why is the planes leaving white smoke in the sky???

Question

I come from south africa and i have never seen planes leaving white smoke in the air!!!
can anyone tell me why that happens???

Answer 1

Condensation trail.

This explains it well.
http://en.wikipedia.org/wiki/Contrail

Answer 2

It's not smoke. It is water vapour condensing from the jet engine exhaust.

This happens because the gasses leaving engine are very hot and the air at 30,000 + feet is very very cold. The water vapour condenses and the sunlight refracts through it and it shows up as a white trail extending for a mike or so behind the aeroplane.

If you ever see real smoke coming from an aeroplane then I suggest that you get out of the way very quickly because it may not be staying up for long.

Answer 3

Contrails are clouds of ice particles formed around the small particles (carbon) which are in aircraft exhaust. If the air is very dry, a contrail will not form behind the plane. If the air is somewhat moist, a contrail will form immediately behind the aircraft and make a bright white line that lasts for a short while

Whether contrails form depends on the temperature aloft as well as the amount of relative humidity in the air mass the plane is flying through. As the relative humidity in the atmosphere increases, the atmosphere is able to supply more moisture into the jet aircraft exhaust plume, and a contrail is more likely to form.

Therefore, the same jet won't always make contrails at the same altitude from day to day as atmospheric conditions vary.

You can use what is called an "Appleman chart" and the standard lapse rate to predict contrail formation for your area- http://asd-www.larc.nasa.gov/GLOBE/resources/activities/appleman_student.html

Answer 4

The white stuff is water vapour not smoke. Very tiny particles from the burning of fuel, form nucleation centres upon which water condenses. If the air is very warm and dry, there are no condensation trails.

Or, in the 3 days after 9/11, if there are no planes, there are no contrails.

Something similar happens in a pressurised drinks bottle when you release the pressure - bubbles form around any minute impurities.

Answer 5

When the air is cold it will leave white smoke trails. It is like the same idea when it is cold outside you can see your breath. Keep in mind airplanes fly high up in the sky and air is much cooler at a higher altitude. Just think of the snow on top of the mountains. Warmer weather you will not notice the white smoke trails as much.

Answer 6

Planes don't leave smoke. It is acually frozen water vapor and gases from the exhaust. The air is so cold up there that when it heats up it produces condensation. When the condensation goes into the -50 degree temperature it freezes and produces a white trail.

Answer 7

Planes leave white "smoke" behind them because the water vapour being exhausted from the jet engines condenses to form a cloud. This only occurs above 30,000ft a.s.l.

Answer 8

The International Civil Aviation Organization (ICAO) in conjunction with the Environmental Protection Agency (EPA) mandated, in 1983, that black smoke from civilian aircraft be processed through catalytic converters to turn it white. All ICAO members are bound by this memorandum (ibid) and that just about covers all civillian air operators. Notable exceptions are Papua New Guinea (PNG), Hutt River Province and three (I think, CIS countries). As a rule of thumb, if the country complies with the latest Noise Abatement Restrictions, then it also meets the (ICAO) Second Stage Carbon Masking Protocol. These regulations only apply to civilian aircraft, which explains why we still see older smoky and noisy military machines.

An interesting marriage of technology and politics has seen a move to eliminate ALL airline carbon pollutants and 85% noise pollution since 2002. Named operation Kangaroo 2012, Smoke and noise is captured and stored internally in wing mounted Duo Noise/Smoke Capsuals (DNSC). A large aircraft leasing company (an Australian company) has modified freight aircraft (18 L1011s, 11 DC10s and 43 B747s) for use by three large Air Freight companies to carry full DNSCs. These 72 aircraft are crewed and operated by the American night freight companies who fly full DNSCs into Darwin (Northern Territory). From there they are sent on the newly completed Alice Springs - Darwin rail way for storage (along with nuclear waste) in Central Australia. Some states in Australia are investigating off setting the financial devastation of the latest drought by storing the DNSCs and nuclear waste on drought ravaged land.

ICAO and the EPA estimate that Operation Kangaroo 2012 will need 122 pollution flights per week into Darwin to meet the requirements for 90% of projected passenger airline growth to 2012. The Australian Department of Immigration and Ethnic Affairs also reserves four flights per annum to repatriate illeagle immigrants (Boat People). Since the current use of Darwin International Airport by Operation Kangaroo 2012 average 82 flights per week over this calender year, the project would seem to be on-track.

Answer 9

Those are condensation trails. It's the interaction between the exhaust produced by the engines and the air. The air at that altitude becomes saturated with water vapor from the engine exhaust and forms the contrail clouds you see from the ground.

Answer 10

They are vapour trails left by aircraft exhaust fumes condensing in the air. Water vapour forms tiny droplets that collect around particles in the atmosphere. These are reflective, which is why they often appear to be white.

It is the same process that forms clouds.

Answer 11

A contrail is not smoke -

one of the by products of combustion is water vapor

temperatures drop one degree for every thousand feet of
altitude - so at 35,000 the oatside air temperature is about
20-40 degrees - BELOW zero

soooooooo- what you are seeing - are ice crystals

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