Pilot Rules of Thumb

 I just blitzed my CPL NAV exam. With some very helpful Little tips I learnt that really saved me time in the exam, So I have decided to share these with you as they are gold:-)

Pilots of yester year, pre, during and post, of the great wars never had the luxuries we have today. Pilots, co Pilots, Engineers and Navigators all worked as a team. Today 1 pilot can do all of these jobs.

With the increasing rate of technology, modern aviation is becoming nothing short of Amazing! A brand new Cessna 172 can be equipped with as much avionics as a jet liner, full glass cockpits giving the pilot superior information with primary flight displays and Multi function display showing full color moving maps, engine parameters and more. Even if you had a 30 year old aircraft, you can still get a powerful hand held Garmin GPS that will enhance your situational awareness and do all your calculations. All you have to do is fly the plane. Sounds good to me.

This got me thinking, If we are relying on all this technology, How did pilots of yester year do it? Well in my hunt for the answer I found 2 little books "the pilot's pocket handbook" and "the pilots rules of thumb"

These two little books can be purchased from Amazon. COM, just search for "Pilots Rules of Thumbs" and "Pilots pocket Handbook". They literally slide into your pocket. You would be amazed at how some complex calculations that require a flight computer can be quickly calculated in your head within seconds!!  I am definitely not a math lover but I sound very smart when I can calculate an answer before any one of my friends with there flight computers.

 Example: How do you calculate your TAS? Simple, True Airspeed increases 2% over indicated Airspeed (IAS) for each 1,000' above sea level.

RULE OF THUMB: TAS = IAS + (2%) IAS X altitude/1000

Example Altitude = 6,000' MSL
           Indicated Airspeed = 100KIAS

           2% X 6 = 12 knots
           100 KTS + 12kts = 112 KTAS

How easy is that? Of course the answer will differ slightly due to density and temperature changes but it is still very accurate,to within + or - 2-3 kts, Try it!

When I did my PPL I was asked how to calculate the crosswind component of a runway. To be honest I didn't know, And I was never shown a crosswind component table. Which is what my testing officer helped me to solve. However I have found (due to this little book) a much much faster way of calculating both your X wind component and headwind component. Now this is a trick that you can beat your mates at a bar and win!

Faster than a flight computer, Faster than a crosswind chart, you can do this in your head!

RULE OF THUMB: To determine the crosswind component multiply the wind speed by the sine of the angle to the runway. (Sound hard? It's easy!)

Example:        Runway 16
                Wind 130 deg @ 20 kts
                Angle to Runway = 30 deg
                Sine of 30 deg = .5
                .5 X 20 = 10 knots crosswind component:)
To determine the sine of an angle, simply drop the zero, add 2 and move the decimal over one place to the left. (30 becomes 3 + 2 = 5 add decimal .5)

 
RULE OF THUMB: To determine the headwind/tailwind component, multiply the wind speed by the cosine of the wind angle to the runway.

Example:        Runway =16
                Wind =140 deg @ 29kts
                Angle to Runway = 20 deg
                Cosine 20deg = .9
                20kts X .9 = 18 knots headwind

To quickly find the cosine of an angle, use the sine of the supplement (the angle to which added = 90deg)

Example"        Cosine 20deg = Sine 70deg (70 + 20 = 90)
                Sine 70 = 7 + 2 = 9 ( move the .) = .9
                Sine 70 = Cosine 20 = .9

This takes a little practice, but I can assure you, you will pick it up quickly and become a Genius Pilot, or so every one will think you are anyway, LOL

Density altitude:
How about this 1, Can you calculate density altitude in your head? It's easy. 1st you need to know the pressure altitude, this can be easily solved by subtracting 1013 from the local QNH x 30 and add to your field elevation or altitude. Lets say we calculated a pressure height of 2000'. Now It's important to note that density height is really pressure height adjusted for temperature and you should be familiar with ISA T's & P's.

So we multiply 2000' x 2 = 4000', drop the zeros to get 4. then subtract 4 from the ISA 15deg c =12deg c. Subtract 12 from the actual temp (say it's +22deg c outside) 22-12=10deg c. Multiply 10 by 120  = 1200 + the pressure height we worked out as 2000' = 3200' density height! How easy was that?

Note* (temperature changes of +/- 1deg c will produce a increase or decrease equivalent of 120' density height) which is why we multiply our ISA temp deviation by 120.*

These are just 3 examples from hundreds in these 2 little books. If you can empower yourself with these rules of thumb than you will be a better pilot.

Happy flying.