AVAT11001: Course Outline 1.Aircraft and Terminology 2.Radio Communications 3.Structure, Propulsion, Fuel Systems 4.Electrical, Hydraulic Systems and Instruments 5.Air Law 6.Aerodynamics: Basics 7.Aerodynamics: Performance 8.Human Factors 9.Meteorology 10.Loading 11.Take-off and Landing Performance 12.Navigation

Stuff to read Required Reading: –BAK Chapter 11, pp –VFG EMERG, pp

The Atmosphere Recall the ISA, International Standard Atmosphere The ISA is a reference model –Used for performance comparisons How does your aircraft compare to another aircraft How will your aircraft perform today compared to a “Standard Day” –Not the actual weather Aircraft performance (take-off distance, rate of climb, etc) is greatly affected by pressure, temperature and density –These parameters all decrease as altitude increases in the ISA model –See Figure 11-1 page 333

Performance and the ISA When performance charts are created, they are referenced to standard atmospheric conditions. To evaluate the how your aircraft will perform, you will need to be able to compare you current weather conditions to an equivalent “standard day”

Pressure Height An altimeter is designed to take the current static pressure, and display the altitude you would be at on a standard day This altitude is known as “pressure height” For a pressure of 900 hPa, the altimeter will display about 3000 feet hPa

QNH Pressure height is very rarely your actual altitude AMSL. To assist pilots, most aerodromes will forecast their local QNH –QNH is a value you can set on your altimeter that effectively shifts the line it uses, so that you get a more accurate AMSL altitude reading Setting QNH to 996 (< ), shifts the line and reduces the reported altitude

Pressure Height To determine your pressure height you can set your altimeter to a QNH of hPa or you can do some simple math –alt P = alt + (1013 – QNH)x30 –See Example 11-1 page 341 When you are preparing for a flight, you should do your computations before you are actually sitting in the aircraft, so you must know how to do the math Remember –If QNH actual elevation –If QNH > , pressure height < actual elevation

Density Height Density is a function of pressure and temperature –From the Ideal Gas Law, PV = nRT –Rewriting this as P/RT = n/V n/V is a density-like term, how much stuff in a given volume Most aeroplane performance parameters are a function of density –Lift = C L x 0.5 x  x V 2 x S There are several methods for determining the density height –Performance Charts –Simple math –Navigation Computer In this class we will only discuss the simple math method

Simple Math Step 1: Find Pressure Altitude –alt P = alt + (1013 – QNH)x30 Step 2: Find ISA temp –T ISA = 15 – 2x(alt P /1000) Step 3: Compare ISA temp and actual temp –  Temp = T act - T ISA Step 4: Find Density Altitude –alt  = alt P + 120*  Temp

Factors affecting TO performance Weight –As weight increases, TODR increases Density Altitude –As density altitude increases, TODR increases Humidity –As humidity increases, TODR increases Wind –A tailwind will increase TODR –A headwind will decrease TODR –A crosswind will slightly increase TODR Runway Surface –As friction increases, TODR increases Runway Slope –Up slope increases TODR –Down slope decreases TODR

Aeroplane Landing Performance Landing Distance –See Figure 11-7 page 338 –Starts from 50 ft AGL –Assumes: Approach speed of 1.3V S Full-flap Idle power Maximum braking Landing Charts will state the flap setting and approach speed to be used –See Figure page 352 and Figure page 353 The Charts often include a factor of safety, which is also listed

Landing Distance Available Portion of runway area suitable for the ground landing of an aeroplane –Established by “competent authority” When planning you must make certain that the available distance will meet the requirements of your aircraft

Landing Distance Required Weight –As weight increases, LDR increases Density Altitude –As density altitude increases, LDR increases Wind –A tailwind will increase LDR –A headwind will decrease LDR Runway Surface –As friction increases, LDR decreases Runway Slope –Up slope decreases LDR –Down slope increases LDR

Landing Charts Be sure to use the flap setting and approach speed indicated on the chart you select The climb requirement is due to the possibility that you will need to perform a go-around Be prepared for variations –Landings often take place long after initial flight preparations Winds can change Fuel predictions may be far off

For next week… Required Reading: –BAK Chapter 12, pp –VFG IN-FLIGHT, pp