Why engines are placed under wings?

Placing engines on the wing provides beneficial wing bending relief in flight. The further the engines are away from the fuselage the greater the wing bending relief so engines buried in the wing root provide little relief.

Is a APU an engine?

The APU is a small jet engine which is normally located in the tail cone of the aircraft but, in some cases, is located in an engine nacelle or in the wheel well.

How many turbines are in the free turbine engine?

two
A typical free power-turbine engine has two independent counter-rotating turbines. One turbine drives the compressor, while the other drives the propeller through a reduction gearbox. The compressor in the basic engine consists of three axial flow compressor stages combined with a single centrifugal compressor stage.

Why are feathering propellers used on multi-engine aircraft?

Feathering propellers must be used on multi-engine aircraft to reduce propeller drag to a minimum under one or more engine failure conditions. A feathering propeller is a constant-speed propeller used on multi-engine aircraft that has a mechanism to change the pitch to an angle of approximately 90°.

What are some examples of multi-engine planes with pusher engines?

The Convair B36 is one notable multi-engine aircraft with engines in pusher configuration, as is the Piaggio Avanti. And the Cessna Skymaster is a push/pull configuration (If you get a multi-engine rating in a Skymaster, your ticket will be limited to multi-engine aircraft with in-line thrust).

What type of engines are used in turboprop aircraft?

[Figure 2] Large commuter aircraft use turboprop engines, such as the P&W 150 and AE2100 that can deliver up to 5,000 shaft horsepower to power mid-sized to large turboprop aircraft. [Figure 3] The turboprop propeller is operated by a gas turbine engine through a reduction-gear assembly.

What are the characteristics of the different types of propellers?

Various characteristics of several propeller types are discussed in the following article, but no attempt is made to cover all types of propellers. As the name implies, a fixed-pitch propeller has the blade pitch, or blade angle, built into the propeller. [Figure 1] The blade angle cannot be changed after the propeller is built.