Units of Measure:
- Statute Mile: the same as a standard mile as you would see driving a car
- Nautical Mile: defined as one minute of arc along a meridian of the Earth. Using the widely accepted WGS84 ellipsoid model, this averages a nautical mile to 6,076 feet (1,852 meters), or 1.15 statute miles
Temperature Conversion:
- The U.S. is used to operating on the Fahrenheit scale for day to day life but aviation standard is Celsius
Formula:
- °C = [(°F - 32) x 5/9]
- °F = [(°C x 9/5) + 32]
Example:
- 70°F day
Calculate:
- °C = ((70°F-32) x 5/9)
- You should come out with 21.1°C
Chart
[Figure 1]- Start at your initial temperature on the Fahrenheit scale
- Move across until you hit the reference line
- Move down and read the temperature off of the bottom
- In this example it comes out to be roughly 22°C
Table:
[Figure 2]- Find the temperature you need and read across the appropriate column
- Notice this table is more designed for Celsius to Fahrenheit but we still come out just over 21°C
Crosswind Component:
- MOVED! See more about crosswinds on the crosswind landing page
Short Field Takeoff Performance:
- MOVED! See more about short field takeoff performance on the Short Field Takeoff page
Load Factor:
- MOVED! See more about crosswinds on the Accelerated Stalls page
Stall Speed Banked:
- MOVED! See more about crosswinds on the Accelerated Stalls page
True Vs. Magnetic North Course Conversion:
- Used primarily for flight planning when converting a chart (always true north) to a course to fly in the aircraft (magnetic north)
Formula:
- "East is least, west is best"
- Magnetic Course (MC) = True Course (TC) - East Variation
- Magnetic Course (MC) = True Course (TC) + West Variation
Example:
- True course is 270°
- Variation is 14° east
Calculate:
- MC = 270° - 14°
- MC = 256°
Mach Number:
- Most high-speed aircraft are limited to a maximum Mach number at which they can fly
- This is shown on a Machmeter as a decimal fraction
Formula:
- Mach Number = Aircraft Speed/Speed of Sound (dependent on altitude)
Example:
- Aircraft is flying at 30,000'
- Speed of sound at 30,000' = 589.4 knots
- The airspeed is 489.3 knots
Calculate:
- 489.3/589.5 = 0.83 Mach
AerospaceWeb.org. Mach 1 vs. Altitude
Pressure Altitude:
- As altitude increases pressure will decrease in a standard atmosphere
Formula:
- Pressure Altitude = [(29.92 - current baro) * 1000] + Current field elevation
Example:
- Current baro: 29.82
- Field elevation: 500'
Calculate:
- 29.92-29.82 = .10
- 0.10 * 1000 = 100'
- 100' + 500' = 600'
Chart:
[Figure 4]- Using the chart on the right of the graph, look for the current altimeter setting
- To the right of it there will be an altitude in feet, and that is your conversion
Pressure/Density Altitude Conversion Chart
Density Altitude:
- Pressure altitude corrected for non-standard temperature
- Used for performance calculations
Formula:
- Pressure Altitude + (120 x [Outside Air Temperature (OAT) - (ISA Temp)])
Example:
- Pressure Altitude = 600' (as calculated above)
- OAT: 10°C
Calculate:
- ISA Temp (using standard Lapse rate of -2 degrees C per 1000 ft) is 14° C
- 600' + [120 * (10-14)]
- 600' + (-480) = 120'
Chart:
[Figure 4]- From the temperature on the bottom move up to your pressure altitude
- Next move left and read your density altitude off the scale
- Other tools are available to help you calculate density altitude such as Pilot Friend's Density Altitude Calculator
Cloud Bases:
- Used for VFR planning or when icing is a concern
- This is a very rough formula as cloud bases are not always flat and can change rapidly
Formula:
- Temperature-Dew Point (°C) divided by 2 = Base of clouds
- Temperature-Dew Point (°F) divided by 4 = Base of clouds
Example:
- Temperature: 10°C / 50°F
- Dew Point: 5 °C / 41°F
Calculate:
- (10-5) ÷ 2 = 2,500' MSL
- (50-41) ÷ 4 = 2,250' MSL
60 to 1 Rule:
- One degree of course change will put you 1 NM off course after 60 NMs
Climb Rate Required:
- Used to determine rate of climb for a given departure/climb out
Formula:
- Ground Speed (GS) (knots) ÷ 60 * Climb Gradient (Feet Per Mile)
Example:
- Ground Speed = 75 knots
- Climb Gradient Required = 200 feet per mile
Calculate:
- 75 ÷ 60 * 200 = 280 feet per minute climb rate required
Maneuvering Speed:
- Also referred to Va
- More weight = more stable
Formula:
Example:
- Follow instructions given on section 6 of the POH
Maneuvering Speed Formula
True Airspeed:
- MOVED! See more about crosswinds on the Airspeed Indicator page
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Top of Climb:
- MOVED! See more about crosswinds on the Flight Planning page
Time to Travel Using a Whiz Wheel:
- Point the black arrow to match the expected ground speed
- Look for the distance to travel on the outer wheel
- Read time immediately below (inner scale) the number representing distance
Ground Speed on Whiz Wheel:
- Line up distance over time (outer wheel over inner)
- Find the big black arrow, it is pointing to your ground speed
- Note that you will travel 10% of your speed in 6 minutes (6 min * 10 = 60 minutes)
Fuel on Whiz Wheel:
- Point the big black arrow to the pounds per hour (burn rate)
- Read time off the inner wheel
- Look above time to get pounds burned in that time
Conclusion:
- Many calculations are rules of thumb that are constantly handy
- Reference material such as the: Pilot's Pocket Handbook: Flight Calculations, Weather Decoder, Aviation Acronyms, Charts and Checklists, Pilot Memory Aids
and Pilot's rules of thumb: Rules of thumb, easy aviation math, handy formulas, quick tips
can come in handy