Angle of Attack Indicators

On Jul 29, 10:25*pm, "JR Weiss" wrote:
wrote:
In passenger jet aircraft you will notice usually 4 of these 'vanes'
mounted to either side of the cockpit. *An A320 has two either side
an A380 no less than 4 either side. *(Pre FBW these were seperate
for pilot an co pilot)
In Jets you will usually see similar vertical vanes mounted on the
nose to measure side slip.
A modern stall warning system uses not only Angle of Attack but side
slip to calculate stall warnings since the prescence of side slip
effects stall angle, presumably due to the greatee distance the air
must flow over the wing during side slip.
Thank you very much for your reply. Military fighter and attack planes
have angle of attack displays visible to the pilot. Do you see any
advantage to having something like this for pilots of airliners,
possibly for use as part of normal flying routine, possibly as a back-
up and cross check for airspeed information?

Unfortunately, the "experts" in the Transport Category Airplane world
have deemed AOA readouts as superfluous. *Their argument (among others)
is that optimum AOA for any particular operation is not constant for a
large range of gross weights, so Vref or V2 as defined by the FAA and
other regulatory agencies is "better."

After 20 years of aircraft carrier operations and 11 years of airline
operations I tend to disagree, but I'm not an aerodynamicist...

FWIW, the sideslip vanes may be on Airbusses, but they're not on the
747, and I haven't noticed them on any other Boeings. *Harriers had
them, and Tomcats had yaw strings (simple and effective).

Hi John;

I've heard the same thing from the airline industry, and I think they
might have a point. I've always wondered how you guys handle the vast
differences in gross weights you have when you arrive at the initial
approach fix.
The Navy as we both know, requires a very stable approach profile so
AOA is great for them, as it automatically compensates for the
differences in approach weight and the approach is the same AOA
regardless of weight. But this assumes a fairly (or at least
comparatively anyway) narrow gross weight for the Navy when arriving
for the approach on the boat.
You guys in the majors deal with what could loosely be described by a
Navy fighter pilot as a fair to middling gross weight range on
approach. My guess would be that using an optimum AOA on approach
might very well not be as viable as using a Vref. I would of course
bow to your better judgment on this since you have time in the big
boys and I don't.
I remember seeing a report from Boeing a while back where they were
"discussing" the addition of AOA to the approach equation both with
adjusted procedures and panel changes regarding instrumentation.
If I remember right, the bottom line on their research was that the
front offices and chief pilots of various majors couldn't reach a
consensus on the issue strong enough to warrant a major policy change
at the top level. There were specific lines who were willing to have
their panels equipped with a change from a peripheral AOA indicator to
a prominent place on the glass for an AOA tape on the approach mode,
but I never followed this through enough to discover were if anywhere
everybody went with all this.
Dudley

Dudley Henriques wrote:

Unfortunately, the "experts" in the Transport Category Airplane
world have deemed AOA readouts as superfluous. *Their argument
(among others) is that optimum AOA for any particular operation is
not constant for a large range of gross weights, so Vref or V2 as
defined by the FAA and other regulatory agencies is "better."

After 20 years of aircraft carrier operations and 11 years of
airline operations I tend to disagree, but I'm not an
aerodynamicist...

I've heard the same thing from the airline industry, and I think they
might have a point. I've always wondered how you guys handle the vast
differences in gross weights you have when you arrive at the initial
approach fix.
The Navy as we both know, requires a very stable approach profile so
AOA is great for them, as it automatically compensates for the
differences in approach weight and the approach is the same AOA
regardless of weight. But this assumes a fairly (or at least
comparatively anyway) narrow gross weight for the Navy when arriving
for the approach on the boat.
You guys in the majors deal with what could loosely be described by a
Navy fighter pilot as a fair to middling gross weight range on
approach. My guess would be that using an optimum AOA on approach
might very well not be as viable as using a Vref. I would of course
bow to your better judgment on this since you have time in the big
boys and I don't.
I remember seeing a report from Boeing a while back where they were
"discussing" the addition of AOA to the approach equation both with
adjusted procedures and panel changes regarding instrumentation.
If I remember right, the bottom line on their research was that the
front offices and chief pilots of various majors couldn't reach a
consensus on the issue strong enough to warrant a major policy change
at the top level. There were specific lines who were willing to have
their panels equipped with a change from a peripheral AOA indicator to
a prominent place on the glass for an AOA tape on the approach mode,
but I never followed this through enough to discover were if anywhere
everybody went with all this.

I still believe that AOA is a more sensitive indicator of performance
than IAS at relatively low airspeeds. That may actually be the
"problem" though -- we probably don't want transport pilots pumping the
yoke to keep an "optimum" AOA and get the passengers upset...

OTOH, the range of handling differences between a "light" (33,000 lb)
and "heavy" (36,500) A-6 on the ball and a "light" (170,000 Kg) and
"heavy" (302,000 Kg) 747 are quite different (I won't address the A-4,
because it wasn't a "heavy" in any sense of the word). The A-6
differed mainly in power response on the G/S, but the 747 differs
mainly in the flare. While AOA was critical in the A-6 to keep the
hook at the proper angle of dangle to snag the 3-wire, the 747 can be
landed comfortably anywhere in the nominal 3000' landing area (first
1/3) of a typical runway.

OTOOH, I think a "real" AOA indicator would be VERY helpful in escape
maneuvers for WindShear and Terrain warnings. The stick shaker is a
useful On/Off switch for backpressure, but a trend indicator via AOA
would be much more useful.

On Jul 30, 12:03*am, "JR Weiss" wrote:
Dudley Henriques wrote:
Unfortunately, the "experts" in the Transport Category Airplane
world have deemed AOA readouts as superfluous. *Their argument
(among others) is that optimum AOA for any particular operation is
not constant for a large range of gross weights, so Vref or V2 as
defined by the FAA and other regulatory agencies is "better."

After 20 years of aircraft carrier operations and 11 years of
airline operations I tend to disagree, but I'm not an
aerodynamicist...
I've heard the same thing from the airline industry, and I think they
might have a point. I've always wondered how you guys handle the vast
differences in gross weights you have when you arrive at the initial
approach fix.
The Navy as we both know, requires a very stable approach profile so
AOA is great for them, as it automatically compensates for the
differences in approach weight and the approach is the same AOA
regardless of weight. But this assumes a fairly (or at least
comparatively anyway) narrow gross weight for the Navy when arriving
for the approach on the boat.
You guys in the majors deal with what could loosely be described by a
Navy fighter pilot as a fair to middling gross weight range on
approach. My guess would be that using an optimum AOA on approach
might very well not be as viable as using a Vref. I would of course
bow to your better judgment on this since you have time in the big
boys and I don't.
I remember seeing a report from Boeing a while back where they were
"discussing" the addition of AOA to the approach equation both with
adjusted procedures and panel changes regarding instrumentation.
If I remember right, the bottom line on their research was that the
front offices and chief pilots of various majors couldn't reach a
consensus on the issue strong enough to warrant a major policy change
at the top level. There were specific lines who were willing to have
their panels equipped with a change from a peripheral AOA indicator to
a prominent place on the glass for an AOA tape on the approach mode,
but I never followed this through enough to discover were if anywhere
everybody went with all this.

I still believe that AOA is a more sensitive indicator of performance
than IAS at relatively low airspeeds. *That may actually be the
"problem" though -- we probably don't want transport pilots pumping the
yoke to keep an "optimum" AOA and get the passengers upset...

OTOH, the range of handling differences between a "light" (33,000 lb)
and "heavy" (36,500) A-6 on the ball and a "light" (170,000 Kg) and
"heavy" (302,000 Kg) 747 are quite different (I won't address the A-4,
because it wasn't a "heavy" in any sense of the word). *The A-6
differed mainly in power response on the G/S, but the 747 differs
mainly in the flare. *While AOA was critical in the A-6 to keep the
hook at the proper angle of dangle to snag the 3-wire, the 747 can be
landed comfortably anywhere in the nominal 3000' landing area (first
1/3) of a typical runway.

OTOOH, I think a "real" AOA indicator would be VERY helpful in escape
maneuvers for WindShear and Terrain warnings. *The stick shaker is a
useful On/Off switch for backpressure, but a trend indicator via AOA
would be much more useful.

It's an interesting subject and I'm sure in any end analysis, aoa
could be integrated into the heavy environment. more than it has been.
Personally I like aoa. I've always taught wing and energy management
flying from Cubs to high performance singles.
The future may very well reveal the benefits of aoa to a wider cross
section of the commercial community. Hope so anyway! :-)
DH

On Jul 29, 9:48 pm, Dudley Henriques wrote:
On Jul 30, 12:03 am, "JR Weiss" wrote:



Dudley Henriques wrote:
Unfortunately, the "experts" in the Transport Category Airplane
world have deemed AOA readouts as superfluous. Their argument
(among others) is that optimum AOA for any particular operation is
not constant for a large range of gross weights, so Vref or V2 as
defined by the FAA and other regulatory agencies is "better."

After 20 years of aircraft carrier operations and 11 years of
airline operations I tend to disagree, but I'm not an
aerodynamicist...
I've heard the same thing from the airline industry, and I think they
might have a point. I've always wondered how you guys handle the vast
differences in gross weights you have when you arrive at the initial
approach fix.
The Navy as we both know, requires a very stable approach profile so
AOA is great for them, as it automatically compensates for the
differences in approach weight and the approach is the same AOA
regardless of weight. But this assumes a fairly (or at least
comparatively anyway) narrow gross weight for the Navy when arriving
for the approach on the boat.
You guys in the majors deal with what could loosely be described by a
Navy fighter pilot as a fair to middling gross weight range on
approach. My guess would be that using an optimum AOA on approach
might very well not be as viable as using a Vref. I would of course
bow to your better judgment on this since you have time in the big
boys and I don't.
I remember seeing a report from Boeing a while back where they were
"discussing" the addition of AOA to the approach equation both with
adjusted procedures and panel changes regarding instrumentation.
If I remember right, the bottom line on their research was that the
front offices and chief pilots of various majors couldn't reach a
consensus on the issue strong enough to warrant a major policy change
at the top level. There were specific lines who were willing to have
their panels equipped with a change from a peripheral AOA indicator to
a prominent place on the glass for an AOA tape on the approach mode,
but I never followed this through enough to discover were if anywhere
everybody went with all this.

I still believe that AOA is a more sensitive indicator of performance
than IAS at relatively low airspeeds. That may actually be the
"problem" though -- we probably don't want transport pilots pumping the
yoke to keep an "optimum" AOA and get the passengers upset...

OTOH, the range of handling differences between a "light" (33,000 lb)
and "heavy" (36,500) A-6 on the ball and a "light" (170,000 Kg) and
"heavy" (302,000 Kg) 747 are quite different (I won't address the A-4,
because it wasn't a "heavy" in any sense of the word). The A-6
differed mainly in power response on the G/S, but the 747 differs
mainly in the flare. While AOA was critical in the A-6 to keep the
hook at the proper angle of dangle to snag the 3-wire, the 747 can be
landed comfortably anywhere in the nominal 3000' landing area (first
1/3) of a typical runway.

OTOOH, I think a "real" AOA indicator would be VERY helpful in escape
maneuvers for WindShear and Terrain warnings. The stick shaker is a
useful On/Off switch for backpressure, but a trend indicator via AOA
would be much more useful.

It's an interesting subject and I'm sure in any end analysis, aoa
could be integrated into the heavy environment. more than it has been.
Personally I like aoa. I've always taught wing and energy management
flying from Cubs to high performance singles.
The future may very well reveal the benefits of aoa to a wider cross
section of the commercial community. Hope so anyway! :-)
DH

Referring to sims, I found the AoA indicator of scientific interest
to measure airfoil performance, but in shooting landings I relied
on the IAS (knots/hr) and vertical airspeed indicator(feet/minute),
those together give a rough idea of angle of descent, and one
then gets a feeling of AoA from pitch.
What might be considered is an instrument that can provide all
that info in nice clear form on single gauge at a glance, let's
design it.
Ken

Ken S. Tucker wrote:

Referring to sims, I found the AoA indicator of scientific interest
to measure airfoil performance, but in shooting landings I relied
on the IAS (knots/hr) and vertical airspeed indicator(feet/minute),
those together give a rough idea of angle of descent, and one
then gets a feeling of AoA from pitch.

Yes, you can get a "feel" of AOA from all that, but not enough to fly
AOA with the accuracy required in modern carrier operations. A half
degree of pitch or a decel/accel trend that you don't see in time could
be the difference between a safe landing and a bolter or worse.

BTW, IAS is measured in knots, not knots/hr. A knot is a nautical
mile/hour, so "knots/hour" would be an acceleration, not a velocity.


What might be considered is an instrument that can provide all
that info in nice clear form on single gauge at a glance, let's
design it.

Can't do it; there are too many different types of measurements to be
made and displayed. While a velocity vector pointer on a HUD may give
a good portion of it, speed is missing...

Hi JR.

On Aug 5, 12:22 am, "JRWeiss" wrote:
Ken S. Tucker wrote:
Referring to sims, I found the AoA indicator of scientific interest
to measure airfoil performance, but in shooting landings I relied
on the IAS (knots/hr) and vertical airspeed indicator(feet/minute),
those together give a rough idea of angle of descent, and one
then gets a feeling of AoA from pitch.

Yes, you can get a "feel" of AOA from all that, but not enough to fly
AOA with the accuracy required in modern carrier operations. A half
degree of pitch or a decel/accel trend that you don't see in time could
be the difference between a safe landing and a bolter or worse.

BTW, IAS is measured in knots, not knots/hr. A knot is a nautical
mile/hour, so "knots/hour" would be an acceleration, not a velocity.

What might be considered is an instrument that can provide all
that info in nice clear form on single gauge at a glance, let's
design it.

Can't do it; there are too many different types of measurements to be
made and displayed. While a velocity vector pointer on a HUD may give
a good portion of it, speed is missing...

Indicator-instrumentation is subjective, so I'll shoot from the hip.

Let DV be rate of ascent, vertically directed, with a length.

Let IAS be Indicated AirSpeed be a vector with length and direction.
The IAS vector is a hypotenuse, let HAS be Horizotal AirSpeed then

IAS^2 = DV^2 + HAS^2

forms a right angle triangle. The IAS and DV come from standard
measurements and the HAS is readily derived, so we have
Ascent Angle embodied in the IAS vector, (pardon the math).

Next, we include Pitch, that is a measurement derived from the
artifical horizon. From those the AoA is

AoA = Ascent Angle - Pitch.

On an actual display, suppose we display the IAS as a vector,
with lengths that are colored green, yellow, red, with red-yellow
demarking a near stall, as well as the Pitch vector, then at the
origin of those displayed vectors, you can print out AoA to .1 degree
accuracy, sufficient for most pilots.

In my experience, some guys like dials (like clock hands) others
like digital, that was a hassle when Volt-Ohm meters went digital,
lots of arguments. Personally I like both. The meter provides a
sense of rate of change, but the digital provides precison at a
glance, so I think the 'AoA' indicator ought to be designed to
reflect those concerns and conditions.

One question, would you want a g-force indicator?
Ken

Ken S. Tucker wrote:

Referring to sims, I found the AoA indicator of scientific
interest to measure airfoil performance, but in shooting landings
I relied on the IAS (knots/hr) and vertical airspeed
indicator(feet/minute), those together give a rough idea of angle
of descent, and one then gets a feeling of AoA from pitch.

Yes, you can get a "feel" of AOA from all that, but not enough to
fly AOA with the accuracy required in modern carrier operations. A
half degree of pitch or a decel/accel trend that you don't see in
time could be the difference between a safe landing and a bolter or
worse.

What might be considered is an instrument that can provide all
that info in nice clear form on single gauge at a glance, let's
design it.

Can't do it; there are too many different types of measurements to
be made and displayed. While a velocity vector pointer on a HUD
may give a good portion of it, speed is missing...

. . .

On an actual display, suppose we display the IAS as a vector,
with lengths that are colored green, yellow, red, with red-yellow
demarking a near stall, as well as the Pitch vector, then at the
origin of those displayed vectors, you can print out AoA to .1 degree
accuracy, sufficient for most pilots.

While you may have a single display here, you actually have 3 different
"gauges": Speed vector, pitch vector, and AOA readout.

In my experience, some guys like dials (like clock hands) others
like digital, that was a hassle when Volt-Ohm meters went digital,
lots of arguments. Personally I like both. The meter provides a
sense of rate of change, but the digital provides precison at a
glance, so I think the 'AoA' indicator ought to be designed to
reflect those concerns and conditions.

Modern HUDs (Head-Up Displays) have many readouts on a single display
already. As you note, there are many individual preferences, so there
is no single "standard" HUD display. You may have some interesting
ideas for the display of the information, but the concept is hardly new.


One question, would you want a g-force indicator?

In a fighter, yes. In a 747, probably not; it would be superfluous.

"Ken S. Tucker" wrote in news:56e7269b-a30f-467b-
:

In my experience, some guys like dials (like clock hands) others
like digital, that was a hassle when Volt-Ohm meters went digital,
lots of arguments. Personally I like both. The meter provides a
sense of rate of change, but the digital provides precison at a
glance, so I think the 'AoA' indicator ought to be designed to
reflect those concerns and conditions.

Slightly OT.

I'm a retired cal tech. Regarding the meter thing, all that "precision"
wasn't really worth a rat's ass, since the accuracy of many digital VOMs
wasn't any better (usually in the 2% - 4% FS area) than the d'Arsonval
movement units they replaced. I still use my 25 yo Simpson 260 more than I do
my Fluke 77.

Dave in Sandy Eggo
AT1 USN Ret