Hacker News Reader

Comment by WalterBright | Hacker News Reader

> nobody should be flying an airplane like this so close to the edge the exact stall speed needs to be known numerically within one knot.

An experienced pilot can feel the stall coming on with a bit of a "burble" in the stick.

My dad (fighter pilot) told me that knowing exactly where the stall point is is life and death. When you're in a dogfight, the winner often is the one that can turn inside the other. Turning as tight as you can requires getting exactly on that edge of the burble.

It's the same thing as in automobile and motorcycle racing. How close you can get to a slide without sliding is the difference between victory and ignominy.

View on HN

> An experienced pilot can feel the stall coming on with a bit of a "burble" in the stick.

Without any disrespect to the flying abilities of your Dad, as an aerospace engineer, the short answer to that is "no".

You will have the luck to feel a "burble" if the airplane has been been built to be give you that warning. You have absolutely no guarantee that once the airplane has been modified beyond its original configuration, you will get any form of warning. This extreme behavior is actually partly present in the current case, with the stalling point jumping from the wing tip immediately to the wing root. That's no good.

It can be even worse if you're flying a plane that is licensed under the "experimental" category by the FAA. One of the preferred airfoil for some time was the NACA 5-series, as it can have very little lift-induced pitching moment. It has also criminal stalling characteristics with absolutely no warning. Something beautifully illustrated by the following lift polar:

https://media.cheggcdn.com/media/76b/76b33250-7f26-41f6-8f2c...

Is it possible there's a mechanical/design cutoff where most planes designed to be fully mechanical would feel the "burble" while a more modern plane would not, similar to ABS vs non-ABS brakes or powersteering vs none? Are there hydraulic assists for flight controls that might smooth out those mechanical tells?

Not necessarily, no.

It's a design feature to give pilots an advanced, physical warning that they are about to stall, and fall out of the sky. Electronic systems are all nice an well, but they can fail. So why not simply make it a physical feature of your airplane design, that triggers reliably not matter what?

In some very specific edge cases a designer might decided that the planform trade-offs needed to bake the feature into the wing is not worth the performance loss in other metrics, and might forgo a nice, buffeting pre-stall wing. But plenty of pilots have died because they unexpectedly stalled, so it is not a design decision that should be taken lightly.

> You will have the luck to feel a "burble" if the airplane has been been built to be give you that warning.

Airplanes which are designed to do this (most airplanes) do it very reliably, it's not luck. Several of the Citabrias I fly don't have stall horns, all I have is the buffet.

Complexity is always a tradeoff: it's harder to fuck up building and/or repairing a simpler airfoil.

> Several of the Citabrias I fly don't have stall horns, all I have is the buffet.

That's fine, as long as the airfoil and wing planform you chose have a forgiving-enough lift vs angle-of-attack curve that you get plenty of buffeting before you start loosing significant lift and fall out of the sky.

> Airplanes which are designed to do this (most airplanes) do it very reliably

Yes, this is by design. Enough pilots were killed because their planes were not doing this reliably, and they literally fell out of the sky.

Sure, that's why I said "airplane like this": in car terms, the plane we're talking about here is a minivan.

Imagine dogfighting in a Cessna! I imagine the arms to be pilot wielded colt 45s and first officer to be a jug of whiskey.

Love this description lol

One of the last aircraft shot down in the European theater of WWII was a Piper Cub that shot down a Fieseler Storch with a .45 pistol. They landed next to the crashed Storch, captured the pilot, and treated his injuries. Then handed him over to the Russians, who I am sure also treated him in accordance with the provisions of the Geneva convention.

https://theaviationgeekclub.com/that-time-a-usaaf-piper-l-4h...

Perhaps in accordance with the spirit, but the Geneva convention was in 1949, so those provisions didn't exist yet.

There were several Geneva Conventions prior to the 1949 one; the "Convention relative to the Treatment of Prisoners of War" was signed in 1929.

https://ihl-databases.icrc.org/en/ihl-treaties/gc-pow-1929

The current Geneva Convention was in 1949, but the original Geneva Convention dates back to 1864.

Of course, the previous poster is noting that the USSR blithely disregarded the conventions for others' POWs as well as its own: most returning soldiers were considered traitors to the Motherland and summarily executed or sent to the Gulag to die more slowly.

if you like that idea and science fiction, see the second book in the Greatwinter trilogy by Sean McMullen (read them in order, though)

https://en.wikipedia.org/wiki/Cessna_A-37_Dragonfly

https://en.wikipedia.org/wiki/Cessna_O-2_Skymaster

https://www.airforce-technology.com/projects/ac-208-combat-c...

> An experienced pilot can feel the stall coming on with a bit of a "burble" in the stick

Stall recovery has also been an essential part of my flight training.

Although can you recover at a height 15m above terrain?

. . . probably not, but does that mean you never practice? Most stall/spin incidents occur at low altitude, but not THAT low. It's often pilot inattention in the landing pattern.

I agree! IANAP though.

Also in this case I suspect they needed to learn proper takeoff procedure. Since you can’t practice dying more than once the mitigation has to be avoidance (in addition to the stall practice you mentioned)

Technically, power-on stalls are supposed to teach how to recover from bad technique on takeoff/go-around and power-off stalls are supposed to teach how to recover from bad technique in the landing pattern.

In reality, they're both training-wheels versions of how to deal with any departure from controlled flight, which is why any professional pilot worth their salt should have a decent grounding in aerobatics and some spin/departure/out-of-control flight experience.

-Am (or at least was) a pilot . . . I could jump in and fly a bugsmasher today if I really needed to, just not legally without a doc visit and a checkride.

The most dangerous situations are when you're flying low and slow like before a landing though, when there's often no time for recovery (especially when you end up in a spin due to asymmetric stall). When I was flying I always worried about this too the point of approaching too fast. But I never finished my PPL anyway

Not really, as to your final point; the race driver’s skill is not in avoiding the slide, but — with the mechanic’s help — finding it, and using it. Recall: loose is fast, and on the edge of out of control.

Reply on news.ycombinator.com