November 5, 2012 at 8:51 pm #83936dstefkoParticipant
I have been reading up on this exhaust AD including one of Tony Saxtons articles. Currently looking at a 1976 340 that according to the logs will hit the 12 year requirement in December 2013. Does anyone have any experience with the cost associated with the inspection and if replacement is necessary, that cost?
DaveNovember 6, 2012 at 2:40 am #97044quote dstefko:
Yes… Pipes, slip joints aft, sent to Knisely Welding. Needed one new-style, round exhaust stack for $800.00. Cost was around 9k. I had the turbos and pressure relief valves overhauled by Main Turbo for an additional 9k. Roughly speaking, it was an 18k project. But, my 12-yr AD is done and I’ve got fresh turbos. Engines are next 😯
I can pull out the receipts, but the 18k sticks in my retired mind 8)
ps mine is a small, low cost shop… YMMV.November 6, 2012 at 4:44 am #97045quote dstefko:
Dave, is it in the initial compliance period for AD 2000-01-16 part (g) or recurrent? See this letter too: https://www.twincessna.org/Documents/AD%202000-01-16.pdf
It is possible it is still in the initial compliance time and therefore exhaust removal/inspection would not be required until engine overhaul. Unlike all the others (g) is written as whatever occurs later.
At 12 years, I would take a close look at fluid hoses + vac hoses. If not changed recently I would strongly suggest getting them replaced (at least fuel and vac). Cessna could have save everyone a bunch of risk by running longer hoses better shielded and farther away from the exhaust. It works, but I think it is one of the weaker design aspects on what is generally a well thought out design.
I went with the higher temp (teflon) hoses at annual.
EricNovember 20, 2012 at 4:21 pm #97137
This AD is difficult to interpret. I am in the middle of this AD nightmare on a pre-buy right now. Between the IA and the FAA, it turns out that the language is misleading. According to the FSDO, once you start the repetetive inspections, the 12 year clock starts ticking. As a result, the airplane in pre-buy has one side due now and the other due in a couple months. The estimate I have for a 421 is 10 hours shop time and $5,200.00 parts per side.
The seller and I are not able to come to a number that we are both satisfied with, since technically, one side is not currently due. But it is a looming $6000 bill.November 21, 2012 at 4:46 am #97145quote tallen:
Well, regardless of the AD or not it is a good idea to have them checked. Did they agree to cover one side? If you hold them off a couple of months then both will be due…. I would compile a list of the exhuast parts on the plane and when they were replaced. The old style slip joints should be replaced regardless (not that expensive). What is the condition of the turbo’s? It might make sense to overhaul these too – at least the gaskets much be replaced.
Will they meet you half way on the 6k? How good is the deal overall?
EricNovember 21, 2012 at 1:56 pm #97147
They have no problem with the side that is due now. I may be able to get them to come up a little more.
This is a trailing link C model and is in very good condition. No corrosion, NDH, etc. there were only minor squawks found, other than the AD. The 800B has some issues, so we would have to send it out. Nice clean airplane, but I am paying for that. The aquisition cost is definitely on the higher end of the market, but my search has shown me that clean, well maintained 421s are hard to find. And those airplanes are usually owned by somebody that doesn’t need to sell.
As of right now, the seller has canceled the sale and elected to have the annual finished.November 21, 2012 at 8:04 pm #97149
Tom, what are the 800B issues? I learned a lot working with shops on my 800B
EricNovember 21, 2012 at 8:17 pm #97150
While tracking a GPS course, it would fly through it. The heading bug was still active, even though we were in GPS mode with HDG off.
A fuel imbalance would cause a drift off course.
The yaw worked, but seemed weak.
Elec. trim thumb switch failed to disengage A/P.
I am going to send the box out. That will be a good starting point.
We are set to close Wednesday. 8)November 22, 2012 at 6:13 am #97152quote tallen:
That’s great on closing, glad you reached an agreement. If you are doing the exhaust I also suggest redoing the vacuum lines in the engine compartment (maybe 200 or so per side). These take a beating next to the exhaust. Also the fuel inlet and return hose, and the left engine fuel controller to spider hose. I have these parts numbers somewhere. About $200 per hose for the nice teflon ones with integral firesleeve.
Easiest way to test the yaw system is activating it while taxing. If you don’t notice, it’s not working. 🙂
trim switch could be wiring? Does it release when you press the test button?
Before you send the box off, call Autopilot’s central. They may have some tests for you do to with the box in your plane that could save you a fortune.
The mode selection box is marked NAV and HDG? How did they wire it up with the GPS? Did it ever work with the GPS? Does it work in NAV mode tracking an ILS or VOR but not in GPS mode? I ask because it also could be how they wired it. The 800B predates GPS, so usually the GPS mode is fed in thru a NAV mode (similar to how the GPS and HSI interact) However, I understand not all were wired correctly. There could also be some sticking relays between HDG and NAV? Autopilot central will know.
Another test you can do on the ground is set it to HDG mode and observe any offset between the HDG set and what the AP trims for, the whole thing is analog genius – but sometimes that means you have a couple degree offset between what the HDG bug is set to and what the AP is driving for.
Everything is inter related in that computer box so don’t let anyone mess around with it unless you are convinced they know what they are doing as the full adjustment procedure is very long. My local shop would help with troubleshooting only.
From what you described it does not sound so bad. you could also have your shop inspect the computer for water damage. I understand that it can “rain” in the tail with condensation from above. Doesn’t help that the hot and humid cabin air is vented into the tail area… (This can condense on the cool ceiling of the tail and rain down on hardware – the computer being the most critical. I think there was a SB to relocate it somewhere else (probably no longer available)
Honestly, the 421C is a great plane to hand fly and trims out very nicely. Aside from IMC (which you typically will not be in for long), it is not as essential as it might initially seem.
Congrats, fly safe and have fun!November 22, 2012 at 3:20 pm #97155
The yaw damp works, but not well. Test flight day was very turbulent with a frontal boundary on top of us. I really don’t know how the interface is set up and trying to examine the equipment on a crappy day and dodging inbound traffic made for a less than perfect test environment.
The shop I use operates a few 400 series Cessnas. They recently were not pleased with AP Central on a 800b repair. They resent the box back out to Duncan. They found several defects that were missed by APC. Needless to say, they are recommending I use Duncan.
Thanks for the other suggestions. I will speak with mx to make sure those lines and hoses were checked.
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