Question 270-1 : Given an aeroplane with a propeller turning clockwise as seen from behind the torque effect during the take off run will tend to ? [ Analysis topography ]

Question 270-2 : A propeller is turning to the right when viewed from behind the asymmetric blade effect in the climb at low speed will ?

Yaw the aeroplane to the left.

When an aircraft is flying with a high angle of attack the 'bite' of the downward moving blade is greater than the 'bite' of the upward moving blade this moves the center of thrust to the right of the prop disc area causing a yawing moment toward the left around the vertical axis to prove this explanation is complex because it would be necessary to work wind vector problems on each blade while considering both the angle of attack of the aircraft and the angle of attack of each bladethis asymmetric loading is caused by the resultant velocity which is generated by the combination of the velocity of the propeller blade in its plane of rotation and the velocity of the air passing horizontally through the propeller disc with the aircraft being flown at positive aoas the right viewed from the rear or downswinging blade is passing through an area of resultant velocity which is greater than that affecting the left or upswinging bladesince the propeller blade is an airfoil increased velocity means increased lift the downswinging blade has more lift and tends to pull yaw the aircraft's nose to the leftwhen the aircraft is flying at a high angle of attack the downward moving blade has a higher resultant velocity creating more lift than the upward moving blade com encom080 663jpg

Question 270-3 : Which definition of propeller parameters is correct ?

Geometric pitch is the theoretical distance a propeller blade element would travel in a forward direction during one revolution.

Question 270-4 : An aeroplane is fitted with a constant speed propeller if the aeroplane speed increases while manifold pressure remains constant propeller pitch 1 and the propeller torque 2 will ?

1 increase 2 remain constant.

Constant manifold pressure assumes constant power with increasing forward airspeed the blade section angle of attack reduces if the blade angle remains unchanged the rpm would therefore increase to maintain the rpm the blade angle pitch must be increased thus increasing the torque and slowing the propeller to its original set rpmcoarse pitch is large blade angle low rpm and high forward airspeed fine pitch is small blade angle high rpm and low forward airspeed blade angle of attack is determined by rpm and tasthe question asks for the condition when all has stabilised again in the 'after' situation manifold pressure and rpm are back to the same as 'before' so torque must also be the same

Question 270-5 : The angle of attack of a fixed pitch propeller blade increases when ?

Rpm increases and forward velocity decreases.

For a fixed pitch propeller the pitch angle cannot be changed it varies from root to tip to maintain near constant angle of attack along the blade the angle of attack as in the case of a aircraft wing is defined as the angle between the chord line and relative airflow with a propeller however the relative airflow is the resultant of the airflow due to rotation and forward speed change either of these values and the angle of attack will change com encom080 549jpg

Question 270-6 : The angle of attack of a propeller blade element is the angle between the blade element chord line and the ?

Resultant air speed vector.

Question 270-7 : In twin engine aeroplanes with propellers turning clockwise as seen from behind ?

The left engine is the critical engine.

On a jet engines aeroplane you don't have the additional critical engine notion added to your engine failureexplanation clockwise rotation as viewed from the pilot's seat the critical engine will be the left engine com encom080 341jpgmulti engine aeroplanes are subject to p factor just as single engine aeroplanes are the descending propeller blade of each engine will produce greater thrust than the ascending blade when the aeroplane is operated under power and at positive angles of attack the descending propeller blade of the right engine is also a greater distance from the center of gravity and therefore has a longer moment arm than the descending propeller blade of the left engine as a result failure of the left engine will result in the most asymmetrical thrust adverse yaw as the right engine will be providing the remaining thrust

Question 270-8 : Which statement is correct regarding the gyroscopic effect of a clockwise propeller on a single engine aeroplane i pitch down produces left yawii left yaw produces pitch up ?

I is correct ii is correct.

Gyroscopic effect works like this if an up force is applied to the tail plane causing nose pitch down that would be the same as applying a forward force to the 12 o'clock position on the prop to cause the pitch down if this was a right hand propeller clockwise when viewed from the rear this force would then act at the 3 o'clock postion on the propeller in a forwards movement causing a yaw to the leftin this image try to imagine the forward force at any position and the effect that it will have on the attitude of flight com encom080 607apng clockwise propeller when viewed from the rear com encom080 607png

Question 270-9 : Select if the following statements are correct or incorrecti when the propeller tip speed is supersonic the prop noise doesn't increaseii when the propeller tip speed is supersonic it is less efficient ?

I incorrect ii correct.

Question 270-10 : For this question use the reference the diagram that correctly represents the propeller in the feathered position is err a 081 632 ?

Diagram 3.

The blade angle known as 'feather' describes the pitch that results in no or slow rotation of the propeller at a specific flight condition typically cruise with the engine shut downdue to the twist of the blade this angle is typically slightly less than 90 degrees com encom080 651jpg com encom080 632jpg example com encom080 651ajpgsaab sf340 inflight engine failure propeller feathered

Question 270-11 : For this question use the reference the diagram the letter which correctly represents the angle of advance helix angle is err a 081 636 ?

D.

com encom080 636jpghelix angle the angle that the actual path of the propeller makes to the plane of rotation

Question 270-12 : For an aeroplane equipped with a two position variable pitch propeller it is advisable to select a ?

Fine pitch for take off and climb.

com encom080 1175png pitch control coarse pitch is large blade angle low rpm and high forward airspeed fine pitch is small blade angle high rpm and low forward airspeed

Question 270-13 : Propeller efficiency is ?

The ratio of power available thrust * tas to shaft power torque * rpm.

Question 270-14 : Which of these statements concerning propellers is correct ?

The blade angle of a feathered propeller is approximately 90 degrees.

The propeller blade angle is the angle that the blade presents to the plane of rotation of the propeller the blade angle known as 'feather' describes the pitch that results in no or slow rotation of the propeller at a specific flight condition typically cruise with the engine shut downdue to the twist of the blade this angle is typically slightly less than 90 degrees com encom080 651jpg example com encom080 651ajpgsaab sf340 inflight engine failure propeller feathered

Question 270-15 : If s is the frontal area of the propeller disc propeller solidity is the ratio of ?

The total frontal area of all the blades to s.

Propeller solidity the ratio of the total blade area to the disc area

Question 270-16 : Which statement about propeller noise is correct i propeller noise increases when the blade tip speed increasesii for a given engine and propeller blade shape an increase in the number of propeller blades allows for a reduction in propeller noise ?

I is correct ii is correct.

A propeller must be able to absorb all the shaft power developed by the engine and also operate with maximum efficiency throughout the required performance envelope of the aircraft the critical factor is tip velocity if tip velocity is too high the blade tips will approach the local speed of sound and compressibility effects will decrease thrust and increase rotational drag supersonic tip speed will considerably reduce the efficiency of a propeller and greatly increase the noise it generatesin most installations increasing the number of blades helps to reduce noise cockpit noise comes from a variety of sources engine exhaust slipstream and the propeller vibrations are also perceived as noise in the cockpit a two blade propeller produces an inherent once per revolution vibration that shakes the airframe so a three blade propeller will be inherently smoother and therefore quieter etc

Question 270-17 : Which statement is correct regarding the gyroscopic effect of a clockwise rotating propeller on a single engine aeroplane i pitch down produces right yawii left yaw produces pitch down ?

I is incorrect ii is incorrect.

Gyroscopic effect works like this if an up force is applied to the tail plane causing nose pitch down that would be the same as applying a forward force to the 12 o'clock position on the prop to cause the pitch down if this was a right hand propeller clockwise when viewed from the rear this force would then act at the 3 o'clock postion on the propeller in a forwards movement causing a yaw to the leftin this image try to imagine the forward force at any position and the effect that it will have on the attitude of flight com encom080 607apng clockwise propeller when viewed from the rear com encom080 607png

Question 270-18 : The asymmetric blade effect on an single engine aeroplane with a clockwise rotating propeller ?

Produces left yaw.

Question 270-19 : The geometric pitch of a propeller is the ?

Theoretical distance a propeller would advance in one revolution at zero blade angle of attack.

If the propeller were to rotate one turn like a cork screw into a bottle of wine geometric pitch would be how far it travels into the cork if you can ignore tas and speed it is just a consideration of the blade angle and one rotation however it would not be a true distance at all stages of rotation like a corkscrew

Question 270-20 : For a given rpm of a fixed pitch propeller the blade angle of attack will ?

Decrease when the tas increases.

For a fixed pitch propeller the pitch angle cannot be changed it varies from root to tip to maintain near constant angle of attack along the blade the angle of attack as in the case of a aircraft wing is defined as the angle between the chord line and relative airflow with a propeller however the relative airflow is the resultant of the airflow due to rotation and forward speed change either of these values and the angle of attack will change com encom080 549jpg

Question 270-21 : For a fixed pitch propeller in flight at a given tas the blade angle of attack will ?

Increase if rpm increases.

For a fixed pitch propeller the pitch angle cannot be changed it varies from root to tip to maintain near constant angle of attack along the blade the angle of attack as in the case of a aircraft wing is defined as the angle between the chord line and relative airflow with a propeller however the relative airflow is the resultant of the airflow due to rotation and forward speed change either of these values and the angle of attack will change com encom080 549jpg

Question 270-22 : Which statement is correct for a propeller of given diameter and at constant rpm i assuming blade shape does not change power absorption increases if the number of blades increases ii power absorption increases if the mean chord of the blades increases ?

I is correct ii is correct.

Question 270-23 : Which statement about a propeller is correct i asymmetric blade effect increases when engine power is increasedii asymmetric blade effect increases when the angle between the propeller axis and airflow through the propeller disc increases ?

I is correct ii is correct.

When an aircraft is flying with a high angle of attack the 'bite' of the downward moving blade is greater than the 'bite' of the upward moving blade this moves the center of thrust to the right of the prop disc area causing a yawing moment toward the left around the vertical axis to prove this explanation is complex because it would be necessary to work wind vector problems on each blade while considering both the angle of attack of the aircraft and the angle of attack of each bladethis asymmetric loading is caused by the resultant velocity which is generated by the combination of the velocity of the propeller blade in its plane of rotation and the velocity of the air passing horizontally through the propeller disc with the aircraft being flown at positive aoas the right viewed from the rear or downswinging blade is passing through an area of resultant velocity which is greater than that affecting the left or upswinging bladesince the propeller blade is an airfoil increased velocity means increased lift the downswinging blade has more lift and tends to pull yaw the aircraft's nose to the leftwhen the aircraft is flying at a high angle of attack the downward moving blade has a higher resultant velocity creating more lift than the upward moving blade com encom080 663jpgthis might be easier to visualize if the propeller shaft was mounted perpendicular to the ground like a helicopter if there were no air movement at all except that generated by the propeller itself identical sections of each blade would have the same airspeed with air moving horizontally across this vertically mounted propeller the blade proceeding forward into the flow of air has a higher airspeed than the blade retreating with the airflow thus the blade proceeding into the horizontal airflow is creating more lift or thrust moving the center of thrust toward that blade visualize rotating the vertically mounted propeller shaft to shallower angles relative to the moving air as on an aircraft this unbalanced thrust then becomes proportionately smaller and continues getting smaller until it reaches the value of zero when the propeller shaft is exactly horizontal in relation to the moving airthe effects of each of these four elements of torque vary in value with changes in flight situations in one phase of flight one of these elements may be more prominent than another in another phase of flight another element may be more prominent the relationship of these values to each other varies with different aircraft depending on the airframe engine and propeller combinations as well as other design features to maintain positive control of the aircraft in all flight conditions the pilot must apply the flight controls as necessary to compensate for these varying values

Question 270-24 : Which statement is correct regarding a propeller i increasing tip speed to supersonic speed increases propeller noiseii increasing tip speed to supersonic speed increases propeller efficiency ?

I is correct ii is incorrect.

A propeller must be able to absorb all the shaft power developed by the engine and also operate with maximum efficiency throughout the required performance envelope of the aircraft the critical factor is tip velocity if tip velocity is too high the blade tips will approach the local speed of sound and compressibility effects will decrease thrust and increase rotational drag supersonic tip speed will considerably reduce the efficiency of a propeller and greatly increase the noise it generates

Question 270-25 : The blade angle of a propeller is usually referenced at ?

75 % of blade radius.

The blade angle is the angle formed between the propeller's plane of rotation and the chord line of its airfoil section it is expressed in degrees usually measured at 75% of the blade's radius

Question 270-26 : Which statement is correct i a propeller with a small blade angle is referred to as being in fine pitchii a propeller with a large blade angle is referred to as being in coarse pitch ?

Question 270-27 : Which statement is correct i a propeller with little blade twist is referred to as being in fine pitchii a propeller with significant blade twist is referred to as being in coarse pitch ?

I is incorrect ii is incorrect.

The reason a propeller is 'twisted' is that the outer parts of the propeller blades like all things that turn about a central point travel faster than the portions near the hub if the blades had the same geometric pitch throughout their lengths portions near the hub could have negative aoas while the propeller tips would be stalled at cruise speed twisting or variations in the geometric pitch of the blades permits the propeller to operate with a relatively constant aoa along its length when in cruising flightpropeller blades are twisted to change the blade angle in proportion to the differences in speed of rotation along the length of the propeller keeping thrust more nearly equalized along this length'little blade twist' is not refered to 'fine pitch' it refers to variation of the angle of attack along the lenght of the bladecoarse pitch is large blade anglefine pitch is small blade angle 885

Question 270-28 : Which statement is correct i propeller gyroscopic effect occurs during aeroplane pitch changesii propeller gyroscopic effect is most noticeable during low speed flight at high propeller rpm ?

I is correct ii is correct.

Propeller gyroscopic effect occurs during aeroplane pitch changes gyroscopic effect works like this if an up force is applied to the tail plane causing nose pitch down that would be the same as applying a forward force to the 12 o'clock position on the prop to cause the pitch down if this was a right hand propeller clockwise when viewed from the rear this force would then act at the 3 o'clock postion on the propeller in a forwards movement causing a yaw to the leftpropeller gyroscopic effect is most noticeable during low speed flight at high propeller rpm since at high speed a higher force is required to counteract the stability of the aircraft

Question 270-29 : Which statement is correct when comparing a fixed pitch propeller with a constant speed propeller i a constant speed propeller reduces fuel consumption over a range of cruise speeds ii a coarse fixed pitch propeller is more efficient during take off ?

I is correct ii is incorrect.

A constant speed propeller maintains near maximum efficiency over a wider range of aeroplane speeds than a fixed pitch propeller therefore a constant speed propeller reduces fuel consumption over a range of cruise speeds com encom080 1175png pitch control coarse pitch is large blade angle low rpm and high forward airspeed fine pitch is small blade angle high rpm and low forward airspeed

Question 270-30 : Which of these statements concerning propellers is correct ?

When compared with a non feathered propeller a feathered propeller improves the handling of a multi engine aeroplane with one engine inoperative.

Following an engine failure on a twin engine aeroplane the increased drag from the windmilling propeller will seriously degrade climb performance limit range and add to the yawing moment caused by the failed engine which will affect controllability also by continuing to turn a badly damaged engine eventual seizure of the engine or an engine fire might resultdrag from a windmilling propeller is high it is being driven by the relative airflow and is generating both drag and torque a feathered propeller generates the least drag there is no torque because it is not rotating and the parasite drag is a minimum because the blades are edge on to the relative airflowthe blade angle known as 'feather' describes the pitch that results in no or slow rotation of the propeller at a specific flight condition typically cruise with the engine shut downdue to the twist of the blade this angle is typically slightly less than 90 degrees com encom080 651jpg com encom080 632jpg example com encom080 651ajpgsaab sf340 inflight engine failure propeller feathered

Question 270-31 : The effective pitch of a propeller is the ?

Actual distance a propeller advances in one revolution.

907effective pitch is the actual distance a propeller advances in one revolution in the air the effective pitch is always shorter than geometric pitch due to the air is a fluid and always slip

Question 270-32 : Which statement is correct i propeller gyroscopic effect occurs during aeroplane yaw changesii propeller gyroscopic effect is most noticeable during low speed flight at high propeller rpm ?

I is correct ii is correct.

Propeller gyroscopic effect occurs during aeroplane pitch changes gyroscopic effect works like this if an up force is applied to the tail plane causing nose pitch down that would be the same as applying a forward force to the 12 o'clock position on the prop to cause the pitch down if this was a right hand propeller clockwise when viewed from the rear this force would then act at the 3 o'clock postion on the propeller in a forwards movement causing a yaw to the leftpropeller gyroscopic effect is most noticeable during low speed flight at high propeller rpm since at high speed a higher force is required to counteract the stability of the aircraft

Question 270-33 : Which statement about a propeller is correct i asymmetric blade effect is unaffected when engine power is increasedii asymmetric blade effect is independent of the angle between the propeller axis and the airflow through the propeller disc ?

I is incorrect ii is incorrect.

Question 270-34 : Which of these statements about propellers is correct or incorrect i a cruise propeller has a greater geometric pitch when compared with a climb propellerii a coarse pitch propeller is less efficient during take off and in the climb but more efficient in the cruise when compared with a fine pitch ?

I is correct ii is correct.

com encom080 1175png pitch control coarse pitch is large blade angle low rpm and high forward airspeed fine pitch is small blade angle high rpm and low forward airspeed

Question 270-35 : Which statement is correct regarding a windmilling propeller on a multi engine aeroplane ?

The windmilling drag is much higher than for a feathered propeller.

Following an engine failure on a twin engine aeroplane the increased drag from the windmilling propeller will seriously degrade climb performance limit range and add to the yawing moment caused by the failed engine which will affect controllability also by continuing to turn a badly damaged engine eventual seizure of the engine or an engine fire might resultdrag from a windmilling propeller is high it is being driven by the relative airflow and is generating both drag and torque a feathered propeller generates the least drag there is no torque because it is not rotating and the parasite drag is a minimum because the blades are edge on to the relative airflowthe blade angle known as 'feather' describes the pitch that results in no or slow rotation of the propeller at a specific flight condition typically cruise with the engine shut downdue to the twist of the blade this angle is typically slightly less than 90 degrees com encom080 651jpg com encom080 632jpg example com encom080 651ajpgsaab sf340 inflight engine failure propeller feathered

Question 270-36 : The angle of attack of a rotating propeller blade element shown in the annex is err a 081 973 ?

Angle 1.

com encom080 973jpg

Question 270-37 : The helix or advance angle of a rotating propeller blade element shown in the annex is err a 081 974 ?

Angle 3.

com encom080 973jpg

Question 270-38 : The blade angle of a rotating propeller blade element shown in the annex is err a 081 975 ?

Angle 2.

com encom080 973jpg

Question 270-39 : Propeller blade twist is the ?

Varying of the blade angle from the root to the tip of a propeller blade.

The pitch angle varies from root to tip to maintain a near constant angle of attack along the bladethe reason a propeller is 'twisted' is that the outer parts of the propeller blades like all things that turn about a central point travel faster than the portions near the hub if the blades had the same geometric pitch throughout their lengths portions near the hub could have negative aoas while the propeller tips would be stalled at cruise speed twisting or variations in the geometric pitch of the blades permits the propeller to operate with a relatively constant aoa along its length when in cruising flightpropeller blades are twisted to change the blade angle in proportion to the differences in speed of rotation along the length of the propeller keeping thrust more nearly equalized along this length

Question 270-40 : A rotating propeller blade element produces an aerodynamic force f that may be resolved into two components a force t perpendicular to the plane of rotation thrust a force r generating a torque absorbed by engine power the diagram representing a rotating propeller blade element during the cruise ?

Diagram 1.

com encom080 1001gif