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I am afraid of my 360 powered RV 9A

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being safe comes in many forms and levels. Not sure what you are afraid of or concerned with. VNE/futter, aircraft control, exceeding G limits from wind gusts, etc.

I routinely fly to the edge of Vno and often beyond that in non-turbulent conditions.

Larry
 
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Since you referenced the Van's article on HP limits, Vne, and TAS, I assume you are concerned about Vne as a function of altitude.

Vne (Redline) for the RV-9/9A is 210 MPH TAS/182.5 KTAS (although you wouldn't know it from official Van's literature). The table on the left in the chart below shows Vne in terms of IAS at different altitudes for a Vne of 210 MPH TAS/182.5 KTAS.

i-wLv7VKD-M.jpg


Vno (Maximum Structural Cruising Speed) is 180 MPH IAS for the RV-9/9A. Note that at 10,000 ft, Vno is about equal to Vne. Above 10,000 ft, Vne is lower than Vno and governs.

Hope that helps,
 
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Don't be afraid...

...do more flying...

Per the manual, the Vne for the RV-9 is 210mph. Vno is 180. Va is 118mph

Consider the extra 20hp (assuming that you have an O-360 or IO-360-B variant of 180H.P.) a gift that yields shorter take off rolls, faster rate of climb, higher cruise, more performance margin...
 
Is it true that I am safe as long as I keep the true airspeed below 170 MPH?

Thank You.

Earl

No. Va is well below that. You need to better understand the conditions you encounter and how they relate to airframe safety. A full elevator pull at 170 will likely create serious damage.

Larry
 
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Earl,
I have a car that will do about 170mph. I dont drive it that fast. When I am on rough roads, I drive it much slower.
Considering you are north of me (KEUL), the extra hp will be nice in the mountains. I really wanted a 360 but got too good of a deal on a 320. Let me know if you want to trade!
 
The RV-9A standard engine of 160 hp is the same engine as used in Cessna 172s and Piper Cherokees, both 4 place planes. Based on that, the RV-9A is "overpowered", meaning it has a higher power to weight ratio, and this is responsible for its remarkable performance. A 180 hp (I)O-360 is only 12.5% more powerful, so you might even find the standard 160 hp engine "over your head" too. The solution is likely more training with a qualified instructor. And remember, the throttle works in both directions.
 
Yesterday afternoon I departed KSJT at 103F on the ground, don't even want to guess what the runway surface temperature was. Density altitude was 5800. Two butts in the seats and 28 gallons plus about 40 pounds in the baggage compartment. I came off the runway on an intersection departure and pitched for about 95 knots in the climb, about a minute and a half later Tower calls me and asks "What engine do you have in that thing?"

I was climbing at 1600/min in that heat with that load - and I wasn't really pushing it.

THAT'S why we (some of us, anyway) put 360's on the 9. It's not for flat-out speed, because it doesn't buy you any more Vne or Vno or Va - those are structural limits and you ignore them at your own peril. It's for the ability to get out of Indian Country and get up high quickly and let that wing do it's thing in mid teens where it wants to be.

Think of it this way - if you are worried about the extra horsepower, don't use it. Simply limit your maximum manifold pressure by 2" less than whatever airport you are taking off from, and you'll be equivalent to the 320. Just because you HAVE the extra horsepower doesn't mean you must use it. Just like a new car driver with a hopped-up mustang, ease into it gradually and feel it out, rather than going drifting around the street corners. The extra power is really nice when you want it - but it's optional, and you have the control literally in your hand.
 
With well over 2000hrs on our 160hp. If / When I get the chance, I'll be applying "more horsepower" to our old bird for the express purpose of time to climb to cooler temps and just a little more left in the tank at 14k'.

If the OP is still afraid of the 360, I can have my 320 off of the airframe tomorrow, ready for a trade :). A little more training can usually solve "fear".
 
I've been flying my O-360 powered -9 for a long time now.

As pointed out, the Vne for the -9(A) is 210 mph (180 knots) TAS.

Van's doesn't recommend this engine because they are afraid that you can exceed Vne with the bigger engine.

That may be possible, if you are flying at full power at sea level. At 8000' DA, mine trues out at 175 knots with 75% power.

If the nose goes down, it is easy to exceed the TAS but that was true back when my plane had a 140 hp O-290d2 up front.

My typical cruse speeds are around 160 knots TAS, so well below Vne.

If you are afraid of your -9A, then you need to see a specialist. IE, a competent CFI and go flying with him/her.
 
The 160 hp recommended limit is related to more than just Vne, and as many times as I have posted about it in the RV-9 forum, I am amazed that it is still the first thing mentioned by some of the veteran RV-9 pilots.......

Here is one of the most recent threads discussing the details
http://www.vansairforce.com/community/showthread.php?t=179222&highlight=vne

I agree that if the limiting speeds are obeyed, it doesn't matter what engine is in the airplane, but as I have mentioned repeatedly in the past, the scary thing is how many people flying with bigger than recommended engines obviously don't understand what all the limiting factors are. And that is why nothing bigger than a 160 HP engine is recommended.
 
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Airguy, loved that :)

On the other hand, flew the airlines for almost 20 years, and seldom did we use full power... jet engines, yes.
Nevertheless, when flexing (yes ladies & gents, it’s what’s its called in the jet world) for I’d say 99% of the TOs gave us say a good 5 to 6K/fpm on a 60 or so K tons A320, this climbing at Green dot around 230 KIAS... and this is the civilian world only :rolleyes:

Yet to fly an overpowered aircraft, patiently waiting... ;)
 
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The club

It is a nice thing to be at pattern altitude halfway down the runway. The CS prop and high HP give a very satisfying climb. Thousand one thousand two, lift off, climb like crazy, plenty of margin for engine failure
 
It is a nice thing to be at pattern altitude halfway down the runway. The CS prop and high HP give a very satisfying climb. Thousand one thousand two, lift off, climb like crazy, plenty of margin for engine failure

This is true.. A few weeks back, I was doing pattern work at an airport about 1400' MSL. By the end of the 5000' runway, I was at 1000' AGL, and had already trimmed and powered back.. :cool:

I too have a 360-powered 9A. I spent some time researching this, and IMO, there's nothing inherently dangerous about the 360 in a RV-9.. BUT it does require the pilot to have a some knowledge of why Van's does not endorse the 360 for the RV-9. Surprisingly, despite the information being out there, very few possess this knowledge.
 
Think of it this way: even if your truck does have the ground clearance, you wouldn't hop the curb at 60 miles an hour. You'd do some damage, and might even lose control, right? Same thing in a plane.

Va, Vc, and Vne are each applicable in specific flight conditions. Understanding them will keep you safe. As long and your airplane in airworthy, not exceeding each limiting V speed for the condition of flight is your safety margin. How much margin you need is up to you and controlled by AoA and correct throttle use.
 
Airguy, loved that :)

On the other hand, flew the airlines for almost 20 years, and seldom did we use full power... jet engines, yes
)
But, you also did every takeoff with the option to either stop, or go. With a single you have the option to stop, or something else. I personally think the risk (reduced power takeoff) is low, but why take it when there is no compelling reason? (Okay, maybe noise is a reason in some places). Altitude is usually your friend.
 
FWIW
After 1000 hours in my RV-9A there are times the extra HP would come in handy. Don't be "afraid" of the extra HP just be attentive when you fly. Consider the extra 20 a gift.
David
 
Yet to fly an overpowered aircraft, patiently waiting... ;)

Me too! There's certantly been times I wish I had more power. It's really easy to have less power by just closing the throttle to the desired amount.

Joking aside, just watch the airspeed and reduce power as needed if getting too close to the limit.
 
I have spent extensive time online reading about overpowered 9As. My 9A is a 360 powered one, and I've realized that I am in over my head.

I am wondering, to be cautious should I make redline of my 9A Vc, which appears to be about 170 MPH. https://www.vansaircraft.com/wp-content/uploads/2019/02/hp_limts.pdf

Is it true that I am safe as long as I keep the true airspeed below 170 MPH?

Thank You.

Earl

It is ok and a little bit health to be afraid of an airplane. That helps keep you from doing things that you should not be doing.

What are you actually afraid of?
The engine will quit running?
The airplane falling apart?
The way the airplane flys? The quick sporty handling of RV aircraft can be scary to someone that has thousand of hours in SPAM cans.

The airplane does not know what kind of engine is pulling it through the air. The laws of physics will increase load on the airplane as it reaches higher speeds.

Typically aircraft require squaring the power to overcome the drag of the airframe to double the speed. Increasing horsepower from 160 to 180 is about a 13% increase in power. Yes that will make the airplane faster but typically one can retard the throttle (reduce manifold pressure) or decrease RPM to keep the HP at the same as a recommended 160 HP engine would produce at that altitude.

I once was asked to fly a 260 HP RV-8 solo on a several hour cross country flight. I flew the airplane local to get familiar with the handling of the HEAVY RV. It flew like a heavy RV but had a fantastic rate of acceleration and climb. It was a nice flying RV. It flew a lot like my 160 HP RV-6 when it was heavy BUT had a lot more acceleration and climb than my RV-6 did when light and solo. The trip was nice and enjoyable. I pulled power back in cruise to fly similar speeds and fuel burn that a typically RV-8 with 180 HP would see. When decening, one also keeps attention on airspeed so as to observe the law of physics and keep the aircraft flying in the middle of the performance envelope like it would with a smaller HP engine.

It is possible that you have an airplane that is not right for you. Being an EXPERIMENTAL airplane it can be changed to what you want. The TCDS lists the 360 as 10-pounds more weight than the 320 but 20 HP more. Lycoming does have some engines DERATED to lower HP. Typically this is done by limiting RPM and or manifold pressure. Evaluate all the different ways that the engine can be derated to not produce more than 160 HP at sea level. Yes lower compression pistons could be installed but if you are comfortable having the governor adjusted to limit RPM you can accomplish the same thing.

IF all this still scares you, only you can decide what comes next. Engine swap to the recommended 320 or sell / trade the aircraft for one that is less scary.
 
Have no fear

'Scary' is an underpowered airplane in a high density altitude situation. My 9A with an EFII equipped 0-320 makes an estimated 175 hp. Gross weight takeoffs at lower altitudes at 100 deg oat are not a problem--easy 1000 fpm without 'pushing it' with high angles of attack. Departing out of a mountain airport with a D/A of close to 7000 ft at 110 kts resulted in an 800 fpm 'easy climb'. Enjoy the extra margin you get with more climb power, pull the throttle back and enjoy the reduced fuel burn while still doing an easy 150kts or better.
I've experienced gross weight 172s on hot days--'unpleasant' is a word I'd use to described those flights. 'Do-able' --yes. Within limits--yes...but not fun....RVs have limits just like any other aircraft---it's just the limits are farther out than you're used to flying lower powered certified planes.
 
OP's response?

Earl, 22 responses later, do you have any thoughts on the posts to date? Do you have a better idea for an action plan to get the confidence you deserve when flying your aircraft?

Personally, I find the 9/9A a delightful plane to fly - with either engine - by knowing and respecting their limitations.
 
Hi Earl, just wondering if you have the IO 360 D1A. It’s my understanding this is the 160 hp @ 2375 rpms. The later 172 Skyhawks used this engine of 360 ci for commonality by the manufacture but there was a limiting plate install to keep the aircraft at 160 hp. I too wanted to look at the D1A but a great deal at Sun-N-Fun from Vans on the IO 320 then added a wonderful CATTO prop!!! Flying 170 series Cessnas and Pipers for 45 years the 9A is delightful change. Just remember the farther the throttle goes in the faster the money goes out of your wallet for fuel! Like The pilots have said you’ll love it’s performance with 160 horse and I wholeheartedly agree. Beside the faster you go the less time you have to enjoy the scenery. And by the way you’ll love the rudder on the 9A too! I too enjoyed all the comments by the pilots and instructors for your post. Reading all of them was like going back to school but with excellent examples and feelings.Enjoy my friend Vans world of Flying!
 
The TAS redline (Vne) of the RV9A is 210mph not 170 mph. What are you worried about? I have an O-360 powered RV9A and have never exceeded 185mph WOT at any alitiude that I fly at (below 10,000). The extra power really helps in takeoff and climb performance. Just not an issue IMO. Of course TAS rises for a given IAS as altitude increases. My EFIS computes TAS, so that is what I am always seeing. I have never been close to Vne.
 
The 160 hp recommended limit is related to more than just Vne, and as many times as I have posted about it in the RV-9 forum, I am amazed that it is still the first thing mentioned by some of the veteran RV-9 pilots.......

Here is one of the most recent threads discussing the details
http://www.vansairforce.com/community/showthread.php?t=179222&highlight=vne

I agree that if the limiting speeds are obeyed, it doesn't matter what engine is in the airplane, but as I have mentioned repeatedly in the past, the scary thing is how many people flying with bigger than recommended engines obviously don't understand what all the limiting factors are. And that is why nothing bigger than a 160 HP engine is recommended.

The TAS redline (Vne) of the RV9A is 210mph not 170 mph. What are you worried about? I have an O-360 powered RV9A and have never exceeded 185mph WOT at any alitiude that I fly at (below 10,000). The extra power really helps in takeoff and climb performance. Just not an issue IMO. Of course TAS rises for a given IAS as altitude increases. My EFIS computes TAS, so that is what I am always seeing. I have never been close to Vne.

Not to pick on you specifically John, but you perfectly prove my previous point.

Vne is not the only limit speed that RV-9(A) flyers need to keep in mind.
 
What is the REAL issue ?

1- You can?t hold Van accountable for CYA when 180HP can exceed his design criteria.
2-Does anyone know factually that a 10lb heavier engine with 180HP does not exceed some structural limit in the mount or airframe within published G limits , harmonic sympathies or maneuvering speed ?
3- If you assume responsibility for the unknowns above, you are the PIC. You control TAS

Just an observation from a gearhead with much less pilot cred than most people sharing there brain on this forum.
 
2-Does anyone know factually that a 10lb heavier engine with 180HP does not exceed some structural limit in the mount or airframe within published G limits , harmonic sympathies or maneuvering speed ?
...

Factually, I do know that at 1068 lbs empty, my O-360 powered -9 is lighter than my friend's O-320 powered -9A with a CS prop on the front.

As for Scott's concern about observing the yellow line, I simply don't cruise my plane at 75% because at those speeds it is DRINKING 100LL and with only 36 gallons on board, I would rather slow down to go faster, meaning I typically cruise around 150 to 155 knots burning around 7 GPH or less.

(If I slow to 130 knots my fuel consumption drops to around 5 GPH or less.)

The other thing about the -9(A) is, with its long wing, it is simply not comfortable hammering along in turbulence. When it is bumpy I slow down so they feel more like rollers than potholes and I hand fly it. I would do that even when I had only 135 hp up front.
 
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@rvbuilder2002

?Not to pick on you specifically John, but you perfectly prove my previous point.
Vne is not the only limit speed that RV-9(A) flyers need to keep in mind.?

Did I say Vne is the ONLY limit speed that RV-9A flyers need to keep in mind? No, I didn?t. Of course there are other speeds. Many of them. I was confining my remark to a specific speed, Vne.
 
Scott has to poo-poo the extra horsepower, it kinda comes with the job. It gets tiresome and old, but it's understandable. If Van doesn't like it, Scott doesn't get to like it.

[ed. Text removed. Crossed my civility line. Please play nice, folks, v/r,dr]


The airplane would fly fine with a 250hp engine in it, if you could get it to balance and make the engine mount handle the weight/torque. The same V-speed limits would still apply, and Vne is only one of them. Other limits include total weight on the gear, and total weight on the nosewheel regardless of CG. These limits come into play when making deviations from the "standard" and you exceed them at your own peril - but you can certainly deviate from the standard and have an excellent performing airplane as long as you remember that you are the PIC and responsible for keeping the airplane inside it's originally designed structural envelope. That includes V-speeds, gear limitations, and before Scott points it out "other limitations" not listed here.

Now before you guys start thinking I have an axe to grind with Scott, that's really only partially true - I just get tired of hearing the same story over and over. [ed. Text removed. Crossed my civility line. Please play nice, folks, v/r,dr] , but he's a good doctor.
 
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The airplane would fly fine with a 250hp engine in it, .

Please don?t tempt me. I?ve got a 290hp lycoming and a 3blade prop sittin on the hangar floor just waiting for a nice project.

By the way, Scott is just doing his job. A lot of kids now days don?t know the dangers of the thin yellow line, the importance of TAS, and what happens when you point the little nose down with the throttle thingy all the way in. Why, I remember just a month ago an all knowing flight instructor was telling his student that the RV was a IAS airplane. I kindly shared with said fellow that the RV-9 flies just fine at 14,000 ft and one better not be relying on IAS at that airspeed. So, as much as I hate to admit it, Scott has to share on a routine basis the things that we know to be true but others are ignorant about.

Now, imagine a 290hp -9 on takeoff........ nawwwww, the 200hp io360 is all ya need.....😄
 
2-Does anyone know factually that a 10lb heavier engine with 180HP does not exceed some structural limit in the mount or airframe within published G limits , harmonic sympathies or maneuvering speed ?

On the page linked below from an earlier thread on 180 HP engines on RV-9s, Scott M. ("rvbuilder2002") indicated that there are NO structural design reasons that would preclude the installation of a 180 HP engine on RV-9s. See Post #32.

http://www.vansairforce.com/community/showthread.php?t=179222&highlight=vno&page=4

Note that everything in this current thread has been hashed out in many previous threads, including the one linked above.
 
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This never ending debate is not much different than the inflated GW builder's assign their aircraft.

Before Dan C. took down his site, he was building a database of finished RV's that included the engines and props installed along with their empty and gross weights. It also included their CG number and fuel capacity.

Dan gave me a copy of that database for some research I was doing at the time.

In reviewing the data there were 87 RV-7 and -7A's. Of those 34 had inflated their GW's, with 26 raising it more than 50 lbs and one going up to 2000 lbs.

Of the 23 RV-9 and -9A's on the list, 10 bumped their GW's above the 1750 design limit, with seven of those set at 1850 lbs. No one went higher than 1850 lbs in the list.

In looking at the list, of the 23 RV-9/9A's, 17 had O-320's, three had Subaru engines, and three had O-360's.

The -8 builders seem to be more conservative. The list includes 48 and of those only five went above the 1800 lbs design weight. However, the highest is set at 2270 lbs.

After looking at the data, my question is, is there a lessor of two evils? Exceeding the HP or the GW design limits?

I know the conservative answer is, "Neither". However, those airplanes with the larger engines and increased GW's aren't falling out of the skies.

Just some rambling numbers.
 
Is the GW increase split into MTOW / MLW with MLW being the normal GW or does everything go up?
 
....
The majority of the time it is for the literally thousands of lurkers.... in the hope that they will think twice before the believe everything the read here on VAF (and I happen to know that Doug will probably be nodding his head and chuckling if/when he reads this)
 
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Thank you for all of the wonderful replies.

I am not afraid of the speed, I have flown faster airplanes. I am afraid that I am too much of a test pilot.

Even in this thread, there is no concurrence of exactly what it is that makes the -9 airframe not suited for a 360 motor. Some say it is. Some say you've got to watch Va. Some say you have to watch Vne. Some say it's the top of the green arc that you have to watch.

Va, Vne, and the top of the green, you have to watch in every airplane. Sure it approaches faster in the RV-9 airframe with 180 horsepower, but that can't possibly be what makes the airplane not suited for an IO-360 per Van's.

Methinks that you can be doing everything right, flying around at 75% power at 6-8,000' and get a gust and end up with a severely disabled aircraft on your hands.. Confirm or deny?

Is it accurate to say that flying at 65% power is safer than 75% power when the engine is able to produce either one? Does that in fact give more gust margin? I believe so.
 
...

Va, Vne, and the top of the green, you have to watch in every airplane. Sure it approaches faster in the RV-9 airframe with 180 horsepower, but that can't possibly be what makes the airplane not suited for an IO-360 per Van's.

...

Va can be exceeded with an O-235 up front.

My biggest concern is cruising along and hitting a bump that jambs my head into the canopy so hard it incapacitates me, not that the airframe is compromised.
 
Options

I've read all 37 of these posts and like conventional vs trike, prime or not, black or white, we will never get a right answer.
Scott gives you factual answers and guidance, others offer information on how it has been done, and still others offer opinions.
The bottom line is if you have any doubt at all about your safety in your airplane, this wonderful VAF site offers you a perfect escape route.

It?s called the ?Classifieds?.
 
Another option

There is one more option I have not heard mentioned. Allow me to suggest getting an RV qualified flight instructor to give you training in your 9A. There are some very good ones here on the site. Your aircraft is very capable but at the same time quite forgiving. Proper flight instruction could show you the capabilities and give you the skill and confidence to use them.
 
I can’t say that I know Scott, but we have met and had a very good conversation. My takeaway from meeting and talking with him is he is no average, garden variety A&P. He knows his stuff. There is no question that he is one of the authorities on RV’s. My .03.
 
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Sure it approaches faster in the RV-9 airframe with 180 horsepower, but that can't possibly be what makes the airplane not suited for an IO-360 per Van's.

Actually, that is pretty much the reason given, along with the ability to maintain higher speeds. Van's has a multiple page document discussing exactly this issue and the reasons for their concern. It is a very well written document and I strongly suggest you read it if you want the manufacturers perspective on this issue. It goes into great detail about the potential risks and why they exist.

Can't remember exactly where it is, but believe it is on vans website. I am sure Scott can provide a link.

Remember, Vans is all about safety and protecting the brand's reputation. They specify an engine that minimizes the risk potential for the large pilotting population. As you add more power that allows you to more easily exceed speed limits, you increase the risk of airframe failure due to pilot error. I suspect Van's would not have an issue with a Bob Hoover protege' installing a 360. However, they can't assume that level of competence across the pilot population. They have to assume a meaningfull percentage of pilots will either not understand or respect the limitations and/or how to deal with them in difficult situations.

Larry
 
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No. Va is well below that. You need to better understand the conditions you encounter and how they relate to airframe safety. A full elevator pull at 170 will likely create serious damage.

Larry

The above is a very true statement. But seriously, who would pull full aft stick at not only cruise speed, but something like full power. You should expect to die in anything but a fighter if you do that. You would be pulling many Gs. I don’t think that is what you intended when you bought a 9. The 2 most important jobs of a pilot are to manage airspeed at both top and bottom ends of the speed range and to not hit anything. Cruise below vno in calm air and at or below Va in bumpy weather and enjoy your airplane. Use that extra power to get out of tight strips and climb to altitude like a scalded cat. Sounds like a great airplane. If it is a constant speed prop even better. You might need headrests to avoid whiplash on takeoff!
 
The above is a very true statement. But seriously, who would pull full aft stick at not only cruise speed, but something like full power. You should expect to die in anything but a fighter if you do that. You would be pulling many Gs. I don’t think that is what you intended when you bought a 9. The 2 most important jobs of a pilot are to manage airspeed at both top and bottom ends of the speed range and to not hit anything. Cruise below vno in calm air and at or below Va in bumpy weather and enjoy your airplane. Use that extra power to get out of tight strips and climb to altitude like a scalded cat. Sounds like a great airplane. If it is a constant speed prop even better. You might need headrests to avoid whiplash on takeoff!

I was simply replying to the OP's question "will I be safe if I keep my speed below 170." That type of approach is dangerous. I was simply making the point that a pilot must be aware of all critical speeds and understand the various conditions that present risks. It not just about airspeed. It must be related to G loading, whether the pilot doing it via the elevator or mother nature doing it for him. The higher the speed, the greater amount of G load seen on the airframe before it self-corrects via stall. The article I referenced does a very good job explaining "the envelope."

I did not mean to offend anyone. However, I hate to see folks not fully understand their risks.
 
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I did not mean to offend anyone. However, I hate to see folks not fully understand their risks.

Same here

But this thread shows that there are still many people out there that don't.
Because of that, I will not stop correcting incorrect or incomplete information.

Those that don't like it..... aren't being forced to read it.
 
There is one more option I have not heard mentioned. Allow me to suggest getting an RV qualified flight instructor to give you training in your 9A. There are some very good ones here on the site. Your aircraft is very capable but at the same time quite forgiving. Proper flight instruction could show you the capabilities and give you the skill and confidence to use them.

If you go this route, make sure your "RV qualified flight instructor" knows how to fly an RV-9(A).

I helped out one pilot who got his checkout from a CFI in the Atlanta area who had never flown a -9 before. It turns out the CFI gave the guy some REALLY bad advice regarding approach speeds, where to place his hand on the stick, etc. Once we corrected the bad advice the new RV-9 owner had no issues flying his plane.

The -9 flies like the other RV's but in the pattern you have to slow it way down and 90 on final just doesn't work well with the -9(A).
 
You're right, he knows his stuff, and I said as much in my last post. I've met him too, and was impressed with his store of knowledge that he could recite from memory - though it was several years ago and I doubt he remembers it, there were quite a few people there at the time.

Maybe I'm just getting old and cranky - but I think that when people are asking questions and trying to become educated about the issues, there are better ways to answer the questions than "Those aren't the only reasons why..."

The logical thing to do would be to EXPLAIN those reasons. List them out, show why they are critical, explain what happens if they are ignored. Scott knows all these things, but prefers to say "You can't do that" without expanding on the statement - and the expansion/explanation is the core of the question.

As has been noted, the majority of us here know these things - the rest are trying to learn. Educate them, please! [ed. Text removed. Crossed my civility line. Please play nice, folks, v/r,dr]

I'll go sit down and shut up and grumble to myself now. Peace.
 
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Earl,
Since you have posed some specific questions, I will try and give some specific answers as the pertain to the RV-9(A)

Even in this thread, there is no concurrence of exactly what it is that makes the -9 airframe not suited for a 360 motor. Some say it is. Some say you've got to watch Va. Some say you have to watch Vne. Some say it's the top of the green arc that you have to watch.

Your correct, not a lot of specifics have been given in this thread but other threads where it has, have been mentioned and links provided.
The primary reason is the Vno speed (top of the green arc).

Why is that you may wonder?

Because it is fairly common within the non professional pilot community (the largest percentage of us flying RV's) to not have a good understanding of what Vno is about.

That is understandable since the certificated airplanes that the majority of us have flown, do not exceed that speed in normal operation cruise flight.

If we use the Piper Warrior / Archer as an example... it is an airplane available with 160 or 180 HP, but in either of those engine configurations it will not exceed Vno in any level flight cruise condition. That means that to some degree it doesn't matter whether a particular pilot has an understanding of the importance of Vno other than during a decent.
That is somewhat compensated for as well. Since they have fixed pitch props, if a very steep decent is made, the throttle needs to be closed some to avoid exceeding normal RPM ranges... This slightly reduces the speed which obviously helps stay in the green range.

Contrast this with the RV-9(A)
With a 160 HP engine, depending on altitude, An RV-9 can fly at indicated airspeeds (Vno is based on indicated) right at or even slightly above Vno (into the yellow arc range). With a 180 engine it can cruise well into the yellow arc range.

Why is this so important to understand when compared to the other RV's?Because with the exception of the RV-10, it is the only RV that can fly in the yellow arc range in level cruise flight, that wasn't designed to aerobatic load limits. This reduces the safety margin compared to the aerobatic airplanes from gust loading in cruise flight.

So what does the Vno speed mean?
In simple terms, it is the speed that at or below, the airplane is safe from structural damage, at up to the design gross weight, if the airplane experiences the FAA designated design standard of 50 feet per second gust loading from turbulance.
Does this mean that turbulance is never higher than that?
No
It is just a standard is considered conservative to the level typically encountered in turbulance.

RV enthusiasts tend to lump all RV's together. It is common to hear comments like "RV's are built like trucks" "Van's is way conservative in the specifications they publish", etc.
This is dangerous thinking with the RV-9 because of the reason already mentioned. It was specifically not designed to aerobatic load requirements.

That makes operating in the yellow arc that much higher of a risk.

Pleas don't twist my words into thinking that the yellow arc is unimportant for the other RV models. It is. Just maybe not to quite the same level of urgency as the RV-9.

So in a nut shell, the 160 hp engine recommendation really is predominately because of the speed attainable, and the structural design of the airplane (not to aerobatic load requirements), factored against the lack of understanding of the typical non professional pilot


Va, Vne, and the top of the green, you have to watch in every airplane. Sure it approaches faster in the RV-9 airframe with 180 horsepower, but that can't possibly be what makes the airplane not suited for an IO-360 per Van's.

Methinks that you can be doing everything right, flying around at 75% power at 6-8,000' and get a gust and end up with a severely disabled aircraft on your hands.. Confirm or deny?

Is it accurate to say that flying at 65% power is safer than 75% power when the engine is able to produce either one? Does that in fact give more gust margin? I believe so.

You are correct. All limiting speeds need to be given respect for all airplanes.
Hopefully it is now clear what the specific reason is for the lower HP recommendation on the RV-9, and that you have an understanding of what needs to be done to operate your safely with a larger than recommended engine.
 
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.... I also get tired of feeling like I post an important operational detail and then some of the very active forum participants continue to ignore it.
Fully their prerogative, but the "get tired of " works in both directions.

Another reason for the type of comment you mentioned is lack of time to go into detail... particularly when there is already info in the thread, or links to it, that covers it. But it is usually because I have done so many many times (I guess I should just bookmark links and put them in posts......)

So I agree that I may not always take the time to explain, but I just did in my last post (for the who knows how manyth time :rolleyes:)

.....
 
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