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  #51  
Old 02-18-2020, 09:52 AM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by Aviaman View Post
I tend to get into the weeds in technical discussions. You motivated me to read the Kruger article again.
Let me discuss it as I understand the article.

Here’s what appears on page 1 of the article “Flying High and Fast”.

“No, the real problem is not mechanical. The real danger is exceeding the Never Exceed Speed, noted as Vne.” So far, no mention of Vno, but will come back to that.

Yes, at extreme altitudes TAS will become very high with sufficiently high IAS. The example he gave was with a turbonormalized engine, which is very unlike what we are discussing. A normally aspirated engine dramatically loses power with altitude. Because of this, my 360 does not exceed Vne, or even come close, in level flight at any altitude that I have flown. In any case, my EFIS computes and displays TAS. So IMO, exceeding Vne is not in the cards, (except in a dive.)
Now, maybe my engine underperforms (carbureted, fixed pitch prop) and others can go faster. But my own experience doesn’t support the possibility of exceeding Vne in level flight.

About Vno. That is the upper limit of the green arc (or the lower limit of the yellow arc). It’s generally understood to mean only go above that limit when in smooth air. Is that a guarantee of no high loads from unexpected gusts like what you described ? No. Flying in the yellow arc is a matter of judgement and the assumption of risk. However that limit was defined for the RV-9 Just like it was for any other standard category plane. (I have experienced sudden gusts like you described, so caution is advisable). There is no reason to regard that limit as defined differently from other aircraft. For the RV-9 its 180 mph IAS. One should give due caution to that limit as one would with any other plane.

I suspect this hp limit on RV-9s was motivated by Vans fearing that RV pilots would think RV-6 and 7 performance was to be expected or considered safe in the RV-9. No, that wouldn’t be a good idea. It is not stressed for acrobatics, and has lower load limits.
John,
The article was written as applicable to all RV models so it does apply to the RV-9 as well, but don't confuse that article with being the reason for the 160 HP recommendation for the RV-9.

The RV-9 is a slightly different breed of RV and has a lower max. HP limit than the other models for a different reason. I think I have now thoroughly explained the reason.
As you mentioned, Vno should be obeyed while flying any aircraft, to which I agree, but having been present and participated in the static load testing of the RV-9 wing and other major air-frame components, and having direct knowledge of many of its design details, I can stand behind my explanation of why there is a smaller engine recommendation specifically for the RV-9.
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  #52  
Old 02-18-2020, 10:22 AM
Vansconvert Vansconvert is offline
 
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Default Vno for a 7a

What is the vno for a 7A? I don't see that published anywhere on the Vans site.
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  #53  
Old 02-18-2020, 10:44 AM
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RV8JD RV8JD is offline
 
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Originally Posted by Vansconvert View Post
What is the vno for a 7A? I don't see that published anywhere on the Vans site.
Vno=193 MPH IAS. See this chart:

https://www.vansaircraft.com/faq/air...ings-by-model/
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  #54  
Old 02-18-2020, 10:44 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Vansconvert View Post
What is the vno for a 7A? I don't see that published anywhere on the Vans site.
Vno is the start of the yellow arc range in the following document -

https://www.vansaircraft.com/faq/air...ings-by-model/
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  #55  
Old 02-23-2020, 11:30 AM
NinerBikes NinerBikes is offline
 
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Surprised, other than the cost, no one talks about running a turbocharged motor at elevations above 10,000, in a RV-9.

No talk about ever running a Rotax 915 IS rated at 141 HP, and it's not losing HP at those elevations.

True, your climb rates won't be as good at lower elevations, but probably past 8000 feet and above, where the RV-9 wing does so well, it's still making good power, where a normally aspirated engine isn't. And it's pretty much FADEC capable. Fuel injection.

And to add some blasphemy, the engine is not a design from 1951 or 1953 when 320's and 360's first came out? Fresh design with current technology, manufacturing techniques and metallurgy. Car engine design, snowmobile engine design, jet ski design and other gasoline powered toys have not stood still. Any fresh new designs out of Lycoming lately? Just asking, for a friend. Wink.

Thoughts?

Sorry I am so simple minded... but if you want a o-360, why don't you build or buy something designed for it, a RV-6 or RV-7? Making something capable of doing something it was never designed for, is lost on me. Get the right tool for the flying mission.

Last edited by NinerBikes : 02-23-2020 at 11:42 AM.
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  #56  
Old 02-23-2020, 12:04 PM
Kyle Boatright Kyle Boatright is offline
 
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Quote:
Originally Posted by NinerBikes View Post

Thoughts?
Go for it. Keep us posted.
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  #57  
Old 02-23-2020, 03:48 PM
Aviaman Aviaman is offline
 
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Location: Louisville KY
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Quote:
Originally Posted by NinerBikes View Post
Surprised, other than the cost, no one talks about running a turbocharged motor at elevations above 10,000, in a RV-9.

No talk about ever running a Rotax 915 IS rated at 141 HP, and it's not losing HP at those elevations.

True, your climb rates won't be as good at lower elevations, but probably past 8000 feet and above, where the RV-9 wing does so well, it's still making good power, where a normally aspirated engine isn't. And it's pretty much FADEC capable. Fuel injection.

And to add some blasphemy, the engine is not a design from 1951 or 1953 when 320's and 360's first came out? Fresh design with current technology, manufacturing techniques and metallurgy. Car engine design, snowmobile engine design, jet ski design and other gasoline powered toys have not stood still. Any fresh new designs out of Lycoming lately? Just asking, for a friend. Wink.

Thoughts?

Sorry I am so simple minded... but if you want a o-360, why don't you build or buy something designed for it, a RV-6 or RV-7? Making something capable of doing something it was never designed for, is lost on me. Get the right tool for the flying mission.
Don’t get the message here. Apparently advocating supercharged experimental automotive/snowmobile power. And supercharged engines were the ones that the extreme >Vne air speeds were tabulated in the Kruger article. Yet the normally aspirated O-360 is somehow wrong.
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Cessna 170B-sold
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Vans RV-6 slider-sold
Vans RV-9A slider, flying
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Dues happily paid Jan 3, 2020

Last edited by Aviaman : 02-23-2020 at 03:51 PM.
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  #58  
Old 02-23-2020, 05:11 PM
NinerBikes NinerBikes is offline
 
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Quote:
Originally Posted by Aviaman View Post
Don’t get the message here. Apparently advocating supercharged experimental automotive/snowmobile power. And supercharged engines were the ones that the extreme >Vne air speeds were tabulated in the Kruger article. Yet the normally aspirated O-360 is somehow wrong.
Run a 141 HP turbocharged motor that is good for continuous 135 HP, has continuous power at higher elevations without loss, and doesn't exceed the Van's 160 HP max rated spec for a power plant that a o-320 recommendation by Van's, or go into the frowned upon 0-360 in a RV-12 request and getting Vno near Vne at higher elevations.


If you're on a tight budget.

Very easy to get a Yamaha snow mobile engine and call up Teal Jenkins for a gearbox. Or look up what Steve Henry is doing. 150 HP normally aspirated, and the motors are proving cheap and reliable, so far.
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  #59  
Old 03-06-2020, 10:14 AM
NinerBikes NinerBikes is offline
 
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Quote:
Originally Posted by Robert M View Post
The RV-9 can hit Vne really quickly by just pointing the nose down so engine size is really not a factor unless flying from higher elevations. I usually cruise at around 125 - 130 MPH, sipping gas. Bottom line, the choice is your, get what YOU want.
You'll get the same results, pointing the nose even slightly down, on a RV-12, if you don't back out of the throttle first, approaching the Vne.

These are really slippery little birds, which probably explains why they are so efficient with fuel.

I don't know if the RV-9 is as sporty with input to the stick for elevator as the RV-12 is, but it doesn't take much finger motion with a RV-12 to get it to change direction, at all, when you're at where the green and yellow meet on the tape on a Dynon Skyview Touch at about 107 kt IAS. Perhaps the RV-9 is a bit more relaxed?

We've run 91 with ethanol Mogas all winter long here in So CA, up to 9500 ft, and haven't had a hickup yet with the vapor pressure from the fuel messing with the floats in the carbs or vaporizing in a Rotax 912 ULS. Key word... "yet". Wondering if the really high elevation and what it does to the vapor pressure of Regular 87 w ethanol mogas winter fuel is part of the problem?

Last edited by NinerBikes : 03-06-2020 at 10:22 AM.
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