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LRI versus Stall warning

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larry(at)macsmachine.com
Guest

Posted: Wed Feb 28, 2007 10:53 am Post subject: LRI versus Stall warning

Hi guys,



I’ve been reading about the Lift Reserve Indicator and stall warning 

indicators and wondering how much

advantage there is to having a gage with the sensitivity of LRI range 

compared to a sound stall warning indicator

that provides only a preliminary warning in advance of a stall.



My panel is full and there’s little room for anything more than a string 

of small lights. The stall-warning indicator

seems to do the same thing for about the same effort. Any 

recommendations or opinions on these devices?



Larry McFarland – 601HDS at www.macsmachine.com

dredmoody(at)cox.net
Guest

Posted: Wed Feb 28, 2007 11:49 am Post subject: LRI versus Stall warning

Take a look at the AOA Sport system here:



http://www.advanced-control-systems.com/Products/AOA/aoa.html



This system doesn't take much panel space and gives an incremental display of your relative AOA which is better info than just a threshold warning alone. With the AFS systems, you can also pipe and audible threshold warning into your speaker or intercom system to make sure you don't ignore a critical LED display indication.



The upper and lower wing surface ports can easily be retrofit into removable access hatches if you have already rivetted the wing closed. Just make certain to use flush dimpled flat head screws to avoid significantly disturbing the airflow over the ports. The ports will need to be about 5 - 6 inches aft of the upper spar rivet line and about 2 - 3 inches aft of the lower one.



Dred

---- LarryMcFarland <larry(at)macsmachine.com> wrote: 

 	  Quote: 	
		   

 

 Hi guys,

 

 Iâ€™ve been reading about the Lift Reserve Indicator and stall warning 

 indicators and wondering how much

 advantage there is to having a gage with the sensitivity of LRI range 

 compared to a sound stall warning indicator

 that provides only a preliminary warning in advance of a stall.

 

 My panel is full and thereâ€™s little room for anything more than a string 

 of small lights. The stall-warning indicator

 seems to do the same thing for about the same effort. Any 

 recommendations or opinions on these devices?

 

 Larry McFarland â€“ 601HDS at www.macsmachine.com

craig(at)craigandjean.com
Guest

Posted: Wed Feb 28, 2007 1:22 pm Post subject: LRI versus Stall warning

Not cheap though. The Sport model is about $900 while the Pro model (which I

have) is almost $1500. The system is a better deal if (like Ed) you get it

built-in with the EFS glass panels.



I haven't installed mine and will be using the AOA built into the MGL Enigma

instead. But you can build the same flush-mount ports by buying flush static

port fittings from Spruce. The valve to drain the port on the top of the

wing is just a fuel tank testing valve. If your wing tips are still open

then the numbers from AFS indicate that installing the ports through the

tips will place the probes sufficiently far enough from the wing tips for an

accurate reading and at the correct spots on the chord.



-- Craig

p.mulwitz(at)worldnet.att
Guest

Posted: Wed Feb 28, 2007 2:30 pm Post subject: LRI versus Stall warning

Hi Larry,



It is my understanding that the LRI and related 

Angle of Attack instruments actually do a lot 

more for you than a stall warning device does.



All the stall warning device does is give you a 

warning that you may be near a stall.



AOA devices and the LRI actually help you to fly 

your plane near the stall without risk of 

actually stalling.  They work to let you approach 

the edge of your envelope no matter how your 

plane is loaded or what the weather conditions 

are.  Using one of these devices you can safely 

land and take off at minimum air speeds and 

achieve ultimate performance with regard to 

landing and takeoff distance as well as obstacle clearance.



I have never flown with one of these devices, but 

all the jet pilots swear by them.  I actually 

built an LRI and will install it on my panel before my first flight.



Good luck,



Paul

XL fuselage

At 10:52 AM 2/28/2007, you wrote:

 	  Quote: 	
		  



Hi guys,



I’ve been reading about the Lift Reserve 

Indicator and stall warning indicators and wondering how much

advantage there is to having a gage with the 

sensitivity of LRI range compared to a sound stall warning indicator

that provides only a preliminary warning in advance of a stall.



My panel is full and there’s little room for 

anything more than a string of small lights. The stall-warning indicator

seems to do the same thing for about the same 

effort. Any recommendations or opinions on these devices?



Larry McFarland  601HDS at www.macsmachine.com


	


--

n801bh(at)netzero.com
Guest

Posted: Wed Feb 28, 2007 3:58 pm Post subject: LRI versus Stall warning

I have been following this thread for a few years and I guess it is time for me to chime in on my thoughts. A plane flys because of the pressure differential between the top wing surface and the bottom wing surface. This differential is based on the airspeed, too slow and the wing cannot support the weight of the plane and down you go, increasing  airspeed and the air passing over the wing will create more lift and the plane stays in the air,  The airspeed indicator gives this information. Suppose you fly into a gust of wind that results in a tailwind componant during landing, The airspeed indicator will instantly show that. Ok, here is the scenerio, someone builds a wizbang 2000 kitplane, they install a airspeed indicator, a Lift Reserve Indicator and a Angle Of Attach indicator. They take off thinking they are bulletproof because of all the gizmos mounted in the panel. Now there are THREE things to look at during a landing event instead of one. They think they can land "safely" at minimum airspeeds and at the flying envelope. You fly into that gust of wind that's atailwind on short final and airspeed drops instantly. My question is,,, which gauge or indicator do you trust and bet your life on ?????? 

do not archive





rning that you may be near a stall.



AOA devices and the LRI actually help you to fly 

your plane near the stall without risk of 

actually stalling.  They work to let you approach 

the edge of your envelope no matter how your 

plane is loaded or what the weather conditions 

are.  Using one of these devices you can safely 

land and take off at minimum air speeds and 

achieve ultimate performance with regard to 

landing and takeoff distance as well as obstacle clearance.



I have never flown with one of these devices, but 

all the jet pilots swear by them.  I actually 

built an LRI and will install it on my panel before my first flight.



Good luck,



Paul

XL fuselage

At 10:52 AM 2/28/2007, you wrote:

 	  Quote: 	
		  --> Zenith-List message posted by: LarryMcFarland <larry(at)macsmachine.com>



Hi guys,



I’ve been reading about the Lift Reserve 

Indicator and stall warning indicators and wondering how much

advantage there is to having a gage with the 

sensitivity of LRI range compared to a sound stall warning indicator

that provides only a preliminary warning in advance of a stall.



My panel is full and there’s little room for 

anything more than a string of small lights. The stall-warning indicator

seems to do the same thing for about the same 

effort. Any recommendations or opinions on these devices?



Larry McFarland  601HDS at www.macsmachine.com


	


--&========================         - The Zeatronics List Features Navigator to browse

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Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Wed Feb 28, 2007 4:20 pm Post subject: Re: LRI versus Stall warning

I'd like to hear from someone out there who has first hand knowledge of the stall characteristics of the XL.  I suspect that it's stalls are gentle and give you plenty of warning, but would like to know if that is not the case.



Truthfully, I have never paid much attention to stall warning devices in my flying career.  In fact, the Champ I fly now has no such device and I don't miss it. 



One of the first things I do when checking out in a new aircraft is take it up and stall it at different attitudes and airspeeds. I also check out it's behavior in "slow flight" and other regimes of flight.  Back in the pattern I trim for an approach speed at around 1.3-1.4 times the stall speed in the landing configuration and go from there.  I suspect that the XL gives plenty of warning when approaching the stall and that once a person has familiarized themselves with the aircraft they should be able to avoid trouble quite easily.  The decision as to whether to install an AOA indicator, stall warning or the like depends on what you need to feel comfortable in the aircraft.



Tim

_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

dredmoody(at)cox.net
Guest

Posted: Wed Feb 28, 2007 4:41 pm Post subject: LRI versus Stall warning

I'm just a low time recreational pilot and I think  there are surely wiser and more experienced minds monitoring this list, so I'll  give this topic my best shot and those who know more can correct any errors or  oversights. 

  

 First, a lift reserve indicator (LRI) and an AOA  indicator are pretty much the same instrument with slightly different operating  details. I don't think many builders will install both in the same panel so  don't lose sleep about having to monitor both. If you are flying an approach or a climb out by reference to angle of  attack, you will be scanning both the ASI and the AOA using  the throttle and stick to keep the flight within a safe envelope. For  example, if the touchdown point is rising in the windshield, a little back  pressure slows the descent and a bit of additional throttle keeps the AOA pegged  where you want it.

  

 Third, I think (hope) what Paul mean to convey  was that using these instruments allows you to better determine what a safe  margin above stall speed actually is at any moment of flight. I don't think  it's a great idea to fly right on the edge of a stall at low altitude with or  without one of these gadgets. The advantage of an AOA indicator is that unlike a  stall warning horn it tells you accurately how close you are to the critical  angle at which your lift will abandon you. Since the speed at which  that happens can vary a lot with atmospheric conditions, loading, and the  general condition of the plane, the margin between the stall horn and the stall  can increase or decrease too. The AOA instrument gives you more and better  information.

  

 Now does this mean that stall horns are the agents  of the antichrist? Obviously not. Are you doomed if you don't install and use an  AOA or LRI instrument? Nope. Is it easier to fly safely using one of these  instruments? Yes it is.

  

 That's my story and I'm sticking to  it,

  

 Dred

 [quote]   ---

amyvega2005(at)earthlink.
Guest

Posted: Wed Feb 28, 2007 4:43 pm Post subject: LRI versus Stall warning

stalls in the 601 are yaaaawwwnn inducing,  0n slow flight you can get to full flaps, and trim for 50 knots, start pulling back and you think it will hang on the prop, then just when the speed gauge starts coming out of the green arch at around 40  knots,  a little shutter, you push the nose and your done.  the plane loses at most 200 ft.  Yaaawwwnn.   zzzzzzzzzzzz.

Juan



--

craig(at)craigandjean.com
Guest

Posted: Wed Feb 28, 2007 4:52 pm Post subject: LRI versus Stall warning

Well, I *think* the carrier pilots who have AOA indicators  just look at the AOA. But I think we have real carrier pilots on this list so  I'll hope for a an answer from them.

  

 -- Craig

  

 do not  archive



  

   [quote][b]

taffy0687(at)yahoo.com
Guest

Posted: Wed Feb 28, 2007 4:58 pm Post subject: LRI versus Stall warning

ground speed is affected, airspeed will read the same



 ---

larry(at)macsmachine.com
Guest

Posted: Wed Feb 28, 2007 5:33 pm Post subject: LRI versus Stall warning

You don't bet your life on either device. In normally good weather and a 

short strip either one of these would

seem to be capable of giving you an edge getting in short. I've already 

experienced a 100-foot drop in wind

shear some 5 years ago and had but 30-feet left on final. A sudden 

tailwind would be the same thing and you can't

insure against either event, but I was looking for a preferred mechanism 

and may have to design a

electrical multi-light LRI readout to get the job done.



Thanks,

Larry McFarland  601HDS at www.macsmachine.com

 	  Quote: 	
		  

 My question is,,, which gauge or indicator do you trust and bet your 

 life on ??????



 I have never flown with one of these devices, but

 all the jet pilots swear by them. I actually

 built an LRI and will install it on my panel before my first flight.



 Good luck,



 Paul

 XL fuselage



 >My panel is full and there’s little room for

 >anything more than a string of small lights. The stall-warning indicator

 >seems to do the same thing for about the same effort. Any 

 recommendations or opinions on these devices?

 >

 >Larry McFarland  601HDS at www.macsmachine.com

jhstarn(at)verizon.net
Guest

Posted: Wed Feb 28, 2007 5:46 pm Post subject: LRI versus Stall warning

Well I have to go with opinions of several Naval Aviators that land on  carriers, at night, pitching deck & howling winds...  They pick  AOA....We asked before installing AOA in HRII. Stall warnings are NOT graduated,  kinda like a low oil light. It blinks under braking when it's almost too late.  Three green, three yellow & four red tell you as you approach. doesn't wait  till your at the point of no return to do anything.  AOA, every scenario I  heard so far.  KABONG  Do Not Archive 

 [quote]   ---

p.mulwitz(at)worldnet.att
Guest

Posted: Wed Feb 28, 2007 6:29 pm Post subject: LRI versus Stall warning

Hi Larry,



If you would like to have the LED readout without having to design 

it, you might want to look at Elbie's AOA product.  His web page is: 

http://www.riteangle.com/index.htm



The AOA product gives you similar capabilities to the LRI.  I think 

they are the same, but Elbie assures me they are actually 

different.  Still, either one allows you to maintain whatever margin 

you want over stall speed.



For me, the big advantage of the LRI is you can build one for under 

$100.  That is a lot less than the purchase price of any of the 

completed products.

Paul

XL fuselage



At 05:31 PM 2/28/2007, you wrote:

 	  Quote: 	
		  I was looking for a preferred mechanism and may have to design a

electrical multi-light LRI readout to get the job done.


	


-

4rcsimmons(at)comcast.net
Guest

Posted: Thu Mar 01, 2007 8:44 am Post subject: LRI versus Stall warning

List,  

   

Just a comment about LRI’s, and AOA and all of the other gadgets that seem to be popping up to distract our eyes from out the window.  

   

I just read an article about looking out the window of an airplane. That is really how we learned to fly. The instruments were not second but conformation of what our seat was telling us. It can also be the direct opposite, the seat confirming what the instruments are saying. They go hand in hand (with caution).   

   

If you want it of course put it in but it was interesting enough that when I flew in the 601XL a few weeks ago, I realized that it had a pretty good LRI and AOA built into the plane itself. I think it was called wing shutter. It was evident and increased accordingly to the decrease in lift. I was impressed to say the least at the handling capabilities under 40mph. (Yes we were 2 mistakes high!) NO bad tendancies and this was experienced as well in the 801. The plane does not roll like a C152 in which I learned to fly in.  

   

I am not fussing but just commenting that for me I still want to use the “KISS” principal in the construction of what my plane. Of course, the wallet and developing technologies will also entice what it will turn out to be.  

   

Until I started reading the list (Under 100 hour pilot) I had never heard of either of these gadgets. As a recreational pilot, I am not sure but is the LRI and AOA necessary or just a nicety? Is it highly recommended by MFG of light aircraft or something to add to cause a distraction for the recreational pilot who looks out the window in most cases?  

   

Again, not a fuss but just a comment so I can better evaluate the need for the AOA or the LRI for my own knowledge!  

   

   

Thanks,  

Rich  

601XL  

   

Do not archive  

   

   

       [quote][b]

ter_turn(at)yahoo.com
Guest

Posted: Thu Mar 01, 2007 10:33 am Post subject: LRI versus Stall warning

Just to add more fuel to the fire, isn't the type of flying, short field, bush, etc. the determining factor in installing a LRI? 

  Most stall/spin accidents occur in the pattern when ones trying to correct a poor setup situation and uses extreme 

  control input to do so. Isn't it unlikely that during that type of impulse maneuver a person is going to be aware enough of

  the situation to be looking at another,  or any instruments for that matter?

   

  Terry Turnquist

  601XL-Plans

  St. Peters, MO 63376

   

   

   

  Rich <4rcsimmons(at)comcast.net> wrote:

  [quote]              List,<?xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

   

  Just a comment about  LRI’s, and AOA and all of the other gadgets that seem to be popping up to distract our eyes from out the window.

   

   

    

Again, not a fuss but just a comment so I can better evaluate the need for the AOA or the LRI for my own knowledge!

   

   

  Thanks,

  Rich

  601XL

   

  Do not archive

   

  Finding fabulous fares is fun.

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Tim Juhl

Joined: 21 Mar 2006
Posts: 488
Location: "Thumb" of Michigan

Posted: Thu Mar 01, 2007 10:45 am Post subject: Re: LRI versus Stall warning

This is not necessarily a comment about LRI's but on a problem that Rich touched on. One problem I've had to deal with when working with primary students (especially those who play MS Flight simulator or the like) is that they want to focus almost totally on the flight instruments.  A kid who can make a great 45Â° banked 360 on instruments totally loses it when the instruments are covered up! As a result I usually cover up the AI for the first few hours.  I also have them do some takeoffs and landings with the airspeed covered, a great confidence builder. 



Don't get me wrong, instruments offer great information, but they are not a replacement for developing basic pilot skills.  I like gizmos as much as the next guy but try not to be dependent upon them.  That said, I see nothing wrong in installing a LRI.... I just don't think I will.



Tim

_________________
______________
CFII
Champ L16A flying
Zodiac XL - Jabiru 3300A
Almost done! It'll fly in spring!

craig(at)craigandjean.com
Guest

Posted: Thu Mar 01, 2007 11:00 am Post subject: LRI versus Stall warning

About half the AOA/LRI devices I am familiar with produce  either an audible alarm or a voice alert ("angle angle push push"). Just  like a stall alarm you don't have to watch it to improve safety. But when you  can watch it you can improve your understanding of the performance envelope of  your plane in different configurations and situations.

  

 -- CraigFinding fabulous fares is fun.



   [quote][b]

jhstarn(at)verizon.net
Guest

Posted: Thu Mar 01, 2007 3:19 pm Post subject: LRI versus Stall warning

It was pointed out to me that I should have identified the "We" I referred  to in my post. The other half of "We" is my building partner: Retired USAF F-4  Wild Weasel Pilot Major Tom "Gummibear" Gummo. The AOA was calibrated in flight,  as installed. All the red lights were On at the point of a stall. We tested  in steep climbing turns, inverted etc. The lights are bright enough to see  without looking "inside" and there is never the problem of a scan delay was with  gages. Our unit has the option for audio warnings too but we don't use it.    KABONG  still Do Not Archive

 [quote]    

   Well I have to go with opinions of several Naval Aviators that land on    carriers, at night, pitching deck & howling winds...  They pick    AOA....We asked before installing AOA in HRII. Stall warnings are NOT    graduated, kinda like a low oil light. It blinks under braking when it's    almost too late. Three green, three yellow & four red tell you as you    approach. doesn't wait till your at the point of no return to do    anything.  AOA, every scenario I heard so far.  KABONG  Do Not    Archive 

    	  Quote: 	
		   	
[b]

ronlee

Joined: 25 Dec 2006
Posts: 141

Posted: Fri Mar 02, 2007 10:08 am Post subject: Re: LRI versus Stall warning

I fly a 701, 100 Hp. I have a steam gage (machanical) LRI. I have flown with it since the first hour of flight, so I feel I can speak with some authority about the usefullness of it. As others have said it does not just tell when a stall is near, but one can see all the way down the scale as lift reserve is diminishing right down to the actual stall. As we all know the stall does not always occur at the same airspeed, it depends on the load, outside temperature etc. If one wants to maintain a certaain degree of lift reserve on landing it can only be done with a LRI . This can't be done with an ASI as the stall speed changes depending on all of the above. 

Has my LRI been usefull, yes. One time my pitot was pluged by an insect that had laid eggs of some sort  way up in the pitot tube. I was about fifty feet in the air and noticed very little air speed on the ASI .By looking at the LRI I was assured that I had sufficent speed, lift to maintain a safe flight. When it came time to land I could be assured I had enough lift to do it safley and without excessive speed. All my landings are done by refering to the LRI. Would I be without one in a STOL airplane, no. I am told that near every plane in Alaska has a LRI.

_________________
Ron Lee
Tucson, Arizona

japhillipsga(at)aol.com
Guest

Posted: Fri Mar 02, 2007 1:43 pm Post subject: LRI versus Stall warning

I have an AOA LRI on my XL. I was making rocket landings because rudder control felt so good and because I could. The LRI allowed me to slow down and feel assured she would keep flying even low and slow. My landings have become somewhat dull benign affairs now and my passengers seldom cry out and beg for Help! as noticeably as they once did. So all in all, the LRI can be a useful tool. Best regards, Bill of Georgia

    

  

 --

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