I am a retired Aerospace Engineer and I sure wish I had professors in college that could explain things as clearly as you do. Very well done. One thing, long before 14 G's were reached I would have thought the pilot of the PC-12 would have passed out.
Austin, I'm a 300 TT CMEL and love your videos. They actually go through the entirety of "things" which doesn't leave any dangling questions. Thank you. -- We used to turn off ESP in the 172 for our steep turns and such. I believe the newer PC12 has a wing leveling system as well.
Austin, I appreciate your efforts but I think your math is wrong. I developed parametric equations to describe the 3D helical path that the plane was following right before the breakup. At that time, the aircraft was turning in a circle of 201m radius at a tangential speed (ADSB groundspeed) of 109.6 m/s. I'm ignoring wind, but I don't think the winds aloft will substantially affect the calculation. The plane also had a vertical speed of about 30,000 feet per minute at breakup (152 m/s) and the vertical speed was accelerating at about 8.76 m/s^2. The parametric equations that decribe the helical path are as follows (x, y, and z are in meters and t is in seconds): x= 201 cos 0.5454t y= -201 sin 0.5454t z= -152t - 4.38t^2 Taking the second derivative of the above equations with resptect to t yields the acceleration equations: d2x/dt2= -59.78 cos 0.5454t d2y/dt2= 59.78 sin 0.5454t d2z/dt2= -8.76 m/s^2 To find the net acceleration, we take the square root of the sum of the squares of the three above equations. That yields 60.4 meters per second squared, or about 6.2 g. I'm sorry, but there is no way the plane was subjected to forces anywhere close to 14 g.
@@GrantBaker Hi Grant, I love your videos and your extremely professional approach to flying! Another way to look at this is that if the PC-12 could handle an ultimate load factor of 14 g's, this would mean the design is inefficient. In other words, structures could be removed or made of less strong, lighter material and this would save weight while still being able to withstand about 6 g's - which should be adequate for almost any scenario. As much as the Swiss love robust engineering, they love efficiency more.
First of all, thanks for using science and numbers for explaining things. I don't know of any other RU-vid channel doing that. I have one question: Where did you find the data?
@@austinmeyer That's not what I mean. Your analysis is very sound. I'm a physicist and plane enthusiast. I'm looking for the ice-related curves. I hope there's more on the paper.
How is that you write the link to science direct link but do not show it in the description or the 1st comment? Can you share it so others have easier access, please? Thank you!!
I have wisely been asked about the WIND at the moment of the accident. After slamming my my hand into my forehead, researching it at ventusky.com showed that 273SM had about a 15-knot CROSSWIND at the termination of the spiral. A crosswind, of course, has little impact on true airspeed compared to groundspeed, as you know. As well, 15 knots is very small compared to the 325 knots airspeed experienced, so the wind in this case had negligible effect.
You guys subscribed to XPlane mobile 😞 I want to know when version 13.0.0 of XPlane mobile arrives?????? and when will the A330-200 come to XPlane mobile??? 😓😢😢😢
23:30 I regularly experience ESPP in the Cirrus, usually at the moment I'm starting to demo steep turns and I realize I forgot to turn it off, so I have to hold the autopilot disconnect to stop it ruining my turns. I hope one day to have a good relationship with ESPP.
You can also disable it somewhere in the AUX page ("System Setup 2" on P+). Just remember to turn it back on... or IIRC I believe it is re-enabled automatically on every startup.
@@jeremyroy99 yeah, I’m supposed to disable it, but frequently forget when I’m doing all the other things. I’m usually rolling toward the 45 degree bank and see the double lines reminding me that it’s still on.
Appreciate the analysis, but wouldn't the centripetal acceleration of the Pilatus be more correctly calculated only from the component of velocity in the plane of the turn (horizontal)? The centripetal g component would be the same whether the aircraft was doing the turn level or diving at 1000 KTAS vertically. Using only the horizontal component yields a centripetal acceleration of only 6g. And on the note about the effect of wind; even if it were significant that would not be relevant for the centripetal acceleration. If I am in a tornado in a balloon and the wind pushes me in a 10g spiral it's still 10gs even if with a true airspeed of 0.
I agree with Jeremy, I don't think the 14 G number is correct. It just doesn't seem reasonable on the face of it, but it also doesn't make sense as a pilot in that I can easily do a 1G turn while descending 2000 FPM. Sort of like the accelerated stall speeds that are published in the POH have a big asterisk...they assume you are pulling back hard enough to maintain altitude. If you relax that assumption (i.e., assume the plane is descending while holding the given bank), the G loading is different as are the stall speeds.
@@wjlong Thanks. To be pedantic, I might suggest one correction to your analogy with an accelerated stall: the wing loading--and thus stall speed--will be the same as level flight for any *unaccelerated* vertical motion--climbing or descending at any constant rate. Level flight and a constant 2000 fpm descent are the same in this regard. Loading will only increase or decrease for any vertical *acceleration*, or change in vertical speed. Like in an elevator you only "feel" g at the top and bottom of the trip--the rest of the ride is a constant 1g.
Hi Austin, pretty interesting video, thanks! I have a comment on how you calculated the centripetal acceleration: you took the radius of the projected path on the horizontal plane, rather than the radius of the actual 3D path, which is a helix. This will make a difference in the load factor calculation. 14 g seems way too high as the ultimate load factor of the PC12. The ultimate load for a FAR-23 aerobatic aircraft is around 9.0 (limit load is 6.0). A transport airplane the size of the PC12 will have a limit LF around 4 and a ultimate LF around 6.
Interesting video ! There is just one thing that I don't understand : If we're adding the vertical speed to the equation, shouldn't we also add the vertical flight path to the equation (thus it would increase the radius and decrease the acceleration). I feel like what we're doing here is a_3D = v_3D^2 / r_2D, which is not homogeneous. I feel like we should be replacing the 2D radius of 204 m with the radius of curvature of the 3D helix. We could do like this : R = 204 m and GS = 213 kts (110 m/s) so the plane takes 11.65 s to do one loop. In the meantime, the VS is 246 kts (127 m/s) so in 11.65 seconds, the plane has lost 1480 m. So we have to find the radius of curvature of an helix of radius R = 204 m and height H = 1480 m. There is a formula for that : RHO = R * ( 1 + ( H / (2*PI*R) )^2) We get that the radius of curvature of this helix is RHO = 476 m. Taking the formula now : a_3D = v_3D^2 / r_3D(=RHO) we get a_3D = 167^2 / 476 = 5.97 G. If we take only the 2D geometry (with V = 213 kts), a_2D = v_2D^2 / r_2D = 110^2 / 204 = 6.05 G. Then it would seem, either method (2D/3D) gives an acceleration of 6 G.
The acceleration of a helical path is the same as the acceleration of the projection onto the horizontal plane (because the difference is just a constant vertical velocity). However, it assumes that the plane has a certain orientation. To calculate the true acceleration we need the 3D coordinates.
Doesn't all that assume the airplane is pointed and traveling in the same general direction? The wreckage makes it clear he was in a flat spin, so the question is for how long. However long it was, that 6G was the least of his problems.
Why are the runways sloped so much more in X-plane vs. real life? I've notice that airports like Eagle County Regional (KEGE) and Madeira have runway slopes that seem very exaggerated.
What a fantastic presentation. I don't see many accident reports that dive into the physics of flight at this level, let alone explain it in a way that others can learn from. It's tremendously illuminating and takes a lot of the guess work out of the potential causes. Thank you Austin, really well delivered.
Maybe it is time to implement a temperature/moisture dependent ice-relevant stall probability warning and over- bank in Xavion. At least patent them before somone in Texas does
loved the video, but i wonder if the g calculation is quite right. isn't the radius of the circle they are moving through is actually somewhat larger because of the vertical component? to get the g load, wouldn't you use the radius of the circle as you calculated (which is the radius of the projection onto the horizontal plane) and the horizontal component of the speed (the ground speed)?
Why don't more High Performance GA planes have "Speed Brakes" as a required option? Most all Gliders have them for a reason, it can't be cost. Anyone know why many high performance planes do not have them in 2023?
Same old same old, cost and weight. Mooney’s had them so you could keep power on during decent so you didn’t shock cool your big 6 cylinder. But most fast stuff these days is Turboprop, so you just pull the lever back and let the flight idle pitch slow you down.
Well, at airlines we’re trained to never trust the autopilot. And no IFR pilot trusts their seat feeling in IFR. So really automation complacency started the chain for DL well before the Ice was terminal. And going back further there’s planning into icing potential, not monitoring the state of the wings in an ice favorable environment, and of course, sleazy purveyors of “known Ice” capable systems that underperform.
You guys subscribed to XPlane mobile 😞 I want to know when version 13.0.0 of XPlane mobile arrives?????? and when will the A330-200 come to XPlane mobile??? 😓😢😢😢
Just updated X-Plane 12 to the latest version 06 and what a disappointment. I was under the impression 06 was to take care of lighting issues, The instrument panel is so dark on the Cessna 172 it's unusable. Talk about flying in the dark on a VFR day. Ever try changing the comm frequency from standby to active, it doesn't work. I've been waiting for the past 9 months for these issues to be corrected. A BIG disappointment Mr Myer.
sad x-plane does not calculate collisions and leaves it to some external game engine getting the object jumping around when hitting ground for example. i found - as this guy demonstrates - consequences of failures were a perfect way of how x-plane could extend its feature line and add creditability to its simulating facettes, as it is an essential part of aviation. here his C172: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Knp8SgXD868.html and here a B747: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-8MNTP1k3pcA.html . Look at it and tell me this would not be a great feature. i don't see valuable reason not implementing this. i'd hire that guy for that particular job. I guarantee there is not a single aviator out there who doesn't want to see failures simulated, while a crash is just one scenario. Students asking: "what happens when.." and there is in fact no tool out there to show that part. The sully landing on the hudson is a perfect example of an event no one would be able to train upfront, and personally i believe X-plane should be the tool to include that.
Its fastinating watching how fast you math all these things out to make sense of it all! You make it look so easy that i cant help thinking i was short changed when it came to brains though!!! But when you get right down to finding yourself flying in a situation such as youre describing, I think very very few pilots might have the ability to save themselves by the time the stall hits. Knowing this would make flying in ice of any kind extremely scary and to be avoided at all costs!
very interesting. I wonder though why Austin didn't reply to several posts that questioned his analysis? Might Austin have an update vs just leave this video posted as is? Thanks.
At 66 years old with a high school diploma and being a little better than average in math comprehension i was able to understand this whole presentation!.😊
Just like your 'why is the Cirrus jet slow', this is a great video with very solid technical underpinning. I also liked your GA Figure of Merit on your website - perhaps that could be the subject for a future video as well.
I think I have an apropos question: can I fly and do a series of maneuvers, and then have XPlane reproduce that same flight while I mess around with the cameras? Thanks!
I'm confused. Even if we account for his vertical speed, we still have no way of knowing his actual airspeed. It gets us closer obviously, but is it close enough to conclude anything definitive?
"Even if we account for his vertical speed, we still have no way of knowing his actual airspeed. " Not true. His ground-speed is printed on the map, and his vertical speed was reported as well, as you can see on the web page. So his 3-dimensional, not 2-dimensional, speed with respect to the ground, was 325 knots, as I explained at t=16:30. The wind was a light crosswind, so it made little or no difference.
@@austinmeyer Which way is a crosswind blowing when you're flying in tight circles? And it seems unlikely the airplane would fall apart at 204 knots max, don't you think?
@@austinmeyer The video isn't the problem. You said "His ground-speed is printed on the map" and his "groundspeed and airspeed were basically the same". Can you give me the timestamp that coincides with the speed of 325 knots?
@@Milkmans_Son I explained his airspeed very carefully at time = 16:30 When i said 'ground speed and airspeed were basically the same" , i did in that case mean his 3-dimensional, not 2-dimensional, speed with respect to the ground. The total speed with respect to the earth, considering both the lateral and vertical dimensions, which do indeed sum to 325 knots, as i do indeed prove at t = 16.:30
Outstanding! I wonder how N515DL’s icing incident compares to Colgan Air 3407. There the autopilot also stayed engaged until the stick-shaker activated. Alleged pilot-errors notwithstanding, if I recall correctly, the gear and flaps were lowered just before the stall-warning, likely resulting in a speed reduction at an airspeed the pilots must have deemed acceptable. The NTSB ruled out ‘severe’ icing, but Austin’s analysis here suggests the onset of a stall is not only sudden but practically unrecoverable with what a pilot might consider a reasonable angle of attack.
A lot of math-ese for me, but very interesting to say the least. I heard the PC-12 audio on a previous investigative channel that was down right chilling. I live in an area outside of KORD, KDUP and KARR, there are all sorts of aircraft overhead and to hear that, well, I cant imagine hearing it at my home. I am glad to see someone(company) offering more safety features like the ESP.
We ALL need to hear this information! Excellent compare and contrast! Like it's inventor, the XP system is such a terrific educational tool. I really do learn a LOT!
Excellent analysis Austin! Dealing with the actual ADS-B data forensically using first principles gets rid of a huge amount of rank speculation on the PC-12 crash. Most credible analyses or commentary suggested pilot lost situational awareness when the autopilot kicked off. He was flying in moderate turbulence, with a warning about it in one of his ATC exchanges. So as you demonstrate it was not icing that kicked off the autopilot, but the turbulence sure could. Even worse, the pilot's head is only inches from the avionics power switches overhead, so if he was not belted down tight in his seat, a moderate to severe turbulent bump could propel his head to hit the avionics power, which is not guarded, making his displays go dark - and at night in IMC and very bumpy, there is no more situational awareness and as you point out he got into a death spiral. At least that is one possible reason an apparently decent pilot could loose control and enter a death spiral. Reference video showing overhead switches and avionics buss switches in a PC-12: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-MSBQBy21LkE.html Relevant segment is at time 14:10 to 14:30
A superb video. Thank you. Understanding the maths / physics on icing at least gives one a fighting chance should something go wrong as normal recovery techniques won’t work. One observation on the autopilot climb: one is taught to set the climb speed (as opposed to rate) precisely to prevent the autopilot climbing into a stall (not that this would have helped with a heavily iced plane).
Setting the AP to climb rate at a lower altitude is fine but once you get towards the thin air say above 10,000 for sure you should set the AP for climb speed well above any anticipated stall speed. There is definitely history of aircraft crashing due to the fact that the crew set the autopilot to a climb rate in that climb rate cause the aircraft to stall at altitude. This was just the beginning of a number of errors that led the crew to actually crash the aircraft and yes they were killed, again this area just started the series of events that crashed the aircraft the second pilot in this smaller craft might have caught it but the crash is noted above had two pilots too bad they weren't focused on safety and we're jacking around trying to get the aircraft to its certified altitude a big no-no if you don't know what the f*** you're doing, God bless
That is absolutely not correct you could have a headwind of 100 mph and you're doing a hundred miles an hour so your ground speed is zero MPH. Now you Yank back on the stick and you pull 3 g's but still your ground speed is zero MPH.
@@XPlaneOfficial The ground track is the projection of the 3D path onto the horizontal plane. By measuring the radius of the ground track it is implicit that acceleration in the horizontal plane is being estimated. The ground speed is the projection of the 3D velocity components onto the horizontal plane and is therefore the value affecting the acceleration in that plane.
@@hypo-jt7yb has it exactly right. The centripetal acceleration would be the same whether the vertical component of velocity was 0 knots or 1000 knots.
Facts tell, stories sell... My five pence: Try not to make videos of yourself and your knowledge as much and showcase your product instead. Or, if you feel the tech details are of importance for a certain customer base, then try and split the facts from the stories into a separate series or even YT channel.
How the hell is a turbine type rated pilot getting themselves in a graveyard spiral in a modern plane in 2023? I’ve been medicaled out of aviation for over a decade now, how sloppy are these fools getting out there? Oh wait, Garmin had to invent a you can’t fly safety system on a 10 1/2 inch BIG SCREEN pfd avionics system because most people flying are airplane steerers now not pilots.
Perhaps the pilot had a medical emergency. Perhaps the avionics failed. Perhaps as another commenter suggested, the turbulence caused the pilot's head or headset to switch off the avionics master (no idea if this is possible on the PC-12). It's probably not quite a simple as "bad pilot."
@@dermick I mean it could be anything. Pilot explodes into a cloud of dandelions, pilot suddenly forgets everything after they were 10 years old, or, more likely given how often it comes up, it was pilot error. Who knows, it could have been an intentional steep spiral emergency descent that went super bad. Or, as Austin postulates. It was a graveyard spiral caused by simple human failing. In the end it’s up to the NTSB, but aviation youtube only has so much to ever talk about that isn’t either rich guy toy reviews or crash speculation.
If I remember right in a Bonanza I flew years ago there was a placard on the visor that said something to the effect of lowering the landing gear and flaps if you start to experience an overspeed condition. This of course has to be practiced with the understanding that you might damage the landing gear doors or flaps if deployed when flying in an overspeed condition, but it just might save your ass
So this PC 12 just " wandered off kilter " come on we have to have a better answer than that. And yes maybe the wing might be 14G but since it looks like the horizontal stabilizer let loose first, then I would say that this structure is less than 14g. But again who cares about the structure we need to know what caused the aircraft to depart heading and pitch actual breakup came about much later. The question I have is could a FO/co-pilot prevented the aircraft from entering the graveyard spiral and subsequent breakup. Thanks AM for developing X-PLANE, a very cool tool for sure.
