As @abelenky points out in his comment, it is the Mean Aerodynamic Chord of the wing. This is not exactly the mathematic mean of the wings' chord, but a size which includes the damping effect of a pitching wing which scales with the square of its chord. The% part just shows that this length is given as a percentage of the mean aerodynamic chord. Next, you need a location for this length unit. This can be the actual MAC location of the wing, other aircraft use the leading edge of the wing root as the lengthwise zero point. All measure distances in their, positive backwards.
The airplane manual should give an exact definition how to measure the correct CG location. If the actual CG location falls within the range given by both numbers, you are safe to go.
Jan 6, 2014 - Is it just a way to tart up a name, by sticking 'Mc' or a 'Mac' in front of it? Or does adding that little prefix actually mean something?history,. Random Mac Factoid: According to the 1977 U.S. Social Security Administration data, the first name Mac is not a popular baby boy's name in California. Imagine that, only 7 babies in California have the same name as you in 1977.
If the CG is forward of the smaller number, your control authority might not be sufficient, the pitch control forces will be too heavy for comfort and both your rotation speed and your stall speed go up. If the CG is aft of the bigger number, your static stability is too small or the airplane might even be unstable. Also, pitch control forces will be very low so you run the risk of damaging the aircraft with too large control inputs. A document said that the optimum CG position is from 13% MAC to 33% MAC.
A possibly better phrasing of that statement is that the 'allowable CG position is.' Or some such. Typically the term 'optimum CG position' is used not for a range but for a given CG position that optimizes whatever you wish to optimize. Usually for transport category aircraft it's used to refer to the target zero fuel weight CG that produces the best fuel economy. As it happens, the range 13% MAC to 33% MAC are typical landing CG limits of 747s as well as the zero fuel, taxi and takeoff limits at low weights.
An often used value for the optimum zero fuel weight target for best fuel economy is 26.6% MAC. Forward of that value would mean you'd burn more fuel, aft of the value you'd burn less fuel but would be starting to have undesirable effects that outweigh the fuel economy.
![What What](/uploads/1/2/4/3/124370199/611651885.png)
If you wish to see a graphical display of such limits, go to, select any aircraft, and when the aircraft page comes up, scroll down to the OPERATING ENVELOPES at the bottom of the page. If desired you can add fuel and cargo and see how it affects the CG.
Updated: by Computer Hope MAC may refer to any of the following: 1. Short for medium access control, or MAC address. Known as a physical address and hardware address whose number is uniquely formatted in format and given to each computer or network device on a computer network. The addresses are usually assigned by the hardware manufacturer, and these ID's are considered burned into the of the network access hardware. Because of this process, some vendors use their own specific code in the hardware address. Below is an example of a MAC address. D4-BE-D9-8D-46-9A Because a MAC address is a unique address, a computer network will not have the same MAC address assigned to more than one computer or network device.