Questions : Propellers
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Questions : Propellers
Hello all:!
One again i've got some troubles in solving a few of my atpl questions. So thank you for those who will take the time necessary to answer those following (boring
) questions.
Here they are :
1- With a Constant Speed Unit (CSU) fitted, the pitch of the blades at fully 'FINE' and 'FEATHERED' is limited by :
a) engine oil forming a hydraulic lock.
b) mechanical stops.
c) by the pitch lever.
d) by the reverse pitch control lever.
I would go for B, but quite unsure.
2- Where is the greatest mechanical load felt on a propeller?
a) at the tip.
b) at the Master Station.
c) at the hub.
d) at the spinner.
Would say A.
3- A blade with a high camber :
a) absorbs less power than one with low camber.
b) is less affected by CTM (centrifugal twisting moment) than one with low camber.
c) aborbs more power than one with low camber.
d) is less affected by ATM (aerodynamic twisting moment) than one with a low camber.
4- An electrical feathering pump is used to :
a) feather the propeller only.
b) unfeather the propeller only.
c) do both of the above operations.
d) increase the picth on electrically controlled propellers.
5- A left handed propeller, when viewed from the front, turns :
a) clockwise.
b) anti-clockwise.
I don't understand where is the "datum' upon which we can determine the sense of rotation of a propeller. As regards to this question, shall we see the motion of the propeller from the front (facing it) or from the flight deck? I would rather say from the flight deck (which is the common way i think), which would therefore mean that answer A is correct. Actually the word "handed" bothers me : i see a guy manually handling the propeller which would mean that the datum would be "when facing the plane".
Many thanks folks ! Hope my english was not too aweful.
One again i've got some troubles in solving a few of my atpl questions. So thank you for those who will take the time necessary to answer those following (boring
) questions.Here they are :
1- With a Constant Speed Unit (CSU) fitted, the pitch of the blades at fully 'FINE' and 'FEATHERED' is limited by :
a) engine oil forming a hydraulic lock.
b) mechanical stops.
c) by the pitch lever.
d) by the reverse pitch control lever.
I would go for B, but quite unsure.
2- Where is the greatest mechanical load felt on a propeller?
a) at the tip.
b) at the Master Station.
c) at the hub.
d) at the spinner.
Would say A.
3- A blade with a high camber :
a) absorbs less power than one with low camber.
b) is less affected by CTM (centrifugal twisting moment) than one with low camber.
c) aborbs more power than one with low camber.
d) is less affected by ATM (aerodynamic twisting moment) than one with a low camber.
4- An electrical feathering pump is used to :
a) feather the propeller only.
b) unfeather the propeller only.
c) do both of the above operations.
d) increase the picth on electrically controlled propellers.
5- A left handed propeller, when viewed from the front, turns :
a) clockwise.
b) anti-clockwise.
I don't understand where is the "datum' upon which we can determine the sense of rotation of a propeller. As regards to this question, shall we see the motion of the propeller from the front (facing it) or from the flight deck? I would rather say from the flight deck (which is the common way i think), which would therefore mean that answer A is correct.
Actually the word "handed" bothers me : i see a guy manually handling the propeller which would mean that the datum would be "when facing the plane".Many thanks folks ! Hope my english was not too aweful.
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Hi Thibau
These are odd looking questions. Are they from the CQB?
Q1 Mechanical stops. The flight fine pitch stop can be varied to prevent a sudden massive selection of fully fine, and can be withdrawn to allow the prop to go to ground fine and reverse pitch
Q2 What do they mean by "mechanical load" and "propeller"? The accepted statement is that bending twisting and thrust forces put maximum stress on the blade root and the blade hub attachment point
Q3 Cambered blade sections can absorb more engine power - they are high lift/high drag sections. I don't see that a change in camber only would affect ATM or CTM
Q4 The electric feathering pump is there to ensure feathering if engine oil pressure is lost
Q5 It's a convention. A right hand tractor propeller has the top blade moving to the right when seen from the pilots seat, ie, clockwise when seen from behind
Do the hands of a clock go round clockwise or anticlockwise? Answer, normally clockwise, but not when seen from the clock
Dick
These are odd looking questions. Are they from the CQB?
Q1 Mechanical stops. The flight fine pitch stop can be varied to prevent a sudden massive selection of fully fine, and can be withdrawn to allow the prop to go to ground fine and reverse pitch
Q2 What do they mean by "mechanical load" and "propeller"? The accepted statement is that bending twisting and thrust forces put maximum stress on the blade root and the blade hub attachment point
Q3 Cambered blade sections can absorb more engine power - they are high lift/high drag sections. I don't see that a change in camber only would affect ATM or CTM
Q4 The electric feathering pump is there to ensure feathering if engine oil pressure is lost
Q5 It's a convention. A right hand tractor propeller has the top blade moving to the right when seen from the pilots seat, ie, clockwise when seen from behind
Do the hands of a clock go round clockwise or anticlockwise? Answer, normally clockwise, but not when seen from the clock
Dick
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By the way, i 've got a last question as regards to propellers.
"Superfine" pitch on a turbine powered aircraft :
a) provides more power at high altitude.
b) aids in windmilling and relighting the engine.
c) provides more power at low altitude.
d) requires less power for starting.
I would say answer D.
"Superfine" pitch on a turbine powered aircraft :
a) provides more power at high altitude.
b) aids in windmilling and relighting the engine.
c) provides more power at low altitude.
d) requires less power for starting.
I would say answer D.
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The first versions of turbo-prop engines were nothing more than standard jet engines with the compressor shaft extended forward to a reduction gearbox to drive the prop.
This arrangement meant that during starting, the starter motor also had to drive the prop. This obviously increased the load on the starter motor.
To overcome this problem some props had a superfine pitch setting that set the blades to zero blade angle. This made it easier for the starter motor to spin up the prop during starting.
Most modern turbo-props use a Free Power Turbine to drive the prop. These are not connected to the main spool of the engine in any way. So the starter no longer needs to spin up the prop during starting.
In the question as stated in your post the answer is D.
But some modern turbo-props still use superfine pitch for a different purpose. By setting the blades to superfine in flight they produce a great deal of extra drag. This process is called “Disking”. It enables the aircraft to achieve steeper descent paths without gaining excessive airspeed.
This arrangement meant that during starting, the starter motor also had to drive the prop. This obviously increased the load on the starter motor.
To overcome this problem some props had a superfine pitch setting that set the blades to zero blade angle. This made it easier for the starter motor to spin up the prop during starting.
Most modern turbo-props use a Free Power Turbine to drive the prop. These are not connected to the main spool of the engine in any way. So the starter no longer needs to spin up the prop during starting.
In the question as stated in your post the answer is D.
But some modern turbo-props still use superfine pitch for a different purpose. By setting the blades to superfine in flight they produce a great deal of extra drag. This process is called “Disking”. It enables the aircraft to achieve steeper descent paths without gaining excessive airspeed.
