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Performance Chapter 11

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Aim To determine aeroplane performance using flight manual data

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**Objectives Define Performance State terms and definitions**

State factors affecting take-off and landing performance Calculate Pressure and Density altitudes Calculate take-off performance Calculate landing performance

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**Background Define the following Max take-off weight (MTOW) –**

Max landing weight (MLW) - Basic empty weight (BEW) - Centre of Gravity (CoG) - Maximum permitted take-off weight Maximum permitted landing weight Weight of aircraft without any payload, includes un-useable fuel and full oil Point where all the weight is said to act. Also the point about which the aircraft pivots

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**1. Define Performance Definition**

Understanding performance data allows us to make practical use of the airplane’s capabilities and limitations

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2. Terms and Definitions Take-Off Distance Required (TODR) - Distance required to take-off and reach a screen height (usually 50ft) above the runway at take-off safety speed Take-Off Run Required (TORR) - Actual Ground Run Required Take-Off Safety Speed (TOSS) - Speed which gives an adequate margin above the stall speed in the take-off configuration. Must not be less than 1.2Vs Screen Height TORR TODR

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2. Terms and Definitions Clearway – Defined area on the ground or over water that is free of obstacles, over which an aircraft may make its initial climb Take-Off Run Available (TORA) – Length of the runway available and suitable for the ground run of an aircraft taking off Take-Off Distance Available (TODA) – Length of take-off run available plus any clear way Screen Height Clearway TORA TODA

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2. Terms and Definitions Stopway – Defined area on the ground at the end of a runway suitable area in which an aircraft may stop in an emergency Accelerate Stop Distance Available (ASDA) – Distance specified as being the effective length available for use by an aircraft executing an aborted take-off, including any Stopway Stopway ASDA

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2. Terms and Definitions Landing Distance Required (LDR) - Distance required to land from a height of 50ft above the threshold to where the aircraft comes to a complete stop Landing Run Required (LRR) - Actual Ground Roll Required Landing Distance Available (LDA) – Length of runway suitable for the ground roll of an aircraft beginning at the threshold or displaced threshold 50’ LRR LDR LDA

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**3. Factors Affecting Perf.**

Take-Off The pilot in command of an aircraft must ensure the TODR does not exceed the TODA When calculating TODR the PIC must take into account: TORA Wind component Pressure Altitude Temperature Aircraft Weight Slope Surface

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**3. Factors Affecting Perf.**

Take-Off - Wind Nil Wind

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**3. Factors Affecting Perf.**

Take-Off - Wind Head Wind

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**3. Factors Affecting Perf.**

Take-Off - Wind Tail Wind

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**3. Factors Affecting Perf.**

Take-Off - Wind Head Wind Nil Wind Tail Wind

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**3. Factors Affecting Perf.**

Take-Off Factor Wind Altitude Temp. Weight Slope Flaps Surface Reason Affect on TODR H/W – T/W – Groundspeed changed Lower engine efficiency, greater TAS required Increase in temperature decreases air density giving a lower performance More inertia Need to accelerate uphill Some aircraft have take-off flap settings, allowing then to get airborne faster but reducing their overall climb performance Friction

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**3. Factors Affecting Perf.**

Landing The pilot in command of an aircraft must ensure the LDR does not exceed the LDA When calculating LDR the PIC must take into account: LDA Wind Elevation/Altitude Aircraft weight Slope Surface

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**3. Factors Affecting Perf.**

Landing - Wind Nil Wind

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**3. Factors Affecting Perf.**

Landing - Wind Head Wind

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**3. Factors Affecting Perf.**

Landing - Wind Tail Wind

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**3. Factors Affecting Perf.**

Landing - Wind Head Wind Nil Wind Tail Wind

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**3. Factors Affecting Perf.**

Landing Factor Wind Altitude Weight Slope Flaps Surface Reason Affect on LDR H/W – T/W – Groundspeed changed Greater TAS Increased momentum Upslope helps deceleration Lower approach speed, Increase in drag Bitumen increases braking efficiency

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**3. Factors Affecting Perf.**

CAO – Take-Off Subject to paragraph 6.3, the take-off distance required is the distance to accelerate from a standing start with all engines operating and to achieve take-off safety speed at a height of 50 feet above the take-off surface, multiplied by the following factors: (a) 1.15 for aeroplanes with maximum take-off weights of kg or less; (b) 1.25 for aeroplanes with maximum take-off weights of kg or greater; or (c) for aeroplanes with maximum take-off weights between kg and kg, a factor derived by linear interpolation between 1.15 and 1.25 according to the maximum take-off weight of the aeroplane.

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**3. Factors Affecting Perf.**

CAO Landing Subject to paragraphs 10.3 and 10.4, an aeroplane must not land unless the landing distance available is equal to or greater than the distance required to bring the aeroplane to a complete stop or, in the case of aeroplanes operated on water, to a speed of 3 knots, following an approach to land at a speed not less than 1.3VS maintained to within 50 feet of the landing surface. This distance is to be measured from the point where the aeroplane first reaches a height of 50 feet above the landing surface and must be multiplied by the following factors: (a) 1.15 for aeroplanes with maximum take-off weights of kg or less; (b) 1.43 for aeroplanes with maximum take-off weights of kg or greater; (c) for aeroplanes with maximum take-off weights between kg and 4500 kg, a factor derived by linear interpolation between 1.15 and 1.43 according to the maximum take-off weight of the aeroplane.

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**READ THE CONDITIONS ON THE CHART**

3. Factors Affecting Perf. CAO Some tables and charts will factor this in. READ THE CONDITIONS ON THE CHART

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**4. Pressure and Density Altitude**

International Standard Atmosphere (ISA) ISA provides a yardstick against which we can measure the effects of changing atmospheric conditions against performance figures produced by the aircraft manufacturer Standard ISA conditions at sea level are: QNH 1013 hPa Lapse rate of 1 hPa per 30ft Temperature 15⁰C Lapse rate of 2⁰C per 1000ft Density Kg/M3

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**4. Pressure and Density Altitude**

Pressure Altitude Pressure altitude is altitude corrected for pressure deviations from ISA If our QNH is greater than ISA our pressure altitude will be less than our actual altitude and the aircraft will perform better If our QNH is less than ISA our pressure altitude will be greater than our actual altitude and the aircraft will perform worse To calculate pressure altitude we must: Determine pressure variation from ISA Multiply variation by the pressure lapse rate, 30ft per 1 hPa Apply the variation to the aerodrome elevation If our QNH is greater than ISA our pressure altitude will be less than our actual altitude If our QNH is less than ISA our pressure altitude will be greater than our actual altitude

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**4. Pressure and Density Altitude**

Pressure Altitude For Example: Elevation is 650ft QNH is 1020 hPa Temperature is 30⁰C What is the pressure altitude? Determine pressure variation from ISA 1013 hPa – 1020 hPa = -7hPa Multiply variation by the pressure lapse rate, 30ft per 1 hPa -7 hPa x 30ft = -210ft Apply the variation to the aerodrome altitude Since QNH is greater than ISA, pressure altitude will be lower 650ft – 210ft = 440ft

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**4. Pressure and Density Altitude**

Density altitude is the altitude which has the same density as ISA standard If our density altitude is less than ISA the aircraft will perform better If our density altitude is greater than ISA the aircraft will perform worse To calculate density altitude we must: Determine pressure altitude Determine temperature variation from ISA at the pressure altitude Multiply variation by the lapse rate, 120ft per 1⁰C Apply the variation to the pressure altitude If our temperature is greater than ISA our density altitude will be greater than our actual altitude If our temperature is less than ISA our density altitude will be less than our actual altitude

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**4. Pressure and Density Altitude**

For Example: Pressure altitude is 4000ft QNH is 1020 hPa Temperature is 22⁰C What is the density altitude? Determine temperature variation from ISA at the pressure altitude 15 ⁰C - (2x4)= 7 ⁰C Multiply variation by the lapse rate, 120ft per 1⁰C 22⁰C - 7 ⁰C = 15 ⁰C x 120ft = 3300ft Apply the variation to the pressure altitude Because the temperature is greater than ISA our density altitude will be greater than our actual altitude 4000ft ft = 7300ft

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Cessna Chart For Example, calculate the Maximum Take-Off Weight for the following conditions: Pressure altitude 4000ft Temperature 25⁰C Take off Distance Available 800m Surface long dry grass No slope 15kt Headwind

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Cessna Chart Method: Enter the chart with 4000’ on the pressure altitude scale and plot a horizontal line to intersect 25⁰C From this point plot a vertical line to the TODA of 800m. Also from the intersection of the climb weight limit line draw a horizontal line to the right. This gives us the climb weight limit of 1060kg

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Cessna Chart Method: From the intersection of the TODA (800m) line plot a horizontal line to the reference line From the reference line follow the lines in the window to the “Long dry grass” line. Plot a horizontal line from here into the slope graph

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Cessna Chart Method: From the intersection of the horizontal line and the “Level” line plot a vertical line down into the wind graph to intersect 15kt headwind From this point plot a horizontal line to the Take Off Weight scale. This gives us the runway performance weight limit of 1000kg

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Cessna Chart Method: The Maximum Take Off Weight is the lesser of the climb weight limit (1060kg) and the runway performance limit (1000kg)

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Piper Chart For Example, calculate the Take-Off Distance Required for the following conditions: Pressure altitude 2000ft Temperature 20⁰C Surface Long dry grass 2% Down slope 5kt Headwind Take-Off Weight 1000kg

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Piper Chart Method: Enter the chart with 25⁰C on the Temperature scale and plot a vertical line up to the Pressure altitude of 2000’. Also check the climb weight limit From this point plot a horizontal line to the surface reference line. Follow the guide lines to the long dry grass line then proceed horizontally to the slope reference line

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Piper Chart Method: Follow the guide lines to the 2% down slope line then proceed horizontally to the wind reference line Follow the guide lines to the 5kt headwind line then proceed horizontally to the take off weight of 1000kg

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Piper Chart Method: Follow the guide lines to determine the Take-Off Distance Required 750m

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**5. Calculate Landing Perf.**

Landing Performance – Typical Cessna Chart For Example, calculate the Landing Distance Required and Maximum Landing Weight for the following conditions: Pressure altitude 7000ft Temperature 15⁰C No slope 10kt Headwind

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**5. Calculate Landing Perf.**

Landing Performance – Typical Cessna Chart Method: Enter the chart with 7000’ on the pressure altitude scale and plot a horizontal line to intersect 15⁰C From this point plot a vertical line into the Landing Distance Required Window

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**5. Calculate Landing Perf.**

Landing Performance – Typical Cessna Chart Method: Enter the chart again from the wind component of 10kts and plot a vertical line up to the slope, in this case level From this point plot a horizontal line to intersect the vertical line already in the Landing Distance Required window

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**5. Calculate Landing Perf.**

Landing Performance – Typical Cessna Chart Method: Follow the guide lines to the left to determine the Landing Distance Required 550m We also need to check the climb weight limit – in case of a Go-Around – In the climb weight limit window plot a horizontal line from pressure height to the reference line then straight down to read the climb weight limit of 910kg

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**5. Calculate Take-Off Perf.**

Landing Performance – Typical Piper Chart For Example, calculate the Landing Distance Required for the following conditions: Pressure altitude 4000ft Temperature 30⁰C 2% Down slope 10kt Headwind

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**5. Calculate Take-Off Perf.**

Landing Performance – Typical Piper Chart For Example, calculate the Landing Distance Required for the following conditions: Pressure altitude 4000ft Temperature 30⁰C 2% Down slope 10kt Headwind

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Piper Chart Method: Enter the chart with 30⁰C on the Temperature scale and plot a vertical line up to the Pressure altitude of 4000’. Also check the climb weight limit From this point plot a horizontal line to the slope reference line. Follow the guide lines to the 2% down slope line then horizontally across to the wind reference line No climb weight limit with a pressure alt. of 4000’

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**5. Calculate Take-Off Perf.**

Take Off Performance – Typical Piper Chart Method: Follow the guide lines to the 10kt headwind line then proceeded horizontally to read the Landing Distance Required of 690m No climb weight limit with a pressure alt. of 4000’

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