Equations

Equations, formulas, and other rule of thumbs

Formula	Equation	Notes
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

Other rule of thumbs and useful info

Emergency frequencies	VHF 121.5, UHF 243, ELT 406
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

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