# Groundspeed/Airspeed of insect

• goldfinger820

#### goldfinger820

Hi all,

I am involved in a project to fly small moths down a wind tunnel to measure their flight patterns.
the moths fly a total of 1.15m into a headwind of 1m/s. i am currently using velocity=distance/time to calculate an average speed but am unsure if this would be a called a groundspeed or airspeed?? most moths take about 6 seconds to fly this distance.
does anyone have any ideas? other thoughts about how to calculate these velocities?

cheers

goldfinger820

That is the ground speed. You are measuring it relative to a fixed ground frame.

Airspeed is the speed relative to the air. Groundspeed is relative to the ground. The 1.15/6 m/s is the ground speed. The airspeed is 1.15+1 m/s.

Airspeed is used for performance calculations like max lift, etc... Groundspeed is used to calculate time of flight.

surely airspeed would be groundspeed-windspeed (which in this case would be negative 1m/s due to it being a headwind)?

It is negative if it is a tailwind, not a headwind.

And any angle between forward and backward results in intermediate values. Despite my total lack of math ability, I could work out wind-vector triangles like a demon. (Gotta love that Cessna flight computer. )
What I really want to know is how you convince a moth to fly upwind rather than down. :uhh:

surely that can't be right - the insects fly into a headwind so the windspeed must be a negative number (see http://www.aerospaceweb.org/question/instruments/q0210.shtml)
using a positive number gives an airspeed of -0.8m/s!

moths and most other animals fly into head winds for tracking purposes

surely airspeed would be groundspeed-windspeed (which in this case would be negative 1m/s due to it being a headwind)?

I suppose it depends on convention--I would thing Sg=Sa+Sw surely if we were talking velocies, this is the case. So the airspeed=2.15m/s as fred suggested. In fact if we were to raise the windspeed to this value, I believe :

Sg=0. Sw=-2.15 and the Sa=2.15