This is an old question to which there have been some answers and a lot of head-scratching. In the 1930s, aircraft had been flying for around 30 years and our understanding of the principles of flight was growing. However, when these principles were applied to the bumblebee, the result claimed that it was impossible for them to be able to fly. Unfortunately, they could state this whilst watching bumblebees happily flying about.
What they did was calculate the wing area and the rate of flapping against the weight of the bee and came back that it should not be able to get off the ground. It was in 1996 that the University of Cambridge thought they had arrived at a solution. They analysed the air vortices around a bee’s wings and said this gave them the extra lift in order to fly.
However, in 2001, the University of California shed doubt on these findings. They built a very sophisticated robot bumblebee and then analysed all of the forces acting on the bee whilst in flight. Their results said that taking the bumblebee’s large body shape and weight, the vortices were not sufficient to allow flight. So, back to square one.
To make matters even more complicated, further research showed that bumblebees could not only carry their own weight into the air, they could carry a further 50% of their weight with them. The problem would have to be approached from a new angle. Luckily, that has happened. New research has come from the direction of not comparing a bee’s flight to the principles of flight for an aircraft.
An aircraft flies due to a difference in air pressure flowing above and below the wing; higher pressure below the wing and lower pressure above the wing. The lift increases with the speed of the aircraft until it is able to take off. On the other hand, a bumblebee moves its wings at an acute angle which creates those additional “lift” vortices. However, it was then discovered that a bee’s wings, which can flap at up to 200 per second, do not flap up and down, but back and forth.
The mechanics of this are similar to a human sweeping their arm forward with the palm of the hand facing down and then flipping their arm over and sweeping backwards with the palm of the hand now facing upwards. This action creates air vortices which further creates a difference in pressure with the surrounding air. By keeping these vortices going, the bee creates the lift to fly and remain in the air.
John Pullen 