Anybody know a source for an overhauled outflow valve? A new one from Cessna is about $18,000.

Chris Short at Yingling always gives me the Cessna quote and then a much lower where he was able to find it. I had to replace a battery last month, Cessna quoted $6k and he found one for less than half. Also, a great guy.

cshort@yinglingaviation.com
316-841-1444

Ahhh, the conquest flow pack. That is one expensive component. You have a few options. First, you can shop around for an overhaul exchange unit. Cessna has them and those are the most expensive. The you can try someplace like Technicair in Fresno. Bruce Rayner almost certainly has one on the shelf for probably in the neighborhood of $15K. Next, if you can wait then contact Ontic directly and send it in for overhaul. They take 3-4 weeks and their customer service sucks, but the cost is more like $10K. Make sure you buy the silicone o rings for when they send back your $10K valve less o rings... You can also ask them to repair your valve if it is not too old. In other words, if it has been overhauled in the last few years you might get Ontic to agree to a repair vs a complete overhaul which will be cheaper still.

What's it doing? Is it the pressurization shut off valve not closing when the source selector is in the off position?

Thanks Scott. No, my problem is not with the flowpacks, although I did have to replace one a year ago ($15K). I have three problems:
1. Can't get to max diff of 5.0 - only about 4.7. Makes for cabin alt of 10,000' at FL250.
2. Can't get less than 550 fpm rate of descent of cabin alt when descending.
3. When initiating descent, even slowly, cabin rate blows down to 1500 fpm then slowly recovers back to 550 fpm.

I sent the controller in for overhaul with no change. I swapped outflow valves with a 414A with no change. Had plane connected to huffer cart and leak checked. No change. Pulled vacuum to check lines from controller to outflow valve - all good, no change. Double-verified good flow from both sources/flowpacks - No change.

Now we're sending back the controller plus the outflow valve and the safety valve to have the entire system checked. See if that helps. I'm running out of ideas.

My WAG is keep looking for a cabin leak versus a mechanical malfunction. I think you have a some seal or hose that is fine on the ground with the huffer cart but leaks in the air.

Did you retract the gear with the cart attached?

You may need to search for the leak in the air. Have someone in the cabin with an incense candle where you can see the smoke. Go around the cabin with it and look at what direction the air is flowing. Anything other then back to the outflow valve indicates a problem.

If you turn off the bleed air sources in the air with the cabin pressurized what speed does the cabin climb at?

Turn off the bleed air with the Cain pressurized in flight, which should totally shut the outflow valve, and use the smoke candle to see where the air is leaking out from.

With 2 & 3 do I assume you pulled back the power? If you descend without pulling back the power does th cabin hold altitude?

Ken Blow helped me a lot with the safety and outflow valves in my 58P. Don't know if they are the same but maybe worth a check.

Kadex - (888) 523-3988

Good luck

On the conquest how is the controller connected to the outflow valve?

Is it electrical or is it pneumatic?

If its pneumatic I'd check to make sure it was clean and clear and had
not water dirt or other contamination in it.

Vacuum line. OP said "Pulled vacuum to check lines from controller to outflow valve - all good, no change."

I think you can observe the outflow valves if you fly with the rear bulkhead removed. If you can fly with an observer watching the outflow valve you can see if it is fully closed when the cabin is descending. Which would indicate the air is leaking from somewhere else.

I'm pretty sure it's not a cabin leak. I took it to a Citation shop in which it was fully inflated. No, they did not retract the gear but he did say I had a "tight" cabin.

Yes, I guess I could pull the rear baggage floor panels and actually observe the outflow valve in flight. Never thought of that.

Hey John,

Sorry I re-read your post and noticed you said outflow valve, not flow pack. I don't know why I mixed those two up. Anyway I just got back from my recurrent training today at Proflight and my classmate has a 425 that does exactly what you described - the cabin initially descends at a very high rate and then recovers to around 500 fpm. The instructor said it's the controller and he had the name of a place in Sparks, NV that works on them. I'll get the name and reply back. I like your idea of sending off the whole system to have it checked. I think the key is to find out if the outflow valves are fully closed or not. If they re fully closed then either you have a leak or insufficient flow from the flow packs. If they are open then it's a problem with the valves, controller, or plumbing.

Here's something you can use to check the outflow valves and yes if you pull the rear panel you can see them easily in flight.

https://www.grainger.com/product/MSA-Pl ... moke-6BU78

Here's a shop that does pressurization component service that I've heard is good: http://www.powerpacksplus.com

Awesome. Thanks Scott.

Sure no problem. The other thing I would say is that Bruce Rayner at Signature Technicair will find the problem. He's in Fresno, CA and I know that's a long way from Texas but if you are in the area he can find and fix any issue with a C425. There's no problem he hasn't see on that airframe 1000 times.