Rules of thumb repository
- Thread starter ppragman
- Start date
Stone Cold
Well-Known Member
Two captains operating an airplane is a potential disaster.
There ya go. That’s a pretty official rule of thumb.
There ya go. That’s a pretty official rule of thumb.
bLizZuE
Calling for engine starts en français
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.)
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.)
poser765
Well-Known Member
3:1 rule works pretty well the rare times I need to use it in the modern jet age.
for temp conversions I make it even easier. Just double the temp in C and add an even 30. 10C. 10x2=20+30= 50. I’m a big fan of arithmetic with round numbers. Is it exact? No, but the people in back aren’t listening when I tell the temp anyway.
inigo88
Composite-lover
Code 7700 has some good rule of thumb threads:
1. Don't hit nothing!
2. Don't do nothing stupid!
Wardogg
Meat Popsicle
That's a good one.
I've always used. 1000lbs = 150 gal.
So for every 2000lbs I need 300 gal.
6000lbs I would just times that by 3. 900 gal.
killbilly
Vocals, Lyrics, Triangle, Washboard, Kittens
@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...
ahw01
Well-Known Member
Doesnt mean you'll land on it...
jmc4
Well-Known Member
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.
Slowing - in level flight at idle, 1 mile for every 10 knots. Add 5 miles if you have more than a light tailwind or are also descending.
killbilly
Vocals, Lyrics, Triangle, Washboard, Kittens
Yeah, they didn't teach us this - would've made some things easier. I picked this up from a pair of XJT people.\
poser765
Well-Known Member
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.
I've found the "12 and 12" works grear in all the jets I've flown: 145, Gulfstream, 757/767, and even the mighty Bus if you can get past the panic stare of the other pilot when you pull V/S. It's one of my favorite rules
In the 757/767 (or should I say the ER) a good one for single engine work is set as many units of rudder trim as the first number of the fuel flow on the good engine. 7,000 pph = 7 units of trim
In the 757/767 (or should I say the ER) a good one for single engine work is set as many units of rudder trim as the first number of the fuel flow on the good engine. 7,000 pph = 7 units of trim
SquatThrust
Well-Known Member
2000fpm with speed brakes at 12,000' (12,500 works a little better tho) will also get you to 250kts by 10k in the 145.
Crockrocket94
Well-Known Member
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...
IE- if you set 2.8 per side, you'll get ~280 KIAS.... etc...
///AMG
Well-Known Member
Where was this last month on a 3 leg day? I wont say I was smart enough to recognize this pattern, but I did learn a lot about hand flying this plane.
