Angle of Attack Indicators

As I understand it, when jet aircraft were flown from aircraft
carriers, procedures and equipment used with piston aircraft proved
inadequate, and the United States adopted a set of devices developed
by the British, including the angled deck, the optical glide path, and
the angle of attack indicator. By the time the Douglas Skyhawk was
built, the angle of attack (AOA) indicator was used with a head up
display.

Was the head up display used from the beginning, or were there earlier
types of AOA indicators with some type of panel display?

Were AOA indicators retrofitted to earlier types of aircraft designed
without AOA equipment?

When did AOA indicators begin to be installed on Air Force planes?

Thank you,
Peter Wezeman
anti-social Darwinist

On Jul 26, 8:29*am, wrote:
As I understand it, when jet aircraft were flown from aircraft
carriers, procedures and equipment used with piston aircraft proved
inadequate, and the United States adopted a set of devices developed
by the British, including the angled deck, the optical glide path, and
the angle of attack indicator. By the time the Douglas Skyhawk was
built, the angle of attack (AOA) indicator was used with a head up
display.

Was the head up display used from the beginning, or were there earlier
types of AOA indicators with some type of panel display?

Were AOA indicators retrofitted to earlier types of aircraft designed
without AOA equipment?

When did AOA indicators begin to be installed on Air Force planes?

Thank you,
Peter Wezeman
anti-social Darwinist

There are two types of sensor, a simple stall warning switch placed at
the stagnation point at whcih stall would occur on the leading edge of
the wing and the more sophisticated type that actually gives precise
angle of attack.

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 single engine piston aircraft you will see the mounted on the wing
tips.

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.

Some aircraft have an Air Data Probe mounted in the nose which
combines AOA, side slip and pitot static (properly called a prandl
tube). Usually used for testing due to its precision.

Military aircraft have a sort of conical or tube shaped devise with
two pressure ports offsest slightly, these have pressure sensors in
them that drive a servo motor till they are in balance. This is a
'pressure nulling sensor'

I believe the Grumman Cougar gave zero stall warning however an AOA
sensor, stick shaker and stick pusher fixed that and gave plenty of
warning.

I don't see the point giving an aircraft a lot of stall warning as in
say a spitfire by given a lot of washout when sensors can now do the
job. Reducing aerodynamic efficiency to give a progressive stall
development is giving away turning circle and aerodynamic efficiency.
Aircraft such as the Ta 152H had such a large degree of washout (3
degrees) they were apparently fully controllable in roll during the
stall.

Of course you still want good post stall recovery. Slats strike me as
a good way to do that.

In FBW aircraft the AOA, side slip and prandl sensor data are fed to
the ADIRU (air data inertial reference unit) a sort of box of
gyroscopes and accelerometers that keeps track of up and smoothes' the
jittery aerodynamic data.

That Airfrance Flight 547 that crashed in the Atlantic eroute from
Brazil to France probably losts its pitot static tube.

Normally A330 airbuses have a Honeywell ADIRU with BF Goodrich pitot
static tubes but Air France took the optional Thales Units whose pitot
tube have a tendancy to not drain water properly and ice up.
Apparently the A320 doesn't suffer from this and A330s are getting the
A320 sensors

Once iced up the FBW system would have detected the inconsistencies
and switched the control laws from full to secondary, a sort of semi
automatic mode where stall protection and flight envelop protection is
reduced. The pilot now has to fly manually.

It would have lmited the rudder to stop the pilot from over stressing
it accidently.

Flying an aircraft whether it be FBW or Normal cabled aircraft without
pitot static data at night and the middle of a storm is not easy.

On Jul 27, 11:48*pm, wrote:
On Jul 26, 8:29*am, wrote:



As I understand it, when jet aircraft were flown from aircraft
carriers, procedures and equipment used with piston aircraft proved
inadequate, and the United States adopted a set of devices developed
by the British, including the angled deck, the optical glide path, and
the angle of attack indicator. By the time the Douglas Skyhawk was
built, the angle of attack (AOA) indicator was used with a head up
display.

Was the head up display used from the beginning, or were there earlier
types of AOA indicators with some type of panel display?

Were AOA indicators retrofitted to earlier types of aircraft designed
without AOA equipment?

When did AOA indicators begin to be installed on Air Force planes?

Thank you,
Peter Wezeman
anti-social Darwinist

There are two types of sensor, a simple stall warning switch placed at
the stagnation point at whcih stall would occur on the leading edge of
the wing and the more sophisticated type that actually gives precise
angle of attack.

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 single engine piston aircraft you will see the mounted on the wing
tips.

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?

Some aircraft have an Air Data Probe mounted in the nose which
combines AOA, side slip and pitot static (properly called a prandl
tube). *Usually used for testing due to its precision.

Military aircraft have a sort of conical or tube shaped devise with
two pressure ports offsest slightly, these have pressure sensors in
them that drive a servo motor till they are in balance. *This is a
'pressure nulling sensor'

I believe the Grumman Cougar gave zero stall warning however an AOA
sensor, stick shaker and stick pusher fixed that and gave plenty of
warning.



In FBW aircraft the AOA, side slip and prandl sensor data are fed to
the ADIRU (air data inertial reference unit) a sort of box of
gyroscopes and accelerometers that keeps track of up and smoothes' the
jittery aerodynamic data.

That Airfrance Flight 547 that crashed in the Atlantic eroute from
Brazil to France probably losts its pitot static tube.

Normally A330 airbuses have a Honeywell ADIRU with BF Goodrich pitot
static tubes but Air France took the optional Thales Units whose pitot
tube have a tendancy to not drain water properly and ice up.
Apparently the A320 doesn't suffer from this and A330s are getting the
A320 sensors

Once iced up the FBW system would have detected the inconsistencies
and switched the control laws from full to secondary, a sort of semi
automatic mode where stall protection and flight envelop protection is
reduced. *The pilot now has to fly manually.

I once read that the control sticks on Airbus planes do not have force
feedback. If this is still the case, what is the procedure for
manually flying the plane without overstressing it?

It would have lmited the rudder to stop the pilot from over stressing
it accidently.

Flying an aircraft whether it be FBW or Normal cabled aircraft without
pitot static data at night and the middle of a storm is not easy.

Thank you again,
Peter Wezeman
anti-social Darwinist

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).

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.