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Low air flow cargo compartment air condtioning.


sparkchaser
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We have had an issue with the air crew writing up cargo comp A/C pack distributing weak air flow on a 89 model (c-130h). We have already changed a bad low temp control valve, flow control shutoff valve. Also we checked for the water separator/sock for and icing or contamination. Did not find any leaks with the heat exchanger and the turbine is running like a champ. We suspect the crew is writing it up because it’s been really hot lately and until they get the engines going they will have less air with the APU.

Some people want to throw a turbine at the aircraft but its working fine with great suction and the air is cooling. I was hoping to find someone with a some experience with the A/C packs that may have some troubleshooting ideas or that could lead me in the right direction. I hate shot gunning parts!

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I have very little experiece with the A/C system, but is it possible you are losing some bleed air via the aux vent valve or the floor heat shutoff valve? What about the cargo compartment/flight deck diverter valve?

Also, is the air recirculation fan on, and is it operating the way it should be?

This is what was in Volume 16, No 2, Lockheed Service news:

If flow is weak, or if there is no flow, check the position of the flow control valve. The position indicator on the side of the valve should indicate about one-third to one-half

open. The valve operation is affected by ambient conditions and bleed air system pressure; therefore the exact position may vary somewhat, depending on operating conditions.

Be sure to check for system leakage at duct joints, especially at the water separator. Visual inspection will usually pinpoint this type of trouble.

A failed cooling turbine will also result in reduced airflow; however, this condition will also be accompanied by an inability of the system to provide adequate cooling.

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With the APU "ON" and APU generator "ON" there is lower air pressure for the AC pac to operate from and no power for the recirculation fan (LH AC Bus). These combined conditions will result in the reduced flow from the CC AC ducts. If there is adiquate flow with engine bleed air and LH AC Bus powered your aircraft is operating normally. You may have a bad recirculation fan which will cause low flow. Try running the APU with bleed air ON then apply external power and turn on the recirculation fan and see if you have better flow. If the recirc fan does not trun ON with the Fan switch try the under floor heat switch as there is a relay installed so the fan runs when you turn on the underfloor heat NO matter the position of the Fan switch.

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If your turbine is high time, the nozzle could be the issue. Each hole in the nozzle of the turbine is like a small venturi; if they erode, your turbine loses performance, and will not cool at the same rate. This allows to much flow across the turbine wheel, and not the compressor of the turbine.

If your turbine is low time, shimming between the nozzle and the turbine wheel can often times be the culpurit. Either way, just because your turbine is spinning fine, and sucking, fine, it could be low in performance.

The only real way to tell if your turbine is performing at an optimum level, you would need to perform a functional test on it. We check ours for turbine inlet air pressures and temps, vs turbine outlet pressures and temps, fan inlet and outlet pressures and temps, and so on and so on...

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There aren't any A/C inlet plugs down inside the intake, are there?

While at the 'Dorf, we had two aircraft we got from somewhere over in the far east that had plug covers inside the fight deck A/C intake. One of them had two sets.

"What the hell is happening to my covers? Someone must be stealing them..."

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We have had an issue with the air crew writing up cargo comp A/C pack distributing weak air flow on a 89 model (c-130h). We have already changed a bad low temp control valve, flow control shutoff valve. Also we checked for the water separator/sock for and icing or contamination. Did not find any leaks with the heat exchanger and the turbine is running like a champ. We suspect the crew is writing it up because it’s been really hot lately and until they get the engines going they will have less air with the APU.

Some people want to throw a turbine at the aircraft but its working fine with great suction and the air is cooling. I was hoping to find someone with a some experience with the A/C packs that may have some troubleshooting ideas or that could lead me in the right direction. I hate shot gunning parts!

So if I understand this correctly the aircrews are having a problem with the APU keeping it cool in the back, on the ground, before engine start-up. Umm....who cares? Really?

Does the system work properly inflight? That's all that really matters.

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So if I understand this correctly the aircrews are having a problem with the APU keeping it cool in the back, on the ground, before engine start-up. Umm....who cares? Really?

Does the system work properly inflight? That's all that really matters.

Like Tony said I don`t see any problem with the sys. We had the thing back in the Day with just the GTC running on a real hot day.

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"We suspect the crew is writing it up because it’s been really hot lately and until they get the engines going they will have less air with the APU."

Come on NOW.....

The intake plug is true though!! Had a mech start up the APU and "Cool" the flight station and during my preflight noticed only the CC AC plugs in the back of the aircraft.... You guessed they were sucked in!!!! I think there is a mishap based on that issue. If I remember AC pac caught on fire and destroyed the Aircraft.....

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Ok let me get this straight, The Aircrew is writting up the CC AC as low flow with only the APU supplying the Air.

Heres my take on this , AS a Flight Engineer on H2 we have 89 Model herks here in Youngstown , and when it get hot outside You will have low flow from the C/C pack. besides when you run it with the APU its real easy to Exceed the EGT limit for the APU so its not recommended to run the C/C pack with the APU on the ground in the Heat. Does the pack cool down the Cargo compartment with the Engines running if so , Your crews do not have a problem, So tell them to have a coke and a Smoke and stop writting it up.

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Hey Tiny , Sorry about that But I'm Ole School, I'm not a big fan of the new Air Force Inc.

I'm sure you remember back in the Day You either learned it or you Found something else to do.

Archie

That's pretty much it Archie. I can't believe what they've done/are doing to my Air Force.

I could give the CSAF an ear full.

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I need to print out that pic and take it to work. Last week we had a guy doing a preflight and crank the APU, with plugs in. A buddy and I saw it and ran over and asked him what the **** he was doing. When we brought up the plugs his answer was

"But I'm not turning the AC on."

Other peoples kids, I tell ya.

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Does your aircraft have a check valve (flapper) installed at the top of the trouser leg?

That valve prevents pressurisation leakage following a system failure, but if it sticks it will impede airflow in both directions.

You may have to slip some internal ducting loose to look back toward the wheel well bulkhead to determine if you have the valve and if so whether it is stuck.

Bob M

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