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Equations 

Equations, formulas, and other rule of thumbs

Formula
Equation
Notes
Mach number
TAS(True airspeed)/LSS(Local speed of sound)
Local speed of sound
Speed of sound (kts)= 38,94 * √T (Kelvin)
Lift
Lift = ½ρv²SCᴸ
Cᴸ= Coefficient of lift
Pressure altitude (PA)
Elevation + (1013 - QNH) (27) or Elevation + 1000 x (29.92 - altimeter setting)
QNH = Forecasted or reported pressure value
Density altitude (DA)
Pressure altitude + (OAT - ISA deviation) (120)
OAT = Outside air temperature & ISA = International standard atmosphere
Crosswind
Wind speed x sin wind angle
Headwind
Wind speed x cos wind angle
Rate one turn
3°/second
180° in one minute
G-force
1/cos (bank angle)
Magnetic bearing
Magnetic heading + Relative bearing = Magnetic bearing
Rotation speed VR
VS x 1.15
VS = Stall speed
Manouvre stall speed
VS x √n or VS x √1/cosα
VS = Stall speed
Moment
Weight x arm
C.G in % MAC
CG distance aft of LEMAC/MAC
LEMAC: Leading edge mean aerodynamic chord
Center of gravity
Total moment/Total weight
Tire hydroplaning speed
9 √ tire pressure(psi)
Radio range formula
R = 1.25√HT + √HR
HT = Height of transmitter, HR = Height of receiver
Equal time point (distance)
ETP = (Total distance x inbound groundspeed)/(outbound groundspeed x inbound groundspeed)
Equal time point (time)
ETP distance/outbound groundpseed
Point of no return (distance)
Total endurance x (Outbound groundspeed x Return groundspeed)/(Outbound groundspeed/Return groundspeed)
Point of no return (time)
PNR distance / outbound groundspeed
Point of safe return (distance)
Endurance minus reserve x (Outbound groundspeed x Return groundspeed)/(Outbound groundspeed/Return groundspeed)
Point of safe return (time)
PSR distance / outbound groundspeed

Radio navigation instruments, their frequencies, and range

RNAV frequencies.png

Other rule of thumbs and useful info

Emergency frequencies
VHF 121.5, UHF 243, ELT 406
Squawk code for communications failure
7600
Squawk code for emergencies
7700
Squawk code for hijack
7500
Are winds in relation to magnetic or true north?
Both. Forecasted winds are true, reported winds are magnetic
Windsock
Each segment represent 3kts of wind
Over the threshold
At the threshold, 1/2 LOC dot = 1/2 runway width
Aircraft weight
10% of aircraft weight change will result in 20% change in take-off distance
Abort take-off
If 70% of takeoff speed is not acheived within 50% of runway
Takeoff distance for general aviation
You need to reach at least 70% of take-off speed by 50% of runway distance
For max TAS and range
Load airplane as close to the aft CG limit as allowable
VOR range (NM)
1.23 x √Altitude in feet
A tailwind of 10% of your approach speed
increase landing distance by 20%
A headwind of 10% of your approach speed
decreases landing distance by 20%
A 10% change in airspeed
causes 20% increase/decrease in stopping distance
1000ft in field elevation
changes landing distance by 4%
A narrow runway…
seems longer on approach
A wider runway…
seems shorter on approach
A narrow and uplsoping runway
creates an illusion that the aircraft seems higher on approach
A wide and downsloping runway
creates an illusion that the aircraft seems lower on approach
A wet runway
Increases landing distance by 50%
Land on the 1st 1/3 of runway
Or go around
Loss of 50% of thrust in a twin engine
Approx 80% loss of ROC
10 - 25 degrees add more lift than drag
25 - 40 degrees add more drag than lift
Having a forward CG…
aircraft more stable and stall at higher speed
Having an aft CG…
aircraft less stable and stall at a lower airspeed
Structural icing occurs usually in the range
0 - 10 degrees
Mountain flying
Actual horizon is base of mountain
Mountain flying
Stay on the updraft side of the canyon
Mountain flying
Approach mountain ridges at 45 degrees
Approximate AOA before stall
18 degrees (For most airfoils)
Glide ratio
A glide ratio of 17:1 means that the aircraft will travel 17000 ft distance for each 1000 ft altitude loss

Disclaimer: These rules of thumbs are not intended to be exact or precise! Use them for your information or at your own discretion

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