Vince Neal's Jet Skids Off Runway at SDL 1 dead

[Hogmann]

Watching the video something never quite looked right to me. I was convinced it was a takeoff accident because I never see the plane come in for the landing it just magically appears at the far end of the runway.

It's been confirmed that they were arriving and it was a landing accident but that still leaves open the question, why were they down on the runway so early?
A review of some notams shows taxiway signs that are out of service and the segmented circle also out of service. Coupling that with the video I've created a approximate ground track of the plane.

That's the red line on the diagram here. The green marks are the painted touchdown Zone which is 1,000 ft from the threshold. The touchdown zone is also the aim point so on a stabilized approach the plane would be touching down at that zone or shortly after, not before. It sure seems to me like they touch down very early and are already on the ground well before the touchdown zone.
I've flown into Scottsdale a few times and it's not the easiest approach if you're not familiar with it. There are no straight in instrument approaches because of the terrain, so you must accept a visual approach or circling also the visual glide slope (PAPI) is four degrees which is 33% steeper than normal.

I can't find it now but I swear I saw some adsb data about this plane that showed him coming in at about 120 knots ground speed which with the reported wind yesterday would be 5 or 10 knots above Vref (approach speed). Usually a steep approach with a slightly fast airspeed will result in excessive floating. (Think Jeju air) alternatively if they were a little fast on short final they may have pulled the power back too much, this combined with the steep descent may have left them unable to properly flare resulting in a hard landing.
A hard landing can create directional control issues when the plane rebounds off its landing gear or if you land hard enough you can cause landing gear or tire problems.
I know there's a picture of the left main landing gear sitting in the gravel way away from the plane. But that's understandable considering the speed they're traveling when they left the runway that it would get ripped off completely going through the gravel.

[Hogmann]

Okay I found the adsb data.
I haven't converted these numbers exactly for non-standard atmosphere but the weather was not that far off of standard that day and this shows him a mile and a half from the runway and over 700 ft above it which is well above the four degree Glide slope also he's at least 20 knots above Vref at this point.
He continues this steep descent while slowing down to the runway the whole time so I think this supports the theory that they ran out of energy and landed very hard.
https://globe.adsbexchange.com/?icao...10&trackLabels

[William May]

On a Lear, the "Gear Unlock" function and warning comes from a small ball bearing that sits in a groove on the very end of the gear actuator upper barrel. The upper barrel is fixed to the 7th and 8th spars, on the rear side of the landing gear well, by a mount bolt that slides into a bushing on #7 spar, then then a castellated nut secures it at the back of #8 spar. There is a switch drilled into the actuator barrel. I don't know if it can be seen in the pic of the gear laying on the runway or not. When the gear is fully extended and in position, there is a ball bearing collar that locks around the actuator rod. At this point, the actuator is fixed, and even if you lose all hydraulic power, it cannot collapse. You can see how well that works, by the fact that the actuator rod is STILL fully extended and locked in position, even though the gear was physically torn out of it's mounts. When the ring collar and lock balls drop into place, the actuator and the barrel become one totally solid piece. The switch is turned in or out to give the adjustment for the indication function. Since the actuator rod did not move, they would not receive any unlock indication. They probably got a "gear red" light on the landing gear indicating panel, when the wiring was severed, as there would no longer be a signal going through the switch indicating locked. That would have happened when the gear separated from the aircraft, but by that point, the crew knew they had lost the L/H gear by the left wing sagging onto the ground but they also probably heard a huge "BANG" as the gear departed the aircraft, but there was nothing they could have done at that point. If that other aircraft had not been parked there, they would have slid another 200 feet and ground to a halt, and everyone would have gotten out completely unscathed. Even the main entry door would probably have opened with no problem. I suspect the crew had already killed both engines and switched off the power before the impact, as there was not even a HINT of a fire. There is still a co-pilot who survived, so he can tell what was going on in the cockpit. Once they got off the runway, they must have hit a drainage collar, or some other LARGE and heavy feature on the grounds in between the runway and the inner airport apron, but I can't see it in the video. I think the point where the aircraft "bobbles" as it is moving along it's path is where it actually tore the gear out.

Lear landing gear is INCREDIBLY tough. I have seen cases where the gear physically punched up through the wing, but was still in place. In fact, in that instance, it was enough to fracture both engine mounts at the pylons, leaving the engines to hang onto the airplane by the sheet metal fairings and the tubing and cables that connected them to the pylon. The impact also separated the tip tanks from the end of the wing. One tore off completely, and the other one broke in half at the forward joint and departed. There was no fire in that event, either. It was a landing training event, and they had about 1/2 full fuel left after training when the accident happened. I have all the pics from that recovery operation, and if I ever learn how to post stuff, I will put them up here.

They just announced that in the Philadelphia accident with the Lear 55, that it had a Cockpit Voice Recorder, but no Flight Data Recorder, so it will be harder to work out the events of that flight. I don't know what this aircraft had as far as those things, but this was probably a loss-of-control event when they touched down, so the CVR and FDR would probably not matter much.

[Tony76]

At least the planes didn't explode on collision..

[Hogmann]

Originally Posted by Tony76

At least the planes didn't explode on collision..

That would kickstart my heart.

I wonder if the injured saw Dr Feelgood at the hospital?

[akham]

What I see in the video is a yaw to the left, departure from runway to the left over rough ground and then wings change from being level to not-so-level. Based on that I would put my money on the loss of landging gear strut being a result of runway excursion and not the other way around. That's best guess based on the info available.

Some are speculating that the aircraft landed on a taxiway, which is refuted by the ADS-B data at least and I think the video also shows it landed on the runway.

[akham]

Originally Posted by Hogmann

why were they down on the runway so early?

This is a bit ambiguous - having looked more closely (prompted by your astute observations about glide slope) it is clear that their rate of descent was way too fast (see below) but based on ADS-B data the WoW switches did not activate until well after the touchdown point.

It sure seems to me like they touch down very early and are already on the ground well before the touchdown zone.

That is not what the ADS-B data says.

I can't find it now but I swear I saw some adsb data about this plane that showed him coming in at about 120 knots ground speed

Well, I did post a link to the ADS-B data on ADSBx and a screenshot of it in post #4 on this thread. :) I've attached the screenshot again to this post for convenience.

Usually a steep approach with a slightly fast airspeed will result in excessive floating. (Think Jeju air)

That is what the data shows, IMO.

Here are my calculations, please correct me if I am wrong (remember - I passed the exams and flew a little bit...)

ADS-B data shows ground speed of about 120kt = 120NM/hr = 729,120ft/hr = 12,152ft/min.

Nominal descent rate (ft/min) on a 4 degree G/S at 120kt = 12152 x tan(4 deg) = 849ft/min.

Looking at the ADS-B data, as soon as the aircraft turned final its descent rate increased from a few hundred ft/min to 1088ft/min, then 1216ft/min, 1600ft/min, back to 1200ft/min, 1000ft/min as they crossed the threshold. And they crossed the threshold at around the correct height, given the aircraft reports altitude to an accuracy of 25ft.

When the aircraft crossed the power lines about 1.6SM from the touchdown point they should have been 590ft AGL (2090ft pressure altitude) but were at 2250ft and descending at 1088 ft/min.

Once over the threshold the aircraft was "level" (within the 25ft range) for 1600ft (or about that, given granularity of ADS-B data) before the WoW switches activated. See attached image of my estimation of touchdown point based on ADS-B data.

That is a classic violation of stabilized approach criteria leading to a high energy state and excessive floating in ground effect. Very similar to Jeju, and this pilot didn't have that excuse!

The video we have doesn't look like there was a PIO leading to bouncing the aircraft, as usually the gear brakes at the last bounce and we don't see any bouncing while the aircraft remains straight on the runway.

I know there's a picture of the left main landing gear sitting in the gravel way away from the plane. But that's understandable considering the speed they're traveling when they left the runway that it would get ripped off completely going through the gravel.

That's my guess.

This leaves us with the question of why was there a loss of directional control? Pilot error (noting the poor approach)? Asymmetric braking (tire marks on runway)? I assume the yaw damper would have been off for landing.

Originally Posted by Hogmann

He continues this steep descent while slowing down to the runway the whole time

Remember that as glide slope increases the difference between ground speed (shown in the ADS-B data) and IAS increases. "Steep descent while slowing down" doesn't make sense because when descending, potential energy is converted to kinetic energy - you speed up. I remember making these mistakes in a C172, I have video to prove it! :)

I think this supports the theory that they ran out of energy and landed very hard.

IMO, the data shows that they had too much rather than too little energy, and they floated in ground effect for a long time (i.e. not a hard landing).

If there was a hard landing, we would either see it on the video (we don't) or by the time we see the aircraft it would either be bouncing in a PIO (it's not) or it would have a broken gear strut (no evidence in video that it does, in fact the video supports gear damage due to runway excursion).

Happy to be corrected if I am wrong, since I don't have enough PIC hours to carry your flight bag. :)

[akham]

Originally Posted by William May

probably heard a huge "BANG" as the gear departed the aircraft

Amazing engineering, Lear included a redundant warning system that works even if the aircraft loses all power!

If that other aircraft had not been parked there, they would have slid another 200 feet and ground to a halt, and everyone would have gotten out completely unscathed. Even the main entry door would probably have opened with no problem.

Sometimes your luck just runs out.

I'd love to know if there are any tire marks on the runway.

I suspect the crew had already killed both engines and switched off the power before the impact, as there was not even a HINT of a fire.

Would a fuel tank rupture be likely as a result of gear separation?

Its possible of course that wing scraping along, or hitting, the ground could rupture fuel tank(s) - but I can't see any conclusive evidence of a fuel spill in the photos.

but this was probably a loss-of-control event when they touched down, so the CVR and FDR would probably not matter much.

One pilot survived, so hopefully they will provide the information needed.

N81VN is not on the list of Part 135 certified aircraft (and, AFAIK, would not need to be 135 for this type of operation) - but that means it was not required to have CVR.

If there was a CVR, the last few minutes of approach would be interesting ... probably followed by "#### [sound of impact] ###".

[Hogmann]

Excellent math. But there are easy calculators for that on the internet nowadays.

Agreed an unstable approach for sure. Too steep and airspeed too fast but also rapidly decreasing.

Slowing down will result in steepening descent unless you change the angle of attack. At a certain point the wing no longer generates enough lift you must descend. This is what happens when you land flare for a landing. Does that make sense?

Now if he was at Vref and slowed down he would have to descend but in this case he was fast. So he was able to trade airspeed for lift and drag by increasing the angle of attack.
That works until a point but you must have enough buffer to rotate the plane to land. By the time he got to the runway he was at Vref and had no energy left. The steeper approach the more you have to rotate, so if you are too slow you will hit the runway hard. That's what I think happened here.

You wont get into a pilot induced oscillation (PIO) because you dont have excess airspeed at that point. PIO usually comes from being too fast and too flat and trying to force the plane onto the runway. I don't see him f

Im not as good with the granular ADSb data as you are so I can't explain the WOW sensor. Other than there may be some delay or if he hit hard and the plane rebounded it might not have activated yet.

[akham]

Originally Posted by Hogmann

Excellent math. But there are easy calculators for that on the internet nowadays.

I don't trust calculators provided by random people on the Internet. :)

Slowing down will result in steepening descent unless you change the angle of attack. At a certain point the wing no longer generates enough lift you must descend. This is what happens when you land flare for a landing. Does that make sense?

Of course, I've done it many times - most right, some wrong! :)

The steeper approach the more you have to rotate, so if you are too slow you will hit the runway hard. That's what I think happened here.

I'd like to know how you reconcile that theory with the data we have.

If the pilot slammed the aircraft down onto the runway before, or well before, the touchdown point surely that is when the gear would have broken? The aircraft continued on centreline for approx 1200-1500ft (after a very early thouchdown), and the video we have of that time period does not show evidence of gear breakage - in fact it supports the proposition that gear was intact until runway excursion, quite late in the event.

Im not as good with the granular ADSb data as you are so I can't explain the WOW sensor. Other than there may be some delay or if he hit hard and the plane rebounded it might not have activated yet.

That is plausible. It is hard to evaluate the reliability of the data sent via ADS-B without knowing what the delay is on that particular type (WM?) between ground contact and WoW being reported via ADS-B, and also likely behaviour during a bounce. And also what the aircraft reports via ADS-B (ground indication based on various factors or simply the WoW status). It can be quite complex, especially in a bounce scenario.

Attached is the DFDR readout from the NTSB report into a bounce incident involving N641UA (not a Lear, so only to illustrate the concept). The ground and WoW indications fluctuate over several seconds.

Currently we only have ADS-B data every few seconds so its hard to guess when the a/c touched ground and when it first sensed ground contact internally (could have been any time after 21:38:18Z).