June 2, 2012 at 1:15 am #83795
Our 310N right now has a Colemill Executive 600 conversion, with 300 HP IO-520-E engines (300 HP @ 2850 RPM for 5 minutes, 285 HP @ 2700 HP continuous).
The engines are 400 hours past TBO, and starting to show signs we need to get them overhauled. Given the nature of the trips we do, we want to get more speed. Turbos would be nice.
The only other upgrade I know of for this plane that’s easily available is the Executive II, which has 300 HP IO-550-E engines. That would increase our cruise a bit.
The Riley Rocket conversion is a nice one, but as far as I know Riley is out of business (not to mention that it would require obtaining two Lycoming engines).
Wondering if anyone knows of any other STCs out there that might work for this. Preference goes towards turbo engines. I have a few ideas up my sleeve as well, but a pre-existing STC would be easier.
Thanks!June 2, 2012 at 1:02 pm #96128
JMHO, Ted: You’ll find no easy, cost-effective way to convert yours to a “T” 310. If you really need turbos (routinely flying the inter-mtn west, for example), you’d be better off trading airplanes. Others here, more knowledgable, may have a very different opinion, but that’s mine.
I’m “paying” for my turbo capability as I type, airplane is apart, exhaust systems and turbos/wastegates out for inspection/overhaul. AD 2000-01-16. OTOH, home field elevation is 7143 msl and during a typical 83degF summer afternoon, DA reaches 10,000′. 🙂June 2, 2012 at 3:32 pm #96130quote RCLOVER:
Many things worth doing aren’t easy. 🙂
Let’s assume that trading aircraft is off the table for various reasons (sentimental and practical).quote :
For you, there is no question that turbos are a requirement for any sort of practical operation. I am envious of the views you must get to see on a daily basis, but not of the weather that goes along with those views. 🙂
We often have days of 1500 nm or more. Currently we do 175 KTAS running LOP. It doesn’t make sense to run ROP – the fuel burn simply would be too high to be practical and keep the CHTs happy on this plane. Even an increase in speed of 10 kts would make a significant decrease in our block times.
For our missions, it’s not a requirement given the fact that we live in PA and seldom head west of Omaha, NE. Doing the 550 conversion would be the simple one since it’s already out there, and should gain us approximately 10 kts in cruise, still running LOP. However the price on it is not particularly desirable, hence me looking at other options. Looking at the numbers on some of the options, it looks like 200 kts at acceptable altitudes for what we do would be possible on a reasonable fuel burn.
We’ve looked at the total cost increase of turbos. By themselves, adding turbos work for our budget. A T310R would give us turbos as well as additional baggage area, which isn’t a bad deal, but again we’re leaving the constraint in of not being able to sell the plane.
So the question was more if there were any STCs out there that did what I want before I decide to do something myself or just go with the 550s. I used to do certification work for a living, so I’ve been through this rodeo before. 🙂June 3, 2012 at 3:07 am #96132rwelshParticipant
There is no free lunch with the IO-550 as your fuel burn would be up to get the 10 knots no matter what the STC holder says. Why not just run at a higher power setting to get another 10-15 knots cruise speed? If you are getting 175 KTAS on around 12 GPH running LOP, then you are doing quite well as 310s go. If you increase the power to go faster, you may have to adjust your baffles to get optimum cooling at say 2500 RPM and WOT and burn 14.5 GPH LOP. Also make sure your flaps and other controls are rigged correctly so you have no trim drag, especially the gear doors. You might want to experiment with different CGs to see if you can pick up 5 knots or so. On my 340, I load the nose so I am as far forward from the rear CG in can get which seems to give a few more knots in cruise.
fltplan.com has a great weight and balance program for free which is really good to visually see the CG after loading in all the weight parameters. You can do some test flights by changing some 120 pound bags of lead/steel/tools from the nose to the tail. You should be able to look out over the top of the tip tanks, and the top should be level with the horizon. This configuration should give the optimal low drag. On long trips, I disconnect the AP every hour and retrim the plane for low trim drag.June 3, 2012 at 11:44 am #96134quote RWELSH:
I do believe faster speeds come from an aft CG due to less downward force being applied by the horizontal stabilizer. That said in the 310 there may be an angle of incidence issue due to the original certification with much lower horsepower. My 310 time is limited to a T310R in 1975. I find it hard to believe a forward CG can speed up any airplane.June 3, 2012 at 11:53 am #96135quote RWELSH:
Correct. More speed will equate to higher fuel burn. We aren’t opposed to burning more fuel to go faster. What we’re opposed to is doing so inefficiently. The previous owner flew this plane around at WOT, 2500 RPM, ROP and about 35 GPH combined to keep CHTs happy. It worked – the cylinders have lasted quite well. However running with the engine monitor has shown that those numbers really are needed to keep CHTs below 380F in most conditions. Actually, they might have still not done a good job of 380F or less, I only experimented with it after getting the engine monitor in to make some comparisons.
In 400 hours of flying the plane as-is, we figure we’ve saved about $40,000 worth of fuel. No, we don’t intend on running inefficiently. Theoretically that fuel savings itself would pay for the 550 upgrade (and we may end up going that route), but turbos would help us further with the altitude options.
As I said, my previous job was doing certification work for a living. It’s a goat rodeo I’ve been to before, but I’d prefer not to unless there was a compelling reason to do so.quote :
That would be the simple solution, and a good question that we have considered. At 2500 RPM the EGTs get higher than what I like to see when running LOP, and the CHTs go up higher than I’d like to see. Note that I’m not running GAMIs so my ability to go LOP is limited, and also these cylinders are getting tired (albeit still passing), which typically will impact both of these. That said, in the current setup the numbers are higher than I want to see. EGT is impacted by a number of factors, but RPM is one of them.
Additionally, at 2500 RPM the noise goes up significantly vs. 2300, which is the part of the no free lunch I have a harder time with than the extra fuel burn. It gets old fast when you’re flying the plane for 8+ hours in a day. That is a function of the props (which are loud and not very well designed). New props would be an option there (and one I will likely explore when it comes time for props), but I don’t need props right now, I need engines. 🙂
The plane is quite efficient at our sweet spot of 175 KTAS @ 25 GPH, which is part of what makes it such a good fit for us.quote :
Unfortunately my typical mission doesn’t allow much for adjustments there, nor does the plane. Since the short-nose 310 has no nose baggage (just wing lockers and the main cabin), and our baggage load is pretty much immovable. That said, I’ve found that changes in weight and CG don’t do very much. Basically if it’s hot and we’re around gross weight, we end up slowing to about 170 kts. If it’s cold and we’re close to empty, we’ll do 180. But most of the year, we’re doing about 175.
Also, wouldn’t an aft CG typically increase speed? That’s what I’ve normally observed in other aircraft. Interesting that you’re noticing a forward CG increasing it.quote :
Agreed. I don’t set the AP until I have the plane trimmed out perfectly (or at least close to it) for straight and level flight, and then end up retrimming it every so often as well.
The 310 hand flies so nicely, sometimes I’ve hand flown from Pennsylvania to Texas and back just because it’s fun. 🙂
I appreciate the input!June 3, 2012 at 1:10 pm #96136quote TDUPUIS:
I don’t quite understand this – $100 per hour fuel savings while running 25 GPH?
How fast do you want your 310 to go?
It is likely that the amount of money you will spend on upgrades and certification, if you go that route, will exceed the cost of a T310R. If you really want to go fast you might want to find a T310R that has received the upgrade to a RAM IV (325 hp) configuration.
GeoffJune 3, 2012 at 1:46 pm #96137quote COCHRANE:
Re-ran the math, $20,000 savings. Sometimes I forget to put the x2 for two engines in the right place. Still, quite significant.
This is comparing how we run the plane (25 GPH trip average) to how the previous owner ran the plane (35 gph trip average).
Obviously, there are some middle ground points there, but we’ve found that they don’t do as much as you’d expect, with higher temps to boot.quote :
200 is a nice round number, and would end up shaving about 2 hours off of some of our common round trips (which currently are 16ish hours of flight time).quote :
That’s a consideration. The previous owner of this plane ended up upgrading to that exact option, and is happy with his 230 KTAS @ FL190 and the improved single engine performance (which is another thing that we’re interested in). Again, the question was posed under the constraint that this aircraft is to be the one utilized, not that we purchase another aircraft. If we went the route of another aircraft, there are a number of other good options out there from T310Rs to 421s.. I’m also aware of the cost of upgrades and certification. Again, I did this for a living before. The 310 represents a good compromise for us as far as size, preference to a standard cabin vs. cabin class, short field capability, etc. But more speed is more better.
I think Bob explained my goal rather well when he discussed putting the money and work into his T303 in one of his articles – wanting a “best in class” airplane. Ours won’t be overall best in class for some other reasons. We’re looking for “best in our class,” which involves a nice avionics suite and making the plane even more of a hot rod than it is.June 3, 2012 at 2:59 pm #96138
Ted wrote: “…So the question was more if there were any STCs out there that did what I want before I decide to do something myself or just go with the 550s. I used to do certification work for a living, so I’ve been through this rodeo before. …”
Not that I’ve found or know about, Ted. I see there are Rajay STC’s for 310’s with 470 engines, though.
Speed and fuel flow…. Well, yeah, burn more go faster 8) I usually run 2350 RPM (see TCM Critical Service Bulletin 09-11), and 25″, or 61.4% power according to the book. 177 KTAS + or -, depending on DA. Always above 10,000 msl. I’ve figured 31gph, best power mixture. Actual useage shows 28-29 gph for flight Hobbs, start to shut down. 32-33 gph maint. Hobbs, takeoff to landing. 31 gph for overall planning purposes works well. Fuel profile on CSC Duats has been refined so I usually see actual burn within 2 gl of flight plan on a 100 gl top off.
Into the wind, I’ll use 27″ for 67.5% power and see 184 KTAS at about 33 gph, but I haven’t verified the FF. I see 190 KTAS at 73.7% power (2350 RPM/29″), on 35 gph (unverified), but that’s in the low to mid-teens, I haven’t been to the flight levels. Nor do I use 75% power for anything but cruise climb, mixture for EGT’s in the high-1200, low-1300 range. My factory CHT’s are always happy, 375 deg range. LOP operation would get me 4 gph less, I think, but I’ve got my reasons for best power mixture … different discussion.
Lots of “points”, Ted, based on my experience over 9 years of ops, FWIW. 200 KTAS would be fun, but spendy, IMHO. My book shows 212 KTAS @ 15,000, 73.7% power, recommended lean mixture, 31.3 gph. Not gonna happen 😯June 3, 2012 at 3:08 pm #96139quote RCLOVER:
That’s what I’ve found so far. I’m not a fan of the various Rayjay products for a number of reasons. And either way, I’m not downgrading to 470s. 🙂quote :
I note that you have an R model, and those seem to be a bit draggier than the earlier models (which is one of the motivations to keep our N-model). Additionally, since you run ROP rather than LOP, we’d expect to see different fuel burns between our aircraft.
The previous owner runs best power and fast on his RAM T310R just as he did with this plane. He gets the speed, but has fuel burn numbers to prove it! For his mission, it works well and makes sense. Our mission makes it more logical for us to get economy where we can. We don’t mind using O2 when it’s beneficial and putting the turbos to work.
It seems the answer to my original question is “No, there aren’t any STCs out there for what you want.” Riley Rocket excluded.
And so we keep on plugging away at choosing an option…June 3, 2012 at 3:28 pm #96140
Good luck, let us know how it goes, the Project.
BTW, mine is a Q, by serial number it’s one of the last of the short-nose. “Word” has it that the useful load is better than the R’s, but I wouldn’t know. My own, with 4 back seats removed, is 1800#. I also don’t know about comparable speeds. Except that Cessna book speeds are… a bit optimistic? 🙂June 3, 2012 at 10:34 pm #96142
Sorry, Rich, I clearly had read that yours was a Q! I had thought the Qs were a bit slower than the normal short-nose planes due to the hunchback? I also could be wrong.
It seems that many book numbers are a hair on the optimistic side, although I’ve found that Cessna’s numbers are based more in reality than Piper’s. I don’t know what’s in the water around here, but I’m glad we drink from a well rather than municipal… (I live near the old Piper factory)June 4, 2012 at 12:26 am #96143quote TDUPUIS:
Right, the TSIO-520 – powered ’66 320 I owned was 5-8 knots faster for the same fuel burn. I write it off to the Q’s 3-bl props and VG’s. Both have boots, hot props, and the 320 had a hot plate…But 2-bl props and no VG’s and no back window.
I’ve always “heard” that the Cessna numbers were, shall we say, “inflated”. My personal experience validates that assumption. The Piper numbers, at least for the Comanches I’ve owned, were pretty close. The Comanche folks I know will tell you that they’re faster than book … 🙄
ps You’ll find my family name on a Brick in the Piper Museum at Lock Haven.
pps You might consider a later model 320.June 4, 2012 at 12:21 pm #96146quote RCLOVER:
It probably just comes down to which engineers were on which projects. Some of the Aztec numbers are downright humorous. Although they aren’t lying about it being able to haul a load!quote :
Very cool!quote :
If we switch airplanes, a 320, T310Q, or T310R would be on the list for sure.
My wife and I talked about this again yesterday, and we further believe that we’re going to stick with this plane (although which option we choose is undecided). This is a very nice airframe that we have been customizing over the past two years and fits our needs exceptionally well. I’ll continue to work on some options and we’ll see what happens. We’re planning on doing the engines by the end of the summer.June 4, 2012 at 11:32 pm #96149
Ted wrote: “…For you, there is no question that turbos are a requirement for any sort of practical operation. I am envious of the views you must get to see on a daily basis, but not of the weather that goes along with those views…”
At 5:30 this afternoon local ASOS reported density altitude at 10,400 … no wonder I was a little “tired” after mowing the lawn 🙂
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