Air speed off at low speeds

[Onex107]

I gotta say something about the LRI. I built mine like you said except a friend tried to drill the long holes and couldn't keep the drill centered in the 1/2 inch material. I made mime out of 1/4 in pieces and cut a groove down both sides with a cutoff wheel to help the drill. I pinned and glued the two halves together after drilling. I adjusted the angle by doing stalls. It's a little simpler in a Onex. The weight doesn't vary as much. I use the LRI exclusively during take off and landing. It's a more accurate indication of air speed and attitude than the ASI.

[jaflint]

Hi Joe:

I've been wrestling with an ASI reading 10+ mph slower than actual (CAS) at pattern speeds until tonight. After trying to solve things by bending pitot tubes and putting a wheel collar in front of the holes in the static tube to adjust ambient pressure, I decided to disconnect the static line from the external tube and just leave it in the wing -- reading static pressure from inside the wing. Now, my IAS is only about 5mph fast at stall speeds, and just about right on the money (+/- 1 mph) from 70 up through 120mph.

Keep us posted with what you find!

JF

[n502pd]

Hi Joe:

I've been wrestling with an ASI reading 10+ mph slower than actual (CAS) at pattern speeds until tonight. After trying to solve things by bending pitot tubes and putting a wheel collar in front of the holes in the static tube to adjust ambient pressure, I decided to disconnect the static line from the external tube and just leave it in the wing -- reading static pressure from inside the wing. Now, my IAS is only about 5mph fast at stall speeds, and just about right on the money (+/- 1 mph) from 70 up through 120mph.

Keep us posted with what you find!

JF

I most certianly will let all know how my littel experiment turns out. You encourage me with the info that you got closer with the static line inside the wing. I will post pix on my build site of the new potot tube and static port arraingments I installed today. other problems have to be realligned prior to further flight, mainly with the oil seperator not doing a good enough job. my site is http://www.mykitlog.com/josephnelsen and I will have the pix there shortly.

[n502pd]

thanks again Dale! I do understand the dual top and bottom holes and what they are intended to do, and I have heard of the o-ring (but had forgotten it!). What I am trying to do is have both instruments as accurate as I can. I feel that the ASI is required, but the LRI/AOA instrument isnt.My simple mind responds with..'why have two monitors of closely related data that either dont agree, or where one is in error so as to not actually use it'. I guess I just want both to work correctly, or at least as close as possible. Also, I have placed the AOA in the view out the LH side of the windshield for a very quick reference without turning my head. I am sure others have done the same. I intend to have the AOA agree with the ASI. which would agree with the stall speed. I am preaching, I know!! Sorry!

[daleandee]

I intend to have the AOA agree with the ASI. which would agree with the stall speed. I am preaching, I know!! Sorry!

Actually they won't always agree and that's the beauty of the LRI! As density altitude, gross weight, and other factors change the stall speed reading, the LRI is consistent in letting you know how hard the wing is working and how much reserve lift is available before the wing stalls.

But I understand the goal you are after and it is a commendable one ...

Dale
N319WF

[radfordc]

I feel that the ASI is required, but the LRI/AOA instrument isnt.My simple mind responds with..'why have two monitors of closely related data that either dont agree, or where one is in error so as to not actually use it'.

A properly installed and calibrated ASI will be in error quite often by its nature...in other words Indicated Airspeed seldom matches True Airspeed. Also, the Indicated Airspeed for stall will change depending on gross weight and G load.

A properly installed and calibrated AoA (LRI and other types) will always show the correct reference for stall, Vx, Vy, etc., no matter what gross weight. Stall occurs at the same angle of attack at all gross weights and G loads.