Dear Mr. Lamar,


I am impressed with your Web site especially with contribution "MAJOR BREAK THROUGH IN
TAIL SITTER TILT ROTOR VTOL AIRCRAFT" and would like to join the NEWSLETTER.

Wankel engines are of great promise for general aviation, because they fill the gap
between low performance gearless piston engines and excellent performance but expensive
turbines.

As person with a lot experiences with Wankel type engines I would like to ask if Mazda
Wankel engines have problems (oil pump - sump) when they work with full power in vertical
position and how to solve problem if they exist.

In our laboratory we are working on development of a small electrical tail sitter UAV and
find a lot of aerodynamic and dynamic problems in hovering and transition. We had crashes
but mostly because of impropriate adjusted autopilot and unsymmetrical wing separation.

Sincerely yours,

Viktor Sajn
Faculty of Mechanical Engineering
University of Ljubljana
Slovenia

A dry oil sump system must be used. I should add that to the article on the
web site.

Here are some graphics on dry sump systems.

Are you using counter rotating props
on your UAV? I think that would help a lot.

Here are some youtube videos on the subject.
http://www.youtube.com/watch?v=K9ybm05EYWg
http://www.youtube.com/watch?v=Nh9dhBJY010

This airplane is at the Florida Museum at Sun n Fun.

Paul Lamar



Dear Mr. Lamar,

We use 4 electro motors and fixed pitch props. Indeed model is mixed Quad copter and flying wing. For bigger VTOL we think about Mazda Wankel and coaxial rotor (kamov double swash plate type). From aerodynamic point of view proposal is good but is very complicated and expensive.

Tail sitter VTOL is quite sensitive to wind in time of landing (surfaces are vertical) and fast agile controls are must. Look all films about VTOLs - no wind at all! We know why - crashed model. Just changing lift force direction regarding to center of gravity - heavily and slow. Maybe assisting with modified double hydraulic servo system for car steering? Cheap and proven.

What about using single prop and extended ailerons for moment compensation (wingspan at least prop diameter)? 3D models make it without problem?

Suggesting to add radio altimeter which can be made from cheap microwave door sensor. Has 20m/60f range - suit for final touch down.

Pogo was a powerful beast - had no problems to overcome deeply stalled wings in process of transition from hovering to  flight. You will have to go "dynamic" both time.

Viktor Sajn


I think roll control would be marginal with just one prop.
Are you going to Aero in Friedrichshaven in April?

Paul Lamar