What Happens When a Hydraulic System Fails?

Airplane taking offFear of flying is amongst the commonest phobias in the western world. The IATA (International Air Transport Association) predicts that there will be 3.3 billion global air travellers by 2014, a huge rise of 32% on the 2.5 billion people that flew in 2009. Despite such fears it's clear that more and more people are travelling by air each year. All of which means the technology has to be better than ever and the safety precautions more stringent than ever before. A very real fear when it comes to plane travel is what would happen if the hydraulic system of an aircraft failed.

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Hydraulic systems work on the principle that a force applied at a single point will be transmitted to another point using an incompressible fluid. This fluid is normally an oil and is defined as a "fluid which is not reduced in volume by an increase in pressure." A basic system will consist of two pistons and a filled cylinder connecting them. In brief, when one of the pistons is pressed the liquid moves through the cylinder and exerts the pressure on the other piston, which causes it to move. The efficiency of oil is very good and the majority of the applied force appears at the second piston. The great thing about hydraulic systems is that the cylinder which connects the pistons can be any shape or length, enabling the fluid to travel through a complex myriad of forks and bends if so required.

In aeroplanes, hydraulics controls the movement of an aircraft in all four directions. In the event of a hydraulic failure, the pilots will lose the ability to control left or right. Only in the event of a total hydraulic failure will pilots be unable to climb. However, there is still a way to fly a plane in this unlikely eventuality. By increasing and decreasing the power of the engines, skilled pilots will be able to slowly descend the plane to a safe distance to attempt an emergency landing. It is worth pointing out though, before people cancel their flight tickets in fear of this happening, that not only would this happen in the rarest cases, but there are a number of additional security measures that are in place in case of such a hydraulic failure. Smaller planes will usually have a manual flight control option, which means you can override the system and fly the plane without the aid of hydraulics. For bigger planes this isn't an option. However, large commercial aircraft will likely have three of four hydraulic systems and it would be an exceedingly rare occurrence for all to fail at once.

The development of hydraulics has been key to air travel, and on-going investment and extensive safety testing all points to how serious an issue this is regarding a form of transportation that is growing year by year. Don't worry though, statistically there is more chance of you falling over in the shower and killing yourself than there is of dying in a plane crash. So watch where you've put the soap.


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