Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Vfe Va Vne AC 90-89A

Matronics Email Lists Forum Index -> Zenith-List

View previous topic :: View next topic

Author Message

ernieth(at)gmail.com
Guest

Posted: Wed Apr 09, 2008 5:52 pm Post subject: Vfe Va Vne AC 90-89A

Hi

the UK report on the pa-181

had an interest technical explantion what Va



I am using my phone and can't get to it easly



The short answer is I don't think it is tested value



E



On 4/9/08, Sabrina <chicago2paris(at)msn.com> wrote:

 	  Quote: 	
		   



 For those of you who have flown off your 40 hours, what are your values for

 Vfe, Va, Vne as listed in your POH?



 Did anyone actually apply swift full control inputs at 1320 pounds at ever

 increasing speeds approaching Va and record the G force values?



 Would the FAA have required detailed G force values at various air speeds

 and control inputs to prove Va for the prototype CAW and AMD S-LSAs?





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=175836#175836

- The Matronics Zenith-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?Zenith-List

pchapman(at)ionsys.com
Guest

Posted: Wed Apr 09, 2008 9:07 pm Post subject: Vfe Va Vne AC 90-89A

At 00:02 10-04-08, you wrote:



 	  Quote: 	
		  



I understand it is a calculated value. My question is, has anyone, 

tested it.   Since the rule of thumb is that a 4G aircraft's Va is 

2X its stall speed, if the CAW stalls at 26, Va would be 52 knots if 

it were 4G, since it is 6Gs, what is its calculated Va at 1320?


	


You'd only want to go as far as the limit load, which might be 4g 

here. (I haven't been following the discussions closely.)

The speed vs G relationship is just based on lift squaring with 

speed. So for 6g the stall speed would be up by root(6) = 2.45* the 

one g stall speed.



 	  Quote: 	
		  One would expect "full from neutral" deflections to equal 4Gs at 2X 

stall.  My question is, has anyone done it?


	


I'm not really up on my flight testing theory, but as far as I recall 

nobody tests for Va. Planes do get tested for Vne in flight.  I don't 

think testing a G-loading is all that common, although it may be 

done, such as for aerobatic aircraft or by pilots who just want to 

check their own homebuilt. That's usually left more for ground static 

tests, checking for no permenant set at limit load, and no complete 

failure at ultimate load.



For Va it would be awkward to test in flight. If everything isn't 

perfect, one could overstress the aircraft (past limit load). In any 

case one might get some nasty high G accelerated stalls going on when 

one hits the stall break. But as you wrote, one could start at low 

speeds and low loadings and work ones way up. Still, it sounds more 

like something to do only on an aerobatic aircraft, and keeping the 

tests below Va to avoid overstressing.



There need not be any particular relationship between elevator 

deflection and the Va stall point. The elevator angle available may 

be chosen for any number of reasons, including being able to raise 

the nose on a forward C of G landing, and just selecting a convenient 

number (eg, +/- 25 degrees). So who knows what the elevator angle 

will be at a high speed high G stall.



I think Va is normally just something calculated on a graph, rather 

than something flight tested. As long as one knows the limit load, 

and the 1g stall speed, Va can be calculated. (Of course as one 

learns, somewhat counterintuitively as a student pilot, Va goes down 

when the plane is loaded more lightly than gross.)



What is done in flight testing is to check the stick force per g (at 

some chosen speed or speeds, like Va). That'll give some idea how 

sensitive the aircraft feels and whether someone rough on the 

controls is likely to overstress the aircraft. An aerobatic aircraft 

can get away with a lower stick force per g as more g is needed 

before damaging things, and the pilot has to be able to access the 

higher g regime without too much stick pressure.



Some of the old CAFE flight test reports in Sport Aviation in the 

late 90s were good for all the stick force per g type of techy reporting.

(http://www.cafefoundation.org/v2/research_aprs.php)    E.g., at Va 

one RV-6A was getting to 2.5 g with 7 lbs force, compared to a C-152 

needing 27 lbs.



That's the best I can do for a quick late-at-night answer.

Peter Chapman

Toronto, ON           601 HDS  /  912  /  C-GZDC

- The Matronics Zenith-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?Zenith-List

grant.corriveau(at)TELUS.
Guest

Posted: Thu Apr 10, 2008 10:44 am Post subject: Vfe Va Vne AC 90-89A

I wonder if any of these (expensive) test programs required for  

certified aircraft are performed for amateur built?  After all, our  

aircraft do carry a big sticker (varies by country) that says to  

effect: "This Is Not A Certified Aircraft"



The manufacturer's reputation and track record is mostly what we have  

to go on when deciding which  Kit we buy and build.  Then of course  

the actual quality of the build will vary, and folks will (often)  

make their own non-certified, untested "improvements" ...



Worst of all, many pilots fly their Zodiacs as if the "Aerobatics  

Prohibited" admonition did not exist --  ("but it looks so sporty, it  

must be aerobatic!" not!).



BTW - Could someone please confirm or deny that this recent crash was  

an XL version?



Thanks.

- The Matronics Zenith-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?Zenith-List

randy(at)rjhebertassoc.co
Guest

Posted: Thu Apr 10, 2008 11:08 am Post subject: Vfe Va Vne AC 90-89A

Grant this is what FAA has



http://registry.faa.gov/aircraftinquiry/NNumSQL.asp?NNumbertxt=357DT&cmn

dfind.x=14&cmndfind.y=7 



DO NOT ARCHIVE

 

 

Randall J Hebert

CH701 Tails built starting Wings

 

--

- The Matronics Zenith-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?Zenith-List

bryanmmartin

Joined: 10 Jan 2006
Posts: 1018

Posted: Thu Apr 10, 2008 12:44 pm Post subject: Vfe Va Vne AC 90-89A

That 26 knot stall speed was listed as IAS and with full flaps. I 

suspect that the actual stall speed (CAS) is significantly higher than 

that and Va is stated for the no flaps configuration. The Zenith web 

site list the XL's stall speed as 44 knots CAS. The Czech built model 

should be about the same.



The information I got from Zenith was Va = 110 MPH, Vfe = 80 MPH and Vne 

= 180 Mph.



I have flight tested my airplane for Vne. I have also tested it to 4Gs 

at gross weight. I did not test full control deflection at Va. For one 

thing, just because you are flying below Va doesn't mean you can't break 

the airplane by applying full control deflection. It just means that the 

wing will stall before it can exceed the positive G flight load limit in 

in a wings level attitude. I.e. you can apply full back stick without 

tearing the wings off, but not necessarily full forward stick and not 

necessarily full back stick with a large roll input.



Sabrina wrote:

 	  Quote: 	
		   

 

 I understand it is a calculated value. My question is, has anyone, tested it.   Since the rule of thumb is that a 4G aircraft's Va is 2X its stall speed, if the CAW stalls at 26, Va would be 52 knots if it were 4G, since it is 6Gs, what is its calculated Va at 1320?

 

 One would think someone would have flown the airplane at 5 knots above stall, used "full from neutral" elevator deflection and recorded the G forces.   Then at 10 knots above stall, etc. upto at least 2X stall speed.   

 

 One would expect "full from neutral" deflections to equal 4Gs at 2X stall.  My question is, has anyone done it? 

 

 I am not talking about rudder or aileron deflections, just "full elevator deflections from neutral."  Flight 587 reminds us that flying below Va does not protect us from limit to limit vertical surface movement.

 


	




-- 

Bryan Martin

Zenith 601XL N61BM

Ram Subaru, Stratus redrive

Do Not Archive

- The Matronics Zenith-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?Zenith-List

_________________
--
Bryan Martin
N61BM, CH 601 XL, Stratus Subaru.
do not archive.

Display posts from previous:

	Matronics Email Lists Forum Index -> Zenith-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum