View Full Version : Anhedral and ducks
rotorfossil
10th May 2006, 18:39
OK guys, here is an odd one to exercise the aerodynamic brains. My wife breeds ducks and wildfowl (as well as driving helicopters). She asked me: "Why do ducks when they are making a glide approach to their water ski landings, and before they lower the undercarriage, sweep their wings forward and carry considerable anhedral. Surely anhedral is laterally destabilising and unlikely to increase lift". Er.....right.
fantom
10th May 2006, 19:04
bending the wings to use as airbrakes.
gaxan
10th May 2006, 21:08
Its a well known fact that Ducks ar not stressed for inverted flight--
Otherwise they would quack up !!!! boom boom!
DX Wombat
11th May 2006, 12:19
Surely anhedral is .......unlikely to increase lift". Er.....right. Isn't the clue in the fact that they are landing not trying to get airborne? :confused:
AngloPepper
11th May 2006, 20:10
Total guess work, but I'll have a stab at this. I suspect they are using their tip feathers to detect the change in local airflow as the ground effect kicks in. This allows them to judge the flare which could be a challenge otherwise given the difficulty judging height over water.
fantom
11th May 2006, 21:00
well, where do we start?
gaxan should be banned for a start. failing to mention that one should be 'feathered'. also failed to mention Vmc beak.
DX W knows better, I am certain. even a duck needs lift at rotation as well as the flare.
AP is clearly mad; who would use feathers rather than eyeballs to judge the flare?
I am the only sane one here. not for the first time...
To maximise lift and drag close to the stall making best use of ground/over water effect contribution. Flicking the odd feather would probably be enough to control the roll instability from the anhedral.
Similar to the technique used by paragliders and to a lesser extent by hang gliders on landing.
Do the ducks always touch down directly into wind?
Wouldn't it be great to be able to do that!
Does anyone know the rest of the words to that old WW2 aviators song -
"Be kind to your web footed friends
Because a duck may be somebody's mother
Well you may think that this is the end
Well it is."