19 Apr 2024, 13:01 [ UTC - 5; DST ]
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Post subject: Re: What do you know about the Cessna 421C  Posted: 01 Mar 2022, 10:16 |
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Joined: 10/24/19
Posts: 145
Post Likes: +38
Location: Central NY, (N03)
Aircraft: 421C
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Hi Don,
Its just more convenient to have the inspections done every 40 hrs at oil change, while my mechanic already has the cowls off. My thinking is that the FAA won’t object to me having them done more often than they require.
John
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 10:23 |
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Joined: 02/17/10
Posts: 600
Post Likes: +822
Company: JCrane, Inc.
Location: KVES
Aircraft: C441, RV7A
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Username Protected wrote: There are a also a few AD’s to be considered - one is the exhaust, even for 91 operators. Inspection every 50 hours and replacement every 12 years. This was something I didn't know about the 421's. So if you're on a 40 hour oil change schedule and 50 hour mandatory exhaust inspection, you're doing (2) shop visits every 50 hours?? Ugh.
Yes, but the 50 hr exhaust insp is a very simple inspection; just give it a thorough visual look-over, which would include a mirror and a flashlight. The 421 exhaust system is short & simple (doesn't disappear into the wing structure and reappear out the back as some of the twin Cessna do).
So, any mechanic can do the inspection (whoever is on the field), nothing much to be gained by using a 421 guru.
I do it myself every oil change (25 hrs) just because, but let a mechanic look at for the log entry every 50.
The cowling must be removed to see everything, so all told this inspection takes maybe 1/2 hr.
The twin Cessnas developed a bad reputation for defective exhaust systems setting the wing on fire, hence the intense focus on exhaust inspections.
G Stull
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 10:50 |
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Joined: 10/24/19
Posts: 145
Post Likes: +38
Location: Central NY, (N03)
Aircraft: 421C
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Hi Gary,
I thought that I was being conservative at 40 hrs, but I see that you’re doing them @ 25..! Am I not being conservative enough? Should I be doing them more often in your opinion or do you just prefer the oil to remain fresh??
John
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 12:13 |
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Joined: 10/04/19
Posts: 653
Post Likes: +400
Company: Capella Partners
Location: Alpine Airpark, 46U
Aircraft: P35, TW Pacer
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Username Protected wrote: Hi Gary,
I thought that I was being conservative at 40 hrs, but I see that you’re doing them @ 25..! Am I not being conservative enough? Should I be doing them more often in your opinion or do you just prefer the oil to remain fresh??
John Depends on frequency of flights. Rule of thumb is that if you are flying more frequently, you get to stretch those hour intervals since they're over a reduced calendar. -J
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 14:45 |
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Joined: 08/05/16
Posts: 3109
Post Likes: +2225
Company: Tack Mobile
Location: KBJC
Aircraft: C441
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Username Protected wrote: True airspeed is not equal to ground speed if there is any wind.
Mike C. True, I was basing my comments on no wind
It should be wheel speed. What if the airplane is on a treadmill???
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 15:06 |
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Joined: 08/05/16
Posts: 3109
Post Likes: +2225
Company: Tack Mobile
Location: KBJC
Aircraft: C441
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Username Protected wrote: I'm surprised at the 421 costs being presented here. $750/hour? $50K/year maintenance? Wow!
Seriously, for that kind of money, or LESS, you can be flying turbine, and that's a whole different "plane" of existence than piston.
Turbine airplanes are better built, aren't being vibrated apart constantly, and simply don't break down. Mission reliability is a major benefit of turbine, perhaps more so than speed, even.
Mike C. Show me a $750/hr turbine that has: - 8 seats - 1,180 lb baggage capacity & volume - 1,200 mile range - a potty - $500k buy-in I think we've done this before...
Given the high price of 421Cs, some going for close to 7 figures, I think a 425 is a better buy.
Owning both a 340 and a 441, the 340 is constantly in the shop. We did an early annual this year to shift to the winter cadence, and in 7 months since last annual we have a two page list including a cracked oil cooler, broken heater combustion fan, broken prop de-ice wire, de-ice boot plumbing issue, leaking turbo controller, and dozens of other small items. We are not cheap and fix anything when it is broken, do oil analysis, heated hangar, and the plane does not sit. We're on week 4 of the annual. In the last year it has been in the shop for probably 10-12 weeks. This is with no big items like engine replacement (although we did replace a cylinder) and no significant paint/interior/avionics work.
We're new to the conquest and have been fixing every little niggle, but even so it has been in the shop less with the exception of the GFC600 install which was major surgery and took over a month.
A 425 is probably $400k more to buy, but if you factor in the downtime it's really not a big premium and per mile probably costs about the same part 91. 135 you have to overhaul the PT6s which are not cheap. If you just do HSI I'd bet they are cheaper all-in than the GTSIOs per dollar per mile, which offsets the higher hull value.
The only operational advantage a 421C has over a 425 is it is quieter, and the BS "handling fees" are less. People get scared over turbines, but the light turbines really aren't expensive at all when compared to the most complex piston twins.
If all my trips were less than 600 miles and they were personal trips where dispatch reliability didn't matter, and I had a shop on the field, I'd get a 421 since the buy-in is cheaper and it has jet-like noise levels. Other than that a 425 is the way to go. Or find a partner and buy both!
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 15:26 |
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Joined: 08/05/16
Posts: 3109
Post Likes: +2225
Company: Tack Mobile
Location: KBJC
Aircraft: C441
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Username Protected wrote: Robbie,
The geared engines don’t scare me. I try to baby them with smooth control and by being slow and deliberate with my power changes, especially reductions, (1” at a time), all in an attempt to manage the temps well. TIT no more than 1500 degrees. Using power until the flare prevents any backlash. I Change the oil every 40 hrs instead of 50. Occasional oil analysis (not every time). Mechanic cuts open and inspects filter. Just had the props and governor’s overhauled and dynamically balanced to reduce vibration as much as possible. Money in the bank, IMO.
John I don't fly a 421C, but have been to 2 twin cessna engine seminars, and the consensus seems to be as long as you aren't pulling power back so fast the props drive the engines no undue wear or damage will occur. The 441 (which obviously also has a gearbox) has an automatic system to prevent this, the 421 does not. I don't think any twin cessna has a TIT probe or published TIT limits. Most people with an EIS had the factory combined EGT probe stuck in the TIT inlet during install ("what should I do with this extra probe? Let's put it in the 7th input") so it's common to see people say they fly by a certain TIT, which is a meaningless number (measuring the 2/4/6 EGT a few inches past the #2 cylinder in a 340 and 414).
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 15:54 |
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Joined: 09/23/18
Posts: 130
Post Likes: +30
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Username Protected wrote: I do every 25 hours with filters every 50. you change your oil on your engines every 25 hrs? is that normal for a 421? i thought it would be more like 100 hrs?
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 15:57 |
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Joined: 02/17/10
Posts: 600
Post Likes: +822
Company: JCrane, Inc.
Location: KVES
Aircraft: C441, RV7A
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Username Protected wrote: Hi Gary,
I thought that I was being conservative at 40 hrs, but I see that you’re doing them @ 25..! Am I not being conservative enough? Should I be doing them more often in your opinion or do you just prefer the oil to remain fresh??
John Don't really know what's "best", but I do the oil changes myself, I enjoy doing it  , and the cost of oil & filter is insignificant. It is amazing to see the amount of crud in the bottom of the drain pan, after tipping it up to dispose of the oil in a large drum. Of course, I remove the cowls completely and do a thorough inspection of the engines, lube the waste gates, air the tires, etc etc at the same time. I nearly always find something that needs some extra attention... Non-turbocharged engines in our hangar have to wait 'till 33 hrs for their oil change. Again, for us, I enjoy the maintenance and the cost of oil is immaterial. G Stull
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 16:11 |
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Joined: 05/17/11
Posts: 1761
Post Likes: +1084
Location: KFRG
Aircraft: 421C
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Username Protected wrote: I do every 25 hours with filters every 50. you change your oil on your engines every 25 hrs? is that normal for a 421? i thought it would be more like 100 hrs?
There is no rule for changing oil on any plane. It all depends. For me, I do it myself. it's inexpensive, keeps my engines clean, takes about 30 minutes per side and I take the opportunity to look for leaks or any other possible items of concern under the cowls. I wouldn't go past 50 hours though; oil starts breaking down after the first start.
Anthony
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 18:41 |
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Joined: 07/06/14
Posts: 3008
Post Likes: +1993
Location: MA
Aircraft: Cessna 340A
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Username Protected wrote: I change my oil every 35 hours and do the inspection at the same time. The inspection is simple and takes about 30 minutes. FWIW, the AD estimates the part (b) inspection to take 3 hours. It's not just a visual once-over. It says to clean the components with a solvent, then dry. Remove heat shields, polish suspect surfaces with crocus cloth. Visually inspect the whole thing. Measure exhaust joint springs, then remove them, then measure them again, then reinstall them and measure them again.
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Post subject: Re: What do you know about the Cessna 421C Posted: 01 Mar 2022, 19:12 |
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Joined: 01/24/10
Posts: 6753
Post Likes: +4416
Location: Concord , CA (KCCR)
Aircraft: 1967 Baron B55
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Username Protected wrote: I change my oil every 35 hours and do the inspection at the same time. The inspection is simple and takes about 30 minutes. FWIW, the AD estimates the part (b) inspection to take 3 hours. It's not just a visual once-over. It says to clean the components with a solvent, then dry. Remove heat shields, polish suspect surfaces with crocus cloth. Visually inspect the whole thing. Measure exhaust joint springs, then remove them, then measure them again, then reinstall them and measure them again.
Show me that AD For the 421C? I have never seen or heard that requirement for a GTISO 520.
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