Mxsmanic wrote:
Dudley Henriques writes:

Not a moment's hesitation.......An angle of attack indicator.

I can understand that. Why are angle-of-attack indicators so rare in
aircraft? Is it something that is difficult to measure? I should think it
would be far more useful than trying to figure out what combination of speed,
weight, pitch angle, etc., is likely to produce a stall.

You are absolutely correct. The military for years has used AOA to
determine cruise, climb, descent, and approach speeds. Almost all high
performance aircraft performance charts use AOA to determine performance
criteria.
For example, a T38 is flown on approach at an optimum AOA of .6 units.
This optimizes the aircraft at whatever approach airspeed the GW
dictates. (remaining fuel). The aircraft can also be flown manually on
approach using an IAS of 155kts plus fuel, which is an additional 1kt
for every l00lbs remaining over 1000lbs. You can fly the approach either
way but as you can see, it's a lot easier using AOA.
Some T38's BTW, incorporate an AOA indexer on the glare shield that will
automatically keep you on speed if you fly the airplane in the on speed
green "donut". The top of the indexer is a red chevron pointing downward
to indicate you're too slow on the approach. The bottom is a red chevron
pointing upward showing too high an airspeed. Keeping the airplane right
on speed in the green donut gives you .6 units AOA regardless of the
gross weight of the airplane.
To expand just a bit on the T38, the AOA indicator shows up as arbitrary
"units" ranging from 0 to 1.0 based on the angle range of the AOA vane.
Some other helpful data supplied by the AOA indicator if I remember
right for the Talon is a maximum range at about .2 units, and a maximum
endurance at .3 units. Initial stall buffet is t about .9 units.

In light civilian airplanes, AOA indicators can be quite useful although
the low speeds involved don't necessarily produce the same advantages
found in much higher performance airplanes where the slightest
difference between optimum and off optimum AOA for a specific
configuration can mean big differences in performance.

Personally, I like the idea of basing even light airplane performance on
AOA. If this format is begun at the manufacturer's level and proper
testing on the aircraft done at that point, the end user has a simple
and precise instrument on which to base the aircraft's performance. This
decreases cockpit workload which is a good thing in itself.

It is my understanding after talking to some ATR (ATP) friends of mine
flying for major air carriers that their companies have been engaged
with manufacturers on better ways to use AOA in their aircraft operations.

--
Dudley Henriques