People Archive

Pedal power

Tuesday, March 24th, 2009

The idea of a human-powered helicopter has intrigued many engineers and pilots. Although a practical application really does not exist, it is a good exercise in the development of highly efficient airfoils and light weight structures. As such, many colleges and universities have put together teams of engineering students to develop and build a human-powered helicopter.

A human-powered aircraft is defined as a vehicle that can carry at least one person using only what power is provided by the person(s) on board, usually by pedaling. Early attempts mainly involved airplanes. For example, the best known human-powered airplane is the Gossamer Albatross, which flew across the English Channel in 1979. Helicopters which require much more power to hover present a much bigger challenge. The two biggest problems are weight reduction and designing a highly efficient rotor system. Efficiency means that the rotors must generate a lot of lift with very little drag.

In 1980, to help further and support the idea of a human powered helicopter, the American Helicopter Society established the Igor I. Sikorsky human-powered helicopter competition. A prize of $20,000 was offered for a successful controlled flight lasting for 60 seconds and reaching an altitude of 3 meters while remaining in an area 10 meters square.

The first vehicle that actually got airborne was the Da Vinci III in 1989, designed and built by students at Cal Poly San Luis Obispo in California. For high rotor efficiency, the students knew that it would be important for the blades to work with as much air as possible. A big rotor handles a large amount of air and thus requires less energy to produce lift. The Da Vinci III had a 100-foot rotor diameter and a tip speed of 50 feet per second. In order to reduce weight, rotor tip propellers provided thrust. This eliminated the need for a transmission and anti torque system. The approximate weight of the aircraft with pilot was 230 lbs. It flew for 7.1 seconds and reached a height of 8 inches. However, the helicopter was unstable and required students on the ground to assist with control. No attempt was ever made to correct the instability.

The current world record for human-powered helicopters is held by an aircraft named Yuri I, built by a team from the Nihon Aero Student Group (NASG). It used four two-blade rotor systems (10 meter diameter each) operating at 20 rpm. In 1994, it achieved a height of 20 cm for 19.46 seconds unassisted and unofficially reached 70 cm during a flight lasting 24 seconds.

As far as I can tell, the most recent attempt, although unsuccessful, at a human-powered helicopter was on August 10, 2004, by a group of engineering students at the University of British Columbia. Although their project seems to be on hold, their Web site is still up.

Many have attempted to fly human-powered helicopters both before and after the creation of the Sikorsky Prize. So far no one has met all of the Sikorsky prize’s requirements.

Lexy’s adventure

Monday, March 9th, 2009

As a parent, I often wonder if my children will develop a passion for flying. I have two daughters, Madi who is 8 years old and Lexy who is 13. Both of them have been around airplanes and helicopters from the time they were babies. In fact, Madi got a helicopter ride before she was born. My wife was four months pregnant, when we flew an R44 from California to Pennsylvania (see AOPA PILOT, September 2000).

Sometimes I think spending so much time around aircraft has given them a different perspective than their friends. Like the time my wife and I decided to rent a C172 and take them around the area to look at the fall colors. They were excited, however, after takeoff we looked in the back and they were both sleeping. My wife commented, “I am not sure they understand the difference between this and the car.”

Last year I had an opportunity to take Lexy with me on a ferry flight from Dallas, TX to Long Beach, CA in an AS350 Astar helicopter. This time she wasn’t content just being a passenger, she wanted to try flying. The first day was a short flight to El Paso, TX. So once clear of DFW’s class B airspace, I gave her the controls. She could hold it steady for a short time before I would take over, straighten it out, and give it back to her. She was determined to make the helicopter do what she wanted and after about 20 minutes she could basically hold it straight and level. After an hour or so she was bored and started asking a lot of questions. I showed her how to read the Garmin GPS, hold heading and altitude and after practicing the rest of the day she got pretty good.

The next day she started out flying right away and flew almost the entire day. I watched, somewhat amazed, as she held a steady course and would tell me how she was using the information she was reading off the GPS. After a while she was eager to learn more and I showed her the sectional map. She would take a break from flying for 5 or 10 minutes and study it. Along our course about 20 nm south of Deming, NM was a tethered balloon to 15,000 feet msl. It was marked on the sectional as a restricted area and she noticed we were heading right for it. When we got closer, she spotted the balloon glimmering in the sun and turned north to avoid the area.

By the time we arrived in the Los Angeles area, she was really comfortable flying and a big help with threading our way through the crowded airspace. We parked the helicopter at Long Beach airport and flew home on the airlines. The next day she came home from school looking very sad. I asked her what was wrong and she said that none of her friends believed that she flew a helicopter. Luckily, we took lots of pictures for her to show them.