Learjet 60 crash in West Palm Beach

MikeD said:
Pilots rush the recovery and accept sloppiness. Asymmetric G loading is bad enough in fighter jets, but worse in fatty jets that aren’t designed for even moderate symmetrical G loading, much less asymmetrical. It’s a good way to unintentionally bend or break things off of your aircraft during a nose low recovery, which will only make your manageable situation worse,


If I were king for a day, I’d have all fixed wing pilots go through a mild centrifuge training profile, probably to about 3.5-4Gs tops, just to experience what that weight loading feels like.
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"I just press the red button and wait for the airplane to stop yellnig at me..." - Random new Vision Jet pilot.
 
jtrain609 said:
I wouldn't hang out in those conditions in any aircraft, but @Kingairer has a point that it could have been ice crystals.
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If I had to hang my hat on a hunch, this + loss of airspeed recovery = Mach tuck on a Mach-critical wing. tail came off while trying to pull out of the tuck event with full power on it. Power stayed on; the plane went fast into the ground. The impact is strikingly similar to other Mach tuck events in the 40/60 series.

But thats a guess... it does stick with the ice crystals... kind of like AF447.
 
Itchy said:
So does the 60 have electric heat on the stab or not? Was it an option? I ask because I have seen some folks say it does, and some say it doesn’t.
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It did not on all 3 Lear 60s I flew. Whether it was an option, I have no clue. It was told, as described above, as not needed due to aerodynamics, according to the schoolhouses I attended.
 
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NovemberEcho said:
I wish we didn’t allow streaming live ATC coms like the rest of the world. Although tbf more than once I have gone to live ATC to see if I messed up or the pilot messed up lol
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Accountability and visibility both suck, but, lead to a better product at the end of the day.

The social media armchair QB’ing is what makes it less tolerable.

If only it was like Reddit where some subs require verification before you a spout off Dan Gryder style theories.
 
Stone Cold said:
It duds not on all 3 Lear 60s I flew. Whether it was an option, I have no clue. It was told, as described above, as not needed due to aerodynamics, according to the schoolhouses I attended.
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It seems that via certification testing, we’ve discovered that it’s not really needed on a lot of airplanes I don’t think many of the new ones have it. I don’t think think I’ve flown one with tailplane protection since the Q400 in 2012.

That airplane was a gigantic POS though, and bombardier products seem to have issues with ice- so I’m not surprised.
 
Kingairer said:
As far as coffin corner, they had been flying at 410, so they at least had that spread. Not familiar with the lear, but I would assume 6,000 feet descent would greatly increased your min/max spread.
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True, but that was without any up/downdraft and perhaps a pilot fighting the vertical upset with a control input that increases the load factor. I can't speak for the Lear, but in my airliner plane, we typically cruise within a few knots of the barber pole at higher altitudes. Increase load factor much above 1G and that bottom end will close up pretty quickly. And that doesn't even begin to get into possible airframe icing effects. But your point is certainly valid. Even if it wasn't mach tuck, it would seem that whatever upset they encountered was over controlled to a structural failure. Startle factor, and a lot of airspeed combined in a recovery can yield unintentionally high G pretty fast.
 
Kingairer said:
My GUESS,
No airframe icing. At -47C, I am not convinced of the SLD potential associated with the mega storm, from reports she texted about the ice 8 minutes prior to the final descent.
Stall? She is nearly live streaming from the moment they go into this cloud unless the audios I have seen have been edited or speed up. You dont hear any shaker or any report that they did.
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But... they were reporting moderate icing...
 
How limited would it be by the loading? It doesn't seem like 35 would be very hairy in an airplane certified to 51 even if it was heavy....

as for icing.... "Managing the ice" is an interesting thing to say, to me, In all my time flying jets ice was literally not something I'd even mention unless I was giving a pirep. To even mention it like that kinda makes me think it was a pretty good amount. But I don't know. Hopefully some more data becomes available.
 
USMCmech said:
Good information regarding the weather side of this accident.

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So thing analysis is informative. A couple things i don’t think he took into account. When they make the final turn towards the storm it’s a track change of about 50 degrees. I can’t imagine their radar is sweeping that wide that they could see it anymore that close in anyway. And he’s also not accounting for the fact that a radar doesn’t just sweep at the altitude you’re at. Now depending on where they had the tilt and gain…all unknowns.
 
trafficinsight said:
How limited would it be by the loading? It doesn't seem like 35 would be very hairy in an airplane certified to 51 even if it was heavy....

as for icing.... "Managing the ice" is an interesting thing to say, to me, In all my time flying jets ice was literally not something I'd even mention unless I was giving a pirep. To even mention it like that kinda makes me think it was a pretty good amount. But I don't know. Hopefully some more data becomes available.
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She also said clear ice so who knows how far back it was running on the airfoils.
 
peterkaminski said:
I’m not a pilot or a forensics professional. I appreciate that my request to post was approved, I hope it's okay. I appreciated the early discussion on this thread, and wanted to give back.

My background is in research and data analysis, and I put together three documents to try to make a little more sense of what the public data shows.

I share them in the hope that someone might find them useful as a rough outline. They're not intended as formal forensic analysis. They were prepared with the assistance of powerful and well-managed AI, and of course, AI can make mistakes.

The first doc is a back-of-the-envelope reconstruction synchronizing the LiveATC recording with Flightradar24's granular ADS-B altitude and vertical-rate data: N722BD: back-of-the-envelope synchronized ATC / ADS-B timeline

The reconstruction includes a timestamped transcript, corresponding altitude and descent-rate observations, an estimated impact time, and methodology and caveats. One interesting observation is that the repeated −32,640 ft/min ADS-B vertical rate appears to be an encoding limit rather than the aircraft's actual maximum descent rate.

Back-of-the-envelope, the final descent rate works out to ~45,700 fpm. We calculate ~13.7 seconds from the start of the last radio transmission, at ADS-B 10,550 ft, to ground impact.

The second document is a rough speed estimate from the dashcam video frames: N722BD: back-of-the-envelope speed estimate from dashcam video

It comes to around 600 mph, with 550–700 mph a fair range, compared with about 590 mph from the ADS-B data above.

The third is a check of the public radar data at the jet's position: N722BD: back-of-the-envelope check of the radar data

This view puts entry into the storm core at about 17:47:52 UTC. Radar echo was moderate at the jet’s altitude, about 30–35 dBZ near FL350, and much stronger below it, into the 50s dBZ under 20,000 ft. It also checks the radar images already circulating on social media, which hold up on the main points. It also lays out the sequence of the reported turn toward Freeport and the core entry.

An open question: News reports name the pilots as Nathalia Gadelha Filgueiras and Jeff Gregory. She is presumed to be the pilot monitoring because she's handling ATC, and he is presumed to be the pilot in command / pilot flying. (We do hear a male voice on at least one short call earlier, on the previous frequency.) But Filgueiras says "Jack" at least once, perhaps twice: "[Jack], look outside! Jack, look outside!" (The first "Jack" is as interpreted. The audio there has (scream)(audio ducking)(vowel)("k" sound), which I interpret as "Jack", but it's not assured.) Does anyone know why there might be that discrepancy between Jeff and Jack?

All three links, on a personal pastebin-like site, they'll be auto-deleted in 90 days:

"N722BD: back-of-the-envelope synchronized ATC / ADS-B timeline"
N722BD: back-of-the-envelope synchronized ATC / ADS-B timeline

"N722BD: back-of-the-envelope speed estimate from dashcam video"
N722BD: back-of-the-envelope speed estimate from dashcam video

"N722BD: back-of-the-envelope check of the radar data"
N722BD: back-of-the-envelope check of the radar data

Pete
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so youre a silicon valley AI peddler whose first post here is a “back of envelope” AI analysis of data and your question for the group of aviation professionals is

why did she call him different name?

gfys
 
DropTank said:
But... they were reporting moderate icing...
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I think she said light and managing it. How much icing has she seen in her career? But clear ice at -47? It’s hard for me to believe at that duration (over 10 min?). Was she seeing crystal flying around and reported that as “clear” ice? Managing it? The sudden change to prescription could also be a marker of ice crystal icing. There is so much science that would lead it away from traditional icing. But maybe this was a highly exceptional moment and somehow they picked up some airframe icing. I just don’t think you need icing in any answer as to what brought the plane down. The quickness at which it was basically all straight down would lead me to believe structural failure in the core of the storm. We may never know.
 
bp said:
so youre a silicon valley AI peddler whose first post here is a “back of envelope” AI analysis of data and your question for the group of aviation professionals is

why did she call him different name?

gfys
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That’s a way to think about me, sure, and the name question is a minor one next to everything else here. I have a great deal of respect for your profession, and I’m sorry to impinge on it.

I understand if you won’t read the writeups. The numbers can be checked against public sources, and I hope pilots here find them useful. A few things I think may be valuable:

- The ADS-B descent rate pegged at 32,640 fpm isn’t a real value. It’s the overflow value of the ADS-B data format. A fit through the last changing altitude reports, down to 8,750 ft, gives about 45,700 fpm (451 kt straight down). With ground speed included, true airspeed near the end was likely around 510 kt, with wind unknown.

- The aircraft is visible in only 4 frames of the dashcam video, but that’s enough to estimate speed (compare pixel length of the 58-ft aircraft to pixels moved per video frame, at 30 fps): around 520 kt (range 480–610), which agrees with the ADS-B.

- The upset was fast: from the peak of about 35,450 ft, ADS-B shows over 10,000 fpm down about 14 seconds later, as the crew calls 8,000, then 10,000.

- The track swings about 188° during the dive, turning faster as ground speed falls from about 506 to about 231 kt. So this was a sustained spiral, and the 60° bank call came while the path was still only about 40° below horizontal, well before it steepened near the end.

I want to keep this thread on the accident and what we can learn from it, not on me. I may not reply to some messages; please take that as my hope to keep the SNR high.
 
Kingairer said:
I think she said light and managing it. How much icing has she seen in her career? But clear ice at -47? It’s hard for me to believe at that duration (over 10 min?). Was she seeing crystal flying around and reported that as “clear” ice? Managing it? The sudden change to prescription could also be a marker of ice crystal icing. There is so much science that would lead it away from traditional icing. But maybe this was a highly exceptional moment and somehow they picked up some airframe icing. I just don’t think you need icing in any answer as to what brought the plane down. The quickness at which it was basically all straight down would lead me to believe structural failure in the core of the storm. We may never know.
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Many pilots, particularly rookies, have a difficult time distinguishing clear/rime/mixed and its intensity.

Also, you don't know what you're talking about....
 
One more thing from lining up the radio calls with the ADS-B. To my ear, her voice changes significantly between the 10,000 fpm call and the 20,000 fpm call. On the first she's energetic and alert but composed. On the second she sounds much more alarmed, while still having the presence of mind to keep working the radio (using the call sign, for instance). The ADS-B data changes in those same seconds.

Times are UTC and assume the LiveATC archive starts at exactly 17:30:00. Path angle uses ground speed and Mach is rough, with wind unknown and temperature taken from the crew's −47°C report:

- 17:48:30, "Mayday", 10,000 fpm call: −14,016 fpm, path 16° down, no turn (track 099°), about 0.84 Mach.

- 17:48:36, "[Declaring] emergency": −19,904 fpm, path 22° down, first movement in the track, about 0.88 Mach.

- 17:48:41, 20,000 fpm call: about −20,700 fpm, path 22–23° down, turning right at 1.2°/s, about 0.90 Mach.

- 17:48:50: −20,864 fpm, path 22° down, turning right at 2.5°/s, about 0.90 Mach.

- 17:49:03, "twenty two thousand feet ... banking sixty": over −31,000 fpm, path about 35–40° down, turning right at 2–4°/s, about 0.91 Mach.

The jet appears to go over its Mach limit at about the time of the first descent and Mayday calls. Mmo is 0.81 Mach from 26,750 to 37,000 ft (Learjet 60 AFM FM-123, Change 37, page 1-9, a 2009 revision; the FAA data sheet charts the same limit, TCDS A10CE, Rev. 67, page 23: Dynamic Regulatory System ). Assuming no wind, it passes 0.81 at about 17:48:27, about when she first calls the descent. Assuming 20 kt of headwind or tailwind moves that to about 17:48:21 or 17:48:32, still after the descent began at about 17:48:16.

The right turn first shows at about 17:48:36, about when she starts to sound more alarmed, within about a second of alignment. Before that the jet is presumably in a wings-level nose-over, with load well under 1 g (our rough estimates run about 0.1–0.4 g). After it, the bank is building at about 1.1–1.4 g, and the speed is near 0.90 Mach. Those load figures are estimates from fitted ADS-B, not measurements.

The descent rate climbs fast until about 17:48:36, then holds near 20,000 fpm until about 17:48:50 before steepening again. Her 20,000 call falls on that plateau and that number matches the ADS-B data.

What this doesn't show is what caused the change in her voice from call to call. She could be reacting to the overspeed, the rate, the roll, or recovery inputs that weren't working. It's tempting, but obviously still premature, to tie the start of the bank to the left elevator coming off, since the NTSB says most of it was found 1.3 to 3.8 miles from the site. A separation at that moment would need about 2 miles of drift or carry, which is possible, but nothing shows it. Also, of course, a right spiral isn't necessarily due to a left elevator separation. High-Mach wing drop, uneven ice or damage, or a small roll that a pull then tightens could all do it.

Same caveats as before: a rough outline, not a forensic analysis. Still using well-managed AI assistance; numbers and calculations are checkable against public data.

Pete
 
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