“Does anyone have the Chelton system AND one of the
AOA insturments installed, and has operational experience comparing the
Chelton's depiction of impending stall with the AOA's sequential indication of
impending stall?”
I have the
early Jim Frantz AOA unit (now called AOA Pro) and the early Chelton IDU-1 with
Pinpoint GADAHRS. I fly AOA for approach, with the modification
that when it gets bumpy, the AOA is very sensitive and quick, too fast to be
truly useful, so I cross check between AOA and airspeed which is much slower to
respond, and then fly airspeed once I have conformed the AOA that I want at a particular
landing weight.
The Chelton
is set up to speak in the head set along with the engine monitor. Since
my intercom has only two unswitched inputs, my AOA does not verbally
annunciate. However, my AOA is directly in my field of view (see photo) since
I use it as the primary indicator on final approach.
The Chelton
does a good job, particularly in the pattern when relatively slow and you bank
the airplane. It presents the visual stall warning descending half circle
in yellow if you tighten the base to final turn too much.
However, the
Chelton is not weight compensated when you are straight and level, one G.
For my airplane which is non-pressurized, the difference between light (pilot
only 20 gallons of fuel, about 2300 pounds) and heavy (four porkers, some
baggage and full fuel, about 3300 pounds) is substantial (43%), and substantial
adjustments in speed (like 20%) are required. I have no winglets or wing
span increases, just the bare 30 foot wing.
When light I
slow enough on final (maybe 90 knots) that the Chelton starts to display
warnings since it is calibrated to a heavier condition and thinks the airplane
is going too slow, but the airplane will still float on flare. When
really heavy, approaching maybe 105 or more on short final, the AOA shows the
lift reserve is getting smaller and smaller, but even through flare the Chelton
never squawks. Therefore the margin with the Chelton is fine when heavy,
but excessive when light the way I have it set up.
Conversely,
if you set your Chelton stall speeds based on flying at midweight, the Chelton
may not provide enough margin when heavy.
The AOA
always delivers a good result. Line up the bars at the right point and it
flies onto the runway with no float and stays planted, regardless of weight.
However, the amount of braking difference between heavy and light is
substantial as you might surmise.
Fred