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  • OG GarlicSalt created a new forum post in ATA 29 Hydraulic Systems
    Working on Hawker 900XP with an intermittent HYD OVHT MWS light.

       

    This fault has some history and they had the reservoir temperature sensor changed at the last MX visit. Typically, the fault comes when its above 100 degrees out and the aircraft has been sitting on the ramp with the APU running.

    This type of fault is definitely not in my wheelhouse, with some hindsight there are quite a few things I would have done differently to isolate the issue much quicker. First, I will go through what we did and how I would do it differently in the future

    First things first the aircraft has no traditional hydraulic cooling system to investigate so the manual states that a component is bypassing causing the reservoir to raise in temperature and eventually send the OVHT MWS.

    First thing we did to establish a base was performed the main accumulator pressure decay test to see if the accumulator could hold pressure. We first had to block the spoiler bypass system which is a mod that is supposed to aid in cooling the hydraulics.

     

    After blocking that we hooked up the mule and pressurized the system to 3000psi, watched the main accumulator go up then kill the mule. The pressure is supposed to hold for at least 20 seconds before dropping. In our case the pressure dropped instantly.

    Next thing we tried to do was pull the aux hydraulic handle in the flight deck. This should separate the landing gear system from the main system. If we tested it again and the test passed we would know that the fault is somewhere in the landing gear hydraulic system. With the landing gear isolated from the system we ran the test again but still failed.

    At this point we decided to go after the low hanging fruit and disconnect some of the main component returns to see if they bypass under pressure. We tried nose wheel steering, brakes, emergency brakes, main accumulator discharge handle. All of these components check good so we decided to start digging into it.



    Next thing we did was to cap the hydraulic pressure manifold inlet line, this will isolate the components side from the full flow relief valves and other upstream components. With this capped we now have a passing test, which tells us that the issue is downstream of the pressure manifold.

    At this point we decided to check the pressure maintaining valve located underneath the main reservoir behind an access panel for bypass. We had to fully isolate the other systems from the pressure manifold leaving only the maintaining valve in the system and performed the test again. We found that the maintaining valve  was bypassing. At this point I plugged the return side of the maintaining valve and tried the test again all good. I reconnected the systems one at a time retesting each time and still everything passed. Pressure maintaining valve confirmed to be the defective part. Removed and replaced the part and aircraft was back in service without issue.






    Now this process took me about 3 shifts to T/S and one to replace the part, and knowing what I do know I would have approached this a lot differently.  If I were to work this problem again and found the original pressure decay tests to fail, I would go straight to the pressure manifold. I would disconnect the runs one by one rechecking the pressure with each. I would keep doing this until the pressure test passed and that would then show me the system with the failed component. This would eliminate removing a lot of hard to get at lines and opening components to check for leakage. Using this approach, I feel we could have had this solved in one day or less. It doesn’t help trying to decipher the vague statements in the hawker AMM either.
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  • They have the WDM online but not aircraft specific so 75% of the time your going to the old paper copy to find out how the airplane was completed. There was no reference to a thermal discharge but there was a metal shard that looked like it was originally the cap to the bottle, not sure if it was made to let go at a certain temperature or the bottle just got so hot and overpressurized. Doesn't help when ambient temp is 120 + running the apu with a duct leak.
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  • Software updates are constant Emaps ECharts, EGPWS, terrain database, nav database. All the airplanes load a diffrent way with diffrent programs ect. Atleast the newer aircraft are alot more user friendly pop the software on a USB and go.
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  • OG GarlicSalt created a new forum post in ATA 49 - APU
    Working on a Hawker 900XP with APU that wont start.

     Some background, we had just pushed the aircraft outside and started up the APU. We parked it on the spot for about 30 minutes when flight crew arrived there was a separate issue that made us bring the airplane back to the hangar. After fixing the issue we pushed back out and the APU failed to start. We canceled the flight and started to troubleshoot the issue.

     There is limited manuals for the Hawker and especially so for the APU. When flipping the APU master switch is seemed like the system was completely dead no relay click in the flight deck ect.  So, my first thought was the switch.  Checked the switch and it checked good, so started to dig into the manuals to see what I could find.

     After checking further into the manual, I see that there is a note saying if the APU fire bottle pressure reads zero the APU wont start. So easy to check and oddly enough the APU fire bottle read zero.  So, issue was found easily but not sure how the bottle would have been blown between starts. I replaced the bottle and made sure to double check the squib activation to make sure it wouldn’t be inadvertently set off. All wiring checks good from the APU fire switch the squib connector. Attach everything and the APU starts up and works properly.

     I’m trying to figure out how this happened so we disassembled the old fire bottle and I find out that the squib was never blown yet the bottle was blown. I figured it must have been a thermal discharge.

     

     

     Restarted the APU to trouble shoot further and found an open hot air duct that was putting hot air onto the fire bottle causing the bottle to blow.

     


    We reconnected the line and have had no issues since. What made this odd is that we were with the airplane the entire time and no one noticed the APU bottle blow and the APU never shutdown, so that threw us off at the start.
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  • OG GarlicSalt created a new forum post in ATA 44 - Cabin Systems
    Working on two G650ERs with a few cabin view problems. Main PAX complained that stock tickers were no longer working, shortly after the main cabin monitors stopped displaying cabinview/airshow all together.  After restarting the aircraft, it would work intermittently roll of the dice each time. Unfortunately, Gulfstream likes to keep a lot of information about the cabin systems to themselves. We ended up having to get in contact with Gulfstream tech support to help guide us forward. They instructed us to check the status of the AVDS node software. To do this we plugged an ethernet cable from our laptop to the cabin MX port, ours is located in the aft cargo compartment just right of the door under the upper access panel. After connecting we opened the AVDS node software, it comes stock on the computer from Gulfstream if you don’t have that there is a download for the newest version in the AVDS S/B. Once the software was open I found out that our version was still 1 while the newest version was 3. To get the work instructions and files required we used the Innovation Advantage S/B AVDS Node S/W Update



    To do the update you have to be connected then hit the retrieve button on the Software package side, this saves your current version incase there is an issue. I did the same on the configuration file. Next just click send on the software configuration tab and select the new software that you downloaded. Don’t be alarmed if it takes along time, it can take up to 5 minutes to move from 0% on the update screen. Make sure to update in order, so if you version is old like ours was we had to update to REV 2 then REV 3 to avoid issues. 

    Make sure to thoroughly read the procedures before doing this as you could brick the AVDS nodes if performed improperly, forcing you to gain access to all nodes and plug into them directly to force the correct update.  After updating the nodes, we now had a new issue, all the cabin view was working but now the screens were displaying in only magenta and green color. Again, we had to talk to techops to see how to move forward.

       

    They weren’t exactly sure why it was happening but they added one line of code to our configuration file that fixed the problem. This is what they added, you could add it yourself but I would recommend having gulfstream modify your configuration. After all of this our cabin issues were solved.


     
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  • Thanks Mark, this airplane is young for 767s produced in 2004. The airplane received the LDS mod a few years ago, since then we have had multiple issues with things wired backwards loose pins ect.
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  • OG GarlicSalt created a new forum post in ATA 27 Flight Controls
    Boeing 767-200 with intermittent LE ASYM EICAS message. This problem resulted in two air turnbacks and forced the aircraft to jettison fuel on both occasions. This issue was worked twice and a "fix" found both times by a repair station. After returning from MX we received the aircraft again and on its second trip out the message briefly popped up with the Flap/Slat position indicator bouncing between 0 and 1.

    At this point I picked up the task and with the history associated with this I wanted to do a very thorough check of the system. I performed a BITE test on the PSEU and it indicated what should have been the faulty sensor. After noting this I still decided that I would ignore the finding from the BITE test and use an LCR meter to test every sensor individually. At this point I found pin F12 on the PSEU for the #3 LH O/B slat to be pushed back. After reinserting the wire and verifying the lock was holding, we closed everything up and no issues since.

    What made this an odd find and what seems to have tripped up the repair station is that each time this problem occurred the PSEU faulted a different sensor than the one actually causing the problem. The PSEU indicated one sensor on the R/H OB, L/H IB and when I did the BITE in indicated 276 for the #1 L/H O/B while the fault was with 278 #3 L/H OB slat.

    Wire came out after being lightly pulled not engaged with the lock.
     
       




     
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