Tuesday, December 27, 2016

Aviation Wind correction calculations

In the Early 80's, I was lucky to have become a Private Pilot.  Lucky, because initially, I was hired as a mechanic / technician for a fleet of aircrafts in a CESSNA Pilot center.  My job was to maintain the 5 airplanes of our fleet (2 Cessna 152; a 172; a 177; a 210 turbo). I quickly became a bother to center's instructor, when I asked him every time to test fly one of the planes I had just worked on.  So, to remedy to the problem, the owner had me get my Private Pilot License.  My first instructor was a retired veteran of the French Air Force. The man was awesome. With his mentoring I was able to land a 152 in the numbers of a runway. My 2nd instructor, was a civilian with great skill and knowledge.  He trained me for the practice of the IFR rating.  His methods of calculating Wind corrections for flight in level and Approach is what I am about to share today.  He taught me as if we had no calculator, nor trig. tables. The 80's were the start of the fancy Trig calculators, and Trig tables of course were available. But his method was much faster.

No calculator, nor Trig. Table are used.

Pre-flight
Navigation Log
Nav. Log

  1. Check Aircraft airworthiness.
  2. Plot your course and record it on your Nav. Log.
  3. Check NOTAM's.
  4. Get Meteorological info for the flight.
  5. Update your Nav. log for Wind and other new info.
  6. Aircraft's pre-flight check.

Plot your Course

In our example, we are flying from location A to location B, as shown on the drawing below.
Empirical Trigonometry. Click for Full Size Image.
  • Course: 090 deg.
  • Aircraft cruising Speed: 120 knots
  • Check Points, etc...

Update Nav. Log: Calculating True Course and Ground Speed.

What we know (3), and what to update (3).

  • Course: 090 deg.
  • Aircraft Speed: 120 knots
  • Winds in flight: from 130 deg. at 30 knots
  • Wind Correction Adjustment: __________
  • Corrected Heading: _________
  • Ground Speed during flight: ________

Order of Calculations

  1. Measure the Angle between Course and Wind direction.  In our example, we measure an angle of 40 deg.
  2. Empirical Method. Calculate the SIN of the angle 𝛂 . Using the formula: (𝛂 + 20) / 100. In our example, SIN ð›‚ = 0.6.  Also, in this Empirical method, the Sum of SIN + COS = 1.3
  3. We can now calculate the Cross Wind component vector Force.  Wind Speed x SIN 𝛂 = 30 x 0.6 = 18 kts. (Will be used for Drift Correction calculation.)
  4. Now the Headwind component to define our Ground Speed. Using the Empirical method: COS 𝛂 = 1.3 - 0.6 = 0.7 . Headwind = 30 kts x 0.7 = 21 kts .
  5. Ground Speed =  120 kts - 21 kts = 99 knots (99 Nautical Miles per hour).
  6. Wind Correction. Convert Nautical Miles per Hour into NM's per Minute: 120 kts / 60 minutes = 2 NM's per minute.  Drift = Cross Wind / NM's per minute = 18 / 2 = 9 .
  7. Corrected Heading. Since the Wind is coming from the right, we will turn the nose of the aircraft into the wind by 9 degrees. We are heading due East, therefore: 90 + 9 = 99, that is our NEW Corrected Heading.

If the Winds were to change in flight, NO BIG DEAL! Do a quick recalc.

Now we Update (3)

  • Wind Correction Adjustment: +9
  • Corrected Heading: 099 deg.
  • Ground Speed during flight: 99 Knots (or 99 Nautical Miles per Hour)
The same method can be used on Approach to a Runway, at night or with low visibility. Adjusting the aircraft power to achieve a desired Ground speed, for ease of approach is also commonly done.

For those that are not too well learned in Aviation and Trigonometry, this very well made Video below.


Flying on Earth, the 3 basic gyroscopic instruments that keep us on course and in level flight.

In 1983, I started working for Maxair Aircraft Corp., an Ultralight aircraft manufacturing company.
See below a few videos that I filmed myself. Credits to Phil Lockwood (at the time, Marketing Manager & pilot), Denis Franklin (Owner).


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