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ATPL - Performance > Thrust, Drag and Lift > Flashcards

Thrust, Drag and Lift Flashcards

1
Q

Thrust on low by-pass ratio engines reduces initially because of … and then increases slightly but steadily above … with improved …

A

intake momentum drag

M0.4

mass flow

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2
Q

what is intake momentum drag?

A

The air entering the intake is slowed down and loses momentum before it is again accelerated

decreases the overall thrust of the engine and it increases with increasing Mach No

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3
Q

Jet thrust … generally with increasing altitude due to …

A

decreases

reduced density

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4
Q

Jet thrust limited by one of two things, which are?

A

TGT limit

RPM limit

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5
Q

On hot days … limit is reached before … limit

A

TGT

RPM

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6
Q

when the TGT is limiting, a reduction in OAT allows an …

A

increase in RPM and a subsequent increase in thrust

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7
Q

As long as max thrust is regulated by the RPM limit, it will be almost … and independent of …

A

constant

temperature

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8
Q

at high temps thrust varies with … but at low temps, usually below about …, the thrust is constant and the engine is said to be …

A

temp

ISA+15

flat rated

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9
Q

As the mass of air entering the engine changes the FCU will adjust the fuel flow to maintain the optimum air to fuel ratio of around …

An increase in density will … fuel flow and vice versa

A

15:1

increase

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10
Q

jet power is rate of application of …, defined as …

A

thrust

thrust x speed

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11
Q

If we assume that jet thrust is relatively constant then power … as speed increases

A

increases

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12
Q

jet power also … with increasing altitude for the same speed because …

It will also decrease with … temperature

A

decreases

the amount of thrust decreases with altitude

increasing

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13
Q

propeller thrust produced depends on the … of the blade, which in turn depends on the …

A

angle of attack

airspeed and induced airflow through the propeller

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14
Q

At low airspeeds the AOA through the propeller will be …, and thrust will be ….

As forward speed builds the angle of attack … and thrust …

A

large, near to the stall

maximum

decreases

reduces

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15
Q

maximum thrust of a propeller driven aircraft is … at zero forward speed and … with increasing forward speed

A

maximum

reduces

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16
Q

Shape of drag curve different for propeller and jet aircraft because they are designed to fly at different speeds, Vmd on a jet is …

A

higher

17
Q

what is the speed unstable regime?

A

at speeds less than Vmd, a reduction in speed leads to an increase in drag, which in turn reduces speed further and increases drag more and so on

18
Q

wha is the speed stable regime?

A

Above Vmd an increase in airspeed also increases drag but this tends to restore the original airspeed

19
Q

when flaps are deployed, because lift delivered is unchanged, the lift induced drag is hardly changed. Selection of the flaps does increase profile drag, which in turn reduces … and …

A

Vmd

Vs

20
Q

If induced drag increases Vmd occurs at a … speed, if profile drag increases Vmd occurs at a … speed

A

higher

lower

21
Q

Effect of mass on induced drag can be estimated coarsely. The induced drag is proportional to …

A

the square of the aircraft weight

(if weight increases by 10% or a factor of 1.1 then the induced drag will increase by 1.1squared or 1.21)

22
Q

Can also roughly estimate the increase or decrease of Vmd with an increase or decrease in weight. Vmd varies by …

A

the square root of the weight change

23
Q

Effect of speed changes on drag can also be coarsely estimated. At a constant weight:

profile drag is protortional to …

induced drag is proportional to …

(both are speeds)

A

V squared

1 / V squared (inversley proportional)

24
Q

Max forward speed in level flight is achieved where the thrust available intersects the … curve, which is where …

A

total drag

max thrust equals drag

25
Q

In 1g conditions at constant mass and without extending flaps the angle of attack increases as … reduces and vice versa. This means that, if we can determine how IAS changes, we can determine how the angle of attack changes

We can us the … graph to determine what will happen to IAS if climbing at a constant Mach No for example and will therefore be able to calculate what happens to …

A

IAS

IAS

ECTM

alpha

26
Q

Power available is … and therefore power required is …

A

thrust x TAS

thrust x drag

27
Q

The total drag curve is IAS squared and if we now multiply it by another speed, TAS, we get the … curve which is …

Changes in mass and flap affect the power required curve in the same way as the drag curve but to a … value as this is an …

A

total power required

IAS cubed

greater

IAS cubed curve

28
Q

As mass increases the induced drag increases and thus the …

The … remains unchanged so the total power curve moves …, the total power required … and Vmp …

A

induced power required increases

parasite power required

up

increases

increases

29
Q

Increasing the flap increases the … drag which in turn increases the …

The total power required curve moves …, the total power required … and Vmp …

A

parasite

parasite power required

up

increases

decreases

30
Q

Increasing alt or temp increases the TAS for a given …

The total power required curve moves … and … and the total power required … and Vmp … as a TAS

A

IAS

up

right

increases

increases

ATPL - Performance (14 decks)

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