I dont see them neccessary unless you are landing on a aircraft carrier.
I just don't know a lot about them. I understand what they do but they just dont seem neccessary unless you are landing a jet to an aircraft carrier where every bit of precise information is neccessary.
And now I see them on the Cessna 172SP planes.
Long story short. How important they are for aircraft carrier pilots and Cessna students/pilots?
They’re super useful once you get used to them. No matter your weight, if you fly at the right AOA you’ll have the right stall margin. It is easier to see the indexer than the ASI, for control on approach. It acts like a pitch rate indicator too, if you are rough with the nose, so it helps to smooth out the flying. Responds much faster than the ASI. If you are maneuvering aggressively, it will give you that stall margin too.
Update with nice paper from AIAA Journal of Aircraft:
"Low-Cost Accurate Angle-of-Attack System", Borja Martos and David F. Rogers, Journal of Aircraft 2018 55:2, 660-665
...The angle of attack for maximum lift-to-drag ratio corresponds to maximum range and maximum glide ratio for a piston engine- propeller aircraft. Hence, in a fuel critical situation and/or an engine failure situation, it is critical that the pilot have accurate access to this angle of attack.
With today’s fuel costs, the Carson cruise [1] angle of attack, which represents the most efficient way to fly fast with the least increase in fuel consumption, is of significant interest.
The angle of attack for maximum lift-to-drag ratio does not depend on density altitude, weight, or load factor but only on aircraft design parameters and aircraft configuration. Similarly, the angles of attack for minimum power required and Carson cruise depend only on aircraft design parameters and configuration...
Therefore, a low-cost, accurate, full envelope, easy to flight calibrate angle-of-attack system is a transformative technology for light general aviation aircraft.
Accidental stalls are fairly common, especially for new pilots, and that's why we have stall warning devices--and train pilots to immediately recover as soon as they hear/see them. However, simple devices don't tell you anything until you're right on the edge. For more complete information, you need an AOA sensor. Once you have that sensor, why not display that information to the pilot? If you have a glass cockpit, the cost of adding one more data item on the display is pretty much zero, and it might be useful to some pilots--regardless of whether they're flying a trainer, an airliner, or a fighter.
Planes that fly off aircraft carriers rely on them heavily. They not only have indexer lights in the cockpit, but they also have them on the outside of the plane (usually on the nose gear doors) so the Landing Signals Officer on the boat can see them as well. Depending on the aircraft, they might not even turn on unless the landing gear is down, because they're calibrated for approach speeds.
On the planes I'm more familiar with, we rarely use it at all because it's a real pain to calibrate. We also have two independent pitot-static systems, so a loss of all airspeed indications is a remote (but not impossible) scenario.
