ppl_05_e2
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ID: 3658
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 9: THE FOUR FORCES INCLUDING TURNING FLIGHT QUESTIONS
12.In this diagram, representing an aircraft in a banked attitude during turning fight, which vector represents total lift?
Use the diagram to answer the question.
a.A
b.B
c.C
d.W
13.Most light aircraft are designed so that, in fight, the centre of pressure is behind the centre of gravity. This means that in order to maintain straight and level fight:
a.the tailplane must produce a downwards force
b.the tailplane must produce an upwards force
c.the tailplane does not need to provide an upwards or a downwards force; it is only used to manoeuvre the aircraft
d.the tailplane does not need to produce an upwards or downwards force, the thrust/drag couple balances the forces
14.If the turn coordinator is indicating Rate 1, the aircraft is changing heading at:
a.3º per second
b.6º per second
c.360º per minute
d.90º per minute
15.An aircraft performs a steady level turn at 30º Angle of Bank at 80 knots IAS. If the level turn is maintained at the same IAS, but the Angle of Bank is increased to 45º, what will be the effect on the radius and rate of the turn?
a.The radius and rate of the turn will be increased
b.The radius of the turn will remain unchanged
c.The radius of the turn will be smaller, and the rate of the turn will increase.
d.For a given radius of turn, the aircraft can have only one airspeed
16.An aircraft’s rate of turn is dependent on:
a.the angle of bank and power available
b.the angle of bank and thrust available
c.the true airspeed and angle of bank
d.the indicated airspeed and the angle of attack
P.T.O
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Order: 6026
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 9: THE FOUR FORCES INCLUDING TURNING FLIGHT QUESTIONS
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The answers to these questions can be found at the end of this book.
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ID: 3658
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 10
LIFT AUGMENTATION
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Order: 6026
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 10: LIFT AUGMENTATION
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ID: 3658
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 10: LIFT AUGMENTATION
LIFT AUGMENTATION.
Take-Off and Landing.
When an aircraft takes off and lands, it is highly desirable that the lift force generated by its wing should be suffcient to support the weight of the aircraft at as low a speed as possible, so that take-off and landing distances will be as short as possible.
This state of affairs could be obtained by ftting a wing whose aerofoil section is thick and highly cambered such as the high-lift aerofoil depicted in Figure 10.1. You can see from the graph that this type of aerofoil section produces a higher coeffcient of lift, CL, for any given angle of attack.
Figure 10.1 CL MAX varies according to the type of aerofoil.
As you have learnt, in straight flight, angle of attack is directly related to airspeed. For the majority of light aircraft, 16°, just before the stall, is the angle of attack giving maximum CL, and that angle is, by definition, achieved at the slowest straight flight speed of which the aircraft is capable.
The speed corresponding to CL MAX in straight flight, therefore, is the aircraft’s straight flight stalling speed, and the higher the CL MAX the slower an aircraft will be able to fly before it stalls.
So a thick, highly-cambered wing would give an aircraft the highest value of lift at the lowest speeds, and provide an aircraft with the shortest take-off and landing run.
The Cruise.
But take-off and landing take up only a small period of time when considering the whole duration of an aircraft’s fight. The greater part of fight is spent in the cruise.
However, at high cruise speeds, a thickly-cambered wing-section would cause considerable drag and require the aircraft to fy in a pronounced nose down pitch attitude, as depicted in Figure 10.2 overleaf.
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Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 10: LIFT AUGMENTATION
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Figure 10.2 A representation of the effect of a high-camber wing on the cruise attitude. |
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It is usual, therefore, for designers to select an aerofoil with a less pronounced |
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camber to optimise the cruise, as in Figure 10.3, and then to modify the shape of the |
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aerofoil section by having mechanical, movable leading and trailing edges, known |
Flaps are used |
collectively as high-lift devices, to increase camber and, thus, CL for any given angle |
to reduce take- |
of attack. Using high-lift devices, the lift-force generated by an aerofoil can be |
off and landing |
maintained at the lower speeds of landing and take-off, and so reduce take-off and |
distances. |
landing distances. Figure 10.4 depicts both leading and trailing edge faps. |
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Using high-lift devices, a pilot may, in effect, convert his wing from a high speed wing |
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to a high lift wing as he wishes. |
Figure 10.3 Aerofoil shape optimised for the cruise.
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Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 10: LIFT AUGMENTATION
Leading and trailing edge flaps increase the camber of a wing.
Figure 10.4 High lift devices mechanically alter the camber of an aerofoil to maintain lift at lower speeds.
TRAILING EDGE FLAPS.
The most common of the high lift devices used on light aircraft are trailing edge faps. A fap is a hinged section of the trailing edge of the wing which can be defected downwards, and so produce an increase in camber. But as well as increasing CL through the increase in camber, trailing edge faps will also increase drag.
Figure 10.5 Turning final with initial flap lowered.
The faps seldom extend the whole length of the trailing edge since the ailerons are also ftted to the outer sections of the wing trailing edge. (See Figure 10.5).
Operation of the Flaps.
The faps are operated by the pilot in the cockpit. The controlling mechanism can be purely mechanical or powered electrically, hydraulically or pneumatically. The mechanical system of fap operation provides the pilot with a lever in the cockpit which is connected via rods or cables to the faps.
With mechanically operated faps it is the pilot who provides the force to actuate the system.
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Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 10: LIFT AUGMENTATION
Flaps |
With a powered fap system, the pilot operates a switch in the cockpit in order to |
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deploy the faps. (See Figure 10.6). |
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increase |
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lift but also |
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drag. |
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Figure 10.6 Powered operation of the flaps.
Most aircraft have a range of fap settings that allow fap to be selected in stages. Stages of fap are usually measured in degrees. The Piper PA28 Warrior allows fap selection in stages of 10º, 25º and 40º degrees. Other aircraft may have different settings. The angle of defection of the fap is measured from the chord line of the fap to the chord line of the main aerofoil section, as shown in Figure 10.7.
Figure 10.7 Flap angle is measured between the aerofoil and flap chord lines.
Flap Setting Indications.
The pilot needs to have an indication of the fap setting selected. Figure 10.8 shows various arrangements that are commonly in use. There may be markings at the base of the manual fap lever, detents on a switched power system or a gauge indicating fap position.
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ID: 3658
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 10: LIFT AUGMENTATION
Figure 10.8 Methods of indicating flap angle.
TYPES OF TRAILING EDGE FLAP.
There are several types of trailing edge fap in use.
The Plain Flap.
The plain fap, depicted in Figure 10.9, is simple in construction and gives a good
increase in CLMAX, but also causes a large increase in drag. The plain fap is used mainly on low speed aircraft where very short take-off and landing performance is
not required.
Figure 10.9 The plain flap.
The Split Flap.
The split fap forms part of the surface of the lower trailing edge, the upper surface contour being unaffected when the fap is lowered, as can be seen in Figure 10.10, overleaf. The split fap gives a slightly higher CLMAX than the plain fap at higher angles of attack, but drag is also higher since the depth of turbulent air behind the wing is greater, when a split fap is deployed.
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Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
Customer: Oleg Ostapenko E-mail: ostapenko2002@yahoo.com
CHAPTER 10: LIFT AUGMENTATION
Figure 10.10 The split flap.
Slotted flaps re-energises the flow over the wing
Fowler flaps increase both
the camber and the
surface area of the wing.
The Slotted Flap.
The slotted fap depicted in Figure 10.11, is much more complex in construction than either the plain or split fap. For the same area of fap, the slotted fap gives a greater
increase in CLMAX and produces less drag than both the plain and split faps. This is achieved by directing high pressure air from below the wing through the slots formed
between the fap and the trailing edge. The re-direction of airfow, in this way has the effect of re-energising the boundary layer and so delaying separation. See Figure 10.11.
Figure 10.11 The slotted fap.
The Fowler Flap.
The Fowler Flap, depicted in Figure 10.12, not only increases camber but also wing area, S. You will recall that S is a factor in the lift formula: Lift = CL ½ ρ v² S, where S is the surface area of the wing.
The Fowler Flap produces the largest increase in CLMAX of all fap types. Because the Fowler Flap increases chord length as well as wing camber, the thickness/chord
ratio is reduced, leading to a reduction in drag. Larger aircraft usually have slotted
Fowler faps which are even more effcient.
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