Basic Rule of Thumb:
You won’t remember a rule of thumb unless you use it.
What are your most useful rules of thumb for flying?
I think that the only two that I use are:
1. Cross wind calculations
10 degrees = 1/6 of winds speed = cross wind component
20 degrees = 2/6 of winds speed = cross wind component
30 degrees = 3/6 of winds speed = cross wind component
…
60 degrees = 6/6 of winds speed = cross wind component
2. For the aircraft that I fly, I need 5nm per 1,000ft desent required, at 500fpm.
So if I need to lose 5000ft to destination, then I need 5*5nm = 25nm to desend.
I can’t off hand think of any others that I use.
As you say, if you don’t use it regularly, you won’t use it.
The most useful one I’ve learnt is for crosswinds:
Also (somehow this was missed in my PPL training):
Divide speed by 10 and you have distance in 6 minutes. Handy for a quick recliner for an estimate at a point when linked with….
500k chart, thumb tip is 10 miles
Descent planning distance start with required altitude change x 3… e.g take 3 miles for each 1000 ft
Standard decent.
Decent rate:
Multiply GS by 5 to get descent rate.
example: 150kt x 5 = 750 fpm.
Distance to start decent:
Multiply the altitude difference in thousands by 3.
Fl120 down to FL70 = 5kft x 3 = 15 miles. You should start the decent 15 miles out.
I use these rules on each and every flight.
The one-in-60 rule is the most useful one for me as it is applicable in many situations (e.g. wind correction, crosswind component…)
Also, start descent at 4* the altitude difference in 1000’s of feet.
From cruise to descent:
Reduction in RPM = rate of descent in FPM.
Works surprisingly well for a wide range of fixed prop aircraft.
Constant speed?
Reduction in inches MP = rate of descent in FPM / 100.
The most useful one I’ve learnt is for crosswinds:
•Wind less than 30 degrees off the runway heading: crosswind component is negligible
•30-60 degrees off: crosswind is about half the total wind
•More than 60 degrees off: crosswind component is the more or less the full wind speed
You better unlearn that quickly. At 30 degrees it is EXACTLY half, and at 60 degrees it is 86%.
Dublinpilot’s is much better – easiest remembered as “clock code”.
Two equally useful methods for wind corrections in the air:
The other one (which I prefer, as I like multiplication more than using the division implied in the “clock code”
Accuracy of all these is better than +-10% for most data points, only at 60 degrees it is around 15%, in any case more accurate than the wind forecast…
Density Altitude: every 8.3 degs C above ISA = 1000 ft increase. ISA of course is 15C minus field elevation in thousands of feet multiplied by two (2C being standard lapse rate).
Example: FE = 7000ft. OAT = 10C. ISA should be 1C. Difference = 9C. DA therefore approx 8100 ft.
This errs a bit on the high side, which is rather a good thing in practice.