Centre of Gravity and how it affects flight

Published: July 06, 2019

14DAYPILOT

The centre of gravity (CG) of your aircraft can be seen when you manipulate the location of the centre of gravity forward or aft. However, how does the differences between forward centre of gravity and aft CG affect you during flight? Well read along, you’ll find the answers here.

In physics we have learnt that the centre of gravity of an object is the point in which the total weight of the object is considered to be concentrated. In most cases where the object is symmetrical, the centre of gravity can be found, well, in the centre of the object. Although, in the case of asymmetrical objects, the centre of gravity may be well beyond the centre due to the weight irregularity throughout the object.

When talking about centre of gravity, we can assume that we are also talking about the balance of the CG. On an aircraft, the CG is not necessarily in the centre of the aircraft, it is determined by the amount of load added onto the aircraft such as baggage, passengers, etc. The distribution of these weights requires the aircraft to manipulate its own CG in order to find the perfect balance.

As the load of the aircraft continues to shift during flight, or even when on the ground, the position of the centre of gravity is constantly changing. There is, however, a range of distance between the maximum point in which the CG is allowed to be located in on the fore and aft of the aircraft. By having the CG located far too forward, the aircraft may experience a nose-heavy condition in which the aircraft will be slanting downwards on the nose end while having the CG located too far aft has the aircraft experiencing tail-heavy conditions similar to the nose-heavy one but instead is occurring on the tail.

Why is all of this important? Why are shifts within the aircraft dangerous? Think about having a plate of water placed above a tennis ball. When the plate is tilted to far to the right or to the left, the water will shift accordingly, and what will happen next? The plate will tilt too far and fall off the tennis ball. Much like an aircraft, when the centre of gravity of the aircraft is located too far off the range, the aircraft will be heavier on one side than the other and the pilot may lose control of the aircraft.

Nose-heaviness and/or tail-heaviness are all caused by longitudinal unbalance of the aircraft. So what about the lateral unbalance? When lateral unbalance occurs, wing heaviness also occurs. Even if the distribution of weight of load inside the aircraft is even, the aircraft may still be affected by lateral unbalance. This is due to the fact that the lateral axis is also affected by fuel weight. If the fuel was not added equally on the right and left side of the aircraft, imbalance occurs.

The consequences of lateral imbalance may not be as severe as longitudinal, which is why it can be easily fixed by adjusting the trim or by holding and maintaining the pressure on the control. This allows the aircraft to enter an out-of-streamline condition that increases drag. Although this method may fix the imbalance, the pilot may become excessively tired, reducing alertness and the overall safety of the flight.

Furthermore, what is the effects of imbalance other than loss of control and reduced safety? When an aircraft is under a nose-heavy condition on ground or in air, the safety is definitely reduced. It takes a greater force to lift the aircraft from the nose end just to prevent it from crashing down, nose diving towards the ground. The same goes for tail-heavy aircrafts. This would cause a number of problems including burning of excessive fuel, inability to recover from stalls, and causing the aircraft to spin and spiral out of control.

When an aircraft is approaching an airport or any field of land in which it is about to land on, the pilot must make sure that the aircraft is properly balanced in terms of its centre of gravity as being nose-heavy or tail-heavy would indefinitely decrease the efficiency of flight, create longer stalls at a faster rate, and requires a greater effort to control the aircraft.

So to all of you that are about to fly an aircraft, will be flying an aircraft in the future, or is a passenger on an aircraft, be frank about the load you are bringing to the aircraft. It’s for your own safety. By manipulating the weight of your luggage, you are putting yourself in danger of said situations above. Always, always remember that prevention is better than cure. Join 14DAYPILOT Flight Academy to learn more on aviation knowledge and become a private pilot in just 14 days!

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