Highly technical aerodynamic question

[compressor stall]

Most of you would have observed that when taxying the cockpit is often buzzing with those pesky little bush flies. When the aircraft's cabin altitude climbs to around 5000 feet the flies seem to "go off to sleep" and disappear.

On descent as the cabin heads through the same approximate altitude, they wake up again to bother you.

Now my question is "Why?"I have 2 thoughts:

First, the flies become mildly hypoxic in the rarified air of about 5000 foot and above, and too lethargic to fly. This could be explained by the drop in partial pressure which is not enough to force the oxygen though their exoskeletons (they have no lungs). Less oxygen, less activity.

Secondly, the aerodynamics of a fly is so optimised that the increase in altitude no longer allows it to fly - the wings no longer
produce sufficient lift.

Any suggestions as to which one would be correct, or any other ideas? I have ruled out temperature as pressurised a/c can hold the same or warmer temps as ground level.

If there are no answers here, I might test out the theory in the back shed with a a glass jar, suction pump, altimeter, oxy level meeter, oxygen and nitrogen bottles.

And flies.

CS

[Ash767]

That's a good question:confused:

I know from being in the Australian alps in summer there are flies about, Thredbo would be about 5000ft elevation I would say.

Maybe it has something to do with our rate of ascent, just a thought.

Ash767:ok:

[Aerodynamisist]

I have found by experiment that temperature affects flies, if you reduce the temp the flies appear to sleep, as a kid we used to put flies in the fridge and when they had cooled down they stopped moving, we would then glue the flies legs to a small model of an aeroplane made out of match sticks (two or three on each wing, shave the matches back to reduce weight) put the model in he sun and the flies came back to life and the model would fly. Not sure about the further affects of altitude on flies, would make an interesting question for doctor Karl.

[Jet_A_Knight]

No matter how 'sleepy' those little b@stards get, they still seem to avoid getting squashed and buzz around the windscreen with impunity.

If you leave them alone for a while and have another go, you can squash them a bit easier. I always thought that was due to their getting çomplacent'. :confused:

Compy, you might just have something.

Ahh, summertime in Australia! Nothing like taking off overweight for all those damn flies stuck to the back of your shirt!

Add one more item to TOPD checks: Kill the flies before they wake:8 :

[The Strez]

Hey there Stallie. Hmm dont know about the flies down your way but I've had a cabin alt of around 8000' and the little ******s are still full of beans! Maybe they breed em tougher up here in the Kimberely!!:ok: But the good thing is the locals smell that bad they hang off them most the time when in the plane!!:} :yuk:

[compressor stall]

Good point Strez, but also consider where those flies have been. A friend in a remote NT community contracted what is normally a venereal disease in his eye - 99% chance transmitted by flies.

[swh]

Hey CS,

This sounds like a question for Dr. Karl (http://www.abc.net.au/science/k2/homework/default.htm)

BTW have you noticed that when you turn your engine/s off, it also seems to have an effect ?

SWH

[Travelair]

but I do know that a good negative "G" will make the dead ones creep out of everywhere...then you need the vacuum!

[Tinstaafl]

I've always thought it was their reduced O2 uptake efficiency. Never considered the power required aspect although that would go hand in hand with the O2 part.

[Thump & Go]

For what it's worth flies enter a coma at temps below 4 degrees C - hence them being "sleepy" in the fridge. That aside, the oxygen theory sounds feasible to me.
Anyone with a BSc in flyology got the real gen?;)

[Woomera]

Comfortably relaxing whilst they enjoy a pleasant flight? :p

W

[Sheep Guts]

There are alot of factors here.

1. Age of the insect. Screworm Flies and most Blow Flies in Oz will live two weeks. Life cycle aswell (basically flies eat then f $%^&).
2. Altitude of operation. Some flies are ok at high altitudes, where they normally prevail.
3. Temperature. Effects flies activity and energy burn.
4. Sunlight or darkness. Direct warmth.
5. Species of Fly. Relates to the robustness of the species

I have dropped Sterile flies on different occasions for around 4 years on an off. Screworm flies over the Jungles of Central , South America and the Carribean, and Mediterrainian Fruit Flies over Southern Mexico. Altidues varying from 1000 ft agl to 14,000ft.

But I will ask the a Doctor Entamologist, colleague of mine tommorrow to give you a definitive answer.


Regards
Sheep

[QSK?]

The answer fellas is to avoid cruising at Blowflies by the Thousand (the old B050 for those who remember it).

[Jamair]

:8 Judging by some of these replies, it might be time for some of you folk to visit your local headshrinker and discuss the sociopathic / psychopathic tendencies indicated by your treatment of insects. Whats next, crackers up the bvms of canetoads, then torturing kittens......?..:uhoh:

(Before anyone gets all hot & bothered, YES I am being humourous!)

[OzExpat]

If there are no answers here, I might test out the theory in the back shed with a a glass jar, suction pump, altimeter, oxy level meeter, oxygen and nitrogen bottles.

And flies.
That sounds like a plan, Professor Stallie! Also sounds like good fun and I'm sure you'll have no trouble locating a suitable quantity of flies that are willing to participate in the experiment. :p

However, I thought you'd have at least one other way to utilise yer off-duty time... :E

I believe that I speak for everyone when I say that we look forward to the publication of yer results... in each activity! :D

[compressor stall]

Jamair as for torturing animals....you should visit Karumba during prawn camp. Evening acitivty when the cane toads swarm around the sodium lights eating the insects out comes the five iron for some chipping practice into the river.... :p

[Spotlight]

Stall, If chipping cane toads is a novelty to you I'm guessing you didn't grow up in Queensland. (Formative years being incidental).

[olderbutyzer]

Q. What do you get if you pull the wings off a fly?

A. A walk. Well, it can no longer fly, so it's not a fly, is it?

[Towering Q]

CS...I always thought it was the drop in temp but the oxygen/exoskeleton idea has merit.

On the subject of flies, I notice plenty of sleeping/dead ones in the small space between the window layers and can't see where they get in. Very annoying after cleaning windows inside and out to impress pax.

[Blue Sky Baron]

Found these links a while ago while looking for info on Bumble Bees!

http://www.cs.washington.edu/homes/diorio/MURI2003/Publications/sane_review.pdf

http://www.news.cornell.edu/releases/March00/APS_Wang.hrs.html

http://faculty.washington.edu/callis/Flight/Insect_Flight_A-99.htm

http://www.irreversiblesystems.com/pdf/bumblebee.pdf


Whilst not specifically about flies, interesting all the same.


BSB

[The Voice]

Crikey Stally ... you DO have too much spare time on your hands!!