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The unstallable plane that stalled

fearoflanding.com

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Re: The unstallable plane that stalled

#51

Post by t0mas88 »

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…

European pilot here :) it's also not a European thing. It works the same here as it does in the US, you use the published number in the flight manual.

But this plane had significant modifications done. And if you do things that significantly change performance, you'll need to get updated performance data. Or the provider of the supplemental type certificate that allows the modification has to provide an updated flight manual with that data.

Re: The unstallable plane that stalled

#52

Post by dghlsakjg »

macintux wrote: post #26
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…

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.

Re: The unstallable plane that stalled

#53

Post by ultrarunner »

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.

Soapbox next to your soapbox: GA planes are old specifically because of the FAA and their overly restrictive regulations. The cost involved to create an AoA sensor & readout is minimal and at least one company has done it with an IMU only. The cost to certify, sell, and install an AoA sensor (in terms of both money and time waiting to get on the schedule of an FAA-blessed installer) is more than most people find it to be worth. Food for thought: this also applies to shoulder harnesses in many cases.

Aviation could be cheaper, safer, and better in general if the FAA was not stuck in the 60s.

Re: The unstallable plane that stalled

#54

Post by Waterluvian »

roywiggins wrote: post #33
lettergram wrote: post #10

Earlier quoted context omitted.

My reflex is to never mandate safety procedures. To put it simply, why should the state use force to mandate something like safety. The implication being if someone refuses the force of the state is used on them… which is definitely not good or improving safety. Mandating the seatbelts exist, sure. Mandating people wear them? Idk about that. In the case of tractors for instance, wearing a seatbelt is downright danger…

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

Not only that but I think there’s also a meaningful quality to living in a society with excessive avoidable deaths. I personally think it contributes to a “shields up, guard up” culture that I’ve experienced and found exhausting.

Re: The unstallable plane that stalled

#55

Post by t0mas88 »

hinkley wrote: post #36
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…

Decreases the stall speed? How does that work?

The published speed is at maximum takeoff weight, with the most unfavourable center of gravity (usually most forward) and idle power

If the conditions are better (not at max weight, rear center of gravity, engine power adding more airflow over the wings) you can fly below the published stall speed number.

Re: The unstallable plane that stalled

#56

Post by fallingknife »

_trampeltier wrote: post #7
BalinKing wrote: post #4

Earlier quoted context omitted.

Indeed, passengers inflating their life jackets too early directly caused many of the deaths on Ethiopian Airlines Flight 961 [0]. This is why the modern safety briefing includes the bit about waiting until you've exited the cabin to inflate your life jacket. I have no clue how this applies to floatplanes, though—I'm curious for more details about when the article says "there are approved life jackets which could be…

"Many of the passengers survived the initial crash, but they had disregarded, did not understand, or did not hear Leul's warning not to inflate their life jackets inside the aircraft, causing them to be pushed against the ceiling of the fuselage by the inflated life jackets when water flooded in. Unable to escape, they drowned."

That seems strange to me. Why would they not simply take off the life jacket and swim out?

Re: The unstallable plane that stalled

#57

Post by Waterluvian »

fallingknife wrote: post #56
_trampeltier wrote: post #7

Earlier quoted context omitted.

"Many of the passengers survived the initial crash, but they had disregarded, did not understand, or did not hear Leul's warning not to inflate their life jackets inside the aircraft, causing them to be pushed against the ceiling of the fuselage by the inflated life jackets when water flooded in. Unable to escape, they drowned."

That seems strange to me. Why would they not simply take off the life jacket and swim out?

The inflatable ones are often designed to be impossible to remove… at least not easily. They inflate into a thing that’s kind of gently choking you.

Re: The unstallable plane that stalled

#58

Post by BruinsInSeven »

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.

How do you determine a margin without some form of a baseline?

Re: The unstallable plane that stalled

#59

Post by dramm »

macintux wrote: post #26
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…

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), the installation needs to be supervised and approved by an A&P technician with IA (Inspection Authority). The STC will modify the airspeed indicator markings, including the stall speed markings (bottom of green and white arcs), and modify the approved flight manual/pilot operating handbook and maintenance documentation for the aircraft. Since this is a major alteration (in a 14CFR regulatory sense) that modifies the flight characteristics of the aircraft it needs to be test flown after the work, and the STC will also separately requires this. I expect/hope the STC includes instructions for checking stall characteristics including airspeed. In European countries a similar level of regulation/documentation is followed based on the USA STC.

Give the description of the pilot's sad lack of understanding of basic operation of the aircraft I am doubting they even read the pilot operating handbook.

Re: The unstallable plane that stalled

#60

Post by t0mas88 »

H8crilA wrote: post #9

Just so we're clear, there's practically no such thing as an "unstallable plane". If some pilot believes that then their license should be revoked. Even jet engines can experience stalls internally on the compressor blades, and even helicopters can experience stalls on their retreating blade. I would compare it to someone believing that their car cannot possibly lose traction. Exceptions, which of course must exist,…

Very bad modification. And wrong (but natural) response from the pilot trying to pick up the dropping wing with aileron input. That would have made the asymmetric stall worse.
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