Questions on "Engines [Gas Turbines]"

[Turbine D]

Truefaith,

$2000 per answered question is rather pricy, even with pics of scantily clad women thrown in at no additional cost.

Might I suggest you start with this book which costs about $100 US.

Aircraft Gas Turbine Engine Technology written by Irwin E. Treager
ISBN 0-02-801828-1 Glencoe/McGraw-Hill

[lomapaseo]

Reading a book won't help some people. Just sell them the answer that they can memorize.

understanding only helps if someday you want to use the information

[Smilin_Ed]

Truly Amazing

This is a truly amazing thread.

[Slasher]

Ok fair enough. 2,000 bucks for 200 answers I admit is rather
pricey, so yeh alright I'll throw in 100 pics of buxom scantily
clad women for truefaith free. Here's a sample if John the Tulla
doesn't mind -



You won't find THAT in Aircraft Gas Turbine Engine Technology!

How much just for the pictures of buxom, scantily-clad women?

I provide em free down in the JB dungeon Hedge. You know that!

[Brian Abraham]

Slasher, I bet if you pricked those they'ed go ppppsssstttt - jet reaction just like a gas turbine. Not scantily clad either that one, false advertising.

[rudderrudderrat]

Hi Truefaith,

Slasher has posted a splendid picture of a pair of governor bob weights. As you can imagine, if they were rotated more quickly (rpm increase), they would move out. If the rpm decreased, they would move back in.
I'd have gone for D - twice.

Q16. If engine power is increased with propeller lever in the constant speed range rpm increase, then:
(a) Governor weights move out, blade angle decrease, rpm decrease, weights remain
(b) Governor weights move in, blade angle increase, rpm decrease, weights move out
(c) Governor weights move out, blade angle increase, rpm decrease, weights move in
(d) Governor weights move out, blade angle increase, rpm decrease, weights move in, blade angle decrease again
Not sure is it correct? I chose (c)

Edit Thanks BOAC, I agree, E is probably better

[BOAC]

rrat - why are they called 'bob'? Are they both called 'bob'? You sure you didn't miss an 'o'?

I would disagree with 'D' by the way - "DD" or 'E'.

[V1... Ooops]

Originally Posted by truefaith

Q3. Taking air from compressor for pressurisation and engine deicing will result in:
(a) high EGT and high specific fuel consumption
(b) low EGT and low specific fuel consumption
(c) high EGT and low specific fuel consumption

Q4. Engine running at constant RPM for a free turbine engine the RPM:
(a) cannot be increased
(b) maybe increased by increased torque pressure
(c) can be increased by propellers

Wow, I don't envy you having to write this test. The test questions are (in my opinion, anyway) rather poorly constructed - more of a test of interpretation of grammar and syntax than a test of aviation knowledge.

Anyway, concerning the two questions directly above:

Question 3: If you remove compressed air from the engine for airframe use (pressurization, de-ice, etc.), the combustion chamber temperature will increase and the fuel consumption will increase. This is because you are providing less cooling air to the combustion chamber (you're stealing it to use it in the airframe), and you will need to burn additional fuel to 'make up' the air that you have stolen from the engine to use in the airframe.

Question 4: In a free turbine engine such as a PT-6, the gas generator (the aft, compressor section) RPM is set by the power lever. The power lever sets the governing speed of the compressor. If you vary the rotational speed of the propeller (the forward, power section), this will result in a change in torque indication, but it will not affect the RPM of the gas generator.

Hope this information helps you figure out what the most appropriate of the answers offered is.

Michael

[V1... Ooops]

Originally Posted by truefaith

Q17. When the plane goes into descent without increasing power with RPM, airspeed increases, what does the CSU do to maintain constant RPM
(a) increase the blade angle
(b) to remain covered by fuel irrespective of the aircraft attitude
(c) decrease the blade angle
(d) maintain blade angle

The key to figuring out this question is to consider what would happen to the speed of the propeller if the aircraft airspeed increased (for example, in a descent) and the propeller governor took no action - in other words, if the propeller governor did not change the blade angle as it is supposed to.

If the speed of the aircraft increases (with no change to engine power setting, as would be the case if you just nosed over into a descent) and the propeller governor took no action, the speed of the propeller would also increase.

The purpose of the propeller governor is to keep the propeller turning at a constant RPM regardless of aircraft speed. So, if the speed of the aircraft increases (and the power setting is not changed), the propeller governor will increase the blade angle of the propeller - so that the propeller 'takes a bigger bite of the air' with each turn - and the propeller speed thus remains constant at the speed that the pilot has set using the propeller RPM control.

Similarly, if you attempt to climb without changing the power setting, the aircraft will slow down a bit, and the propeller governor will reduce the propeller blade angle so that the propeller 'takes a smaller bite of the air' with each revolution, and thus maintains the speed you have set with the propeller RPM control.

Michael

[ChristiaanJ]

Originally Posted by Slasher

Its what I've known for a long time - Tech Log is just a quick way of getting free answers for slobs who are too bloody lazy
to put in the necessary hard work and study.

A bit unfair, really, Slasher.
Not all of the readers here are test pilots with full engineering degrees, and thousands of hours on both civil and military aircraft.
I've seen answers to questions here I couldn't have found anywhere else.

CJ

[barit1]

When in high school, I encountered a standardized test question that went something like this:

A 100 ohm resistor is dissipating 10 watts. If it is replaced by a 50 ohm resistor, and everything else is unchanged, how much power will be dissipated?

To which I pondered: you can maintain a constant supply voltage, in which case current (and power) will double. OR - you can maintain a constant current, in which case voltage (and power) will be reduced to half. But (by definition) you cannot keep both voltage and current constant!

I answered it as if voltage remained constant, because I was sure the test-writer never comprehended any other way.

[barit1]

Turbine D:

Might I suggest you start with this book which costs about $100 US.

Aircraft Gas Turbine Engine Technology written by Irwin E. Treager
ISBN 0-02-801828-1 Glencoe/McGraw-Hill

Professor Treager was my instructor at Purdue nearly 50 years ago. One of the best!

[Slasher]

Not scantily clad either that one, false advertising.

If I had've posted anything stronger BA, John Tulla would've
banned me!

A bit unfair, really, Slasher.

'

Ok CJ I'll rephrase - Tech Log is just a quick way of getting
free answers for some slobs who are too bloody lazy to put in
the necessary hard work and study.