Takeoff and Landing Performance

A significant number of accidents and incidents occur during takeoff and landing. Ensuring that your takeoff and landing can be conducted within the confines of the runway will significantly contribute to the safety of these critical phases of flight.

Every effort is made to ensure that the information in this booklet is accurate and up to date at the time of publishing, but numerous changes can occur with time, especially in regard to airspace and legislation. Readers are reminded to obtain appropriate up-to-date information.

Contents PIC Responsibilities................5 How to Comply............................ 5

Performance Factors..............6 Weight......................................... 6 Air Density................................... 6 Wind.......................................... 10 Slope.......................................... 12 Surface...................................... 12 Obstacle Clearance.................... 14 Flap Setting................................ 14 Ground Effect............................ 15 Tyre Pressure............................. 16 Wing Surface............................. 16

Other Considerations...........17 Runway Distance....................... 17 Pilot Technique.......................... 17 Speed Control............................ 18 Decision Points.......................... 18 Contingencies............................ 19

Determining Performance....20 Group Rating System................ 20 P-Charts..................................... 22 Aircraft Flight Manual................ 30 Air Transport Operations............ 32 Know Your Aircraft..................... 33

Conclusion.............................34 Performance Questions............. 35

CAA Web Site

Every effort is made to ensure that the information in this booklet is accurate and up-to-date at the time of printing, butweb numerous can occur with time, especially in regard to legislation. See the CAA site forchanges Civil Aviation Rules, Advisory Circulars, Readers are reminded to obtain appropriate information. Airworthiness Directives, forms, and moreup-to-date safety publications.

4

PIC Responsibilities Civil Aviation Rules clearly indicate that it is the responsibility of the pilot in command to ensure that they operate their aircraft in a safe manner with respect to takeoff and landing performance. In particular, rule 91.201(2) states that “A pilot-in-command of an aircraft must … during the flight, ensure the safe operation of the aircraft and the safety of its occupants…”.

How to Comply

If you are operating under Part 135, there

If you are operating under Part 91,

will be specific performance requirements you will need to meet – these are briefly

Advisory Circular 91-3 Aeroplane Performance Under Part 91 provides

discussed later in this booklet.

guidance on how best to comply with

Note that the group rating system,

rule 91.201(2). Essentially, AC91-3 says

for instance, is quite conservative and

that you can determine the takeoff and

sometimes shows that an aircraft will

landing performance of your aircraft by

not fit on to a particular runway when

one of the following three methods:

in fact P-chart calculations (which are

•

Group Rating system;

more precise) show otherwise. It is

•

P-charts; or

•

Approved Aircraft Flight Manual data.

quite acceptable to select the method that shows that the operation can be performed within the aircraft’s

AC 91-3 also provides performance

performance limits.

correction tables for surface type, slope,

All of these three methods are

and contaminated runway surfaces,

discussed, with worked examples,

since this information is often omitted

later in this booklet.

from many light aircraft Flight Manuals.

5

Performance Factors Many different factors affect aircraft performance. Weight

Effect of Pressure on Density

The gross weight of the aircraft directly

Atmospheric pressure decreases with

affects stall speed, a 10 percent increase

altitude, because the air near the earth’s

in weight increasing the stall speed by

surface is compressed by the air above it.

5 percent.

As altitude increases, air is free to expand and therefore becomes less dense.

Takeoff Liftoff speed is generally about 15 percent

Effect of Temperature on Density

above the stalling speed, so an increase in

Temperature generally also decreases with

weight will mean a higher liftoff speed.

altitude. This causes the air to contract

In addition to the higher speed required,

and become denser. However, the drop

acceleration of the heavier aeroplane is

in pressure as altitude is increased has

slower. Hence, a longer takeoff distance

the dominating effect on density when

will be required. As a general rule of thumb,

compared with the effect of temperature.

a 10 percent increase in takeoff weight has

Effect of Humidity on Density

the effect of increasing the takeoff run by

Water vapour is lighter than air; consequently

about 20 percent.

moist air is lighter than dry air. It is lightest

Landing

(or least dense) when, in a given set of

Heavier landing weights require higher

conditions, it contains the maximum amount

approach speeds, which means the aircraft

of water vapour.

will have greater momentum and require

International Standard Atmosphere

more runway in which to land and stop.

A standard atmosphere has been

A 10 percent increase in landing weight has

established to enable comparison of aircraft

the effect of increasing the landing distance

performances, calibration of altimeters and

by about 10 percent.

other practical uses.

Air Density

In the International Standard Atmosphere

As air density decreases, both engine and

a particular pressure and temperature

aerodynamic performance decrease.

distribution with height is assumed.

6

At sea level the pressure is taken to be 1013.2 hPa and the temperature 15˚C. In this ‘average’ atmosphere, any pressure

Height above Sea Level (Thousands of feet)

Temp (˚C)

Press. (hPa)

Relative Density

40

-56

188

0.247

level has a standard corresponding altitude

Cirrus clouds

called the pressure altitude (based on a lapse rate of approximately one hPa per

35

-54

239

0.311

30

-44

301

0.375

30 feet at lower levels) and a corresponding temperature called the ISA temperature. Pressure altitude is the height that will register on a sensitive altimeter whenever

Mt Everest

its sub-scale is set to 1013.2 hPa. In the standard atmosphere, temperature

25

-34

377

0.449

20

-25

466

0.533

falls off with height at a rate of 1.98˚C per 1000 feet up to 36,090 feet, above which it is assumed to be constant (see Figure 1). Warm air is less dense than cold air.

High Cumulus clouds

Thus, when the temperature at any

15

altitude in the atmosphere is higher than

-15

572

the temperature would be in the standard

0.629 Mt Cook

atmosphere at the same altitude, then the air at that altitude will be less dense than

10

-5

697

0.739

5

+5

843

0.862

in the standard atmosphere. ISA also assumes dry air. In normal conditions, the amount of water vapour

Stratus and Nimbus clouds

in the air does not make a significant difference to its density. However, as warm

0

air can contain much more water vapour than cold air, at high temperatures and

+15

1013 Sea level

1.000

high humidity, the reduction in density may become significant and degrade aircraft

Figure 1

takeoff performance accordingly.

The International Standard Atmosphere

7

Density Altitude

Density altitude can be calculated by taking

Density altitude represents the combined

pressure altitude and adding (or subtracting)

effect of pressure altitude and temperature.

120 feet for each 1˚C above (or below) ISA.

It is defined as the height in the standard

When an aircraft is taking off at a density

atmosphere, which has a density corre-

altitude above ISA sea level, it will still get

sponding to the density at the particular

airborne at the same indicated airspeed

location (on the ground or in the air) at which

as at sea level, but because of the lower

the density altitude is being measured.

density the true airspeed (TAS) will be

Aircraft performance depends on air density,

greater. To achieve this higher speed with the same engine power, a longer takeoff run

which directly affects lift and drag, engine power, and propeller efficiency. As air

will be needed.

density decreases, aircraft performance

The effect of a high-density altitude on the

decreases. Density altitude, therefore,

power developed from the unsupercharged

provides a basis for relating air density to

engine is adverse, and less power will be

ISA, so that aircraft performance can be

available for takeoff. (When taking off from a

readily determined.

high-density altitude aerodrome, the engine

8

• The takeoff distance is increased by

will not even develop the power it is capable

one percent for every 1˚C above the

of unless the mixture is correctly leaned.)

standard temperature for the aerodrome

An increase in density altitude, therefore,

elevation.

has a two-fold effect on the takeoff:

• Rate-of-climb and angle-of-climb are

• An increased takeoff speed (TAS) is

noticeably reduced, as is obstacle

required.

clearance after takeoff.

• Engine power and propeller efficiency

High-density altitudes are found most

are reduced.

commonly at high-elevation aerodromes

• The approximate effect of these two

when the temperature is high.

components on takeoff and landing

Low atmospheric pressures will accentuate

performance are:

the effect. Taking off with a heavy aeroplane

• The takeoff distance is increased by one

in these conditions is fraught with danger.

percent for every 100 feet of aerodrome

Your takeoff performance sums have got to

pressure altitude above sea level, and

be right.

the landing distance by one percent for every 400 feet.

9

Glentanner aerodrome has an elevation of 1824 feet AMSL.

Wind

Landing distances are similarly increased. Tailwind takeoffs and landings should be

Headwind

avoided unless it can be established with

Taking off into wind results in the shortest

absolute certainty that there is sufficient

takeoff run and the lowest groundspeed

distance available to do so.

on liftoff. If it becomes necessary to abandon the takeoff, not only will the lower

Crosswind

groundspeed make it easier to stop, but also

A crosswind situation will affect takeoff

the shorter takeoff run means more runway

and landing performance, mainly because

available to do so. Climbing into wind

of the reduced headwind component.

gives a lower groundspeed and therefore a

If the wind is 30 degrees off the runway

steeper angle of climb after takeoff; this is

heading, the headwind is effectively

good for obstacle clearance.

reduced by 15 percent. If the wind is

Landing into wind results in a lower

45 degrees off, the headwind is reduced

groundspeed and shorter landing run.

by 30 percent.

Takeoff and landing distances are reduced by about 1.50 percent for each knot of

Gusting Winds

headwind up to 20 knots.

A gusting wind situation will require that you keep the aeroplane on the ground for

Tailwind

a slightly longer period of time to provide

Taking off downwind results in a much

a better margin above the stall, thereby

longer distance to get airborne and a

increasing your overall takeoff roll.

decreased angle of climb, which is bad for

Gusty conditions also necessitate a higher

obstacle clearance.

approach speed, which results in a longer

For a 5-knot tailwind component, the takeoff

landing roll.

distance should be multiplied by 1.25 and for ten knots by 1.55.

10

Turbulence and Windshear The possibility of turbulence and windshear should be considered when working out takeoff or landing distances. Windshear is a change in wind velocity (speed and/or direction) over a very short distance. The presence of windshear can cause sudden fluctuations in airspeed after takeoff or during an approach. Hangars, buildings and areas of trees all influence the flow of the wind near them. The mechanical turbulence resulting from this disturbed airflow may become very marked in the lee of the obstruction. In winds below 15 knots, turbulence occurs in the lee of the obstruction and may extend vertically to about one third higher again than the obstruction. In winds above 20 knots, eddies can occur on the leeward side to a distance of about 10 to 15 times the obstruction height and up to twice the obstruction height above the ground.

11

Slope

15 metres (50 feet) height difference on a 750-metre strip gives an answer of 0.02,

An uphill slope increases the takeoff ground

or a 2 percent slope.

run, and a downhill slope increases the landing ground run. For example, an upslope

Surface

of 2 percent increases takeoff distance by about 15 percent and a 2 percent downslope

Takeoff

decreases it by about 10 percent.

Grass, soft ground or snow increase the

Slopes can be calculated from known or

rolling resistance and therefore the takeoff

estimated information. Divide the difference

ground run will be longer than on a sealed

in height between the two strip ends by

or paved runway.

the strip length (working in the same

Dry grass can increase takeoff distance

units of measurement). For example,

by up to 15 percent. Long wet grass can

12

further increase this distance depending

Landing

on the length and wetness of the grass and

On landing, grass or snow cause an

the weight and wheel size of the aircraft.

increased ground roll, despite increased

Aircraft type is a big factor here – attempting

rolling resistance, because the brakes are

to takeoff on such a surface in a Piper Cub is

less effective.

an entirely different proposition to a Cessna

Long wet grass can mean a very large

172 for example.

increase in the landing run due to this effect.

It is often inadvisable to takeoff in long wet grass, and it can be impossible. Puddles of water on the runway can also significantly retard acceleration.

13

Obstacle Clearance

by the number of nautical miles covered

Plan to clear obstacles on the climbout path

per minute eg, 500 fpm/1.1 NM per min = 454 feet per NM of climb performance

by at least 50 feet.

(this assumes a groundspeed of 66 knots).

Consider what your aircraft’s climb gradient is likely to be as part of your takeoff

This will then give you a good indication of

performance calculations – especially

whether you will be able to maintain safe

if terrain, wires, and the possibility of

terrain and obstacle clearance.

Photo courtesy of Kaye Nairn

downdraughts are factors in the climbout path. Calculating the gain-of-height per

Flap Setting

mile is straightforward. Simply divide the

Flap reduces the stalling speed and enables

aircraft’s known rate-of-climb performance

you to lift off at a lower indicated airspeed.

14

wing out of ground effect. Thus the wing

This can mean a shorter ground run, but

is more efficient while in ground effect.

it may not give any reduction in takeoff distance to 50 feet because flap usually

While this can be useful on occasions, it can

causes a reduction in the rate of climb.

also trap the unwary into expecting greater climb performance than the aeroplane is

The recommended flap setting should

capable of sustaining.

always be used.

On landing, ground effect may produce

Ground Effect

‘floating’ and result in a go-around (or an

When flying close to the ground, the wing

overrun, if the danger signs are ignored)

generates less induced drag than around a

particularly at very fast approach speeds.

15

Low-wing aeroplanes are more sensitive

satisfactory obstacle clearance as result,

to ground effect than high-wing ones.

which is all the more reason for making

Ground effect makes it possible to lift off

sure that you get it right first time.

at too high a pitch angle, or too soon with

Tyre Pressure

a heavy load. Taking off too steeply (or too

Low tyre pressure (perhaps hidden by grass

soon) will cause the angle of attack to be

or spats) will increase the takeoff run.

at or near that of a stall, with drag and thrust nearly equal, and thus no chance

This is something that should always be

of accelerating.

checked during the pre-flight walk around.

Don’t force your aircraft to become

Wing Surface

airborne too soon.

Deposits on the wing surface, such as

Let it lift off when it’s ready to fly. Utilise

raindrops or insects, can have a significant

ground effect by briefly holding the aircraft

effect on laminar flow aerofoils such

in ground effect to let it accelerate to best

as used on some self-launching motor

angle-of-climb speed before climbing out.

gliders and high performance home-built

This is especially important when departing

aeroplanes. Stall speeds are increased and

from a short soft field with obstacles.

greater distances are required.

If you inadvertently leave ground effect

The presence of surface frost, ice or snow

too soon, and the aeroplane is not able

affects any aerofoil, including the propeller.

to accelerate to its proper climb speed,

Minor hangar rash or dents on the lifting

the only way to retrieve the situation is

surfaces or propeller will also degrade

to lower the nose, allow the aircraft to

performance. Keep all lifting surfaces

accelerate, and then climb. The problem

damage-free and clean to ensure maximum

is, that you may not be able to achieve

performance.

16

Other Considerations It is good airmanship to think about what technique, speed, and decision point, you will use for every takeoff and landing. Runway Distance

Pilot Technique

Information on available runway distances is

Ensure that recommended short-field

published in the AIP New Zealand AD section.

takeoff and landing techniques are always

At non-published airstrips distances should be paced out. Pace length should be established

used when operating out of airstrips where the distance available is a factor. Consult the Flight Manual, or an instructor,

accurately – or deliberately underestimated.

if you are unsure as to what technique

If you expect to use a strip frequently, you

should be used for a particular aircraft.

should ensure that the length is measured

Consider undertaking some dual short-field

accurately (for example, by using a rope of

takeoff and landing revision.

known length).

17

Speed Control

Decision Points

The speed at which you lift off is very

You should always nominate a decision

important with regard to achieving the

point where you will abandon the takeoff

best takeoff performance from the aircraft

or discontinue the approach if things are

– particularly when runway length is a

not going as expected.

significant factor. Likewise, letting the

For takeoff, this is the point at which there

aircraft accelerate in ground effect to best

is sufficient distance available to safely

angle-of-climb speed is also critical.

stop the aircraft should it accelerate slower

For landing, correct speeds for the prevailing

than expected or suffer a power loss.

conditions are obviously important.

This is particularly important for multiengine aircraft.

Photo courtesy of Kaye Nairn

Arrive too fast and you will use up more runway, too slow on approach and you may

For landing, the decision point should be

stall and not arrive on the runway at all.

a height where there is sufficient room to

18

effect a safe go-around if you are not happy

Contingencies

with the approach. An important factor

Even after having worked out your aircraft’s

here, and one that is often overlooked by

takeoff or landing performance, it is prudent

pilots, is the assessment of groundspeed

to add a contingency to allow for other

while on approach. A check of the windsock

factors that you may have overlooked.

and an estimate of whether your ground-

For instance, the engine may not be

speed is about what you would expect for

performing as well as it used to, the brakes

your airspeed when on short final is good

may be dragging slightly, the propeller may

practice. Any tailwind component very

be less efficient than it used to be, you might

significantly increases the landing distance,

encounter a lull or shift in the wind, etc.

so a go-around is usually the best course

Where takeoff and landing distances are

of action should this be the case.

looking marginal, we suggest that you always factor a contingency of at least 10 percent into your calculations.

19

Determining Performance The following section gives three ways of ensuring adequate takeoff and landing performance for private operations.

Group Rating System

The Group Rating system allows for runway length, slope and surface, with a generous

What Is It?

allowance for ambient conditions, and it

Every light aircraft in New Zealand has been

assumes that the operation is conducted

(and still is) assigned a group rating number

into wind using recommended short-field

from 1 to 8 – based on its takeoff and

techniques. The system can’t take into

landing performance at maximum weight

account specific conditions on the day,

(1 = excellent performance and 8 = poor

so the aircraft Group Rating number

performance). Runways that are published

allocated is conservative for private

in the AIP New Zealand AD section are

operations. However, if ambient conditions

also assigned a group rating number based

differ significantly from ISA in a way that

on their characteristics (1 = short distance

will reduce performance, and the airstrip is

available and 8 = long distance available).

sloping, it would be wise to use a P-chart

20

AIP New Zealand

NZGS AD 2 - 52.1

GISBORNE

Certificated Aerodrome 1NM W of Gisborne

Not for operational use

NZGS

OPERATIONAL DATA (1)

RWY RWY

SFC

Strength

Gp

Slope

ASDA

14 32

1310

B

PCN 20 F/B/Y/T

8

0.07U 0.07D

14 14

B

PCN 20 F/B/Y/T

7 6

0.07U

32 32

0.07D

Take-off distance 1:20

1:25

1:30

1:40

1:50 1371

777

EXTENSION CLOSED

LDG 1:62.5 DIST 1371 1270

1310 868

B

PCN 20 F/B/Y/T

6 7

14 14

Gr

ESWL 1600

4 6

0.08U

32 32

Gr

ESWL 1600

6 4

0.08D

03 21

Gr

ESWL 5700

8

0.05U 0.05D

1042 1170

1170 1042

09 27

Gr

ESWL 9080

8

0.1U 0.1D

1039 1173

1173 1039

868

EXTENSION CLOSED

551 750

777

750 551

MINIMA Figure 2 IFR Take-off RWY

Day

Night

14/32

300–1500

300–1500

03/21 600–1500 600 1500 or the Flight Manual to determine takeoff 09/27

NA runways with a group rating of 6 or from

and landing distances.

greater. If the runway group rating is less

The group number of your aircraft can be

than 6 it may still be safe to operate under

found in the front of its Flight Manual.

favourable conditions, but you would need

The runway group rating number can

to work out the distances required for the

be found in the table at the top of each

prevailing conditions using one of the other

aerodrome operational data page in the

two methods.

AIP New Zealand AD section.

Note that some runways may in fact have

(continued)

more than one group number assigned to

How Does It Work?

them because of differences in the available

Using the group rating system is very

takeoff and landing distance, for example

simple. For example, if your aircraft has

Gisborne (see Figure 2).

a group rating of 6, it is safe to operate Effective: 24 SEP 09

GISBORNE

21

E Civil Aviation Authority

OPERATIONAL DATA (1)

P-Charts

What Are They?

Use of a Performance chart (P-chart) is

P-charts are graphs developed from

another acceptable method (which is more

manufacturer’s test data. They apply various

precise than the group rating system)

factors, including density altitude, type of

for determining takeoff and landing

operation, runway surface, runway slope

performance.

and wind to readily determine takeoff and landing distances for a particular set

Photo courtesy of Jack Stanton

of conditions.

22

The CAA no longer (as of 1 April 1997)

P-chart, it is important to know how to use it

includes a P-chart when it issues a

and to understand what is being allowed for.

Flight Manual for an aircraft. But for the majority of light aircraft in New Zealand

Examples

the P-chart remains a very practical

The following example gives guidance on

method of determining takeoff and landing

how to best use a P-chart. (Note that at the

performance and can be completed with

bottom of the P-chart there is a tracking

ease. If your aircraft Flight Manual has a

depiction on how to work from box to box.)

23

Takeoff Distance Example

Determining Density Altitude

The red line in Figure 3 relates to the data

The first thing we need to do is to calculate

supplied below and the blue line provides

the airstrip’s density altitude.

a comparison for ‘standard’ conditions.

To do this we must determine the pressure

Note that all takeoff distances are to a

altitude of the airstrip and then correct

height of 50 feet, at which point a speed of

it for temperature by using the ambient

1.2 Vs (where Vs is the stall speed for the

temperature of the day (26˚C in this case).

chosen configuration) is assumed to have

This is an area that many pilots seem to

been achieved. Landing distances are also

have difficulty with.

all from a height of 50 feet with a speed of

The easiest way to determine pressure

1.3 Vs when passing through that height.

altitude, if we are sitting in our aircraft,

The distances given for private operations

is to set the sub-scale on the altimeter to

represent the minimum distance acceptable,

1013.2 hPa. The altimeter will then read

and pilots should carefully review all factors

the pressure altitude of the aerodrome.

(and other options) before landing at or taking off from an aerodrome with only the

Alternatively, knowing that 1013.2 hPa is

bare minimum distance available.

ISA pressure at sea level, we calculate the difference from today’s QNH (sea level

Type of Operation – Private

pressure), which is 997 hPa. This is 16 hPa

Aircraft – Cessna 172P

below 1013.2 hPa, and as each hectopascal

Max all up weight – 1089 kg

equals approximately 30 feet, this equates to 480 feet. We must now apply this

QNH – 997 hPa

correcting figure to our aerodrome elevation

Temperature – 26˚C

of 1320 feet. Do we add it or subtract it?

Wind – 050˚M/15 knots

Because the pressure today is lower than

Aerodrome elevation – 1320 feet amsl

standard (pressure decreases with altitude, 997 hPa being found at 480 feet amsl

Runway – 020˚M

on a standard day) we add the figure to

Surface – grass

aerodrome elevation, arriving at a pressure

Length – 730 metres

altitude of 1800 feet.

Slope – 1% up

24

25

Figure 3

0

1000

2000

3000

4000

DENSITY ALTITUDE

Density Altitude Graph

Surface

Now we start at the box for determining

From this point we track vertically up

density altitude which can be found at the

into the next box, until we meet the line

bottom left of the chart. We enter the graph

“Private – Grass – Day”.

at the top with the ambient temperature of 26˚C, and track vertically down that line

Slope

until we meet the imaginary angled pressure

We then move horizontally to the next

altitude line for 1800 feet (ie, a point just

box going through to the zero line. (This is

under the angled 2000-foot line).

most important – always go to the zero line in the last two boxes.) We then track

(For our exercise, we don’t need to worry

parallel to the curved lines until we reach

about the angled temperature lines marked

the 1 percent up line.

“ISA+10” etc, which depict the ISA drop-off in temperature with altitude.)

Wind

From that point we exit the box horizontally

The headwind component must now

to the right. A scale is not usually marked

be determined because the wind is not

on the righthand side of the box, but we

straight down the runway. The crosswind

have shown the density altitude figures in

component graph in the Flight Manual can

colour on our example to give you a better

be used to calculate this (see figure 4).

appreciation of what you are working out.

The headwind component in this case is

(You will note that, although the aerodrome

13 knots.

elevation in our example is only 1320 feet,

Now we move horizontally to the zero

the density altitude under the prevailing

line of the wind box. Using the headwind

conditions is 3500 feet – quite a significant

component of 13 knots track parallel to

difference.)

the curved line until we reach the 13-knot headwind line. From this point, we exit

Weight

horizontally to the right of the box, where

Continue horizontally into the next box until

we can read off the distance required

we meet the weight line of 1089 kilograms

for takeoff.

(ie, the maximum). You will notice that the only variable on the chart that the pilot has

In this example nearly 700 metres is

any control over is the weight of the aircraft.

required to reach a height of 50 feet.

Bearing this in mind, the graphs can be

As the runway in this example is 730 metres

used to work out a safe operating weight

long, we should be able to take off safely

on marginal runways.

(but remember this is for short dry grass).

26

Figure 4 Wind Components

EXAMPLE:

FLIGHT PATH 60

0˚

10˚

Wind Speed Angle between wind direction and flight path

10 Knots

Headwind component Crosswind component

9.5 Knots 3.5 Knots

20˚

20˚ 50

IN W

30˚

D

AT FL IG HT P

50˚

N

AN D

50

S OT KN

H

60

–

60˚

40

W EE

N

W

IN

D

DI

RE

CT

IO

30

30

70˚

GL

EB

ET

20 AN

HEADWIND COMPONENT – KNOTS

D EE

40

SP

40˚

20

10

80˚ 10

0

90˚

-10

-20

100˚

180˚ 170˚ 160˚ 150˚ 140˚ 0

10

130˚

120˚

20 30 40 CROSSWIND COMPONENT – KNOTS

27

110˚ 50

60

Landing Distance Example

as engine performance is not a critical factor

Now work through the landing example

(unless a go-around becomes necessary). At very high density altitudes, however,

provided (see Figure 5) using the same

the resulting higher true airspeed (TAS)

aircraft, aerodrome and weather conditions

should be borne in mind in relation to the

as above by following the red line.

approach and landing, as should the reduced

Note that aerodrome elevation is used rather

power available for a go-around.

than density altitude in this calculation,

You will also note that the slope corrections are reversed from the takeoff situation; an uphill slope on landing will decrease the landing distance and vice versa.

28

29

Figure 5

Aircraft Flight Manual

allowed for manually and added to the

Takeoff and landing performance graphs/

basic takeoff or landing distance as a

tables in aircraft Flight Manuals vary from

percentage value.

manufacturer to manufacturer.

AC91-3 suggests that takeoff and landing

Usually they do not allow for as many

distances derived from the aircraft flight

variables as P-charts.

manual should be corrected for variation in runway surface and slope by applying

Each graph or table will normally be

the factors in Figures 6 and 7.

formulated for standard conditions (ie a level, dry, paved surface in nil wind

If your aircraft Flight Manual has a

with the aircraft configured for a short-

P-chart, we suggest that, in most cases,

field takeoff or landing) and allows for

it is preferable that you use it over other

variations in weight, pressure altitude,

Flight Manual data – particularly if it is an

and temperature only. For tables, these

old Flight Manual, some of which tend to

variables are usually given over rather

be less comprehensive than their modern

a broad range, eg temperature in bands

counterparts. Some manufactures’ Flight

of 10˚C and pressure altitude in bands

Manual data can also, at times, tend to be

of 1000 feet. Other variables, such as

optimistic rather than conservative about

wind and type of surface, have to be

their aircraft’s performance.

30

AC91-3

AC91-3

ensures that you the capability Aircraft flight manual thishave ensures that you 4. Aircraftdata flight manualthis data clear any obstacles close theobstacles runway end cleartoany cl 4.1 For calculating aircraft performance, 4.1 For calculating aircraft performance, the aircraft manufacturer has supplied 4.3 In addition you should correct the the aircraft manufacturer has supplied 4.3 In addition yota performance data performance in the aircraft data flightinmanual. off distance from airc the aircraft flight manual.to 50 feet offderived distance to the 50 feet This data allows you to calculate the take-off manual for– This data allows you to calculate flight the take-off flight manual for– and landing distances with a correction for and landing distances with a correction for (a) other than a paved runway surface density altitude at various weights and for the (a) other than a p density altitude at various weights and forapplying the the factors in Table 1; and surface wind. The manufacturer does not applying the f surface wind. the Theeffect manufacturer does not provide you with data to calculate of provide you runway with data to calculate the (b) effect of slope by applying the factor runway runway slope or the different surface (b) runway slope runway slope or the different runway surface Table 2 up to a maximum of 3% slo types. Table 2 up to types. 4.2 You should use the flight manual data 4.2 You should to determine the take-off distance to 50use feet the as flight manual data determine the take-off distance to 50 feet as Table 1. Runwayto surface factors Table 1. Runway surface factors SURFACE TAKE-OFF LANDING SURFACE TAKE-OFF FACTOR LANDING TYPE DISTANCE FACTOR DISTANCE TYPE DISTANCE FACTOR DISTANCE FACTOR x 1.00 x 1.00 Paved x 1.00 x 1.00 Paved Figure 6 x 1.00 x 1.05 Coral Runway surface x 1.00 x 1.05 Coral x 1.05 x 1.08 Metal factors x 1.05 x 1.08 Metal x 1.16 Rolled earth x 1.08

4.

Grass

Rolled earth x 1.14 Grass

x 1.08 x 1.18

x 1.16

x 1.14

x 1.18

Table 2. Runway slope factors DIRECTION OF SLOPE

Figure 7 Runway slope factors

Uphill

Table 2. Runway slope factors % OF SLOPE TAKE-OFF DISTANCE DIRECTION OF %CORRECTION OF SLOPE SLOPE 1 +5% 1 +10%

+5% -10%

-5%

2 +15%

+10%-15%

-10%

1

-5% 3

+15%+5%

-15%

2

-10% 1

-5% +10%

+5%

3 Downhill

-15% 2

-10% +15%

+10%

-15%

+15%

2 3

Downhill

LANDING DISTANCE CORRECTION LANDING DIS TAKE-OFF CORRECT DISTANCE CORRECTION -5%

Uphill

3

For slopes expressed to a decimal point, the correction is 0.5% distance for each 0.1% slope. For example, f runway slope of 1.6% the correction factor is 8%.

31

For slopes expressed to a decimal point, the correction is 0.5% distance for each 0.1 runway slope of 1.6% the correction factor is 8%.

Air Transport Operations

There are also specific runway surface and slope correction factors to apply.

If you are operating a light aircraft on Air Transport or Commercial Transport

Part 135 requires you to use Flight Manual

operations, there are specific performance

data to determine takeoff and landing

requirements that must be met in CAR Part

performance. This may include the use of

135 Air Operations – Helicopters and Small

P-charts but the group rating system is not

Aeroplanes, Subpart D.

acceptable for air transport operations.

For example, the takeoff distance required

See Advisory Circular 119-3 Air Operator

must not exceed 85 percent of the takeoff

Certification – Part 135 Operations for details

run available. You must take account of

on how to compile a P-chart and apply the

not more than 50 percent of the reported

applicable Air Transport factors to your aircraft

headwind (or not less than 150 percent of

Flight Manual performance data.

the reported tailwind, as the case may be).

32

Know Your Aircraft

when it comes to deciding whether such

It is useful to work out, and remember, the

calculations are necessary – it is better

takeoff and landing distances required for

to be safe than sorry.

your aircraft in ISA conditions at sea level,

If you own your own aircraft, you might

with nil slope, and nil wind on a sealed

like to consider actually confirming what

runway. This can serve as a basis for

distance it will takeoff and land in under

determining whether it is necessary to carry

these conditions – get to know your

out performance calculations in any given

own aircraft.

situation. Always err on the side of caution

33

Conclusion Takeoff and landing are both high-risk phases of flight. The more that we can do as pilots to minimise these risks, especially when operating out of a short airstrip in an underpowered aircraft,

4. 1973 feet is required.

the safer we will be.

Yes, I could land there at this weight.

If takeoff or landing performance is ever

3. Maximum weight would be 1045 kg.

doubtful, then taking the time to apply

2. Yes – 460 metres would be required.

basic performance calculations is a prudent thing to do and takes the

Landing – 460 metres.

‘she’ll be right’ out of the situation.

1. Takeoff – 570 metres.

Make performance calculations part of

problems from page 35:

your pre-flight planning if you suspect

Answers to aircraft performance

things might be tight.

34

Performance Questions Now that you have seen how to use a P-chart, try these problems by using the chart provided in the original example above (answers on page 34): grass runway, in my private Group 6

1. A private flight, C172P, aircraft weight 1089 kg, QNH 1020 hPa, temperature

Cessna 172P. Assume standard pressure,

20˚C, aerodrome elevation 400 feet,

a temperature of 25˚C, and nil wind.

slope nil, grass/day, wind 250˚M at

The runway is 575 metres long with

5 knots, runway 22.

no slope. What would be the maximum allowable

What takeoff and landing distances

weight for a safe takeoff under these

are required?

conditions? Could I land there at

2. An air transport flight, C172P,

this weight?

aircraft weight 1089 kg, QNH 997

4. A private flight, C172P, aircraft weight

hPa, temperature 26˚C, aerodrome

2400 lbs, QNH 1013 hPa, temperature

elevation 1700 feet, slope 1 percent

25˚C, aerodrome elevation 1000 feet,

down, paved/day, wind 150˚M at

nil slope, grass/day, wind 220˚M at

10 knots, runway 18 (520 metres).

10 knots, runway 22.

Can I safely land on runway 18 in these

Use the Flight Manual data provided below,

conditions?

and any other corrective factors required, to calculate the takeoff distance to 50 feet

3. I would like to fly into Kaikoura

under these conditions.

(elevation 19 feet), which has a Group 4 0˚c

Takeoff Speed KIAS Weight LBS

Lift off

AT 50 ft

2400

51

56

Notes:

10˚c

20˚c

30˚c

Press Alt ft

Ground Total ft Ground Total ft Ground Total ft Ground Total ft roll to clear roll to clear roll to clear roll to clear ft 50 ft OBS ft 50 ft OBS ft 50 ft OBS ft 50 ft OBS

S.L. 1000 2000 3000 4000 5000 6000 7000 8000

795 875 960 1055 1165 1285 1425 1580 1755

1460 1605 1770 1960 2185 2445 2755 3140 3615

860 940 1035 1140 1260 1390 1540 1710 1905

1570 1725 1910 2120 2365 2660 3015 3450 4015

925 1015 1115 1230 1355 1500 1665 1850 2060

1685 1860 2060 2295 2570 2895 3300 3805 4480

1. Decrease distances 10 percent for each 9 knots of headwind. 2. For operation on a dry, grass runway, increase distances by 15 percent.

35

995 1090 1200 1325 1465 1620 1800 2000 ----

1810 2000 2220 2480 2790 3160 3620 4220 ----

PO Box 3555, Wellington 6140 Tel: +64 4 560 9400 Fax: +64 4 569 2024 Email: [email protected] Takeoff and Landing Performance was published in January 2011. See our web site, www.caa.govt.nz, for details of more safety publications.