Lift Reserve Indicator

[eightyknots]

LiFt ReSeRvE InDiCaToR

 

I have been looking around the internet about this interesting instrument. Most of what I have read is either positive or very positive. EG: Installing the Lift Reserve Indicator

 

As a newbie to flying, I would like to know what other pilots' experiences are (obviously for those who have an LRI), both advantages and disadvantages.

 

According to the introduction in the Wikipedia article: "The Lift Reserve Indicator (LRI) has been proposed as an alternative or backup to the Airspeed Indicator (ASI) during critical stages of flight. This is an elegant device but is rarely found in light aircraft or even transport jets."

 

Wikipedia concludes with: "The LRI has been well received by STOL pilots and pilots of experimental or home-built aircraft. The LRI is very useful for short field landings, short field takeoffs, and slow speed maneuvers such as steep turns, steep climbs, and steep descents, and also allows pilots of fast or "slippery" aircraft to land with little or no float very reliably. Since the LRI is so useful at the critical lower end of the flight envelope, most pilots will use the LRI as a complement to the ASI, using the LRI for slow speed work and the ASI for cruising and navigational work."

 

I wonder, if this instrument has the potential to save lives, why are so few fitted to aircraft? Is it cost cutting, complexity or the weight?

 

 

[eightyknots]

Associate Professor installs LRI in personal plane

 

The Embry-Riddle Aeronautical University did a report on the LRI (see http://www.liftreserve.com/erau.htm). Interestingly, the Associate Professor (Richard E Neate) involved in this liked it so much that he installed one in his personal Piper Cherokee 140 even though he wrote: I don't completely understand the LRI, I like the system and I even trust it enough to use it as the primary traffic pattern indicator.

 

It is a riddle to me that an instrument that is so neat seems to be seldom installed in planes.

 

 

[dazza 38]

What is it.Is it like a AOA indicator.I have never heared of it before? I havent voted as yet.I dont know what it is ?

 

 

[Spin]

Yeah Dazza, sounds a bit like a simplified AoA indicator that I read about a while back. This one used a pressure sensitive pad on one leading edge, connected to a series of lights displayed in the cockpit, essentially showing how close you were to the stall.

 

The way it was described there sounded pretty interesting - I just get a bit edgy about things sold like snake oil, ie. "I can't explain how it works, but trust me, I'm a doctor/engineer/pharmacist, it does and you are an idiot if you don't buy one too"

 

 

[dazza 38]

Yeah Dazza, sounds a bit like a simplified AoA indicator that I read about a while back. This one used a pressure sensitive pad on one leading edge, connected to a series of lights displayed in the cockpit, essentially showing how close you were to the stall. The way it was described there sounded pretty interesting - I just get a bit edgy about things sold like snake oil, ie. "I can't explain how it works, but trust me, I'm a doctor/engineer/pharmacist, it does and you are an idiot if you don't buy one too"

Thanks Spin.:)

 

 

[KB59]

Talk to any pilot that has dropped onto a Navy Carrier over the last 50 odd years.

 

They work

 

 

[Spin]

Talk to any pilot that has dropped onto a Navy Carrier over the last 50 odd years.They work

Very true, I believe they improved the success rate of new pilots qualifying, quite dramatically when first introduced. I understand airliners rely quite heavily on AoA indications as well in the landing / t-off configuration.

 

What I was getting at, was the implication that this is something new and not fully understood. I like the idea, especially for STOL operations, where airspeed is but a crude approximation of what you really need to know.

 

 

[jetboy]

I tried one, useless in CH701, Easy to build but just not meaningful enough (things unravel fast in a 701, no time to watch what the clocks are doing) I could install it again but it is a waste of panel space

 

Ralph

 

seeing your poll has got ages to run I reserve my decision

 

 

[icebob]

Must agree with Spin a great bit of kit, they can be set for instrument only display or a set of tones or voice. You can get exactly the same rate of decent +/- 20fpm all the time, the more expensive ones have better accuracy.

 

Bob.

 

 

[facthunter]

Lift reserve indicator..

 

Works on a principle of measuring AofAttack. Jets have had this as a slow-fast indication for years. It gives a confirmation that the speeds you are using are safe. Takes configuration etc into account.( flap settings etc ). While I like the information I am not sure of it's relevance to our ops. Things change pretty quick sometimes, so "feel" for your plane might be more appropriate. If you get a high sink rate suddenly you don't always have the time to look at instruments. Nev

 

 

[Thalass]

Seems ok, to me. Airliners use AoA and Airspeed to vary the point at which the stick shakers start up. I don't think the ones i work on have an actual indication - Airline pilots fly to set figures in a book rather than their pants so they don't really need to know their AoA. As long as they fly the numbers they'll be fine.

 

Of course i've only worked on a few aircraft types, so i'm sure there are others out there that do.

 

I kind of like this thing. I would probably prefer a proper electronic indicator with AoA and Airspeed inputs, but i'm avionics and airline so i'm weird like that. It seems it measures the differential pressure between the two holes on the probe. During cruise the forward one will see nearly 100% pitot and the downward one would almost be a static port. As you get slower the pitot pressure on the forward one decreases, and as your AoA increases the pressure on the downward one would get higher. So i guess it's a reconfigured airspeed indicator. Kinda neat.

 

It probably shouldn't replace a pilot knowing his/her aircraft. They do tell you when they don't want to fly anymore. But everything helps!

 

 

[Smokey]

Easy to build but just not meaningful enough

Hi Ralph

 

A while back I was hunting up how to build an AOA indicator, not sure I'd actually build one, curiosity as much as anything. Couldn't find anything on the net at the time. Came up with a few ideas of my own, vane with optical sensors, 2 ports above and below the LE with some sort of electronic pressure sensor(s) to give the differential etc.

 

Do you have any specifics or references on how to build/calibrate ?

 

Ta Mark

 

 

[Deskpilot]

Hmmm, wouldn't have one in your normal plane but I just might consider one in my Eagle-ray due to the high AoA on landing. That is, if I ever get round to finishing the design and start building.

 

 

[antzx6r]

From what I read of pilots moving up to slipery higher stall speed aircraft, the biggest danger is alowing the aoa to get too high when lining up on final or turning xwind on T/O or just when bad weather closes in trying to find the field. So I think for those looking at aircraft like the Lancair, this could be the instrument that saves lives. However with the 45kn stall restriction on raa, I think this instrument would be helpfull in getting nice flat approaches but if you are slow enough to get a warning from this instrument, your almost falling out of the sky. I could be wrong tho. I've never seen them working.

 

 

[hihosland]

have a look at

 

INSTALLATION

 

for an ecconomical option

 

davidh

 

 

[facthunter]

Flying with an AoA indicator.

 

They are a great bit of kit. The aircraft that I have done most of my flying in have them and they are essential in that environment.

 

Speeds are NOT a good indicator of whether you are stalling ,or near the stall . The AoA IS and IF you were trained appropriately you would fly much better and safely using it. If the aircraft is flapped, then the system whether a vane or a 2 port would have to recognise the change of configuration, and be calibrated in both. If the thing is not set up properly then it is just a distraction.

 

Don't forget that the stall "speed" varies in response to "G" loading, weight, flap setting. IF you had an AoA indication in a steep turn, with flap and full power you could fly the altimeter and tha AoA indicator only and do the safest Max rate level turn your plane is capable of. Nev

 

 

[eightyknots]

LRI claims, gleaned from liftreserve.com

 

100% Stall Protection

 

Instantaneous Windshear Detection and Best Recovery Solution

 

Automatic Density Altitude Compensation

 

Maximum Lift Performance

 

Shortest Takeoff Roll

 

Slowest Flyable and Maneuvering Speeds

 

Slowest Approach and Landing Speed

 

Shortest Landing Roll

 

Minimum Sink

 

Correct Speeds for Varying Weights

 

Fly With Confidence and Eliminate Guesswork

 

 

 

 

 

 

 

 

 

 

 

Precision Flying in All Conditions

 

 

 

 

 

 

We have pilots come up to us all the time and say, "Oh the LRI is just a stall warner. I already have one on my airplane. What do I need an LRI for?"

 

The LRI is far more than a stall warner.

 

The LRI has been called an angle of attack instrument. It may be. The discussion is still open on this. The LRI does identify the absolute stall angle for any aircraft.

 

What makes the Lift Reserve Indicator unique is that the LRI integrates angle of attack and airspeed in a single, immediately clear analog readout.

 

Angle of attack and airspeed are the two fundamental components of lift. The LRI provides a continuous and steady visual display of the condition of an aircraft's lift throughout its slow speed envelope regardless of the many variables which act upon an aircraft.The LRI also provides a continuous visual reference of an aircraft's margin over stall at any airspeed. This allows a pilot to continuously track his aircraft's performance since the LRI responds instantaneously to pilot control and wind conditions.

 

What advantage does this give to a pilot?

 

The LRI is a potentially life saving instrument by keeping him aware of his margin over stall thus increasing precision and confidence for all pilots regardless of number of hours flown and level of skill.

 

The Lift Reserve Indicator is an investment in performance, safety and economy. The LRI needs only to be scanned once in a tricky situation for its significance to become immediately obvious to anyone flying with it on board.

 

The LRI is a user friendly instrument which quickly becomes part of a pilot's standard instrument scan. It a backs up instrumentation should they ever fail due to loss of electrical power or bugging of the pitot.

 

The LRI is inexpensive, easy to install and simple to calibrate and will pay for itself through fuel economy, savings on brake and tire wear and through the increased confidence and peace of mind that precision flying brings to all flying experiences.

 

As you can see, the above claims are pretty extensive.

 

 

[eightyknots]

BS = Before Stall?

 

..sounds like BS to me...

BS = Before Stall?

 

It may prevent stalls from occurring due to pilots knowing how much reserve lift they have. However, I still wonder why there aren't more fitted to aeroplanes.

 

 

[dazza 38]

I dont know it sounds like crap to me.Its not needed in the aircraft we fly.

 

 

[facthunter]

BS or not.

 

it would be significamt to note that nobody so far has ticked #2. Which is essentially that you HAVE used one and think they are a gimmick. Nev

 

Well now someone has,(as of the 30th) Isn't that surprising?

 

 

[jetboy]

Not to say they are a gimmick but thats the only category you left for me to apply;

 

In summary, and having used one, I cannot think of an RaAus type plane suitable to use them on, especially STOL style with slats/VGs.

 

The reasons I guess for ineffectiveness:

 

No indication compensation for different weights carried

 

No indication compensation for amount of flap deployed

 

In the context of the type of planes we fly, I think it does not adequately address the relationships of low inertia vs. airspeed and power settings, in gusty conditions where outcomes change quickly.

 

Dont be put off by my opinion, it costs so little to try one the plans are readily on the net and the indicator gauge is an off the shelf HVAC device, and calibration is easy to do.

 

Ralph

 

 

[facthunter]

Using the LRI.

 

What a horrible name. Lift reserve indicator. Wing performance monitor might be better but that's only off the cuff.

 

Thanks for your reply Ralph. An AoA indicator DOES compensate for weight change and for "G". That is why it's so good. When I flew gliders (briefly) I concentrated on the VSI. Having an AoA reading would help to get the max efficiency from the glider as well as a margin of safety from the stall in tight thermals.

 

A GOOD system will take flap and LED's (droops) if fitted into account.

 

I DON'T belong to a group that wants to watch instruments all the time, but this is a bit of information that would be more valuable than a lot of other stuff that clutters some cockpits. Nev

 

 

[eightyknots]

What a horrible name. Lift reserve indicator. Wing performance monitor might be better but that's only off the cuff.

It seems as if the Lift Reserve Indicator is also known as a POWL (Potential Of Wing Lift) meter. Does that sound any better?

 

 

[eightyknots]

Thanks for your response to this questionnaire and also the insightful comments!

 

My own feeling is that I wouldn't rule it out when I get around to building my aircraft.

 

 

[farri]

While I like the information I am not sure of it's relevance to our ops. Things change pretty quick sometimes, so "feel" for your plane might be more appropriate. Those who have an awareness and feel for what the AC is doing,have the best instrument of all.

 

Frank.