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tenten

Outflow valve and safety valve..!

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During the FCF of 382G “CIVIL†airplane-, The Auto pressurization mode fails to pass the “pressure controller differential valve checkâ€.

Safety valve was controlling the differential pressure before or might be at the same time of pressure controller.

Safety valve required to remain closed during this check.

Safety valve cracked to open at 14.8 in/hg and will maintain 14.9 in/hg; while pressure controller (when isolating the safety valve) was taking over at 14.9 and maintaining 15.0 in/hg.

All pneumatic lines checked, 2 pressure controllers 2 safety valves and 2 outflow valves had been changed to find a proper matching setting with no effect.

Settings of differential pressure controlling limits according to our book(FM 382-6CF)are:

Outflow valve differential control 14.2 (+0.6, - 0.4)

Safety valve differential control 14.9 (±0.5)

Details of plus or minus show the overlap of both valves setting; however book require the safety valve to remain closed. Any help on this will be appreciated.

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Not sure if it’s an issue or the cause of your problem; but if you have a USAF C-130 type (P/N 102150-0 or 3314765-1) outflow valve installed it will stay closed until a maximum differential pressure of 15.18 inches of mercury is reached. The safety valve used by USAF doesn’t open until you reach maximum differential pressure 15.90 inches of mercury. So, if a USAF type outflow valve is installed, it won’t open before your Civil Registered C-130 type safety valve does at 14.9 inches of mercury and could cause the problem you’re having.

Just a thought as I’ve seen this type of discrepancy in the past when working on a mixed batch of Military and Civilian type C-130’s and the wrong P/N outflow valve was installed. Hope it helps.

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Thanks MARS for the input; At the time I am out of IP manuals, to my knowledge Outflow Valves are changeable between military and civil registered aircraft; just check and reconfirm; If you are correct on this... puzzle is solved, hens the one installed on the defective aircraft is P/N 102150-0., with a Safety Valve P/N 103036-5, and a Pressure Controller P/N 102538-3-1.

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You’re welcome. Outflow Valves are not interchangeable between Military C-130 and Civilian Registered L-100 aircraft, because of the difference in maximum differential opening settings (among other things). Neither are the Safety Valve and/or Pressure Controller interchangeable.

None of the P/N’s you listed are in the -4. The -4 lists the following P/N’s: Safety Valve; 103036-3, Controller 102076-5, 102538-2-1, or 102538-5-1.

Once you install the correct P/N Outflow Valve, this problem will be solved.

You can verify the cracking pressure of the Outflow Valve during a ground pressurization check with the #2 Test Valve closed and # 1 Test Valve open. Hope this helps you.

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Unfortunately, based on our authorized manual SMP 1729 for the airplane 382G65C Lockheed Ser No. 5024 (L-100-30 civil registered) I confirm the following from the IPC:

Outflow Valve P/N 102150-0

Safety Valve P/N 103036-5

Pressure controller P/N 102538-3-1

As for our military registered airplanes (C-130H Lockheed Foreign Direct Sales) (with Lockheed Ser No 4879. and based on SMP 893:

Outflow Valve P/N 102150-0

Safety Valve P/N 103036-3

Pressure controller P/N 102538-2-1

Therefore; according to our manuals both types sharing the same part numbers !!

The key of deferent control settings (military 15.16) (civil 14.25)., might be based on the deferent settings of the pressure controllers rather than a deference settings of outflow valves, since pressure controllers on each type having a deferent part number thus deferent setting.

Regarding ground pressurization check with #2 test valve closed and # 1 test valve open; it had been done on ground and the best combination of components installed found to be both cracking open at around 14.8 hg.

And by isolating the safety valve during flight (disconnecting safety valve static line reference) the outflow valve was maintaining the 15.0 hg.

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Oh well, maybe my old-age Can’t Remember S#*t (CRS) syndrome is kicking in; my experience is mostly on C-130-series aircraft and my experience on L-100-series aircraft is limited. Though I really thought we had changed the outflow valve and our problem went away... With that in mind:

To my knowledge the safety valve operates completely independently of the outflow valve and pressure controller as there are no pneumatic connections between them. So, if outflow valve cracks open as required in-flight with the safety valve “forced” to remain closed and everything else checks good, you might consider the following:

Based on the settings you provided in your original posting of:

“Outflow valve differential control 14.2 (+0.6, - 0.4)”

“Safety valve differential control 14.9 (±0.5)”

If your overhaul facility adjusted the outflow valve or pressure controller to the high side cracking pressure of 14.8 Hg and the safety valve to its low side cracking pressure of 14.4 Hg, your safety valve would open first and the outflow valve would never reach the cracking pressure it’s adjusted to open at … Just another option for you to consider. Again, hope it helps.

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If your overhaul facility adjusted the outflow valve or pressure controller to the high side cracking pressure of 14.8 Hg and the safety valve to its low side cracking pressure of 14.4 Hg, your safety valve would open first and the outflow valve would never reach the cracking pressure it’s adjusted to open at … Just another option for you to consider. Again, hope it helps.

Indeed it helps, and based on the above, we set the agreement with the flying crew, to limit deferential pressure to below 14.0 hg until overhaul facility-3000KM away-reset our components.

Thanks a lot MARS.

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