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Stall warning airspeed for XS Mono

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rparigoris

Joined: 24 Nov 2009
Posts: 780

Posted: Tue Mar 02, 2021 12:55 am Post subject: Stall warning airspeed for XS Mono

Hi Group



What is favorite indicated airspeed to set factory stall warn to alarm at?



Thx. Ron P.

davidjoyce(at)doctors.org
Guest

Posted: Tue Mar 02, 2021 5:22 am Post subject: Stall warning airspeed for XS Mono

Ron, I was brought up n 5kts above stall speed. David, GXSDJ 

  

 

On 2021-03-02 08:55, rparigoris wrote:  	  Quote: 	
		   --> Europa-List message posted by: "rparigoris" <rparigor(at)hotmail.com (rparigor(at)hotmail.com)>Hi GroupWhat is favorite indicated airspeed to set factory stall warn to alarm at?Thx. Ron P.Read this topic online here:http://forums.matronics.com/viewtopic.php?p=500834#500834http://forums.matronics.cosp;           - NEW arget="_blank" rel="noopener noreferrer">http://wiki.matronics.com<        - List Contribution Web Sit                         a href="http://www.matronics.com/contribution" target="_blank" rel="n========

brian.davies44(at)gmail.c
Guest

Posted: Tue Mar 02, 2021 6:02 am Post subject: Stall warning airspeed for XS Mono

CS-VLA requirements ( guideline for us folks) :

 

(c) The stall warning must begin at a speed exceeding the stalling speed by a margin of not less than 9,3 km/h (5 knots), but not more than 18,5 km/h (10 knots) and must continue until the stall occurs.

 

Regards

 

Brian Davies

 

From: owner-europa-list-server(at)matronics.com <owner-europa-list-server(at)matronics.com> On Behalf Of davidjoyce(at)doctors.org.uk

Sent: 02 March 2021 13:22

To: europa-list(at)matronics.com

Subject: Re: Stall warning airspeed for XS Mono

 

Ron, I was brought up n 5kts above stall speed. David, GXSDJ

 

 



On 2021-03-02 08:55, rparigoris wrote: 	  Quote: 	
		  

--> Europa-List message posted by: "rparigoris" <rparigor(at)hotmail.com (rparigor(at)hotmail.com)>



Hi Group



What is favorite indicated airspeed to set factory stall warn to alarm at?



Thx. Ron P.





Read this topic online here:



http://forums.matronics.com/viewtopic.php?p=500834#500834



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rparigoris

Joined: 24 Nov 2009
Posts: 780

Posted: Tue Mar 02, 2021 3:30 pm Post subject: Re: Stall warning airspeed for XS Mono

Thanks for replies. What is approx. indicated airspeed when flying light weight and also near gross? I understand all aircraft will be a little different. I'm in the middle of wiring and want to add a 2mm super bright red LED on our Winter airspeed gauge close to where the needle would be  about 5 knots above stall. Thx. Ron P.

Burrilla

Joined: 25 Apr 2015
Posts: 182

Posted: Tue Mar 02, 2021 4:06 pm Post subject: Stall warning airspeed for XS Mono

Do you expect the stall, flapless and with flaps, to be significant different to the POH? 



Alan



Sent from my iPhone



 	  Quote: 	
		   On 2 Mar 2021, at 23:33, rparigoris <rparigor(at)hotmail.com> wrote:

 

 ï»¿

 

 Thanks for replies. What is approx. indicated airspeed when flying light weight and also near gross? I understand all aircraft will be a little different. I'm in the middle of wiring and want to add a 2mm super bright red LED on our Winter airspeed gauge close to where the needle would be  about 5 knots above stall. Thx. Ron P.

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=500840#500840

budyerly@msn.com

Joined: 05 Oct 2019
Posts: 281
Location: Florida USA

Posted: Tue Mar 02, 2021 7:29 pm Post subject: Stall warning airspeed for XS Mono

Ron, 

The speed change is only a couple knots from 1300-1450 pounds.  Stall speed is 49 KIAS at 1370.  Once you calibrate your airspeed system simply set the horn/light during in flight testing.  See your POH.

Vstall is square root of Weight / (1/2 x rho x Cl x S)  rho or density is .00238, Cl is about 1.6-1.7 and S is 100-110 square feet.  Answer is in feet per second so do the conversion.

5 knots is the accepted lead airspeed for the various warning systems in the FARs unless the plane is a computer driven squirrel that needs stick shakers and trend indicators so they get exceptions.



I do the stall speed horn tests with flaps up and down to get the ideal speed for my client.  Some builders insist on pitot tubes that are not installed to be most accurate IAW manufacturers guidelines so calibration is necessary.

The Europa Pitot/static of course is placed properly and very accurate.  Instruments and pitot/static connections must be checked always prior to first flight in my opinion.  What is on the gauge on the initial flight is a trend instrument without testing and verification.

Stall strips reduce lift at the stall and the indicated airspeed of the stall stripped wing will be higher.  The actual stall should be only a couple knots above an unstripped wing and the buffet typically 5 knots higher than that.  I set the stall warning horn at the beginning of the burble if it is about 5 knots above stall.  Close enough.  Fine tune to desired.



A super bright LED will not be welcome at night.  A normal LED (1.5 to 2 volts)  and horn has worked well for years, especially a flashing light.



Don't over think it.  I do not set the stall warning on my initial test flight.  I fly my airspeed because my instrument guy checked my indicator and pitot/static system.  GPS ground speed is my backup initially.

If unable, put a suction on your altimeter to increase the altitude 1000 feet,  A/S should read 135 Knots and both should be steady for 30 seconds.  VSIs are designed to leak then should stabilize out so disconnect the VSI during this ground test.  If it fails this initial test, something is wrong, go fix it.



I've written before on this in more detail..



Best Regards,

Bud Yerly



--

rparigoris

Joined: 24 Nov 2009
Posts: 780

Posted: Wed Mar 03, 2021 11:23 pm Post subject: Re: Stall warning airspeed for XS Mono

Hi Bud Thanks for reply. Curious, if you were to set stall warning 5 knots above stall with flaps and gear down on a Mono XS, when approx. might you get warning above (perhaps below?) stall with gear and flaps up? Ron P.

budyerly@msn.com

Joined: 05 Oct 2019
Posts: 281
Location: Florida USA

Posted: Thu Mar 04, 2021 7:41 am Post subject: Stall warning airspeed for XS Mono

Ron,  

I’m home from more medical tests today so here goes. 

  

The pre-stall warning will be close gear up/down on the mono.  That is flap up/down also in a trigear.   Different, but close enough. 

  

Not to be disrespectful, but an easy reference is The Theory of Wing Sections and note how the pitch and stall angle change with a plane  flap.  Fowler flap references are less available as they are company proprietary data. 

  

Or for the hands-on guy, go get proficient in the C-172 and set the flaps to just shy of 30 and note how the stall indicator horn (using the same suction device for a stall warning flap up and down) behaves. 

The clean stall warning is remarkably close to the pre-stall warning at low flap angles between 0-30 at slow speed approaches to the  stall.  At 40 degrees there is less of a warning as speed bleeds rapidly, but there is still ample warning. 

  

Note:  Approach to stall testing is at a slow rate of 1 knot per second.   Rapid changes in AoA or rapid decrease of airspeed approaching the stall will affect different aircraft from plane to plane due to design differences and rigging as well as the stall indicators design.  Pilot control and technique also affect the stall.  We all are “ham fists” on initial flights in a new aircraft until we get proficient. 

  

I hope I don’t sound flippant,  but It is like one of my commanders quipped "you're measuring it with a micrometer, marking it with a crayon and then cutting it with an ax".  Obsessing with small details can make you miss the main point which is build the aircraft per the manual.  However, learning should never stop, and asking questions is good, but questioning the design can lead you, me and others into making changes and decisions that perhaps are not well thought out or even applicable.   

  

Build and rig the plane correctly IAW the manual, then set the add on stall indicators or devices of your choice like the book says  and then test.  Fly IAW the handbook at the speeds prescribed and the aircraft will return honest feedback.  Expand the flight envelope slowly.   Don’t get into the weeds on the detail of add on systems or try to redesign things unless you personally have calculated, and tested your change.  For instance:  The Europa POH is very good provided it is read and followed.  Don't just put stall strips on and paint over them and expect the pre-stall warning to be what you desire.  Tape them on, and test.  Take baby steps and test three mistakes high.  Then get close to the ground.  Use caution and a long runway to determine how these devices work near the runway pre-touchdown.  Then reposition and test again until the warning is acceptable to you.  Some add on stall strips, AoA indicators, speed warners, and lift reserve  indicators  and others find omitting the stall strips and such devices is perfectly fine for them and their style of flying.  The latter feel these warning horns and lights on a straight wing airplane are just annoying bells and whistles.  Amateur Experimental Aviation is a diverse group. (ATTENTION:  for the sensitive of feelings, please disregard the following comment.)   Frankly I was one of the latter but to sell the aircraft I am now adding these “bells and whistles” as the civilian market in used experimental aircraft seems to need these.  I am appalled that many of the second hand owners buy before they have even flown the aircraft and other than the prestart checklist, have no idea what’s in the POH or why.  If a wing drops in a stall they fear the stall or label the aircraft is a killer, rather than noting they failed to keep the ball centered i.e. coordinated flight into the stall.  (ATTENTION:  Resume reading for the sensitive pilot.) 

  

As far as stall speeds and loading, I hope to be more clear here to you personally.  Because many folks arbitrarily decided a higher gross weight was necessary using the super-factor built into the Europa design (because they didn’t control their empty weight), I didn’t load my plane beyond the 1370 gross in the test phase.  Hell my ID placard says 1300 still for the Classic, but the ops manuals (POH for my aircraft) have changed since Mod 52 and my MTOW change.  Although a 1450 GW increase was the rage here in the US 20 years ago, I completed my initial flight testing below 1370 after Mod 52.  I worked up to 1450 MTOW (max takeoff weight) and kept the CG well within the limits.  I personally disassembled my aircraft and inspected the aircraft lift points and attachments after each test session.  Same with my clients.   I do not land above 1370 pounds without a post flight inspection (over gross/hard landing checklist), as I did not drop test the aircraft to determine gear stresses at 1450 pounds.  I personally only use 1450 as a MTOW in smooth air and hard surfaced runways.  My CG range was modified after testing and my maximum G limits lowered proportionally also.  My Operations Limits in my aircrafts flight manual are written for my airplane and it is flown by those operational limits I have tested.  Abrupt flight maneuvers and turbulence were and are still avoided when flying operationally above 1370 lbs.  Although the Europa was built with a super-factor to allow for amateur building, it is still a kit aircraft, with hand molded components for the most part and there are variations we cannot predict.  What we know for everyone is: fly the plane IAW the manual and it will behave.  Redesigning or "stretching" the limits should be avoided for the novice builder.  Not all modifications attempted by others will work exactly the same on your aircraft.  There is always some tweaking.  I try to write up my testing evaluations or changes and provide my documentation and test results, but that doesn’t mean it is going to work for you.  Test and evaluate, then test some more.   (Frankly, that is all I ever seem to do rather than long enjoyable cross countries as many use their aircraft for.) 

  

Some governments around the world limit ANY change to the design or modification of any aircraft without government approval.  This may be nanny state to some, but it occurs here in the US also.  Case in point is the LSA market.  Even in the US the light sport ELSA is not really an experimental aircraft.  By regulation, its assembly cannot deviate from the factory built SLSA without approval from the manufacturer or by contacting the FAA inspector and changing its registration and airworthiness to EXPERIMENTAL EXHIBITION CLASS.  As many of these “ELSA kits” are a less than 51% kits, the builder cannot be issued a repairman’s certificate for these aircraft they have built, yet they are considered Experimental Amateur Built by the FAA but, are still ELSA kits and are relegated  to exhibition class.    It is a regulatory mess now as some DARs and FAA inspectors are ignorant of the actual wording in the regulation and intent.  Now that accident information is being evaluated closer, we shall see how it is handled or if it stays a vague regulatory mess. 

  

Probably clear as mud. 

  

Bud Yerly 

  

  

Best Regards, 

Bud Yerly 

  

--

rparigoris

Joined: 24 Nov 2009
Posts: 780

Posted: Sat Mar 06, 2021 1:57 pm Post subject: Re: Stall warning airspeed for XS Mono

Hi Bud

"Probably clear as mud."

More Understanding Definitely! Ron P.

budyerly@msn.com

Joined: 05 Oct 2019
Posts: 281
Location: Florida USA

Posted: Sat Mar 06, 2021 2:52 pm Post subject: Stall warning airspeed for XS Mono

I reread my anythysia recovery rant.  I'm hoping I didn't hurt any second owner feelings.



I should write a paper for myself on the flap vs clean leading edge pressure and angle of attack difference so I can write the program sketch, as my digital attempted digital stall system would benefit.  Then it would be a lead into the angle difference in clean vs flapped prestall warning using stall strips as well.  As you know some Pipers have two stall warner switches, one flapped and one clean.  That may be easier than working a fixed suction port with all the measuring and testing required to get a program to work

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