You can Google up what an S-92 is, and you can google up what an APU is, and an accumulator as well....but I'll give a brief discription. The S-92..is the new heli that Sik makes, and APU is an Auxillery Power Unit on the s-92, which is nothing but a tiny self contained jet engine that is used to feed electical power to the aircraft, and the accumulator is a nitrogen/hydrolic bottle that stores energy to start the APU. The accumulator is a simple component...a high pressure nitrogen bottle, on one side, hydro fluid on the other, and a diaphram between them, with a pop valve that is electrically actuated or manually popped...the nitrogen in the bottle is at 2100 psi +- 100 psi, and the hydrolic gets serviced from the #3 hydro pump system, and is about 1.5 gallons of fluid. so this thing sends a mad rush of hydro fluid thru a pipe that is connected to the APU start motor, and it turn a gear that turns the APU, then the fluid rushes back to the accumulator, and becomes a non pressureized fluid, and the nitrogen drops from 3900 psi back to it's normal precharge of 2100spi.....it's a cool system, most aircrafts have them.
Well a month ago, an inspector noticed a drop in the drain tube that connects to the accum, and that's bad...it means that the diaphram is leaking, and could possible rupture after time, which would litterally spray hydro fluid everywhere in the cabin at any given time....so he wrote up the discrepancy, and the creiw cheif ordered the part. they was waiting for the aircraft to go thru the re-works that needed to be done, so that means that the aircraft will be down for a while....it has only 3 flight hours on it. Well, the part is there, and they asked me to change it....
Its an easy job, I just have to follow a list and do what it says..OK....this is a new aircraft now, so the list that they made is not really tested and tryed...and the engineeres are working on the aircraft with a desk...and they forgot a few things....so I got with the crew cheif and he told me the best way to do the job. Simply turn off all the switches that power they system, remove the ignitor cannon plug so the apu wont fire up and run, disconnect all 3 hydro systems from the resevoirs, so the system wont piss fluid everywhere...varify the intake on the APU is clear, so no shit will get sucked into it and cause any damage, and then pop that bitch to make everything spin and to bleed off the hypro pressure...thats the fun part...hehe. OK now the hydro pressis down to zero psi, it's time to bleed the nitrogen pressure down to zero...then start disconnecting all the lines and clamps. It's a messy job, the APU start motor is on top of the aircraft, and the bottle I'm removeing in under it, so all the fluid in the lines will piss everywhere when I disconnect it, so I got a lot of rags. I had to take the APU generators vent off, and a lot of other items just to get to some of the lines, and work in tiny spaces to get shit done.
Got the accumulator out, and the new one is ready to go in, they had a peice of paper in the box, and the price was on it....$16,499 for this damn part...wow...I said. so now I know not to drop it.
By the time I got the old one out, and the new one installed, it was time to go home. So I had to do the forms and shit to annotate what I did, disconnect, and parts that were removed and other crap. And clean up the gallon of hydrofluid that spilled out 
Next day....I finished installing it, and ran into a problem...the inspector didn't like the best bolt on a clamp that holds it...I didn't bed it, it was like that when I removed it, so I had to spend a day removeing the accumulator again, and order new clamps, drill them off from the airframe and rivit the new ones back on. And found out why the bolt bent....a rubber peice was right where the clamp attacehed, and was to thick for that area...so it was something that the original installer did..not me. But when I was removeing one of the big hydro lines the crows foot slippid and gouged out one of the fittings, so I rejected that part, and ordered a new one...when the tube came the next day..it didn't have any fittings, so they had to take the tube back to another part of the factory and swedge the fittings on. And now this little swap is in day 3...hehe
Last night, go the tube, installed it, torqued it to 798 inch/pounds, got the nitrogen lines on, torqued it to 160 inch pounds...blah..blah...blah...so I know it is done by the book. So then I servied the nitrogen finally...to 2100 psi...and took a break...came back and it dropped to 2000 psi...I noted that..and pressed on with the serviceing...recoonected all the hydro systems, filled the resevoir, and pumpped the manual accumulater handle to build up pressure. There was a lot of air still in the hydro lines, so I had to keep filling, bleeding, and pumping. Finally built up the pressure to 3900psi...and I took another break...cam back and it dropped to 3800...so now I got worried and told the inpector the play by play...and they said to monitor it...so I did...and then I came up with the idea to pop the motor again....to re-check the precharge...so I did...it dropped to 1800 spi...so now I know that the nitrogen side of the bottle is bleeding down...and tonight...I might have to change the bottle again with another one...unless the line that I torqued properly needs a little more torque
So B.....new parts do fail....just be glad you don't own an Aircraft
Well a month ago, an inspector noticed a drop in the drain tube that connects to the accum, and that's bad...it means that the diaphram is leaking, and could possible rupture after time, which would litterally spray hydro fluid everywhere in the cabin at any given time....so he wrote up the discrepancy, and the creiw cheif ordered the part. they was waiting for the aircraft to go thru the re-works that needed to be done, so that means that the aircraft will be down for a while....it has only 3 flight hours on it. Well, the part is there, and they asked me to change it....
Its an easy job, I just have to follow a list and do what it says..OK....this is a new aircraft now, so the list that they made is not really tested and tryed...and the engineeres are working on the aircraft with a desk...and they forgot a few things....so I got with the crew cheif and he told me the best way to do the job. Simply turn off all the switches that power they system, remove the ignitor cannon plug so the apu wont fire up and run, disconnect all 3 hydro systems from the resevoirs, so the system wont piss fluid everywhere...varify the intake on the APU is clear, so no shit will get sucked into it and cause any damage, and then pop that bitch to make everything spin and to bleed off the hypro pressure...thats the fun part...hehe. OK now the hydro pressis down to zero psi, it's time to bleed the nitrogen pressure down to zero...then start disconnecting all the lines and clamps. It's a messy job, the APU start motor is on top of the aircraft, and the bottle I'm removeing in under it, so all the fluid in the lines will piss everywhere when I disconnect it, so I got a lot of rags. I had to take the APU generators vent off, and a lot of other items just to get to some of the lines, and work in tiny spaces to get shit done.
Got the accumulator out, and the new one is ready to go in, they had a peice of paper in the box, and the price was on it....$16,499 for this damn part...wow...I said. so now I know not to drop it.
By the time I got the old one out, and the new one installed, it was time to go home. So I had to do the forms and shit to annotate what I did, disconnect, and parts that were removed and other crap. And clean up the gallon of hydrofluid that spilled out Next day....I finished installing it, and ran into a problem...the inspector didn't like the best bolt on a clamp that holds it...I didn't bed it, it was like that when I removed it, so I had to spend a day removeing the accumulator again, and order new clamps, drill them off from the airframe and rivit the new ones back on. And found out why the bolt bent....a rubber peice was right where the clamp attacehed, and was to thick for that area...so it was something that the original installer did..not me. But when I was removeing one of the big hydro lines the crows foot slippid and gouged out one of the fittings, so I rejected that part, and ordered a new one...when the tube came the next day..it didn't have any fittings, so they had to take the tube back to another part of the factory and swedge the fittings on. And now this little swap is in day 3...heheLast night, go the tube, installed it, torqued it to 798 inch/pounds, got the nitrogen lines on, torqued it to 160 inch pounds...blah..blah...blah...so I know it is done by the book. So then I servied the nitrogen finally...to 2100 psi...and took a break...came back and it dropped to 2000 psi...I noted that..and pressed on with the serviceing...recoonected all the hydro systems, filled the resevoir, and pumpped the manual accumulater handle to build up pressure. There was a lot of air still in the hydro lines, so I had to keep filling, bleeding, and pumping. Finally built up the pressure to 3900psi...and I took another break...cam back and it dropped to 3800...so now I got worried and told the inpector the play by play...and they said to monitor it...so I did...and then I came up with the idea to pop the motor again....to re-check the precharge...so I did...it dropped to 1800 spi...so now I know that the nitrogen side of the bottle is bleeding down...and tonight...I might have to change the bottle again with another one...unless the line that I torqued properly needs a little more torque
So B.....new parts do fail....just be glad you don't own an Aircraft
