performance factors

Question 1

what is air density?

Answer 1

the mass in an object divided by its volume. the more dense it is the heavier it is

Question 2

what is air pressure

Answer 2

the force exerted by the air on anything in contact with it. measured with a barometer in hectopascals

Question 3

what happens to air pressure as altitude increases?

Answer 3

air pressure decreases, because air has mass and therefore gravity acts on it and with higher air pressure their is a higher number of air molecules in a given volume or parcel of air.

Question 4

what is the ISA pressure? and what is the pressure lapse rate

Answer 4

1013.2hPa, 1hPa per 30ft

Question 5

what is the temperature lapse rate? and what is the mean sea level ISA temperature?

Answer 5

1.98 degrees per 1000ft

15 degrees

Question 6

what is pressure altitude?

Answer 6

the difference between the air pressure existing at any altitude and the values associated with ISA.

e.g if pressure is 993 hPa

difference of 20 hPa from ISA value of 1013

20 x 30 = 600 ft so pressure altitude = 600ft

pa is the altitude at which we would expect to find the prevailing air pressure

in isa, we would expect to find a pressure of 993hPa at 600ft AMSL

Question 7

for pressure altitude if QNH is less than ISA what should you do and if it’s more what should you do?

Answer 7

less than ISA, add variation to the aerodrome altitude

more than ISA, subtract.

Question 8

how can you determine pressure altitude by using an altimeter?

Answer 8

setting the altimeter to 1013

Question 9

what does temperature do on performance?

Answer 9

if temperature alone is considered, a high temperature is indicative of poorer performance and conversely, low temperatures provide better performance conditions.

must also take air pressure into account.

Question 10

what is density altitude?

Answer 10

the pressure altitude and the affects of temperature.

Question 11

how is density altitude calculated?

Answer 11

find pressure altitude then adjust that for the temperature difference from what we would expect to find at that pressure altitude.

Question 12

what is the adjustment for temperature?

Answer 12

a rate of 1-degree celsius per 120ft

Question 13

what is the difference between high air density and high-density altitude?

Answer 13

a high air density is a great thing for aircraft performance

a high density altitude is a bad thing

Question 14

how does air density affect performance?

Answer 14

high-density day, more air molecules in the same parcel of air allowing greater engine performance and aerodynamic efficiency.

low-density day, less air molecules per same volume of air meaning the opposite.

Question 15

how is ISA temperature found at an altitude?

Answer 15

ISA temp at MSL = 15 degrees with a lapse rate of 2 degrees per 1000ft

e.g pressure altitude of 2000ft at 2000ft is 11 degrees
( 2000ft x 2 C per 1000ft = 4 degrees) 15 - 4 = 11

Question 16

how is ISA temperature deviation found?

Answer 16

by finding the ISA temperature at an altitude and by adding or subtracting it relative to the ISA

ISA temp at pressure altitude of 2000ft is 11 degrees
(2000ft x 2degrees per 1000ft = 4 degrees) 15 - 4 = 11 or ISA - 4

Question 17

how is density altitude calculated?

Answer 17

multiplying the ISA temperature deviation with the adjustment for temperature (120 ft per 1 degree) then adding it onto the pressure altitude

e. g PA = 4000 ft ISA temp = ISA - 4
- 4 x 120 = -480ft

4000ft - 480ft = 3520 ft

Question 18

what is the difference between TODR and TODA?

Answer 18

TODR is the actual distance that an aircraft requires from a standing start, with full power, to get to 50 feet above the runway at takeoff safety speed.

TODA is the length of the take off run available plus the length of any clearway ( a portion of ground or water that an aircraft may climb over)

Question 19

what is the difference between LDR and LDA?

Answer 19

LDR - horizontal distance from a point 50ft above the threshold, to the point that the aircraft can be brought to a complete stop with max braking.

LDA - length of the runway that’s declared by the airfield operator as available and suitable for the ground run of an aircraft.

Question 20

where is TODR, TODA, LDR and LDA found?

Answer 20

in the NZAIP VOL 4 containing all the info. may have stuff like circles on the runway meaning you cannot land in the first ___ metres of that runway which is known as a displaced threshold.

Question 21

how does weight affect takeoff performance?

Answer 21

heavier aircraft require greater takeoff distance. due to slower acceleration on the runway and the requirement for increased flying speed to provide the required safety margin (20%) above the increased stall speed.

Question 22

how does density affect takeoff performance?

Answer 22

low air density results in a greator TODR because of poorer performance of the engine and airframe.

occurs on hot days, low-pressure days, high elevation aerodromes

Question 23

how does humidity affect takeoff performance?

Answer 23

high humidity reduces air density meaning poorer performance

Question 24

how does temperature affect takeoff performance?

Answer 24

causes poor performance

Question 25

how does runway slope affect takeoff performance?

Answer 25

upslope will require more distance than a flat or downslope

Question 26

how does runway surface affect takeoff performance?

Answer 26

anything increasing drag between wheels and runway surface will degrade takeoff performance, thus long grass, water or slush on the runway and potholes and bumps will result in a longer TODR.

Question 27

how does the wind component affect takeoff performance?

Answer 27

a headwind will reduce TODR since it’ll take less time for the aircraft to reach flying speed.

Tailwind will cause an aircraft to take a longer time.

Question 28

how do contaminants affect takeoff performance?

Answer 28

contaminants have a strong degrading effect on takeoff performance and result in a greater TODR.

Question 29

how does flap affect takeoff performance?

Answer 29

creates higher amounts of drag meaning TODR is increased.

Question 30

how does weight affect landing performance?

Answer 30

heavier aircraft require greater LDR due to the higher approach speed required and the higher momentum on touchdown.

Question 31

how does density affect landing performance?

Answer 31

low density results in a greater LDR because of the higher TAS of the aircraft on approach and landing.

Question 32

how does runway slope affect landing performance?

Answer 32

because a downslope encourages the aircraft to maintain its forward speed and upslope slows it down quicker.

Question 33

how does runway surface affect landing performance?

Answer 33

slippery or wet runway will reduce braking action increasing LDR. long grass and long wet grass will reduce the LDR but if the deceleration is too severe risk of aircraft nosing over is there.

a soft surface will reduce the landing roll but there’s a risk wheels sink deep into the surface and get stuck, potholes and bumps cause aircraft to skip increase LDR.

Question 34

how does wind component affect landing performance?

Answer 34

a headwind will reduce LDR since the aircraft, provided its flow at the correct approach speed will touch down at a lower Groundspeed.

tailwind causes groundspeed to be higher so LDR will increase.

Question 35

how do flaps affect landing performance?

Answer 35

allow a slower approach speed and will shorten LDR.

Question 36

what are the hazards surrounding windshear during takeoff or initial climb or final approach?

Answer 36

when win is light or calm immediately above the surface and stronger above a certain height.

under these conditions, the flight path will be affected and the rate of climb or descent will change abruptly. recovery from windshear takes time and height and when limited may make it too hard to recover.