Contents
What causes a contrail behind an airplane?
The combination of water vapor in aircraft engine exhaust and the low ambient temperatures that often exists at these high altitudes allows the formation of contrails. Contrails are composed primarily of water (in the form of ice crystals) and do not pose health risks to humans.
Do prop planes make contrails?
Contrails can be formed by propeller or jet turbine powered aircraft. During WWII, large formations of bombers left strikingly remarkable contrail formations. Typical contrails are shown below. The contrails formed by the exhaust at high altitude are typically white and very similar to cirrus clouds.
At what altitude do contrails form?
The exhaust particles in the aircraft’s exhaust act as this trigger, causing the trapped vapor to condense rapidly. Exhaust contrails usually form at high altitudes; usually above 8,000 m (26,000 ft), where the air temperature is below −36.5 °C (−34 °F).
What does the APU do on an airplane?
The APU is designed to provide electrical, bleed air (for environmental control, and for starting other engines), and in some cases they may run other accessories. It may be possible to have more power available to the main engine (s) if the APU is used for electrical, bleed air, etc. Normally, this is not done in most aircraft.
Is it possible to fly without an APU?
The biggest downside to operating without an APU is the lack of decent air conditioning during taxi and ground operations. Other considerations for operating without an APU are airplane specific. For example, the EMB-145 has two generators per engine and one on the APU for a total of five generators.
Can a car run if the APU is not connected?
Yes it is. Without the APU the airconditioning and electronics also won’t work when the engines are shut down, so a ground power unit is connected to provide the electricity and enough compressed air to run the air-conditioning.
What happens when the APU is shut down?
Without the APU the airconditioning and electronics also won’t work when the engines are shut down, so a ground power unit is connected to provide the electricity and enough compressed air to run the air-conditioning. Starting the engines will need a air start unit to start one of the engines using compressed air provided by hoses.