Today we started work on an engine change. A A&C job at first sight but this time we'll be doing it with only one A&C engineer and two coneheads (avionics).
My colleague Sjap is the A&C engineer who's taking charge of the engine change today, he run's a website about the technical aspects of the 737's and can be found at Sjap.nl.
First off, we take a hand over from the previous shift who had started work and opened up the engine cowlings and disconnected the hydraulic lines, the fuel lines and most of the electrical connectors.
I start off between the thrust reverser doors, disconnecting some more electrical connectors (fire detection wiring, engine vibration sensor wiring and such) and some pneumatic lines and pipes.
This is a cramped workspace but also an area wich is the usual suspect for damage to be found. This is the hot section of the engine, this is also one of the highest vibration areas of the aircraft and it is also one off the most cramped spaces on the aircraft.
Here's a view of this core section taken from the other side of the engine.
So I take the connectors off and remove the bolts holding the bracket onto the engine.
The thrust link that u can see is responsible for converting the engine's thrust to the airplane. It takes the full forward force of the engine.
After this I go to the other side and remove some more pneumatic lines.
When we have all the lines disconnected we make some room for the precooler control valve to come out of the pneumatic duct.
This large metal contraption is where the thrust link connects to the aircraft. This also needs to be disconnected.
And this is one of the three points wich hold all the engine's weight. We leave these connected until we have the engine on a crane.
Here is Sjap in his 'the thinker' mode.
He's getting ready to connect the crane onto the engine.
Positions it at the right place.
The crane must be exactly in the right place if we don't want the engine to 'jump' off the pylon.
The crane is now in position and the cable's are connected to the engine with force indicators.
The cable tension is increased and the engine mounts are slowly disconnected.
When the engine mounts are disconnected, the engine hangs from the crane and we can start to move the engine downwards a bit.
Sjap loweres the engine and watches if the engine doesn't drag anything down with it.
Then the engine is free from the aircraft.
The shiftleader comes by to have a look at the removal of the engine, here he is hiding behind the engine.
With the engine hanging it's time for us to go and have lunch.
After lunch we come back and I turn off the flash option on my camera.
This is what the aircraft looks like with one engine missing and the thrust reverser doors opened.
Now we need to get this engine off the crane and into an engine cradle so we connect the cradle connections to the engine.
That connection will slide in this connection on the cradle here.
We move the engine over the cradle.
But before we can lower the engine onto this cradle we must take the engine cowling off and place it aside so that we can connect it to the new engine later.
See the remove engine inlet cowl section for this.
After this, we lower the engine onto the cradle.
The engine must be lowered enough so that we can put a large metal pin through the line up hole on the cradle.
At the back end of the engine a simple pin is sufficient.
And on the other side another pin.
At this time we have a look at the new engine that we are going to fit.
Lately the company has been getting these engines from a company in brazil rather than our own engine shop. These engines usually require a lot of work by us to undo all the mistakes that the engine overhaul shop had made. This engine is not so bad, it takes only a few fixes for us to be able to fit it to the aircraft.
topside of the engine.
We hang the engine from the crane and pull it up to the pylon but immediately run into a problem.
These clips have been fitted the wrong way around causing them to be squashed when the engine gets pulled up to the pylon.
We reinstall the clips the right way around.
My colleague tightens the mounting nut and torque's it to the correct value. (This will have to be done with the engine firmly pressed to the pylon offcourse).
Sjap will take care of the ones at the backside of the engine.
We connect some of the pipes, lines, connectors and such.
The engine is now hanging on the airplane. It is the end of our shift now and the nightshift gets to continue connecting the rest of the connectors and pipes, hang the fan cowling doors to the engine, inspect the engine and testrun it.
For us it's time to go home.
The next day we come in and we find the aircraft still sitting in the hanger. It turns out that the engine shop had fitted the engine driven pump mounting plate incorrect. This resulted in the EDP having the wrong angle and making it impossible to close the fan cowl doors. The previous shift had ordered a new EDP for us and so we continue with this job and first have a look at the pumps.
The scavenge line on the pump was connected to a different opening on the new pump. This is presumably due to the angle of the pump when it was installed and the location of the hydraulic pipe.
This is the incorrectly installed mounting plate.
So we take it off.
And install it correctly.
The engine is now installed, the doors are closed, the inlet cowl is fitted, the insides have been inspected for loose tooling, loose connections etc.
It's time to testrun the engine.
I don't have footage of running the engines because at this time the battery of my camera went flat but here's a short clip of another testrun with my colleague Rob.