Mental maths - tips, tricks and shortcuts [Archive]

Jabawocky

17th Dec 2011, 23:07

Learn how to manipulate numbers and groups of numbers in your head.

For example 85 USG of fuel, how many L and KG?

Start with 85 x4 so that is 170 plus another 170 which is 340. Now we all know that it's about 3.778 not 4 so that is less 5% roughly. So that is less 10%/2 or 34/2 which is 17. Answer is 323 litres. Now doing it accurately it works out at 321.76, so in flight doing a mental check is 323 close enough?:ok:

Now we want kg, well 0.71 kg to the litre, ahhh near enough to 30% less and we had 323, but let's allow a tad mor so use 330 to account for the bit more than 0.70 vs 0.71 and we get 10% of 330 being 33, so three of them is 99 and that means 231kg. Or from 323 it would be 226kg.

Now doing it accurately I get 228.45kg, so how close is 231 or 226kg.:ok:

So the secret is knowing the formulae or conversion constants, and then just being good at manipulating the numbers in easy chunks. Knowing what to add or subtract and doing so.

I am blessed with good mental maths and the ability to also know what is near enough and what is wrong. Too many kids today can't do this and they have no clue if hey come up with a wrong number. That is the scary bit.

Mental maths is great, but it must be matched with knowing what looks right and wrong.

I hope that helps answer your question. As for the useful tricks like descent profiles such as distance times 3 (in hundreds feet) add 100 etc is something others here will have good tricks for.

Chimbu Chuck is a classic one for them.

VH-XXX

17th Dec 2011, 23:42

Minutes to decimals .6 - I've never had a reason to use this except for sometimes when I have to pay for the aircraft after the flight.

Fratemate

18th Dec 2011, 02:55

The one I use a lot is the 'clock face' for approximating crosswinds, drift angles etc:

The clock obviously has 60 minutes and you use the proportion of those minutes to estimate the % of the crosswind etc. I know, crap explanation :) So, I'll try harder. The wind is 30 degs off the runway at 20 knots. Take those 30 degs and pretend they're minutes on our clock face. 30 minutes is 1/2 (50%) of the face, so the crosswind component is about 10 knots. Another: wind is 20 degrees off the runway at 15 kts. 20 degs = 20 minutes = 1/3 of the clock face, therefore 1/3 of 15; crosswind is 5 kts. This works all the way up to around 40-45 degs; thereafter just take the whole lot. So a wind 50 degs off the runway at 10 kts will be 10 kts of crosswind.

Add in a 'max drift' calc and we can sort out all our nav problems. Max drift is the wind speed divided by our TAS in miles/min(or IAS if you're low down......these are approximates, not absolutes :)) SO; we're in our Cessna and we're bimbling along at 120 kts. 120 kts/60 = 2 miles/min. We've got a wind speed of 30 kts at our cruising level, so max drift (i.e. if it was all across) would be 15 degs. Now we apply our clock face: wind is 15 degs off our track. 15 degs = 15 minutes = 1/4 of the clock. Max drift is 15 degs (piss poor example eh), so our drift angle is 4ish degs (1/4 of 15), so head 4 degs into wind. Another, I hear you cry: TAS 180 (3 miles/min). Wind is 60 kts, therefore max drift is 60/3 = 20 degs. Wind is 40 degs off our track. 40 degs = 40 mins = 2/3 of the clock. 2/3 of 20......14 degs of drift.

We can also take that angle off our track of the wind, subtract it from 90 and apply the same calcs to work out our groundspeed. E.g: we've got 20 kts of wind at 60 degs off our nose. 90-60 = 30. 30 on the clock face = 1/2; so we've got 10 kts of headwind. Wind 30 degs off track at 10 kts: 90-30 = 60; therefore take the whole lot: we've got 10 kts headwind. Apply logically for tailwind.

Applying it all: wind is 330/20 at cruise and we're going to track 360 in our 120kt TAS Cessna. So, max drift is 10 degs (120/60 = 2 nms/min. 20/2 = 10). wind is 30 degs off track so hdg reqd is 355 (30 = 1/2 the clock. 1/2 of 10 = 5 degs.....apply in the correct sense!). Groundspeed is 100 kts (90-30 = 60. Apply the whole lot 'cos it's greater than 75% of the clock face, therefore, we've got 20 kts headwind). We land on our conveniently orientated runway 36 and the wind is now 320 at 15. We've got a 10 kts crosswind from the left (40 degs off = 2/3 of the clock = 2/3 of 15).

I haven't got a whizzwheel to hand but would be interested to hear how close they are. Now, back to the FMC :ok:

MakeItHappenCaptain

18th Dec 2011, 03:25

Another good tip is to
STOP USING FR:mad:GGIN' CALCULATORS IN FLIGHT!

It takes your attention away from the aircraft attitude while you concentrate on using tiny buttons and a miniscule display.

My students soon learn if a calculator comes out in flight it soon ends up in the baggage area behind the back seat.:E:E:E

The more you practise "mental gymnastics" the easier it gets.

Learn to use your whiz wheel (not just for time vs distance/fuel, but for multiplication and division as well). The dude who invented this thing was a certifiable genius!

Round numbers to make rough calcultions easier,
Eg. 4 miles off in 38 would be pretty close to 4:40, hence 6:60 or 6 degrees.:ok:

For cross and headwinds, I used
30 deg = 1/2 wind strength is x/wind
45 deg = 3/4 and
60 deg = 90%

Reverse the order for head/tail winds

30 deg = 90% head/tail wind
45 deg = 3/4 and
60 deg = 1/2.

At 60kts, 1 kt x/w = 1 deg drift
At 120 kts = 1/2 deg drift.
:ok:

rutan around

18th Dec 2011, 04:01

A good tip I was shown (after 20 years of flying) : A persons finger on a WAC chart covers near enough to 10 nm. Try it. 2 fingers 20nm 4 fingers 40nm etc You'll quickly work out for your own hand where it has to cross the track drawn on the chart to be surprisingly accurate.Very handy on a rough day bouncing around with no auto pilot.Wish I had been shown this for my pre GPS days. I still use for identifying items of interest that we see out the window from time to time.
Cheers RA

Capt Fathom

18th Dec 2011, 09:34

http://www.stefanv.com/aviation/flight_computers/cr.jpg

Jabawocky

18th Dec 2011, 10:10

But when MIHC chucks your calculator or whizz wheel (same thing really) into the back seat, maybe you might want to unstuff the brain maths.

Capt Fathom

18th Dec 2011, 10:17

That's why I carry two of them!:E

Doesn't anyone have a sense of humor anymore?

BoxBoxCheez

18th Dec 2011, 10:34

To nail a 3 degree glideslope, use RoD of 5 x groundspeed! (Because a 3 degree slope is a 5% gradient). Simple, but effective.

MakeItHappenCaptain

18th Dec 2011, 11:27

No, I don't mind a whiz wheel, really. You can hold it up, operate it with one hand and keep an eye on what's going on outside at the same time.
(Most students let go of the yoke (haven't quite worked out rudder to keep wings level yet, but that doesn't matter cause they're looking down anyhoo) and concentrate fully on a little half by 3 cm screen for the next two minutes.)

Mental maths first, double check with the whiz wheel.

Plus, no batteries to go flat.:E:ok:

JustJoinedToSearch

18th Dec 2011, 12:43

NIK320

18th Dec 2011, 13:37

Top of descent for a 500ft/min descent.
Thousands of feet to loose x twice the GS in nm/min.

Descent from 9000 to 3000 at 180kts.
dropping 6000ft and covering 3nm per minute so 6 x 6 = 36nm.

To prove it works.
36nm @ 3nm/min = 12 mins.
12 mins x 500ft/min = 6000ft.

4000ft at 120kts = 4 x 4 = 16nm
16nm @ 2nm/min = 8 mins
8 mins x 500 ft/min = 4000ft.

GS is a multiple of 2 so easy enough to use either 120kts, 150kts or 180kts.
+/- 10kts, adjust by 3nm as appropriate.

greybeard

18th Dec 2011, 14:19

RTFQ = 1/2TFA

Works for me

You must have a ball park figure at all times as man's index finger on the keyboard causes more strife than the middle one used to do.

:ok:

kalavo

18th Dec 2011, 14:58

Fratemate's clock code works well.

Rather than dividing and multiplying all over the place having one simple number to remember. I use 0.284 to get litres of Jet per side... ie I need 500 lbs of fuel x 0.284 = 145 litres a side.

Time on target can be useful as well... 10 seconds late requires a 10 knot increase for (normal cruise speed) seconds (so if normal cruise speed was 240kts, and you were 10 seconds late, you need to do 250kts for 4 minutes to make up the lost time).

Remembering 3x height for profile can be rather hand for night circling as well, not just 60nm out.

Wally Mk2

18th Dec 2011, 20:07

Quick numbers checks using what some have mentioned here are fine under certain conditions but it would be very irresponsible of any pilot not to have a calculator at hand at all times. Under pressure or duress the brain can be very unreliable & simply wrong so always have two options for working out any calculations. Why else do we have such high levels of automation these days even in basic A/C, 'cause it takes the 'guess' work out of a lot of flying & that includes number crunching using the brain only.End result safer!
When I was taught to drive a plane everything revolved around a whiz wheel as well as being able to do simple maths in yr head but a calculator was always there close at hand.

Simply being alert at all times & having good situational awareness means brain number crunching is kept to a minimum.

Wmk2

knox

18th Dec 2011, 21:12

Here is an easy one. How many feet before leveling off from a climb or descent is required for attaining your target altitude. 10% of ROC eg climbing at 1000fpm you'd need to start leveling off 100' prior to target altitude.

The other one is at what point you require to start your turn onto an DME arc. 1% of GS eg 200kts x 1%=2nm (rate 1 turn)

Knox.

Kelly Slater

18th Dec 2011, 23:35

Reciprocal headings, add 200 minus 20 or vise versa or add 2 minus 2 to keep it simple.

150 add 200 = 350 minus 20 = 330
300 minus 200 = 100 plus 20 = 120

JustJoinedToSearch

19th Dec 2011, 04:51

One I use for percentages (especially multiples of 10%) is to divide by 10 and then multiply by whatever number you need to get the right percentage.

I.e. 20% of 20 = 20/5=4 nice and easy. but 20% of 17.8 I would find too hard to just divide by 5.

So I do 17.8/10= 1.78 (10%) x2= 3.56.

Works for multiples of 5% as well. you just do the same thing to the 10% level below and then add half of the original figure.

I.e. 35% of 56= 5.6x3=16.8 (30%) + 2.8 (half of 10%)=19.6.

Arm out the window

19th Dec 2011, 06:03

Or you can round a bit to make it easier -

35% of 56:

Do 35% of 60, which is 3 and a half times 6, ie 21. Take a little bit off because 56 is a bit less than 60, call the answer 20.

Or to be slightly more scientific, 35% of 60 is 21.
56 is 4 less than 60, or about 6% less (two-thirds of 10%).
So my answer should also be two-thirds of 10% less, or 21 minus 1.4, which is 19.6.

ForkTailedDrKiller

19th Dec 2011, 07:01

Ooooooooooooooh! My head hurts just reading this thread!

I am with the Captain on this one.

Dr :8

zlin77

19th Dec 2011, 07:10

The ideal woman is half your age plus seven years....very useful after getting an airline command and going through divorce..!

Capt Fathom

19th Dec 2011, 09:55

Reciprocal headings, add 200 minus 20 or vise versa or add 2 minus 2 to keep it simple

150 add 200 = 350 minus 20 = 330
300 minus 200 = 100 plus 20 = 120

That is simple??

What's wrong with.....

150+180=330 and 300-180=120! :confused:

Some of these work-arounds are more complicated than the original!

MakeItHappenCaptain

19th Dec 2011, 10:23

Sorry, Wally.

Gotta disagree here (partially).
I am seeing WAY too much of students that can't even do simple addition without a calculator. The overreliance on this automation is the problem. Don't laugh, but I have actually seen finger counting to add two single digit numbers.
WHAT THE F:mad:CK??!!??:ugh::mad::bored:

Not saying everyone finds multiplying two double digit numbers easy, but practise and using unfcukupable tools are a starting point.
Did I mention practise?
Does anyone notice how when they first learned to drive a car, they had to really work on clutch & gear coordination, parking, hill starts etc...? Notice how it gets easier with time?
Because you practise! Being able to get these answers without having to take your socks off has gotta make things easier when your workload has gone ballistic.:ok:

Not trying to drift the thread here, but seeing similar things with many AFR navexs where GPS has taken over.

Xcel

19th Dec 2011, 11:04

Always laughed at the time to decimal place card in the cockpit. Till I used it a few times... Oh how quickly we build reliance on something.

Seriously 0.1= 6 mins IS easy, but after 16 hr split duty have to confess, out comes the app, calculator and socks off...

Gone back to refusing to use tools and cards for simple arithmetic and low and behold, I can figure stoof out again. Amazing!

Even to the point that ops staff were simply amazed when I figured out the fuel in kg just by taking off 20%... wow no fms, calculator, app, whiz wheel or toes required.

So best tip, trick and shortcut? Put down the calculator! Pick up the pen!

NIK320

19th Dec 2011, 11:30

Then pen works fine until you forget to carry a 1 and cause a mess as a result.

Then you get back to technology to fill out the occurrence report which will no doubt be an online form.

There is a reason technology has become such a reliance in aviation. Not such a problem calculating a 1:60 in a GA aircraft.. your visual and can probably get close enough to see the destination.

Doing the math mentally, getting it wrong and not loading enough fuel in the 767 will land you in Gimli.

Mr.Buzzy

19th Dec 2011, 18:59

I just love the idea that reading little numbers on an electronic calculator is bad airmanship. Apparently reading smaller numbers on a whizz wheel is not!

Get with the times, encourage common sense, if someone is fast and safe using any technique, then rather than "throwing stuff into the baggage hold" take some notes yourself, you might learn something!

Bbbbbbbbbbbbbbbzzzzzzzzbzbzbzzzzzzbzzbzzz

Move On

19th Dec 2011, 19:35

Got to agree on mental maths.

Make it Happen Captain, agree with the mental stuff and whizz wheel at student level/flying school ops, however outside of GA, the calculator is your best pal.

Example..

If you do 8 sectors there is a "Deck log/ Flight log" to be filled out for each sector and it has to be crunched quickly, as the turn around can be 30 mins.. These compile of converting pounds to kg- litres to kg- minutes to dec. points, along with other calculations.

A calculator is a must, No guestimations here. It is also stated in Part B/SOP's, that a calculator is to be used for the Deck logs/MEL's.

ANOTHER THING GUYS/GIRLS.....GENERATION Y ARE A DIFFERENT BREED WITH REGARDS TO TECHNOLOGY....CALCULATORS RULE FOR THEM. I notice some here mentioned "batteries"....geez you must be a baby boomer or Gen x....:rolleyes: Solar power and battery combination along with pocket size/ compact units that fit right in your right pocket of your shirt,if you lose it, there is also a iPhone....

Anyhow, as mentioned still got to love mental maths for TOD points... Oops, the FMC does it for me....:ok:

b_sta

19th Dec 2011, 21:55

Checkboard

19th Dec 2011, 22:15

I like that a thread about mental arithmetic shortcuts has been hijacked into whether you are a hero for liking them or not!

QSK?

19th Dec 2011, 22:25

Years ago when I was in the old CAA, I was checking out a new (young) guy for a rating on a certain sector. One aircraft this guy was responsible for was tracking between two reporting points that were 119 nm apart and the pilot's ETI for the route segment was 60 mins. Casually I ask the guy I was checking what was the pilot's approximate groundspeed.

To my surprise he reaches for a calculator! I still shake my head at that one.

Surely there must still be a need for some mental maths ability!

Arm out the window

19th Dec 2011, 23:54

There'll always be a place for it.

I like new technology that makes life easier, but I don't think I've ever owned or used an electronic device that didn't malfunction in some way at some time.

Knowing you can deal with loss of gear (GPS being the most notable one these days I think) without totally losing the plot is good.

Plus, it's just good airmanship to be able to check if the automation is telling you bull****, be it because of equipment or operator failure, or both.

MyNameIsIs

19th Dec 2011, 23:54

Jeez, and I thought mental maths was supposed to make things simpler and easier... some of the stuff in this thread makes my brain hurt :ugh:

Clock code for xwind, TOD, RoD etc., sure, but fuel conversions, planning etc., I'll stick with a calculator thanks - why make things harder than they have to be??

I use my head for fuel quite a lot- but its more for the 'get an idea' rather than gospel.

Its not that hard to remember that 100lbs of JetA is almost 60 litres.
For example if i want 500lbs ill be ordering about 300 litres, and if its been ordered for me if all of a sudden i saw 400l or 200l I know something somewhere isnt quite right for whatever reason.

That's not "harder than they have to be". It's actually quicker than removing calc/phone from pocket and punching in 500 / 1.76 = into it!

Sure we arent trying to sin/cos/tan angles or anything like that so some things are irrelevant, but mental maths is very useful to dummy-check figures in all aspects of flying or at least get a rough estimate to get things going and work out an absolute later.

sisemen

20th Dec 2011, 00:36

To my surprise he reaches for a calculator! I still shake my head at that one.

Undergoing a check. Stressed (some people react badly to check rides). Momentary brain fade.

I suspect that afterwards, when calmed down, there would have been a forehead slapping moment in private.

But, of course, you've never been in that situation have you? I just LOVE empathetic examiners :*

rutan around

20th Dec 2011, 06:09

Sorry-I can't help myself. I always do a rough mental calculation to assure myself that the box of silicon chips probably gave me the correct answer. It's too easy to hit for example the x button when you really meant to divide. So if I'm adding 256 L of Avgas and I need to calculate the added weight I mentally note it should be less than 256kg but more than half of 256kg. I then multiply 256 by 0.7 and arrive at 179.2 so it's probably correct. If I arrive at 365.7 I know I've made a mistake,in this case divided instead of multiplying.
Two more handy rule of thumbs.
For 75% power use the rule of 48. MP in Inches plus RPM hundreds will be pretty close to 75% power if they total 48 eg 24 inches MP plus 24 hundred revs is about 75% power so is 23plus 25 or 21 plus 27
For TAS use 2% of the IAS X altitude in thousands and then add this result to the IAS
eg Indicating 135 knots @ 9500 feet you get 2% of 135 = 2.7 X 9.5 = 25.65 plus 135 =160.65 knots. This doesn't allow for temperature effects but it's pretty close to right.
Cheers RA

QSK?

20th Dec 2011, 23:02

sisemen:But, of course, you've never been in that situation have you? I just LOVE empathetic examiners Don't fret sisemen, the young guy still passed the check OK because, despite using the calculator, he still gave me the correct answer and, apart from that, I also appreciated he was under some level of stress at the time due to a heavy sector workload and the fact that he was being checked. He performed well given all the circumstances, so I WAS EMPATHETIC.

But you're right there was a forehead slapping moment after the event.

helloimindelaware

30th Dec 2012, 13:08

General Aviation Mind Tricks (http://www.gamindtricks.com/)

Short PDF book with a few mental maths shortcuts

AileronsNeutral

30th Dec 2012, 23:00

To nail a 3 degree glideslope, use RoD of 5 x groundspeed! (Because a 3 degree slope is a 5% gradient). Simple, but effective.Why multiply by 5 when you can divide by 2?

Capn Bloggs

30th Dec 2012, 23:07

Why multiply by 5 when you can divide by 2?
My method of choice. :ok:
(Not forgetting to x 10, of course! :})

Zoomy

31st Dec 2012, 02:05

Does anyone notice how when they first learned to drive a car, they had to really work on clutch & gear coordination, parking, hill starts etc...? I also noticed that as my cars progressed they got easier and easier to drive. Not because of my practice, but because of power steering, AWD, ABS, rear camera, ect ect ect.

Use a calculalor if you must. Use a wizz wheel if you must. Use your brain if you must.

Whatever you do. Do not get caught up in 15th century training methods.

Capt Fathom

31st Dec 2012, 02:15

15th century training methods

Zoomy. I'm afraid you'll have to remind me what those methods were. The 15th century is a bit hazy....even for me!

Zoomy

1st Jan 2013, 05:56

You know, remember the abacus.

All of the training I received in GA, was pedagogical. It was mainly teacher centered with the learner being a passive receiver. Information flowed one way and all the learning activities in the class room were rigid sequences.
Adults, (usually socially accepted as 18+ give or take a few years in some), learn in a completely different way. In fact it has been proven that some children learn in an andragogical learning environment.

Adults learn best when new information is linked to past experience, we all know that. But adults also like to take part in the learning path and have some form of input into the sequence.

If a student presents with a calculator, so be it. This is a result of the present. They are widely used in schools and kids grow up with them. If you want to ween them off, do so nicely. There is absolutely no need to throw the thing in the hat shelf and tell the student off. Perhaps show them the mental arithmetic techniques as the present themselves.

Some of the rhetoric on here regarding a students inability to calculate simple sums, just tells me the instructor has no patience for the job at hand.

MakeItHappenCaptain

1st Jan 2013, 11:09

OK, Zoomy,

I also noticed that as my cars progressed they got easier and easier to drive. Not because of my practice, but because of power steering, AWD, ABS, rear camera, ect ect ect.

What an unmitigated heap of steaming crap. How does your argument hold up when driving a base model Hyundai (ie. no power steering, AWD, ABS, rear camera etc etc etc). Spose your spelling is another example of near enough good enough, eh?:E It got easier because you practised and used the skills. Same thing happens with mental arithmatic.
According to your logic, what's next? A licence based on age of the aircraft? Or an "easy to fly" licence vs a "hard" category?

I spend a significant amount of time explaining how to use a whiz wheel. I don't even charge when showing them some of the more advanced uses, such as multiplication and division. I show them alternatives to calculators as a means of cross checking flight planning. Divide the number by 10 and add half of that again to give 15%, a quick way to check variable fuel reserve as well as using a calculator for flight planning.

I explain to the student, regardless of their age, 18 or 48, why it is not a good idea to be using a device that sucks your attention into a tiny screen and funnily enough, not many older students have a problem with mental maths. People's skills have just gone rusty over the last 20 years, they haven't gotten dumber. (Maybe lazier, though.)

If the student continues to sneak calculators (even as far as onto their flight test, with the ATO quoting their head being inside the cockpit for so long as the biggest single reason they couldn't hold a heading or altitude, despite having flown the previous five navs without it no drama), I will continue to force them to use other methods and I do so with the full support of EVERY CFI I have flown under.

You know of a CFI who is happy to use calculators without any further effort, post their school up here, but only if you want to ensure their graduates don't find work, because I for one would be very cautious if I saw that particular school on a resume.

Continued reliance on a calculator will not, contrary to your babying, help a student, especially in the middle of a NVFR or IFR exercise with no autopilot. I have yet to see an ATO who prefers to see a calculator in a cockpit. Furthermore, if you are content with the ability and dedication of a pilot flying your family around commercially (or privately) who needs to take off their shoes and socks to add, then standards have hit rock bottom and started digging. I, however, refuse to promote this level of mediocrity.:cool:

Some of the "rhetoric here" is a result of
a) incredulous belief that students will refuse to make the effort to improve to the standard required of a professional pilot; and
b) "instructors" that are happy to accept this problem because it is "a result of the present".

I expect that level of complacency from hour building instructors, not anyone who is genuinely interested in producing the highest possible standard of pilot.:=

Not saying every student is a mental genius, but I will make the effort to help them if they want to help themselves. :ok:

Zoomy

1st Jan 2013, 20:48

What an unmitigated heap of steaming crap.Whos a bit sore this morning.

Get A LIFE Mate.

Oh and as for the spelling, I forgot to use spell check.

standard required of a professional pilotOh and I would like to know, what is your standard of a professional pilot. What do you call professional? The way you conduct yourself on here and sending other pruners intimidating and threatening PMs,, shows me your true professionalism.

Tidbinbilla

1st Jan 2013, 21:03

If you wish to carry on like a bunch of school children - you will be treated as such.

Dash8capt

1st Jan 2013, 21:18

Why it is not a good idea to be using a device that sucks your attention into a tiny screen
Used an FMS lately :}
This forum outlines the race to the bottom out industry faces.... If we can't get along in here we are doomed sitting 30cm away from each other in the pointy end, and even worse come EBA time.

lilflyboy262...2

1st Jan 2013, 21:41

How is using a calculator any different to looking down at a map? Hell you can even hold the calculator up in front of your face if you have to.

I always round things up to make things easier to calculate. For fuel. 100lbs of Jet is around 54L. I round it up to 60L and work that out. Once you start taking bigger orders of fuel such as, for example, 1000lbs. For every 100lbs of fuel, you get 6 extra L. 6 x 10 = 60, 600 - 60 = 540L for 1000lbs. (I use this as an example, obviously if its 54L per 100lbs, for 1000lbs you just need to add an extra 0.)

ROD for glide slope is half your ground speed then add a 0 at the end.

My other options are a) Engage Captain Auto if I am single pilot and use a calculator. Or b) Get my F/o to either fly, or do the calculations.

psycho joe

2nd Jan 2013, 00:41

I just love the way that we Australians, in this industry are anal about the really important stuff like whether someone who uses a wizz wheel has higher moral ground than someone who uses a calculator, and whether someone who uses neither can claim themselves victorious.

Well I sneer upon you loathsome, dare I say unsafe masses, as I claim moral superiority; you see I have a wiz wheel on my over-sized Pilot watch which trumps you all.

As if my overt strutting wasn't enough, one glance at my watch by all and sundry, tells the great unwashed that I am a Pilot without having to actually say a word. This coupled with Ray-bans at a bar lets all those in "visual contact" make no mistake. I use words like "aircraft" instead of "plane" and extol the virtues of hand flying and make anti- automation comments whenever possible to mask my fear of it and the fact that I'm not really sure of what it all does.

Sometimes on a long flight I like to turn everything off and hand-fly my jet based on nothing more than memorised maps, pure skill and my trusty watch wizz wheel; usually after announcing "watch this". The fact that I can do this whilst complaining about Y gen (of which I am not) and randomly ranting about the government, single mothers, Airline management etc asserts my authority and prowess in the cockpit.

As for mental math tricks:

Multiplying by 5, 25, or 125

Multiplying by 5 is just multiplying by 10 and then dividing by 2. Note: To multiply by 10 just add a 0 to the end of the number.

12x5 = (12x10)/2 = 120/2 = 60.

Another example: 64x5 = 640/2 = 320.

And, 4286x5 = 42860/2 = 21430.

To multiply by 25 you multiply by 100 (just add two 0's to the end of the number) then divide by 4, since 100 = 25x4. Note: to divide by 4 you can just divide by 2 twice, since 2x2 = 4.

64x25 = 6400/4 = 3200/2 = 1600.

58x25 = 5800/4 = 2900/2 = 1450.

To multiply by 125, you multiply by 1000 then divide by 8 since 8x125 = 1000. Notice that 8 = 2x2x2. So, to divide by 1000 add three 0's to the number and divide by 2 three times.

32x125 = 32000/8 = 16000/4 = 8000/2 = 4000.

48x125 = 48000/8 = 24000/4 = 12000/2 = 6000.

lilflyboy262...2

2nd Jan 2013, 03:06

^^^^ :D:D:D:D

On an every day operational basis, the only quick mental math I have to do is the Glideslope ROD. And thats about it.

Oh and ToD depending on which plane I use. Unpressurised. 500ft per minute is not a hard one.
Altitude x3 or x2 for pressurised aircraft.

GPS are now installed in pretty much every aircraft. And if not, DME is also there.

MakeItHappenCaptain

2nd Jan 2013, 07:41

To all, I will publicly apologise for letting my "enthusiasm" for the topic get away from me lately.:ouch:
I have always admitted when I was wrong, but while I have been presenting my view with (too much) gusto, I still firmly believe in what I am saying and the principles behind it.
I was taught this way, have seen many different techniques, and don't believe that the aircraft most people are progressing into for their first "standard" GA job have changed over the last 20 years much. Still C210s with a few more GA8s maybe, so IMO, the techniques still apply.

Zoomy,
sending other pruners threatening and intimidating PMs
That is an out and out lie.
I have been known to send PM's to people apologising for undeserved public comments, but I do not use PMs to threaten. You may disagree with what I say, and it is my right to do so with your argument, but I do not behave as you are accusing and am more than happy for a moderator to look into the accusation, as I would do if someone threatened me.:cool:

Lickher Licence

2nd Jan 2013, 10:13

Safe to say that MIHC is certainly passionate about what he teaches! A rare trait among most instructors these days.

In my earlier training days, my instructor thought that flying wasn't hard enough so he used to get me to count my 7,8, or 9 times tables backwards. Sounds easy, but try it during steep turns, if you don't get to 0, start again!
Call me a nerd but I loved those flights (and the challenge)
The reason why cars and flying machines are fitted with all these fancy bells and whistles is for one main objective, SAFETY.
I've made errors calculating my TOD before using my brain, how many times has my pocket calculator made them? 0. But a solid understanding and a mental check of the math confirms that.
Math is a requirement for all facets of flying.
Use all tools that are available in the cockpit, car or Segway:} to get you and your passengers safely to the destination.
I personally enjoy the challenge of using my noggin for calculations. But I'm not going to judge someone who doesn't enjoy maths as much as I!

Counter-rotation

3rd Jan 2013, 06:47

A good thing to know is that:

100 fpm = 1 knot (roughly). (It comes from the fact that there's about 6000 ft in a nautical mile...)

This can help with calculating required climb RATES to meet missed approach obstacle clearance, as one example.

ie:
Vyse = 120 kts.
You need to make 2.5% gradient.
What RATE of climb (what the performance charts often speak about, and what the instrument tells you) do you / will you require?

2.5% of 120 is 3 kts.
So that's about 300 fpm...

Also,
2 knots = 1 metre per second
ie. halve the number on your ASI (convert to TAS first if significant) to know your speed in mps.

This stuff really should be taught. Maybe it is.

CR.

Capt Fathom

3rd Jan 2013, 10:33

Metres Per Second.... WTF ? Do I need to know that?

And I thought Psycho Joe's post was mind numbing!

:ugh:

djpil

3rd Jan 2013, 10:37

A competition aerobatic box is 1000 m square so it is essential for us to know the conversion from kts to m/sec.

compressor stall

3rd Jan 2013, 11:05

I've made errors calculating my TOD before using my brain, how many times has my pocket calculator made them? 0. But a solid understanding and a mental check of the math confirms that.

Hmm, I've watched students use a calculator and get an answer one order of magnitude out.....

A mental check takes as much effort as rounding and getting the answer in the first place. And if you round the numbers (for most calculations that's all you need for aviation accuracy) and think about your process, you get that added gut feeling of reasonableness to boot.

The shortcuts as described here are not really that hard. Personally, I think anyone who doesn't [want to] learn them is just lazy and unprofessional.

Capt Fathom

Metres Per second.... WTF? Do I need to know that?Flown overseas recently?

Slasher

17th Feb 2013, 06:03

TAS (nm per min) x crab angle = crosswind comp.

You can juggle too - Crab Angle = crosswind comp / TAS nm per min.

X/W or H/W....

30* - 90% reported
45* - 75%
60* - 50%

I still use my Jepp wizzwheel but only very rarely these days - mainly
in the sim when poofteenths matter. I'm not against the Magenta kids
using a calculator but only if it doesn't take too long and they aren't in
control (ie PNF).

Metres Per second.... WTF? Do I need to know that?

Flying a 3.3* profile decent and that 1m happens to equal 3.28 ft gives
the dist required to BOD. Helps if you have an altimeter reading metres
though. More applicable to us international jocks.

Roger Greendeck

17th Feb 2013, 20:31

Interesting variation on the the automation debate. I like to think about it the same way. If the aircraft has it you should be able to use it. If your have high end automation then you should be able to operate it quickly and accurately but be able to hand fly it just as well.

Having been forced by my instructors to be able to do mental DR I am eternally grateful. There is a time and place for a calculator (mainly flight logs where accuracy counts and you have time to go heads down) but mental DR is pretty handy. The FMS is not always right and not every approach can be fully programmed to touchdown so the VNAV requires some mental backup. Thanksto my instructors who insisted on mental gross error checks my occasional cock ups have not ended in tears.