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So do you know the answer - 50 tons of Canaries


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Any commercial pilot please do not answer this if you know the answer and give it away this is for the guys to exercise their brains in RAA or PPL pilots.

 

This question we got thrown as a hypothetical in one of senior commercial theory licence questions in class it was not in an actual exam – but a bit of fun by the instructor.

 

Accept the premise AND all assumptions.

 

So we have 50 tons of Canaries (yes little yellow birds) sitting in all the seats of a 747. No seats belts.

 

The 747 is flying at 35,000 feet straight and level.

 

Then all 50 tons of Canaries become airborne inside the 747 flying around.

 

The Question

 

  • What happens to the 747 In other words is it 50 tons lighter Or is it the same weight at that point in time.
  • If it is 50 tons lighter does THE 747 climb
  • If the 747 maintains it's flight level without climbing WHY?

 

 

Please explain your logic and process of YOUR answer.

 

No droll smart arse answers I've heard them all before .

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Any commercial pilot please do not answer this if you know the answer and give it away this is for the guys to exercise their brains in RAA or PPL pilots.

 

This question we got thrown as a hypothetical in one of senior commercial theory licence questions in class it was not in an actual exam – but a bit of fun by the instructor.

 

Accept the premise AND all assumptions.

 

So we have 50 tons of Canaries (yes little yellow birds) sitting in all the seats of a 747. No seats belts.

 

The 747 is flying at 35,000 feet straight and level.

 

Then all 50 tons of Canaries become airborne inside the 747 flying around.

 

The Question

 

  • What happens to the 747 In other words is it 50 tons lighter Or is it the same weight at that point in time.
  • If it is 50 tons lighter does THE 747 climb
  • If the 747 maintains it's flight level without climbing WHY?

 

 

Please explain your logic and process of YOUR answer.

 

No droll smart **** answers I've heard them all before .

The weight doesnt change because the air under their wings is deflected downwards to the floor so overall weight unchanged

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Makes no difference to the 747. It is carrying the internal air and the canaries, what they are doing internally doesn’t matter. (Answer from an engineer, not a professional pilot)

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The weight doesnt change because the air under their wings is deflected downwards to the floor so overall weight unchanged

I mean the air they have displaced just moves around without affecting total weight

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No effect at all! Except perhaps lots of feathers floating around the cabin and clogging up the A/C vents.

 

How did I go as a mere PPL?

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No change at all. The plane is on autopilot and the pilots are chatting up the hostess....

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2 bottles of red later this still hurts my brain to think about.?

Same here? Airlines are only retiring Jumbo's these days as they can't find 50 T of canary's, there's a shortage apparently!??

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African or European canaries?

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The question reminds me of a story my Dad used to tell of a truck driver who was carrying an overload of birds. As he drove onto the checking station weighbridge he began hitting the side of his truck. When asked why he was doing it, he replied that if he kept the birds flying, he wouldn't weigh heavy.

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The question reminds me of a story my Dad used to tell of a truck driver who was carrying an overload of birds. As he drove onto the checking station weighbridge he began hitting the side of his truck. When asked why he was doing it, he replied that if he kept the birds flying, he wouldn't weigh heavy.

Technically that's true. But like having a load of pallets on a truck sitting on a weigh bridge then one is lifted off by a fork lift just to clear the flad bed, instant less weight on the scale?

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The scientists calculated that the birds flying makes no weight difference in a tightly enclosed space. But if the birds took off into the open atmosphere - then for sure, the weight is off whatever they were sitting on.

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Here's another one for you - if you're in a spaceship travelling at the speed of light (suspend your disbelief), and another spaceship is on a head-on collision course also at the speed of light - what's the closing speed?

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Only massless particles can travel at the speed of light, so your question is impossible.

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Suspending that rule, they close at the speed of light. But perhaps from an outside observer they never meet because of time dilation?

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Depends on how they took off ...

1. If they jump upwards into the air using leg muscles to push off their entire weight by reaction to the seat to take off and do it all at once then the seats and airframe are having 50ton of downward force applied in an instant - apparent increase as you have applied muscular force not mass change. But once airborne and flying around in level flight in the cabin all 50ton are suspended within the air within the enclosed space and lift/mass are offset within the fuselage and no impact on the aircraft.

2. If they take off by pushing horizontally then the muscular force is acting against the direction of flight so I’d not like to think about what it does to airspeed in a short period.

 

But they are canaries so assuming most jump forward to start flight and they all go in random directions with their launch push from legs then it will net out to no impact.

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The answer depends on the position of the observer. To the pilot of each spaceship, the other spaceship is approaching at the speed of light. To an observer sitting on an asteroid watching them, they are approaching (closing speed) of twice the speed of light. It's Relativity, my dear Watson.

 

Now here's the rub! If both spaceships are travelling at the speed of light, then their electro-magnetic images would be travelling at the speed of light also. Therefore, neither helmsman would detect the other by sight or radar. Talk about the Big Bang!

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With the average weight of a canary being 15g, that's 3,333,333 canaries.
So the real question becomes how many canaries does it take to fill a 747?

 

But are we talking about a Classic, a -400, or even that cute little aberration they called the -SP?

 

If we assume we're talking about the Atlantic Canary, they range 10 to 12 cm (3.9 to 4.7 in) in length, with a wingspan of 21 to 23.7 cm. Split the difference and you get 11cm long and 22.25cm wingspan for an occupied area of 244.75cm2 per bird (Ref: Wikipedia)

 

A 747-400F has a main deck area of 21347ft2 occupied by pallets (Ref: Cargolux), probably a bit more if you account for the pallet-handling equipment, but we'll use that figure. So 21347ft2 gives 1983.2m2. Assuming a single-layer of birds that 1983.2m2 gives 19,832,012cm2 which means you can fit 81,278 canaries on the main deck of a 747-400. But we're still 3.2m canaries short of our goal.

 

To reach our needed 3.333333m canaries, we would need to have 41 layers of birds. Unfortunately, the Atlantic Canary's 1cm length means you can get 27 layers in the 300cm-high main deck.

 

So we have a figure of 27*81,278 or only 2,194,506 Atlantic Canaries weighing 32.917 tonnes in a CargoLux 747-400F

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The canaries maintain their flight by pushing the surrounding air down. This reacts with the cabin floor so there is no difference in the weight as long as the cabin is airtight.

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