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 Hypothetical Question...
 Jpdflymhtmlb From United States of America, joined Jan 2006, 78 posts, RR: 0Posted Mon Feb 13 2006 23:20:00 UTC (10 years 3 months 2 weeks 4 days 12 hours ago) and read 5219 times:

 Two of them actually. An airplane is getting ready for take-off, and it happens to be full of birds. The pilots, realizing before take-off they are overweight, decide to throw a firecracker in back prior to take off to all the birds start flying. Since they are now flying, would the plane be underweight and be able to make the take-off? Which now leads to this question... Same scenario, except the plane is made of chicken wire... Fly
 Landings are just controlled crashes.
 212 replies: All unread, showing first 25:
 Newark777 From United States of America, joined Dec 2004, 9348 posts, RR: 27 Reply 1, posted Mon Feb 13 2006 23:43:28 UTC (10 years 3 months 2 weeks 4 days 12 hours ago) and read 5202 times:

 Oh boy, I remember this thread.    Harry
 Why grab a Heine when you can grab a Busch?
 DarkBlue From United States of America, joined Sep 2003, 233 posts, RR: 9 Reply 2, posted Tue Feb 14 2006 00:08:13 UTC (10 years 3 months 2 weeks 4 days 12 hours ago) and read 5183 times:

 Newton's 3rd Law: "For every action there is an equal and opposite reaction." For a bird to fly it must create lift equal to its weight. In a closed fuselage the air that supports the birds is supported by the fuselage. All forces must balance within the fuselage.... Since lift = weight, makes no difference if the birds are flying. Now for a chicken wire plane (I assume you mean only the fuselage. A wing made of our chicken wire would have some serious issues   )... With nothing to contain the air that is supporting the birds inside the fuselage, you would simply have a very odd looking helicopter. Yes, the aircraft would be lighter.
 2H4 From United States of America, joined Oct 2004, 8957 posts, RR: 56 Reply 3, posted Tue Feb 14 2006 00:15:52 UTC (10 years 3 months 2 weeks 4 days 11 hours ago) and read 5177 times:

 Prediction: 200+ posts.    2H4
 Intentionally Left Blank
 David L From United Kingdom, joined May 1999, 9646 posts, RR: 42 Reply 4, posted Tue Feb 14 2006 00:48:11 UTC (10 years 3 months 2 weeks 4 days 11 hours ago) and read 5161 times:

 Oh, go on then. I'll agree with DarkBlue. Although there'd be some interaction between the airflow caused by all the flapping and the chicken wire it would be minimal. Of course, I wouldn't fancy the birds' chances at 300 kts IAS.
 Bobster2 From , joined Dec 1969, posts, RR: Reply 5, posted Tue Feb 14 2006 01:51:47 UTC (10 years 3 months 2 weeks 4 days 10 hours ago) and read 5143 times:

 It would be heavier. The firecracker would literally scare the crap out the birds. All the bird droppings would make the plane even more overweight.
 David L From United Kingdom, joined May 1999, 9646 posts, RR: 42 Reply 6, posted Tue Feb 14 2006 02:08:09 UTC (10 years 3 months 2 weeks 4 days 10 hours ago) and read 5133 times:

 Quoting Bobster2 (Reply 5):The firecracker would literally scare the crap out the birds. All the bird droppings would make the plane even more overweight.

In the spirit of such discussions, and given the prediction of 200+ posts, I'm going to go ahead and argue that the aforementioned crap was already in the birds when they boarded. Since a lot of it would fall through the chicken wire, the aircraft would be lighter even if the the birds settled on the "floor" (though they might skid around a bit in the aftermath.

 Aogdesk From United States of America, joined Jun 2004, 936 posts, RR: 3 Reply 7, posted Tue Feb 14 2006 04:42:47 UTC (10 years 3 months 2 weeks 4 days 7 hours ago) and read 5065 times:

 I'm going to hypothesize that upon seeing the rapidly approaching firecracker travelling at approximately ten feet per second, the rate of bird crap production would increase by a factor of .0013. Upon expulsion of said crap, it would create an increased weight on the airframe. Ok...I know I'm full of said crap.
 Bobster2 From , joined Dec 1969, posts, RR: Reply 8, posted Tue Feb 14 2006 04:47:39 UTC (10 years 3 months 2 weeks 4 days 7 hours ago) and read 5064 times:

 Think of a fish tank full of water being weighed on a scale. Everything inside contributes to the total weight. It doesn't matter if an object floats, swims, or sinks to the bottom of the tank; it weighs the same wherever it is. An airplane is like a fish tank, except it has air inside instead of water.
 Vikkyvik From United States of America, joined Jul 2003, 12147 posts, RR: 24 Reply 9, posted Tue Feb 14 2006 05:06:01 UTC (10 years 3 months 2 weeks 4 days 7 hours ago) and read 5059 times:

 Indeed in the spirit of 200+ posts, I'll postulate that said firecracker would perhaps blow out a window, at which point said birds will be sucked out of said airplane, and therefore said airplane will be less the weight of said birds. As a friend of mine said upon seeing a photo of a bird that had gotten stuck in the landing gear door of an airplane (don't feel like searching for the photo), "poor bird, doesn't it know it can fly for free?" ~Vik
 I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 Bobster2 From , joined Dec 1969, posts, RR: Reply 10, posted Tue Feb 14 2006 05:18:31 UTC (10 years 3 months 2 weeks 4 days 6 hours ago) and read 5056 times:

 I think we're all missing the point here. This was clear case of pilot error, plus they broke the law by carrying firecrackers on the airplane. It's true that we don't know all the details until the investigation is completed, but I'm going to immediately blame the pilots, the airline, and airport security. (If you really want 200+ messages, the moderators should move this thread to Civil Aviation.) By the way, it doesn't matter that this thread is hypothetical. The pilots are still guilty until proven innocent. [Edited 2006-02-14 05:21:09]
 Jpdflymhtmlb From United States of America, joined Jan 2006, 78 posts, RR: 0 Reply 11, posted Tue Feb 14 2006 05:30:50 UTC (10 years 3 months 2 weeks 4 days 6 hours ago) and read 5049 times:

 Since I'm looking for a somewhat serious answer, I guess it's safe to say that in the case where the birds are in a closed environment, they do add to the weight of the airplane regardless of whether they are flying or not. In the case of the airplane being made of chicken wire...structural issues aside, they wouldn't add to the weight, therefore the airplane would be able to make it off the runway? Thanks for the humourous comments too, keep em going if you like...
 Landings are just controlled crashes.
 Newark777 From United States of America, joined Dec 2004, 9348 posts, RR: 27 Reply 12, posted Tue Feb 14 2006 06:08:04 UTC (10 years 3 months 2 weeks 4 days 6 hours ago) and read 5029 times:

Harry

 Why grab a Heine when you can grab a Busch?
 Bobster2 From , joined Dec 1969, posts, RR: Reply 13, posted Tue Feb 14 2006 06:16:11 UTC (10 years 3 months 2 weeks 4 days 5 hours ago) and read 5024 times:

 I believe the chicken wire airplane would be like a fish tank in the ocean. Fish could swim in and out of the tank without affecting the weight of the tank, but if you put a rock on the bottom of the fish tank, then the tank would be heavier.
 Bobster2 From , joined Dec 1969, posts, RR: Reply 14, posted Tue Feb 14 2006 06:43:06 UTC (10 years 3 months 2 weeks 4 days 5 hours ago) and read 5019 times:

 People in the old thread were talking about the birds' flapping wings pushing the air down. Actually, I don't believe the flapping has any relevance. Imagine the plane carrying flour as cargo. If you ripped open the bags and used fans to fill the air with flour dust, the dust in the air would still add to the weight of the plane even though the dust doesn't have flapping wings.[Edited 2006-02-14 07:06:11]
 Flyf15 From , joined Dec 1969, posts, RR: Reply 15, posted Tue Feb 14 2006 07:47:33 UTC (10 years 3 months 2 weeks 4 days 4 hours ago) and read 5005 times:

 Technically, after the firecracker goes off and the birds start flying, the aircraft will indeed be lighter. In the explosion of the firecracker energy (heat, sound, light, etc) is released. This energy had to come from somewhere, and it came from the mass of the explosives. The resulting mass of the products is going to be slightly less than the mass of the initial substances. e=mc^2
 David L From United Kingdom, joined May 1999, 9646 posts, RR: 42 Reply 16, posted Tue Feb 14 2006 14:42:22 UTC (10 years 3 months 2 weeks 3 days 21 hours ago) and read 4963 times:

 Quoting Bobster2 (Reply 8):Everything inside contributes to the total weight. It doesn't matter if an object floats, swims, or sinks to the bottom of the tank; it weighs the same wherever it is. An airplane is like a fish tank, except it has air inside instead of water.

 Quoting Bobster2 (Reply 13):I believe the chicken wire airplane would be like a fish tank in the ocean.

That would be true in a closed system, e.g. a proper fuselage, but this is not a closed system. Air being pushed around by the birds wings would be free to leave the aircraft and only a small amount would interact with the chicken wire.

 Bobster2 From , joined Dec 1969, posts, RR: Reply 17, posted Tue Feb 14 2006 19:02:01 UTC (10 years 3 months 2 weeks 3 days 17 hours ago) and read 4901 times:

 I'm trying to refine my analogy to make it more convincing. If you put a fish in a fish tank, the weight of the fish has to be supported by the bottom of the fish tank. If you put a fish in the ocean, the weight of the fish is supported by the entire ocean floor. In both cases, it doesn't matter if the fish is floating on top, flapping its fins, or lying on the bottom. I believe we can say the same about an airplane. A bird in an airplane is supported by the floor of the airplane, floating, flapping, or standing does not matter. If the skin of the airplane is totally porous and offers no air resistance (hard to image, but this is hypothetical), then a flying bird is no longer in the airplane, the bird is in the ocean of air known as the atmosphere. In the first case, the birds' weight has to be supported by the floor of the airplane. In the second case, the weight is distributed over the large atmosphere and the weight is supported by the Earth.
 David L From United Kingdom, joined May 1999, 9646 posts, RR: 42 Reply 18, posted Tue Feb 14 2006 20:06:26 UTC (10 years 3 months 2 weeks 3 days 16 hours ago) and read 4874 times:

 Quoting Bobster2 (Reply 17):A bird in an airplane is supported by the floor of the airplane, floating, flapping, or standing does not matter. If the skin of the airplane is totally porous and offers no air resistance (hard to image, but this is hypothetical), then a flying bird is no longer in the airplane, the bird is in the ocean of air known as the atmosphere. In the first case, the birds' weight has to be supported by the floor of the airplane. In the second case, the weight is distributed over the large atmosphere and the weight is supported by the Earth.

So you're saying that in an aircraft where the skin is "totally porous and offers no air resistance" the weight of the birds is not supported by the floor of the aircraft but by the surface of the earth. I think a chicken wire skin would count as porous!

As I said, there would be a small amount of interaction but the vast majority of the disturbed air would be free to move in and out of the aircraft without interaction. For argument's sake, lets say the surface area of the chicken wire occupies 5% of the area it covers. That means about 5% of the air being pushed down by the birds' wings would collide with the chicken wire in the floor, pushing it down, and about 95% would pass straight through the gap. I'm assuming that boundary layer effects and so on wouldn't affect the result by more than a few percent.

There's a problem with the fish analogy. Whether in a tank or in open water, fish normally have neutral bouyancy - they have the same the same density as the water so don't need to exert a downward force to remain in position.

 David L From United Kingdom, joined May 1999, 9646 posts, RR: 42 Reply 19, posted Tue Feb 14 2006 20:14:12 UTC (10 years 3 months 2 weeks 3 days 15 hours ago) and read 4871 times:

 Quoting Bobster2 (Reply 14):People in the old thread were talking about the birds' flapping wings pushing the air down. Actually, I don't believe the flapping has any relevance.

It does. In order to stay off the floor, the birds have to force air downwards to give them an upwards shove. The air moves downwards with a force equal to the weight of the birds (since that's the force keeping the birds' weight off the floor). Therefore a force equivalent to the weight of the birds acts on the floor. If they didn't flap, they'd fall on to the floor and we'd be back to square one.

 Bobster2 From , joined Dec 1969, posts, RR: Reply 20, posted Tue Feb 14 2006 22:23:31 UTC (10 years 3 months 2 weeks 3 days 13 hours ago) and read 4836 times:

 Quoting David L (Reply 19):In order to stay off the floor, the birds have to force air downwards to give them an upwards shove.

Right now I'm having trouble defending some of the things I said earlier, so maybe you're right.

This is the point where I like switching to the fish tank analogy because it's easy to visualize and it can't be disputed. Adding any object to a fish tank full of water makes the tank heavier regardless of whether the object sinks or floats. Can anybody possibly disagree with this? If you want to lift the fish tank, it takes more energy when the fish are added.

There has to be some mechanism to keep an object floating in the water. As you said, the density of an object might equal the density of water. Or an object with high density could use a propeller to hover. Or an object could be designed with wings and a propeller to move horizontally. But I don't see how the mechanism makes a difference. In all cases it's quite clear that the object adds weight to the tank and the position of the object inside the tank makes no difference. We know this from experiments.

Now change the water to air, keep the fish tank with a cover on top. The differences in density, viscosity, compressibility, etc don't change the fact that water and air are both fluids. Adding an object to the bottom of the fish tank full of air makes it heavier. But suppose we fill the tank with flies. Is it heavier? Definitely yes if they sit on the bottom and I think yes when they're flying, because if you want to lift the tank it takes more energy with flies inside. I don't think that can be disputed. You can't get something for nothing. But is the tank heavier if you put it on a scale? The more I think about this, the more I'm having trouble with the idea that flies add weight to the tank when they're flying. Since air is invisible and hard to feel, it's more difficult to have intuition about what to expect in this situation, even though it's an analogy to fish in water. Flying in air should be like swimming in water. Right?

Regarding the chicken wire issue: Air molecules are always moving. You can't see them or feel them, but they are absolutely all moving all the time. In the absence of gravity, the direction of movement would be totally random. In the presence of Earth's gravity there are slighly more molecules moving down than up. That's why air has weight. That's why the airplane has to lift the weight of air inside.

So when we talk about the chicken wire airplane, the air molecules move through the chicken wire in all directions by themselves. They don't need to be pushed. The air is no longer a part of the airplane because the air molecules have freedom to move. Even if the chicken wire covers 5% of the area, that's really small. I would still say there is no longer an inside or outside of the airplane, the movement of air molecules joins the inside and outside together into one big atmosphere.

[Edited 2006-02-14 22:47:53]

 Sovietjet From Bulgaria, joined Mar 2003, 2734 posts, RR: 15 Reply 21, posted Tue Feb 14 2006 23:04:14 UTC (10 years 3 months 2 weeks 3 days 13 hours ago) and read 4816 times:

 Oh no not this again. If the plane is chicken wire it would weigh less. If it was a real plane then no it wouldn't.
 Silver1SWA From United States of America, joined Mar 2004, 5072 posts, RR: 21 Reply 22, posted Tue Feb 14 2006 23:24:45 UTC (10 years 3 months 2 weeks 3 days 12 hours ago) and read 4809 times: AIRLINERS.NET CREWPHOTO SCREENER

 Quoting Bobster2 (Reply 10):I think we're all missing the point here. This was clear case of pilot error, plus they broke the law by carrying firecrackers on the airplane. It's true that we don't know all the details until the investigation is completed, but I'm going to immediately blame the pilots, the airline, and airport security. (If you really want 200+ messages, the moderators should move this thread to Civil Aviation.) By the way, it doesn't matter that this thread is hypothetical. The pilots are still guilty until proven innocent.

LOL welcome to my RU list my friend. That was classic...

 ALL views, opinions expressed are mine ONLY and are NOT representative of those shared by Southwest Airlines Co.
 David L From United Kingdom, joined May 1999, 9646 posts, RR: 42 Reply 23, posted Tue Feb 14 2006 23:25:06 UTC (10 years 3 months 2 weeks 3 days 12 hours ago) and read 4809 times:

 Quoting Bobster2 (Reply 20):If you want to lift the fish tank, it takes more energy when the fish are added.

In a closed system, yes, i.e. if the displaced water stays in the tank the total weight will equal the original weight of the water plus the weight of the fish. However, if you fill the tank to the top then add the fish, the water displaced by the fish will be spilled over the top of the tank. Since the weight of the water displaced is the same as the weight of the fish the total weight won't change. But here we're talking about something with neutral bouyancy.

 Quoting Bobster2 (Reply 20):There has to be some mechanism to keep an object floating in the water.

The mechanism is that the fish has the same density as the water so there's no net upward or downward force. It's the same mechanism that keeps a litre of water "suspended" in a swimming pool.

 Quoting Bobster2 (Reply 20):Or an object with high density could use a propeller to hover. Or an object could be designed with wings and a propeller to move horizontally. But I don't see how the mechanism makes a difference.

If the object has to apply a downward force to remain "aloft" then it doesn't matter how that force is applied. But it's not the same as the fish scenario.

 Quoting Bobster2 (Reply 20):Now change the water to air, keep the fish tank with a cover on top. The differences in density, viscosity, compressibility, etc don't change the fact that water and air are both fluids. Adding an object to the bottom of the fish tank full of air makes it heavier. But suppose we fill the tank with flies. Is it heavier? I think yes, because if you want to lift the tank it takes more energy with flies inside. I don't think that can be disputed. You can't get something for nothing. But is the tank heavier if you put it on a scale? The more I think about this, the more I'm having trouble.

Agreed so far and I would say categorically that the tank would be heavier than the same closed tank with no flies. However, the flies are forcing air down against the floor when they're flying. Think about blowing on a sheet of paper (the air pushed down by the birds' wings) compared to blowing on a sheet of chicken wire. The paper's going to move quite noticeable while you'd be lucky to move the chicken wire very much at all. The downwards force wouldn't act very much on the chicken wire aircraft but would mostly pass through to the air outside.

 Quoting Bobster2 (Reply 20):Air molecules are always moving. You can't see them or feel them, but they are absolutely all moving all the time. In the absence of gravity, the direction of movement would be totally random. In the presence of Earth's gravity there are slighly more molecules moving down than up. That's why air has weight. That's why the airplane has to lift the weight of air inside.

If there were slightly more molecules moving down than up then the air would eventually spread itself out on the floor! Air has weight because it's trying to move down but can't because something's in the way (more air, the planet's surface, etc.) - the same reason that anything more dense that air has weight.

 David L From United Kingdom, joined May 1999, 9646 posts, RR: 42 Reply 24, posted Tue Feb 14 2006 23:28:55 UTC (10 years 3 months 2 weeks 3 days 12 hours ago) and read 4807 times:

 Quoting Silver1SWA (Reply 22):Quoting Bobster2 (Reply 10): I think we're all missing the point here. This was clear case of pilot error, plus they broke the law by carrying firecrackers on the airplane. It's true that we don't know all the details until the investigation is completed, but I'm going to immediately blame the pilots, the airline, and airport security. (If you really want 200+ messages, the moderators should move this thread to Civil Aviation.) By the way, it doesn't matter that this thread is hypothetical. The pilots are still guilty until proven innocent. LOL welcome to my RU list my friend. That was classic...

I forgot to mention that - agreed!

 25 DC10GUY : Sounds like 2 problems. 1st, bad load plan/ weight & balance not correct, 2nd, Cargo not properly tied down.... Oh yeah one more thing.... Does it rea
 26 Vikkyvik : The flies, whether they're flying or sitting on the bottom of the tank, are adding their combined weight to the tank. However, if the flies were to s
 27 Bobster2 : I'm having a problem with that argument. I thought birds fly by creating a pressure differential above and below their wings, causing an upward press
 28 2H4 : We musn't forget to factor in the loss of feathers resulting from the shock and surprise of the firecracker. In addition, each individual bird's thru
 29 Vikkyvik : Technically speaking, the effect of birds (or airplanes, or whatever) is felt from the wing all the way to the ground. However, it is distributed ove
 30 David L : But there's a downward component. If they propel themselves upwards there must be a force downwards greater than their weight. When they're in "level
 31 Bobster2 : The pressure differential created by a moving wing disipates quickly. The high pressure air mixes with the low pressure air. You guys may be right but
 32 VirginFlyer : Would it make any difference if the birds were all running on treadmills? V/F
 33 Vikkyvik : That's the point - they aren't wasting any energy. They aren't attempting to create a noticeable force on the ground; that's just the result (or caus
 34 David L : But the bulging eyes and stars circling their heads would counteract that. And, as we all know from cartoons, any bird which suddenly loses its feath
 35 Bobster2 : OK. It's easy to see that with the fish tank, but it's harder to comprehend with air. So if we have too many birds, can't we have Dick Cheney shoot t
 36 2H4 : Would there really have to be, though? The relative wind experienced by each bird would be very erratic, and each bird would have to continously adju
 37 Vikkyvik : Now what if the birds were in an A340? It only gets in the air because of the curvature of the earth, right? So if birds are flying in an A340, how do
 38 2H4 : On that note, I predict the birds would prevent an IL-86 from taking off at all. 2H4
 39 David L : In localised patches that's true but overall the forces would balance out. But if the bird is being drawn up by the air pressure then air must be dra
 40 David L : What's the weight of a lawsuit?
 41 Bobster2 : It's easy to accept the explanation that the air supports the birds and the plane supports the air. Or, when the plane is open, the air spills out and
 42 Seanp11 : A firecracker exploding is a chemical reaction, so that ever so famous equation you posted doesn't hold true. The energy released in a firecracker ex
 43 Zeke : Negative, considered a closed volume in the physics sense, the mass of the birds, air in the aircraft, and aircraft remains unchanged. The weight on
 44 David L : I'm not sure I agree it's a closed system if the fuselage is made out of chicken wire - air is free to enter and leave the system. From what I can re
 45 2H4 : Question: How many of the birds are female, and what is the likelihood the firecracker will cause such shock that they instantly lay eggs? This could
 46 David L : Can the eggs fit through the chicken wire (without being pushed)? If they laid the eggs "hard enough" I guess they might scramble their way through a
 47 David L : I meant "with enough force" rather than "hard-boiled", d'oh! My brain hurts.
 48 Jpdflymhtmlb : Ok, good to see so much response on this, thanks for all the replies, but now I have a new question... Lets say the birds are nailed down to their per
 49 David L : In that case they'd be applying an upward force to the aircraft by moving air down through the aircraft so the load would be lighter. This is rather
 50 Zeke : The quote I used was before that bit, for chicken wire it is not a closed system.
 51 Vikkyvik : So after 50 replies, it looks like the consensus is that the next generation of aircraft should be large coconut-shaped chickenwire vessels (obviously
 52 David L : Fair enough - I've been getting the "old" question mixed up with the "new" question, too.
 53 David L : And the Boeing fans would be in uproar.
 54 2H4 : So if when these aircraft are certified, will the swallow thrust be considered when calculating the takeoff performance? Other multiengine aircraft p
 55 David L : Ah, finally, the conditions could officially range from Good to Crap. With the prevalence of FBW, would the wings be mechanically linked to the birds
 56 N600RR : Next generation of aircraft?!? I thought you were describing the future NW DC9 fleet after D checks ...
 57 Flyf15 : Ah, you're right, I guess I didn't think that one through well enough, its been almost a decade since I took a chemistry class.
 58 727EMflyer : This thread reminds me of the plane on a treadmill thread! I'm joining late here, but I have a problem with everyone claiming the air must support the
 59 Zeke : In a closed volume the mass of the aircraft, the cargo, and air (which is a fluid) remains unchanged. Think of the souvenir Christmas settings you ge
 60 David L : With nothing moving inside the fuselage you'll have the weight of the bird pressing down on the floor and the air pressure will be evenly distributed
 61 N600RR : But what about that nano-second when a bird's wing has reached the end of it's flap? Hasn't the maximum amount of upwards force necessary to push the
 62 David L : Absolutely. In practice, there would be an increase in force on the downbeat as the birds accelerate upwards and a reduction in force on the upbeat (
 63 Zeke : Correct, however the mass remains unchanged
 64 Bobster2 : The birds create pressure on the bottom because they are attracted to the bottom by gravity. They also create pressure on the front and back when the
 65 2H4 : But the dust particles are inanimate, don't produce energy, and don't generate their own forces. These self-generated forces...which are above and be
 66 N600RR : No doubt ... unless we are talking about birds approaching the speed of light ... But that's a topic for another thread.
 67 Bobster2 : It took energy in opposition of gravity to get the dust into the air. It took energy in opposition of gravity to get the birds into the air. I still
 68 N600RR : Actually you did in reply 60, which is what made me think of the NASA weightlessness training flights. But I didn't quite grasp your point with the w
 69 2H4 : As I see it...and I'll certainly stand corrected if wrong...the difference is that the dust particles remain suspended for a longer period of time be
 70 David L : First of all, gravity is what's trying to pull everything to the ground. Without it there'd be no weight and the problem wouldn't exist! Flapping mea
 71 Bobster2 : Now we're getting into Brownian motion and the kinetic theory of gasses. The air itself is able to oppose gravity because of thermal energy. (If not
 72 Bobster2 : Sounds like you haven't tried to weigh flour. I have. A lot of the flour particles never make it to the balance. They get blown away by Brownian moti
 73 David L : But when an air molecule and a smoke particle collide you get conservation of momentum. If an upward moving air molecule collides with a smoke partic
 74 David L : Ah, but in a closed environment they would eventually either fall on to the floor, seat tops, etc, or the the energy imparted to the flour by the air
 75 Bobster2 : There has to be a source of heat energy. Nuclear fusion in the Sun, heat rising from the molten core of the Earth, tidal forces from the revolving Mo
 76 2H4 : Bobster, your entire dust analogy is predicated on forces...in this example, solar...that act uniformly upon the birds and dust particles. Again, the
 77 David L : I'll concede that, however, the energy due to Brownian motion is insignificant compared to the energy required to suspend birds in air (unless they v
 78 Sovietjet : If a chicken is on a scale on two legs and weighs two pounds and then raises one leg how much does it weigh?
 79 David L : Is it trying to fly?
 80 2H4 : Are firecrackers involved in any way? 2H4
 81 Bobster2 : I'm still waiting for somebody to challenge me on this. Tell me your car doesn't convert matter into energy because it's just a chemical reaction. Go
 82 David L : Maybe everyone agrees with you.
 83 Vikkyvik : I'd argue with you, but I'm too busy trying to sell the future of aviation to either Boeing or Airbus. They're just not buying the chickenwire-coconu
 84 David L : That's true. Even if the sun blasts heat into the cabin, all that's going to happen is that the collisions, actions and reactions, will be more viole
 85 727EMflyer : David L and Zeke, Sorry for the late reply here, and sorry to all for breaking the very thrilling flour talk One thing I must add. I absolutely agree
 86 2H4 : Exactly! The birds rise on their own accord, while the dust/flour particles simply go wherever outside forces push/pull/suck/blow them. Perhaps the o
 87 Bobster2 : I think it's easier to understand when the airplane is moving. For example, if the birds are flying in the cabin when the plane is moving 500 mph, it
 88 N600RR : ...That's because they have no launch customer lined up yet. I suggest you try pitching the idea to Richard Branson. As soon as he realizes the marke
 89 Vikkyvik : While the birds are accelerating upwards, the scale would register more. When they are in level flight, the scale would register the same (albeit wit
 90 David L : I thought the introduction of the spring balance did that.      Well, after my hissyfit I guess I can't complain about another non_avism.   Edit:
 91 Vikkyvik : That.......was absolutely terrible. I'm not even sorry.
 92 David L : Absolutely. Like a bad song going round in my head. I just didn't see why I should be the only one to suffer it.
 93 LeanOfPeak : Here's something kind of fun. The aircraft COULD have improved takeoff performance. Not because there is less weight for the lift to counteract (Becau
 94 David L : In the chicken wire aircraft, yes. It would be another story for a real aircraft. In order for the birds to propel themselves forwards, they'd have t
 95 Bobster2 : Yes! I believe that works. The birds start in the front of plane before the roll, they hover over a fixed point on the runway until the back of plane
 96 LeanOfPeak : No. I premised the problem that the birds were airborne with forward velocity before the takeoff roll began. Their horizontal reactions with the air i
 97 Bobster2 : Another difference of opinion. This is great because one of our objectives is to reach 200 posts.   If the birds fly with forward velocity, it's like
 98 David L : Yes, that would work... until they slammed into the back of the cabin. It would need to be a very short takeoff. The only way to overcome drag forces
 99 Bobster2 : My hypothetical airplane has a Vr of 3 mph. Is that a problem?
 100 2H4 : Well, if you employ the policy of calling V1 5 kts prior to actual V1 (to compensate for vocalization and reaction times), your V1 speed may be a neg
 101 David L : You might achieve that if the fuselage was made out of chicken wire... oh, wait. But, seriously, don't do that! I nearly started thinking about it.
 102 LeanOfPeak : The birds don't need to be stationary with respect to the runway. If they start at the back of the cabin moving at, say, 30 mph and THEN the airplane
 103 Vikkyvik : However, in this closed system, the velocity of the birds is relative only to the airplane. So if the birds are flying forward at 30 mph (relative to
 104 LeanOfPeak : You make a good point. The birds would have to be willing to lose airspeed as the aircraft accelerated. While unlikely, it is possible. Did I mention
 105 CitationJet : I think you are right. We are already over half way there.
 106 David L : But... but... think about the way the seat back pushes you when an aircraft accelerates down the runway. If the seat back wasn't there you'd drift to
 107 Vikkyvik : D'oh! You're absolutely correct. I realized that awhile after I posted, but alas, twas too late to edit the post. However, I think that whether the b
 108 David L : Don't worry about it - I got into a right pickle with the Brownian Motion!
 109 Zeke : Incorrect. Another simple example, say your in a swimming pool. The total mass of the swimming pool will not change if you stand on the floor, or swi
 110 DEVILFISH : Still a long way to go before 200!
 111 N600RR : Would this be a typical swimming pool or like those being installed in the A380? Never, even in my most disturbing nightmares, could I have imagined
 112 2H4 : Ok, let's try a more extreme example to illustrate the theory. Let's say you load a helicopter into the Good Year blimp and get the blimp airborne. A
 113 N600RR : off-topic alert Thanks! '04 CBR 600 RR You? (BTW, I have a LeMond Tete de Course and an Orbea Kilo too. Riding one of those would be better for my he
 114 Zeke : Dont know if a real helicopter would fit, a model helicopter, or UAV moving inside would not move the blimp. The mass of blimp does not change. The b
 115 Vikkyvik : I wouldn't be too worried about being off-topic in this thread. I doubt anyone other than those posting in it are reading it anyway. Welcome to the f
 116 N600RR : Wasn't worried so much as inadvertently adding another variable to the hypothetical ...before you know it we would be analyzing what would happen if
 117 2H4 : When I was in school, NW donated an old 747 to us which we would play in from time to time. When I took this picture, I was thiiiiiiiiiiis close to g
 118 IFACN : Mind you, I'm not anyone at all! I'm not so good at physics as many of you are, but I want to give my contribute at reaching the 200th post; I was th
 119 David L : Somebody would still want all the window shades down.
 120 2H4 : That chicken wire would ice up in a second. What kind of ice protection would it utilize? Boots would be too big, and there's no room for fluids or b
 121 Vikkyvik : Could you make the chickenwire hollow and have bleed air running through the wires? ~Vik
 122 Bobster2 : I'm not sure about that. What if the fish tank is suspended from ropes and a fish swims horizontally? Wouldn't that make the tank move sideways? When
 123 2H4 : See, I agree with Bobster. That fish tank suspended from ropes, or even better, a single rope, would surely budge. 2H4
 124 Vikkyvik : Yes, I believe then the tank would move. Similar to if I was sitting in a tank suspended by ropes and I kicked off of one of the sides. God I just go
 125 N600RR : Therefore, a pressurized aircraft requires a greater expenditure of energy to maintain flight at altitude than a non-pressurized aircraft of the same
 126 2H4 : I'm not qualified to ref, as my own posts have brought up such topics as chicken-wire anti/de-icing systems, egg-laying ballast-reduction, dead-bird
 127 Vikkyvik : I would think that would make you MORE than qualified to ref. Perhaps we should create another thread to establish the rules and officials of this th
 128 N600RR : Not sure that I agree with this too. With all due respect, I believe you are practically correct, but physically incorrect. An object at rest tends t
 129 2H4 : Yes....I'd like to see a CAD or CATIA draft of the aircraft, with some baseline performance figures. Then we'll begin. That sure seems logical to me.
 130 Vikkyvik : By the way, I don't think we ever established how many birds need to die for the engine-out procedures. I mean, I guess since in other aircraft, engin
 131 2H4 : That will be featured in the supplemental thread. I'm particularly interested in the flight crew regs of such an aircraft. With so many powerplants,
 132 Bobster2 : No. I'm not the referee. We need an impartial screener. But I'm submitting this picture for approval. I just ran across it in another thread. If this
 133 2H4 : That MD-88 was a testbed used for these experiments just last month. The photo shows engine-out ILS trials. 2H4
 134 Vikkyvik : I guess this was one of the less successful powerplant tests (this is an A.net photo, but I couldn't find it): ~Vik
 135 2H4 : No, that was actually a very successful test of an experimental ram-air turbine bird, used to generate backup electrical power. The photo shows it im
 136 Vikkyvik : Ahhh, I stand corrected. (we have wayyyy too much time on our hands)[Edited 2006-02-20 06:44:06]
 137 Zeke : Well its true, let me put in terms of a different fluid which maybe more tangible or you, not air but beer. Which would require greater expenditure o
 138 IFACN : Electric power comes from generators; generators are either linked to the engine or powered by an alternate supply. Let me think... I find impractica
 139 Vikkyvik : See, now someone is actually thinking. It's always a tradeoff. You add more weight, you need more lift, which in turn generally adds more weight. So
 140 IFACN : Well, the hamsters are both the APU and the in-flight generators. This has the great advantage of having full power on the buses even in case of multi
 141 David L : Aaargh! Looking at the last 10 posts or so, it's clear that I'm in way over my head! Fewer if the birds are hawks. I confess I'm struggling with this
 142 Vikkyvik : I'm a little worried now......what if the birds start hunting the hamsters? I hope cockpit/crew regulations would keep this from occurring. ~Vik
 143 IFACN : I think that we're looking at a breakthrough in modern engineering. I never thought of a predator-prey scenario when designing aircraft systems (well
 144 2H4 : Well, it depends on the hamster. Certain models are more efficient than others. Generally, in the interest of weight savings and optimum energy outpu
 145 David L : The APU(s) would need to be mounted above the powerplants, either in a chicken wire pod or one made from perspex. There would need to be a full duple
 146 2H4 : Where are the folks from Modified Airliner Photos? 2H4
 147 David L : Good point but I don't want to do a web search for "hampster" for fear of what I might find.
 148 N600RR : ...hmmm...that makes sense (I think). But not being a physicist, I'm going to have to mullet over a whale before I'll concede your point. This is whe
 149 N600RR : That in addition to all this talk about birds and chicken wire, is really making me feel like an egg that's been in the bird too long...need to get l
 150 Vikkyvik : Haha, I hear ya. So what are we talking for cruise speeds and altitudes? I suppose it depends on the powerplant. We could potentially offer a variety
 151 N600RR : Funny you should mention this, but I was wondering what effect "drafting" by the birds would have on the performance characteristics of our airplane.
 152 Scarebus03 : Before we get completely carried away we have yet to calculate the weight of bird/hamster droppings. For example during a particularly traumatic clear
 153 IFACN : According to direct observation, hamsters stop running only when have to pee or to eat; other body functions can be easily perfomed while running. AP
 154 ATCme : This is one of the funniest threads ever! The combination of the swallow plane, hamsters, and the treadmill make it hilarious. ATCme
 155 Vikkyvik : So are we actually ever gonna reach 200 posts? We kinda stalled out there for awhile. But I think if we really dig down deep, and find that which mean
 156 Bobster2 : I have my copy of "The Feynman Lectures on Physics" standing by in case somebody wants to ask a serious question. Conservation of energy, theory of gr
 157 N600RR : Hey...I wasn't stalled . I've been conducting critically important experiments attempting to answer the following question: Unfortunately, I've been
 158 Vikkyvik : Well, obviously we'll need to subdivide tasks here. Perhaps each person can research a particular beer (or three?) That should make for some interest
 159 David L : Not enough dissenters - wrong forum. Actually, I think I've stalled out because I've been lucky so far. If I carry on I'm going to say something stup
 160 IFEMaster : Well for what it's worth, I read the first 50 or so posts to this thread, and then decided to jump to the bottom, and all of a sudden we're talking ab
 161 Jetflyer : I can't believe there are over 160 responses to this "question". The answer could be given in one sentense. Of course a bunch of birds taking off insi
 162 David L : I think we're assuming it's just the fuselage that's made of chicken wire. I take it you didn't read any of the responses... or even the opening post
 163 2H4 : Navigational issues shouldn't be a problem, but with a bird-powered airplane, measures would have to be taken to avoid damaging controller's equipmen
 164 David L : Let's not start from scratch again! It's only fair that if someone wants to join in they read what's gone before... and the original question. At lea
 165 IFACN : If the passengers jump with a determined force, wouldn't the plane be lighter for enough time to be out of trim, start climbing and then impacting ag
 166 David L : That's a good point. Although the aircraft would briefly be lighter, it would have been shoved downwards as the passengers push off. How quickly does
 167 IFEMaster : LOL! Brilliant response! Thanks, 2H4! Here's a thought though - what if there was no displacement of air? When a bird flies, it displaces air to crea
 168 David L : Correct. Since you're taking care of your weight yourself, the aircraft doesn't have to bother until you turn The Force off - assuming you're not lev
 169 IFEMaster : Good to know. I'll test my Jedi levitation skills this Monday on my LAX - LHR hop.
 170 2H4 : I believe Rutan's designs utilize this technology. 2H4
 171 David L : As long as it's authentic Jedi. Vindaloo after effects count as "jet pack, etc.". Make sure you take the light sabre, not the heavy one.
 172 David L : Wouldn't surprise me. Oops... that might have guaranteed 200+ posts.
 173 Okelleynyc : Forgive me if this has been raised already, but has anyone calculated the additional propulsive force of induced flatulence? Perhaps you could feed th
 174 N600RR : In that scenario, why even bother flying commercial?!? Easier said than done, I suspect. Are you levitating relative to the cabin floor or to the gro
 175 Vikkyvik : ...and the jokes get worse and worse. well, after 161 replies we finally have our answer. oh wait... ~vik
 176 David L : Reminds me of the conveyor belt thread: "An aircraft on a conveyor belt is like a car on a conveyor belt" "No it isn't because..." 10 posts later...
 177 N600RR : ...hmmm ...how much does one's levitating self weigh?
 178 2H4 : Well, that all depends on which planet you're on. 2H4
 179 Francoflier : Ok... Then does the surface of the earth bear the weight of the aircraft when it is airborne? Ah! Not that easy, is it?
 180 Vikkyvik : actually, yes it does. see reply 33. ~vik
 181 2H4 : Well, but couldn't it be said that the air supporting a glider is itself being supported by solar energy (in the case of thermals) and kinetic energy
 182 N600RR : Ok...but then what supports the ground?
 183 2H4 : Not directly related, but I suspect you'd enjoy reading it: Drilling A Hole Through Planet Earth Posted Fri Nov 4 2005 18:01:45 UTC+1 and read 1186 t
 184 Vikkyvik : Moles. Yes, that's correct. Their (and other burrowing creatures') sole function in life is to burrow underground and hold up the ground. However, th
 185 ComairGuyCVG : This sounds like a job for the Myth Busters.
 186 IFACN : Actually, a test protocol about this subject was under design. Alas, while running preliminary investigation about which food optimizes flatulence pe
 187 David L : Phew! I'm glad I didn't see that one at the time. The other side of the planet. Everything above you and everything between you and the centre of the
 188 N600RR : Nope .... It's Atlas! See....
 189 N600RR : Oh sure, give me the easy answer...But what about at the atomic or sub-atomic level?
 190 IFACN : Sorry to disappoint you, the only way would be to reduce mass. May I suggest you a diet? (nothing personal, just silly!) Back on topic: moving from t
 191 David L : By my calculations, quite-a-few point six. The answer at the atomic level is "turtle atoms". The subatomic answer is the easy one. At the subatomic l
 192 SSTsomeday : Getting there.... Yours was the third post, indisputable, and explained so succinctly. Why did there have to be 189 more?? We a-net geeks sure like t
 193 David L : You just need to master the art of not taking 8 hours to make a couple of posts a day.
 194 2H4 : Indeed. It's also a great way to pass the time when you're on hold. 2H4
 195 Vikkyvik : yes indeedy. sadly, my laptop is right next to my tv....i'm screwed.... anticipation grows for the 200th post.... so should we market this idea to bo
 196 2H4 : I know how that goes..... My question hasn't been answered, though: 2H4
 197 Vikkyvik : heh, i avoided answering it, because i believe that the question is insignificant, irrelevant, unfounded, inadequate, and ill-advised. (by that i mea
 198 SSTsomeday : Cool. I would have been in heaven. I would have slept in it.... I would have run up and down the spiral staircase until my legs ached. Why are car en
 199 Vikkyvik : i would think reading this thread would answer that question well, 1 more to go before 200...who'll grab #200? ~vik
 200 SSTsomeday : HA HA THANK you!
 201 PurdueAv2003 : Be careful not to give them to the hamsters, though. I've heard that they can't fart or belch and would just explode, disabling the APU's!
 202 David L : Good question but I just get even more funny looks when I ask. Then they'd need pressure suits designed to give way underneath first, giving a shaped
 203 Vikkyvik : So we're talking one-time use hamsters? We'll need a reliable supplier then. I think PETA might be interested in our activities.... ~Vik
 204 SSTsomeday : Pop quiz: If an airplane full of flying birds and made of chicken wire travels from LAX to JFK at 500 miles per hour, how many farting hamsters wearin
 205 2H4 : No problem. APUs can be deferred, hamster-powered or otherwise. 2H4
 206 Vikkyvik : let's see.... ZFW = 110,000 lbs. (i figure chickenwire can't be that heavy) Fuel (Bird/Hamster food) = 30,000 lbs. including reserves Passenger weigh
 207 SSTsomeday :
 208 Vikkyvik : funny thing is, out of all the numbers i posted, the one i got wrong was the number of posts including mine. i said 205....it was actually 206. i post
 209 Meister808 : And at that, I came quite close to peeing myself. Nice work on the rest of it, guys. Next time I go outside and get hit with a carpet of s*it falling
 210 2H4 : Well, either that, or there's a Kalitta 747 in the vicinity.... 2H4
 211 Jetflyer : Yes it does, I knew that anyway because it goes by the same principle as what I said in the first place. Here's one for you, does the earth bear the
 212 David L : No, that's a job for the US Treasury.
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