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agarrett
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agarrett wrote:

Where is the offload valve on a P model. Is it not in the center dry bay like the others?

Also, any idea why the offload valve is wired different than any other Herk.

PS; Dan Moen wants to know.

On the MC-P it is in the center drybay. I don\'t know how they do it on slicks or Talons. I know that some of the fuel system was modified when they added the pods and fuselage tanks and now a few valves don\'t really match the schematic anymore.

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The offload valve should still be in the center drybay aft of the refuel/dump manifold Y out to the wings. On shadows, the Y was more like a diamond for uarrsi. Power for the valve was changed from main DC to essential DC with the uarrsi mod and wired into the line drain switch on FE\'s panel. Tell Dan he\'s slipping. He taught me most of this.

Mike

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Hey, Dan dumped all his Shadow brain cells when he became a WombatB)

We got curious about this because of a non UARSSI airplane doing a FARRP.

Art M. called me with the location. Its in the line way up above the SPR panel. Moving it would make sense if that is where the fuselage tank manifold ties in to the refuel/defuel/dump manifold because the offload valve needs to be aft of that.

Now, why its wired the way it is is still a mystery. According to an HC-H dash one it was wired that way before UARSSI.

Someone correct me if I\'m wrong but every other Herk I\'ve checked, if you put the offload switch to open during drain it takes power away from the offload valve relay and the ofload valve will close.

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agarrett wrote:

Hey, Dan dumped all his Shadow brain cells when he became a WombatB)

We got curious about this because of a non UARSSI airplane doing a FARRP.

Art M. called me with the location. Its in the line way up above the SPR panel. Moving it would make sense if that is where the fuselage tank manifold ties in to the refuel/defuel/dump manifold because the offload valve needs to be aft of that.

Now, why its wired the way it is is still a mystery. According to an HC-H dash one it was wired that way before UARSSI.

Someone correct me if I\'m wrong but every other Herk I\'ve checked, if you put the offload switch to open during drain it takes power away from the offload valve relay and the ofload valve will close.

So are you asking why you can open the offload valve with the master switch in drain?

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The reason you move the offload valve to open on the shadows and any other UARSSI equipped aircraft is because it is no longer wired into the SPR pump drain switch. They moved this feature to the line drain switch in the flight deck so they can utilize the SPR pump for draining the refueling manifold after inflight refuel. So bascially you just think of it as kind of backwards. After the pump has been running for the 5 minutes of draining, after inflight refuel, then the line drain switch is turned off in the flight deck and then the sump dump switch is opened to remove any leftover fuel after draining, which of course goes overboard.

I know this because I asked the same question when I got here at the \"Hole\". I came from slicks w/o UARSSI and I remember when you just had to go to drain with the SPR switch and the offload valve automatically opened. Now I will say this. There is one shadow here w/o UARRSI and the offload valve is still wired into the SPR drain switch. I hope this helps and if I am wrong somewhere I am sure someone will correct me.

Later and fly safe!

DaveB)

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Again, the curiosity was raised when we did a FARRP with a NON UARSSI HC-130.

Visual inspection tonight revealed that the offload valve was in the center dry bay.

On this airplane, the offload valve had to be opened with the offload valve switch when the master switch was placed in the drain position.

Dave, we covered this before. You say that UARSSI changed the function of the offload valve switch. I’m saying it didn’t.

If the refueling job guide tells you to place the offload switch to open on all UARSSI airplanes, not just P models, then I challenge the job guides accuracy. You, being in QA, are in a position to research this, verify it, and recommend/submit changes.

We verified that the offload valve opened when the SPR switch was placed to drain on AC-H/Us, MC-E/H/Ws and the ex Harrisburg ECs that we have here at Hurbie. Check your T-IIs at the “Hole†and see what you find.

The other question still stands. Does anybody know why the ex-rescue airplanes, or any others, were wired that way?

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The in-flight refueling system utilizes the single point refueling system drain transfer pump and valve in conjunction with the air refueling line drain valve to pump residual fuel from the UARRSI fuel line into #3 main fuel tank after a refueling operation. When the line drain switch on the air refuel panel is placed to ON, the offload valve, air refueling valve (signal amplifier must be in NORM or OVRD), line drain valve, drain shutoff valve, and the drain pump configure to pump the fuel into #3 main tank. The drain operation requires approximately 8 minutes. After completion of the drain operation, the line drain switch is placed to OFF, the open valves close, and the drain pump deactivates.

They are relay controlled by the drain switches on the aerial refuel panel and the offload valve switch on the SPR panel. The drain system is powered by 28V DC from the DRAIN PWR circuit breaker located on the copilot’s side circuit breaker panel.

Back in the 80`s some HC`s and maybe others were modded for FARP.

ZAK

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agarrett wrote:

Dave, we covered this before. You say that UARSSI changed the function of the offload valve switch. I’m saying it didn’t.

If the refueling job guide tells you to place the offload switch to open on all UARSSI airplanes, not just P models, then I challenge the job guides accuracy. You, being in QA, are in a position to research this, verify it, and recommend/submit changes.

We verified that the offload valve opened when the SPR switch was placed to drain on AC-H/Us, MC-E/H/Ws and the ex Harrisburg ECs that we have here at Hurbie. Check your T-IIs at the “Hole†and see what you find.

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UPDATE:

Last night I took the liberty to try this theory out on the MC-130P. The job guide was \"correct\" for this MDS. When the SPR master switch is moved to drain the OFF LOAD valve doesn\'t open automatically. The valve had to be opened by using the OFF LOAD valve switch. I haven\'t tried it out on the MC-130H as of yet, maybe tonight. One interesting tid bit for the Papa\'s is that they were rescue birds at one time. The ones we have here at the hole were HC-130N\'s at one time. This may have had something to do with the UARRSI at that particular time. Anyway I just wanted to post this and let you know what I\'ve found out so far.

DaveB)

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Cool, thats what the P model schematics I looked at show, and the MC-P HC-N dash 1s state.

All others indicate, as well as our field tests here that the offload valve will open.

Shadoif, any idea why some HCs would have to be modded for FARRP?

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Back in about 1981 there was a program thet brought rescue aircraft into SOF. We only had a limited number of tankers and quite a few HC 130Hs with nothing to do. It was not a fleet wide mod but a few select aircraft at the 33rd, 55th, 1550th and 41st. Numerous TDYs were spent doing FARP with the users that didn`t have probes.

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  • 3 weeks later...

From what I know, the shadow off-load valve was done with the HAR pods since it was wired that way long before the UARRSI mod (back when we called em \"Humpies\"). FTD was a long time ago but... On shadows the re/de-fuel manifold is used to deliver fuel to the HAR pods. What good would it do to drain the entire manifold after a refuel, go upstairs, put fuel to the pods only to fill it up again?... This way the lower portion of the SPR that\'s exposed to the wheelwell is drained leaving fuel in the upper portion of the manifold for HAR. You can tell when the off-load is closed on shadows, while draining after a re-fuel the SPR poppet valve sucks air in while it drains, normal herks don\'t due to air being let in by a check valve up in the flap-wells (the ones that leak in cold weather). Hope this helps. Cheers.

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