Does a plane fly in an arc?

Question

If an aircraft was to fly from eg: Sydney Australia to LAX @ 30,000 feet or what ever their altitude is, once the aircraft reaches its altitude does the plane fly in an arc or does the pilot have to avoid crashing into the stratisphere and head into outter space ?

Answer 1

Aeroplanes do not fly at a constant height above the ground. Planes measure their height above the ground using an altimeter which is a modified barometer. The height is calibrated from the air pressure outside. The instrument is set to the standard atmosphere of 1013hPa above 20,000 ft and to the area pressure setting, called the Area QNH, below that. On landing and take-off the altimeter is set to the aerodrome pressure or QNH.

This means that planes are flying at constant pressure levels not constant altitudes. It is for this reason that upper level weather charts are drawn at constant pressures - 700hPa, 500hPa, 300hPa etc - rather than constant altitudes.

As everyone's altimeter is set to the same QNH, there is no danger of planes flying into each other if they maintain separation.

(QNH, by the way, is part of the old Q code used in Morse and flag signals. It means "Set your altimeter to XXXX to show your height above sea level")

Returning to the question. As planes are flying on a constant pressure level, they are rising in areas of high pressure and descending in areas of low pressure so their track across the Pacific would be like a series of waves. The people on board the plane don't notice it.

Answer 2

Well, by maintaining its altitude then the plane does technically fly in an arc, although from the point of view of the plane itself it is retaining a constant height above the ground.

To fly in a straight line relative to the earth it would require the plane to increase altitude, and to be able to head into outer space it would requite so much energy to do so it would need to be propelled by a rocket engine.

Which, I suppose is why rockets do the space exploration, and planes do the low-altitude stuff.

Answer 3

On long flights, commercial jets fly level at close to 35,000 feet elevation, just below the troposphere-stratosphere boundary. Rlative to the *surface* of the earth, they are flying "flat". However, relative to the *center* of the earth they are flying in an arc parallel to the surface; the arc is of radius equal to the length of the line segment between the plane and the center of the earth.

As far as the pilot and instruments are concerned on board, the plane is flying level.

Answer 4

Not sure what you're asking, but I suppose if you're flying along a Great Circle route, it could technically be considered an arc. There's NO chance of a plane accidentally 'crashing' into the stratosphere and flying into space, though.

Answer 5

They maintain a constant altitude with respect to the ground, so they are in no danger of flying into space.

HTH

Charles

Answer 6

the pilot just keeps the same alltitude off the earth that why they have the meters and they wouldnt crash into the stratisphere the plane would stall out

Answer 7

Yes.