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 still: 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.
The 40lbs of gas I burn flying for an hour decreases the stall speed by more than 1mph on those Citabrias I fly.
EDIT: I was mistaken, this isn't a requirement in Europe either.
> 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.
> 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:
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.
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.
My understanding is that in the US, part of the modification would be updating the plane's official operating limitations, and there could be a new stall number. Still a number from the manufacturer, not a number empirically determined by testing that specific airplane. For special one-off modifications, I don't know: I've always been told that's almost impossible with certified airplanes.
One Citabria I've flown had vortex generators installed on the leading edge of the wings, but the club sold it over a year ago and I don't remember if it listed a modified stall speed. I do remember it said "not airworthy if more than N of the VGs are broken off", I think it was three?
The plane had a cargo pack and a Robertson STOL. Cargo packs are essentially for bush planes and as an example, the 1975 Skywagon’s owners manual even had one diagrammed. Robertson STOL’s are extremely common in Northern Canada to the point that even as a passenger I know about them.
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.
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.
I'm not a pilot or an aviation expert, but I think you're arguing against a strawman here. The investigation report said nothing about determining the precise stall speed, it just recommended "that pilots be informed about the stall behaviour of the Robertson short take-off and landing kit on the Cessna 185 aircraft, both by listing the issue in the aircraft flight manual supplement and through education through the aviation authority". The fact that the stall speeds were not listed on the test flight report was just further proof that the pilot didn't actually test the stall behaviour of the aircraft.
What the investigation report also didn't mention is that pilots should actually practice stall recovery and not just think "if I believe strongly enough that my plane is unstallable, I can ignore stall recovery". But that probably goes without saying...
> It's normal for airplanes of the same model to fly differently
In my experience any equipment this large is effectively handmade, with all the variability implied by this. I'd hope aircraft are made to tighter tolerances than the stuff I work with but a couple of millimeters is often enough to have a noticeable effect on things like actuator travel.
> 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.
This is exactly my takeaway as well. Rather than trying to determine the characteristics of the machine to the n'th degree, assume a realistic degree of variation and design for it accordingly.
> 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 is not necessary as in "there is no legal obligation", true.
But if you want to live, it is absolutely necessary. The numbers provided by the manufacturer will tell you absolutely nothing about the stalling characteristics of the airplane as soon as you start modifying it.
The non-linearity of the phenomena involved in stalling also mean that "intuition" and "small changes" will be of absolutely not help to determine by how much you changed the characteristics of your airplane.
> 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.
Things that can influence stall speed include weight, power, center of gravity, flaps/landing gear configuration, and more.
Why? Well, stall speed isn't a real thing. There isn't a speed at which you stall, that's not how it works. It's a convenient short-hand that we use for the more complicated reality. The physical reality is that stalls happen at a particular angle of attack (AOA) into the apparent wind. That is, the angle of your wings relative to the airflow. Up to the critical angle a higher AOA means more lift to counteract gravity. As you slow down you generate less lift because there's less airflow over the wings. So as you slow down, in order to generate a similar amount of lift you have to increase your AOA. If you keep slowing down and adjusting your AOA to compensate, you'll reach a speed that's low enough and therefore AOA high enough that adding more AOA no longer adds more lift (the air no longer flows smoothly over the wing). That's the stall speed, the speed at which more AOA no longer generates more lift. But it's the AOA that's the problem, not the airspeed.
In addition to lower speeds needing more AOA, you also need a higher AOA if you weigh more. A wrong but illustrative way to think about it might be that you need the engine's thrust pointed more towards the ground the more you weigh. That means that as you burn fuel (lose weight) the AOA that will stall you doesn't change, but the excess AOA available due to your weight-change does so in effect the air speed at which you would be near the critical AOA to stay airborn does change.
Stall speed is still a useful concept especially while landing but it's misleading outside of landing and when anything else is remotely unusual like weight or modifications to the plane. For this reason the FAA has been trying to get AOA indicators installed in planes and to train pilots to look at those instead of thinking about stall speeds https://www.faa.gov/sites/faa.gov/files/2022-01/Angle%20of%2...
Useful to think of the airplane as standing still while the engine accelerates the air around it. To fly, you need the air to move over the wings quickly and in the right direction.
You can sort of trade how fast you need the air to go for how ideally the air is flowing over the wings. If you angle the wings just right against the air flow, and/or you bend them out of shape just right with flaps, you can slow down a lot while relying on the air itself to carry your plane. If you're flying against the airflow, you need to go faster.
This is usually done during take off and landing. The pilot lowers the flaps when approaching to land and flares the aircraft before touchdown, all to make the air flow efficiently into the wings, thereby allowing the aircraft to slow down without falling straight down like a stone.
That's why weather is so important for flights. Pilots need to be ready to call TOGA and go maximum thrust at a moment's notice just in case some crosswind or heat wave or something screws up the direction of the air flow just as they're about to land. Many an admiral cloudberg article has been written due to that sort of thing. You angle the plane just right, slow it down just to the edge of stalling, then some phenomenon happens and increases your stall speed past your current speed...
The Robertson STOL mod droops the ailerons with flaps, changing the effective angle of incidence of the wing. A friend had a Robinson-equipped 182 and we could quite comfortably operate in/out of Marlboro Airport (1650' paved with trees at one end and a fence at the other).
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.
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.
I was very skeptical of this until I had the chance to fly one of those brand-new C172 models that come equipped with 'em. They're so convenient!
Sure, ye olde haptic feedback + inner ear + stall horn/shaker combo has always worked for me—but if you are a new or overwhelmed or complacent or unlucky pilot, having a big angry indicator sitting atop the glare shield furiously (visually & audibly) informing you of the approaching cross-control stall that is about to bury you in your base-to-final grave makes danger IMPOSSIBLE to miss.
The LEDs were bright enough to be clearly visible even under direct sun, but the Geiger-esque clicking and chattering increasing in urgency as I approached critical AoA made it for me. No need to put your head down or even alter your scan to include it: you can hear trouble coming!
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.
I don't think that's completely true. There is a combination of market size and regulatory burden; not a lot of people are buying GA aircraft (compared to say, the number of people buying iPhones), so there isn't an enormous financial incentive to get people out of their C172 or Bonanza.
I also think that these old airplanes are really ships of theseus. Maybe there are some original stickers and seats, but that's about it. Safety and avionics upgrades on these old airframes are definitely in the financial reach of many readers of this forum, and I'm sure many people are flying "old" airplanes that have AoA sensors and IFR-certified glass panels and backups. Day to day they probably feel a lot like airline pilots.
The FAA is stuck in the 60's because there is a massive industry supporting the ancient technologies in general aviation.
Modern stuff, like you point out, is far more reliable, cheaper, lower power consumption, and more functional. That better reliability means less need for aircraft mechanics and avionics shops.
Nobody would want their discreet component transponder overhauled if it could be replaced with a cheaper unit that uses modern wizardry like logic chips or even (gasp) a microcontroller.
Ditto for leaded fuel air cooled piston engines with manual mixture controls that require teardowns all the time. That bullshit is only still around because Continental and Lycoming want it to.
My favorite anecdote I heard of from a flight instructor is that of a cargo plane taking off that had some heavy vehicle tied down in its hold. It broke free of its straps during takeoff and rolled to the back of the aircraft, which shifted the CG such that the plane entered an unrecoverable stall and crashed.
There is a video which makes its way around the Internet regularly of this crash[1] which was attributed to exactly that, killing all seven on board. (Which makes it pretty heavy for an anecdote, admittedly.)
> Stall speed is an approximation. It's baffling that GA aircraft don't have one of the most safety-critical measurements: AOA.
All aircraft equipped with a six pack, you have an artificial horizon indicator which can tell you what is your angle of attack. And Cessna's have them in all planes, even 50-60 years old ones.
The angle of attack is the angle between the chord line of the wing and the oncoming air (or relative wind). This is distinct from what the artificial horizon measures. The artificial horizon is concerned with the aircraft's orientation relative to the gravitational pull of the Earth, indicating whether the nose of the aircraft is above or below the horizon and how much the wings are tilted relative to the horizon.
Artificial horizon is not a reliable indicator of angle of attack.
I’ve been thinking that now that we have glass cockpits the airspeed indicator could automatically reflect the current stall speed under all conditions. I.e. green arc could shrink in a steep turn, etc.
To add to what Toutouxc said, stalls are a fairly routine training/familiarization maneuver in most light aircraft. The typical recovery is just to push forward on the stick/yoke. A manual[0] I found with a web search claims a Cessna 185 on floats may require up to 200 feet to recover.
Stalling one wing but not the other usually results in a spin, for which recovery requires both breaking the stall and stopping the rotation. The ailerons, located near the wingtips are not effective (or even counterproductive) during a spin because air is not flowing smoothly over the stalled wing; the rudder, located on the tail is used to stop the rotation. This usually requires more altitude for recovery.
If you stall one wing but not the other at an altitude of 15 meters (49 feet), it's very likely you're going to contact the surface in a manner you did not intend. Inappropriate control inputs, such as trying to correct the resulting bank using the ailerons guarantee it. It's still a good idea to attempt to recover rather than sit still and pray because a more controlled impact is usually more survivable.
You decrease the angle of attack, i.e. you let the nose drop a bit. When the stall has fully developed into a spin, you perform the spin recovery procedure for your aircraft. Hopefully you still have some altitude left.
Non sequitur from non-pilot: I was once in Duluth, MN in the bitter cold and watched a Cessna with skis (for landing on the frozen lakes of the Boundary Waters) land at the airport. It was the utterly bewildering to see how slowly it was going in the air. And how little distance it took to stop. Short Landing Kit I assume. I've seen ducks and geese come into land on lakes at higher speeds!
"According to the operating handbook, the An-2 has no stall speed. A note from the pilot's handbook reads: "If the engine quits in instrument conditions or at night, the pilot should pull the control column full aft and keep the wings level. The leading-edge slats will snap out at about 64 km/h (40 mph) and when the airplane slows to a forward speed of about 40 km/h (25 mph), the airplane will sink at about a parachute descent rate until the aircraft hits the ground." As such, pilots of the An-2 have stated that they are capable of flying the aircraft in full control at 48 km/h (30 mph) ... This slow stall speed makes it possible for the aircraft to fly backwards relative to the ground: if the aircraft is pointed into a headwind of roughly 56 km/h (35 mph), it will travel backwards at 8 km/h (5 mph) whilst under full control."
I once got to ride in an An-2 on a tourist sightseeing flight. I've always remembered the sense that the pilot didn't even bother to line up with the runway ahead of time when landing, but simply took a gentle turn onto it upon reaching it, at roughly the speed of a car.
I'm sure this is a slight exaggeration in my memory, but it really was able to fly incredibly slowly and take turns in an incredibly short distance.
I have been a passenger in a C-170 with a STOL kit that flew backwards over a beach on the Washington coast. We landed well behind where we took off. The takeoff and landing were both nearly vertical. Had a steady wind from the ocean.
>“I let it lift off by itself. It was well-trimmed and it lifted off normally by itself.”
It sounds like the pilot wasn't fully prepared and engaged to compensate for propeller torque at the moment the aircraft left the surface of the water. At full takeoff power in a single engine aircraft this can be very intense and jarring, particularly with a high pitch ascent and full prop pitch. All it took was a momentary lapse in keeping the wings level to stall out at that speed.
>The indirect causal factor was the pilot’s lack of experience with stalling the aircraft. He told the investigation that he had never stalled the aircraft, which meant that he was unable to recognise the stall during the take-off.
It's this lack of stick and rudder skills at the root of the incident.
> The pilot had set the trim so that the aircraft would lift off from the step and begin to climb away. The rudder trim was set almost as far right as it could go. The pilot described the take-off as quick and easy. “I let it lift off by itself. It was well-trimmed and it lifted off normally by itself.”
Further down.
> The maintenance team discovered an incorrect right wing geometric twist, which was unrelated to the hangar roof collapse but probably happened during repairs done previously in the USA. As a result, the aircraft had a tendency to roll and had been uncomfortable to fly because of a lack of aileron trim. This might explain why the pilot had the aircraft trimmed full right rudder on take-off: to correct for this roll.
He may have actually had too much rudder. They don’t say this explicitly, but correcting for roll with rudder means you’ll be cross controlled.
He was dangerously near stall speed without realizing it. Some turbulence could cause a small partial stall.
If the airplane was straight, it would have just dropped the nose a bit and corrected. But with a twist in one wing and 2/3 of rudder trim engaged, it’s more like it entered a snap roll. One wing was stalled, one was still making lift.
The airplane felt fine to the pilot, but it was essentially modified to be a snap roll machine. I don’t think a stock 185 would have even been capable of what happened here.
Kind of my point though. The pilot was disengaged from the controls, and relying on trim settings for takeoff. Regardless of the different roll characteristics, if he had been actively controlling the yoke at the time rather than needing a split second to react and correct, the accident probably would not have occurred.
Note that the twist had been repaired before the accident.
> When they repaired the damage to the right wing, they also corrected the geometric twist, removing the aircraft’s tendency to roll.
However, since the repairs were completed five days before the accident, the pilot may have set the rudder based on pre-repair experience with the plane. He may not have been informed of the change in twist, or may not have understood it.
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, include some fly-by-wire setups which limit the actuation of flight surfaces so that it should be theoretically impossible to put an aircraft in that situation, and rumored properties of some abnormal constructions like the An-2. Although even there you should repeatedly get comfortable with what happens in/around a stall, at least in simulators.
The fact that air started to separate and the end of the wing, and not at the root, is scary. It means the pilot wouldn't get the normal warning in the form of airframe shaking. Bad modification.
The main wing can still be stalled in a canard; it’s not easy but it is possible and when it happens it’s almost unrecoverable because the canard will be stalled too and no flying surfaces will have sufficient lift to correct the condition. It’s a condition called “deep stall”
This is far from universally true. The Saab 37 Viggen fighter jet (which was also the first series produced canard aircraft) is capable of departing from controlled flight into a stalled attitude in no less than five different ways, according to its flight manual:
> If the angle of attack exceeds the permitted limits, some yaw disturbances appear around alpha 25-28°, and at alpha 28-30° there are weak pitch-up tendencies. If the stick is moved forward to counter the pitch-up, the aircraft returns to normal alpha, possibly after overshooting up to alpha ~50°. Note that the angle of attack instrument only shows the area -4° to +26°.
> If the stick movement forward at the pitch-up is too small or is made too late, such that the angle of attack does not immediately decrease, the aircraft departs into superstall or spin. If the pitch-up occurs without aileron input, the departure usually results in superstall. If the pitch-up occurs with any aileron input active, the aircraft is affected by adverse yaw and the likelihood of a spin increases.
In addition to the superstall, the aircraft has two spin modes, in the flight manual referred to as flat and oscillating. The difference is basically the rotation speed and if there are oscillations in pitch and/or roll or not. The recovery is pretty conventional:
> In superstall or spin the pitch authority is good, which eases recovery. Aileron input results in adverse yaw, that is to say rolling right gives a yaw to the left and vice versa. Rudder authority is negligible.
> Recovery from superstall and oscillating spin is accomplished by moving the stick to a position somewhat forward of the neutral pitch position, with ailerons and rudder neutral. To recover from a flat spin, the yawing rotation must be stopped first, which is accomplished with neutral pitch and full roll input in the direction of the rotation ("stick into the spin"). When the rotation has just about ceased, recovery is accomplished with neutral ailerons and the stick somewhat forward of neutral, just like when recovering from superstall and oscillating spin.
In addition to regular stalled attitudes though, the aircraft also exhibits another stalled attitude with autorotation, the "plunging spiral" (sv. störtspiral) which can also be encountered in two variants. I'm honestly not sure how exactly it works aerodynamically. The flight manual says:
> In certain adverse dynamic scenarios, the aircraft can enter an uncontrolled attitude of the autorotating type, here called plunging spiral . The plunging spiral, which can be either right side up or inverted, is considered to be the potentially most dangerous form of uncontrolled flight that has been discovered during the spin tests of aircraft 37.
> The most common form of the plunging spiral is the inverted one. The following attitudes/maneuvers repeatably result in an inverted plunging spiral: 1) somersault into inverted position from oscillating spin (for example while attempting to recover from a spin with the stick fully forward), 2) stalling the tailfin through so-called "knife edge flying". The inverted plunging spiral is characterized by: 1) negative load factor (-1 to -3 G) 2), low nose, 3) very high rate of rotation in the roll axis (≥ 200°/s), 4) high sink rate (≥ 150 m/s).
> Moving the stick back and/or aileron input to either side tends to increase the rate of the roll rotation. The rotation can be stopped by moving the stick fully forward with no aileron input. When the rotation has ceased, the stick is moved back to neutral pitch, and the aircraft recovers to controlled flight.
> The aircraft only departed into a non-inverted plunging spiral on a few occasions during the spin tests. It has not been possible to define any repeatable attitude or maneuver that results in a non-inverted plunging spiral. During the spin tests the non-inverted plunging spiral only occurred on the following two occasions (not repeatable): 1) when recovering from an inverted superstall, 2) when recovering from an oscillating non-inverted spin. The non-inverted plunging spiral is characterized by: 1) positive load factor (+1 to +3 G), 2) low nose, 3) very high rate of rotation in the roll axis (≥ 200°/s), 4) high sink rate (≥ 150 m/s).
> In a non-inverted plunging spiral, aileron inputs have no effect. Instead, the roll rotation must be stopped by pulling gently back on the stick until the rotation ceases. When the rotation has ceased, the stick is moved forward to the neutral pitch position and the aircraft recovers into controlled flight.
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.
Over 18k An-2 were produced during the time of 1947-2001. It’s an unusual plane due how old it is and that many are still in operation so general stats should take that into account. It’s well known for being nearly impossible to stall with a stall speed of 30 knots - if it does stall it’ll sink at the rate of a parachute which is still faster than you’d want to hit the ground for a landing. It’s also easy to pick up that speed by dipping the nose. If someone crashes an an-2 by stalling it they had to really work hard to do it. Any pilot that did this would be considered unsafely inept to an almost unimaginable degree.
This article is the first I'm hearing of a Cessna 185 being considered unstallable and I do wonder it that title was picked for engagement. Float planes are extra dangerous with more that can go wrong and less margins for safety.
So many factors that could be blamed in this story. As in every other aircraft accident. But EVERY plane will stall.
THERE IS NO SUCH THING AS AN 'UNSTALLABLE' PLANE.
I once overloaded a plane inadvertently, by having a heavy load plus a full weight of fuel.
At the point of lift-off, the stall-warning started screaming at me as I started to go into the climb. Training kicked in and I pushed the nose down to maintain flying speed. Practically no climb at all possible though. I did a very quick and low circuit, landed and offloaded.
Funny how those little tense moments stay with you for ever. :)
A stall is a loss of lift from an aerofoil due to a high Angle of Attack causing a separation of the airflow from the
aerofoil. No laminar flow = no lift.
There is such an animal as a high-speed stall, where the angle of attack is greater than 15 degrees. Can happen when a gung-ho pilot makes a high speed dive over his girl-friends house and leaves it too late and too low to pull out gently.
('Gently' being a pull back on the controls such that the Angle of Attack is less than 15 degrees, and curves enough to pull smoothly out of the dive, go into a climb and away to safety.)
He pulls back too hard on the controls. The angle of attack goes over 15 degrees, there is no 'lift' to stop the dive, and the plane continues the trajectory straight into the girl-friend's house.
Whether that has ever actually happened, I do not know. But that was the warning not to be a smart-arse as told to me by my CFI.
Life jackets seem like they’d be problematic in an enclosed cabin where their use is if you’ve crashed and are taking on water. That’s a bit different compared to a pleasure craft or other vessel that has an outside deck and likely more time to react.
But I don’t really know things. Perhaps most float plane emergencies that require life jackets don’t suffer from my perception of the issue.
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 used to deal with these circumstances".
> I'm curious for more details about when the article says "there are approved life jackets which could be used to deal with these circumstances"
In context, that says:
“Floating and automatically operating life jackets aren’t practical, specifically because of cases like this where the occupants have to dive out of the capsized aircraft in order to escape the cabin. However, there are approved life jackets which could be used to deal with these circumstances.”
So, I guess there are approved life jackets that do not automatically inflate and are neutrally buoyant, thus minimally hindering attempts to leave a submerged plane while wearing one.
"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."
In my vernacular, I distinguish between "life jackets" and "buoyancy aids". Apparently most people don't.
A buoyancy aid has a foam core, and always provides buoyancy. It's the sort of thing you'd wear while kayaking, but it's far too bulky to want to wear it unless you expect to go in the water.
A life jacket is inflatable, and normally automatic. If you're at risk of falling in, and to do so would be dangerous, you should probably wear one of these -- if you go in the water, it'll inflate automatically. This isn't suitable if you might get wet without wanting the life jacket to inflate, though, and you can get equivalents with manual inflation. The ones you get on aircraft are cheaper than ones you're expected to re-use by wearing multiple times but in neither case will you inflate it multiple times.
The downside of a manually-inflated life-jacket is that you need to be conscious to inflate it. The downside of an automatic life-jacket is that if you get wet, it'll inflate. The downside of the buoyancy aid is that it's always bulky, but on the other hand if you're wearing it, it'll always work.
The other down side of buoyancy aids I was told about is that many (most?) will not turn you face up if you are unconscious. Gives useful extra mobility for sports but can be fatal if the wearer is unconscious.
It sounds like the two surviving passengers would have died if they had life jackets on. I can’t imagine getting out of an inverted, flooded 185 cabin with a life jacket on.
I think there was some sense to not requiring life jackets on seaplanes. They’re much more confined spaces than most pleasure boats, not to mention that you’re usually on a boat rather than in it. The flooding is also usually just about instant as the airplane rolls over.
Seems common for reactive legislation to not actually fix the situation that’s being reacted to. Requiring shoulder harnesses during takeoff and landing (which is the case in the US) would have actually kept the deceased passenger conscious to escape, as said in the report. But they didn’t change that law.
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 dangerous. You cannot jump out then, and will be killed by a tractor if it flips.
What a horrible click-bait title. There is nothing about a C185 or one modified with a STOL kit that is unstallable. A better title would be something like "Clueless pilot stalls aircraft. Which unfortunately is not an uncommon thing.
I wonder if they're practicing modern journalism strategies that are worried about libel suits? Or it's so obviously satire to them that they don't need to clarify? When they write:
> However, the investigation discovered that despite his experience, he had never practised stall recovery on the Cessna 185. The pilot had no knowledge of the aircraft’s stall behaviour at all. His opinion was that the Cessna 185 simply didn’t stall.
In writing targeted at lay readers, I would expect this to be followed with something like "This opinion, of course, is complete lunacy. All aircraft can stall. Practicing stall recovery should be a normal part of pilot training."
I believe this article doesn't need such clarifications. It says in unambiguous terms that Cessna had stalled, with an obvious logical implication that a pilot was dead wrong. The article even discusses differences of how the stall occurs in modified and unmodified versions of a plane. To not get the message a reader must be not a lay person, but an exceptionally dumb one.
Readit News
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 still: 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.
The 40lbs of gas I burn flying for an hour decreases the stall speed by more than 1mph on those Citabrias I fly.
EDIT: I was mistaken, this isn't a requirement in Europe either.
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.
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...
Stall recovery has also been an essential part of my flight training.
> ...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?
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.
One Citabria I've flown had vortex generators installed on the leading edge of the wings, but the club sold it over a year ago and I don't remember if it listed a modified stall speed. I do remember it said "not airworthy if more than N of the VGs are broken off", I think it was three?
It’s nothing too radical.
Edit - Here’s a copy of the 1975 owners manual:
https://www.seaplanescenics.com/documents/1975-cessna-185f-p...
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.
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.
What the investigation report also didn't mention is that pilots should actually practice stall recovery and not just think "if I believe strongly enough that my plane is unstallable, I can ignore stall recovery". But that probably goes without saying...
In my experience any equipment this large is effectively handmade, with all the variability implied by this. I'd hope aircraft are made to tighter tolerances than the stuff I work with but a couple of millimeters is often enough to have a noticeable effect on things like actuator travel.
> 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.
This is exactly my takeaway as well. Rather than trying to determine the characteristics of the machine to the n'th degree, assume a realistic degree of variation and design for it accordingly.
It is not necessary as in "there is no legal obligation", true.
But if you want to live, it is absolutely necessary. The numbers provided by the manufacturer will tell you absolutely nothing about the stalling characteristics of the airplane as soon as you start modifying it.
The non-linearity of the phenomena involved in stalling also mean that "intuition" and "small changes" will be of absolutely not help to determine by how much you changed the characteristics of your airplane.
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.
Anyone doing the above with unfavorable wind has a death wish.
Why? Well, stall speed isn't a real thing. There isn't a speed at which you stall, that's not how it works. It's a convenient short-hand that we use for the more complicated reality. The physical reality is that stalls happen at a particular angle of attack (AOA) into the apparent wind. That is, the angle of your wings relative to the airflow. Up to the critical angle a higher AOA means more lift to counteract gravity. As you slow down you generate less lift because there's less airflow over the wings. So as you slow down, in order to generate a similar amount of lift you have to increase your AOA. If you keep slowing down and adjusting your AOA to compensate, you'll reach a speed that's low enough and therefore AOA high enough that adding more AOA no longer adds more lift (the air no longer flows smoothly over the wing). That's the stall speed, the speed at which more AOA no longer generates more lift. But it's the AOA that's the problem, not the airspeed.
In addition to lower speeds needing more AOA, you also need a higher AOA if you weigh more. A wrong but illustrative way to think about it might be that you need the engine's thrust pointed more towards the ground the more you weigh. That means that as you burn fuel (lose weight) the AOA that will stall you doesn't change, but the excess AOA available due to your weight-change does so in effect the air speed at which you would be near the critical AOA to stay airborn does change.
Stall speed is still a useful concept especially while landing but it's misleading outside of landing and when anything else is remotely unusual like weight or modifications to the plane. For this reason the FAA has been trying to get AOA indicators installed in planes and to train pilots to look at those instead of thinking about stall speeds https://www.faa.gov/sites/faa.gov/files/2022-01/Angle%20of%2...
https://ciechanow.ski/airfoil/
Useful to think of the airplane as standing still while the engine accelerates the air around it. To fly, you need the air to move over the wings quickly and in the right direction.
You can sort of trade how fast you need the air to go for how ideally the air is flowing over the wings. If you angle the wings just right against the air flow, and/or you bend them out of shape just right with flaps, you can slow down a lot while relying on the air itself to carry your plane. If you're flying against the airflow, you need to go faster.
This is usually done during take off and landing. The pilot lowers the flaps when approaching to land and flares the aircraft before touchdown, all to make the air flow efficiently into the wings, thereby allowing the aircraft to slow down without falling straight down like a stone.
That's why weather is so important for flights. Pilots need to be ready to call TOGA and go maximum thrust at a moment's notice just in case some crosswind or heat wave or something screws up the direction of the air flow just as they're about to land. Many an admiral cloudberg article has been written due to that sort of thing. You angle the plane just right, slow it down just to the edge of stalling, then some phenomenon happens and increases your stall speed past your current speed...
Deleted Comment
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.
Sure, ye olde haptic feedback + inner ear + stall horn/shaker combo has always worked for me—but if you are a new or overwhelmed or complacent or unlucky pilot, having a big angry indicator sitting atop the glare shield furiously (visually & audibly) informing you of the approaching cross-control stall that is about to bury you in your base-to-final grave makes danger IMPOSSIBLE to miss.
The LEDs were bright enough to be clearly visible even under direct sun, but the Geiger-esque clicking and chattering increasing in urgency as I approached critical AoA made it for me. No need to put your head down or even alter your scan to include it: you can hear trouble coming!
Aviation could be cheaper, safer, and better in general if the FAA was not stuck in the 60s.
There are FAA regulations that are overly conservative IMO, but I think the FAA has a sensible stance on AoA indicators.
I also think that these old airplanes are really ships of theseus. Maybe there are some original stickers and seats, but that's about it. Safety and avionics upgrades on these old airframes are definitely in the financial reach of many readers of this forum, and I'm sure many people are flying "old" airplanes that have AoA sensors and IFR-certified glass panels and backups. Day to day they probably feel a lot like airline pilots.
Modern stuff, like you point out, is far more reliable, cheaper, lower power consumption, and more functional. That better reliability means less need for aircraft mechanics and avionics shops.
Nobody would want their discreet component transponder overhauled if it could be replaced with a cheaper unit that uses modern wizardry like logic chips or even (gasp) a microcontroller.
Ditto for leaded fuel air cooled piston engines with manual mixture controls that require teardowns all the time. That bullshit is only still around because Continental and Lycoming want it to.
https://en.wikipedia.org/wiki/National_Airlines_Flight_102
https://www.faa.gov/lessons_learned/transport_airplane/accid...
[1] https://en.wikipedia.org/wiki/National_Airlines_Flight_102
All aircraft equipped with a six pack, you have an artificial horizon indicator which can tell you what is your angle of attack. And Cessna's have them in all planes, even 50-60 years old ones.
Artificial horizon is not a reliable indicator of angle of attack.
But I like the imagery of a a little tea kettle on a hob under the panel.
Stalling one wing but not the other usually results in a spin, for which recovery requires both breaking the stall and stopping the rotation. The ailerons, located near the wingtips are not effective (or even counterproductive) during a spin because air is not flowing smoothly over the stalled wing; the rudder, located on the tail is used to stop the rotation. This usually requires more altitude for recovery.
If you stall one wing but not the other at an altitude of 15 meters (49 feet), it's very likely you're going to contact the surface in a manner you did not intend. Inappropriate control inputs, such as trying to correct the resulting bank using the ailerons guarantee it. It's still a good idea to attempt to recover rather than sit still and pray because a more controlled impact is usually more survivable.
[0] https://aerocet.com/uploads/A-10010.pdf
"According to the operating handbook, the An-2 has no stall speed. A note from the pilot's handbook reads: "If the engine quits in instrument conditions or at night, the pilot should pull the control column full aft and keep the wings level. The leading-edge slats will snap out at about 64 km/h (40 mph) and when the airplane slows to a forward speed of about 40 km/h (25 mph), the airplane will sink at about a parachute descent rate until the aircraft hits the ground." As such, pilots of the An-2 have stated that they are capable of flying the aircraft in full control at 48 km/h (30 mph) ... This slow stall speed makes it possible for the aircraft to fly backwards relative to the ground: if the aircraft is pointed into a headwind of roughly 56 km/h (35 mph), it will travel backwards at 8 km/h (5 mph) whilst under full control."
I'm sure this is a slight exaggeration in my memory, but it really was able to fly incredibly slowly and take turns in an incredibly short distance.
It would be a neat trick to see a pilot pull that off intentionally and under control.
It sounds like the pilot wasn't fully prepared and engaged to compensate for propeller torque at the moment the aircraft left the surface of the water. At full takeoff power in a single engine aircraft this can be very intense and jarring, particularly with a high pitch ascent and full prop pitch. All it took was a momentary lapse in keeping the wings level to stall out at that speed.
>The indirect causal factor was the pilot’s lack of experience with stalling the aircraft. He told the investigation that he had never stalled the aircraft, which meant that he was unable to recognise the stall during the take-off.
It's this lack of stick and rudder skills at the root of the incident.
Further down.
> The maintenance team discovered an incorrect right wing geometric twist, which was unrelated to the hangar roof collapse but probably happened during repairs done previously in the USA. As a result, the aircraft had a tendency to roll and had been uncomfortable to fly because of a lack of aileron trim. This might explain why the pilot had the aircraft trimmed full right rudder on take-off: to correct for this roll.
He may have actually had too much rudder. They don’t say this explicitly, but correcting for roll with rudder means you’ll be cross controlled.
He was dangerously near stall speed without realizing it. Some turbulence could cause a small partial stall.
If the airplane was straight, it would have just dropped the nose a bit and corrected. But with a twist in one wing and 2/3 of rudder trim engaged, it’s more like it entered a snap roll. One wing was stalled, one was still making lift.
The airplane felt fine to the pilot, but it was essentially modified to be a snap roll machine. I don’t think a stock 185 would have even been capable of what happened here.
> When they repaired the damage to the right wing, they also corrected the geometric twist, removing the aircraft’s tendency to roll.
However, since the repairs were completed five days before the accident, the pilot may have set the rudder based on pre-repair experience with the plane. He may not have been informed of the change in twist, or may not have understood it.
Exceptions, which of course must exist, include some fly-by-wire setups which limit the actuation of flight surfaces so that it should be theoretically impossible to put an aircraft in that situation, and rumored properties of some abnormal constructions like the An-2. Although even there you should repeatedly get comfortable with what happens in/around a stall, at least in simulators.
The fact that air started to separate and the end of the wing, and not at the root, is scary. It means the pilot wouldn't get the normal warning in the form of airframe shaking. Bad modification.
> If the angle of attack exceeds the permitted limits, some yaw disturbances appear around alpha 25-28°, and at alpha 28-30° there are weak pitch-up tendencies. If the stick is moved forward to counter the pitch-up, the aircraft returns to normal alpha, possibly after overshooting up to alpha ~50°. Note that the angle of attack instrument only shows the area -4° to +26°.
> If the stick movement forward at the pitch-up is too small or is made too late, such that the angle of attack does not immediately decrease, the aircraft departs into superstall or spin. If the pitch-up occurs without aileron input, the departure usually results in superstall. If the pitch-up occurs with any aileron input active, the aircraft is affected by adverse yaw and the likelihood of a spin increases.
In addition to the superstall, the aircraft has two spin modes, in the flight manual referred to as flat and oscillating. The difference is basically the rotation speed and if there are oscillations in pitch and/or roll or not. The recovery is pretty conventional:
> In superstall or spin the pitch authority is good, which eases recovery. Aileron input results in adverse yaw, that is to say rolling right gives a yaw to the left and vice versa. Rudder authority is negligible.
> Recovery from superstall and oscillating spin is accomplished by moving the stick to a position somewhat forward of the neutral pitch position, with ailerons and rudder neutral. To recover from a flat spin, the yawing rotation must be stopped first, which is accomplished with neutral pitch and full roll input in the direction of the rotation ("stick into the spin"). When the rotation has just about ceased, recovery is accomplished with neutral ailerons and the stick somewhat forward of neutral, just like when recovering from superstall and oscillating spin.
In addition to regular stalled attitudes though, the aircraft also exhibits another stalled attitude with autorotation, the "plunging spiral" (sv. störtspiral) which can also be encountered in two variants. I'm honestly not sure how exactly it works aerodynamically. The flight manual says:
> In certain adverse dynamic scenarios, the aircraft can enter an uncontrolled attitude of the autorotating type, here called plunging spiral . The plunging spiral, which can be either right side up or inverted, is considered to be the potentially most dangerous form of uncontrolled flight that has been discovered during the spin tests of aircraft 37.
> The most common form of the plunging spiral is the inverted one. The following attitudes/maneuvers repeatably result in an inverted plunging spiral: 1) somersault into inverted position from oscillating spin (for example while attempting to recover from a spin with the stick fully forward), 2) stalling the tailfin through so-called "knife edge flying". The inverted plunging spiral is characterized by: 1) negative load factor (-1 to -3 G) 2), low nose, 3) very high rate of rotation in the roll axis (≥ 200°/s), 4) high sink rate (≥ 150 m/s).
> Moving the stick back and/or aileron input to either side tends to increase the rate of the roll rotation. The rotation can be stopped by moving the stick fully forward with no aileron input. When the rotation has ceased, the stick is moved back to neutral pitch, and the aircraft recovers to controlled flight.
> The aircraft only departed into a non-inverted plunging spiral on a few occasions during the spin tests. It has not been possible to define any repeatable attitude or maneuver that results in a non-inverted plunging spiral. During the spin tests the non-inverted plunging spiral only occurred on the following two occasions (not repeatable): 1) when recovering from an inverted superstall, 2) when recovering from an oscillating non-inverted spin. The non-inverted plunging spiral is characterized by: 1) positive load factor (+1 to +3 G), 2) low nose, 3) very high rate of rotation in the roll axis (≥ 200°/s), 4) high sink rate (≥ 150 m/s).
> In a non-inverted plunging spiral, aileron inputs have no effect. Instead, the roll rotation must be stopped by pulling gently back on the stick until the rotation ceases. When the rotation has ceased, the stick is moved forward to the neutral pitch position and the aircraft recovers into controlled flight.
This article is the first I'm hearing of a Cessna 185 being considered unstallable and I do wonder it that title was picked for engagement. Float planes are extra dangerous with more that can go wrong and less margins for safety.
There are many ways of totalling a plane beyond a stall.
THERE IS NO SUCH THING AS AN 'UNSTALLABLE' PLANE.
I once overloaded a plane inadvertently, by having a heavy load plus a full weight of fuel.
At the point of lift-off, the stall-warning started screaming at me as I started to go into the climb. Training kicked in and I pushed the nose down to maintain flying speed. Practically no climb at all possible though. I did a very quick and low circuit, landed and offloaded.
Funny how those little tense moments stay with you for ever. :)
There is such an animal as a high-speed stall, where the angle of attack is greater than 15 degrees. Can happen when a gung-ho pilot makes a high speed dive over his girl-friends house and leaves it too late and too low to pull out gently.
('Gently' being a pull back on the controls such that the Angle of Attack is less than 15 degrees, and curves enough to pull smoothly out of the dive, go into a climb and away to safety.)
He pulls back too hard on the controls. The angle of attack goes over 15 degrees, there is no 'lift' to stop the dive, and the plane continues the trajectory straight into the girl-friend's house.
Whether that has ever actually happened, I do not know. But that was the warning not to be a smart-arse as told to me by my CFI.
But I don’t really know things. Perhaps most float plane emergencies that require life jackets don’t suffer from my perception of the issue.
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 used to deal with these circumstances".
[0] https://en.wikipedia.org/wiki/Ethiopian_Airlines_Flight_961
In context, that says:
“Floating and automatically operating life jackets aren’t practical, specifically because of cases like this where the occupants have to dive out of the capsized aircraft in order to escape the cabin. However, there are approved life jackets which could be used to deal with these circumstances.”
So, I guess there are approved life jackets that do not automatically inflate and are neutrally buoyant, thus minimally hindering attempts to leave a submerged plane while wearing one.
A buoyancy aid has a foam core, and always provides buoyancy. It's the sort of thing you'd wear while kayaking, but it's far too bulky to want to wear it unless you expect to go in the water.
A life jacket is inflatable, and normally automatic. If you're at risk of falling in, and to do so would be dangerous, you should probably wear one of these -- if you go in the water, it'll inflate automatically. This isn't suitable if you might get wet without wanting the life jacket to inflate, though, and you can get equivalents with manual inflation. The ones you get on aircraft are cheaper than ones you're expected to re-use by wearing multiple times but in neither case will you inflate it multiple times.
The downside of a manually-inflated life-jacket is that you need to be conscious to inflate it. The downside of an automatic life-jacket is that if you get wet, it'll inflate. The downside of the buoyancy aid is that it's always bulky, but on the other hand if you're wearing it, it'll always work.
In boating a life jacket does not need to be inflatable. https://uscgboating.org/recreational-boaters/life-jacket-wea... says:
> There are four basic design types: Inherent, Inflatable, Hybrid, and Special Purpose.
> There are two main classes of PFDs.
> * Those which provide face up in-water support to the user regardless of physical conditions (lifejackets).
> * Those which require the user to make swimming and other postural movements to position the user with the face out of the water (buoyancy aid).
It mentions both "Foam filled lifejackets" and "Inflatable lifejackets".
The other down side of buoyancy aids I was told about is that many (most?) will not turn you face up if you are unconscious. Gives useful extra mobility for sports but can be fatal if the wearer is unconscious.
I think there was some sense to not requiring life jackets on seaplanes. They’re much more confined spaces than most pleasure boats, not to mention that you’re usually on a boat rather than in it. The flooding is also usually just about instant as the airplane rolls over.
Seems common for reactive legislation to not actually fix the situation that’s being reacted to. Requiring shoulder harnesses during takeoff and landing (which is the case in the US) would have actually kept the deceased passenger conscious to escape, as said in the report. But they didn’t change that law.
Mandating the seatbelts exist, sure. Mandating people wear them? Idk about that.
In the case of tractors for instance, wearing a seatbelt is downright dangerous. You cannot jump out then, and will be killed by a tractor if it flips.
> However, the investigation discovered that despite his experience, he had never practised stall recovery on the Cessna 185. The pilot had no knowledge of the aircraft’s stall behaviour at all. His opinion was that the Cessna 185 simply didn’t stall.
In writing targeted at lay readers, I would expect this to be followed with something like "This opinion, of course, is complete lunacy. All aircraft can stall. Practicing stall recovery should be a normal part of pilot training."