Aviation Calculations

Preflight planning is a very important element of any flight and especially so when going on a cross country flight. There are a number of items to be done in preparation for a VFR cross country in such a way that nothing is overlooked and the intended flight is done as safely as possible.

The pilot will perform a number of calculations during preflight planning and the one we used on the site are listed below for convenient access. Sometimes the use of a special aviation calculator (E6B models or electronic Jeppesen) is required other times it can be done without the use of such devices.

Formulas In Aviation

As a reference, we compiled a list of formulas we used throughout the site:

Flight planning

   Compass heading: TC +/-WCA = TH +/-VAR = MH +/-DEV = CH

   Estimated Time Enroute (ETE): Time = Distance/Speed

   Weight shift problems: distance weight shifted × weight shifted = total weight × Change of C of G

   Track Error (1 in 60 rule): TE = (60 / distance flown ) * distance from track

   Closing Angle (1 in 60 rule): CA = (60 / distance to go) * distance from track

Aerodynamics

   Load factor: G = 1 / cos(bank angle) or G = L / W

   Higher stall speed in a turn: Vsacc = Vs × √ load factor

   Increased stall speed at higher weight: Vs new = Vs old weight × √(new weight / old weight)

   Lift formula: L = ½ ρ V² × S × C_L or simplified Lift = IAS × C_L

   Dynamic pressure (IAS): ½ ρ V²

   True Airspeed (TAS): TAS = IAS × √ (ρ0 / ρ)

   Propeller efficiency: Thrust × TAS / Brake Horse Power

   Propeller tip speed (π is PI, 3.1415...): V_TIP = π d N

Aircraft performance

   Pressure Lapse Rate: PLR = 96 × ( T in kelvin) / local pressure (in hPa)

   Pressure Altitude: Pressure Altitude = Altitude + (1013 - QNH) × 27

   Density Altitude: Density Altitude = Pressure Altitude + (OAT - ISA_Tpa) × 120

   Specific Air Range (SAR): SAR = (TAS / power) × (1 / SFC)

   Specific Ground Range (SGR): GS / fuel flow or GS / power

   Best Specific Fuel Consumption (SFC): SFC = TAS / power

Physics

   Kinetic energy: E = ½ m v²

   Speed of sound: 331,3 √ (1 + T / 273,15)

   Ideal gas law: p × V = n × R × T

   Force: F = m × a

   Work: W = Force × Distance

   Power or the rate of doing work: Power = Work / Time

Engines

   Engine power (π is PI, 3.1415...): BHP = ((2 π × RPM) / 60) × Torque

   Engine efficiency: Brake Thermal Efficiency = Brake Power / Fuel Consumption

   Engine SFC: Brake Specific Fuel Consumption = Fuel Flow / Brake Power

Electronics

   Light power, luminous flux: 1 lm = cd.sr

   Ohms law: U = I × R

   Electrical power: P = U × I

   VHF Communications range: Range = 1,33 (√H-aircraft + √H-gs)