Prandtl-D Aircraft

The Prandtl-D No. 3 research aircraft had its first flight on Oct. 28, 2015. (NASA / Lauren Hughes)

NASA's Armstrong Flight Research Center 

engineers in Edwards, California, are working 

on an increasingly complex aircraft called the 

Preliminary Research Aerodynamic Design to 

Lower Drag, or Prandtl-D.

The aircraft features a new method for 

determining the shape of the wing with 

a twist that could lead to an 11-percent 

reduction in drag. The concept may also lead 

to significantly enhanced controllability that 

could eliminate the need for a vertical tail and 

potentially to new aircraft designs.

Flight data from the first two Prandtl-D 

vehicles validated the use of twist to tailor 

the lift distribution across the aircraft’s 

wing – bell shaped rather than the traditional 

elliptical shape – leads to more efficient flight. 

In fact, engineers estimate future aircraft 

could see more than a 30 percent increase in 

fuel economy by using the new methods of 

wing design and eliminating the weight of 

the modern aircraft tail and its flight control 

surfaces. In that regard, Prandtl-D research 

also borrows from how birds fly. Birds 

turn and bank without vertical tails that are 

required for such maneuvers on traditional 

aircraft, but not on the Prandtl aircraft.

The first two subscale Prandtl-D aircraft had 

a 12.5-foot wingspan and were constructed 

of a machined foam core wrapped in a skin 

of carbon fiber. Initially, each aircraft was 

radio operated with a hobby-grade controller 

and launched with a bungee cord system. The 

second aircraft also featured an Arduino flight 

data system.

The Prandtl-D No. 3 first flew Oct. 28, 2015, 

with double the wingspan of the earlier 

versions. The third aircraft also has the same 

Arduino flight control system as the second 

Prandtl-D subscale model and is constructed 

of carbon fiber, fiberglass and foam. Follow 

on flight tests will switch from a bungee 

launch method to a towed launch like a glider. 

Another key difference in the third Prandtl-D 

is an addition of a University of Minnesotadeveloped off-the-shelf data collection system.

Flight data also reinforces a number of wing 

design solutions used on the Prandtl-D aircraft 
FS-2016-03-106 AFRC

National Aeronautics and Space Administration

Armstrong Flight Research Center

P.O. Box 273

Edwards, California 93523

NASA Facts

This illustration shows what a Prandtl-M might look like flying 

above the surface of Mars. (NASA / Dennis Calaba) 

that were an outgrowth of ideas by aeronautical engineer 

Ludwig Prandtl in the early 20th century. Prandtl was a 

German whose research is considered a foundation of 

modern aerodynamics. The Prandtl-D's designs are also 

based on glider concepts of German brothers Reimar 

and Walter Horten and incorporate the conclusions of 

NASA aerodynamics pioneers R.T. Jones and Richard T. 

Whitcomb.

Albion Bowers, NASA Armstrong chief scientist and 

Prandtl-D project manager, put all the pieces together 

from the classic aeronautical theorists and has led the 

NASA effort with help from student interns. 

In March 2016, Bowers published a technical paper 

entitled, “On Wings of the Minimum Induced Drag: 

Spanload Implications for Aircraft and Birds,” NASA/

TP – 2016-219072. Detailing the aerodynamic properties 

and mathematics associated with the project, Bowers 

discusses in depth the science behind altering the spanload 

distribution on aircraft wings and the data gathered from 

experiments that demonstrated validation of its critical 

principles. Bowers’ publication can be requested either 

electronically or in paper form, via NASA’s Scientific 

and Technical Information Office, at 717-864-9658, or by 

email at help@sti.nasa.gov. 

Prandtl-D No.3 Specifications

• Wingspan: 25 feet

• Weight: 28 pounds

• Airspeed: 18 knots (approximately 21 mph)

• Testing Altitude (maximum): 220 feet

• Primary Materials: Carbon fiber for structure, with 

 fiberglass for the skin

Prandtl-M

Work on the Prandtl-D led to a concept for a Mars 

airplane. If the Preliminary Research Aerodynamic Design 

to Land on Mars, or Prandtl-M aircraft, is successful, it 

could collect and transmit valuable information back to 

Earth.

Envisioned with a wingspan of two feet and weighing less 

than three pounds, the aircraft would be able to deploy, 

fly in the Martian atmosphere, glide down and land. The 

Prandtl-M during its flight over Mars could collect very 

detailed high-resolution topographic images that could tell 

scientists about the suitability of potential landing sites.

Prandtl-M would have a flight time of about 10 minutes 

and would glide for the last 2,000 feet to the Mars surface. 

Its range would be about 20 miles.

Student Involvement

If a NASA Armstrong concept for a Mars airplane takes 

flight, it will be in part thanks to support from college and 

university student interns.

The students started with a boomerang-shaped aircraft 

constructed of carbon fiber and conducted research by 

flying it down Armstrong hallways, in a conference room 

and then in an aircraft hangar. Those flights allowed a 

peek at the aircraft’s aerodynamics before moving on to 

more complex tests and higher altitudes, resulting in a 

more delta-shaped aircraft.

Students in NASA education programs have had 

opportunities to perform hands-on job experiences across 

disciplines to learn what it takes to pave the way for the 

technologies of tomorrow such as the Prandtl-D and 

Prandtl-M.