Rules of Thumb

[Rocketier]

Hi fellow aviators I would like to know all your rule of thumb info. It seems that whilst training there is a lot of maths etc, which then you have to use the wiz wheel for. Only to find out when talking to more experienced pilots there is a rule of thumb for that which could be easier.Can we all share our Rule of Thumb info? no matter how small it is just jot it down.

[Nibbler]

Crosswind - the simple (on final) mental calculation

Split the watch face into 4 quarters - 1 to 3 = 1/4, 3 to 6 = 1/2, over 6 = full crosswind

Wind 10-30 deg off runway is in the first 1/4 - take 1/4 of wind as crosswind
Wind 30-60 deg off runway is in the second quarter - take 1/2 of wind as crosswind
Wind 60 deg + take all of wind as crosswind

[Duchess_Driver]

From your knuckle to the tip - how long is your thumb?

On an average spread - how wide is your hand from thumb to little finger?

It helps with diversion planning whilst in the air.

[beatnik]

Even simpler, and more accurate, than the previous reply, take the number of degrees the wind is off the runway heading, divide by 10, then divide by 6. The crosswind is that fraction of the wind strength.

So if Rwy is 020 and wind is 040/12k, then wind is 20 degrees right of rwy heading. So 2/6 of 12k = 4kts xwind from the right

Example: Same rwy and wind stength but the wind direction changes
Wind 020 -diff = 0, so 0/6 = no crosswind
Wind 030 - diff = 10, so 1/6 = 2kts
Wind 040 - diff = 20, so 2/6 = 1/3 = 4kts
Wind 050 - diff = 30, so 3/6 = 1/2 = 6kts
Wind 060 - diff = 40, so 4/6 = 2/3 = 8kts
Wind 070 - diff = 50, so 5/6 = 10kts
Wind 080 - diff = 60, 6/6 = 12kts Full crosswind component.

[MyNameIsIs]

If you think it looks dodgy, it probably is!

That goes to anything from paperwork to maintenance, to the state of the aircraft to the weather etc.

[Pilot DAR]

Chance of survival is inversly proportional to angle of arrival

[Pace]

RULES OF THUMB

Dont get your thumb in the way when hammering in nails :=

Another one? for your descent point multiply your altitude by 3 ie 30,000 just take the 30x 3= 90 miles or 9000 feet 9 x 3 = 27 miles out.:)

Pace

[BackPacker]

To obtain a three degree glideslope:

- Altitude in 1000' of feet times three is the distance to descend.
- Groundspeed in knots times five is the vertical speed required.

[trex450]

beatnik,

Wind 030 - diff = 10, so 1/6 = 2kts

dangerous one yours, a wind that is 30 deg off runway heading simply gives a crosswind component of half the wind speed. Your example gives a 2 kt crosswind when it should be 6. Mathematically it is the sin of the angle multiplied by the windspeed. Rules of thumb work but not this one.

Stick with the clock face and you can't go wrong. Failing that if it feels to strong it probably is.

[172driver]

- Groundspeed in knots times five is the vertical speed required.

In feet, one would hope :eek:

[mm_flynn]

beatnik,


dangerous one yours, a wind that is 30 deg off runway heading simply gives a crosswind component of half the wind speed. Your example gives a 2 kt crosswind when it should be 6. Mathematically it is the sin of the angle multiplied by the windspeed. Rules of thumb work but not this one.

Stick with the clock face and you can't go wrong. Failing that if it feels to strong it probably is.trex, you misread the table, Wind 30 on RWY 20 is 10 degrees off runway heading (not 30) - hence beatnick's result of 2 kts x-wind component.

[Halfbaked_Boy]

beatnik -

Thanks for that one, that's extremely useful! :ok:

edit - although wouldn't use it above about 50 degrees as it becomes very inaccurate, but up to that, very close to the sine values!

[BackPacker]

In feet, one would hope

Actually feet per minute.

although wouldn't use it above about 50 degrees as it becomes very inaccurate, but up to that, very close to the sine values!

Above 50 degrees you use the full wind strength for the x-wind component. That's actually very close to the sine values as well. In fact, you'll find that the inaccuracies of this method are less than the inaccuracies caused by the wind being variable, particularly in strong winds where it matters most.

[Pilot DAR]

Quote:
- Groundspeed in knots times five is the vertical speed required.
In feet, one would hope http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/eek.gif

Refer to post #6...

Also:

Nothing ever happens fast enough in aviation, unless something is going wrong...

[Halfbaked_Boy]

Cheers Backpacker, never considered an x-wind safety factor, unlike tailwinds and headwinds. Learn something new every day :ok:

[modelman]

Used to be the max thickness of branch you could legally beat the missus with!

[jonkil]

Fuel weight in KGS = 75% the volume...... not exactly but OK for calculations..
(eg) 100 litres fuel = 75KGS
80 litres fuel = 60KGS

[trex450]

mm flynn, thanks for that, sorry Beatnik I stand corrected.

[bjornhall]

One I use on almost every flight: Dependence on weight for approach speed, best glide speed, VX, VY, VA: The percentage change in speed is half the percentage change in weight.


Penetration speed: When gliding with a head wind, increase gliding speed by a quarter of the wind speed. When gliding with a tail wind, glide slightly slower, but never slower than the minimum sink speed.


IAS -> TAS: Two percent per 1,000 ft.


Crosswind correction: 1 knot crosswind per 1 degree correction, per 60 kts GS. E.g., 10 kt crosswind component at 120 kts GS requires 5 degrees correction.

[IO540]

Groundspeed in knots times five is the vertical speed required.

Where would one use that rule?

[Human Factor]

A 3 degree glideslope.

[Rocketier]

Hi all
Thanks for all your responses,

I have one for you, if its any use.

To quickly determine NM per minute, round your airspeed to the nearest 10, drop the zero and divide by 6.

Example TAS =178KTS = 180knots

Drop the zero and divide by 6:
18 divided by 6 = 3NM per minute:ok:

[Rocketier]

With regard Glide slope.
Another one is add a zero to your ground then half it.

IE: 50knts add 0 = 500 half it =250ft/min

what do you think?

[IO540]

A 3 degree glideslope

Why not track the glideslope as indicated by the glideslope indicator?

[dan1165]

Easier for GS

Your ground speed divided by 2 . ex : 150 KT gs , vs =750'/mn :cool:

[contrail]

Quote:
A 3 degree glideslope

Why not track the glideslope as indicated by the glideslope indicator?

During a Non Precision approach such as a VOR/DME Procedure with a promulgated 3 degree slope.

[IO540]

OK, I get that.

I just wondered how many NP approaches have their continuous descent alternative at exactly 3 degrees, while not having the pre-calculated FPM figures (for various GS values) shown on the chart.

[BackPacker]

To quickly determine NM per minute, round your airspeed to the nearest 10, drop the zero and divide by 6.

To determine the IQ of a random group of people, take the lowest IQ of the group, multiply by ten, add fifty, divide by ten, subtract five.:ok:

[flybymike]

Why not track the glideslope as indicated by the glideslope indicator?

Maybe it is just me, but surely you find it easier to "nominate" an initial rate of descent once the glideslope has been intercepted and thereafter to make adjustments to descent rate in order to maintain the slope , rather than simply charging up and down the sky hoping to recapture it?

Edit.. all so much easier on autopilot of course..

[Pilot DAR]

subtract five.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/thumbs.gif

People from the random group? or IQ points?

....You only have too much fuel when you are on fire....

[IO540]

Maybe it is just me, but surely you find it easier to "nominate" an initial rate of descent once the glideslope has been intercepted and thereafter to make adjustments to descent rate in order to maintain the slope , rather than simply charging up and down the sky hoping to recapture it?

Obviously one doesn't just "charge up and down the sky hoping...".

At the GS intercept, I drop the gear and select 1st stage flap. This gives me very close to the required -VS. And the aircraft remains trimmed as it was before. This is IMHO better than trimming in a hurry at the GS intercept.

I am sure others have different methods.

[MyNameIsIs]

Have heard that

"halve your groundspeed, multiply that by 10" will keep you pretty close to a 3deg slope.

also
5x your groundspeed = required ROD for a 3 degree approach.

the above are the same, just depends on how good you are at maths!!!

sorry if someone has mentioned it and i've missed it and am repeating!


DAR, you said "you only have too much fuel when you are on fire"...

.....or if you have a boss like mine that books too many people on a flight in the heaviest aircraft and you are already on min fuel and get an earbashing from them because you 'have too much and we havn't had this problem before'..... :ugh:

[DA-10mm]

300' above field elevation per ever mile on final will keep you outta trouble

@1 mile...300 AGL, 2 miles 600 AGL...so on and so forth

basic pilot stuff, works every time, no matter what airplane you're in, big or small...

[DA-10mm]

this has been totally abused on an earlier thread, for sure, but here we go...

can't use the runway behind you
can't use the altitude above you
the only time that you'll ever have too much fuel on board is when you're on fire...

git sum!
never jim-jam the flim-flam...

[worrab]

....You only have too much fuel when you are on fire....

... or with 2 rugby players in a C150

[flybymike]

300' above field elevation per ever mile on final will keep you outta trouble

@1 mile...300 AGL, 2 miles 600 AGL...so on and so forth

basic pilot stuff, works every time, no matter what airplane you're in, big or small...

But it doesnt work if you are making an approach to somewhere like Oban where there is an 1100ft mountain a mile from the threshold...

[Skylark58]

At single/light twin approach speeds, 100rpm or 1" of manifold pressure is worth about 100 fpm

[ExSp33db1rd]

Is anyone actually looking out of the window ?

My first Nav. instructor told me to stop doing a maths exam in a rattling steel cabinet. Same goes for flying the beast. KISS