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The unstallable plane that stalled

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Re: The unstallable plane that stalled

#101

Post by jcalvinowens »

WalterBright wrote: post #68
jcalvinowens wrote: post #17

It is not necessary to empirically determine a specific airplane's stall speed in order to operate it safely. It's not required in the US, we just use the number the manufacturer publishes. It's normal for airplanes of the same model to fly differently: I fly a little fleet of six Citabrias, and their stall characteristics are radically different. You'd expect more uniformity from a modern aluminum airplane, but stil…

> 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…

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

Re: The unstallable plane that stalled

#102

Post by SR2Z »

sokoloff wrote: post #88
jcalvinowens wrote: post #17

It is not necessary to empirically determine a specific airplane's stall speed in order to operate it safely. It's not required in the US, we just use the number the manufacturer publishes. It's normal for airplanes of the same model to fly differently: I fly a little fleet of six Citabrias, and their stall characteristics are radically different. You'd expect more uniformity from a modern aluminum airplane, but stil…

> 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 Citabria's are often flown in aerobatics (Citabria backwards is airbatic and for a while, they were the only aerobatic aircraft being commercially manufactured in the US) and a lot of aerobatic maneuvers involve stalling the wing.

Yes, but anyone doing aerobatics so close to the ground that they can't recover from a stall is understood to be doing that at their own risk.

Anyone doing the above with unfavorable wind has a death wish.

Re: The unstallable plane that stalled

#103

Post by roywiggins »

VS1999 wrote: post #43
roywiggins wrote: post #33

Earlier quoted context omitted.

Everyone ends up paying for that, in the form of insurance rates.

And healthcare insurance if you live in the US, and regardless of where you live it clogs up your entire healthcare system as Jimmy-no-seatbelt flies into the trauma center.

In countries with universal healthcare you pay too, it's just called "taxes" instead.

Re: The unstallable plane that stalled

#104

Post by roywiggins »

lettergram wrote: post #40
roywiggins wrote: post #33

Earlier quoted context omitted.

Everyone ends up paying for that, in the form of insurance rates.

They could just not cover injuries where a seatbelt isn’t warn. That said, we have evidence that seatbelt wearing didn’t impact insurance rates. Literally look at the rates over time, even after these laws were enacting, insurance rates rose fast as ever

That's not how emergency room care works. It doesn't matter whether it's covered or not, you're going to get treated; quite likely the hospital ends up eating the bill if insurance doesn't pay.

Re: The unstallable plane that stalled

#105

Post by jcalvinowens »

sokoloff wrote: post #88
jcalvinowens wrote: post #17

It is not necessary to empirically determine a specific airplane's stall speed in order to operate it safely. It's not required in the US, we just use the number the manufacturer publishes. It's normal for airplanes of the same model to fly differently: I fly a little fleet of six Citabrias, and their stall characteristics are radically different. You'd expect more uniformity from a modern aluminum airplane, but stil…

> 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 Citabria's are often flown in aerobatics (Citabria backwards is airbatic and for a while, they were the only aerobatic aircraft being commercially manufactured in the US) and a lot of aerobatic maneuvers involve stalling the wing.

You don't really look at the airspeed indicator for that, you feel the stall in the reversible controls. That feel is incredibly precise.

Re: The unstallable plane that stalled

#106

Post by buildsjets »

peteradio wrote: post #70
WalterBright wrote: post #68

Earlier quoted context omitted.

> 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…

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

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...

Re: The unstallable plane that stalled

#107

Post by buildsjets »

andoando wrote: post #76
the__alchemist wrote: post #24

Soapbox: Stall speed is an approximation. It's baffling that GA aircraft don't have one of the most safety-critical measurements: AOA. Stall airspeed varies with a number of factors; this includes the mods described in the article, and weight change from burning fuel, passengers, payload etc. AOA is more invariant to that as a metric for choosing stall speed, speed down final etc.

But we got a nice tea kettle whistle to tell us were about to die.

I've always thought it sounded like a kazoo. Or sometimes a harmonica.

But I like the imagery of a a little tea kettle on a hob under the panel.

Re: The unstallable plane that stalled

#108

Post by howard941 »

buildsjets wrote: post #94

I've been involved in general aviation since the late 1970s, currently commercial/twin/instrument rated, have a degree in aerospace engineering, and do what my username says for a living. So I know airplanes, and why they do the things they do. But an appreciation for what is physically occurring during a stall, how the resulting balance of forces influence the aircraft handling during a stall and recovery, and why t…

> instead of recovering as soon as you heard the horn blip, you spent a lot of time with it going off in your ear. In fact my instructor used to pull the circuit breaker for it after it went off, as we already knew we were going to be spending a lot of time in an incipient stall condition, and could tell more from the changes in sound of the air going past us than some buzzer.

This is sort of the way I was taught. In primary training we'd always wind up doing a lot of minimum controllable airspeed work and then move on to power on stalls/departures and low power stalls/approaches. Recognition was pretty easy with the buffeting followed by the nose dropping. Coordination and control were the goals. Later on we'd also do accelerated stalls. I hated doing low speed work so my instructor made us do it every time even after I started doing them without him in the airplane.

Re: The unstallable plane that stalled

#109

Post by avianlyric »

dramm wrote: post #59
macintux wrote: post #26

Earlier quoted context omitted.

I'll admit to complete and total ignorance, but: > ...we just use the number the manufacturer publishes. From the article it sounds like this plane was radically modified, to the point where the manufacturer's stall speed would be irrelevant. Why wouldn't you want to confirm for yourself where the speed is after so many changes?

Radical has all the wrong implications. It's a "major alteration" in a regulatory sense, done from an approved kit of parts, with a very well documented installation and post-installation operation and maintenance procedures. The aircraft was modified with a Robertson STOL kit. A common type of modification to make to a "bush aircraft". In the USA the modification is covered by an STC (Supplemental Type Certificate),…

As noted in the article, the plane had been modified with far more than just the STOL kit.

> A further issue was that his Cessna 185 had been extensively modified. The addition of floats, cargo pack, short take-off and landing kit and a three-blade propeller had never had their combined effect documented.

That’s a lot of things that modify the flight characteristics of a plane, all interacting together in what seems to be a previously untested configuration.

I can completely see how each individual modification might modify the planes flight characteristics in a well know manner. But I struggle to see how anyone could realistically predict the result of all the modifications without some basic empirical testing.

Re: The unstallable plane that stalled

#110

Post by KolmogorovComp »

dghlsakjg wrote: post #52
macintux wrote: post #26

Earlier quoted context omitted.

I'll admit to complete and total ignorance, but: > ...we just use the number the manufacturer publishes. From the article it sounds like this plane was radically modified, to the point where the manufacturer's stall speed would be irrelevant. Why wouldn't you want to confirm for yourself where the speed is after so many changes?

Stall speed depends on so many factors that it can change significantly in a single flight. Weight, altitude, density altitude, angle of attack etc. are all going to have an effect. In other words, sure, you might want to confirm it, but you should also give yourself some margin since you don’t ever really know what the stall speed is until you stall.

> angle of attack etc

This is wrong.

The angle of attack is not a parameter of the stall speed, it is the cause of the stall (for a given configuration, assuming well below transonic speed). This is why for example, for precise handling you should use an angle-of-attack indicator (a large majority of fighter jets and more generally military aicraft have it).

> you should also give yourself some margin since you don’t ever really know what the stall speed is until you stall

The manufacter speed already take into account the afore-mentioned parameters into account, and the resulting speed is the worst case scenario, if not told otherwise (usually max weight, max forward CG).

One should not fly with an arbitrary speed margin, but instead use well-known speedq (1.3Vs, 1.45Vs, where Vs=stall speed in the given config) depending on the flight phase, and remember well the bank angle limit associated with them.

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