Pay attention that this page is under construction.
Information inside can be read but shall not be taken as input for any exam or definite information.
The concept of weight and balance is critical in aviation industry. Compliance with the known limits is very important relating to the flight safety. Aircraft balance refers to the location of the center of gravity (CG) of an aircraft. Operation with CG outside the approved limits results in control difficulty.
Preflight planning should include a check of performance charts to determine if the aircraft's weight may contribute to hazardous flight operations.
The CG of a body is the theoretical point at which the entire weight of that body is assumed to be concentrated. In a airplane, the CG is a point at which the aircraft would balance if it were suspended atthat point.
The primary concern in balancing an aircraft is the fore and aft location of the CG along the longitudinal axis. The CG is not necessarily a fixed point. Its location depends on the distribution of weight in the aircraft. The distance between the forward and back limits for the position of the center for gravity or CG range is certified for an aircraft by the manufacturer.
On small airplanes and on helicopters, the CG location is identified as being a specific number of inches or millimeters from the datum and the CG range is identified the same way. On larger airplanes, the center of gravity and its range are typically identified in relation to the width of the wing (usually mean aerodynamic chord is used).
Each aircraft has a determed and precalculated weight and balance references and numbers. Basically speaking it looks like this:
The actual location of the CG can be altered by many variable factors and is usually controlled by the pilot:
Flying an aircraft that is out of balance can produce increased pilot fatigue with obvious effects on the safety and efficiency of flight. Adverse balance conditions affect flight characteristics in much the same manner as those mentioned for an excess weight condition. Stability and control are also affected by improper balance.
It is vital to comply with weight and balance limits established for all aircraft.
Let's take a look onto standard Cessna 152 weight and balance sheet and try to calculate weight and CG for different phases of flight.
Pilot weight: 160 lbs
Passenger weight: 140 lbs
Fuel required for flight: 15 gallons
Fuel consumption for flight: 7 gallons Baggage: 50 lbs.
Usually weight and balance sheet for general aviation consists of 2 parts: data table and CG graph (envelope). Our first step is to fill the table with actual data.
1. Fill the table with weight data.
Use the conditions from above to fill the table and calculate total weight.
2. Calculate the moments.
* Multiply each weight that was entered by its corresponding arm from the "Arm" column and put the result in the "Moment" column.
3. Verify the numbers.
Verify that the total weight and CG for takeoff fall within the envelope.
4. Check weight and CG for landing.
During flight, fuel burn is normally the only weight change that takes place. As fuel is used, an aircraft becomes lighter. Furthermore, fuel moment also changes and it for sure affects total moment and CG position.
Summary: weight and CG is insight the limits during all phases of flight, nor extremly forward or aft, so the flight could be safely performed.