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MHerder
Joined: 11 Feb 2008
Posts: 143
Location: Fort Worth TX
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 Posted: Tue Feb 08, 2011 6:30 pm Post subject: Determining Vx |
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So Vy and best glide are easy to find, and I'm guessing that Vx is about 85% of Vy under "normal" conditions, although Vx=Vy at service ceiling.
How does one determine Vx? Any thoughts. Seems to be about 67kts for my bird, so Im guessing Vy is about 57 kts, I'd just like to know how it's determined.
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_________________
Zodiac 601 HD
Jabiru 3300
Wood Sensinich 64x47
Finally Flying |
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jlatimer1(at)cox.net
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| Posted: Tue Feb 08, 2011 7:15 pm Post subject: Determining Vx |
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Mike,
I will take a stab at it. I've been searching for the source of the information, but haven't found it.
When doing your rate of climb flight testing (ROC), you end up with the ROC for various airspeeds. These should be put into a spreadsheet and graphed, plotting ROC on the Y-axis and airspeed on the X-axis. Ideally you should get a parabola. The Vy corresponds with the max ROC of the parobola.
Vx is determined by extending a line from origin of the graph (0 ROC and 0 AS) so that it is tangent to the parabola. This is usually pretty close to Vy.
I also have a 601HDS with a 912S. My Vy was 70mph true airspeed and Vx was 65 mph TAS. This was at 3500 ft on a 95 degree day. I haven't rerun the test since it has been cold.
Jerry
N316JL, 70 hours
---- MHerder <michaelherder(at)beckgroup.com> wrote:
[quote] --> Zenith601-List message posted by: "MHerder" <michaelherder(at)beckgroup.com>
So Vy and best glide are easy to find, and I'm guessing that Vx is about 85% of Vy under "normal" conditions, although Vx=Vy at service ceiling.
How does one determine Vx? Any thoughts. Seems to be about 67kts for my bird, so Im guessing Vy is about 57 kts, I'd just like to know how it's determined.
--------
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Terry Phillips
Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT
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| Posted: Tue Feb 08, 2011 8:15 pm Post subject: Determining Vx |
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Mike
One of the books on my wish list a couple of years ago was "Flight Testing
Homebuilt Aircraft," by Vaughan Askue. My daughter and son-in-law gave me
the book for Christmas.
I haven't looked at that book much, because my build was interrupted and
flight testing is far away. Askue has a detailed procedure for determining
best ROC (Vy) as a function of altitude. It looks like a well thought out
approach.
And, my favorite flight training book, Machado's "Private Pilot Handbook,"
in chapter 15, suggests a procedure for determining the best angle of climb
speed (Vx) from the ROC curves that result from Askue's procedure.
You might take a look at those two books. Good luck with your flight testing.
Terry
At 06:30 PM 2/8/2011 -0800, you wrote:
| Quote: | So Vy and best glide are easy to find, and I'm guessing that Vx is about
85% of Vy under "normal" conditions, although Vx=Vy at service ceiling.
How does one determine Vx? Any thoughts. Seems to be about 67kts for my
bird, so Im guessing Vy is about 57 kts, I'd just like to know how it's
determined.
--------
One Rivet at a Time!
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Terry Phillips
ttp44~at~rkymtn.net
Corvallis MT
ZU-601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail & flaps are done;
Upgrading wings & ailerons per the AMD Safety Directive
http://www.mykitlog.com/N47TP/
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_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings. |
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ch701builder(at)yahoo.com
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| Posted: Tue Feb 08, 2011 8:52 pm Post subject: Determining Vx |
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Look at the attached file and see if this is what you are looking for. Found it on the EAA.org homebuilders site.
Keith
CH701 - scratch (working on cabin area)
From: MHerder <michaelherder(at)beckgroup.com>
To: zenith601-list(at)matronics.com
Sent: Tue, February 8, 2011 7:30:47 PM
Subject: Determining Vx
The fish are biting.
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Climb_Test_Procedures.pdf |
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Terry Phillips
Joined: 11 Jan 2006
Posts: 346
Location: Corvallis, MT
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| Posted: Tue Feb 08, 2011 10:37 pm Post subject: Determining Vx |
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Good find, Keith
That article only addresses determining Vy. However, it is 1 of a series of about 5 articles. One of the other articles describes the Vx calculation. Kolano appears to confirm Askue's procedure and the Vx determination suggested by Machado.
Terry
At 08:50 PM 2/8/2011 -0800, you wrote:
| Quote: | Look at the attached file and see if this is what you are looking for. Found it on the EAA.org homebuilders site.
Keith
CH701 - scratch (working on cabin area)
From: MHerder <michaelherder(at)beckgroup.com>
To: zenith601-list(at)matronics.com
Sent: Tue, February 8, 2011 7:30:47 PM
Subject: Determining Vx
The fish are biting. |
Terry Phillips
ttp44~at~rkymtn.net
Corvallis MT
ZU-601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail & flaps are done;
Upgrading wings & ailerons per the AMD Safety Directive
http://www.mykitlog.com/N47TP/ [quote][b]
| | - The Matronics Zenith601-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?Zenith601-List |
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_________________
Terry Phillips
Corvallis, MT
ttp44<at>rkymtn.net
Zenith 601XL/Jab 3300 slow build kit - Tail feathers done; working on the wings. |
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don.honabach(at)pcperfect
Guest
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| Posted: Tue Feb 08, 2011 10:53 pm Post subject: Determining Vx |
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If you have a RV builder nearby, there is a nice section in their builder’s manual (?) that they get that talks about Vx/Vy and how to get the numbers during your test flights.
Don
From: owner-zenith601-list-server(at)matronics.com [mailto:owner-zenith601-list-server(at)matronics.com] On Behalf Of Terry Phillips
Sent: Tuesday, February 08, 2011 11:31 PM
To: zenith601-list(at)matronics.com
Subject: Re: Determining Vx
Good find, Keith
That article only addresses determining Vy. However, it is 1 of a series of about 5 articles. One of the other articles describes the Vx calculation. Kolano appears to confirm Askue's procedure and the Vx determination suggested by Machado.
Terry
At 08:50 PM 2/8/2011 -0800, you wrote:
Look at the attached file and see if this is what you are looking for. Found it on the EAA.org homebuilders site.
Keith
CH701 - scratch (working on cabin area)
From: MHerder <michaelherder(at)beckgroup.com (michaelherder(at)beckgroup.com)>
To: zenith601-list(at)matronics.com (zenith601-list(at)matronics.com)
Sent: Tue, February 8, 2011 7:30:47 PM
Subject: Determining Vx
The fish are biting.
Terry Phillips
ttp44~at~rkymtn.net
Corvallis MT
ZU-601XL/Jab 3300 s .. l .. o .. o .. w build kit - Tail & flaps are done;
Upgrading wings & ailerons per the AMD Safety Directive
http://www.mykitlog.com/N47TP/ | Quote: | | <=====rowse, Chat, FAQ,[/b]http://www.matronics.com/Navigator?Zenith601-Listhttp://forums.matronics.com<================== <===== |
012
[quote][b]
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