what is meant with: "...than the reactions of the air against the earth’s surface"

[RealQuax]

Hi there,

In ICAO-annexes definitions, an aircraft is defined as: "Any machine that can derive support in the atmosphere from the reactions of the air other than the reactions of the air against the earth’s surface."

What the heck is a machine which flies with the reactions of the air against the earths surface?

clueless,

Realquax

[Inverted Flat Spin]

I think a hovercraft?

[Luc Lion]

It's an hovercraft or an ekranoplan.
Luc

[mad_jock]

A kite

but i have to add more words for the forum

[forget]

Kite? :confused: ...........................

[FCS Explorer]

" the reactions of the air against the earth’s surface" -> wind?

[Pugilistic Animus]

s used in Subchapters A through K of this chapter, unless the context requires otherwise:
Administrator means the Federal Aviation Administrator or any person to whom he has delegated his authority in the matter concerned.
Aerodynamic coefficients means non-dimensional coefficients for aerodynamic forces and moments.
Air carrier means a person who undertakes directly by lease, or other arrangement, to engage in air transportation.
Air commerce means interstate, overseas, or foreign air commerce or the transportation of mail by aircraft or any operation or navigation of aircraft within the limits of any Federal airway or any operation or navigation of aircraft which directly affects, or which may endanger safety in, interstate, overseas, or foreign air commerce.
Aircraft means a device that is used or intended to be used for flight in the air.
Aircraft engine means an engine that is used or intended to be used for propelling aircraft. It includes turbosuperchargers, appurtenances, and accessories necessary for its functioning, but does not include propellers.
Airframe means the fuselage, booms, nacelles, cowlings, fairings, airfoil surfaces (including rotors but excluding propellers and rotating airfoils of engines), and landing gear of an aircraft and their accessories and controls.
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.


:E

[mad_jock]

Aye the reaction to the earths surface is via the bit of string.

Cut the string and it stops flying

[Pugilistic Animus]

just like a recent conversation

...A rocket leans on the air

....No, the rocket is driven upwards by it's equal and opposite reactions of the gasses from the exhaust...

...blah blah blah..... wiki....blah, blah.......and....blah blah blah

...So, how does it work in space with no air?

.....:uhoh:

.....:E

[hvogt]

Quax,

in the nineteen sixties ICAO decided air cushion vehicles were no aircraft. The respective definition was then amended by the words in question as to incorporate the decision. Here (http://www.icao.int/icao/en/nr/1967/pio196719_e.pdf) is a press release explaining more or less the same.

[Milt]

The weight of all aircraft in level flight always impinges on the earth's surface. They just make the atmosphere heavier just as the weight of a ship on the sea is supported by the sea bottom.

How can it be otherwise?

[bookworm]

in the nineteen sixties ICAO decided air cushion vehicles were no aircraft. The respective definition was then amended by the words in question as to incorporate the decision.

That ICAO has been relying on bad physics for more than 40 years doesn't make it less bad!

Vehicle pushes on air and air pushes back on vehicle. Air pushes on ground and ground pushes back on air. Newton is happy. Works for all vehicles that use the air as a medium.

There's no testable difference in the physics between an aircraft and a hovercraft/ekranoplan. The FAA has the right idea.

[Bruce Wayne]

Works for all vehicles that use the air as a medium


that pretty much covers most things.

not many work particularly well in a vacuum. :hmm:


The FAA has the right idea. Today 13:53

The FAA has the right idea


Yup.

JAA/EASA regs [sic] are littered with someone taking a cut and paste of the FAA regs then using the thesaurus function in word to a.) justify their existence and b.) trying to make it original. :E

[Mr Optimistic]

A force and its 'reaction' act on different bodies: are you all going mad ?

[rudderrudderrat]

There's no testable difference in the physics between an aircraft and a hovercraft/ekranoplan

If you measured the static air pressure under a hovercraft, then surely it must be bigger than ambient. That pressure difference * Area = weight of craft.

If an aircraft overflies a static air pressure sensor on the ground, I think the delta pressure is almost zero. (especially the higher it flies)

[Mr Optimistic]

Reminds me of an old physics question about hauling a truck load of birds up a hill. Do it once with them all perched then again with them all flying, any difference in the effort required ? Answer is no because of the delta pressure caused by their little beating wings.

[bookworm]

If an aircraft overflies a static air pressure sensor on the ground, I think the delta pressure is almost zero. (especially the higher it flies)

"delta pressure" is indeed "almost zero", but that very small "delta pressure" is increased over a very large area. As the aircraft moves out of ground effect and flies higher and higher, the area increases and the "delta pressure" gets smaller and smaller. But the product of the two is always equal to the weight of the aircraft.

[cwatters]

Since a kite doesn't rely on "the reactions of the air against the earth’s surface." it appears a kite meets that particular definition of an aircraft.

If a kite isn't an aircraft does a winch launched glider only become an aircraft once it drops the cable :)

[RealQuax]

Thanks for the clarification! And the link.

Realquax

[Capt Pit Bull]

Since a kite doesn't rely on "the reactions of the air against the earth’s surface

Sure about that?