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Using LRI

PostPosted: Sun Apr 05, 2015 6:52 pm
by User GDS
I rely on my LRI and made this video to show it in operation. It's a great instrument, especially if you do low level maneuvering and slow approaches to landing. I would definitely install one if I were building another plane.

I had a lot of fun making the video, had to build a camera mounting system in front of the panel. Sorry for all of the lawyer-ly language in the beginning, but the LRI has to be calibrated to indicate properly.

https://vimeo.com/124164105

Re: Using LRI

PostPosted: Sun Apr 05, 2015 9:58 pm
by SheepdogRD
Did you buy that unit, or build it yourself?

Re: Using LRI

PostPosted: Sun Apr 05, 2015 10:01 pm
by levyland
Excellent video Gary thanks for sharing

Re: Using LRI

PostPosted: Sun Apr 05, 2015 10:20 pm
by Allan
John,
I tried to get hold of that sometime ago (or one that looks the same as yours) and got no response from the site. I have had a differential pressure probe made up for plane already which will plug into the ports of my glass panel.
I really like the analog needle setup !
I have a full glass MGL panel and radios and to back all that up I have an analog skid ball and magnetic compass and your LRI would be all that's needed..........magic!
So, where did you get it?
Allan

Re: Using LRI

PostPosted: Mon Apr 06, 2015 2:51 am
by Allan

Re: Using LRI

PostPosted: Mon Apr 06, 2015 9:32 am
by SheepdogRD
Allan wrote:An interesting link. http://www.ch601.org/resources/aoa/aoa.htm

I've attached PDF versions of that material which may be easier to read.

LRI Instructions from Airsoob.pdf
(107.02 KiB) Downloaded 108 times

LRI probe.pdf
(15.91 KiB) Downloaded 111 times

Allan wrote: I have had a differential pressure probe made up for plane already which will plug into the ports of my glass panel.

The link you pointed out explains that, If you have the probe, all you need is the gauge specified (Dwyer Series 2-5002 Minihelic II Differential Pressure Gauge). I bought mine from an eBay vendor, ravenbooks, for less than $40 delivered. I've attached the factory product sheet on the gauge.

Dwyer 2-5000_iom.pdf
(73.31 KiB) Downloaded 83 times

You'll also need a printed face for the gauge. A sample is included in the first attachment.

Here are other links that may help: http://mountainflying.com/Pages/articles/alpha_systems_aoa.html and http://tincantimes.dcsol.com/LRI.html and http://home.hiwaay.net/~sbuc/legaleagleXL/lri.htm

I looked into making the probe as in the instructions, but I don't have drills long enough to make accurate holes that deep. There are many different probes pictured on the web, so I'm making a much-simplified one by replacing the suggested long aluminum block with 1/8" aluminum tube, similar to this one:

LRI Probe 2.jpg

Here are some other examples of simplified probes:

LRI Probe 3.jpg


LRI Probe 4.jpg

Re: Using LRI

PostPosted: Mon Apr 06, 2015 10:53 am
by User GDS
The LRI in the video is this one: http://www.liftreserve.com. I bought it from Just Aircraft when I ordered my kit, but I don't see it as an accessory on their website anymore.

The LRI is the only analog gauge in my panel, it's a good back up to the electronics. I didn't use it much in the first 50 hours, but when I started landing on short spots where the margin for error was low, I started to rely on it to keep me slow, but not too-slow.

The other analog gauge I want to add is a large slip and skid ball. I've got one, but haven't figured out a clean way to mount it on the panel yet.

Re: Using LRI

PostPosted: Mon Apr 06, 2015 12:36 pm
by moving2time
Wouldn't an AOA indicator give you similar data for keeping your aircraft safe at slow and low flight attitudes while flying at the edge of the envelope? I guess I need to study up on what the actual differences are between AOA and RLI. Sounds like the RLI requires the same set up and configuration as an AOA. Would the choice between the two be related to costs? Looks like parts of the RLI can be hand built wile the AOA is a fairly expensive piece of equipment to add to the panel. Joe b

Re: Using LRI

PostPosted: Mon Apr 06, 2015 1:02 pm
by User GDS
They are the same thing, the airplane's Lift Reserve is directly related to its Angle of Attack, if you go past critical angle of attack, you will run out of lift reserve. If there is a difference in price for the different units, it's probably just coincidence.

Dynon has a good write up on AOA on their website. http://www.dynonavionics.com/docs/D180_Feature_AOA.html I use a Dynon Skyview and could have installed their probe to get AOA displayed, but I wanted an analog instrument on my panel.

If you build your own probe like in the pictures posted by Sheepdog, make sure the angle is adjustable. To calibrate you have to do some stalls and then make small adjustments to the angle of the probe. It takes a few flights/adjustments before it indicates properly.

Re: Using LRI

PostPosted: Mon Apr 06, 2015 8:55 pm
by Allan
LRI and AoA measure the same info if using the SAME probe type. Some of these digital systems have an option that is not true differential probe info and essentially work only in "straight and level" - or at least that's my understanding. So read your documentation for what ever "glass panel" you have.
Bought a winter skid ball, easy to mount and see. Skid ball is different to AoA, I think both are important and neither provides both sorts of info,definitely complimentary though! If I had to choose, skid ball is first, AoA next.
Flying a balanced aeroplane (skid ball) tells you lots and for those contemplating low level start with the training. It's cheap (for what you get) and an incredibly worthwhile experience. Gauges are second to all this.
Will work on making a different digital AoA display to start with on the glass panel. The analog gauge is a bit big for my panel space, have to see what other options are out there........so, keep ideas links coming.
First job for me will be getting the plane flying, the test flying program done.........

Re: Using LRI

PostPosted: Tue Apr 14, 2015 4:24 am
by Dave Krall CFII SEL SES
In what ways can LRIs give inaccurate information?

Re: Using LRI

PostPosted: Tue Apr 14, 2015 11:07 am
by SheepdogRD
Dave Krall CFII SEL SES wrote:In what ways can LRIs give inaccurate information?

Three scenarios come to mind: (1) a poorly calibrated system, (2) a system with the probe bumped to the wrong angle, or (3)a system with a blocked intake port. Any of these could indicate inaccurately. In other words, the stall wouldn't be where you expect it on the gauge.

Re: Using LRI

PostPosted: Tue Apr 14, 2015 4:55 pm
by gkremers
Richard,

I have the Alpha Systems AOA on my Highlander and couldn't be happier.

Ultra.png
Ultra.png (46.24 KiB) Viewed 2840 times


I don't need to know the exact airspeed for approach, stall clean or dirty, best rate of climb, best angle of climb. Once the system is calibrated (correctly) you run several tests to determine which combination of LED lights indicate the above scenarios. I find the LED's are a much better visual clue than the airspeed indicator. Of course I use both but the LE'D's work well for me.

I think your stretching the reasons just a bit.

#1. Of course it needs to be set up correctly, just like anything else when you build a plane.
#2 The mast that comes with the Alpha system is rugged, you'd hurt whatever body part runs into the probe before knocking it out of alignment (ask me how I know :wink: )
#3. I guess this could happen just like a plugged pitot tube by a bug, only happened once in my 30 years of flying so far. That's why we have redundancy.

Of course everyone will have an opinion... I will install one in my next build for sure.

Gary
N325AB
Highlander #249

Re: Using LRI

PostPosted: Tue Apr 14, 2015 7:59 pm
by SheepdogRD
gkremers wrote:I think your stretching the reasons just a bit.

I agree... I did have to wrack my brain for answers to Dave's question. I think all those scenarios are unlikely, and I should have made that clearer.

I've read dozens of favorable comments about AOA/LRI systems, and we'll have one in N7340Z.

Re: Using LRI

PostPosted: Tue Apr 14, 2015 9:16 pm
by User GDS
I don't know for sure, but I suppose that just like the ASI, it might read incorrectly in a slip. slip/skid makes turbulent air at the front of the pitot tubes. (I slip a lot on approaches, but only use LRI or AS at entry and exit of the maneuver)

Unfortunately, to test the hypothesis, I would have to slip and stall the plane, which I'm reluctant to do. I'm comfortable spinning a Citabria or similar, but don't have the nerve to play test pilot and spin the H.