Seneca III operating cost

Good day. I am considering a seneca II o III and although I can find plenty of information on specs and capabilites, there is no information about what the operating costs are. Anybody that could have recent information or expirience on this matter? Kind regards.

Comments

  • There's not a real lot of difference between the II and the III, they simply improved the airframe a bit, but they re-vamped the paperwork on the engines to make the -KB. It is physically, no different at all than the -EB in the Seneca II. They just allow the governor to run at 2800 rpm for a maximum 220hp for 5 minutes, versus 2575 for -EB at 200hp take off power. The power setting tables were revamped as well, so in effect, what the III says is "75%" would be 82.5% power on the II, along with a much lower TIT limitation.

    The essence of this is that the III's -KB engine has paperwork available to let it run as much as 29gph and 165hp, versus 75% on the II at 23.6 gph. Basically, the II's 75% becomes 65% on the III.

    In reality, the cylinders on these engines don't last when run hard. It pays to be conservative on the Seneca II-V in choosing power settings.

    For my II:

    Figure per hour at 65%:
    Engine and prop overhaul reserve $45/hr
    Fuel 21gph $120 hr.
    Misc maintenance $10 hr
    So $175/hr in direct operating cost.

    Insurance is about $2400 yr
    hangar about $2640,
    annual inspection $2500,
    database subscriptions $800
    Property tax $1500
    = 9840

    Figure 10 hours per month for 120 hours per year to amortize fixed costs: $82/hr

    Works out to about $257 an hour. Probably not counting stuff like training and what not, but it will be thereabouts.
  • Thanks a lot for your answer. How come the gross weight in hte III is 200 lbs. higher than in the II? Is it true the III has a bigger wingspan?
  • The gross weight increase is probably all due to the extra horsepower. The real thing to look at on the II's and III's (and the IV and V's for that matter) is the Zero Fuel Weight. That's more limiting than the gross weight a lot of times.

    The III increased the ZFW by slightly beefing up the wing structures and attach points. Wingspan is the same on all PA34's, 38'-11".

    My Seneca II has a 1582lb useful load. It also has vortex generators, the STC allows a 168lbs ZFW increase.
  • So practically, the II with vortex generators has the same usefull load than the III. The only difference between the two is the 220 hp available for 5 minutes during takeoff. For the rest are the same machines. Am I correct?
  • The III actually does have a higher gross weight and a higher ZFW from the factory, a new instrument panel design and some other improvements over the II, so they tend to fetch a bit more on the market. The 20 extra HP is just really on paper for the most part. It is the exact same engine and propeller, just higher RPM limits and a new power setting table on paper.

    Here's the TCDS for the hard numbers:
    http://rgl.faa.gov/regulatory_and_guidance_Library/rgMakeModel.nsf/0/79578854d89e712286257209007693d4/$FILE/A7SO.pdf

    The Seneca IV are rare, not many were made, but very similar to the III in all respects.

    The V's have a very different engine from the same TSIO360 family and are still made brand new today. The downside is that the V is absolutely corpulent. Empty weight is often very high which leaves little useful load.
  • I sure wish my hangar was 2650 per year, try $6500 where I live and the 2500 for maintenance that is just the flat rate annual before things that are wrong. I must live in the wrong state.
  • hugounruh wrote:
    I sure wish my hangar was 2650 per year, try $6500 where I live and the 2500 for maintenance that is just the flat rate annual before things that are wrong. I must live in the wrong state.

    Actually, that's just for a covered shelter.

    My Cherokee 180 is in the T-hangar, at $570 a month. The T is not big enough for the Seneca's wingspan. Between the two of them, I've got annual hangar bill of almost $10, 000
  • larrysb2 wrote:
    For my II:

    Figure per hour at 65%:
    Engine and prop overhaul reserve $45/hr
    Fuel 21gph $120 hr.
    Misc maintenance $10 hr
    So $175/hr in direct operating cost.

    Insurance is about $2400 yr
    hangar about $2640,
    annual inspection $2500,
    database subscriptions $800
    Property tax $1500
    = 9840

    Figure 10 hours per month for 120 hours per year to amortize fixed costs: $82/hr

    Works out to about $257 an hour. Probably not counting stuff like training and what not, but it will be thereabouts.

    I agree with almost everything you say with my II except I think the $2500 for the annual is a little misleading. I pay close to that for the "inspection" (I pay $3300) but for the "ordeal" every year I've been averaging double that. So to get the out the door cost its been running me $6500 dollars per year. And my bird is a great running bird. Just with those two engines you usually get an exhaust leak here or some brake leak there, or oleos which need to be resealed. Something usually will put you in at around another $3000 per year above what they shop is charging for the inspection.

    As far as fuel burn i'm running on average around 23 gph but my engines are getting up close to TBO so that just may be them getting a bit tired.

    As far as engine/ prop reserve I think you are a little low also. Since my engines are getting close to TBO I've been looking at this pretty hard. I think you would be hard pressed to find an engine shop to overhaul the TSIO-360-EB's for anything less than about $38k and with the $5k or so for install your reserve just for the engine should be closer to $50/ hour.

    Anyway just some more numbers for you to check out. My numbers for everything else is pretty much the same. Out the door I'm looking at around $300/ hour when you add in oil changes and all of the misc mx.
  • Thanks for all the replys. Then it seems it is not as affordable as some people suggest. According to twin cessna org. the operating cost for a turbo c-310 the costs are similar and for a C-340 is around 350 to 380 US$. Could that be right?
  • Turbo 310? Oh, probably more than that per hour. They are very maintenance intensive and their bigger engines can burn a lot of gas.

    The Seneca II/III are more economical by quite a bit. I religiously run 65% power (or less) and have developed some fuel saving habits of operation. Fuel costs really dominate, if you are flying the plane at all.

    I separated my "investing" in the plane from my operations. Over the last 3 years, I've done both engines, props, landing gear trunions, installed all new avionics and windows. All that is left on my plane is interior and getting the autopilot fully working.

    The TSIO360EB is about $36k + shipping for a factory remanufactured engine (AirPower is where I got mine). The other was a field overhaul that I bought outright from a guy who's plane was storm damaged while the engines were off being overhauled. IF (big IF), you have the -EB (the B is important as it denotes an improved case) AND you have a VAR crankshaft, you can do a good quality overhaul for about $25k. You can do a quicky for about $18k. If you don't have a VAR crank, then the factory reman is your best option. The factory reman is a good deal because it comes with almost everything, exhaust, turbos, alternator starter, etc. All you need is the prop governor and it is ready to hang. The factory will take a non-VAR crankshaft as a core at no upcharge.

    Doing two engines and props is quite brutally expensive. Fortunately, the TSIO360 is actually pretty reliable - when operated conservatively. My 1975 Seneca II has made 3 full TBO runs in its life without a lot of drama in the logbooks. (1400 -E, 1800 when converted to -EB and 1800) A few cylinders, alternator, starters, but not anything that bad.

    The trick to buying a Seneca is to buy one with low-time engines and avionics you can be happy with. The rest of the plane is no different than a Lance or Saratoga and not all that expensive to keep. I have a FIKI equipped bird with boots, heated glass and stall sensors. That's more equipment to keep up and adds to the cost. If you don't need that stuff, then you can save money by not buying a de-iced plane.

    There's a lot of Senecas on the market, I'd stay away from the fixer-uppers. Basically, they're worth what their engines and avionics are worth.
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