# Energy efficiency of MacCready Gossamer Albatross

Updated Nov 9, 2020

• covered around 2.0—4.6 m/kJ
• and moved mass at around 0.1882 —0.4577 kg⋅m/J

Contents

## Details

The MacCready Gossamer Albatross was a human-powered flying machine that crossed the English Channel in 1979.1 The pilot pedaled the craft, seemingly as if on a bicycle. It had a gross mass of 100kg, flying across the channel,2 and flew 35.7 km in 2 hours and 49 minutes.3 The crossing was difficult however, so it seems plausible that the Gossamer Albatross could fly more efficiently in better conditions.

We do not know the pilot’s average power output, however:

• Wikipedia claims at least 300W was required to fly the craft4
• Chung 2006, an engineering textbook, claims that the driver, a cyclist, could produce around 200W of power.5
• Our impression is that 200W is a common power output over houres for amateur cycling. For instance, one of our researchers is able to achieve this for three hours.6

The best documented human cycling wattage that we could easily find is from professional rider Giulio Ciccone who won a stage of the Tour de France, then uploaded power data to the fitness tracking site Strava.7 His performance suggests around 318W is a reasonable upper bound, supposing that the pilot of the Gossamer Albatross would have had lower performance.8

To find the energy used by the cyclist, we divided power output by typical efficiency for a human on a bicycle, which according to Wikipedia ranges from .18 to .26.9

### Distance per Joule

For distance per energy this gives us a highest measure of:

35.7 km / ((200W * (2 hours + 49 minutes))/0.26) = 4,577 m/MJ

And a lowest measure of:

35.7 km / ((318W * (2 hours + 49 minutes))/0.18) = 1,993 m/MJ

### Mass per Joule

For weight times distance per energy this gives us a highest measure of:

(100kg * 35.7 km) / ((200W * (2 hours + 49 minutes))/0.26) = 0.4577 kg⋅m/j

And a lowest measure of:

(100kg * 35.7 km) / ((318W * (2 hours + 49 minutes))/0.17) =  0.1882 kg⋅m/j

Primary author: Ronny Fernandez

## Notes

1. “The Gossamer Albatross is a human-powered aircraft built by American aeronautical engineer Dr. Paul B. MacCready‘s company AeroVironment. On June 12, 1979, it completed a successful crossing of the English Channel to win the second £100,000 (£509644 today) Kremer prize.[1]

2. “The empty mass of the structure was only 71 lb (32 kg), although the gross mass for the Channel flight was almost 220 lb (100 kg). “

3. “Allen completed the 22.2 mi (35.7 km) crossing in 2 hours and 49 minutes, achieving a top speed of 18 mph (29 km/h) and an average altitude of 5 ft (1.5 m).”

4. “To maintain the craft in the air, it was designed with very long, tapering wings (high aspect ratio), like those of a glider, allowing the flight to be undertaken with a minimum of power. In still air, the required power was on the order of 300 W (0.40 hp), though even mild turbulence made this figure rise rapidly.[2]