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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
FORCES, MOMENTS & DATUMS: DEFINITIONS
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
FORCES, MOMENTS & DATUMS: DEFINITIONS
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
FORCES, MOMENTS & DATUMS: DEFINITIONS
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
Centre of Gravity (CG)
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
Centre of Gravity (CG)
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)
Take-off run available
(TORA) Stopway
1st
significant
obstruction
Accelerate-Stop Distance Available
(ASDA)
Take-off run available
(TORA) No
stopway
available
TAKE-OFF PERFORMANCE : DEFINITIONS
PPL FP & P
TAKE-OFF PERFORMANCE : DEFINITIONS
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
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
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
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
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
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
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
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
WIND
Still Wind
Head Wind
Tail Wind
PPL FP & P
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
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
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
RUNWAY SURFACE
Paved level surface
Wet long grass
Mud / Sand
Surface may retard acceleration and lengthen ground run
PPL FP & P
RUNWAY SLOPE
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
Paved level surface
Upslope
Slope assists or retards acceleration to VTOSS
PPL FP & P
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
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
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
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
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
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
TAKE-OFF PERFORMANCE : FACTORS AFFECTING
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
TAKE-OFF PERFORMANCE : FACTORS
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
TAKE-OFF PERFORMANCE : FACTORS
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
TAKE-OFF PERFORMANCE : EXAMPLE 1 – TABLED DATA
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
TAKE-OFF PERFORMANCE : EXAMPLE 1 – TABLED DATA
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
TAKE-OFF PERFORMANCE : EXAMPLE 1 – TABLED DATA
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
LANDING PERFORMANCE : FACTORS AFFECTING
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
LANDING PERFORMANCE : FACTORS AFFECTING
WIND
!
Still Wind
Head Wind
Tail Wind
Same IAS, different groundspeeds
PPL FP & P
RUNWAY SLOPE
LANDING PERFORMANCE : FACTORS AFFECTING
Paved level surface
Upslope
Slope assists or retards deceleration
PPL FP & P
LANDING PERFORMANCE : FACTORS AFFECTING
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
LANDING PERFORMANCE : FACTORS AFFECTING
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
LANDING PERFORMANCE : FACTORS AFFECTING
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
LANDING PERFORMANCE : FACTORS
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
LANDING PERFORMANCE : FACTORS
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
LANDING PERFORMANCE : EXAMPLE 1 – TABLED DATA
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
LANDING PERFORMANCE : EXAMPLE 1 – TABLED DATA
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
LANDING PERFORMANCE : EXAMPLE 1 – TABLED DATA
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)
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
GLIDING : FACTORS AFFECTING
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
GLIDING : FACTORS AFFECTING
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
GLIDING : FACTORS AFFECTING
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
GLIDING : FACTORS AFFECTING
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
ADVERSE EFFECTS ON PERFORMANCE: CARB ICE
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
ADVERSE EFFECTS ON PERFORMANCE: CARB ICE
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?