Peter wrote:
especially if you can tinker with the plane inside it… and park your car in it
Peter wrote:
Tinker – you can google it.You can easily save thousands by having a hangar where maintenance is permitted.
I did :
tinker –
noun
1.(especially in former times) a person who makes a living by travelling from place to place mending pans and other metal utensils.
2.BRITISH informal; a mischievous child. “little tinkers, we were”
verb
1.attempt to repair or improve something in a casual or desultory way.
So which of these would apply ?
Great that your ‘plane is flying again – on the pressurisation it would be interesting to understand what troubleshooting was involved, and what still needs addressing.
Well, we fixed what we thought were the major culprits:
Wing roots (where the wing meets the cabin – a classic leak point on Commanders).
Pedal and steering column boots (where they meet the floor and pressure vessel)
Windows and window seals.
This we thought would have taken care of it, but it has only improved it by about 1psi. We need another 1.2psi to be able to make full differential. Two other major leaks have been identified:
Turns out the floor, which is the outer pressure vessel on these, has a ton of leaks in the inspection panels. The floor has about 10 little panels you can open up to check the linkages below. They’ve mostly been sealed with gaskets that have been leaking, some with old crumbling cork gaskets. These panels need to be sealed with ProSeal – that two part grey gunk you seal tanks with. Why this wasn’t checked and done previously is one of the many reasons that mechanic will not work on this plane again. Also, the whole floor is covered in some old spray-on gunk of unknown variety, which I will need to scrape down to bare metal. In general, floor is in pretty bad shape, washboarded and just worn. Might be worth to just replace completely and make new. Take a skilled metal guy about 2-3 days to do, so not an eye watering cost. But I’ll see how bad it is when it’s scraped down.
Second is that many rivet joints in the skin leak between plates. We soap tested the aircraft and it comes out of many of them (see video). The old sealant has after the years dried and cracked and needs to be replaced. So now I’ll have to remove all the insulation from the entire cabin, then scrape, clean and use adhesive removers on the inside of each panel. Once that is done, re-seal with ProSeal and prime it. A time consuming job, but I will try to do this myself as the I know it will be done right. I don’t look forward to scraping the old stuff off, but hey..
I’m sure you know more about this than I, but my impression was that pro seal makes follow on maintenance, like opening the inspection hatches, difficult? Or am I totally off base?
Yes; it is very hard to remove anything stuck with PRC or similar 2 pack fuel tank sealant. I would use RTV732 which is the original silicone sealant i.e. sticks but not so well that you can’t get it off later. Or better still use the non-corrosive version, 3145.
The video says “unavailable”.
AdamFrisch wrote:
They’ve mostly been sealed with gaskets that have been leaking, some with old crumbling cork gaskets. These panels need to be sealed with ProSeal – that two part grey gunk you seal tanks with.
Um, well, are you ever going to open them up again for maintenance? In which case, why not replace the gaskets? Sounds like a much easier work too.
AdamFrisch wrote:
So now I’ll have to remove all the insulation from the entire cabin, then scrape, clean and use adhesive removers on the inside of each panel. Once that is done, re-seal with ProSeal and prime it. A time consuming job, but I will try to do this myself as the I know it will be done right.
Woha. Well, yes that is going to be a very time consuming job during which your cabin will have to be totally disassembled. I don’t envy you… And there’s me worrying that one day my tanks might have to be done…
You know what Adam, I am REALLY grateful to you for being so upfront with this and telling us all this. I have never yet had an account so compelling (with 3 subsequent airplanes too) and informative about what can (will) go wrong when taking on a project airplane, particularly if you are not aware it was a project in the first place. I do hope you will finally get it sorted out and enjoy flying it for a LOOOONG time before your next one comes along.
redRover wrote:
I’m sure you know more about this than I, but my impression was that pro seal makes follow on maintenance, like opening the inspection hatches, difficult? Or am I totally off base?
You can buy a low adhesion version specially made for inspection panels. It follows the AMS-3284 standard:
The more adhesive stuff, either with curing time of 30min or 2hrs, follows the AMS-S-8802 standard. There are multiple manufacturers of these various goo’s, PPG, Flamemaster etc.
That is brilliant Adam. I wish I had known about it for my TKS installation. I did the belly panels with RTV 732, to stop the fluid getting in there. But it’s messy stuff…
Peter, you have to be a little careful with silicone as the vinegar in it can cause corrosion, I’ve been told. I know there are silicones that don’t have that stuff in it as well, so best to use that.
