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-   -   RV9 200HP Yamaha Sidewinder (https://vansairforce.net/community/showthread.php?t=207338)

Teal 06-19-2022 03:41 PM

Quote:

Originally Posted by SPX (Post 1614850)
You can also learn more in this thread: Vne: Indicated -v- True Airspeed



And that is exactly why Vne is TAS based.

Thank You for all the information. I will study it closely and carefully consider The TAS numbers in my VNE calculation.

RV8iator 06-19-2022 03:54 PM

Quote:

Originally Posted by Teal (Post 1614857)
Thank You for all the information. I will study it closely and carefully consider The TAS numbers in my VNE calculation.

It is the truth. VNE for these planes are TAS.
Ignore this at your own peril.

DanH 06-19-2022 04:40 PM

Quote:

Originally Posted by SPX (Post 1614848)
Page 3 directly mentioned Vne being TAS, but this entire PDF is applicable.
Sorry to be the one to give the bad news.

https://www.vansaircraft.com/wp-cont...1/hp_limts.pdf

Nobody joking here Teal. The RV-7 and the RV-9 share the same vertical stabilizer and rudder. Our community has already suffered some fatalities due to apparent flutter during known overspeed events. So far, I think they have all been 7's, but please note the 7 is standard with 180HP, some have as much as 215, and acro is allowed. As you know, a -9 is typically 160, no acro . No prize for being the first pilot to rip a -9 rudder.

Teal 06-19-2022 07:19 PM

Quote:

Originally Posted by RV8iator (Post 1614859)
It is the truth. VNE for these planes are TAS.
Ignore this at your own peril.

I do appreciate every ones concerns for my safety. I think conservatively maintain the TAS numbers under 210MPH for this application is prudent anyways and I will do so. Again thinks for sharing the information.
To use TAS instead IAS as VNE is conservative and a way to keep from having to do calculations to see how much fludder margin there is at a given altitude and speed. I am fine with that. But to point blank say VNE for these planes, TAS and IAS are the same is a fallacy.

wilddog 06-19-2022 07:53 PM

WOW Teal,
Great work! Please keep us updated.

grubbat 06-19-2022 08:33 PM

IAS and TAS
 
After all these years, Iím amazed that we are still discussing the IAS and TAS limitations on the RV. Last week I had this same discussion with a know-it-all airline pilot who simply did not agree that these planes are TAS limited.

I love my RV-9 but descending out of 17,000 ft is a TAS exercise that I never had to worry about in my Aerostar or Comanche. I love the high flying efficient -9 but itís a different animal that requires fitness. The margins are tight on that rudder.

Good job taking the advise of the folks here about TAS. Nobody here wants to lose yet another RV driver due to willful ignorance. We love the design, especially the -9.

RVbySDI 06-19-2022 10:42 PM

Quote:

Originally Posted by Teal (Post 1614878)
I do appreciate every ones concerns for my safety. I think conservatively maintain the TAS numbers under 210MPH for this application is prudent anyways and I will do so. Again thinks for sharing the information.
To use TAS instead IAS as VNE is conservative and a way to keep from having to do calculations to see how much fludder margin there is at a given altitude and speed. I am fine with that. But to point blank say VNE for these planes, TAS and IAS are the same is a fallacy.

Ok, I am going to add to this conversation as a fellow RV9A flyer who is running a higher HP engine than the recommended max 160 HP recommended by VANS.

PLEASE NOTE! VNE is NOT the only restrictive speed to pay attention to when flying an RV9(A). The point others have made concerning TAS vs IAS is valid not only for VNE but also for MAX cruise speed. And, you are familiar with the maneuvering speed right (118mph)?

If you thoroughly study the article written many years ago and sent out by VANS about speed limitations of the RV9(A) there is a substantial amount of print devoted to the MAX cruise speed for the 9 (which is also based upon TAS). There are ďmarginsĒ to pay attention to in cruise also and NOT just at the max VNE speed.

Your experimentation is very interesting. I wish you the best and look forward to your findings. More than anything else though, I look forward to talking to you in person someday at OSH, Petit Jean or some other fly-in. If you pay attention to these things being posted here, I am confident you will have a lot to show and tell us at those gatherings.

Scott Hersha 06-20-2022 08:13 AM

[quote=RVbySDI;1614914]Ok, I am going to add to this conversation as a fellow RV9A flyer who is running a higher HP engine than the recommended max 160 HP recommended by VANS.

PLEASE NOTE! VNE is NOT the only restrictive speed to pay attention to when flying an RV9(A). The point others have made concerning TAS vs IAS is valid not only for VNE but also for MAX cruise speed. And, you are familiar with the maneuvering speed right (118mph)? [quote]

If you thoroughly study the article written many years ago and sent out by VANS about speed limitations of the RV9(A) there is a substantial amount of print devoted to the MAX cruise speed for the 9 (which is also based upon TAS). There are “margins” to pay attention to in cruise also and NOT just at the max VNE speed.

—————————————————————————————————————-

OK, now I’m confused. I thought that the redline Vne was based on TAS for meeting designed flutter margins. Isn’t maneuvering speed and max structural cruising speed based airframe structural load limits? If so, doesn’t that depend on IAS (calibrated)?

lr172 06-20-2022 08:46 AM

Quote:

Originally Posted by RVbySDI (Post 1614914)
Ok, I am going to add to this conversation as a fellow RV9A flyer who is running a higher HP engine than the recommended max 160 HP recommended by VANS.

PLEASE NOTE! VNE is NOT the only restrictive speed to pay attention to when flying an RV9(A). The point others have made concerning TAS vs IAS is valid not only for VNE but also for MAX cruise speed. And, you are familiar with the maneuvering speed right (118mph)?

If you thoroughly study the article written many years ago and sent out by VANS about speed limitations of the RV9(A) there is a substantial amount of print devoted to the MAX cruise speed for the 9 (which is also based upon TAS). There are “margins” to pay attention to in cruise also and NOT just at the max VNE speed.

Your experimentation is very interesting. I wish you the best and look forward to your findings. More than anything else though, I look forward to talking to you in person someday at OSH, Petit Jean or some other fly-in. If you pay attention to these things being posted here, I am confident you will have a lot to show and tell us at those gatherings.

Let's limit the fear mongering and get the facts straight. What is it that you are calling max cruise speed, as that is not a std aviation term? If you are referring to Vno, which is NOT a max cruise speed, that is related to the speed below which a 50 fps vertical gust will send the wing into a stall before reaching the structural load limit of the wing. Those dynamics are always measured in IAS, as stall speed is always related IAS not TAS, and Van's has no guidance suggesting TAS should be used instead of IAS for Vno. Generally speaking, Vno is recommended as a max speed in conditions OTHER than clear, non-turbulent air. The challenge with Vne is flutter and flutter is based upon velocity and not wing lift dynamics, therefore TAS and not IAS. Many other planes get away with IAS limit, as they just don't go fast enough at ANY altitude to warrent a TAS limit.

Larry

RVbySDI 06-20-2022 10:03 AM

Quote:

Originally Posted by lr172 (Post 1614959)
Let's limit the fear mongering and get the facts straight. What is it that you are calling max cruise speed, as that is not a std aviation term? If you are referring to Vno, which is NOT a max cruise speed, that is related to the speed below which a 50 fps vertical gust will send the wing into a stall before reaching the structural load limit of the wing. Those dynamics are always measured in IAS, as stall speed is always related IAS not TAS, and Van's has no guidance suggesting TAS should be used instead of IAS for Vno. Generally speaking, Vno is recommended as a max speed in conditions OTHER than clear, non-turbulent air. The challenge with Vne is flutter and flutter is based upon velocity and not wing lift dynamics, therefore TAS and not IAS. Many other planes get away with IAS limit, as they just don't go fast enough at ANY altitude to warrent a TAS limit.

Larry

I am referring to the article written by Ken Krueger and the graph on page 3 that can be found in this article:
https://www.vansaircraft.com/wp-cont...1/hp_limts.pdf

To be clear, my post is not motivated by “fear mongering”! I am making statements about maneuvering and “MAX cruise speeds” (call it what you will but it is addressed by Mr Krueger as Vc) to make note of these speeds that are important to structural integrity not risks of stall. Both of those speed concepts exist so that pilots can be aware of structural limits of the airframe. That structural integrity is why VANS wrote the above referenced article! The speeds listed that fall outside the margins of the “cruise envelope “ referenced in that graph are not labeled “stall”. They are labeled “STRUCTURAL DAMAGE”. The graph refers to the upper limit of cruise speed as Vc. That is what I am referring to as “MAX Cruise Speed”. Anything above that up to Vne is putting the airframe outside the “safe” envelope the airframe was designed to operate in.

I too have had questions about IAS and TAS, since VANS does address Vne as TAS speed but labeled the graph as IAS. For my flying I use TAS for every speed except stall. It is my opinion that TAS is a more accurate measurement of the airplane’s actual speed moving through the air and therefore is a more realistic representation of what impact that atmosphere will have on the plane as it travels through that air. It is that atmospheric environment that will ultimately impact the airframe.

Live Long and Prosper!


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