More worthless trivia!

[ananoman]

What does N1 and N2 refer to?

Where does bleed air come from? What is it used for?

What is a blisk? (it is a part in some new light jet engines)?

What is the difference between a vapor cycle and an air cycle machine?

Why would it be necessary to turn off bleed air to the air conditioning packs prior to takeoff?

What two types of compressors are used in jet engines? What are the advantages and disadvantages of each?

What part of the wing will stall first on the airplane you are currently flying? How does this compare to the stall characteristics of a swept wing?

Aircraft piston engines are commonly referred to by a series of letters and numbers. What do they refer to in the following examples?
O-320, IO-360, LO-360, R-4360, GSIO-480, GTSIO-520, AIO-360, AEIO-540, V-1710

Why would an aircraft use an inverted engine? (The D.H. Chipmunk is a good example)

What is the difference between a wet sump and a dry sump engine?

Why would certain engines have pressurized magnetos?

Describe the difference between a wet and a dry vacuum pump. What are the advantages and disadvantages of each?

Describe the common de-ice and anti-icing systems commonly used on aircraft. What are their advantages and disadvantages?

 

[JHines]

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What does N1 and N2 refer to?

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N1 = RPM of LPT (fan) shaft in a gas turbine engine
N2 = RPM of HPT (gas generator shaft) in a gas turbine engine.

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Where does bleed air come from? What is it used for?

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Usually, different points in the high pressure compressor. Used for turbine clearance control, engine frame deicing, hot section cooling, airframe deicing, and to run A/C equipment

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What is a blisk? (it is a part in some new light jet engines)?

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It's a "bladed disk" - a compressor or turbine wheel where the hub is integral with the blades.

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What is the difference between a vapor cycle and an air cycle machine?

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vapor cycle machine uses a refrigerant which undergoes a phase change during the cycle. Air cycle machine uses gaseous air.

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Why would it be necessary to turn off bleed air to the air conditioning packs prior to takeoff?

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Because they depend on compressor bleed air. Bleeding off air that the compressor has already performed work on reduces available thrust and/or increases fuel consumption to achieve the same thrust.

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What two types of compressors are used in jet engines? What are the advantages and disadvantages of each?

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Centrifugal and axial. Centrifugal are more compact and simpler. Axial can achieve higher pressure ratios and mass flow rates and make it much simpler to implement multiple stages. There are also mixed flow types which are a combination.

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What part of the wing will stall first on the airplane you are currently flying? How does this compare to the stall characteristics of a swept wing?

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The root. Swept wing = tips.

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Aircraft piston engines are commonly referred to by a series of letters and numbers. What do they refer to in the following examples?
O-320, IO-360, LO-360, R-4360, GSIO-480, GTSIO-520, AIO-360, AEIO-540, V-1710

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O = opposed, I = fuel injected, R = radial, G = gear reduction, T = turbocharged, A = aerobatic, V = vee=type. The numbers are the displacements in cubic inches. L = ?

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Why would an aircraft use an inverted engine? (The D.H. Chipmunk is a good example)

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Typically to improve visibility over the cowl.

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What is the difference between a wet sump and a dry sump engine?

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Wet sump = lubricating oil returned to a low-mounted sump which maintains a supply of oil. Dry sump = oil is continuously scavenged from the sump by the oil pump.

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Why would certain engines have pressurized magnetos?

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To avoid high altitude misfiring.

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Describe the difference between a wet and a dry vacuum pump. What are the advantages and disadvantages of each?

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Wet = uses "total loss" lubrication in which oil is supplied, lubricates the pump internals, and then drains overboard. Messy but has a long life and a predictable (i.e. gradual) failure mode.
Dry = uses "self-lubricating" carbon vanes running in a metallic chamber. Basically maintenance free and clean, but subject to sudden failure w/o warning at the end of its useful life.



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Describe the common de-ice and anti-icing systems commonly used on aircraft. What are their advantages and disadvantages?

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Pneumatic boots = relatively cheap, pneumatic power system is failure prone, boots not particularly durable.
Heated wings = simple, durable, requires heat-resistant structure and source of hot bleed air
Weeping wings = durable, reliable, expensive, uses fluid rapidly
Electro-expulsive = durable, expensive, complex.

 

[Alchemy]

L in the engine designation is for a left turning prop (counterclockwise when viewed from the rear).

 

[moxiepilot]

nice job jhines - you stole my thunder /ubbthreads/images/graemlins/frown.gif

 

[ananoman]

You guys did pretty good. I have just a few minor notes.
[ QUOTE ]

Aircraft piston engines are commonly referred to by a series of letters and numbers. What do they refer to in the following examples?
O-320, IO-360, LO-360, R-4360, GSIO-480, GTSIO-520, AIO-360, AEIO-540, V-1710

O = opposed, I = fuel injected, R = radial, G = gear reduction, T = turbocharged, A = aerobatic, V = vee=type. The numbers are the displacements in cubic inches. L = ?

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The only one you guys missed is the 'S' for supercharged. If there is a 'TS' the engine is Turbosupercharged , if there is only an 'S' the engine is Supercharged by a gear driven supercharger. (The commonly used term 'turbocharged' is really a shortened form of turbosupercharged, which is the correct term, even though few now use it.)

As others have mentioned 'L' is commonly used to denote counter clockwise rotation. There was also an engine put out by Continental that was liquid cooled and I believe this was also referred to as 'L'. The only thing that keeps this from getting confusing is that the liquid cooled engines were only used on some RAM conversions of the big Cessna twins and the Extra 500, which was not a sales success.

As far as I know there are two variations of the aerobatic Lycomings. The older AIO-360 used a dry sump oil system. The newer AEIO series is a wet sump without an external oil tank.

I am still wondering how to denote an inline engine. In cars they usually use an 'L', but this will not help us here.

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Why would an aircraft use an inverted engine? (The D.H. Chipmunk is a good example)



Typically to improve visibility over the cowl.

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This is true, but the main reason is prop clearance. On an inline or 'V' type engine the crankshaft is normally at the bottom of the engine. To get enough ground clearance, you would have to have abnormally long landing gear, and conventional gear would be mandatory. By turning the engine upside down, the crankshaft and the prop are moved higher away from the ground.