Tutorial: altitude and altimeters

Groundschool – Theory of Flight

Altitude and altimeters

Revision 44 — page content last expanded 15 May 2012.

The instrument for indicating the aircraft's altitude, the altimeter, measures static air pressure and is calibrated in accordance with the ICAO international standard atmospheric pressure and temperature model. Air density has a significant effect on aircraft take-off performance, and equivalent air density at the airfield can be ascertained from the ambient air pressure and air temperature.

Content

3.1 The altimeter
3.2 Altitude and Q-code definitions
3.3 Physiological effects of altitude
3.4 High density altitude: effect on take-off/landing performance
3.5 Calculating density altitude
Things that are handy to know
Stuff you don't need to know

3.1 The altimeter

The altimeter is the cockpit instrument that indicates the aircraft's altitude. The instrument is a refined aneroid barometer with a dial indicating height above a pre-set level rather than atmospheric pressure. The main component of such an instrument is a small, flexible, corrugated metal capsule from which the air has been partially evacuated — fitted with a metal closure or diaphragm. There is a spring within the capsule that applies a constant force to the bottom of the diaphragm, while atmospheric static pressure applies a counter force to the top, so that the diaphragm moves as atmospheric pressure changes. The movement of the pressure-sensing capsule is transferred and magnified — via a mechanical linkage or piezo-quartz component — to a dial pointer or pointers, or a digital display, which indicate the altitude reading. The static pressure is drawn from the aircraft's static vent, which may induce slight position errors due to aerodynamic effects around the vent.

The level in the atmosphere at which any particular pressure occurs is also dependent on temperature — as we saw in the 'Airspeed and the properties of air' module — but the altimeter does not sense the air temperature. Consequently, all altimeters are calibrated in accordance with the International Standard Atmosphere [ISA] model, which utilises a standard temperature lapse rate with height of 6.5 °C per km. The atmosphere in any region rarely corresponds to the ISA, so aneroid altimeters do not indicate totally accurate height. This is not that important, as true altitude can be calculated, in the rare circumstance that it is needed for terrain clearance purposes. There is no problem with air traffic management, in that all aircraft in the same region, with properly set (and functioning) altimeters, will be out by the same amount.

altimeter face

It is, of course, desirable to set the current local surface pressure into the altimeter by setting that reference pressure into a pressure-setting scale (known since the 1930s as the 'Kollsman* window'), which in turn resets the position of the height-indicating pointers against the dial. Or, if the aircraft is on the ground, the same result is achieved by turning the pressure-setting scale until the altimeter indicates the known airfield elevation. The sensitive altimeter in the image indicates an altitude of about 1410 feet with the baro-scale set at 29.9 inches of mercury [in/Hg] — equivalent to 1013 hPa. If the altitude was 11400 feet, the pointer with the inverted triangle on the end would be past the figure 1 on the image, indicating +10 000 feet.

*Paul Kollsman invented his 'sensitive altimeter' in 1929 which was a far superior instrument to those existing at the time but it didn't gain widespread use until 'instrument flying' became common later in the 1930s.

In Australia, all barometric pressures are reported in hectopascals [equivalent to millibars]; and in the USA in units of inches of mercury [in/Hg =33.86 hPa]. The sub-scale setting range provided in modern altimeters is from 850 to 1050 hPa.

Electronic altimeter

Electronic flight instrument systems [EFIS] use solid-state electronic componentry plus software to display the usual flight instrument readings on a liquid crystal, or similar, screen. In such systems, the atmospheric static pressure is fed to a pressure transducer, which senses and convert pressures to voltages. See the screen display of the Dynon D10A light aircraft EFIS. Note that the EFIS has an outside air temperature probe and the software can calculate density altitude (see section 'Altitude and Q-code definitions') when needed.

Electronic altimeters are also available as single instruments or possibly combined with an ASI function.

Altitude encoding

In some flight conditions, an aircraft must operate a transponder for traffic separation purposes. The transponder obtains altitude data from a special altitude encoding altimeter or from a blind encoder; the latter being an electronic device that obtains current atmospheric pressure from the static pressure line and the reference pressure used is preset at 1013.2 hPa. That same reference pressure is used for the altitude encoding function of the altimeter, thus the transponder broadcasts pressure altitude only.

3.2 Altitude and Q-code definitions

Altitude

Altimeter indicated altitude: the approximate height of the aircraft above mean sea-level [amsl], calculated in accordance with the ISA.

Calibrated altitude: the indicated altitude, corrected for internal instrument error and static vent position error.

Pressure altitude: the altimeter reading when the pressure-setting scale is set to 1013.2 hPa, usually termed pressure height in reference to an airfield reading. It is the ISA Standard Pressure setting. Standard pressure is also the standard factory setting for altitude encoding devices. All aircraft cruising in the Standard Pressure Region — above a transition layer that (in Australia) commences at 10 000 feet — use the standard pressure setting, and the subsequent altimeter reading is normally referred to as flight level [FL]. However an aircraft maintaining a constant altitude using 1013.2 hPa, or any other fixed setting for that matter, is following an isobaric surface whose height amsl will vary according to atmospheric conditions. An aircraft maintaining FL145 (i.e. 14 500 feet), and flying towards a lower pressure area, will actually be descending at a rate approximating 40 feet per one hPa decrease in surface level pressure.

True altitude: the calibrated altitude corrected for atmospheric temperature conditions. But as the correction will assume standard pressure and temperature lapse rates between the surface and the aircraft level, it will not be an accurate reflection of the aircraft's height above mean sea-level. If you maintain a particular altitude, you will be following an isobaric surface and not maintaining a constant height. The only way to measure height accurately is by triangulation — and that can only be done by a GPS receiver in the aircraft. However, there are still problems in determining the vertical datum. See geoid-ellipsoid separation.

Density altitude: a calculation used to determine possible aircraft performance — see section 'High density altitude' below. This is the pressure altitude adjusted for variation from standard temperature, or the height in ISA having a density corresponding to the location density, then called density height.

Declared density altitude: see the section 'High density altitude: effect on take-off/landing performance' below.

Pivotal altitude: is not associated with altimeter setting; it is a term used by the proponents of 'ground reference' manoeuvres such as 'eights on pylons'. It is a particular height above ground at which, from the pilot's viewpoint, the extended lateral axis line of an aircraft doing a 360° level turn (in nil wind conditions) would appear to be fixed to one ground point, and the aircraft's wingtip thus pivoting on that point. The pivotal altitude in nil wind conditions is easily calculated by squaring the TAS in knots and dividing by 11.3. So an aircraft circling at 80 knots would have a pivotal altitude around 550 feet, no matter what the bank angle.

When an aircraft is turning at a height greater than the pivotal altitude, the wingtip appears to move backwards over the landscape. When an aircraft is turning at a height less than pivotal altitude (i.e. usually close to the ground) the wingtip appears to move forward over the landscape. For more information see 'pivotal altitude and reversal height'.

Q-codes

Note: the letters in the Q-code nomenclature have no literal significance; these are remnants of an extensive notation system from the days of wireless-telegraphy. There were some 200 three-letter Q-codes, each representing a sentence, a phrase or a question. For instance, QRM "I am being interfered with"!. Some 30 Q-codes are still used by amateur radio/morse code enthusiasts and the four below, plus QDM (the magnetic bearing to a station), still survive in aviation. For a full listing of Q-codes google 'all Q codes'. The following four codes relate to altimeter settings.

QFE: the barometric pressure at the station location or aerodrome elevation datum point. If QFE is set on the altimeter pressure-setting scale while parked at an airfield, the instrument should read close to zero altitude — if the local pressure is close to the ISA standard for that elevation. However, the use of QFE is deprecated and anyway, if the airfield elevation is higher than perhaps 3000 feet, older/cheaper altimeters may not be provided with sufficient sub-scale range to set QFE.

QFF: the mean sea-level [msl] pressure derived from the barometric pressure at the station location. This is derived by calculating the weight of an imaginary air column extending from the location to sea-level — assuming the temperature and relative humidity at the location are the long-term monthly mean, the temperature lapse rate is ISA, and the relative humidity lapse rate is zero. This is the method used by the Australian Bureau of Meteorology; QFF calculations differ among meteorological organisations. QFF is the location value plotted on surface synoptic charts and is closer to reality than QNH, though it is only indirectly used in aviation.

QNH: the msl pressure derived from the barometric pressure at the station location by calculating the weight of an imaginary air column extending from the location to sea-level — assuming the temperature at the location is the ISA temperature for that elevation, the temperature lapse rate is ISA and the air is dry throughout the column.

The Australian aviation regulations state that when an 'accurate' QNH is set on the pressure-setting scale at an airfield, the altimeter indication should read within 100 feet of the published airfield elevation, or 110 feet if elevation exceeds 3300 feet; otherwise the altimeter should be considered unserviceable. However, due to the inherent inaccuracy possible in QNH, this may not be so. The difference between QFF and QNH when calculated on a hot day at a high airfield in Australia can be as much as 4 hPa, equivalent to about 120 feet. The advantage to aviation in using the less realistic QNH is that all aircraft altimeters in the area will be out by about the same amount, and thus maintain height interval separation.

The Local QNH at an airfield is normally derived from an actual pressure reading. But the Area QNH used outside the airfield zone is a forecast value, valid for three hours, and may vary by up to 5 hPa from any Local QNH in the same area. Either Local QNH or Area QNH may be set on the altimeter pressure-setting scale of all aircraft cruising in the Altimeter Setting Region, which (in Australia) extends from the surface to the Transition Altitude of 10 000 feet. The cruising levels within the Altimeter Setting Region are prefixed by 'A'; e.g. A065 = 6500 feet amsl.

When there is no official Local QNH available at an airfield and the site elevation is known, the Local QNH can be derived by setting the sub-scale (when the aircraft is on the ground at the location) so that the altimeter indicates the known airfield elevation. The use of Local QNH is important when conducting operations at an airfield, as the circuit and approach pattern is based on determining height above ground level [agl].

Note that it is not mandatory for VFR aircraft to use the area QNH whilst enroute. You may substitute the current local QNH of any aerodrome within 100 nm of the aircraft or the local QNH at the departure airfield. See 'Acquiring weather and QNH information in-flight'.

The purpose of the Transition Layer is to maintain a separation zone between the aircraft using QNH and those using the standard pressure setting. Cruising within the Transition Layer is not permitted. If Area QNH was 1030 hPa, there would be about 500 feet difference displayed between setting that value and setting standard pressure. The Transition Layer extends from the Transition Altitude to the Transition Level which, in Australia, is usually at FL110 but it may extend to FL125 — depending on Area QNH. More detail is available in 'Aeronautical Information Publication (AIP) Australia' section ENR 1.7; downloadable from Airservices Australia.

QNE: common usage accepts QNE as the ISA Standard Pressure setting of 1013.2 hPa. However another definition of QNE is the 'altitude displayed on the altimeter at touchdown with 1013 set on the altimeter sub-scale'. It is also referred to as the 'landing altimeter setting'.

Within the latter meaning, the term is only likely to be used when an extremely low QNH is outside an aircraft's altimeter sub-scale range, and the pilot requests aerodrome QNE from air traffic services. In Australia, such extreme atmospheric conditions are only likely to occur near the core of a tropical depression/cyclone and as QNE is not listed in the ICAO "Procedures for Air Navigation Services", air traffic services would not provide QNE on request.

However, QNE can be calculated by deducting the QNH from 1013, multiplying the result by 28 (the appropriate pressure lapse rate per hPa) and adding the airfield elevation.

For example: QNH 960 hPa, airfield elevation 500 feet, pressure setting 1013.
QNE = 1013 –960 = 53 × 28 = 1484 + 500 = 1984 feet (the reading at touchdown).

3.3 Physiological effects of altitude

The tissues and organs of the human body need a constant and adequate supply of oxygen to function at maximum efficiency; insufficient oxygen in those tissue and organs is called hypoxia. There are many causes for the condition, but the one of most interest to sports and recreational aviators is the hypobaric form of hypoxia caused by continuing flight at an altitude where the partial pressure of the atmospheric oxygen is less than that required for proper functioning of the brain. The body utilises the oxygen partial pressure to pass it through the membrane of the lung alveoli into the bloodstream.

(The 'stagnant' forms of hypoxia — greyout and blackout — caused by reduced blood flow to the eyes and brain at aircraft accelerations exceeding +3g to +4g is also, of course, of interest to aerobatic pilots. For a pilot of average fitness, greyout (dimness of vision) will start between +3.5g and +4.5g, reaching blackout (complete loss of vision) between +4g and +5.5g and g-induced loss of consciousness [GLOC] between +4.5g and +6g.) The application of perhaps –2g or –3g causes increased blood flow to the eyes, resulting in leakage from the blood vessels –redout. Prolonged application of high negative g may severely damage the eyes.

Atmospheric oxygen partial pressure declines as altitude increases; see the atmospheric oxygen section in the Aviation Meteorology Guide. The table in that section shows the time a reasonably fit person will remain conscious at those altitudes without using supplemental oxygen. However, the effects of hypoxia commence at much lower altitudes, probably around 8000 feet for a fit person, less if unfit though much lower for a heavy smoker. These effects include a gradual deterioration in thinking, calculating and reacting; inability to make appropriate judgements; light headedness and a poor memory recall. Unfortunately, the afflicted person is usually quite unaware of the symptoms occurring and may enjoy a feeling of well-being even, perhaps, euphoria. For more information read the article 'Hypoxia' from Flight Safety Australia magazine.

In Australia recreational aircraft may only be flown at or above 10 000 feet amsl if the pilot has applied to and received written permission for that flight from the Civil Aviation Safety Authority. The aircraft must be equipped with an operating Mode A/C or S transponder. Also the Australian Civil Aviation Order Part 20.4 paragraph 6 which applies to all Australian aircraft, requires that: "A flight crew member who is on flight deck duty in an unpressurised aircraft must be provided with, and continuously use, supplemental oxygen at all times during which the aircraft flies above 10 000 feet altitude." Note that an aircraft may not cruise within the transition layer and that layer could extend to FL125.

3.4 High density altitude: effect on take-off/landing performance

High 'density altitude' conditions at an Australian airfield, particularly in summer, can provide severely hazardous conditions for any aircraft where the difference between power required and power available is small. This concerns most general aviation and all sport and recreational aircraft engaged in take-off or landing at that airfield. It is the density of the air that provides thrust and lift.

Effect of density altitude on performance

What we are really doing when calculating density altitude is estimating the density of the air. In ISA conditions, at a density altitude of 6000 feet amsl, the air density will be about 1.0 kg/m³ (about 20% less than sea-level standard). So the weight of the charge delivered to the cylinders, in a normally aspirated engine, will be only 80% of the standard sea-level value. Thus, only 80% of the engine's rated power can be supplied at the propeller shaft for take-off and climb-out, or for a go-around. As well as that, the lower air density (½r in the lift equation) directly reduces the thrust performance of the fixed-pitch propeller by 10% in which case the thrust performance will be 90% of 80%, or about 72% of the rated sea-level performance.

The maximum lift possible to be generated will be reduced by 10% (lift = C_L × ½rV² × S ) and the ground roll speed related to IAS/CAS prior to take-off will be higher; i.e. during take-off at msl in ISA sea-level conditions TAS = IAS/CAS, but in high density altitude conditions TAS is greater than IAS/CAS. So, at 6000 feet density altitude the TAS at lift-off would be about 10% higher (see rule of thumb) than msl conditions thus the aircraft has to accelerate to a 10% higher ground roll speed before reaching lift-off IAS. and both the time and the distance needed to acquire take-off lift — and to clear obstacles at the end of the strip — must be increased. And that is before taking into account the effect of reduced engine/propeller performance on take-off distance. Remember that V² in the lift equation refers to TAS not CAS.

There are many conditions that exist, or might exist, at high density altitude which, though they may be individually slight, all affect the airframe and engine performance adversely. For instance, attempting take-off with a combination of some of the following conditions may cause some difficulty; attempting take-off when most conditions exist may well be disastrous:

at an elevated airfield
with high surface temperature
on a short, soft strip with unslashed, wet grass
at maximum weight
incorrect flap setting
light and variable winds
departing into rising terrain and a sinking air environment.

The same conditions apply when landing; the TAS at Vref will be higher and the consequent ground roll will be longer. The thrust available for a go-around, in the event of an aborted approach, might be very much less than the rated msl thrust, which would probably preclude a go-around.

Also, it must be borne in mind that the air is not dry; rather, the absolute humidity may be very high. This does not have a significant effect on lift, but does adversely affect the engine performance a little. In a carburation or injection system fuel is metered on the volume of gas being inducted whether it is air or water vapour. With water vapour in the gas, there is less air present. This enriches the mixture slightly as the fuel is metered for the total volume of gas. Water vapour slows burning, which slightly affects power.

In addition, under high density altitude conditions, the mixture may be excessively over-rich. The recommendation for normally aspirated engines with cockpit mixture control is that the mixture should be leaned to maximum rpm before taxying, take-off or landing if the density altitude is 5000 feet or greater.

Density altitude at a particular location can vary considerably from day to day, and also according to time of day. For instance, the table below shows a mid-afternoon and an early morning reading at Alice Springs, in central Australia, on different days. The airfield elevation is 1900 feet.

QFE	Temperature	Air density	Pressure altitude	Density altitude
941 hPa	43 °C	1.037	2020 feet	5600 feet
957 hPa	–2 °C	1.230	1580 feet	–100 feet

3.5 Calculating density altitude

The density of dry air (r) varies according to ambient air pressure and ambient air temperature, this is reflected in the equation r = pressure (P) divided by 2.87 times the temperature (T). Pressure (or pressure altitude) is readily obtained from the altimeter, and temperature can be obtained from various sources.

Method 1: use the temperature differential

Density altitude is roughly 120 feet greater than pressure altitude for each 1 °C that the temperature exceeds ISA for that level, and 120 feet less for each 1 °C that the outside air temperature is less than ISA. In the ISA table sea-level temperature is 15 °C and the ISA temperature lapse rate is 2 °C per 1000 feet.

For example: Armidale, New South Wales, airport (elevation 3550 feet) on a warm day, temperature 30 °C. Altimeter, with 1013.2 standard sea-level pressure sub-scale setting, reads 3400 feet pressure height/altitude.

ISA standard temperature for an elevation of 3550 feet = [15 –(3.55 x 2)] = 8 °C.
The Armidale temperature then exceeds standard by 22 °C, thus adjustment to be added= 22 × 120 = 2640 feet
Pressure altitude = 3400 feet
Then the approximate density altitude = 2640 + 3400 = 6040 feet.

Method 2: calculate using the air density equation

The density of dry air at altitude can be calculated using the equation:
r = P / (2.87 T), where:

r = rho — the density of dry air [kg/m³]
P = the pressure [hPa]
2.87 = the gas constant for dry air
T = the air temperature [K].

Using the Armidale example, with the altimeter set so that altitude shows the elevation of 3550 feet, the pressure-setting sub-scale will display 895 hPa (i.e. QFE). The temperature is 303 K (30 °C + 273) thus density = 895 / (2.87 × 303) = 1.029 kg/m³. The height in ISA having a corresponding density is about 5850 feet. This gives a slightly more accurate calculation of density altitude than method 1.

Method 3: use the CASA declared density altitude charts

The ICAO International Standard Atmosphere model is based on average conditions in mid-latitude (30° to 60° N&S) temperate climates and as such does not reflect conditions over much of Australia. The Civil Aviation Safety Authority recognises this and publishes seasonal 'declared density altitude' charts showing regional values to be added to airfield elevation to give declared density altitude. The three seasonal charts (summer, winter and autumn/spring) are published as appendices to Civil Aviation Regulations section 20.7. For example the summer chart shows regional values of 2000 feet in the south-east and 3600 feet in central areas. These regional values are to be used only if there are no other means of calculating current density altitude at the departure and destination airfields.

Armidale is located at 30° S and 151° E between the 2800 and 3000 feet contour lines of the summer chart, so adding 2900 to the airfield elevation of 3550 feet gives a declared density altitude of 6450 feet.

Method 4: use a density altitude computational chart

First determine current pressure altitude with 1013 hPa standard pressure setting on the altimeter sub-scale, for example 3400 feet. Also determine outside air temperature, for example 30 °C. Draw a horizontal line from the 3400 feet position to the 30 °C vertical line. Determine the density altitude scale at which the line terminates, for this example density altitude = 6000 feet.

Click the image for a larger scale printable computational chart.

Method 5: use an E6-B type circular scale computer

The plastic circular slide rule flight planning computers have a density altitude facility that just entails placing the pressure altitude opposite temperature and reading off density altitude from a third scale. The scales are small and difficult to set accurately but the Jeppesen Model CR-3 computer indicates about 6000 feet density altitude for the Armidale example.

Method 6: use the information in the Pilot's Operating Handbook

Charts in the Pilot's Operating Handbook or Flight Manual provide density altitude plus aircraft performance and maximum weight figures from the input of pressure altitude and temperature.

Before you can start to estimate the take-off distance required under high density altitude conditions, you must know the take-off distance required under standard ISA mean sea-level conditions.

CAO 101-28, an airworthiness certification requirements for commercially supplied amateur-built kit ultralights, states in part:
"The take-off distance shall be established and shall be the distance required to reach a screen height of 50 feet from a standing start, with ... short, dry grass surface ... the aeroplane reaching the screen height at a take-off safety speed not less than 1.2 Vs1 ... take-off charts ... shall schedule distances established in accordance with the provisions of this paragraph, factored by 1.15."

Sea-level ISA and nil wind conditions are implied.

CAO 101.55 has much the same wording, but specifies 1.3 Vs1 as the take-off safety speed. FAR Part 23 is similar.

CAO 101-28 also requires that the landing distance stated will be that to come to a full stop from a screen height of 50 feet at the threshold, with the screen being crossed at 1.3 Vso and the same conditions as specified for the take-off distance. Refer to Vref.

If buying an aircraft or kit, you should require that the standard take-off and landing distance chart information for the airframe/engine/propeller combination be supplied. Statements such as "Take-off ground roll 10 m to 40 m" have no value. You must insist, particularly with imported aircraft, that the distances should be stated clearly in one form only and for nil wind conditions "Take-off distance to clear 50 feet (15 m) screen" or "Landing distance over 50 feet (15 m) screen". You have to know without doubt, having done the necessary calculations, that you can clear obstacles at the end of the unslashed paddock on a hot, bumpy day without risk to you or your passenger, and that if it is necessary to abort a landing, the aircraft will have the ability to go-around safely.

For more information on take-off and climb performance in high density altitude conditions, see take-off considerations.

[ The next section in the airmanship and safety sequence is section 9.1 Consequences of exceeding MTOW ]

Things that are handy to know

Altimeter rules of thumb

   • For each 10 °C that the outside air temperature is warmer than ISA standard, increase the indicated altitude by 4% to give true altitude. Conversely, for each 10 °C cooler, decrease indicated altitude by 4% — 10/273 approximates to 4%; refer to Charles' law.

   • When flying from higher to lower pressure conditions, without altering QNH, the altimeter will — if below 10 000 feet — overread (indicate higher than actual altitude) by about 30 feet for each one hPa pressure change.

   • When flying from lower to higher pressure conditions, without altering QNH, the altimeter will — if below 10 000 feet — underread (indicate lower than actual altitude) by about 30 feet for each one hPa pressure change.

   • If the altimeter sub-scale setting is less than QNH the altimeter will overread. Conversely, if the setting is greater than QNH, the altimeter will underread.

   • Air density decreases by about 1% for each:
   — 10 hPa fall in pressure, or
   — 300 feet increase in height, or
   — 3 °C increase in temperature, from the msl standard.

Stuff you don't need to know

   • There is a semi-diurnal atmospheric tide, similar to the oceanic tide, which is most apparent in the lower latitudes. The tide peaks at 1000 hrs and 2200 hrs local solar time, with the minima at 0400 hrs and 1600 hrs. At Cairns, 17° S latitude, the daily minima and maxima are 2 hPa either side of the mean pressure; e.g. 0400 hrs — 1014 hPa; 1000 hrs — 1018 hPa; 1600 hrs — 1014 hPa; 2200 hrs — 1018 hPa. The runway elevation at Cairns is 10 feet amsl, so that if you left a parked aircraft at 1600 hrs with the altimeter reading 10 feet, six hours later it would be reading 110 feet below mean sea-level. When making their regular pressure reading reports, weather observation stations adjust the reported QFF according to a 'time of day' table.

   • There is also a semi-diurnal gravity variation at the Earth's solid surface, also peaking at 1000 hrs and 2200 hrs. A movement of 50 cm from the low to high earth tide has been ascertained in central Australia.

   • Perhaps the highest surface pressure recorded is 1083.3 hPa at Agata, Siberia on 31 December 1968. It is not known whether this was QFE or QFF. Agata is 850 feet amsl.

The next module in this Flight Theory Guide discusses lift generation, aerofoils and wings.

Groundschool – Flight Theory Guide modules

| [3. Altitude & altimeters] | 4. Aerofoils & wings | 5. Engine & propeller performance |

| 10. Weight shift control | 11. Take-off considerations | 12. Circuit & landing |

| 13. Flight at excessive speed | 14. Safety: control loss in turns |

Supplementary documents

| Operations at non-controlled airfields | Safety during take-off & landing |

The next section within the Aviation Meteorology ground school covers cloud, fog and precipitation