in Independence Oregon (at the Independence State Airport, 7S5).  

In 2014 he completed experiments on the Velocity to improve its cooling using vortex generators.  A copy of a paper is available here.  In a reduced form it was published in Kitplanes magazine in December 2015.



EAA Activities

Ullman is past-president of EAA 292 a very active chapter with over 160 members.  His main emphasis has been on youth aviation and airport safety.  In 2016 he piloted one of three Speed Canards from Oregon (7S5) to EAA Airventure in Oshkosh Wisconsin.  On taxing for departure from Oshkosh a friend took a picture of the three about to be eaten by a Sea Fury.  Ullman is in the first Speed Canard.



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