Can we get some free advice?

Home 2024 Forums Opening Section Maintenance Issues Can we get some free advice?

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      Looking for wisdom and advice to make sure we’re not missing anything.

      We’ve owned our 340A for 8 years and are delighted with it.

      We’re going into Annual in December. TAS annual in 2019, but we’ve used our local wizard (really a remarkable talent) since. But he’s only one set of eyes. Can you help us make sure we’re not missing anything?

      Airplane has 5,600TT, RAM VI 13 years ago and 1,300TSMOH, engines and props. FIKI airplane. Garmin 600, 750, 650, 345, 275, and TXi we put in 2 years ago. RAM gauges and FF. We fly ROP targeting 1550 EGT. AdLog. Put 80 hours on it every year for the last 8 years. 2 ATP pilots – 1 Army, 1 Navy. Hangared and we use oil pad heaters when required. Use 2-3 quarts between changes. We plan on running to TBO.

      All new hoses firewall forward last year, reasonable times on mags, alternators, vacuum pumps. Battery is 6 years old, but on a maintainer, and running strong. Oil changes every 40 – 50 hours. Blackstone analysis. Ram’s save-a-turbo every 50 to 100 hours.

      We use Cessna and Continental books and the TTCF annual checklist, and the Rig-it-Right gear CD.

      Here are some specific questions for the group:

      Does fume-proofing have a life limit? TAS put ours in about 500 hours ago.

      How long does a battery last, even on a trickle charger?

      We follow the guidance on the starter and gear, but I worry about it. Anyone do anything on those we should know?

      We NDT our torque tubes every year, which we assume have the TTAF on them. I’ve wanted to replace them IAW with bulletin, but this forum changed my mind. Busch’s article makes sense to me (said there has never been a gear collapse attributed to a failed torque tube). Other thoughts?

      Should we OH the props at 13 years old? No leaks. Boots work fine.

      Prop Sync is inop, but we don’t use it. Repair it?

      Heater Hobbs has 366 on it. We assume that is total time on it. Fuel servo replaced. Passes decay test no issues. Is there a life limit here anyone worries about?

      We have an air leak that I found out yesterday only lets the cabin pressurize to 3.1 max diff. We’ll find that. I’ve read all the posts on boots, and have the books to troubleshoot. Not looking forward to that.

      We want a new interior, but our local shop has a 2 year wait list. Anyone have recommendations?

      And most important – what else should we check or replace?

      Many thanks for all the expertise.



        Fly it more! Your fixed costs are eating you alive. $320 per hour for fuel and oil! Mechanics today can be as high as $165 per hour.

        The more you fly the better shape the airplane is going to be in.

        Keep’em flying



          Yep yep yep. Completely agree. We keep saying that. The airplane doesn’t like to sit, and fuel is the cheapest thing we buy…


            My 421c is at TAS right now. I just bought it four mts ago…second one I’ve owned…first experience with TAS (which is going great). For some perspective, my cabin heater had 1400 hrs and was working great. My limited understanding is that for 135 operations the heater has to be overhauled at 1000hrs. I figured if that’s the rule for 135 operations then I should abide by the same standards for me and my family. We went ahead and sent it out for overhaul which is about $8000. Yours sounds like it has pretty low hours.
            As far as your pressurization issues, TAS is great at tracking down all the gremlins.
            I can sync my props better than the prop sync on my plane but I’m the kind of guy that hates to have anything inop on my plane. When you go to sell it your inop prop sync will show up on prebuy and youll need to fix it….might as well fix it now.
            6 years out of a battery is great….you got your moneys worth. I’d replace it so you’re not stranded somewhere.
            Lastly, if you’re planning on going to TBO, I would have TAS pull a few lifters on each engine to look for spalling and replace as necessary.
            I know this reply is late….let us know how your December annual went.


              Hi John:
              Sounds like you are doing lots of things right. A few suggestions:
              1 Battery – Have them do a capacity test on it (start fully charged before putting it on the capacity tester) and if it doesn’t meet mfg specification, replace it.
              2.Magnetos – verify the magneto times and if they are close to 500 hrs just go ahead with the 500 hr inspection. I have been seeing a lot of crummy magnetos lately.
              3.Engine – your engine time is about when you start seeing worn out protocols. Download you engine monitor data and see if there is the spike pattern consistent with lack of valve rotation and especially if boroscopy shows any signs of assymetrical color pattern on the exhaust valves, replace the protocol on those cylinders.
              4.Are you doing Magnifluxing or dye-penetrant NDT on the MLG torque tubes every year. Magnifluxing seems like a bit over the top to me. Dye-penetrant is not so much. Careful pre-flight is a better answer and in line with Mike’s way of thinking about things. I think the removal, re-installation, and rigging from Magnifluxing has more potential for maintenance induced harm than good. (Just my opinion and I know this is a controversial issue).
              5.I would NOT overhaul your props at this time unless your airplane spends a lot of time outdoors in high corrosion environments. If all is well in that regard (hangared, non-corrosive sea-side environment etc) go a few more years then re-seal/IRAN the props. Every time you overhaul you loose some metal and after about 4 go-rounds the blades will be under-size and have to be scrapped. You will pass on the stress relieving process (sanding and shot peening) of an overhaul but re-seal/IRAN is a lot less invasive and you rule out the hub and blade corrosion that are the more common issues.
              6. Is your prop synch a Type I or Type II synchrophaser? Repairs on those differ.

              Just a few thoughts,
              Gary S. Silver, MD, A&P/IA, Avionic Tech, 28 year Cessna 421B owner Farmington, UT N678DB

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