Lift Reserve Indicator (LRI) Demonstration

[Rynoth]

The LRI is an on-again off-again topic that comes up occasionally, today I felt like making a little demonstration video of how it works in the cockpit.

https://youtu.be/7aVS91ogf1c

Video Description:

"This is a video demonstrating my Lift Reserve Indicator (LRI), which is basically a very simple/inexpensive setup that gives readout similar to an Angle of Attack (AOA) indicator. It uses 2 90-degree offset ports on a 3d-printed probe which is mounted on my left wing and set to the stall AOA, connecting to a simple differential pressure gauge. The resulting indication, once calibrated, will provide a visual indication of proximity to stall AOA, as well as how much of a buffer (reserve lift) is left between your current AOA and stall.

The demonstration shows how when the stall buffet occurs, the LRI is indicating the stall in the middle of the red arc (which happens to be where I've calibrated it), while the airspeed varies depending on how accelerated the stall is. Additionally, the landing video shows how the LRI is useful in controlling approach and touchdown airspeed. For all of these maneuvers the LRI was my primary instrument (including the landing.) Since the LRI is essentially AOA based, unlike airspeed, the readout is valid for any aircraft weight, pitch, or bank angle."

If anyone has any ideas for additional demonstrations/capabilities of LRI, let me know and I can do more testing/video. I believe is also has usefulness for setting best glide (again, at any weight), and possibly best angle of climb. I think it’s a fantastic instrument that’s also in the budget of a home builder.

[onex28]

Thanks for the video Ryan, good stuff. At what angle do you have the probe set relative to the bottom of the wing skin?

David

[Rynoth]

Thanks for the video Ryan, good stuff. At what angle do you have the probe set relative to the bottom of the wing skin?

David

It's installed at exactly the same position as the pitot tube position on the opposite wing. Angle to the bottom skin is set to 63 degrees (in flight testing I incrementally adjusted it starting from about 57 degrees, then to 60, then 63 was my sweet spot.) Making the adjustments was pretty straightforward, each time I increased the angle it moved the stall buffet a bit more towards/into the red on my instrument.

Correction: I actually just measured it and it’s 63 degrees, will post a pic later.

Edit: images of the probe:

[inventor]

That is a great video. Would you share where you picked up the instrument and the manufacturer? I have seen a few by searching but your gauge looks better than the ones that come up on a search.

Richard

[Rofomoto]

At what angles are the holes in the probe

[Rynoth]

That is a great video. Would you share where you picked up the instrument and the manufacturer? I have seen a few by searching but your gauge looks better than the ones that come up on a search.

Richard

Hi Richard, unfortunately the individual that made/sold mine is no longer selling them (website is offline.) It was Kelly at Value Engineering, I think a few others here have his probe, or have made their own. As for the gauge, I think it's a 2 1/4" differential pressure gauge that has had the face markings replaced with what you see.

It looks like ACS sells a similar setup: https://www.aircraftspruce.com/catalog/ ... onitor.php

My installation post can be found here: http://www.rynoth.com/wordpress/waiex/2 ... indicator/

Also, see Robbie's excellent writeup on LRI here: http://www.sonexfoundation.com/uploads/ ... icator.pdf

At what angles are the holes in the probe

On mine the holes are on opposite sides of the rectangle, so 90 degrees, but are each initially drilled at (I believe) 45 degrees into the wind.

[thomas]

Ryan,

Thanks for posting the video of your LRI in operation and for your assistance earlier in locating Kelly. The good news is that he is still printing probes and charged me only $50. His email is kelly@meiste.com. Classy guy and easy to work with. Below is a photo of one of Kelly's probes that I'm mounting on my left wing, exactly mirror to the pitot location on my right wing.

Paul

[sonex1374]

As for the gauge, I think it's a 2 1/4" differential pressure gauge that has had the face markings replaced with what you see.

This is the pressure gauge that you'll want to use.

https://www.globaltestsupply.com/produc ... FgQAvD_BwE

Jeff

[onex28]

Thanks Ryan, I’m at 60 degrees now but need a slight adjustment. Now off to find your angle finder.

David

[Rynoth]

Thanks Ryan, I’m at 60 degrees now but need a slight adjustment. Now off to find your angle finder.

David

At 60 degrees I imagine you are getting consistent indications, but the stall may be a bit above the red (assuming you have the same gauge/arc ranges as me.) Where you set the stall on the gauge is really up to you, some might say to put it at the top of the red, mine is in the middle of the red. My main reason for doing so was just to have a bit more information/range at the top of the green arc.