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How long does it take to restart a jet engine?
It can take from a few seconds to eternity. If the core cools down, the engine might lock up. Windmilling starts are only possible if the aircraft is flying fast and low enough. It will assist the startup process, but needs additional help from the starter or bleed air, typically below 300 knots and above 20,000 ft.
How are jet engines throttled?
Modern jet aircraft technically don’t use throttles; rather they are equipped with thrust levers which are connected to a Fuel Control Unit (FCU).
How long do jet engines need to warm up?
They require warming up the engines in stages which involves several increases in power corresponding to increases in temperatures until such time as take-off power can be accepted by the engine without turbine or shaft failure. The procedure usually takes 10 to 15 minutes an a cold day.
How does air density affect a jet engine’s restart altitude?
A jet engine requires (compressed) air, fuel and a flame source for (re)starting. So air density plays an important part in determining the maximum restart altitude. In addition, there are other factors at play as well.
What is the maximum altitude a pilot can attempt a restart/relight?
On all the turbojets that I have flown the maximum altitude a pilot can attempt a restart is 30,000 FT MSL. What factors go in to deciding what the maximum altitude is for an engine restart / relight? Basically, it gives the pilot the altitude and airspeed at which the engines can be relighted in flight.
How do planes fly at such high altitudes?
The air gets fed into the cylinders directly for combustion, and as the air becomes thinner as you go higher and higher, the engine loses its ability to create much needed power. However, there are turbocharged piston engine aircraft that are able to cruise at very high altitudes (25 to even 34,000 ft).
What are the advantages of a jet engine?
Jet engines have the ability to compress air and increase its pressure. This increases the mass flow rate through the engine enabling it to produce thrust at higher altitudes.