?? Lift Reserve Indicator ??

First time I've stumbled across one of these:

Lift Reserve Indicator

http://home.hiwaay.net/~sbuc/journal/liftreserve.htm
"One of the AOA systems that has been around the longest is the Lift Reserve
Indicator. This unit was developed in the 1970's and has been offered in a
couple of different variations since then. There is considerable controversy
over just what the LRI actually measures and how it operates, but when the
price of the analog unit was recently reduced substantially, it got my
attention. Since the panel of 399SB is rather unconventional, I had included
a small backup airspeed indicator. However, the AI was never used since I
rely on the RMI uEncoder for pitot info, so I decided to replace the AI with
the LRI since it could also serve as a backup airspeed indicator. The
decision was easier since the LRI would fit in the same space as the little
AI and was in the pilot's angle of vision."

http://www.liftreserve.com/
Company website - InAir Instruments


Montblack

"Montblack" wrote in message ...
First time I've stumbled across one of these:

Lift Reserve Indicator

http://home.hiwaay.net/~sbuc/journal/liftreserve.htm
"One of the AOA systems that has been around the longest is the Lift Reserve Indicator. This unit was developed in the
1970's and has been offered in a couple of different variations since then. There is considerable controversy over
just what the LRI actually measures and how it operates, but when the price of the analog unit was recently reduced
substantially, it got my attention. Since the panel of 399SB is rather unconventional, I had included a small backup
airspeed indicator. However, the AI was never used since I rely on the RMI uEncoder for pitot info, so I decided to
replace the AI with the LRI since it could also serve as a backup airspeed indicator. The decision was easier since
the LRI would fit in the same space as the little AI and was in the pilot's angle of vision."

http://www.liftreserve.com/
Company website - InAir Instruments


Montblack

Interesting, delta P between two sources, one more or less pointing forward and one more or less pointing downward. I
suppose the indicator has a pressure diaphragm inside it linked to the needle...

I want an AOA indicator for the BD4 someday...

Hmmmmmm.......

..Blueskies. wrote:
"Montblack" wrote in message ...

First time I've stumbled across one of these:

Lift Reserve Indicator

http://home.hiwaay.net/~sbuc/journal/liftreserve.htm
"One of the AOA systems that has been around the longest is the Lift Reserve Indicator. This unit was developed in the
1970's and has been offered in a couple of different variations since then. There is considerable controversy over
just what the LRI actually measures and how it operates, but when the price of the analog unit was recently reduced
substantially, it got my attention. Since the panel of 399SB is rather unconventional, I had included a small backup
airspeed indicator. However, the AI was never used since I rely on the RMI uEncoder for pitot info, so I decided to
replace the AI with the LRI since it could also serve as a backup airspeed indicator. The decision was easier since
the LRI would fit in the same space as the little AI and was in the pilot's angle of vision."

http://www.liftreserve.com/
Company website - InAir Instruments


Montblack


Interesting, delta P between two sources, one more or less pointing forward and one more or less pointing downward. I
suppose the indicator has a pressure diaphragm inside it linked to the needle...

I want an AOA indicator for the BD4 someday...

Hmmmmmm.......



A couple of years ago Kitplanes had an article about and AOA sytem
that used 2 ports flush with the wing surface near the wing tips. It's a
simplified version of a system the military has been using for decades.
The military version uses a conical probe sticking out of the side of
the fuselage. There are two sets of slots a few degrees part facing
towards the front of the airplane. These slots are ports that send air
pressure to two sensing chambers. Here's where they decided to get
complicated: the cone is then driven until the chamber measure equal
pressure. The cone's position is then transmitted to an indicator.
Obviously the system isn't for single engine tractor airplane. The
3.125" indicator is a tad big for most homebuilts, but does contain
switches for stall warning and AOA indexer lights. It seems to me some
enterprising electronics genius should be able to design a simple system
that does all this in solid state.

Dan, U.S. Air Force, retired

"Dan, U.S. Air Force, retired" wrote in message
...
.Blueskies. wrote:
"Montblack" wrote in message
...

First time I've stumbled across one of these:

Lift Reserve Indicator

http://home.hiwaay.net/~sbuc/journal/liftreserve.htm
"One of the AOA systems that has been around the longest is the Lift
Reserve Indicator. This unit was developed in the 1970's and has been
offered in a couple of different variations since then. There is
considerable controversy over just what the LRI actually measures and how
it operates, but when the price of the analog unit was recently reduced
substantially, it got my attention. Since the panel of 399SB is rather
unconventional, I had included a small backup airspeed indicator.
However, the AI was never used since I rely on the RMI uEncoder for pitot
info, so I decided to replace the AI with the LRI since it could also
serve as a backup airspeed indicator. The decision was easier since the
LRI would fit in the same space as the little AI and was in the pilot's
angle of vision."

http://www.liftreserve.com/
Company website - InAir Instruments


Montblack


Interesting, delta P between two sources, one more or less pointing
forward and one more or less pointing downward. I suppose the indicator
has a pressure diaphragm inside it linked to the needle...

I want an AOA indicator for the BD4 someday...

Hmmmmmm.......



A couple of years ago Kitplanes had an article about and AOA sytem that
used 2 ports flush with the wing surface near the wing tips. It's a
simplified version of a system the military has been using for decades.
The military version uses a conical probe sticking out of the side of the
fuselage. There are two sets of slots a few degrees part facing towards
the front of the airplane. These slots are ports that send air pressure to
two sensing chambers. Here's where they decided to get complicated: the
cone is then driven until the chamber measure equal pressure. The cone's
position is then transmitted to an indicator. Obviously the system isn't
for single engine tractor airplane. The 3.125" indicator is a tad big for
most homebuilts, but does contain switches for stall warning and AOA
indexer lights. It seems to me some enterprising electronics genius should
be able to design a simple system that does all this in solid state.

Dan, U.S. Air Force, retired

I'd also like an electronic AOA indicator. There are several probes that
work on three pressure pickups like
(http://www.cgmasi.com/aviation/index.html). In sailplanes we can just
tape a couple of yarns of the side of the canopy and mark the inside with
grease pencil.

bildan

"Bill Daniels" bildan@comcast-dot-net wrote in message ...

"Dan, U.S. Air Force, retired" wrote in message ...


A couple of years ago Kitplanes had an article about and AOA sytem that used 2 ports flush with the wing surface
near the wing tips. It's a simplified version of a system the military has been using for decades. The military
version uses a conical probe sticking out of the side of the fuselage. There are two sets of slots a few degrees part
facing towards the front of the airplane. These slots are ports that send air pressure to two sensing chambers.
Here's where they decided to get complicated: the cone is then driven until the chamber measure equal pressure. The
cone's position is then transmitted to an indicator. Obviously the system isn't for single engine tractor airplane.
The 3.125" indicator is a tad big for most homebuilts, but does contain switches for stall warning and AOA indexer
lights. It seems to me some enterprising electronics genius should be able to design a simple system that does all
this in solid state.

Dan, U.S. Air Force, retired

I'd also like an electronic AOA indicator. There are several probes that work on three pressure pickups like
(http://www.cgmasi.com/aviation/index.html). In sailplanes we can just tape a couple of yarns of the side of the
canopy and mark the inside with grease pencil.

bildan


Here is an electronic version: http://advanced-control-systems.com/AOA/aoa.htm

Two pickups; one on the top of the wing and one on the bottom...

In article ,
"Montblack" wrote:

First time I've stumbled across one of these:

Lift Reserve Indicator

http://home.hiwaay.net/~sbuc/journal/liftreserve.htm
"One of the AOA systems that has been around the longest is the Lift Reserve
Indicator. This unit was developed in the 1970's and has been offered in a
couple of different variations since then. There is considerable controversy
over just what the LRI actually measures and how it operates, but when the
price of the analog unit was recently reduced substantially, it got my
attention. Since the panel of 399SB is rather unconventional, I had included
a small backup airspeed indicator. However, the AI was never used since I
rely on the RMI uEncoder for pitot info, so I decided to replace the AI with
the LRI since it could also serve as a backup airspeed indicator. The
decision was easier since the LRI would fit in the same space as the little
AI and was in the pilot's angle of vision."

http://www.liftreserve.com/
Company website - InAir Instruments


Montblack

Hey, most of you old guys are even older than I am. Didn't they used to
hang AOA indicators on the wing struts of biplanes? A little flat plate
that moved a big needle around a graduated arc as it was pushed by the
relative wind? Sort of like a weathervane. Or was that just an airspeed
indicator I'm thinking of?

Icebound wrote:
".Blueskies." wrote in message
t...


Interesting, delta P between two sources, one more or less pointing
forward and one more or less pointing downward.



Basically a stall horn, with the lowered pressure activating a meter instead
of a sound-producing reed. As the pressure falls at the horn, the needle
swings deeper toward the red.


Are we sure that the sensor is a pressure type sensor?

The A-4 Skyhawk uses a paddle type vane on the side of the aircraft's nose.
I'm assuming a simple potentiometer is attached to the vane to read position.
Very straight forward mechanical approach.

Another approach would be to use a pair of thremosistors carefully positioned
inside the slots of the external sensor.

Differences in the air flow inside the two slots (as mentioned previously)
would cause temperature variations of the thremosistors according to AoA.

The electrical difference between the two thremosistors is properly scaled and
can be used to monitor AoA.

I don't have my "library" handy. All that is still packed up in storage.
So I can't pull the relevant details up this morning.
But the Sport Aviation index came up with the references listed below.

Food for thought....

Richard


References:

May '78
Preliminary Report-Development of a Poor Man's VFR Autopilot/Don Hewes

March '79
Update On The Poorman's Autopilot... by Donald E. Hewes

February '80
Autopilot System For Homebuilt Airplanes... by Don Hewes

August '80
Fine Tuning The Electro-Fluidic Autopilot.. . by Doug Garner

April '81
Muscle For Your Homebuilt Autopilot... by Don Hewes

November '81
A Magnetic Heading Reference For The Electro Fluidic Autopilot,Part I
by Doug Garner

December '81
Magnetic Heading Performance For The Electro Fluidic Autopilot
Part 11 . . , by Doug Garner

I downloaded a homebuilt version of a AOA some time ago. If you want it
contact me and I will I will attach a copy and send it to you.





"Montblack" wrote in message
...
First time I've stumbled across one of these:

Lift Reserve Indicator

http://home.hiwaay.net/~sbuc/journal/liftreserve.htm
"One of the AOA systems that has been around the longest is the Lift
Reserve Indicator. This unit was developed in the 1970's and has been
offered in a couple of different variations since then. There is
considerable controversy over just what the LRI actually measures and how
it operates, but when the price of the analog unit was recently reduced
substantially, it got my attention. Since the panel of 399SB is rather
unconventional, I had included a small backup airspeed indicator. However,
the AI was never used since I rely on the RMI uEncoder for pitot info, so
I decided to replace the AI with the LRI since it could also serve as a
backup airspeed indicator. The decision was easier since the LRI would fit
in the same space as the little AI and was in the pilot's angle of
vision."

http://www.liftreserve.com/
Company website - InAir Instruments


Montblack

The last vane-type indicator I witnessed was hanging on the strut of a
New Standard DB-25 (circa 1926). It was an airspeed indicator and
appeared to function quite well from my perspective in the forward-left
front seat.

Orville Wright used a vane-type device in the autopilot system he
invented. While this was the world's first functional autopilot, it
never became popular. Sperry's gyroscopic autopilot system hit the
market shortly after, and was superior.

I'm not familiar with any vane-type AOA indicators that could be
mounted on a strut, but that doesn't mean that they didn't exist. If
anyone knows of one, I'd like to see it.

Harry

On 14 Feb 2006 08:29:37 -0800, "wright1902glider"
wrote:

I'm not familiar with any vane-type AOA indicators that could be
mounted on a strut, but that doesn't mean that they didn't exist. If
anyone knows of one, I'd like to see it.

I saw a very simple one in Kitplanes years ago. It was a vane
attached to a backing plate that was painted white, and had degrees on
it, and a big red area that represented the critical angle of attack,
beyond which the airplane stalled.

It was mounted to the wing strut in a vertical position so that you
could see it by turning your head left. Or right, it doesn't matter
on which side you mount it.

There were other versions of this that connected the vane to a
transducer which then transmitted the angle of the vane to a display
on the instrument panel.

I've always thought this (AOA indicator) was a good idea.

Corky Scott