All about Cessna 310s

Discussion in 'Flight Following' started by flyingcheesehead, Mar 15, 2019.

  1. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    We got to talking about this on another thread, but @MIFlyer suggested that I post my "brain dump" on 310s that I wrote up for my airplane partner, rather than wait for @Ray Jr to start a thread about it. I'll keep the first post edited with any other information that is added/corrected.

    This information was gleaned from conversations with @Ted DuPuis, some of the great info in Twin Cessna expert Jerry Temple's "Temple's Tips" (there's a lot of info on the other Twin Cessnas there as well), The Twin Cessna Flyer's 310 prospective buyer page, reading the POHs (I posted a 310R POH PDF here), and lots of Googling and reading other articles from around the web. So, here goes:

    The big split in 310s is the long and short nose varieties. Only the 310R produced from 1975-1980 had the long nose with baggage compartment. Between aft baggage, nacelle baggage, and nose baggage, you can haul a lot of stuff AND a lot of people. Useful loads are in the 2000-pound range, with maximum tankage being about 1200 pounds of fuel, so you can pack 800 pounds of people and stuff into it and go for 8 hours to dry tanks at around 185 knots. Without any nacelle tanks, full fuel would give you a payload of about 1050 pounds and enough fuel to go for a solid 6+ hours to dry tanks.

    Fuel tanks:
    The tip tanks are the mains on ALL 310s, and were always 100 gallons regardless of their shape. Early 310s had “Tuna Tanks” - They kinda look like fish on the wingtips. Starting with the 1962 310G, they moved to the modern “Stabila-Tip” tanks. (Gotta love Cessna’s marketing jargon.)
    Wing aux tanks became available in 1958, and most planes were equipped with them. They held 30 gallons from 1958-1966, then 40 gallons from 1967-1972, and for 1973 and later could be either 40 or 63 gallons. The aux tanks are directly selectable, but the overflow from the fuel divider always gets pumped back into the mains. So, you start, take off, climb, and land on the mains, and the initial part of cruise is on the mains as well: 60-90 minutes at the beginning of flight must be on the mains, 60 minutes for the 40-gallon aux tanks or 90 minutes for the 63-gallon aux tanks), to make room in the main/tip tanks. At that point, you can switch to the aux tanks, and while you do burn fuel direct from the aux tanks, the mains will re-fill from the overflow line off the fuel divider. So, once your aux tanks are empty, the mains will be full again.

    Finally, starting in 1968, nacelle locker tanks became an option. The nacelle tanks are accessed via transfer pumps that push the fuel out to the main/tip tanks. There may be one or two nacelle tanks, 20 gallons each. You burn the mains down to 180 pounds (30 gal) per side from 50, and then start the transfer pumps. The transfer takes ~75 minutes for the 20 gallons, so about 16 gph per side. There are also aftermarket nacelle tanks that are 18.5 gallons each that can be installed both where the factory put theirs AND in the nacelle baggage compartment, so you could potentially have up to four nacelle tanks with the aftermarket variety, for up to 240 gallons total fuel.
    Where it gets weird is if you have a nacelle tank only on one side. For this example, let’s say you have a nacelle tank only on the left side. You start heavy on that side to begin with unless you put something in the opposite wing locker, and when you start the fuel transfer that wing gets even heavier because you’re pumping the fuel out to the tip. Plus, there’s less fuel on the other (right) side. So, you have to crossfeed with the right engine, which lightens the load in the left tip AND puts overflow fuel into the right main, which helps balance things out. But, since you’re crossfeeding, you’re burning fuel out of the left tip at a much faster rate than the transfer pump is putting it back in. So, say you burn the mains down to 30 a side and you have 20 in the left nacelle, then you start the transfer pump and switch the right engine to crossfeed, after 75 minutes you’ve emptied the nacelle tank, which would put 50 gallons into the left tip if you weren’t burning anything, but you’re burning 25 gph all out of that tank so you’re down to about 19 on that side, except with the fuel divider thing you’ve actually pumped one engine’s worth of overflow fuel back into the RIGHT tip, which still had 30 gallons in it when you started crossfeeding… Confused yet? You kinda have to crossfeed just part of the time, but I haven’t figured out exactly how much that would be to avoid creating an imbalance. I think that particular configuration is the one that has given Twin Cessnas a bad reputation when it comes to fuel management.

    Seats and Baggage:
    Early models were four seats. Six became an option with the 310G in 1962, but at that point the 5th and 6th seats took up the entire baggage compartment (seat backs are up against the wall in front of the hat rack). The cabin was lengthened and moved the last row off the aft bulkhead sometime between then and 1973, quite possibly in 1971 when the Q model, S/N 400 and up, also gained a rear window. It appears that the R model may have lengthened this portion even more. (?)
    So, aft baggage with six seats was no bueno for a while… But, nacelle/wing locker baggage compartments were added in 1964 with the 310I. Those have a limit of 120 pounds each, or 40 pounds if a nacelle tank is installed as well. Without a tank, the dimensions are 50” x 25” x 8” or about 3 golf bags per side. (For six seats… Hmmm.)
    The final model 310R extended the nose a whopping 32 inches, adding a huge nose baggage compartment with 350-pound capacity. So, the R model has aft, nacelle, and nose baggage.

    Engines:
    The 310s came from the factory with either an IO-470 variant at 260hp/side and a 1500 hour TBO, or for the R model, an IO-520 at 285hp per side with a 1700 hour TBO. The 470-powered ones came standard with two-blade props, the 520s (including the turbos) with three-blade.
    The 520s have a bad rep in many installations which is mostly undeserved - It sounds like if we run them at 65% all the time that they should last just fine. Turbos became an option with the 1969 310P, and all turbos had 285hp TSIO-520s with a 1400 hour TBO. TBO is kind of meaningless in the real world, but when you’re buying and selling it’s a factor.
    Both Colemill and RAM did engine upgrades. Colemill did the “Executive 600” upgrade which basically puts the R’s IO520s on the older short-nosed 310s, plus 300hp available for 5 minutes. For the R model, they did the “Bearcat” conversion, which replaces the R’s normal IO-520s with 300hp IO-550-As. Put those on the short nose and it’s the Executive II. You can still do these mods, but it’s not really worth it - They’re in the $130K-$150K range, and while that does include engines, that’s an awfully spicy meatball unless you already need two new engines! The Colemill upgrades have a 1900-hour TBO.
    RAM Aircraft does engine mods and other work on most Twin Cessnas. On the 310, they only do the turbos, and the “RAM I” mod ups it to 300hp/side while the “RAM IV” ups it to 325/side. (I bet that’s fun on takeoff, but not so much at the fuel pump).

    Turbos:
    They didn’t put turbos on the 310 until the 1969 P model. The good thing is that they’ve got automatic wastegates. The bad is that they’re hard-mounted and thus subject to a lot of vibration, so it sounds like they can potentially be a maintenance nightmare. There’s also an exhaust AD requiring an inspection every 50 hours on the turbo models. One source said that 2/3 of the final year of production 310Rs were turbo.

    Robertson STOL:
    This system basically replaces the 310’s stock split flaps with nice Fowler flaps. Vmc is lowered, accelerate-stop distance is drastically reduced, ground roll is shorter, and it sounds like this mod can really increase safety margins. However, it’s not well supported. Robertson went out of business and Sierra Industries bought the STCs, and while that company still exists, but they mainly do Citation maintenance now.

    De-ice systems:
    There are at least two possibilities. FIKI certification wasn’t available until 1977, and that system has wing boots both inboard and outboard of the nacelles, tail boots, hot props, and a hot plate on the windshield. But, before that there was a system with only the outboard part of the wings booted, tail boots, hot props, and an alcohol windshield. That system is pretty well regarded too, but not officially approved for flight into known icing. The hot plate on the FIKI system is supposed to be very expensive to repair or replace, too (10 AMU range).

    Other options:
    A/C:
    It sounds like the Cessna factory AC is crap. Mechanically driven and hard to find parts for. The factory AC requires the right engine to be running, and precludes having a right-side nacelle tank (and probably shrinks the baggage compartment on that side, though I couldn’t find anything saying so). There is an aftermarket system that is considered to be better (“Keith A/C”) that is electrically driven and supposedly reliable. The Keith system is fully electric and thus can be plugged in and run on the ground prior to engine start.

    Vortex Generators:
    These are pretty much a must-have, conferring at least some of the benefits of the R/STOL only with no moving parts and way cheaper. Kits are still available (from Micro Aerodynamics, BLR, and Knots2U), and they can be installed in less than a day for about 3 AMU, so well worth doing if you find a plane without them. Gross weight is increased by 150-180 pounds, Vmc drops nearly 10 knots (and is only 2 knots above stall in the landing configuration), takeoff speed also drops 10 knots, etc… It’s an excellent performance improvement. More info here: https://www.avweb.com/news/reviews/182564-1.html
     

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  2. JOhnH

    JOhnH Touchdown! Greaser! PoA Supporter

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    Thanks for the write up. A friend of mine just bought a 310R. Now, we won't have to take two airplanes when we go on vacation together. My Bo won't hold the four of us with luggage and fuel.
     
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  3. James_Dean

    James_Dean Pattern Altitude PoA Supporter

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    They’re just sexy. There are days I wish I still had mine.

    C9375346-DFE6-4A44-9B33-F43EE55804C8.jpeg 3D4D9F4F-3F83-432C-A393-5035B356A817.jpeg 67A20FAE-1160-41B3-9F2A-707A798B04C3.jpeg 8AB13F2D-0DA7-4256-9DAB-5251A8E1F105.jpeg 4DF58228-88C6-4415-8FB6-290A51D1AFB4.jpeg
     
  4. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    She's a beaut. If you ever go back in time, can you hang onto it until I'm ready to buy it? As I recall, the panel was very nice as well.
     
  5. James_Dean

    James_Dean Pattern Altitude PoA Supporter

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  6. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    Nice. What are the two little red numeric displays above the PFD?
     
  7. Eric Stoltz

    Eric Stoltz Line Up and Wait

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    That fuel system sounds like a Monty Python skit...and much like Concord's fuel system. 17 selectable tanks, numbered 1 through 11.
     
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  8. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    It's actually not that bad at all - You just have to understand it. With the exception of the 183-gallon system that has a nacelle tank on only one side, it's pretty dirt simple, you just have to make sure there's enough room in the mains that you're not pumping fuel overboard.

    If you have the 203-gallon system, you take off on the mains and empty some space out, start pumping the nacelles into the mains, open up some more room in the mains again, switch to the auxes, and then back to the mains for landing. Not at all unusual, really. But then, I'm a guy who likes a large fuel capacity and isn't afraid to switch tanks now and then. I always thought it would be fun to own the pond-crossing Twin Comanche that had main, aux, secondary aux, tip, and nacelle tanks. ;)
     
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  9. MIFlyer

    MIFlyer Line Up and Wait PoA Supporter

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    wow, great write up Cheesehead. Seriously, this is the kind of knowledge that's impressive to have. does the exhaust AD apply to the non turbo models?

    Have you sat inside one? how does it compare to an Aztec inside?
     
  10. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    Thanks! I like to research things in pretty good depth before I buy.

    I don't believe so. I didn't go as in depth on the turbo models because we'll likely be holding off on turbos until we can get pressurization too.

    I have sat in both, but @Ted DuPuis should be the one to answer this, as he's owned both and flown them for hundreds of hours apiece, including owning both at the same time!

    I will say that both are very roomy, and IMO the view out of the 310 is better because of its flatter, lower engine nacelles. In the Piper twins, you tend to feel like you're sitting down in between the nacelles, while in the 310 they're quite a bit lower relative to your eyes. Because of that, and the significant speed difference between the two on about the same fuel burn, means that the 310 is a much more desirable bird, to me.
     
  11. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    That was a great airplane.

    Spent about 1,000 hours in each of those two.

    The Aztec is larger and more comfortable. Wider and taller, more legroom as well. Easier to get in and out. The 310 is still plenty comfy and bigger than a Baron (or about any piston single).
     
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  12. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    310s do have a much better exterior view. The exhaust AD does NOT apply to naturally aspirated models.

    Do not buy a turbo model. My 2 cents.
     
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  13. ZeroPapaGolf

    ZeroPapaGolf Line Up and Wait

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    RPM and MP fed from the JPI.
     
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  14. Arbiter419

    Arbiter419 Cleared for Takeoff

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    Great writeup! Sounds like the naturally aspirated R is the bees knees. Although I absolutely love the look of the short nose tuna tankers and I reckon 300 horse per side for 5 mins on one of those old light airframes would be a fun time. Sky king!
     
  15. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    A short nose with 520s or 550s is the most fun of the 310s.
     
  16. James_Dean

    James_Dean Pattern Altitude PoA Supporter

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    But I want a Ram IV. :rockon:
     
  17. James_Dean

    James_Dean Pattern Altitude PoA Supporter

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  18. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    The previous owner of Cloud Nine's 310 replaced it with a T310R, and had the RAM IV upgrade done to it. I got to fly it a few times. It's a hell of a performer, basically lower end turboprop performance out of a piston. That said, he and I both thought in a lot of ways the old 310N was a more fun plane.
     
  19. GRG55

    GRG55 Final Approach

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    LOL. I have 188 gallons and don't have to pump anything anywhere, other than directly to the engines. Dead simple, an inboard and an outboard in each wing. Two position fuel selector. Have to work very hard to goof up.
     
  20. mwagg737

    mwagg737 Pre-takeoff checklist

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    She only holds100 gallons, but makes up for it by being sexy; my 310.[​IMG][​IMG]

    Sent from my Pixel 2 XL using Tapatalk
     
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  21. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

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    The Twin Cessna fuel system does require management, but if you’re flying long enough to use it all then you’ve got time to think about it. That said it has some pitfalls, most notably that you have several failure modes where you can have fuel starvation with many gallons left on board. @James_Dean experienced one. Two others include the nacelle tank pumps freezing up and losing prime (you should prime them on the ground if you’re going to use them) and if you lose an engine with fuel in the wing tanks, the fuel on the dead engine side is unusable. It is a sub-ideal setup but in a couple thousand hours of flying it the primary issues I’ve had we’re forgetting to switch back to mains (that causes a temporary engine failure) and I had the transfer pumps on the 414 froze up sometimes if I forgot to prime them on the ground.
     
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  22. kep5niner

    kep5niner Pre-Flight

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    dsc_0268.jpg

    upload_2019-3-16_22-48-39.jpeg

    Ok I’ll play. Love the short nose, and very happy with the IO470. In the shop now for annual and panel work, and looking forward to getting it back! Paint scheme matches the boat too.
     
    Last edited: Mar 16, 2019
  23. KaiGywer

    KaiGywer Pre-takeoff checklist

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    And they make for a good YouTube platform :p Just ask @Radar Contact
     
  24. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    To be fair to the 310, a busted fuel selector when you're trying to switch from a nearly-empty tank is going to mess up any airplane. Only having an engine-driven pump on the aux tanks is a potential weakness, though.

    How exactly do you prime the nacelle pumps? Just run them for a few seconds? How can you tell if that was successful? Also, why would it work on the ground and not in the air? If it doesn't work when you try to prime on the ground, is there anything you can do to make it work?
     
  25. flyingcheesehead

    flyingcheesehead Touchdown! Greaser!

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    That there is a very nicely updated classic 310!
     
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  26. GRG55

    GRG55 Final Approach

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    There is quite a difference in the visibility between a Piper Seneca and a Piper Aztec. The Seneca, with it's Continental engines, has noticeably more bulbous cowlings. The reason for this is the intake manifolds for the Continental IO-360 engines are above the cylinders, unlike the Lycomings in the Aztec (see pics below). Combine that with the seating, which in the Seneca is typical Cherokee heritage and low to the floor (as @flyingcheesehead noted) than the higher seating position in the taller cabin Aztec. The combination makes quite a difference between these two Piper twins.

    Continental 360.JPG

    Seneca Cowlings.JPG
     
  27. Ray Jr

    Ray Jr Filing Flight Plan

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    Hi FCH, Thanks for posting! I got distracted!
     
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