3:1 rule works pretty well the rare times I need to use it in the modern jet age.Descent I use altitude to lose times three and groundspeed times five a lot. And if groundspeed times five is too hard for my pea brain I just cut the groundspeed in half and add a zero. (500 knots / 2 = 250 + 0 = 2500 feet per minute)
So altitude to lose times three gives me distance from a certain point to start a descent. And the groundspeed math gives rate of descent required.
Crosswind components - if the wind is 60° from centerline it’s all crosswind (so 10 knots of wind you have 10 knots of crosswind) and at 30° from centerline it’s half (10 knots of wind is now 5 knots of crosswind). From there just interpolate a little.
Temperature conversion - Temperature in C, double it, take away 10% and add 32. 10° C * 2 is 20° take away 10% = 18° + 32° is 50°F. (If you use an iPad, the spotlight search from your Home Screen will do temperature conversions without an internet connection. Just type 15c to F and it will show you.)
1. Don't hit nothing!Let’s collect all the aviation rules of thumb we can think of here, show that they’re reasonably correct, then post them in a GitHub repository or something for posterity!
That's a good one.“We need 6000#”
6000 - last “0” = 600
600/2 = 300
300 + 600 = 900gal of fuel.
(9000 x 6.7 = 6030)
I’ve only ever needed that up to 30k but it works.
Doesnt mean you'll land on it...If you can see the airport, you can't run out of gas.
Prove me wrong
@bLizZuE took the main ones I was thinking of...here's a couple more...
- "12 and 12" - an EMB-145 - if you're at 1200fpm descent by 12,000 feet, you'll be under 250 at 10,000
If I remember correctly, this worked at any 1Xk altitude with the thrust levers at idle.
I.e. 1900fpm from FL190, all the way to 1100fpm at 11,000.
I remember back in the pre gps, GA days I had all sorts of sectional measurements on my hand. Length from the last joint of my finger to the tip, width of my palm, pinky tip to thumb tip spread out.@bLizZuE took the main ones I was thinking of...here's a couple more...
- "12 and 12" - an EMB-145 - if you're at 1200fpm descent by 12,000 feet, you'll be under 250 at 10,000
- Pax generally tolerate a 500fpm (cabin) or (non-pressurized) descent rate pretty well.
- Turn 20, Twist 20 on a DME arc works really well on most GA airplanes....if the arc is 10nm or more
- Putting the nose on the horizon on TO usually results in Vy on most airplanes (again, piston GA but I hear it's true of jets)
- The width of the knuckles of your first two fingers - edge to edge - are about 10nm on a sectional, and 5nm on a TAC
- On an approach, 300' increase in altitude per 1 NM from the runway gives you a good 3-degree glide slope...so, 3NM = 1500, 4NM = 2000, 5 NM = 2500, etc...
fun 737 NG fact, if your Autothrottles are inop, set your fuel flow to get your airspeed at altitude.
IE- if you set 2.8 per side, you'll get ~280 KIAS.... etc...