I don't get it!
I had a friend call me from Sun N' Fun all excited about the SMA diesel engine. There is ALWAYS a discussion about alternative engines or diesel engines on a forum. I know people are looking for the Holy Grail in engines but for now the Lycoming is it. And now people want to put a 4 cylinder engine in their airplane to achieve that lower fuel burn. Why would you not want to most horsepower you can get and use an engine that has proven reliability? There are two things you can never have enough of horsepower and money.
Horsepower = Safety
The more horsepower you have the safer you will be when you need to go around, or takeoff on a hot day, or the need to climb above some rain or a storm.
Again, the fuel savings is not that much in the big picture.
The average RV-10 cost is in the $130,000 range. Insurance will be $3500 per year, hanger rent is $3000 per year. Lets say you fly 200 hours per year and fuel is $4.50 per gallon. The IO-540 will burn 13 gallons per hour and the 360 or 400 will burn 9. That is $3600 per year in extra fuel for the IO-540 or $300 per month.
You can definitely pull the throttle back as well. The difference in engine friction is not that much, OK let?s assume it is 1 gallon per hour more because of friction. So now you will spend an additional $16 per month in fuel based off 200 hours/year to have that extra power when needed. Then there is re-sale, you will have a hard time selling a highly modified RV-10. Not to mention your insurance actually might be higher because of deviations to plans.
If all you want to do is save fuel then get an RV-7. Before you really decide on a 4 cylinder, you need to go load up an RV-10 with 4 people and take it right up to 2700 lbs. at an airport that is above 3000 ft elevation. Make sure the OAT is above 85 degrees and then takeoff and see if you would feel comfortable with 20% less power. The current RV-10 has 10.38 lbs/hp with an IO-540. If you had a 210 HP engine, you could only have a gross weight of 2180 lbs to achieve that same 10.38 lbs/hp. The empty weight of a light RV-10 is 1600 lbs. Therefore with full fuel you would have a useful load of 220 lbs to achieve the same IO-540 lbs/hp. Anything over that and you will really start seeing a decrease in performance.
Just like anything, go fly a few planes and see what you think. I know everyone I talk with about these issues never go and fly. It is all imagination flying and dreaming of the idea plane ? 200 mph with 4 people burning ? cup per hour. Fly an RV-10 and then go and fly the 4 place Diamond aircraft. It has a 4 cylinder and will give you a good idea on speed and climb performance as compared to the RV-10.
Here is the fact! Flying is expensive no matter how much you want to ignore it. I love what Kirby Chambliss said in his interview in the Pilot Journal when they asked him what it takes to win the National Championship, "All the time and money you have!" Sean Tucker has said the exact same thing but it was more like, "Figure out how much you need and then multiply it by 2." Flying experimentals are the exact same. If you are on the edge of affording an RV-10 but it looks like you will squeak by with installing a 4 cylinder engine, you need to rethink it. Your project WILL cost 20% more than you think. Things will break and need to be replaced. I never changed my plan on my RV-10 from day one and I went over 23%. It just happens, ask anyone.
Tim Olsen's wife had a good right up about flying and the expenses.
http://www.myrv10.com/N104CD/why/wifesperspective.html You have to choose to fly and give up lots of other things. What you give up the most is time. The maintenance on an RV-10 is high especially the first year while you are fixing issues and troubleshooting avionics. In the past six months I have had to fix the following issues or do the following maintenance:
- 5 oil changes
- Replaced dimming controller
- Repaired rear intercom wiring
- New wheel pant supports
- Replaced B&C alternator controller
- 2 new bulbs on wing tips
- Installed new GPS antenna for Cheltons
- Stiffened oil door - was slightly popping up
- Oil cooler duct flange broke - reinforced
- Remounted Grand Rapids Magnatometer
- Installed new elevator trim mounts - Solid Aluminum
All of that takes time which takes me to another point, the hanger. Another thing to consider is your working environment. It is nice not only for you but for your spouse if you have warm or cool (depending on the season) place to work on the plane. There are many Saturdays when my wife and I go up the hanger to be with each other and friends come by there to ride bikes and be together. If it wasn?t nice then we would be apart those times.
If you have money then don?t build, just go buy a Cirrus and pay someone else to maintain it. But for most of us we have to sacrifice many other things to afford our hobby. Also, build what Van?s says to build especially the engine. It is a proven design, it works great, and you can get it fixed anywhere.
I can promise you that after your first ride in an IO-540 RV-10 you will be all smiles.