22.32.8
Express an ambient temperature as a deviation from ISA temperature (and vice versa).

ISA temperature is 15°C at sea level. The standard deviation with altitude gain is 2°C per 1000ft

If you are flying at 3000ft and the temperature at that altitude is +20°C it is possible to calculate the temperature deviation from ISA

1. Temperature at ISA is calculated by 15- (3 X 2) = 15 – 6 = 9°C
2. Difference between ambient and ISA is 20 – 9 = 11°C
3. Thus ambient temperature is ISA +11°C

22.32.6
Given an elevation, QNH and ambient temperature, calculate pressure altitude and density altitude.

Considerations

Pressure altitude is obtained by adding pressure variations caused by changes in ambient pressure to the selected airfield elevation. 

Density altitude is obtained by correcting pressure altitude for changes in temperature due to deviation from expected ISA temperatures. 

Pressure Altitude

Pressure altitude is obtained by adding pressure variations caused by changes in ambient pressure to the selected airfield elevation. 

Assuming a selected airfield with an elevation of 1000ft, and a QNH of 1000hPa; what is the pressure altitude at the airfield?

1. Determine the pressure variation from ISA: 1013-1000=13hPa
2. Apply the formula 13 (hPa) X 30ft = 390ft
3. Apply the variation in height to the actual airfield elevation. Since the sea-level pressure (QNH 1000hPa) is less than ISA we can expect the performance of the aeroplane at the selected airfield to be poorer than standard: Therefore pressure altitude is 1000 + 390 = 1390ft

Density Altitude

Assuming the above airfield with an elevation of 1000ft, a QNH of 1009hPa and an ambient temperature of +11°C, calculate the airfield density altitude:

1. Obtain airfield pressure altitude. 
2. Determine ISA temperature at pressure altitude 1390 ft 15-(2X1.4) = 12.2°C
3. Compare ISA temperature (+12.2) to the actual temperature (+11) and determine the temperature deviation, (ISA-1.2) Lower temperature gives a lower density altitude
4. Calculate deviation height -1.2 X -120 = -144ft.   
5.  Add to pressure altitude  1390 – 144 = 1246ft 

22.32.4
Explain the factors affecting take-off and landing performance.

Factors Affecting Takeoff and Landing Performance

Under Part 135 each flight must have takeoff and landing data calculated. 

When calculating the takeoff distance we must take into account

1. The takeoff run available;
2. The weight of the aeroplane at the commencement of the takeoff run;
3. The density altitude of the aerodrome;
4. The type of runway surface and the runway surface condition;
5. The runway slope in the direction of takeoff; and,
6. Not more than 50% of the reported headwind component  or not less than 150% of any reported tailwind component

When calculating the landing distance the operator is required to take into account 

1. The landing distance available 
2. Aerodrome elevation
3. Ambient temperature
4. The type of runway surface and the runway surface condition
5. The runway slope in the direction of landing
6. Not more than 50% of the reported headwind component or not less than 150% of any reported tailwind component 

All this applies to a dry runway. For wet or contaminated runways the landing distance must be increased by 15%

When the appropriate weather reports or forecasts, or a
combination of them, indicate that the runway at the estimated
time of arrival of the aeroplane may be wet, the landing distance
available is at least 115% of the landing distance required by
135.223

(h) Drift Down

Drift down means the gradual descent of an aircraft operating with one engine inoperative to an altitude at which it can comply with the one-engine inoperative en-route climb performance requirements.

(g) Dry, Wet and contaminated (in relation to runway surface)

Dry runway

Means a runway that is not contaminated and includes a paved runway that has been specially prepared with grooves or a porous pavement to retain effectively dry-braking action even when liquid moisture is present.

                                          

Wet runway

Wet in relation to a runway, means a runway with sufficient moisture on it’s surface to cause it to appear reflective but without any areas of standing water.

               

Contaminated runway

Contaminated in relation to a runway means more than 25% of the runway surface area within the required length and width is covered by surface water, slush, or loose snow more than 3mm in depth, or ice on any part of the runway surface area.

     

(f) Landing Distance Available

Landing distance available means the length of the runway that is declared by the aerodrome operator as available and suitable for the ground run of an aeroplane.

The landing distance available starts at the landing threshold and in many cases corresponds to the physical length of the runway. However the landing threshold may be displaced from the end of the runway when it is considered necessary to make a corresponding displacement of the approach area and surface for reason of obstruction in the approach path to the runway.

(e)Gradient, Gross and Net Flight Paths.

Gradient of climb means the ratio of height gained over a horizontal distance travelled, expressed as a percentage

e.g. If the height gained is 500ft over a horizontal distance of 8000ft:

climb gradient = height gained/distance travelled = 500/8000 = 0.063

This means that for each foot travelled horizontally you climb 0.063ft

This can be converted to a percentage my multiplying by 100/1 so that:

Climb gradient = 500/8000 X 100/1 = 6.3%

Gross and Net Flight Paths

Gross flight path means the flight path it is assumed the aeroplane will follow then flown in a particular configuration in accordance with specified procedure.

Net flight path means the gross flight path reduced by specified margins. These margins, which will be specified in the rules make allowances for the reduced performance that could be expected in a real emergency situation in unfavourable conditions (i.e. severe turbulence)

(b) Takeoff Distance Available

Takeoff Distance Available (TODA) is defined as the length of the takeoff run available plus the length of any clearway

Clearway is defined as an area in which an aeroplane may make a portion of its initial climb to a specified height

                                           

(c)Takeoff Run Available

Takeoff Run Available (TORA) means the length of the runway declared by the aerodrome operator as available and suitable for the ground run of an aeroplane taking off

(d)Accelerate-Stop Distance Available

The Accelerate-Stop Distance Available (ASDA) means the distance specified by the appropriate authority as being the effective length available for use by an aeroplane executing an abandoned (or rejected) takeoff. The effective length includes any stop-way.

A stop-way is a defined as an area on the ground in which an aircraft can be stopped in the case of an abandoned takeoff. A stop-way must be included within the strip. 

                   

The longer the declared accelerate stop distance ..

• The higher the speed beyond which an aircraft can be bought to a halt in the case of an abandoned takeoff; and
• The greater the allowable takeoff weight

A stop-way does not necessarily have to be a prepared sealed or level grass surface, but a reasonably flat area suitable for braking and bringing an aircraft to a stop in an emergency. 

The Accelerate-Stop Distance Available (ASDA) is promulgated as part of the runway information for appropriate aerodromes. The accelerate-stop distance required (ASDR) under varying conditions can be calculated from tables or graphs in the aircraft flight manual.

(a) Takeoff distance required (TODR),  takeoff safety speed and screen height (or barrier)

Takeoff distance required (TODR) is the distance required to takeoff from a standing start at maximum takeoff power and reach a screen height (usually 50 feet) above the runway at the takeoff safety speed.

Takeoff safety speed (TOSS) is a speed that gives an adequate safety margin about the stalling speed. It must not be more than 1.2Vs in the takeoff configuration. TOSS will normally be incorporated in the takeoff climb speed given in the flight manual for the type.

Screen height The screen height for light aircraft is 50 feet, but for large aircraft and for commuter operations it may be 35 feet (or lower in some circumstances)

22.32.2
Define:
(a) Take-off distance required (TODR), take-off safety speed, and screen height (or barrier);
(b) Take-off distance available (TODA) and clearway;
(c) Take-off run available (TORA);
(d) Accelerate-stop distance available (ASDA) and stopway;
(e) Gradient and gross and net flight paths;
(f) Landing distance available (LDA), landing distance required (LDR) and landing threshold;
(g) Dry, wet, and contaminated (in relation to runway surface);
(h) Drift down.