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  #1  
Old 05-10-2018, 03:53 PM
RV8JD's Avatar
RV8JD RV8JD is offline
 
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Posts: 915
Default RV-8/-8A and RV-7/-7A Maneuvering Speeds (Va)

Please see Post #12 in this thread.
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Carl N.
Arlington, WA (KAWO)
RV-8, 415 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 06-07-2018 at 03:39 PM.
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  #2  
Old 06-04-2018, 04:46 PM
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RV8JD RV8JD is offline
 
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Posts: 915
Default Accident Probe: Maneuvering Speed

Today, AvWeb published the article linked below. They used the in-flight breakup of an RV-7 (Hurricane, Utah in 2015) as an example for a discussion of Maneuvering Speed:

https://www.avweb.com/news/features/...-230922-1.html
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Carl N.
Arlington, WA (KAWO)
RV-8, 415 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 06-07-2018 at 03:40 PM.
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  #3  
Old 06-05-2018, 06:02 AM
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ronschreck ronschreck is offline
 
Join Date: Mar 2006
Location: Gold Hill Airpark (NC25), NC
Posts: 1,336
Default A suggestion...

Carl,

I'll not attempt to argue with your figures as I am no aeronautical engineer. However, if you think that Van's maneuvering speeds are incorrect I would hope that you will contact Dick VanG. We may all benefit from having both of you address this issue together. I am sending you Van's email via PM.
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Ron Schreck
IAC Director and National Judge
RV-8, "Miss Izzy", 2100+ RV Hours
Track Me *** Gold Hill Airpark (NC25)
VAF 2018 Donor
"He who demands everything that his aircraft can give him is a pilot; he that demands one iota more is a fool."
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  #4  
Old 06-05-2018, 02:59 PM
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RV8JD RV8JD is offline
 
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Default

Quote:
Originally Posted by ronschreck View Post
Carl,

I'll not attempt to argue with your figures as I am no aeronautical engineer. However, if you think that Van's maneuvering speeds are incorrect I would hope that you will contact Dick VanG. We may all benefit from having both of you address this issue together. I am sending you Van's email via PM.
Ron,

I received your PM with Dick's address. Thank you. I may contact him directly.

As I mentioned in the original Post, I did contact Van's Aircraft. In early April I sent a PM to Scott M. and Mitch L. regarding two issues, one being this RV-8/-7 Maneuvering Speed question. I received a reply from Scott saying that it will take some time to review the two issues I brought up.

I should note that after I posted originally, Mike Vaccaro (Vac) contacted me. It turns out that he found the same discrepancy I found in Va for the RV-8/-7 when he was putting together his excellent transition training manual.

Note that his Va plot and mine do differ between 1600 pounds and 1800 pounds because I purposely did not take into account any change in the Design Limit Load Factor between 1601 pounds and 1799 pounds, since that is not typically how Va is calculated for civilian aircraft. When Mike put his plot together, he made the assumption that the Design Limit Load Factor would change linearly between 6.0 to 4.4g, and included that in his calculation of Va.

Mike also included an estimated reduction in Va for rolling-g maneuvers (based on a 33% reduction in Limit Load Factor). In civilian flying, all we are told as pilots is to either not pull any g while rolling; or be careful and not pull too many g's, with no guidance as to how much is too much. Since this is not usually quantified in the civilian world, I thought that was an excellent addition to the Maneuvering Speed section of his manual.

(Mike, if I mischaracterized anything you told me, please don't hesitate to jump in.)
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Carl N.
Arlington, WA (KAWO)
RV-8, 415 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 06-07-2018 at 03:40 PM.
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  #5  
Old 06-05-2018, 06:27 PM
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Walt Walt is offline
 
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Location: Dallas/Ft Worth, TX
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Default

Wow, that quite a difference, I think I'll lower my Va to something less than the current 124 Kts (down to about 105) until this gets cleared up!
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Walt Aronow, Dallas, TX (52F) RV7A, IO360, C/S, 1500+hrs

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  #6  
Old 06-05-2018, 06:57 PM
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RV8JD RV8JD is offline
 
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Quote:
Originally Posted by Walt View Post
Wow, that quite a difference, I think I'll lower my Va to something less than the current 124 Kts (down to about 105) until this gets cleared up!
One note of clarification. Aircraft designers and manufacturers usually publish the highest Va if they only publish one number. And Va decreases as Gross Weight decreases.

For the RV-8/-8A and RV-7/-7A, Van's published one Va of 142 MPH.

For the RV-14/-14A, Van's published the Va at the Aerobatic GW as well as the Va at the Utility GW. Note that the RV-14s have relatively high Va's. That is due to the higher stall speeds that the RV-14s exhibit, compared to the RV-8s and -7s.
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Carl N.
Arlington, WA (KAWO)
RV-8, 415 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 06-07-2018 at 03:42 PM.
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  #7  
Old 06-05-2018, 07:43 PM
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Chino Tom Chino Tom is offline
 
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Location: Chino, CA
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Default

Based on the formulas above, it appears the RV-14 Va's are calculated
using the clean stall speed, Vs, not Vso as is the case with the -8/8a.
Regardless of aerobatic or utility load limit, which stall speed should
be used, Vs or Vso?
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Tom Prokop
Chino, CA
RV-8A,180/CS/Carb, AFS 4500 EFIS/EMS
RV-6, sold, 820 hrs of fun.
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  #8  
Old 06-05-2018, 08:40 PM
KatanaPilot KatanaPilot is offline
 
Join Date: Feb 2015
Location: Locust Grove, GA
Posts: 373
Default FAR 23.335 - Design Airspeeds

Clean stalling speed V sub s.

If the published stall speeds are flaps down and the calculations for maneuvering speed(s) by the OP are using those speeds, then I believe the Va speeds being calculated above are suspect.
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Krea Ellis

Locust Grove, GA
DA20-A1 Katana "Princess Amelia"
RV-7A Phase 2
RV-10 under construction

Last edited by KatanaPilot : 06-05-2018 at 08:58 PM. Reason: Added text
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  #9  
Old 06-05-2018, 09:50 PM
RV8JD's Avatar
RV8JD RV8JD is offline
 
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Quote:
Originally Posted by Chino Tom View Post
Based on the formulas above, it appears the RV-14 Va's are calculated
using the clean stall speed, Vs, not Vso as is the case with the -8/8a.
Regardless of aerobatic or utility load limit, which stall speed should
be used, Vs or Vso?
The flaps up stall speeds should be used. I used the stall speeds from this Van's webpage, assuming they were flaps up stall speeds for the two different weights listed. Since Van's did not specify the configuration, they could indeed be the flaps down stall speeds.
__________________
Carl N.
Arlington, WA (KAWO)
RV-8, 415 Tach Hours
(Pic 1),(Pic 2)
- Out with the Old, In with the New
(Pic)
RV-8, 1938 Tach Hours (Pic 1),(Pic 2) - Sold

Glasflügel Standard Libelle 201B, N564NS - Sold
Rolladen-Schneider LS1-f, N61MP - No longer owned

Last edited by RV8JD : 06-05-2018 at 09:55 PM.
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  #10  
Old 06-05-2018, 11:53 PM
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Chino Tom Chino Tom is offline
 
Join Date: Jun 2005
Location: Chino, CA
Posts: 707
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Quote:
Originally Posted by RV8JD View Post
The flaps up stall speeds should be used. I used the stall speeds from this Van's webpage, assuming they were flaps up stall speeds for the two different weights listed. Since Van's did not specify the configuration, they could indeed be the flaps down stall speeds.
In the case of the -8/8a it appears to me Van's used the gross weight approximate Vso of 58 mph and the Acro load limit to calculate the
Va of 142 mph. Not the clean stall speed (Vs approximate 64 mph)
and the utility load limit.

Regardless, your post has me recalculating the Va of my -8A. Thank you
for bringing this to our attention.
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Tom Prokop
Chino, CA
RV-8A,180/CS/Carb, AFS 4500 EFIS/EMS
RV-6, sold, 820 hrs of fun.
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