Legendary Hydraulic knowledge!

Good afternoon my aeronautics enthusiasts,

It’s been two weeks since my last blog and that means that a lot of things have happened during this time. We did a lot of practises at the workshop and we also learnt new knowledge about the systems of the aircraft.

One of the most interesting things we’ve done, has been related with the hydraulic system of the aircraft. As you all know, the hydraulic is very important in the aircraft because almost all of the moveable’s parts are moved with the hydraulic. Everything related with the flight controls, such as the elevators, flaps, slats, spoilers and even the retraction of the landing gear is hydraulic actuated.

As you can see, a loss of hydraulic can cause the airplane to become uncontrollable and that’s why we have different system to avoid a total loss of the aircraft control. But, have you ever wondered from all this hydraulic pressure comes from?

The two practises we did, were related with the generation of this pressure and how to cut it. The first practise was removing/installing the engine driven pump of hydraulic and the second one was removing/installing the hydraulic shut off valve.

In the aircraft, the hydraulic is pressurized by two ways. The first one is to pressurize the system with the engine driven pump which is moved when the engine of the aircraft is turned on. The second way is thanks to a hydraulic electric pump, which as it name says, it is moved electrically and doesn’t need the engine turned on. This second pump is usually turned on when doing maintenance for doing checks or in case of an emergency or malfunction of the driven pump. As you can see the pump use severals pistons to increase the pressure coming form the supply up to 3000-5000 psi depending on the aircraft.

The driven pump is connected with a splined shaft directly to the accessory gear box which is connected to the main shaft of the engine. It’s removal was kind of difficult as it is located in a very tight spot with tubes all around. It is mandatory that always that you work in an hydraulic system to make sure that the system is depressurized. If there is a remanent of pressure and you remove something, you will do a mess of hydraulic all around you or even cause you severe damage. It is like disconnecting a hose while water is running inside, when you disconnect it, it will eject water in all directions as pressure inside is higher than in the exterior. As it rained all the week we weren't able to take many photos but the pump looks like this.

The second practise was removing the shut off valve, this one was a bit easier than removing the driven pump. The shut off valve is an electrical valve that cuts the flow of hydraulic through the tube. There are many shut off valves in the aircraft, from the fuel to the oil or in this case, the hydraulic. This valve is just before the driven pump of the aircraft and cuts the supply line to this pump. We normally cut the shut off valve when there is a fire on the engine or when there is a loss of hydraulic on the system. It only has two positions, fully opened or fully closed.

Removing it was very simple, we only had to remove four bolts and disconnect the electrical supply. We even had to do a test if it was working correctly. With the help of an external battery of 28 volts we connected the correct terminals and managed to see how the valve closes and opens. It is a very strong mechanism so never put something inside as it will cut it like butter. We even put the root of a banana and cut it with no problem.

New practises will arrive but from now on I don’t have anything else to share with you related with the workshop. However outside Globalia I did some fantastic things and one of them was going to “la Fira del Motor” at Inca. I mentioned this on my last blog and finally the day came. We meet very early at Inca, more and less at 8:00 and we had to pick up my girldfriend's pink Seat 600 and I think that it is the one with the best colour and people love it. Once all the cars arrived, we drove around the city and park all the cars in the location they told us. It was a shame that we didn’t drive much because I really like driving old cars and I don’t know why but the Seat 600 gives me a special feeling. It was the car that motorized Spain and if you ask somebody about this car everyone tells you fantastic stories about the car.

I really liked driving back the Seat because since before the covid pandemic we haven’t meet all the members of the club. Apart from the meeting, I haven’t done nothing more spectacular than studying for our first exam of FOL and I must say that it went quite good!

So that’s all for today’s blog. I hope you really enjoyed and learnt new fantastic and awesome things about planes and myself.

See you on my next blog!