BACKGROUND
3.4.2.5. The Coriolis effect The Coriolis effect is the tendency for any moving body on or above the earth's surface to drift sideways from its course because of the earth's rotational direction
(west to east) and speed, which is greater for a surface point near the equator than towards the poles.
In the Northern Hemisphere the drift is to the right of the body’s motion; in the Southern Hemisphere, it is to the left.
The Coriolis deflection is therefore related to the motion of the object, the motion of the Earth, and the latitude. The Coriolis acceleration results in an increase or decrease of the apparent aircraft gross weight.
.GW .6
=.7.63×10 ×GS×sin(TT) × cos(LAT)
GW
Where GW is the aircraft gross weight
GS is the ground speed in knots
TT is the true track
LAT is the latitude
At a given ground speed and latitude,
.
In the Northern Hemisphere, the aircraft gross weight increases when flying westwards and decreases when flying eastwards.
.
In the Southern Hemisphere, the aircraft gross weight decreases when flying westwards and increases when flying eastwards.
In order to account for the gross weight deviation, a positive correction when the aircraft is flying westwards and negative correction when the aircraft is flying eastwards (in Northern Hemisphere, and vice versa in the Southern Hemisphere) could be applied to the specific range.
.SR
The correction is applied on the as follows:
SR
. .SR . .Cd .Cl .GW
. .= =+k × =+k ×
. SR .CORR Cd Cl GW
where k is a function of the drag and lift coefficients.
Flight Operations & Line Assistance Getting to Grips with Aircraft Performance Monitoring
BACKGROUND
Hence,
. .SR ..6
. .=.k ×7.63×10 ×GS×sin(TT) ×cos(LAT)
SR
..CORR
Where GS is the ground speed in knots
TT is the true track
LAT is the latitude
3.4.3. Technical factors
3.4.3.1. Fuel Lower Heating Value (Fuel LHV)
The Fuel LHV defines the fuel specific heat or heat capacity of the fuel. The usual unit for this parameter is BTU/LB.
Fuel flow is directly impacted by this value. The effect of the fuel LHV on the apparent cruise performance level is explained below thanks to a basic reminder of the operation of a gas-turbine engine.
The engines are required to produce a certain amount of thrust (i.e. a N1/EPR thrust setting parameter is required) to maintain the aircraft in steady cruise level flight. For given flight conditions, a given engine provides an amount of thrust, which depends on the amount of heat energy coming from the fuel burning in the combustion chamber.
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