Flying the Dynon AOA with the LRI AOA probe

[Sam Buchanan]

Finally got around to trying something that had been on the to-do list for awhile. My RV-6 panel includes both a Dynon D10A and an LRI angle of attack indicator:



The LRI is a valued instrument that I use on every flight:

http://thervjournal.com/liftreserve.htm

Not only does it provide the info needed for max performance take-offs and landings, but the LRI is the backup instrument for landing in case the Dynon takes the day off.

The Dynon includes an AOA indicator that was designed for use with the Dynon AOA pitot probe. Even though the D10A AOA indicator is smaller than the LRI indicator, it does provide an audible alarm, something that many have mentioned as a shortcoming of the LRI.

Question for the day-----Will the Dynon AOA indicator work with the LRI probe?

Short answer........Yes!

This should be of great interest to folks flying the LRI and a Dynon. It is possible to retain the independent, non-electrical function of the LRI, and have an audible alarm without having to install the Dynon pitot mast. This also puts an AOA indicator in your EFIS instrument scan.

I inserted a tee in the low-pressure line of the LRI (the one that connects in the center of the gauge) and ran a hose to the AOA port of the Dynon. The LRI probe was not touched so calibration of the LRI was not disturbed. The question I needed to resolve was whether or not the Dynon had enough calibration range to accept the LRI low-pressure signal in a way that provided useful info on the Dynon AOA indicator. Instead of going through the entire set of stalls per the Dynon instructions, I did one flaps-up, power-off stall that corresponds to the red/white indicator on the LRI. My goal was to try to have the two AOA systems showing "matching" warnings that I was already accustomed to.

The Dynon calibration routine worked flawlessly. Some repeat stalls demonstrated the stability of the calibration, and several touch-n-goes also confirmed the Dynon/LRI combo was behaving in a similar manner to the LRI indicator. I am still very early in exploring the Dynon/LRI combo, but it appears this is a very attractive option for those of us with both systems. Since this is such an easy mod to perform, I encourage others who have these systems to try this and let us know how it works for you.

After pondering this for about, oh, five minutes, me thinks it might be a very simple project to build an AOA probe that would work with the Dynon. It would involve a second probe for those who aren't using the Dynon pitot probe, but could be fabricated from an extra Vans aluminum tubing pitot probe (or the home-made equivalent). An aluminum plug with a 1/16" diameter hole would be in the outboard end of the tube, and the lower end would be bent down/forward at a 45 degree angle instead of the customary 90 degrees. This would mimic quite closely the design of the low-pressure side of the LRI probe. Obviously some flight testing would be needed, possibly to adjust the probe angle, but basically the system is driven by ram pressure that increases as angle of attack increases. Hopefully the Dynon firmware would be able to accommodate the low pressure signals generated by the custom-built (!) probe.

[davidcyr2000]

Interesting that the Dynon AOA works with the LRI AOA probe. What about the opposite situation? We have a Dynon Pitot/AoA probe and wonder if the LRI indicator would behave correctly with the Dynon probe...

[Bill_H]

Go to this thread then start on page 2. http://www.vansairforce.com/communit...ad.php?t=34040
You do not need the Dynon combo probe at all! You can add AOA to a Dynon for about $12 in plastic parts. The post shows an inflation needle as the port, but later it is shown that a simple "static port rivet" works just as well. On an RV-12 you can install the whole thing through the access plate for the stall switch. the key is putting it in the right place on the underside of the leading edge. I have it on my RV12 and it works great! Detailed parts list later in the post listed.

[Sam Buchanan]

Originally Posted by davidcyr2000

Interesting that the Dynon AOA works with the LRI AOA probe. What about the opposite situation? We have a Dynon Pitot/AoA probe and wonder if the LRI indicator would behave correctly with the Dynon probe...

David, I've never tried your combination but it should work to some degree. A problem I see is that the Dynon probe is not adjustable because calibration is calculated in the Dynon EFIS. The LRI depends on the probe angle being adjusted in order to get the expected indications on the dial indicator.

So the Dynon probe will most likely move the needle in the LRI indicator, but you may have to rework or remark the dial face once you find out where stall occurs.

[acent05]

I have an LRI with probe and would like to know if this will act as pitot and AOA for my GRT HXr. I believe it will work for the AOA so would it not work for pitot as well? Any advice appreciated.

[Raymo]

Originally Posted by acent05

I have an LRI with probe and would like to know if this will act as pitot and AOA for my GRT HXr. I believe it will work for the AOA so would it not work for pitot as well? Any advice appreciated.

From what I have read on the unit, the LRI only provides AOA from their probe. You would need a separate pitot tube for airspeed.

I am helping install the probe and associated wiring in a ADI Super Stallion, which has both probes. The owner contacted LRI for the heating element for the AOA probe (optional) so both are also heated.

[Sam Buchanan]

It would be interesting to try using the high pressure port on the LRI probe for pitot sensing. I suspect it would work, but I've never tried it. The high pressure port points straight into the slipstream at cruise.

[Canadian_JOY]

Originally Posted by acent05

I have an LRI with probe and would like to know if this will act as pitot and AOA for my GRT HXr. I believe it will work for the AOA so would it not work for pitot as well? Any advice appreciated.

There's a big "That depends..." part to this answer.

GRT for years has had "calculated AoA", using attitude and acceleration to come up with a proxy for AoA. All accounts I've read here and elsewhere indicate it's pretty close to reality.

GRT has recently come out with the "Sensed AoA" option to be added to the AHARS package. This option ($250) adds a third pressure sensing port to the AHARS package - it's a small black plastic nipple mounted between and below the two 1/8NPT pitot/static fittings on the AHARS.

If you have the Sensed AoA option on your AHARS then you will need some form of AoA sensing pitot head. If you don't have the Sensed AoA option on your AHARS then you don't have the capability to sense the pressure differential provided by an AoA sensing pitot.

In our case I upgraded our AHARS to the new Adaptive AHARS and added both the Sensed AoA and the internal GNSS multi-constellation satellite receiver options.

Our aircraft was provisioned for a standard heated pitot so I just added an AoA sensor port directly behind the pitot. That sensor port is a piece of 1/8" aluminum tubing mounted in a simple aluminum base that screws onto the lower wing skin. The aluminum tubing is bent downwards at an angle as indicated in the RV12 discussion thread referenced in an earlier post here. Total cost to fabricate the AoA sensor would be on the order of $5. It works a charm!

[catmandu]

You can read about my experience going off the reservation with my GRT if you like.

[Bill Boyd]

So, JOY, your AOA port is not heated, and not something that you'd trust in icing conditions? Just curious.