Stall speed is a misnomer.

Stalls occur due to exceeding the critical angle of attack and can happen at ANY speed.

Whoever is downvoting this: Stop. It's the key point here. Planes don't need to know their weight to produce a stall warning; AoA is a great metric, and GA planes not having an indicator or warning based on it is astonishing.

I thought the point was predicting a stall by knowing the approach speed will be so low that you will stall, not detecting a stall just before it happens

You can't control the weather, if there's a micro burst during landing you are in trouble.

GA planes have a stall warning horn (based on AoA). They just generally don't have a AoA indicator (though that might be a good idea indeed), relying on indicated airspeed instead, which (for given airplane mass) has a one-to-one [1] mapping to AoA in unaccelerated flight. That's why the concept of stall speed exists.

That is the case since, in unaccelerated flight, we need weight == lift, so

   W := m g == L := 1/2 rho v^2 c_L S

with m = mass, g = earth gravitational acceleration, 1/2 rho v^2 = fluid dynamic pressure which is measured by the pitot tube and displayed as indicated airspeed (well, a function of it), c_L = the coefficient of lift, and S = wing area.

Now, weight is constant (for given airplane mass, in unaccelerated flight), and so is the wing area. The coefficient of lift depends on the AoA, and dynamic pressure has a monotonic one-to-one relationship to IAS. Thus you have the relationship between IAS and AoA.

[1] Unless you get to "the back of the power curve" (the coefficient of lift increases with AoA, then decreases again, until it drops off in a stall). Let's not go there.

I think that was his point. To calculate if you are going to stall in a final, you need to know your weight and flap setting to see if you will exceed the critical angle of attack when doing the turn, exactly because the speed isn’t constant.

No, you just need an angle of attack sensor. These are increasingly available for small GA planes.

stall AoA depends on flaps though?

Yes, and some sensors do take flaps position into account (or you compromise and have it display the AoA with a typical approach setting).

You need an AoA sensor to see if you are currently stalling or are just about to stall. To predict if you will stall at a specific point in your approach before you’re there, you need to know your weight, too.

it's a misnomer but airspeed is life. we're not talking about people stalling during air combat or aerobatics, we're talking about doing it in the pattern. simply keeping your speed up and knowing the speed you will stall at based on bank angle should be enough.

> But again, it's not that we can't do those things, it's just that they're completely cost prohibitive.

Isn’t this what the OP is referring to when he says the current market can’t support the necessary innovation? As I understand it the idea here is to expand the market and spread certification costs out over more planes.

I don't think he can get the required certifications and charge a reasonable price for this plane. There are not enough people interested in a personal airplane at any price to support the costs to bring a new one in the air. You can rebuild all current airplane's (most built before 1980) for much less than the costs to certify a modern replacement, and only then can you start asking what it costs to build that replacement. Which is why we rebuild old airplanes all the time - it is wouldn't pass modern regulations but since it already exists it is certified.

There's an interesting dynamic here--we (the industry today) are more okay with flying rickety airplanes from the 70s before flying something built with more modern engineering and production techniques.

> As I understand it the idea here is to expand the market and spread certification costs out over more planes.

exactly.

> There are not enough people interested in a personal airplane at any price to support the costs to bring a new one in the air.

our thesis is that this isn't true. we've seen glimpses of this in the past 10 years that haven't been successful, but have shown that there is a wave of people who would get into GA if it were safer and more affordable. our mission to make it so, and the Airhart Sling is just the first step

> There's an interesting dynamic here--we (the industry today) are more okay with flying rickety airplanes from the 70s before flying something built with more modern engineering and production techniques.

Any insights on why that is? My gut feeling is that it’s some combination of cost (there’s still a huge glut of old and cheap planes that basically work fine) and skepticism towards new, less proven models and technologies (i.e. the perception of Cirrus changed very slowly over a decade plus to where now the chute is generally accepted to be a good thing to have).

I think there's definitely a "tried and true" and "if it aint broke don't fix it" mentality. Combine that with the fear of trying something new in the face of the FAA and regulatory barrier, many will say it's better to just take the risk on older stuff than make something new and better

I'm not wishing you bad luck, but I remain pessimistic about your ability to get something certified and charge a reasonable price.