KA 200 pressurization/heating issue

[Luap]

Hey guys. Im looking after a early model ka200 with -41s where the max diff is intermittent flight to flight. One flight it will be 4.8 or lower max diff and the next will be 5.8. I've pressurized on the ground and checked for leaks....there are some but leaks dont turn on and off and its got the new style metal flapper T in the ducting. Also the heating is a little on the cold side. Is there some kind of temp sensor on the flow packs that can limit air to the cabin. I'm trying to figure out if the heating and pressurization problems are related. I only have time to look at it a couple hours a week so any help would be awsome!

[impress]

If you can get 4.8 my thought is that you do not have a flow issue, you have a leak. Intermittant leak? check door seal.

Heat issue:

Again if you have 4.8 diff, not a flow issue. Ducting? Is it Medical interior? blocking outlet? Not sure on that one.

[torquey401]

Check the flow packs and more importantly the ambient air mixing components. You may want to check that the bypass valves are in good condition.

[Tiger Moth]

I have dealt with almost an identical snag and it turned out ours was a leaky fuselage. In the AMM Chapter 21 there is a flight test procedure that will likely point you towards that as well. I bet your varing max diff will change based on outside air temp, altitude (better up to about 16000, then worse, then better after 21000?) and power settings. As to the heat issue, are both of the butterfly valves in the wing centre sections working properly? Or possibly a clamp there is loose, that has affected our machine and gave it a low psid as well as cool air issues. Lots of times with pressurization it turns out to be a bunch of little things adding up.

As to a temp sensor, on the firewall by the intake of the engine is a small temperature sensor. This controls the ambient air valve on your flow pack. Again in AMM Ch 21 there is a chart for the resistances on this thing, but in my experience they fail open or shorted, not "out by a bit". If that failes it messes with the amount of ram air that the flow pack allows in to mix with the P3 Air.

PM me if you want some more

~Tiger Moth

[maigashi]

A couple of things worth noting or trying.

Simplest solution, sometimes the outflow valves get sticky or residue on the seat of the valve, clean and reinstall. Sounds stupid but you'd be amazed how often this is the culprit. Often manifests in erratic pressurization. Can also check the drain valves on the piping to the outflow valves (beneath floor behind copilot usually. Water in the line also creates erratic control

Verify that your heat exchanger bypass valves (stub wing) are working (noise and you can see the arm move) One closes than the other does and vice versa. I think the whole procedure takes about a minute, 30 seconds a valve. Second is that sometime in the flow controller, the jet can get obstructed and you will get restricted flow sporadically. Best way to test this is if they have an empty let get them to try pressurizing to max on both sides separately (normal safety procedures apply) and see if one side is weaker than the other.

I would assume weak flow is the culprit as the heat is low, assuming you are in the winter as we are this is usually the problem. Cold fuse from a single pack or pack and a half. Like the moth says though, most likely a combination of items, king airs don't break, they just get ornery.

If these don't work let me know, got a million more solutions to your problem.....
Daniel

[teh_flyguy]

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[maigashi]

How did it turn out for you?