4 ms·

Another data point to remind everyone how AoA is one of the most important metrics wrt flying an airplane (airspeed is right up there, too). Obligatory citatio

Another data point to remind everyone how AoA is one of the most important metrics wrt flying an airplane (airspeed is right up there, too). Obligatory citation; imho, one of the webs's great resources— https://www.av8n.com/how/htm/aoa.html#sec-aoa-intro https://www.av8n.com/how/htm/aoa.html#sec-aoa-intro

mikeash 8y ago
Airspeed is mostly, although not entirely, important as a proxy for angle of attack.
dsfyu404ed 8y ago
But you don't need a dedicated sensor for it. The artificial horizon does that job too. Edit: To be more clear, the artificial horizon combined with other sources of information available to the pilot (airspeed, stall indicator) provide the pilot with the same level of situational awareness as knowing his/her AOA outright from a dedicated sensor.
- danaliv 8y ago
  The artificial horizon doesn't indicate angle of attack. Please see this comment: https://news.ycombinator.com/item?id=19638250 https://news.ycombinator.com/item?id=19638250 Or consider an aerobatic airplane at the first vertical point in a loop. The airplane's pitch is 90° but the angle of attack is less than 10°.
  - dsfyu404ed 8y ago
    You're right but the vast majority of the time the difference between the AI and the AOA is close to zero (plus whatever the angle of the wing is relative to the fuselage which is fixed and should be pretty small anyway). The times when the difference between the AOA and the AI is very different than zero in a bad way the little stall switch on the wing and some sort of chime/buzzer will be more than happy to let the pilot know. My point is that the AI combined with the little stall switch on the wing seem to be good enough for the overwhelming majority of cases. Add in airspeed and you're more than covered. We keep trying to add systems to cover whatever remaining edge cases we find but those systems have failure modes too so we take three steps forward and two steps back. These systems pick up the slack when the pilot might be inattentive but the increased complexity and cognitive load poses other risks.
    - lutorm 8y ago
      Loss of control during approach and landing because of poor airspeed control kills pilots every year. It's important enough that the EAA has a dedicated "loss of control initiative" to try to figure out what to do. See for example https://www.eaa.org/eaa/news-and-publications/eaa-news-and-aviation-news/news/01-17-2019-Loss-of-Control-in-Homebuilts-Program-Video https://www.eaa.org/eaa/news-and-publications/eaa-news-and-a...
    - mikeash 8y ago
      Climbs after takeoff are a situation where they will significantly differ, and also one of the times when this information is more important. Attitude indicator? Look out the window! Stall horn? Just feel the pre-stall rumbling through the controls. You can fly a plane with no instruments. None of them are strictly necessary, but it’s a good idea to have them.
cjbprime 8y ago
> everyone how AoA is one of the most important metrics wrt flying an airplane Pretty difficult argument to make when most planes do not have AoA sensors!
- astrodust 8y ago
  The "sensor" is often the pilot.
- DamnYuppie 8y ago
  I believe he means jets, which I believe all of them do.
  - AdrianB1 8y ago
    He does not. Let's read as it is written.
- briandear 8y ago
  Almost all new airplanes have them. The Skyhawk got one as standard equipment in 2016. Here’s a thesis on the topic: https://kb.osu.edu/bitstream/handle/1811/68634/1/AbramsHonorsThesis.pdf https://kb.osu.edu/bitstream/handle/1811/68634/1/AbramsHonor...
  - cjbprime 8y ago
    Sure, but almost no-one flies brand new airplanes. What percentage of GA flights do you guess contain an AoA display? And the argument's supposed to be that they're a most important indicator for airplanes?
- mikeash 8y ago
  And yet it’s absolutely true. Note that many light aircraft have stall warning horns, which are just AoA sensors that only detect when the AoA exceeds a certain amount. In many other planes, you can detect excessive AoA by sound or feel.
AdrianB1 8y ago
I am qualified to fly several types of small planes, none has an AoA. I was able to fly with a faulty Pitot reading (airspeed), but I would not do it often; I had never felt the need for an AoA sensor, not even when I was flying in "unusual attitudes" (intentionally).
- 0xfaded 8y ago
  My second ever solo my airspeed indicator froze :)

mikeash 8y ago

Airspeed is mostly, although not entirely, important as a proxy for angle of attack.

dsfyu404ed 8y ago

But you don't need a dedicated sensor for it. The artificial horizon does that job too. Edit: To be more clear, the artificial horizon combined with other sources of information available to the pilot (airspeed, stall indicator) provide the pilot with the same level of situational awareness as knowing his/her AOA outright from a dedicated sensor.

danaliv 8y ago
The artificial horizon doesn't indicate angle of attack. Please see this comment: https://news.ycombinator.com/item?id=19638250 https://news.ycombinator.com/item?id=19638250 Or consider an aerobatic airplane at the first vertical point in a loop. The airplane's pitch is 90° but the angle of attack is less than 10°.
- dsfyu404ed 8y ago
  You're right but the vast majority of the time the difference between the AI and the AOA is close to zero (plus whatever the angle of the wing is relative to the fuselage which is fixed and should be pretty small anyway). The times when the difference between the AOA and the AI is very different than zero in a bad way the little stall switch on the wing and some sort of chime/buzzer will be more than happy to let the pilot know. My point is that the AI combined with the little stall switch on the wing seem to be good enough for the overwhelming majority of cases. Add in airspeed and you're more than covered. We keep trying to add systems to cover whatever remaining edge cases we find but those systems have failure modes too so we take three steps forward and two steps back. These systems pick up the slack when the pilot might be inattentive but the increased complexity and cognitive load poses other risks.
  - lutorm 8y ago
    Loss of control during approach and landing because of poor airspeed control kills pilots every year. It's important enough that the EAA has a dedicated "loss of control initiative" to try to figure out what to do. See for example https://www.eaa.org/eaa/news-and-publications/eaa-news-and-aviation-news/news/01-17-2019-Loss-of-Control-in-Homebuilts-Program-Video https://www.eaa.org/eaa/news-and-publications/eaa-news-and-a...
  - mikeash 8y ago
    Climbs after takeoff are a situation where they will significantly differ, and also one of the times when this information is more important. Attitude indicator? Look out the window! Stall horn? Just feel the pre-stall rumbling through the controls. You can fly a plane with no instruments. None of them are strictly necessary, but it’s a good idea to have them.

cjbprime 8y ago

> everyone how AoA is one of the most important metrics wrt flying an airplane Pretty difficult argument to make when most planes do not have AoA sensors!

astrodust 8y ago
The "sensor" is often the pilot.
DamnYuppie 8y ago
I believe he means jets, which I believe all of them do.
- AdrianB1 8y ago
  He does not. Let's read as it is written.
briandear 8y ago
Almost all new airplanes have them. The Skyhawk got one as standard equipment in 2016. Here’s a thesis on the topic: https://kb.osu.edu/bitstream/handle/1811/68634/1/AbramsHonorsThesis.pdf https://kb.osu.edu/bitstream/handle/1811/68634/1/AbramsHonor...
- cjbprime 8y ago
  Sure, but almost no-one flies brand new airplanes. What percentage of GA flights do you guess contain an AoA display? And the argument's supposed to be that they're a most important indicator for airplanes?
mikeash 8y ago
And yet it’s absolutely true. Note that many light aircraft have stall warning horns, which are just AoA sensors that only detect when the AoA exceeds a certain amount. In many other planes, you can detect excessive AoA by sound or feel.

AdrianB1 8y ago

I am qualified to fly several types of small planes, none has an AoA. I was able to fly with a faulty Pitot reading (airspeed), but I would not do it often; I had never felt the need for an AoA sensor, not even when I was flying in "unusual attitudes" (intentionally).

0xfaded 8y ago
My second ever solo my airspeed indicator froze :)