0-235 in RV-9A

[David Wilson]

Looking at fitting 0-235 in our aircraft as performance is not that bad in comparison to 0-320 but a lot more economical which is important considering fuel costs in the UK ($3 per ltr).

Would be greatful to hear how other listers have got on with this engine please.

 

[David-aviator]

Looking at fitting 0-235 in our aircraft as performance is not that bad in comparison to 0-320 but a lot more economical which is important considering fuel costs in the UK ($3 per ltr).

Would be greatful to hear how other listers have got on with this engine please.

I had an 0-235 in a previous airplane, it is a good engine. But there is no economical advantage over the 0320 except if you can acquire an 0235 for less money. All Lycomings burn about the same amount of fuel per hour relative to HP produced. You can fly the 0320 as economical as the 0235 - just pull the throttle back to produce 0235 horse power. Same can be said for comparing the 0235 and an 0360. The only loss of efficiency is the increased weight of the 0320 or 0360 over the 0235.

The dry weight of the 0235L is 218 lbs., the 0320A is 244 lbs., and the 0360A is 265 lbs. Another consideration in this matter is the center of gravity of the -9A. If ballast is necessary with the 0235, it negates some of the efficiency advantage of the engine due to its lighter weight.

 

[pierre smith]

Great performance

Looking at fitting 0-235 in our aircraft as performance is not that bad in comparison to 0-320 but a lot more economical which is important considering fuel costs in the UK ($3 per ltr).

Would be greatful to hear how other listers have got on with this engine please.

You'll probably get a reply from Bill Repucci soon, who installed one in his -9 and loves it...over 160 MPH cruise!

Regards, and welcome to VAF

 

[rvbuilder2002]

I had an 0-235 in a previous airplane, it is a good engine. But there is no economical advantage over the 0320 except if you can acquire an 0235 for less money. All Lycomings burn about the same amount of fuel per hour relative to HP produced. You can fly the 0320 as economical as the 0235 - just pull the throttle back to produce 0235 horse power. Same can be said for comparing the 0235 and an 0360. The only loss of efficiency is the increased weight of the 0320 or 0360 over the 0235.

The dry weight of the 0235L is 218 lbs., the 0320A is 244 lbs., and the 0360A is 265 lbs. Another consideration in this matter is the center of gravity of the -9A. If ballast is necessary with the 0235, it negates some of the efficiency advantage of the engine due to its lighter weight.

I agree with David.

I have an RV-6A with an O-360 (180 HP) and a Sensenich fixed pitch prop.
I have a monthly (personally imposed putting around the local area) fuel budget of $100.
My kids and I fly around the local area at about 17" MP and 2200 RPM still indicating about 145 MPH and showing just above 5 GPH on a calibrated fuel flow instrument that is always within .2 Gal of error at fill up. Because of low power settings in the pattern, etc., we average out to right about 5 GPH over all. With our local fuel price being steady at right about $4 per gal for quite a while now, we can fly about 5 hours per month.
If traveling cross country we can still true right at 200 MPH burning just over 9 GPH.

This can be done with any RV model equipped with any engine. You just have to have the will power to pull back on the $ meter control knob.

The only way I would install an O-235 in an RV-9 is if I already had one (no cost to me) that I knew was a good engine. If I needed to go out and purchase an engine anyway, I would get an O-320. It will be more marketable for resale and the performance difference because of flying with a lighter weight when using the O-235 is so small that it is not worth considering.

 

[Yukon]

Mouse Motor

Since the RV-9 was prototyped at Van's with an 0-235, we have the advantage of knowing that it will do 120 MPH on 3.5 GPH. No other airframe/engine combination can do this to my knowledge. If minimal fuel burn is your desire, it's hard to beat the smallest engine. Pumping losses prevent larger engines from duplicating the SFC of smaller engines. That, in part, is why Lycoming builds so many different sized engines.

 

[rvbuilder2002]

Since the RV-9 was prototyped at Van's with an 0-235, we have the advantage of knowing that it will do 120 MPH on 3.5 GPH. No other airframe/engine combination can do this to my knowledge. If minimal fuel burn is your desire, it's hard to beat the smallest engine. Pumping losses prevent larger engines from duplicating the SFC of smaller engines. That, in part, is why Lycoming builds so many different sized engines.

I think they make many different engines because you wouldn't put a 200 HP engine in an airplane whose mission /performance profile was only designed for 108 HP.

No need to defend the decision to choose an O-235 for an RV-9(A).
It is still a good airplane with that engine. I have 10 hours or so flying a 9A with that engine.
I still think it is very little advantage over a larger engine and I think I could come very close to matching 120 MPH and 3.5 GPH. One benefit I have with the larger engine is little or no concern about density altitude in the summer.
That is not the case with an RV-9(A) equipped with an O-235...I have personal experience with this. In the flat lands (most of the U.S.) this is probably not an issue. Out West here where we regularly cross mountains and use higher elevation airports, it must definitely be considered.

 

[Yukon]

Scott,

I'll have to agree with you there, and want the UK fellow to understand too. If hot and high performance is required, the 0-320 is definitely a better choice. Another gallon an hour is inconsequential if you can't clear the powerlines at the end of the strip!

 

[L.Adamson]

One benefit I have with the larger engine is little or no concern about density altitude in the summer.

As I do live in a mountainous area (4620'msl), I think about density altitude a lot. And it's one of the reasons I'm not particularly fond of small Pipers, Cessna's, etc. I'd certainly go with the 0320 for around here too. It's a great "feeling" to not having density altitude on the mind constantly. I've got nearly 40 hours in a 9A with a 150 hp 0320, and it still had some pretty good performance figures, considering it's 10 horses less.

L.Adamson -- RV6A 0360 C/S

 

[N941WR]

David,

Welcome to the forum.

When you get a chance, do a search on this engine, you will find a number of questions and posts all ready out there which are worth reading.

As you can tell, almost everyone will make the argument to install an O-320 or larger in your -9.

You will also find a bunch of people who will tell you to install every possible dodad in your airplane, thus inflating the empty weight and requiring those larger engines.

If you build your plane as light as you can, as Van's likes to say, "Build lightness in," your airplane will perform better than you will ever imagine.

My -9 has a 135 HP O-290-D2 installed which pulls me along at 165 MPH and my GW climb is around 1800 FPM. (I am going to change the prop out this summer after I finish all the fairings and get some solid speed numbers to Catto.) The empty weight of my plane is 990 LBS and the thing just performs! One real advantage of building light like this is my plane has a 760 lbs useful load and that is without inflating the GW. (You can check my web site listed below for details and pictures.)

There is a local -9A with the 108 HP version of the O-235. This airplane replaced a 160 HP -6A that was his first build. Once his -9A was finished he gave the -6A to a relative so he can still fly it from time to time. In talking with him, he said he prefers the -9A and regularly flies 800 mile non-stop legs on the standard tanks.

He has commented that the climb is a bit anemic but that is all relative, even at 1000 FPM at gross, you are out climbing a Skyhawk.

Since you are in the UK and you play by a different set of rules than we do here and you might be happy to know the O-235 can be built up to a certified 125 HP by changing out the pistons. Add on a pair of electronic ignitions and I would suspect it might be closer to 130 HP.

I recently posted some numbers from a trip my wife and I took last weekend you might be interested in. Here's the thread

As for using an O-290 as I did, they are a great engine but have been out of production since the 50's so parts can be a challenge to come by. I only used it because I got such a great deal, I couldn't pass it by. My total FwF costs are around $7,500.

Best of luck and please let us know how you progress with this engine. Who knows, maybe you will put some of the rumors to rest.

 

[videobobk]

Good luck on your build. I'm sure you won't be unhappy, no matter which engine you end up with. IMHO, there is only a little economy to be gained by going with the 235, but it may be significant to you. Bill brought up one good point that you should consider, especially if you are out to save fuel. When I went to electronic ignition (right side only) my fuel burn dropped by a gallon an hour at cruise. I believe (and no, I can't prove this) that puts me down around the same fuel burn as a straight mag 235. I would hope you in the UK have that option, but I don't know about your rules. Let us know how it all turns out.

Bob Kelly

 

[rvbuilder2002]

He has commented that the climb is a bit anemic but that is all relative, even at 1000 FPM at gross, you are out climbing a Skyhawk.

An RV-9A at gross weight with an O-235 engine will not come anywhere close to 1000 FPM climb at higher density altitudes. 8,000-10,000 ft Density alt. is not at all uncommon at many of the higher altitude (4000 - 5000 ft elevation) airports out west.

This is the reason that the factory approved gross weight for an O-235 engine RV-9(A) is 1600 lbs instead of the 1750 lbs for the O-320. Even at 1600 pound gross weight the max rate of climb is specified at 950 FPM (sea level). A summer time afternoon departure at a lot of airports in the western U.S. would be impossible.

 

[N941WR]

An RV-9A at gross weight with an O-235 engine will not come anywhere close to 1000 FPM climb at higher density altitudes. 8,000-10,000 ft Density alt. is not at all uncommon at many of the higher altitude (4000 - 5000 ft elevation) airports out west.

Scott, the guy lives in the UK, I'm not thinking they have even 6,000' foot mountains in the Western UK so this won't be an issue.

Also, my O-290 can cruise climb at over 800 FPM at 9,000+ so I suspect a 1750 GW O-235 power -9 will do around 300 to 400 FPM, which is still better than a Skyhawk out of Ledville.

It is all about mission, and if the numbers of the O-235 seem to meet that mission, then why wouldn't that engine suit his needs?

Besides, should he set his GW at 1750 and his empty weight comes in where mine did, it is unlikely he will ever load the plane up that much.

 

[Bryan Wood]

Scott,

Didn't you build all of the factory planes? It seems likely that you have flown all the various models and have experience to offer that the rest of us don't have. I have a question based on experience from flying my 9a for 4 years now that has a heavy nose with an 0-320 swinging a Hartzell. As you stated I can power back and get Cessna type speeds at the 4 gph range but the plane flys nose high and just doesn't feel nice to fly. I still do it often, but if my plane flew this way all of the time it would be a negative for me. It also is a little mushy on the controls at these low speeds and again it just isn't as much fun. My question is this. If the plane is going to be operated at lower power settings for economy anyway will a lighter plane because of the smaller engine fly more level and feel like it is in its element. It seems like the wings won't have to have such an aggressive angle of attack to hold up the small prop and engine, but with no experience in both this is just a hunch.

 

[Yukon]

Wonderful insight Bryan. I can't wait to hear the answer. I'm just not comfortable with the "one size fits all" thinking.

 

[bsacks05]

Bryan,
I read with interest your description of your 9A being "nose heavy". I am no expert and won't offer any opinions but I'm interested in what suggestions will be offered by those with more experience.
I run an O320 as well, but with a wood prop and tailwheel and have never noticed the flight tendencies you describe.
Sounds like a problem which can be solved, however.

 

[David Wilson]

Thanks for the replies Guys. Had hoped there may be someone out there who is flying on118HP!!! Thanks John for your comment and your reasons for going down the 235 route stated on your web site.

We had planned on fitting a Wilksch diesel at 110/120HP but unfortunately they when out of production and their designer is now Director of Engine Development or similar title at Teledyne Continental. About 20 engines were sold for RV9's I think and the first one's are starting to fly on permits to test. I understand though that there are lots of cooling problems and getting PFA (now LAA) approval is daunting.. As we want to fly sooner than later we thought that a 235 would be suitable and in the future we could change to a diesel as they become available and get approval. There are some promising designs coming on over here.

Altitude isn't a problem as most airfields in the UK are below 300' and the highest (I think) Dunkerswell at 850'. In Western Europe most are below 1000' and the highest is an Altiport in the French Alps at 6,581' sloping down over 535m to the threshold at 6368'. You land up hill and take off down hill!! Regarding temperature the odd day in the UK might make 80 + deg F so density altitude is not a problem.

We don't have experimental aircraft over here and all our designs have to be cleared by the LAA including mods. This might change under the new European regulations. We cannot fly our RV's or any other homebuilt at night, IMC or over built up area's. Again this might change.

As far as cost go my $200 a month on a 0-235 powered Robin R2112 will give be about 3 hours flying at about 55% and a cruise of about 90Kts. If you are interested put her registration G-CBNG into Google.

One of our concerns about the 235 though is short field performance as there are quite a few grass strips in the UK at about 300/400m and while Van's figures say it will be OK will it on wet grass which has not been cut for a few days?

David Wilson

 

[N941WR]

David,

Check your gmail account...

 

[Kevin Horton]

I have a question based on experience from flying my 9a for 4 years now that has a heavy nose with an 0-320 swinging a Hartzell. As you stated I can power back and get Cessna type speeds at the 4 gph range but the plane flys nose high and just doesn't feel nice to fly. I still do it often, but if my plane flew this way all of the time it would be a negative for me. It also is a little mushy on the controls at these low speeds and again it just isn't as much fun. My question is this. If the plane is going to be operated at lower power settings for economy anyway will a lighter plane because of the smaller engine fly more level and feel like it is in its element. It seems like the wings won't have to have such an aggressive angle of attack to hold up the small prop and engine, but with no experience in both this is just a hunch.

The biggest reason why the nose is high, and the controls are mushy is because you are flying slowly. The angle of attack needs to be higher than it would be at higher speed, so the wing can develop enough lift. The controls are mushy because the airspeed is low.

The forward CG has only a tiny part to play here. If the CG moves forward, the tail must develop additional downwards lift in order to keep the nose from falling. The wing must then develop extra positive lift, as the wing must support the weight of the aircraft plus the downwards lift created by the tail. The additional downwards lift created by the tail due to the CG being further forward than if an O-235 was fitted is probably less than 10 lb (this is a SWAG - I could calculate a more exact answer if I knew how much heavier an O-320 was than an O-235, how many inches the engine CG was ahead of the aircraft CG, and how many inches it was from the aircraft CG to the HS rear spar). But even with a more exact calculation, the basic conclusion would be the same - the CG is only a very minor cause of the nose high, mushy controls situation.

 

[rvbuilder2002]

Scott, the guy lives in the UK, I'm not thinking they have even 6,000' foot mountains in the Western UK so this won't be an issue.

Sorry, I was writing in more general terms as a reason for choosing the O-320 over the O-235 (for anyone else that may read the thread).

 

[N941WR]

Sorry, I was writing in more general terms as a reason for choosing the O-320 over the O-235 (for anyone else that may read the thread).

Scott,

That post of mine sounds a bit pissy, sorry about that. It was not my intention.

 

[rvbuilder2002]

I have a question based on experience from flying my 9a for 4 years now that has a heavy nose with an 0-320 swinging a Hartzell. As you stated I can power back and get Cessna type speeds at the 4 gph range but the plane flys nose high and just doesn't feel nice to fly. I still do it often, but if my plane flew this way all of the time it would be a negative for me. It also is a little mushy on the controls at these low speeds and again it just isn't as much fun. My question is this. If the plane is going to be operated at lower power settings for economy anyway will a lighter plane because of the smaller engine fly more level and feel like it is in its element. It seems like the wings won't have to have such an aggressive angle of attack to hold up the small prop and engine, but with no experience in both this is just a hunch.

Kevin H. pretty much answered your question already I but thought I would still reply.
Any wing produces a given amount of lift at any specific combination of airspeed and angle of attack to produce level flight. For level flight the wing is producing an amount of lift equal to the weight of the airplane (and the weight of the down force produced by the horizontal tail).

In any airplane, if you reduce speed, you will have to increase angle of attack to continue producing the same amount of lift to support the airplane weight for level flight. The wing incidence that is built into the airplane is done based on what the normal cruise speed range will be for the airplane.
If the RV-9 had been designed for a cruise speed the same as a C-150, it would probably have had a higher angle of wing incidence which would have allowed the fuselage to fly at a more level attitude.
Because the RV-9 has a wide speed range and a high cruise speed, when flying at C-150 speeds it will seem to have a noticeably higher angle of attack than you may be accustomed to in other airplanes.

So...this has nothing to do with you thinking your RV-9A is nose heavy (which I don't think it is). I imagine that if you do a W&B calculation for a couple of adults and a bunch of baggage, you C.G. likely falls some where in the middle of the usable range. This is perfect since the designed mission for the airplane was cross country cruising.

As Kevin already mentioned, having a slightly lighter airplane wont cause much of a noticable change in the angle of attack an RV-9 flys at, at any given airspeed

The control response issue is just a function of slower airspeed causing less control force that the control surface can produce.

As a side note...I also don't like slogging along at high angle of attack when I need to fly slow. In all of the RV models, when I need to fly slow for an extended period of time (such as the arrival to Oshkosh) I lower 10 degrees of flaps. This reshapes the wing, making it act sort of like it is at a higher incidence angle (and it produces some pitching moment) so the airplane will then fly more nose down in level flight.
This works great as long as you can stay below Vfe.

Hope this helps.

(How did I do Kevin?)

 

[Bryan Wood]

Seems logical to me

Kevin and Scott,

Your answers make sense to me. So if Van had wanted me to fly at 100 knots indicated the wings would be mounted to position the nose down more. Okay, so what's up with the other guys? Am I the only one flying this slow?

As a clarification when I said the engine and prop were heavy it was just to give a comparison since the thread was about using lighter engines. My CG couldn't be better and there doesn't seem to be any situation where we have to worry about it.

But I'm stickin to the way it feels at 100 knots IAS. How about it folks? Do you like how your plane feels at that speed right before you can drop the flaps? Mine is better with a few more knots passing over the wings.

 

[petehowell]

Slow

Hey Bryan,

We have almost the same set up. I fly slow quite a bit. 100kts feels fine to me, but I get the nose high feeling at about 90kts. My guess is our planes fly the same, it is just subjective how we feel.

I fly with my daughter at 100kt and the alt hold engaged all the time when we are not going anywhere. It only burns 3.3 GPH at that speed and is still fun to fly.

From a post last Summer:

Part of the attraction of the RV-9A is it goes slow just as well as it goes fast. Here you see me burning up the sky at 98Kts TAS burning 3.3 GPH - dare I say it - LOP. I know I am not really going any where, but that was the intent of the flight anyway. The Dynon also shows the engine at a whopping 31% power or less than 50HP. The -9A - as all RV's, are pretty dang efficent. The computed range - with a slight headwind at these settings is 1,120 miles.

 

[Dave_Boxall]

We had planned on fitting a Wilksch diesel at 110/120HP but unfortunately they when out of production and their designer is now Director of Engine Development or similar title at Teledyne Continental. About 20 engines were sold for RV9's I think and the first one's are starting to fly on permits to test. I understand though that there are lots of cooling problems and getting PFA (now LAA) approval is daunting.. As we want to fly sooner than later we thought that a 235 would be suitable and in the future we could change to a diesel as they become available and get approval. There are some promising designs coming on over here.



David Wilson

David

There are two LAA approved installations of the WAM-120 on RV-9A's, both appear to be giving satisfactory cooling and three aircraft flying. Wilksch are not in volume production at the moment, they are supplying engines, but they're just stepping back from new homebuilders as they find homebuilders consume far too many of their resources in terms of support.


I have a WAM-120 in an RV-9A. I hope to do my first engine runs this weekend and be flying in the summer. If you'd like to get in touch send me an Email - dave_boxall (at) yahoo.co.uk

Dave

 

[gorbak]

Lycoming O-235 L2C 118 hp

David,

My build partner and I have the Lycoming O-235 L2C 118 hp engine in our RV-9A and we could not be happier with this combination. We fly out of Wichita, KS (KICT) at 1330' and a Catto two blade prop, full fuel, two of us in the plane (I am 230 lbs), we are getting close to 950'/min. climb. With one of us in the plane, from 3000' and full fuel, our timed climb was 1075'/min.

I am out of state on business or I would give you more data. Feel free to send me an e-mail requesting our data and I will send to you in a week or so.

Again, this has been a great combination and our combined fuel flow, including climb and landing, WOT in cruise, has been averaging 5.5 gph. We consistently produce 167 to 171 mph at 2800 rpm. The Catto prop is redline capable to 3200 rpm. Contact me at [email protected]

Pat Garboden
RV-9A N942WG
Ozark, MO

 

[gasman]

MORE SLOW FLIGHT

Kevin and Scott,

How about it folks? Do you like how your plane feels at that speed
right before you can drop the flaps? Mine is better with a few more
knots passing over the wings.

Go out and spend some time flying at 60, then 100 will be just fine.
The more time that you fly slow, the more you will understand your
RV and what it is telling you.

At least twice a month I will go up and fly just above stall.... and
then increase the speed about 10 mph and stay there for about
10 minutes and add another ten. It is a good fealing to control
the aircraft at the lower speeds....

I fly a 6A 0320 FP.

 

[Bryan Wood]

Go out and spend some time flying at 60, then 100 will be just fine.
The more time that you fly slow, the more you will understand your
RV and what it is telling you.

I fly a 6A 0320 FP.

My plane wallows along just fine at 55 mph indicated when dirty. At 100 I understand what it is telling me and it's that it is flying nose up.