Not so dicey

September 2020

Q: A simulation expert known for her wry sense of humor is headed to a famous casino on the French Riviera to celebrate the 100th successful flight of a prototype maneuverable hypersonic aircraft. The sponsor had fretted that the aircraft would fly out of control, but after inputting the results of numerous subscale component trials and conducting rigorous statistical sampling and simulations, she accurately predicted that the odds of that were low. What is the name of her destination, and what is its significance for simulation?

Draft a response of no more than 250 words and email it by noon Eastern Sept. 10 to aeropuzzler@aiaa.org for a chance to have it published in the October issue.

MAGNIFICENT MATCH: We asked how a U-2 pilot flying in the tropics might be able to fly at just a few knots of ground speed, like a magnificent frigatebird.

WINNER: This is possible due to the high winds associated with tropical weather in the magnificent frigatebird’s habitat, the relationship between indicated airspeed, true airspeed and ground speed, and the low stall speed achievable by the U-2. For the U-2 to remain airborne and achieve this feat, the U-2 wing must produce sufficient lift at the low speed. We will assume that the pilot is flying into a severe tropical storm. Tropical storms have winds up to ~63 knots and have lower pressure and higher temperature than normal standard atmospheric conditions. The U-2 has a stall speed of ~65 knots indicated airspeed during tropical storm conditions (higher temperature, lower pressure). Under this condition the U-2’s knots true airspeed is ~68 knots. With a headwind of ~63 knots, the U-2 pilot can achieve a ground speed of just a few knots. The basic lift equation for a wing confirms that even with the lower pressure and higher temperature present during a tropical storm, the knots true airspeed of 68 knots and headwind of 63 knots creates enough lift to maintain flight with a few thousand pounds of fuel and a reasonable angle of attack.

Derek Brookover
AIAA member
Temecula, California; dbrookover@gmail.com; Brookover is an aerospace engineer at General Atomics-ASI in Poway, California.