flight performance and planning for ppng member

PPL FP & P

FLIGHT PERFORMANCE

AND PLANNING I

PPL FP & P

LECTURE ONE: VIRTUALLY ALL YOU NEED TO KNOW

1. Mass and Balance

2. Take off Performance

3. Landing Performance

4. En-route Performance – Climbs, Cruise, Descents

PPL FP & P

MASS AND BALANCE

MASS is measured in kilogrammes (kg) and is a reflection of how much

matter something contains

An object’s mass does not change wherever it is

WEIGHT is a force measured in Newtons (N)

An object’s weight is its mass multiplied by gravity

Astronaut weight on earth

= 120 kg x 10

= 1200 N

On earth, 1 kg creates a force of 10 N

Astronaut weight on moon

= 120 kg x 1.6

= 200 N

In aviation we refer to MASS and not weight

PPL FP & P

MASS AND BALANCE: BASIC EMPTY MASS

Airframe

Engine

Fixed Equipment

Unusable Fuel

Full Oil

Items necessary for flight

Used for Loading Calculations

PPL FP & P

MASS AND BALANCE: EMPTY MASS

Airframe

Engine

Fixed Equipment

Unusable Fuel

Undrainable Oil

Items necessary for flight

Specified in Flight Manual after weighing

PPL FP & P

MASS AND BALANCE: GROSS MASS

Basic Empty Mass

Pilot

Payload (Passengers + Cargo)

Ballast

Fuel

+ + + +

PPL FP & P

MASS AND BALANCE: ZERO FUEL MASS

Basic Empty Mass

Payload (Passengers + Cargo)

Pilot

Ballast

No Usable Fuel

Structural Limitation

+ + +

PPL FP & P

MASS AND BALANCE: RAMP, TAKE-OFF, LANDING

MAXIMUM RAMP WEIGHT

Maximum permitted mass prior to taxi

May be maximum take-off weight + taxi fuel (3kg for C172)

MAXIMUM TAKE OFF MASS (MTOM)

Maximum allowable gross mass permitted for take-off

MAXIMUM LANDING MASS (MLM)

Maximum allowable gross mass permitted for landing

Same as MTOM for most light aircraft

If not may require fuel burn / dump prior to land

PPL FP & P

MASS AND BALANCE: RAMP, TAKE-OFF, LANDING

MTOM and MLM may have another

value which concerns performance

May be used when:

short runway

high obstacle on approach / climb out

unfavourable wind

unfavourable slope

high temperature

high pressure altitude

PPL FP & P

MASS AND BALANCE: WHY?

Aircraft mass is balanced by lift

Lift is a function of airspeed and air density

Airspeed is limited by power available from engine / propeller

Air density is out of pilot control

Flying an overweight plane is a very bad idea because:

PPL FP & P

MASS AND BALANCE: WHY?

Higher Stalling Speed

Higher Take-off Speed Required

Greater Braking Requirements

Lower Service Ceiling

Lower Endurance

Higher Landing Speed

Worse Climb Performance

Less manoeuvrability

Longer Take-off Run

Longer Landing Distance

Higher Fuel Consumption

Shorter Range

PPL FP & P

PRACTICE QUESTION!

“Which of the following statements about an overweight aircraft are true?:

(a) Higher stalling speed

(b) longer take off run required

(c) improved performance

(d) poor handling”

(a), (b) and (d)

PPL FP & P

WEIGHTS: CONVERTING UNITS

It is VITAL that you use the correct units when calculating mass and balance

LITRES

IMP GAL

KG

POUNDS

US GAL

(Weights based on

AVGAS (SG 0.72))

3.8

4.5

1.2

1.58

6.0

7.2

0.72

2.72

3.27

2.2

PPL FP & P

FUEL WEIGHT

1 litre of water weighs 1 kg

1 imperial gallon of water weighs 10 lb

Avgas is lighter than water and has a

specific gravity of 0.72

1 imperial gallon of Avgas weighs 7.2 lb

1 US gallon of Avgas weighs 6 lb

PPL FP & P

PRACTICE QUESTION!

“What is the weight of 120 litres of AVGAS (SG 0.72)?”

120 litres x 0.72 = 86.4 kg

PPL FP & P

FORCES, MOMENTS & DATUMS: DEFINITIONS

A MOMENT is the tendency of a force to twist or rotate an object

The MOMENT ARM is the distance from the point of rotation to the action of the force

Moment = Force x Distance

BALANCE occurs when the moments are equal

The DATUM can be selected anywhere and is the point from which

the MOMENT ARMS are measured

PPL FP & P


A balanced example – no resultant turning moment

1 m 2 m

6 kg

Datum

Weight x Distance = Moment Weight x Distance = Moment

6 x 1 = 6 3 x 2 = 6

Moments are equal so no

turning forces and are in

balance

3 kg

PPL FP & P


Choice of Datum does not change the result – same example, different datum

Weight x Distance = Moment

6 x 1 = 6

Weight x Distance = Moment

3 x 2 = 6

Moments are equal so no

turning forces and are in

balance

6 kg 3 kg

2 m

Datum

1 m

PPL FP & P


Moments are either clockwise or anticlockwise

Anticlockwise rotation

Units used for moments may be

pounds/inches or

kilograms/millimetres

PPL FP & P

WHY IS BALANCE IMPORTANT TO AIRCRAFT LOADING?

Loading of an aircraft determines where its centre of gravity will be

If an aircraft is loaded incorrectly the worst-case scenario on the ground is:

!

Airborne there might be other issues

PPL FP & P

CENTRE OF GRAVITY

Straight and Level Flight Lift equals weight and thrust equals drag

Four forces lead to two couples which are not always in balance

The tail plane is used to provide forces to balance this

The tail plane rotates the aircraft around its centre of gravity

Thrust

Weight

Drag

Lift

Centre of Gravity (CG)

PPL FP & P

CENTRE OF GRAVITY

Any movement of the centre of pressure (for lift) or the centre of gravity (for

weight) will require a balancing force from the tail plane


If the CG is too far forward the moment

arm to the tail plane is long

The aircraft is very stable in pitch

Forward CG position is limited to avoid a nose-heavy aircraft

which would be difficult to pitch up (especially for take-off

and landing when speed is slower)

PPL FP & P

CENTRE OF GRAVITY


If the CG is too far forward the moment

arm to the tail plane is short

The aircraft is less stable in pitch

Rear CG position is limited so the aircraft’s natural ability to

retain a steady pitch is maintained and so elevator “feel” is

normal

PPL FP & P

CENTRE OF GRAVITY

The CG of an aircraft changes in flight normally due to fuel usage

It is safer to establish the aircraft’s loading at both take-off mass and as zero-

fuel mass to ensure the limits are not exceeded during flight

Take-off mass

Zero-fuel mass

PPL FP & P

CENTRE OF GRAVITY

Usually fuel tanks are located near the CG so that the weight reduction

does not change the CG position greatly

Every aircraft has a Centre of Gravity Envelope which

must be adhered to

PPL FP & P

CENTRE OF GRAVITY

280

5

0

1448

11200

320

0

-

147 6174

1595 52235

52235 ÷ 1595 = 32.7” AFT OF DATUM

PPL FP & P

CENTRE OF GRAVITY

Our weight = 1595 lbs Within Limits

Our Centre of Gravity 32.74” aft Within limits

Or we can enter the information

on the graph for our aircraft

PPL FP & P

CENTRE OF GRAVITY

1595 lb

32.7”

x

Zero fuel CG

location

Zero fuel

weight

x

PPL FP & P

PRACTICE QUESTION!

“Aircraft has a take off weight of 1600 lbs and a centre of gravity of 36.4” aft of

the datum. If it uses 100 lbs of fuel (32” aft of datum), where will the centre of

gravity be for landing?”

1600 lbs x 36.4” = 58240 (moment)

100 lbs x 32” = 3200 (moment)

New moment = 58240 – 3200 = 55040

New weight = 1600 lbs – 100 lbs = 1500 lbs

New Centre of Gravity = 55040 (moment) ÷1500 lbs = 36.69” aft

PPL FP & P

Take-off distance available

(TODA)

Take-off run available

(TORA)

Clearway

1st

significant

obstruction

TORA, TODA, Clearway

TAKE-OFF PERFORMANCE : DEFINITIONS

PPL FP & P

Accelerate-Stop Distance Available

(ASDA)


(TORA) Stopway

1st

significant

obstruction

Accelerate-Stop Distance Available

(ASDA)


(TORA) No

stopway

available


PPL FP & P


Measured Take-off distance is the measured distance it takes for

an aircraft to accelerate on a dry paved surface and to get

airborne and climb to a screen height of 50 feet

Assumes: All engines operating at maximum power

Speed not less than Take-off Safety Speed (TOSS) / V2

TOSS is at least 20% margin over the stall (1.2VS)

PPL FP & P

PRACTICE QUESTION!

“The length of a take-off run available plus a clearway is also known as the?”

Take off Distance Available (TODA)

PPL FP & P

TAKE-OFF PERFORMANCE : FACTORS AFFECTING

FLAP SETTING

Original

Lift-off

point

Earlier

Lift-off

point

Clean take-

off (no flap)

Take-off

(with flap)

Flap REDUCES ground roll

Flap REDUCES rate/angle of climb by reducing the lift/drag ratio

50ft

PPL FP & P


WEIGHT

Increased weight INCREASES ground roll (longer to get to 1.2VS)

Increased weight DEGRADES climb performance

50ft

Original

Lift-off

point

Heavier

Lift-off

point

PPL FP & P


DENSITY ALTITUDE

Increased density altitude INCREASES take-off roll

Increased density altitude DECREASES climb performance

Original

Lift-off

point

Increased

density

altitude

Lift-off

point

Density altitude increases due to lower air pressure or higher

air temperatures which both reduce engine power effectiveness

PPL FP & P


HUMIDITY

Increased humidity INCREASES take-off roll

Increased humidity DECREASES climb performance

Original

Lift-off

point

Increased

humidity

Lift-off

point

Increase humidity decreases aerodynamic and engine

performance by effectively lowering air density (less air

molecules to do the work)

PPL FP & P


WIND

Still Wind

Head Wind

Tail Wind

PPL FP & P


WINDSHEAR

Nil wind

gradient

Windshear is wind that differs in strength and direction from one place to another

Usually wind increases with height – assisting climb gradient

If wind decreases with height it will degrade climb gradient

PPL FP & P


RUNWAY SURFACE

Paved level surface

Wet long grass

Mud / Sand

Surface may retard acceleration and lengthen ground run

PPL FP & P

RUNWAY SLOPE


Paved level surface

Upslope

Slope assists or retards acceleration to VTOSS

PPL FP & P


RUNWAY SLOPE

So you know slope affects take-off performance but how do you

know what the slope of a runway is?

The UK AIP has all the runway statistics:

Wycombe 17 elevation 516 feet, 35 elevation 482 ft,

length of runway 695 m

PPL FP & P


RUNWAY SLOPE

Over 695 m our runway gains / loses 34 feet in height

(34 feet ÷ 695m) x 100 = 4.8% slope

Not as bad as this!

PPL FP & P

CROSSWINDS


All aircraft have a crosswind limitation

Crosswinds weathercock the aircraft into

wind and the rudder is used to oppose this

Crosswinds try to lift the into-wind wing

and aileron is used to oppose this

When calculating crosswind make

sure to use common units (degrees

magnetic normally)

PPL FP & P


CROSSWINDS

No

crosswind

Complete Crosswind

30° off – crosswind ½ wind strength

45° off – crosswind wind strength

60° off – crosswind wind strength

Example: On runway 24, wind

300/20 crosswind component

is 18 kts

PPL FP & P

TAKE-OFF PERFORMANCE : FACTORS

So now you know what affects take-off performance, how do you apply this?

If you know the basic take-off distance for your aircraft you can

then apply some factors to get a more accurate figure.

Only use these factors if you do not have the aircraft actual figures

These are all included in the CAA Safety Sense

Leaflet “Aeroplane Performance” which you can

download from the CAA website

PPL FP & P


CONDITION

INCREASE

IN TOD TO

50FT

FACTOR

10% increase in weight 20% 1.2

1000ft increase in elevation 10% 1.1

10° increase in temperature 10% 1.1

Dry Grass (up to 20cm on firm soil) 20% 1.2

Wet grass (up to 20cm on firm soil) 30% 1.3

Tailwind of 10% of lift-off speed 20% 1.2

Soft Ground / Snow 25%+ 1.25+

Factors are multiplied…

PPL FP & P


Example:

Original take-off distance 600 metres

Taking off on Wet grass, aircraft is 10% heavier and temperature is 10° warmer

600 m x 1.3 (grass) x 1.1 (weight) x 1.1 (temperature)

= 943.8 metres

PPL FP & P

TAKE-OFF PERFORMANCE : SAFETY FACTORS

There is then an additional “Safety Factor” which you can apply

(it must be applied for public transport flights)

For take-off this factor is 1.33

In our example this means the total take-off distance

required to clear a 50 ft obstacle would be 1255 metres

(double the original distance)

PPL FP & P

TAKE-OFF PERFORMANCE : EXAMPLE 1 – TABLED DATA

Conditions

Any changes

that are required

PPL FP & P


Example – 500 ft airfield at 15°C

We need to interpolate to find the information we need

Never extrapolate outside a performance table

PPL FP & P


Grab your calculators and see what you get

725 1340

760 1407.5

795 1475

You may also want to apply a PSF to these figures

PPL FP & P


So can we take off at our airfield?

The AIP gives distances available:

Runway 06

TORA of 735m

TODA of 735m

Our example:

TORR of 760 ft

TODR of 1407 ft

Our example (metric):

TORR of 232m

TODR of 429m

We can take off!

PPL FP & P

TAKE-OFF PERFORMANCE : EXAMPLE 2 – GRAPHICAL DATA

Some aircraft have graphs instead of tables

PPL FP & P

TAKE-OFF PERFORMANCE

Why Bother?

Belgium 2008

Too much cargo, 5 crew, runway too short

Luckily no casualties

France 2010

2 people on board, alpine airfield

2 killed

PPL FP & P

PRACTICE QUESTION!

“What type of runway is performance data based upon?”

Hard, dry, level surface

PPL FP & P

PRACTICE QUESTION!

“What is the Public Transport Safety Factor to be applied for take-off?”

1.33

PPL FP & P

TAKE-OFF PERFORMANCE: PRESSURE ALTITUDE

Performance data is often tabulated against Pressure Altitude (PA)

This refers to the aerodrome elevation based on a standard pressure

setting of 1013mb

It is assumed that pressure drops by 1mb every 28 feet of altitude gain

If the aircraft is operating at a “higher” pressure altitude there is less oxygen for

the engine to burn and less air for the propeller to turn etc etc

You need to know how to work out a pressure altitude:

PPL FP & P

TAKE-OFF PERFORMANCE: PRESSURE ALTITUDE

Example – the pressure at and airfield (QFE) is 1009 mb

If you set your altimeter to

1013mb at this airfield, what

would it read?

1013mb – 1009mb = 4mb difference

4mb x 28 feet = 112 feet

The Pressure Altitude is 112 feet

The “original” elevation of the airfield is irrelevant

If you get a question about this on an exam paper you

can use 30 feet per mb

PPL FP & P

PRACTICE QUESTION!

“An airfield has an elevation of 520 feet above mean sea level. The QFE is

982mb, what is the approximate pressure altitude?”

1013mb – 982mb = 31mb

31mb x 28 feet = 868 feet

Pressure Altitude – 868 feet

PPL FP & P

LANDING PERFORMANCE : DEFINITIONS

50 ft

Landing distance available

(LDA)

Aircraft speed 1.3 x VS

Maximum

braking applied

Full flap,

no power

PPL FP & P

LANDING PERFORMANCE : DEFINITIONS

Measured Landing distance is the measured distance from a

point 50 feet above the runway to the point at which the aircraft

reaches a full stop

Assumes no power, full flap approach with a speed of 1.3 x

stalling speed at a simulated 50 ft marker point

Allows a 30% margin above the stall for safety

PPL FP & P

LANDING PERFORMANCE : FACTORS AFFECTING

WEIGHT

Increased weight INCREASES stall speed

Increased stall speed INCREASES approach speed

Increased approach speed INCREASES ground roll

Increased weight INCREASES kinetic energy so brakes have to absorb

more energy increasing ground run

50ft

PPL FP & P


DENSITY ALTITUDE

50ft

Increased density altitude INCREASES true airspeed (IAS remains same)

Touchdown speed is higher and so brakes have more kinetic energy to overcome

Higher Density

Altitude, longer

landing run

PPL FP & P


WIND

!

Still Wind

Head Wind

Tail Wind

Same IAS, different groundspeeds

PPL FP & P

RUNWAY SLOPE


Paved level surface

Upslope

Slope assists or retards deceleration

PPL FP & P


FLAP SETTING

Less

deceleration

required

Lower

approach

speed

Flap REDUCES stall speed and therefore approach speed

Lower approach speed reduces landing roll

PPL FP & P


RUNWAY SURFACE

Paved level surface

Wet long grass

Surface may retard deceleration and lengthen ground run

!

PPL FP & P

PRACTICE QUESTION!

“If the stalling speed of an aircraft in the landing configuration is 50 kts, what

will be the minimum approach speed?”

50 kts x 1.3 = 65 kts

PPL FP & P

PRACTICE QUESTION!

“If the aircraft is approaching an airfield with a tailwind, will the groundspeed

be higher or lower than the True Airspeed?”

Higher

PPL FP & P


AQUAPLANING

On a wet runway, the tyre may lose all contact with the surface

The tyre “floats” above the surface and so brakes become ineffective

It happens to cars as well as aircraft!

Usually occurs at the speed of:

9 x tyre pressure

PPL FP & P

LANDING PERFORMANCE : FACTORS

So now you know what affects landing performance, how do you apply this?

If you know the basic landing distance for your aircraft you can

then apply some factors to get a more accurate figure.

Only use these factors if you do not have the aircraft actual figures

These are all included in the CAA Safety Sense

Leaflet “Aeroplane Performance” which you can

download from the CAA website

PPL FP & P


Factors are multiplied…

CONDITION

INCREASE

IN LD FROM

50FT

FACTOR

10% increase in weight 10% 1.1

1000ft increase in elevation 5% 1.05

10° increase in temperature 5% 1.05

Dry Grass (up to 20cm on firm soil) 15% 1.15

Wet grass (up to 20cm on firm soil) 35% 1.35

Tailwind of 10% of lift-off speed 20% 1.2

Soft Ground / Snow 25%+ 1.25+

PPL FP & P


Example:

Original landing distance 600 metres

Landing on Wet grass, aircraft is 10% heavier and temperature is 10° warmer

600 m x 1.35 (grass) x 1.1 (weight) x 1.05 (temperature)

= 935.55 metres

PPL FP & P

LANDING PERFORMANCE : SAFETY FACTORS

There is then an additional “Safety Factor” which you can apply

(it must be applied for public transport flights)

For landing this factor is 1.43

In our example this means the total landing distance

required from 50 feet would be 1377.8 metres

(more than double the original distance)

NB. The factor is higher for landing because of the variation at

the “start point” of measuring the distance

PPL FP & P

LANDING PERFORMANCE : EXAMPLE 1 – TABLED DATA

Conditions

Any changes

that are required

PPL FP & P


Example: Airfield at 1400 feet pressure altitude,

temperature 22°C

We need to interpolate to find the information we need

Never extrapolate outside a performance table

PPL FP & P


Grab your calculators and see what you get

You may also want to apply a PSF to these figures

504 1246

511 1258

523 1276

PPL FP & P


So can we land at our airfield?

The AIP gives distances available:

Runway 06

LDA of 735m

Our example:

LDR of 1258 ft

Our example (metric):

LDR of 384m

We can take off!

PPL FP & P

LANDING PERFORMANCE : EXAMPLE 2 – GRAPHICAL DATA

Again, some aircraft have graphs instead of tables

PPL FP & P

PRACTICE QUESTION!

“Will a snow-covered runway increase or decrease a landing distance, and by

how much?”

Increase by 25% or more (Factor of 1.25 or more)

PPL FP & P

LANDING PERFORMANCE

Why bother?

Honduras

A320 over-ran runway on landing

Rochester

Cessna over-ran runway

and skidded into hedge

(pictured “parked up” after

accident)

http://www.airport-data.com/aircraft/photo/360479L.html

PPL FP & P

EN-ROUTE PERFORMANCE: BASICS

Drag

Airspeed

Total Drag

Parasite Drag

Induced Drag

Increases with

airspeed – more air

molecules striking

aircraft and being

slowed down by it

Decreases with

airspeed because the

wing is not working as

hard to produce lift

PPL FP & P

EN-ROUTE PERFORMANCE: BASICS

Drag

Airspeed

TOTAL DRAG has two maximums – one at

low speed and one at high speed

For straight and level flight the aircraft

must produce enough THRUST to balance

the DRAG

The POWER REQUIRED is high at low

speed and also at high speed

PPL FP & P

EN-ROUTE PERFORMANCE

Slow

flight

Fast

flight

The POWER REQUIRED

curve shows the extra need

for thrust at the two points

of maximum drag

The POWER AVAILABLE

curve shows the amount of

excess power available

(for acceleration or climb if

required)

PPL FP & P

EN-ROUTE PERFORMANCE: CLIMBING

Best RATE OF CLIMB = Best altitude gain for shortest time

Occurs where excess power is at its maximum

Best ANGLE OF CLIMB = Best altitude gain for shortest distance

Occurs usually 5-10kts below best rate of climb speed

Also known as VX

Also known as VY

PPL FP & P

EN-ROUTE PERFORMANCE

Climb Performance

Information can be

found in the aircraft

Pilot Operating

Handbook / Manual

PPL FP & P

ENDURANCE & RANGE: DEFINTITIONS

ENDURANCE refers to the amount of TIME that an aircraft can fly

RANGE refers to the maximum DISTANCE that an aircraft can fly

Range and Endurance are important but much more so in high-

performance aircraft where power setting, cruise altitudes and cruise

speeds have a more significant effect

PPL FP & P

EN-ROUTE: THE CLIMB

If being very accurate for time

and fuel calculations!

For example, for this aircraft for

a climb to 3000 feet it will take

3 minutes, 0.4 gallons of fuel

and 3nm at a 65 kt climb

PPL FP & P

ENDURANCE SPEED

Endurance Speed occurs

where aircraft is airborne

for longest time

Need to minimise fuel

burnt

Occurs at minimum power

required point of the

POWER REQUIRED

graph

Best

endurance

speed

Minimum

power

required

PPL FP & P

ENDURANCE SPEED

Detailed

information about

endurance speed

is in the aircraft

Pilot Operating

Handbook /

Manual

PPL FP & P

RANGE SPEED

Best range

speed

More

power

required

Range Speed occurs

where aircraft can travel

furthest distance

Occurs where power –

airspeed ratio is least

Rate of distance coverage

= speed

Rate of fuel burn =

power

At any other point on the

curve, the power/speed ratio

is higher

PPL FP & P

RANGE SPEED

Detailed

information about

range speed is in

the aircraft Pilot

Operating

Handbook /

Manual

PPL FP & P

SUMMARY OF RANGE / ENDURANCE

Best

RANGE

speed

Best

ENDURANCE

speed ?????

PPL FP & P

EN-ROUTE: THE CRUISE

All aircraft have a Cruise Performance

table in the Pilot Operating Handbook /

Manual

Different temperatures against

different pressure altitudes

The C152 POH shows percentage of

BHP, true airspeed and US gallons per

hour

PPL FP & P

PRACTICE QUESTION!

“Flying at the minimum drag speed will allow the aircraft to achieve maximum

.....?”

????

PPL FP & P

GLIDING

Weight

Relative Airflow

Lift

Drag

In a glide an aircraft produces no thrust

A component of weight balances the drag

Glidepath angle

PPL FP & P

GLIDING

The greater the drag, the steeper the glide angle

The shallowest glide is obtained when the drag is least – the best lift/drag ratio

LOW L/D RATIO

High Drag

Steep Angle Glide

Distance Poor

ie. L/D 3:1

HIGH L/D RATIO

Low Drag

Shallow Angle Glide

Distance Good

ie. L/D 6:1

PPL FP & P

GLIDING

Gliders are designed to:

Fly at a high L/D ratio

Glide for the maximum distance

Usually flown at best angle of attack (about 4°)

L/D ratio = 43:1

English Electric Lightning

L/D ratio = 14:1

PPL FP & P

GLIDING : FACTORS AFFECTING

WIND

Still Wind

Head Wind

Tail Wind

Same pitch attitude,

different flight paths

Glide distance is the

same relative to the

airmass but different

over the ground

PPL FP & P


AIRSPEED

Best L/D ratio speed

gives furthest glide

Too fast =

Smaller angle of attack =

L/D reduces and so Aircraft

“dives” towards ground

Too slow =

Larger angle of attack =

L/D reduces and so aircraft

“falls” toward ground

If gliding at recommended

speed and are

undershooting DO NOT

slow down!

PPL FP & P

FLAP SETTING


Generally – flaps lower the L/D ratio and reduce gliding distance

D

D

L L

W W

Clean Glide (no flap)

L/D ratio highest Glide with full flap

L/D ratio lowest

PPL FP & P

WEIGHT


Lighter aircraft has a slower speed for any

given angle of attack

L/D ratio usually at 4° angle of attack

Airspeed to maintain this angle will be

lower but glide angle the same

Rate of descent will be reduced

PPL FP & P


The best speed for gliding

for your aircraft will be found

in the Pilot Operating

Handbook / Manual

Usually based on max weight

– if big variation allowed,

different speeds will be shown

PPL FP & P

PRACTICE QUESTION!

“To obtain maximum glide range, a heavy aircraft will need to do what to equal

that of a light aircraft?”

Fly at a faster speed (to maintain the best angle of attack for gliding)

PPL FP & P

ADVERSE EFFECTS ON PERFORMANCE

FLAP

Initial settings increase lift-production

Later settings increase drag production

Alter stall speed - alter best approach speed

More power required to overcome extra drag

PPL FP & P

ADVERSE EFFECTS ON PERFORMANCE

ICE

Adds weight to aircraft

Decreases wings’ lift-producing capability

Drag increased

On propeller reduces thrust-producing capability

May reduce engine thrust-producing capability

AIRFRAME CONDITION

Dirty wing decreases wings’ lift-

producing capability

PPL FP & P

ADVERSE EFFECTS ON PERFORMANCE: CARB ICE

CARBURETTOR ICE can form

in temperatures up to +30˚C

As air passes through the

VENTURI, it is forced to speed

up and this causes the

temperature to decrease

If the air is moist then ICE will

form and may block airflow into

the engine

This causes ENGINE

ROUGH RUNNING and even

ENGINE STOPPAGE

PPL FP & P


This is more likely at LOW

POWER SETTINGS where

the gap between the

THROTTLE BUTTERFLY

and the outer wall of the

carburettor is smaller

Carburettor icing is ALWAYS

likely when the temperature

is below +30˚C and the

aircraft is within 200nm of

any sea surface

This must be probably on

about 99% of days in the UK!

PPL FP & P


PPL FP & P

PRACTICE QUESTION!

“When is carburettor ice most likely to occur?”

At low power settings (when the throttle butterfly is partially closed) with a

temperature below 30°C

PPL FP & P

Syllabus complete

Any Questions?

flight performance and planning for ppng member

Documents

balance mass

aircraft mass

descents ppl fp p mass

land ppl fp p mass

objects mass

fuel mass basic

ppl fp p fuel weight

ppl fp p lecture