Whilst bored in my car, staring at the sky, in a traffic jam i found myself wondering,........?

Question

at what altitude does a plane need to be at to create a vapour trail?

Thank you all very much for your answers!

Answer 1

Depends on the temperature and humidity of the air. Anywhere from ground to upper atmosphere. It depends. In Alaska in the winter time, an aircraft can have a contrail right from takeoff. Half the ice and snow on the runways in polar regions is created by condensing moisture from aircraft engines on takeoff.

"Contrails are condensation trails (sometimes vapour trails): artificial cirrus clouds made by the exhaust of aircraft engines or wingtip vortices which precipitate a stream of tiny ice crystals in moist, frigid upper air. Contrary to appearances, they are not pollution as such.

Contrails are created in one of two ways:

1. First, the airplane's exhaust increases the amount of moisture in the air, which can push the water content of the air past saturation point. This causes condensation to occur, and the contrail to form.

Aviation fuel such as petrol/gasoline (piston engines) or paraffin/kerosene (jet engines) consists primarily of hydrocarbons. When the fuel is burned, the carbon combines with oxygen to form carbon dioxide; the hydrogen also combines with oxygen to form water, which emerges as steam in the exhaust. For every gallon of fuel burned, approximately one gallon of water is produced, in addition to the water already present as humidity in the air used to burn the fuel. At high altitudes this steam emerges into a cold environment, (as altitude increases, the atmospheric temperature drops) which lowers the temperature of the steam until it condenses into tiny water droplets and/or desublimates into ice. These millions of tiny water droplets and/or ice crystals form the contrails. The temperature drop (and therefore, time and distance) the steam needs to condense accounts for the contrail forming some way behind the aircraft's engines. The majority of the cloud content comes from water trapped in the surrounding air. At high altitudes, supercooled water vapour requires a trigger to encourage desublimation. The exhaust particles in the aircraft's exhaust act as this trigger, causing the trapped vapor to rapidly turn to ice crystals. Contrails will only occur when the outide air temperature around the aircraft is at or below -57 degrees centigrade.

2. The wings of an airplane cause a drop in air pressure in the vicinity of the wing (this is partly what allows a plane to fly). This drop in air pressure brings with it a drop in temperature, which can cause water to condense out of the air and form a contrail but only at higher altitudes. At lower altitudes, this phenomenon is also known as Ectoplasm. Ectoplasm is more commonly seen during high energy manouvers like those of a fighter jet, or on jet liners during takeoff and landing, at areas of very low pressure, including over the wings, and often around turbo-fan intakes on takeoff. See also Wing tip vorticies.

Exhaust contrails tend to be more stable and long-lasting than wing-tip contrails, which are often disrupted by the aircraft's wake and are commonly very short-lived."

Answer 2

Yes it's more to do with air temp. temperature and pressure decrease as altitude increases. Next time you see jets in the sky with vapour trails and one plane has a longer trail than the other then thats because it's at a greater altitude. But generally speaking on a average day I'd say about 20,000 ft for a vapour trail.

Answer 3

The air in the sky must be cold.
To make a vapor trail

because the heat coming from the tail of the plane is hot, and the air is super cold.

so it makes a trail.

It's about atmosphere (air around the jets or tail wind) not always necessarily altitude.

Answer 4

It can happen at any altitude. Depends upon atmospheric conditions.

Answer 5

it doesnt matter what altitude, that vapour trail you see is the pilot having a crafty ciggy with the window open............lol

Answer 6

6 miles

Answer 7

What a thing to think off when in your car thats the sort of thing you think about when in the toilet

Answer 8

Take off

Answer 9

Anywhere above freezing level

Answer 10

I don't have a clue, when in a car jam I usually fantasise about all the other drivers.....male ones...so next time you see me looking at you......................