Mean Aerodynamic Chord (MAC) - اسأل الطيار ask pilot


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Tuesday, April 21, 2020

Mean Aerodynamic Chord (MAC)

Mean Aerodynamic Chord (MAC)
%MAC (Percent Mean Aerodynamic Chord) is a mathematical calculation that shows where the center of gravity is over the wing. In simple form it describe as the average distance from the leading edge to the trailing edge of the wing.
The calculations is rather straight forward and the generic formula is the same for all airplanes. All one has to do is to figure out the numbers and plug them into the formula.
How is %MAC calculated?
Pilots, dispatchers or load masters will calculate the weight and balance with respect to the aircraft datum. Unfortunately, we need to change where the reference point is from the (datum) to the front of the wing called leading edge mean aerodynamic chord (LEMAC). There is also a trailing edge mean aerodynamic chord (TEMAC) that is calculated. TEMAC - LEMAC = Wing width.
LEMAC and TEMAC are easy to calculate for straight wing aircraft. It is simply the measurement from where the wing starts and ends from the datum. For swept-wing aircraft it isn't that simple. As a result, aerodynamic engineers figure out where the average of the LEMAC by averaging the wing root and wing tip. The same process happens for calculating TEMAC.
%MAC is simply a calculation of how far the CG is from the LEMAC. If the CG is at the LEMAC, we can say it is at 0% MAC. CG at TEMAC means the CG is at 100% MAC.
*Special Notes
(Formula: MAC = TEMAC – LEMAC )
TEMAC. Trailing edge of the mean aerodynamic chord. .
LEMAC. Leading edge of the mean aerodynamic chord. A reference point for measurements, and specified in inches from the datum to allow computations to relate percent MAC to the datum.
By Air.Net Team

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