Just a few I remember off the top of my head, which I use IRL, and in the sim too. I’ll add more if I remember more!
Takeoff/Climb Performance Rules of Thumb
1. The 50/70 Rule
If you haven’t reached 70% of your takeoff speed by the time you’ve covered 50% of the runway length, abort your takeoff!
2. The Density Altitude Rule
The density altitude at an airport changes by 120 feet for every degree in variation from standard temperature (ISA, which is 15ºC or 59ºF at sea level). Density altitude increases with increase in temperature, and decreases with a decrease in temperature.In a formula: Density altitude = Pressure Altitude + 120 (Outside Air Temp - Standard Air Temp)
3. The Standard Adiabatic Lapse Rate
Standard temperature (ISA), which is 15ºC or 59ºF at sea level, decreases by 2º for every 1000 feet in altitude.
4. The Climb Rate Rule or Ft/NM to Ft/Min Rule
When you have a climb gradient in feet per NM (as most SIDs do), to get it in feet per minute, which is a more accessible format, divide your groundspeed by 60 and multiply it by the given climb gradient in ft/NM. In a formula: FPM = (GS / 60) x FPNM
5. The Cruise Climb Speed Rule
The best cruise-climb speed is the difference between Vx (best angle of climb speed) and Vy (best rate of climb speed), which is then added to Vy. In a formula: Cruise Climb Speed = Vy + (Vx - Vy)
Enroute Flight Rules of Thumb
1. The 1 in 60 Rule
When you’re 60 NM out from a VOR tracking station 1º of offset = 1 NM (note: on a VOR, a full-scale deflection on either side = 10º so each dot = 2º)
So if you’re off track, you can find out by how much, assuming you have a constant heading. The formula is: (No. of degrees off course x Distance to station) / 60
2. Standard Rate Of Turn
To calculate a standard rate of turn, divide the airspeed by 10, then add half the result to the total number. In a formula:
Step 1: Airspeed / 10 = blahblah
Step 2: blahblah + 0.5blahblah = Standard ROT
Apologies, I hate using the ‘standard’ variables such as x, y, a, b etc.
Approach/Landing Rules of Thumb
1. The Top Of Descent Rule, or Rule of Three
Calculate a rough top-of-descent by the 3 to 1 rule. You travel 3 NM for every 1000 feet lost. In a simple formula: Top of Descent = (Altitude/1000) x 3
2. The 3º Glideslope Rule
To calculate a 3º glideslope, which comes in handy when you’re on an ILS approach, divide your groundspeed by 2 and add a 0 to the end of the result to get your vertical speed. For example, if your groundspeed is 130kts, 130/2 = 75, then add a zero, that’s 750 feet per minute. Bonus: an ILS is 4 times more sensitive than a VOR. So while a full scale deflection of the needle on a VOR indicates a 10º offset, on an ILS it’s 2.5º
3. The Gusty Approach Rule
If you’re flying a gusty approach, add half of the gust factor to your approach speed. If your approach speed is 145 KIAS and the winds are gusting 20 knots, keep your approach at 145 + (20/2) = 155 KIAS