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IO 360 180 HP in a 9A

kaweeka

kaweeka

Well Known Member
I am a 5000 ATP who is looking to join the experimental world after a loooong time flying certified aircraft and spending a LOT of money for that privilege. I've looked at a lot of aircraft, flown a few types from canards to Glasair/Lancair to LSA and believe (at this writing) that the Vans RV 9A is about as good a mission fit as I've found. After looking around, I see what looks like a very nice aircraft but lists a 180 HP IO360. I have read several articles about overpowering these aircraft and the aerodynamic dangers possible and want some input from those that know much more than I if this should throw up red flags about non-standard building, or if this is common and acceptable. My wife and I really want to use this as a means to travel. Inverted is not in the flight plan. Been there, done that. Looking forward to your input.
Thanks,
Dave
 
Welcome Dave.

I have an O-360 in my -9 and while I understand Van's comments regarding VNE and larger engines, you simply can't run past it with this engine in an RV-9.

With 650 hours in my -9, 450 hours with the O-360, I would be surprised if you had a problem.

Find someone knowledgeable in RV's to do a preflight and you should be OK
 
There are plenty of 180HP 9's out there - my first ride was in one. "Acceptable" depends on who you ask, but I certainly wouldn't draw any conclusions on build quality based just on the 'non-standard' engine. I would look into insurance costs for that engine/airframe though.

I won't wade into the debate about whether one should or shouldn't, but I will say I am building mine with a 320, and remember that Van designed the prototype plane around a 118HP O-235. I also fly in Florida, so high-altitude operation is not as big a concern. My main goal is efficient, long-distance flying. That being said plenty of people are flying 180HP (and higher, I'm sure) 9's out there, and operating safely in the margins. Their experiences would be valuable to hear.

Chris
 
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Thanks for your thoughtful replies and indulging a newbie. Such is the transition from certified to experimental. I will need to adjust my thinking and processes a bit. I do feel better about the engine question. The aircraft is in Ohio and I'm in California. Need to figure out how and who to get to put an eye on this one to find out about build quality.
 
Dave,

Welcome to VAF. The -9 is a fantastic plane and very stable for cross country and IFR flying. I agree that a non-standard engine does not determine build quality. Vans recommends the O-235 or O-320, but they also strictly recommend against IFR flying, which many RVers ignore, including myself. In fact, I talked to a Vans tech at an airshow once and specifically asked about the -360 on a -9 in performance compared to a -6 or -7. He said it would likely perform the same as those other models with the same engine. He did not specifically try to talk me out of putting that much power in it. Weight would be a consideration, as would CG. Get someone who knows -9's to do a Prebuy inspection and test fly it and get their opinions.

Enjoy. The -9, IMHO, is the sweetest flying RV, while the -10 is the most comfortable.
 
RV-9 education

Dave sence your in Roseville, you are near several RV's that fly weeky. Google Sacramento RVators, most of them fly out of Lincoln. I have built a couple RV's started with a 4, and am currently helping my son build anouther 4, I would be glad to help in any way, I fly out of RIU and JAQ. IM me and I will give you my phone number.


Randy
 
YellowJacket RV9 said:
...

I would look into insurance costs for that engine/airframe though.

...
Click to expand...

The insurance companies don't seem to care and honestly, they have never asked and I haven't volunteered that it is a "non-standard" engine. I just told them I have a O-360.

I did ask one insurance company how the price RV's with auto engines installed and was told they lump all RV's together and the engine doesn't matter.

One other thing, insuring an Experimental is generally more expensive than insuring a "Like" certified airplane of the same value. The reason is simple, they are "experimental".
 
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O 360 180 HP in a 9A

Give me a call at 775-843-6133 and we can talk IO/O-360 engines in a -9A. I have a 2007 with 1294 hours, fixed pitch prop, and an O-360-A4M. It is in Reno at RTS. Dan
 
As I understand it, the 360's weight gain is minimal (I0-320 lists at 291 lb. per Lycoming...what's a 360?). The key is to avoid the temptation of overspeeding the airframe through judicious use of the throttle and control stick. Many of us drive cars that are capable of 130, 140, or 150 mph, but most use our heads and stick to (or close to) the posted limits.

Personally, I'm building my -9A by the book, with an IO-320. I like the idea of using full throttle and never having a concern about the structure (in very still air, of course!). And the less weight I have on the nose wheel, the better....assuming CG is within safe range.
 
N941WR said:
Welcome Dave.

I have an O-360 in my -9 and while I understand Van's comments regarding VNE and larger engines, you simply can't run past it with this engine in an RV-9.

With 650 hours in my -9, 450 hours with the O-360, I would be surprised if you had a problem.

Find someone knowledgeable in RV's to do a preflight and you should be OK
Click to expand...

Bill,
I can't help but comment since it has been said so many times previously.
The design HP limitation on the RV-9(A) has nothing to do with exceeding VNE.
THIS BLOG POST gives a very good explanation of the factors involved.
I suggest the OP search through some of the previous discussions. It has been explained numerous times.

Since it hasn't been discussed in a while I am adding relevant details....
The RV-9(A) is designed to normal category load requirements (3.8 G's)
It has a designed Vno (max. structural cruise speed / normal operating speed limit) that in certain circumstances can easily be exceeded with higher than 160 HP engines. This may be down played by some as trivial, but it is not.

Stepping onto soap box......

This thread is a perfect example of some of the dangers of the experimental aircraft world.

I wont disagree, that an RV-9 can be flown safely with a 180 HP engine. IF the builder fully understands the reasons for the limitation, and properly compensates during it's operation.
It is obvious to me there are people flying with bigger engines in RV-9's, that don't have that understanding. Has it not been an issue so far because the RV-9 is over built? Maybe.
Has it not been an issue so far because people do not understand the details, and have just been lucky? Also a possibility.

Here in lays the danger.... a builder may understand, but then sell the airplane to someone that knows nothing of the details (The very subject of this thread). Since there is no POH spelling out those details, the new unsuspecting owner will not know. His only knowledge will be the info provided to him by others (such as on the VAF forums) that may not know any more than he does.

Stepping off of soap box.....
 
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Not to worry Doug, you can't over speed an (I)O-360 powered -9(A) at any altitude with wide open throttle. However, point the nose downhill with any engine and you can over speed it, along with your engine.
 
N941WR said:
Not to worry Doug, you can't over speed an (I)O-360 powered -9(A) at any altitude with wide open throttle. However, point the nose downhill with any engine and you can over speed it, along with your engine.
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Yeah, I guess what I meant was that you're closer to Vne with a 360 in a full-throttle situation, so you have to be more vigilant with nose-down attitudes, throttle position, etc.
 
rightrudder said:
Yeah, I guess what I meant was that you're closer to Vne with a 360 in a full-throttle situation, so you have to be more vigilant with nose-down attitudes, throttle position, etc.
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Very true.

In my case, knowing I was going to be over powered, I elected to use a fixed pitch Catto prop cut for cruise. I can easily climb at over 1600 FPM at gross. When pointing the nose down hill, I have to throttle back to keep from over speeding the engine, which keeps me below VNE.

All that said Van's does not recommend the 360.
 
What is safer, a 9 with a 320 or 360 taking off in the sumber out of Aspen CO? How about when you need to climb to 15k so you don't hit some mountain? You have to determine your mission and then decide what is safer for YOU. IF you are not a careful enough pilot to keep from over speeding, maybe you need to consider other activities.
 
Reminds me of the days from the past, The Forked Tail Doctor Killers. As my good buddy IA mechanic states... "stupid pilot tricks". Most of the time it is NOT the airplanes fault. :)
 
Cirrus

I think Cirrus has taken over that title here in 21 century.....

180hp CS in a rv9 has one heck of a climb, and I thought the -3 was good.

If the OP knows enough not to point a Boeing down with full throttle, maybe he knows something about not doing the same thing in a 180hp rv9.

To all the newbies who read this post years from now, learn about TAS on Vans's designs. It may help you one day when you are trying to get home decending through a FL12 avoiding thunderstorms and in a hurry.... I.e. read smoky's story

Good day.

LifeofReiley said:
Reminds me of the days from the past, The Forked Tail Doctor Killers. As my good buddy IA mechanic states... "stupid pilot tricks". Most of the time it is NOT the airplanes fault. :)
Click to expand...
 
grubbat said:
To all the newbies who read this post years from now, learn about TAS on Vans's designs. It may help you one day when you are trying to get home decending through a FL12 avoiding thunderstorms and in a hurry.... I.e. read smoky's story
Click to expand...

Very good advice, but for the RV-9 people should pay particular attention to the one after Smokys story titled "ALL THE PRETTY HORSES"
VNE is important in all the RV's, but because the RV-9 was not designed to aerobatic load limits (it is 3.8 instead of 6 G's) Vc or Vno (basically the same for the RV-9 is just as important. The aerobatics capability of the other 2 seat models gives them much more envelope margin (read the article), which is why it is not emphasized as strongly with those as it is with the RV-9.
In an RV-9, Vno can be exceeded in level flight with 180 HP.
 
rockwoodrv9 said:
What is safer, a 9 with a 320 or 360 taking off in the sumber out of Aspen CO? How about when you need to climb to 15k so you don't hit some mountain? You have to determine your mission and then decide what is safer for YOU. IF you are not a careful enough pilot to keep from over speeding, maybe you need to consider other activities.
Click to expand...

If that was a serious question, my answer would be if you are cutting it so close that a 160 HP RV-9 wasn't going to make it safely in a particular situation (it is a rather highly capable airplane even with 160 HP) then you probably still have no business being in that situation with 180 HP.
 
It has been 23 years since I flew with Van in his Red RV6A. The flight was totally amazing. We discussed engines, HP, performance and keeping things very simple. Vans advice in 1991 stuck with me into my 2009 RV7A build... Simple, Light, O-320, FP, VFR... and just the very basic seats for interior. It is one of the nicest flying RV's I been in to date.
 
Then why do you put that extra 2 gallons of fuel in your tank when the trip says it will only take a determined amount. Both amounts should work fine and probably will. If you hit a head wind, you may want that extra fuel and if you hit a down draft in the hills, a little extra power may be nice.

rvbuilder2002 said:
If that was a serious question, my answer would be if you are cutting it so close that a 160 HP RV-9 wasn't going to make it safely in a particular situation (it is a rather highly capable airplane even with 160 HP) then you probably still have no business being in that situation with 180 HP.
Click to expand...
 
rockwoodrv9 said:
Then why do you put that extra 2 gallons of fuel in your tank when the trip says it will only take a determined amount. Both amounts should work fine and probably will. If you hit a head wind, you may want that extra fuel and if you hit a down draft in the hills, a little extra power may be nice.
Click to expand...

I get your point, but using that logic, why not put on a 200 HP instead of the just the 180?

My opinion is the same.
If a down draft in the mountains would be better dealt with by a particular pilot if he had 20 extra HP; with as capable of an airplane as the RV-9 is with 160 HP, I would say he is cutting it a bit to close.
In simpler terms, if an RV-9 pilot is using good judgement, he should never be in a spot where he was wishing for the small performance gain that 20 more HP would provide.
Even that statement is far to general, because in the example you gave, a 160 with constant speed would probably be better off than a 180 with a fixed pitch prop. at altitude in the mountains.
 
Not trying to harsh anyone, but in mountains you can be cruising dead smooth then round a ridge or something and suddenly you're goin down like 2500/min. So, you never know.
 
Not quite as many airframe hours as guccidude, but my RV-9 has about 700 hours now. Having learned to fly at LXV (field elevation 9920) in a C172 one appreciates having a few extra HP under the cowl. Engine weight difference is only a few pounds from the 320, so as long as one understands the limitations already spelled out in this and other threads, I see no reason to NOT have the 360. At cruising altitudes of 12-18k, the HP available is considerably less than a 320 at sealevel.

As with guccidude, you are welcome to come visit RTS and see/ride in either the 9 (mine) or 9A (his).

Greg
 
Im not trying to get into an arguement - there is no argument here with you. I know what the company says about which engine to put into the 9. I have flown out of Aspen in the summer in a 9 with O320. It did fine.

My point is no different than pulling to the very end of the runway before you take off. Having a backup alternator or, making sure you have extra fuel - even more than needed. I didn't say an O320 was not up to the task flying out of Aspen. I do believe a O-360 is a safer choice in the high elevations. You may not - that's OK with me.

I have a Ford Explorer. When I pull onto the highway, it gives me plenty of power - when I am at lower elevations. When I am at Aspen or some of the other passes at or above 12,000', I would rather be driving my business partners McLaren. It gets onto the highway pretty quick. The McLaren can go much faster than is safe and when I drive it, I have to pay attention to it. I can go over speed in my Explorer too just like I could do in a 9 with a O320. You have to use good judgment in all situations in life. Not just flying.

I ended up with an O320 in my 9A. I had planned on an O360, but I got too good of a deal on my engine, so I jumped on it.

rvbuilder2002 said:
I get your point, but using that logic, why not put on a 200 HP instead of the just the 180?

My opinion is the same.
If a down draft in the mountains would be better dealt with by a particular pilot if he had 20 extra HP; with as capable of an airplane as the RV-9 is with 160 HP, I would say he is cutting it a bit to close.
In simpler terms, if an RV-9 pilot is using good judgement, he should never be in a spot where he was wishing for the small performance gain that 20 more HP would provide.
Even that statement is far to general, because in the example you gave, a 160 with constant speed would probably be better off than a 180 with a fixed pitch prop. at altitude in the mountains.
Click to expand...
 
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This has probably been beaten enough, but here are some of my thoughts, from a 9 builder, but not a 9 flyer yet:

1) There's no such thing as too much power, but there may be control issues.
2) Everything is a compromise.
3) The cheapest hp (in terms of $'s/hp) come in the form of a parallel valve O-360.
4) An airplane is a set of compromises including weight, hp, cost, and many others.

All that said, I am planning an O-340 fixed pitch, with a second choice O-360 FP and third choice O-320 CS. My final choice,however, may change more than a college freshman's declared degree,though...

Tim
 
IMHO, a CS prop will add more flexibility than anything else. Yes, $$$$, but I would choose an O-320 with a CS prop over any other engine with a FP prop. Especially for an RV-9/9A.

Full power available for T/O and Climb. Complete control of RPM and MP. Ability to maximize economy. What's not to like?

I really like my Whirlwind CS prop!!!!!!! :cool:
 
What limits the RV-9?s G loading?

Scott,

Engine size aside, what limits G loading on the -9? Knowing the fuselage is essentially the same as the -7, is it the longer wing or longer HS?

I ask because I have always been told the -9 is not aerobatic but there has been nothing more than "don't do it" from Van's.
 
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Returning to the OP's situation, I'm sure you've done it, but spend lot's of time poking around Van's site as well as VAF. Lot's of valuable info there, but you have to sometimes stumble across it. There's also lots of value in taking a peek at the bulletins and articles aimed at the other models in the line up.

http://vansaircraft.com/pdf/letters/buying_a_flying_rv.pdf

Ultimately, while we have much more freedom in the experimental arena we have a responsibility to educate ourselves. You are clearly doing that by reading and posting on VAF but it is really important to pay special attention to the info coming directly from the manufacturer. It is too easy to dismiss warnings as CYA from the folks who know the design inside and out, including the margins engineered into it and the unknown reasons for certain decisions. In a recent thread involving the rear spar Scott was discussing a flight regime and design point with structural load on the wings in the FORWARD direction which took me completely by surprise.

The threads discussing Vne being a True Airspeed also got bogged down by the confusion over what the reason for the limit was. The manufacturer has the last word. That said, after getting an understanding of what their stance is and learning about the qualifications of the various posters, in the experimental world we have the freedom to make our own decisions. Informed decisions are the best and you seem to be in the process of getting informed.

Education and Recreation!

Enjoy and welcome!
 
Good question

Good question Bill. I'm interested also.


N941WR said:
Scott,

Engine size aside, what limits G loading on the -9? Knowing the fuselage is essentially the same as the -7, is it the longer wing or longer HS?

I ask because I have always been told the -9 is not aerobatic but there has been nothing more than "don't do it" from Van's.
Click to expand...
 
Probably both the wings and the tail as stated: "The RV-9(A) is designed to utility category load requirements (4.4 G's)" Even engine mounts can be designed for such a category.
 
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LifeofReiley said:
... Even engine mounts can be designed for such a category.
Click to expand...
The -9 uses many of the same parts as the -7, including the engine mount. In fact, after some spin recovery issues with the -7, Van's replaced the -7's VS and rudder with those from the -9.

So the question still stands.
 
N941WR said:
The -9 uses many of the same parts as the -7, including the engine mount. In fact, after some spin recovery issues with the -7, Van's replaced the -7's VS and rudder with those from the -9.

So the question still stands.
Click to expand...

Hey Bill... I understand the mounts are the same, just stating mounts can be designed in this manner.
 
N941WR said:
Scott,

Engine size aside, what limits G loading on the -9? Knowing the fuselage is essentially the same as the -7, is it the longer wing or longer HS?

I ask because I have always been told the -9 is not aerobatic but there has been nothing more than "don't do it" from Van's.
Click to expand...

Actually, the 7 fuselage is the same as the 9... The RV-9 was introduced about 1.5 years before the RV-7

As is discussed here on a regular basis, the proper design of an aircraft is doing it as a whole package, and balance a large list of compromises.

The RV-9 began life with the intent that it would be designed to meet "normal" category certification requirements. In simple terms.... a non aerobatic airplane, designed with limit loads (the load limit a pilot is supposed to avoid exceeding) of 3.8 G's. So the wings and tail were engineered to be able to tolerate 3.8 G's at the selected max. gross weight of 1750 lbs.

The different assemblies were then statistically load tested to those weights, and confirmed to pass a number of different tests as prescribed by FAR 23.
Beyond that, if anyone is interested in a higher level of detail regarding why the recommended HP limit for the RV-9 is 160 HP, I suggest they read the article previously mentioned titled "ALL THE PRETTY HORSES". You can find it HERE (it is teh last 2 pages of the document).

If someone takes the time to read it carefully and understand each part before moving on, at the end you should have a good understanding of where the limitations on the RV-9 come from.

In a nut shell.... a properly established Vc speed is one that when an airplane is flying at or below that speed and it encounters a 50 FPS vertical gust (a certification standard based on turb. that can be encountered), it will not induce a load above the max load limit (in the case of the RV-9, 3.8 G's).

The Vc speed is the top of the green arc. An RV-9 with 180+ HP is capable of flying at indicated airspeeds well into the yellow arc range, in level flight. So, the issue has nothing to do with exceeding Vne in a decent, etc.

Ok, but wait a minute, the other 2 seat RV's are able to do the exact same thing when using bigger engines.
True, but there is one key difference, the rest of the 2 seat RV's (the RV-12 doesn't count in this discussion... it is an entirely different situation) are approved for aerobatics. So their structures are designed to take a 6 g's limit, instead of 3.8 (at a reduced aerobatic gross weight, but it still works out to a higher load capability), so there is a broader margin in regards to gust loading.
If we looked at a V-N diagram for the RV-7 to compare, we would see that the gust loading speed limit would graph out higher than it does for the RV-9, and that is why the Vc speed for the RV-7 and 8 is spec'ed at 193 MPH (Relatively close to what the average top end indicated speed in cruise is).

If people want to really understand some of the details regarding what established the limits on the aircraft they fly, read the articles and if needed, ask questions. For the case of the max. HP debate on the RV-9, the last article in the document is particularly relevant.
 
Scott...

Just wanting to clarify. In Post #10 it states:

Since it hasn't been discussed in a while I am adding relevant details....
The RV-9(A) is designed to utility category load requirements (4.4 G's)
It has a designed Vno (max. structural cruise speed / normal operating speed limit) that in certain circumstances can easily be exceeded with higher than 160 HP engines. This may be down played by some as trivial, but it is not.

**********************************************************

Now it's 3.8? Just don't want anybody getting confused. Thanks :)
 
Scott,

Thanks for the post. That helps some but still leaves me wondering if the difference is just in testing or actual weaker structure.

Meaning did Van's decide the -9 will be limited to 4.4/3.6 G's and stop testing when it hit those limits or did they test to destruction? If so, what failed and at what loading? Inquiring minds want to know.

Yes, I have read the document you referenced and still don't hit the numbers listed, although I am slightly closer than a lower powered -9, if I chose to fly that fast, which I don't.

As for the G loading, while cruising at 150 knots true, in clear / smooth air, I got hammered with a 4.1G positive bump. Thank you Van for designing such a strong airframe!
 
My mistake (the other post I mentioned it I got it right :eek:)
I edited post # 10.

If you look at the V-N diagram in the document I linked too, you can see that the top edge of the envelope is at 3.8 G's
 
Margins

So if an existing rv9 driver wanted to increase their margins, they could limit gross to 1600lb like the -6 and maybe drop 3ft off the wing with smaller wingtips. Of course, a lighter airframe with smaller wing area, now the little bugger has less drag and TAS is once again an issue. Might as well scrap it and buy a -14......😄😛
 
grubbat said:
So if an existing rv9 driver wanted to increase their margins, they could limit gross to 1600lb like the -6 and maybe drop 3ft off the wing with smaller wingtips. Of course, a lighter airframe with smaller wing area, now the little bugger has less drag and TAS is once again an issue. Might as well scrap it and buy a -14......😄😛
Click to expand...

You bring up a good point.

The -14 has a wing that is one foot shorter than the -9 and HS is the same design. So, what makes the -14 stronger? Thicker skins, more ribs, thicker spar?
 
N941WR said:
Thanks for the post. That helps some but still leaves me wondering if the difference is just in testing or actual weaker structure.

Meaning did Van's decide the -9 will be limited to 4.4/3.6 G's and stop testing when it hit those limits or did they test to destruction? If so, what failed and at what loading? Inquiring minds want to know.
Click to expand...

I am not really sure how to say it any more clearly....

I wrote....

rvbuilder2002 said:
The RV-9 began life with the intent that it would be designed to meet "normal" category certification requirements. In simple terms.... a non aerobatic airplane, designed with limit loads (the load limit a pilot is supposed to avoid exceeding) of 3.8 G's. So the wings and tail were engineered to be able to tolerate 3.8 G's at the selected max. gross weight of 1750 lbs.
Click to expand...

It means what it says.
The airplane was designed to be 3.8 G's and then was tested to prove that it met that.
I thought it was common knowledge at this point that the RV-9 was designed to be built with as low as a 118 HP engine. That requires keeping it light.... which in turn requires having no more structure than is necessary for the load that needs to be endured. The RV-9 wing is far from being an RV-7 wing (structurally) with a different airfoil shape.

If you say your airplane can't cruise at above 180 MPH indicated, either you have a very slow RV-9, or you don't understand the influence in altitude.
Up high the indicated will of course be well down in the green range, but down low, you should easily be able to get into the yellow range if you were to run at 75% power. The Vc limit (actually all speeds except for Vne) is based on indicated air speed.
 
N941WR said:
You bring up a good point.

The -14 has a wing that is one foot shorter than the -9 and HS is the same design. So, what makes the -14 stronger? Thicker skins, more ribs, thicker spar?
Click to expand...

I think maybe some of your confusion with details regarding the RV-9 design is some poor information you got somewhere, or some incorrect assumptions...

The RV-14 horizontal does share the same shape with the RV-9 (and RV-10), and it uses the same ribs, but it is no where near the same structure.
It is actually far closer to being the same as the RV-10, than it is the RV-9.
 
rvbuilder2002 said:
...
It means what it says.
...
If you say your airplane can't cruise at above 180 MPH indicated, either you have a very slow RV-9, or you don't understand the influence in altitude.
Up high the indicated will of course be well down in the green range, but down low, you should easily be able to get into the yellow range if you were to run at 75% power. The Vc limit (actually all speeds except for Vne) is based on indicated air speed.
Click to expand...

I guess I just never push it that hard. I must be too conservative. (And I could have a slow -9 but I kind of doubt it.)

Looking at some pictures I took in flight, my typical cruise is around 8500' MSL (DA is much higher) while doing ~50% power LOP (according to the SkyView), showing 134 Knots indicated and 156 KTAS, while burning 6.1 GPH. There is one flight I took at 15.5, indicating 120 knots, 158 KTAS, 43% LOP, and burning 5.2 GPH.

From my testing, after I first installed this engine, it will turn in 200 MPH (170 kts) at 8,000 DA, WOT, leaned for best power. That works out to close to 75% power but I do not recall what the indicated AS is. I'll have to go and do some more flights and play with power settings.

As I have said, I don't run it wide open and typically not at 75% power because I'm just not in that much of a hurry to get anywhere.

Thanks again for your input.
 
I say red flag

kaweeka said:
I have read several articles about overpowering these aircraft and the aerodynamic dangers possible and want some input from those that know much more than I if this should throw up red flags about non-standard building.
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Kaweeka, When a builder of a kit aircraft instals an engine more powerful than that allowed by the design engineer it could be for any number of reasons including:

a) He thinks he knows more than the design engineer despite the fact that he probably has absolutely no engineering background whatsoever.

b) He's easily influenced by the ignorance of others on forums (the blind leading the blind).

c) There's a part of his brain missing that correlates cause and effect.

d) He just wants to do it so he's gonna do it, and it is, he says, the "Experimental" category after all.

I would suggest to you that none of the above are optimum for the correct mindset in building an aircraft. Vans says max 160HP... builder says stuff that....I say red flag and expect other undesirable anomalies in the build. :(
 
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I just realized that this HP argument seems to only apply to the -9(A) and not a single person brings it up when -7 or -8 builders talk about adding more than 200 hp, except for installing an IO-540.

In addition, the conversation doesn't ever seem to include installing an (I)O-340 in a -9 (A), why is that?
 
N941WR said:
Not to worry Doug, you can't over speed an (I)O-360 powered -9(A) at any altitude with wide open throttle. However, point the nose downhill with any engine and you can over speed it, along with your engine.
Click to expand...

Several posts back, you made the above comment. Unfortunately, it's not entirely true. With too much power, you can fly level and exceed the Vne TAS. That's the point of this article: https://www.vansaircraft.com/pdf/hp_limts.pdf

I hope you have read it, and understand it.

If you limit the speed by pulling back the throttle, as you seem to do, then all is OK. But it you fly WOT at altitude with a 180 hp engine, you can get yourself into trouble.

Capiche?

And another thanks to Scott for his patience and participation on VAF!! :cool:
 
Pete,

Yes, I have read that article (a couple of times) and yes, I understand it and as I have said, I cannot hit Vne in level flight with an O-360.

Yes, Scott has been very patient but he still has not answered the basic question, and neither has anyone at Van's; since the -7 and -9 share many of the same parts what on the -9 is the limiting factor?

With that bit of information, some of us might like to make some changes. For example, I was once told the the HS is the weak point and that by adding the missing nose ribs it would be as strong as the -7's HS. If true, I would like that margin of safety, regardless of engine size.

All any of us get is, "It wasn't designed for anything over 160 hp, don't do it."
 
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Yes, Scott has been very patient but he still has not answered the basic question, and neither has anyone at Van's; since the -7 and -9 share many of the same parts what on the -9 is the limiting factor?
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Well, from the above discussion, the wings are.

With that bit of information, some of us might like to make some changes. For example, I was once told the the HS is the weak point and that by adding the missing nose ribs it would be as strong as the -7's HS. If true, I would like that margin of safety...
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So fit RV-7 wings will get some of the way.

All any of us get is, "It wasn't designed for anything over 160 hp, don't do it."
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Ummm... maybe there is a reason for that?

Designers do not start out building a 400Kt 300HP aircraft, and then remove a rib or something and now say it is a 160HP 180Kt aircraft. The whole aircraft is designed to a weight / 'g' / HP etc. specification. If you buy this aircraft instead of the 200HP / 200Kt, but want the 200HP / 200Kt spec, many of us might ask why?
 
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