# Aviation Calculations, Formulas

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 × CL or simplified Lift = IAS × CL

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...): VTIP = 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 - ISATpa) × 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)

### Written by EAI.

WHERE TO GO NEXT?

SITE SECTIONS: LIBRARY - NEWS - FLIGHT PLANNING - WEATHER - REGULATIONS - HOMEBUILT AIRCRAFT

QUICK WEATHER ACCESS: TAF-METAR & NOTAMs