C-130B Cargo Compt. Air Condition.

[jakesnk]

I am dealing with a lot of "low performance" problems with cargo compartment air conditions of old B models. And by "low performance" I mean insufficient airflow especially during colder settings(AUTO & Manual) and especially on the ground or low altitudes, causing discomfort to the crew and passengers during summertime(temperature regulation seems normal). The problem is the same both with engines and/or GTC supplying air. Things get a little better as the airplane climbs in a higher altitude. The air condition heat exchanger most of the times is found to be repaired or overhauled. Apart of the heat exchanger I think that the flow can also be affected by the shut off valve. Also no obvious leaks are noted in any case.

Not sure about pressurization issues, since we usually fly the B airplanes from FL100 to FL140.

We begun by replacing the water separator relief valve and bag, the shut off valve, turbine and after that the heat exchanger(repaired). No significant changes.

Since the B model heat exchanger is quite hard to find in the market and quite expensive, any other ideas about what could affect the air flow and the performance of the cargo compartment air condition?

[kersey9502]

The main components that affect flow are flow control valve (shutoff valve), heat exchanger, and turbine in full cold. You need to check the heat exchanger again. You can do this by gaining access to the duct that is coming out of the heat exchanger to the turbine ( usaully look like a J duct), you need to cap that duct off down by the turbine. What this does is force back pressure on the heat exchanger. while the heat exchanger is pressurized feel the exhaust nozzles and make sure that no exhaust is coming out. That will check the heat exchanger. If you have exhaust this is a bad heat exchanger.

[james]

Athens this time if year is fairly warm, and for the A/C system to keep that aircraft cold on the ground will be a full time task for a new A/C - let along a B model. A cargo full of passengers emitting body heat compounds the problem. If you're not sure about pressurization issues, especially at altitude, I would start by pressurizing the A/C on the ground. While the A/C is pressurized, do as Kersey0502 mentions check the heat exchanger. Another way to check the heat exchanger is - you'll get exhaust through the cargo compartment intake. Its been a long time since I worked on a C-130 - but I remember very vividly replacing a cargo heat exchanger (not my favorite task) on the Athens ramp. The heat exchanger I replaced was for pressurization problems, don't remember if low airflow was a complaint.

[MARS]

The 70 PPM C/C packs installed on the B/E/Super E aircraft are notoriously fickle and usually don’t work worth a damn… The problem may or can be one or a multitude of separate problems. I recommend you try the following:

NORMAL CHECKS

1. As stated by kersey9502; check the heat exchanger for leakage using the H/E Leak Check Fitting (in the pre-politically correct USAF referred to as the “donkey-dickâ€).

2. Verify the C/C FCV is opening as required:

a. If my Can’t Remember S#*T (CRS) isn’t too bad today; I believe with GTC/Air Cart the FCV should be almost fully open.

b. Again, if my CRS isn’t too bad today; during an Engine Run the FCV should modulate to maintain 70 PPM and the position indicator on the side of the FCV 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.

c. Also, check the FCV filter and all sensing line connections.

3. Pressurize the aircraft and ensure the C/C pack has no leakage while under pressure (even though you stated “we usually fly the B airplanes from FL100 to FL140†there still is a pressure difference affect on the C/C pack and on occasion leaks will show up under pressure that do not when unpressurized):

a. Ensure the AUX Vent Valve and UFH SOV are completely closed with no by-pass or seal leakage.

4. Remove the Turbine Ice Screen and ensure it’s not damaged or clogged.

“OUT OF THE BOX†CHECKS

1. Remove the Turbine and check the shaft for fwd to aft endplay. If any endplay is present it will cause the Turbine to “slow-down†by creating excessive friction between the shaft and bearings. This “slow-down†usually occurs before the Turbine can reach its optimal effective RPM and causes low flow and higher output temperature. If endplay is present; replace the Turbine (even if new or overhauled) as I’ve seen endplay cause the problem you’re experiencing numerous times, especially in hot environments such as SEA.

2. Check the Pant Leg Duct Flapper Valve to ensure it opens smoothly and fully. The easiest way to check it is to:

a. Drill a small hole in the Duct in the upper wing root area large enough to insert a long welding rod. Insert the welding rod and repeatedly move the Flapper valve through its full range of motion ensuring it opens fully and smoothly. If it’s okay, just seal the hole with fiberglass or epoxy. If it’s not okay, oops out comes the Pant Leg Duct…

Sorry if I was a little longwinded and hope this helps, though unfortunately low airflow and insufficient cool temperatures are the nature of the beast when dealing with the older 70 PPM C/C packs, especially in hot environments.

Regards

Edited August 28, 2012 by MARS
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