Chapter 3 - Climbing, Descending, Turning and Stalls

Question 1

What is rate of climb (RoC)?

Answer 1

An aircraft’s vertical speed - the rate of positive altitude change with respect to time or distance.

RoC = Excess Power/Weight = Pav - Preq/Weight

Question 2

What determines an aircraft’s RoC?

Answer 2

The amount of additional power required to maintain the same airspeed as in level flight.

Question 3

What is angle of climb?

Answer 3

The ratio between distance travelled over the ground and altitude gained.

Question 4

What determines an aircraft’s angle of climb?

Answer 4

The amount of excess thrust left after opposing drag?

Question 5

How should the aircraft be flown to achieve the maximum angle of climb?

Answer 5

At the speed which gives the maximum difference between thrust and drag.

Question 6

How should the aircraft be flown to achieve the maximum rate of climb?

Answer 6

At the speed which gives the largest difference between power available and the power required (drag x airspeed, i.e. power needed to overcome drag)

Question 7

What is Vy?

Answer 7

The best rate of climb speed

Question 8

What is Vx?

Answer 8

The best angle of climb speed

Question 9

What is Vmu?

Answer 9

Minimum Unstick Speed

The calibrated airspeed at and above which the aircraft can safely lift off the ground and continue the take off.

Question 10

What is the best angle of climb speed, Vx, for a jet?

Answer 10

Vimd

Question 11

What is the best angle of climb speed, Vx, for a piston aircraft?

Answer 11

Just above Vmu (minimum unstick speed)

Question 12

What is ‘absolute ceiling’?

Answer 12

The altitude at which the maximum power available curve only just touches the power required curve and sustained RoC is no longer possible.

Question 13

What is ‘service ceiling’?

Answer 13

The altitude at which the maximum sustained rate of climb falls to 500fpm (100fpm for a piston aircraft).

Question 14

What affect does altitude have on climbing?

Answer 14

Thrust horsepower of an engine decreases.
Jet engines are more efficient, but power available is lowered.

Therefore, max angle of climb and best rate of climb will reduce?

Question 15

What are the two types of descent?

Answer 15

Powered Descent

Glide Descent

Question 16

How does power affect the descent of an aircraft?

Answer 16

It reduces the descent angle and increases the distance travelled over the ground, increasing the range from a given altitude.

Question 17

How do we fly an aircraft for endurance gliding?

Answer 17

Minimum rate of sink.

Question 18

For a given aircraft weight, at what speed is the rate of descent least?

Answer 18

The speed where the power required is least.

Question 19

What is range gliding and how do we fly to achieve it?

Answer 19

Range gliding is going as far as possible over the ground during the glide. It is achieved by flying at the aircraft’s optimum lift/drag ratio, Vimd (+ approx. 4 degrees AoA).

Question 20

How does altitude affect best gliding speed for a given weight?

Answer 20

It does not, the best gliding EAS is constant regardless of altitude. However, the rate of descent will decrease as lower altitudes are reached and the TAS reduces.

Question 21

How does wind affect gliding descents?

Answer 21

Tailwind INCREASES gliding RANGE

Headwind DECREASES gliding RANGE

Wind does NOT affect gliding endurance

Question 22

How does aircraft weight affect a glide descent?

Answer 22

Does not affect gliding angle

Range gliding is unchanged - higher rate of descent but travel further over that distance due to higher ground speed

Endurance gliding decreases with an increase in weight and vice versa

Question 23

What controls the Rate of Descent?

Answer 23

Power

More power = lower RoD

Question 24

Does banking affect the amount of lift produced?

Answer 24

No, but a component of the lift is angled in to the turn. Therefore, more lift needs to be produced to increase the vertical component of the lift. This is done by gently pulling back on the stick to increase AoA.

Higher AoA = More lift, therefore more LDD. Means a power increase is needed.

More bank = More lift needed = Larger increase in AoA = Larger increase in LDD = Larger increase in power required to maintain speed

I.e. additional thrust is proportional to the angle of bank.

Question 25

How does weight affect angle of bank required to turn at a set rate?

Answer 25

It does not, angle of bank remains the same. (More AoA needed though for a larger vertical lift force to oppose weight? - Check) If the same TAS and AoB can be obtained, the radius of turn is basically independent of the weight of the aircraft (limited by g-loading and aircraft tolerances).

Question 26

What is a minimum radius turn?

Answer 26

Achieving the turn in the smallest possible ground area.

Question 27

How is a minimum radius turn achieved?

Answer 27

Wing loading as low as possible Air as dense as possible Max value of the product of CL and AoB (CLmax) Higher TAS = Higher AoB possible = Smaller radius of turn I.e. min radius at infinite speed

Question 28

What is the equation for centripetal force (CPF)?

Answer 28

CPF = (W x V^2)/gr ``` V = TAS in mps g = Gravitational force r = Radius W = Weight ```

Question 29

How does the EAS for a min radius turn (in reality, not theory) change with increasing altitude?

Answer 29

It remains the same, but the radius of turn achieved at this speed increases. Due to a reduction in CLmax. Thrust also reduced at altitude.

Question 30

How is a max rate turn achieved?

Answer 30

Wing loading as low as possible. Air must be as dense as possible. Maximum value of the AoB, speed and CL value must be obtained. Note - Both max rate and min radius turns are flown at full power with max lift

Question 31

How does thrust affect max rate and min radius turns?

Answer 31

It contributes a vertical component into the turn, so reduces the lift needed from the wing or can help improve turn radius. Reduction in thrust with increasing altitude causes a reduction in turning performance.

Question 32

How does altitude affect max rate and min radius turns and why?

Answer 32

Increases both (worse performance) Due to less thrust from the engine, the TAS/EAS relationship and the reduction in CLmax.

Question 33

What is the approximate stalling AoA for aircraft like the Prefect?

Answer 33

15 degrees

Question 34

Note - Look at 1-3-4 Stalling, note the Pressure distribution with AoA interactive diagram.

Answer 34

Check NOW!

Question 35

What is the Centre of Pressure (CP) and how does it move with increasing AoA?

Answer 35

CP is the point where the lift force appears to be acting from. It moves forward as AoA increases, its furthest point forward being when CLmax is achieved. When the aircraft then stalls, the CP generally moves back along the chord.

Question 36

What is the boundary layer?

Answer 36

The layer of air extending from the surface to the point where no drag effect is discernible.

Question 37

What does the boundary layer determine in flight?

Answer 37

Maximum lift coefficient Stalling characteristics of a wing Value of form drag Certain high-speed characteristics of an aircraft

Question 38

What is Vb?

Answer 38

Stalling speed

Question 39

What is stalling speed?

Answer 39

The speed of an aircraft in flight at its maximum lift coefficient (CLmax).

Question 40

What are the key factors that change stalling speed (Vb)?

Answer 40

Change in weight (heavier = higher stalling speed) Manoeuvre (load factor, n) Configuration (changes in CLmax) Power and slipstream

Question 41

Is the AoA at which an aircraft stalls affected by weight?

Answer 41

No If weight increases the AoA required to maintain level flight is increased for a set speed, therefore the aircraft reached the crit AoA at a higher speed.

Question 42

How does AoB affect load factor?

Answer 42

Increasing AoB in a turn increases the load factor.

Question 43

What is the new stall speed in a turn?

Answer 43

Vb (normal stall speed) x Square root of g E.g. in a 4g turn, New stall speed = Vb x 2

Question 44

What is the 'thrust-line' affect of stalling?

Answer 44

Stalling speed will be SLIGHTLY reduced by the effect of power, due to some of the thrust being inclined upwards, contributing to lift. Aided by the flow of the prop slipstream over the lifting surfaces.