Rules of thumb - nifty little guide

[VBHB 298]

http://www.flightsim.../rule-of-thumb/Good little guide that provides us with quick ways in working out our Aviation math. It's easy to forget these things and get lazy with the wonder advances in technology that comes with planes these days.Also has other guides about Aviation which is interesting and increases knowledge (especially for a non RL pilot like myself).Enjoy!Pete Walsh.

[Benji 3]

Nice one Pete! very useful!Thanks

[Alaaar 34]

Thank you so much Pete, that is very intersting

[kevinh 409]

I've not looked at many but the first two I read were flawed.How to convert knots to mph is given as:Multiply knots by 1.15That's not a rule of thumb, you might as well use a calculator. How about this instead, which is a rule of thumb:Add 10%, then add half the same again.i.e. 300 knots = 300+30+15 = 345 mphWorse, the calculation for time to travel distance based on ground speed is plain wrong. Also it only "works" for one TAS. The rule gives 57 minutes to fly 360 mm at 450 kts TAS. In fact it should take:360/450 = 0.8 hours or 48 minutes.Time = distance / speed is simple enough.No doubt there are some useful rules of thumb but be aware it has errors.Kevin Hall

[BlakeWilliams 6]

Nice! Thanks for the link!

[MorsAbAlto 19]

I've not looked at many but the first two I read were flawed.How to convert knots to mph is given as:Multiply knots by 1.15That's not a rule of thumb, you might as well use a calculator. How about this instead, which is a rule of thumb:Add 10%, then add half the same again.i.e. 300 knots = 300+30+15 = 345 mph

Isn't "multiply by 1.15" the same thing as saying "add 10% and then half the same again" but shorter?Thanks for the link. Bookmarked it.

[ronzie 21]

Here's another Rules Of Thumb source:http://www.b737.org.uk/rulesofthumb.htm

[kevinh 409]

Isn't "multiply by 1.15" the same thing as saying "add 10% and then half the same again" but shorter?Thanks for the link. Bookmarked it.

Can you easily multiply by 1.15 in your head? Probably not, but you can easily add 10% and then half that again.A conversion formula which needs a calculator is not a rule of thumb.The second "rule" was simply wrong.Kevin Hall

[MorsAbAlto 19]

Can you easily multiply by 1.15 in your head? Probably not, but you can easily add 10% and then half that again.A conversion formula which needs a calculator is not a rule of thumb.The second "rule" was simply wrong.Kevin Hall

Kevin,actually that's how I would multiply by 1.15. Writing it out as a sentence doesn't change the mathematical operations required to solve the equation, or does it? Who needs a calculator for stuff like this?I get your point, a rule should to be written out in a sentence. But it's really not necessary in this case IMHO. It's already as easy as it gets. If you can't solve this one in your head quickly you probably shouldn't be allowed to fly.Here is something that I think qualifies for a formula vs. a rule of thumb:I sound like a wisenheimer, but multiplying by 1.15 shouldn't be hard for anybody who finished high school.

[Danielsen 14]

Nice one! Instantly bookmarked

[XPX64man 130]

Thank you for the links. I'll bookmark them

[3-2-1-Now 126]

Rules of thumb can be a long way out. Use with caution. A simple calculator with trigonometric functions is all you need and/or an E-6B, and beats rule-of-thumb any day.

If you can't solve this one in your head quickly you probably shouldn't be allowed to fly.

Without referring to anything, what is 463 kph in kts? Those who fly the Russian birds should be quick with this one. :) "It's easy when you know the answer". ;)Best regards,Robin.

[Lukas_Mathijsen 41]

250 IIRC :D

[VBHB 298]

It's for simulator use only, relax professors...Pete Walsh.

[leppakot 0]

Very nice link indeed, thank you very much!

I've not looked at many but the first two I read were flawed.How to convert knots to mph is given as:Multiply knots by 1.15That's not a rule of thumb, you might as well use a calculator. How about this instead, which is a rule of thumb:Add 10%, then add half the same again.i.e. 300 knots = 300+30+15 = 345 mphWorse, the calculation for time to travel distance based on ground speed is plain wrong. Also it only "works" for one TAS. The rule gives 57 minutes to fly 360 mm at 450 kts TAS. In fact it should take:360/450 = 0.8 hours or 48 minutes.Time = distance / speed is simple enough.No doubt there are some useful rules of thumb but be aware it has errors.Kevin Hall

For me there is huge difference between multiplying by 1.15 or adding 10% and half of it again.. I think last one is much simplier =)I agree that there is major error in explanation concerning "time to travel distance based on ground speed", I think it is meant to be done as follows for example distance 150 nm:150/10=15; 15/3=5; 15+5=20 minutes(150/450=0,333 hours or 20 minutes)So it gives rough estimate of needed time to travel distance along ground with one specific GS (450 kts). Correct me if im wrong but isn´t it GS (wind component included) which must be 450kts for this to work not TAS (wind component not included)? Tapio LeppäkoskiFinland