lehpron
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How Is An Airplane Defined, Exactly?

Mon Jul 21, 2003 7:13 am

i always assumed that no matter how fast or how high, as long as a vehicle used air to lift itself and used air in it's engines and flew within the atmosphere, then it's an airplane. to what degree does/can this differ?

the problem is that i came to a conclusion recently than the only way to make very highspeed travel practical is to deal with the extreme friction heat by dumping it in space. this thing spends a third of it's time out there but it still uses an air-breathing accelerator. i personally feel offending refering this unknown as a spaceplane as it cannot ever stay out there, not fast enough.
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
m717
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RE: How Is An Airplane Defined, Exactly?

Mon Jul 21, 2003 7:27 am

"Airplane" as defined by Part 1 - Definitions - of Title 14 (Aeronautics and Space) of the Code of Federal Regulations:

Airplane means an engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings.

 
ybacpa
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RE: How Is An Airplane Defined, Exactly?

Mon Jul 21, 2003 11:11 am

M717,
Out of curosity, what is the official definition of a 'fixed-wing' aircraft? Technically, wouldn't (if it had been built) the 777 with folding wings option not fall under this classification? Also, and being the novice I am I can't reference an exact model, don't some military fighter aircraft have wings that substantially change shape in flight (i.e. from a traditional wing to a delta wing)?

Thanks,
yb


[Edited 2003-07-21 04:12:24]
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desertjets
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RE: How Is An Airplane Defined, Exactly?

Mon Jul 21, 2003 11:20 am

Folding wings for the purpose of improving storage is still fixed wing. a non-fixed wing would be a bird, or a helicopter (rotary wing).
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m717
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RE: How Is An Airplane Defined, Exactly?

Mon Jul 21, 2003 11:37 am

yb,

DesertJets is correct. Even though certain aircraft may have folding wings or variable shape wings (such as the B-1), these are still "fixed wing aircraft", as opposed to "rotary wing aircraft" (helicopters/rotorcraft).
 
jhooper
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RE: How Is An Airplane Defined, Exactly?

Mon Jul 21, 2003 5:04 pm

You raise an interesting philosophical question. When I took an Intro to Philosophy class, one of the questions the prof posed to us what "What exactly is a dog?" One could define a dog by the way it barks (but you don't need to listen to it bark to know it's a dog). One could define a cat by its whiskers (but if I clipped my cat's whiskers it would still be a cat). Then we started studying "forms", etc. What we see is merely a shadow of what is really there.

So what exactly makes an airplane an airplane. I guess it's "airplaneness?"
 Big thumbs up

[Edited 2003-07-21 10:04:56]
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buckfifty
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RE: How Is An Airplane Defined, Exactly?

Mon Jul 21, 2003 11:28 pm

Definitions change all the time with ever increasing development. Languages change everyday. Today, airplanes are just that, with a defined definition (whether ICAO or FAR's). Who knows what it could be 50 years down the line, with perhaps a whole new generation of propulsive techniques. (Anti gravity, anyone?)

I suppose in rhetorical questioning a spaceplane can also be defined as an airplane when travelling in the atmosphere. Though in light of its extra capabilities of travelling outside (not technically outside, but close enough) the atmosphere, I think to call it a spaceplane is not too outlandish.
 
lehpron
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RE: How Is An Airplane Defined, Exactly?

Tue Jul 22, 2003 4:20 am

"Airplane means an engine-driven fixed-wing aircraft heavier than air, that is supported in flight by the dynamic reaction of the air against its wings.
"

Question 1 : what's an aircraft?

Question 2 : what about lifting bodies? they don't use wings, they use their fuselages, but they still abide by the pressure difference law so i guess it doesn't matter.

as wing the folding/swing wing issue, i guess it depends on what is used when. if they are on the ground then they could be anything; like we could be airplanes, technically. but if we fell out of the sky, we wouldn't be planes, we'd be dead.  Smile


So Buckfifty, if you were in a vehicle cruising @ M12.0 and FL2000 while running on scramjets, would you be in an airplane?

See whenever i talk about hypersonic flight in here, most people assume and conclude that i am refering to space flight (which sounds like an oxymoron) and nothing in between, so i thought maybe my definitions were off.
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
m717
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RE: How Is An Airplane Defined, Exactly?

Tue Jul 22, 2003 9:53 am

Lehpron,

Answer to question 1: "what's an aircraft?"

Again, courtesy of Part 1-Definitions, Title 14 CFR

Aircraft means a device that is used or intended to be used for flight in the air.

Can't help you with Question 2. Big grin
 
lehpron
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RE: How Is An Airplane Defined, Exactly?

Wed Jul 23, 2003 5:53 am

10Q again M717. where did you find these definitions from? I may have other inquiries in the future, like for example max tire pressure or rate of decent from commercial re-entry into atmosphere (the last one can't exist yet right?) ?
The meaning of life is curiosity; we were put on this planet to explore opportunities.
 
m717
Posts: 540
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RE: How Is An Airplane Defined, Exactly?

Wed Jul 23, 2003 9:16 am

Lehpron,

The definitions I quoted are from Part 1 of the FARs (or another way of saying it is Chapter 1, Title 14 of the Code of Federal Regulations). I will post a link to the CFR online, and you can browse any chapter you choose. Again, chapter 1.1 are the definitions.

Link to the CFR online:

http://www.access.gpo.gov/nara/cfr/cfrhtml_00/Title_14/14tab_00.html
 
buckfifty
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RE: How Is An Airplane Defined, Exactly?

Thu Jul 24, 2003 4:46 pm

The X-15, for example, was termed as an airplane, not a spaceplane, 'cruised' at FL350, and made Mach 6 something.

Now, the earth's atmosphere, technically (according to NASA anyway, as I just checked) extends up to 650km (or 372 nm) amsl. Anything beyond that ('the exosphere' included) is pretty much considered space.

Now, the space shuttle itself orbits at an altitude of around 210 nm, which is within the Thermosphere. So it also does not technically 'fly around' in space. Yet I haven't heard of anyone calling the Space Shuttle an 'airplane'. At the most, it's a combination of 'rocket' and 'glider', but it cannot support powered flight on it's own.

So if you have a hypersonic a/c travelling at the speeds and altitude you mentioned, I'd assume that calling it a 'spaceplane' is quite feasible. Yes, it does travel within the atmos, but not in a conventional manner.

But that's just my opinion.

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