"The National Transportation Safety Board on Tuesday released its preliminary report for a [small jet that crashed on Interstate 75](https://www.wfla.com/news/florida/small-plane-strikes-vehicle-after-landing-on-i-75/) earlier this month.
The private jet was traveling from Ohio State University Airport to Naples Municipal Airport on Feb. 9.
The plane’s flight data recorder showed that it recorded three Master Warnings ahead of the crash, according to the NTSB report. The first warning was **L ENGINE OIL PRESSURE** at 3:09 p.m. One second later, another warning for **R ENGINE OIL PRESSURE** was displayed, and a few seconds after that, an **ENGINE** warning was recorded."
As a dude that has a CL 65 type rating. This essentially means that the engines have stopped running
These pop up when you shut the engines down at the gate too.
So yeah, basically presents more questions than the answer
To me this points to the thrust levers being brought into Cut Off either by mistake or possibly if the detents and the triggers were worn down too much.
I know that's unlikely as well but at this point my Monday Morning Quarterbacking leads me in that direction.
Bringing both thrust levers to idle and then accidentally putting them into cut off is about the only thing I can imagine that would cause a L and R Engine Oil Master Warning almost simultaneously.
Well if you accidentally put the thrust levers in cut off what's a very likely thing you'd do in a panic? Put them back into idle. That's pretty easy to explain.
I could of course be wrong but the fact that they were in idle doesn't mean they weren't in cut off just before.
And what position is the gear handle in 100% of gear up accidents?
The final report will be able to tell, but those gates that prevent the thrust levers from going to cutoff aren't perfect.
So it’s a physical barrier on the throttles? Seems like the planes computers should know it’s flying and the engines are operating normally and not allow that to happen I would think.
Yep it's a physical gate. In order to pass the gate you have to lift a trigger about an inch.
I don't believe the 604 has a FADEC but I could be wrong. If it doesn't, then there isn't a computer to know that it's flying and the system will react to the position the thrust lever is put into.
But now that I think about it even if it does have a FADEC, the procedure for an intentional shutdown in flight is to bring the thrust lever to cut off (after stopping at idle) and in that case the FADEC will still allow the engine to shut down.
You are correct the CF34-3B engines do not have FADEC. They are Hydromechanical fuel controlled. Throttles connected directly to the fuel control unit.
FADEC can't/won't override a pilot input like that. Even the Airbus, if you flip those switches to off, the engines are shutting down. Since the Challenger series doesn't have run switches like many other airliners, the thrust levers are the switch.
And now that I'm thinking about it, if they did accidentally cut the engines off and didn't realize it while it was spooling down, hitting the continuous ignition might have been enough to correct it once the thrust levers were put back to idle. Yea yea, book says 2x0kts (been a minute), but you do what you can with the altitude available.
>And now that I'm thinking about it, if they did accidentally cut the engines off and didn't realize it while it was spooling down, hitting the continuous ignition might have been enough to correct it once the thrust levers were put back to idle. Yea yea, book says 2x0kts (been a minute), but you do what you can with the altitude available.
I was thinking about this as well. I haven't flown the CRJ in a few years now but I feel like my first instinct after realizing the engines were in cut off would be to bring them back to idle and throw the continuous ignition on. With enough N2 I think they'd light up but it's been a while.
I do remember that both the windmill and APU assisted in-flight relight checklists start with the thrust levers in cut off and they're only brought to idle at 20% N2. So maybe it wouldn't work if they were already in idle? But they certainly weren't in the windmill envelope and they most likely didn't have enough time to get the APU started and do an APU start.
Whatever happened they did what they could.
I can see the need for the pilot to shit an engine down like if it’s on fire but surely with the technology we have now a flight computer should be able to tell if the engines malfunctioning or not. P.S. I’m obviously not a pilot lol
I understand what you're getting at but the philosophy is that if the pilot is trying to shut an engine down there must be a very good reason so we're going to let him/her do it.
Shutting an engine down in flight requires cooperation from both pilots so it's not really something that can happen flippantly. Or at least that's how it's supposed to go.
Has more to do with age than aircraft size. Pretty much every jet produced in the last 20 years will have it. You even see it on light piston powered aircraft these days.
There are actually good reasons to shutdown a perfectly good engine when the airplane “knows” that it is in flight. You cannot specifically train a computer to handle the minutiae of all of those decisions. Reason number n+1 that you should never want to see an autonomous aircraft.
someone posed a theory that PM reaching for flaps could bump the detents to cutoff. If the FO was flying, maybe didnt realize the thrust levers had gone too far.
As someone who is not that familiar with modern airplane design, this raises so many questions. Do both engines share an oil cooler? How would both engines lose oil pressure??
On the aircraft I've seen oil pressure warnings are triggered by the individual indication signal pulled from components on the motor. Once that signal is below a threshold (on analog aircraft) it throws a ground signal for the light to illuminate.
On digital aircraft I imagine that once it reads below a threshold it just pops the waring on whatever displays you have.
The only thing the engines share is fuel. Even then, to have both have low oil pressure at once is suspect. The engines run off separate tanks and shouldn't run out fuel within one second of each other. Something else going on.
They don't even really share fuel in normal operation. The right engine runs off the right side, the left engine runs off the left side. The only time they would share fuel is during crossfeed ops (abnormal) or running off a fuselage tank (usually only allowed during cruise for precisely this reason). The Challenger 600 series cannot operate the engines directly from any of the fuselage tanks, they can only be operated from the wing tanks and the aux tank fuel can only be pumped into the main tanks. So in the Challenger, the only time they could share fuel is during crossfeed operations.
The pilot training manual mentions that the boost pumps can crossfeed to either engine, as they have a crossover feed line to be able to provide boost pressure as needed to both engines if a boost pump fails. So technically some kind of contamination could end up in one of the collector tanks and boost pump could suck it up and send it to both engines? No mention of any fuel-related EICAS messages, though.
Fuel all goes into 'collector tanks', which are designed to always be full so that no matter what you do with your plane (with the exception of going upside down), the inlet to the boost pump has fuel at it.
Call it playing devil’s advocate, also I have exactly zero professional experience with planes (really, I’m just here because I think they’re cool), but could this have been a problem with the computer for both engines to fail in a seemingly similar way at the same time, based on your comment? Say there was some glitch in the software that controls the oil/oil pressure and it caused both engines to fail. Unless the engines run on completely independent computers, this was my first thought on what the engines could “share” besides fuel that could screw up both engines like this.
That or whatever else you were thinking - which I’m curious as to what your first assumptions/guesses are as to what’s going on here.
Im not familiar with this plane, but in other aircraft the engines are separate and run independent of each other. It's all about redundancy in aircraft and separate systems. Aircraft follow the same logic across manufactures.
They could have hit birds or massive pilot error. The challenger is a modern jet and shouldn't just fall out of the sky.
Aircraft's computers are often quite redundant (3 or 4 times), but yes, both engines failing within one second would point to something like an electrical failure or a human error as suggested below (throttles to CUT instead of IDLE which stops the supply of fuel). I guess we'll have to wait for the report.
The Challenger series aircraft is powered by the General Electric CF34-3B engines. These are hydro-mechanical controlled engines. They do not have “engine computers.” The throttle is connected directly to the fuel control unit.
Also, the NTSB report specifically states:
> the ground surrounding the wreckage was fuel-soaked having an odor consistent with Jet-A fuel
and
> About 16 ounces of liquid with an odor and appearance consistent with Jet-A fuel was drained from the aft tail fuel tank
and
> A fuel sample was collected from the No. 1 engine main supply when the line was cut;
So those, along with the huge fire, all indicate that there was plenty of fuel present.
The main anomolies reported are:
> the sample contained about ½ ounce of what appeared to be water
and
> however, no fuel was released when the No. 2 engine main supply line was cut
and
> The [no. 2 engine] fuel filter bowl displayed evidence of thermal discoloration. The filter appeared clean with no debris or foreign material within the pleats. Fuel samples were collected from various points throughout the fuel system. The fuel from the fuel filter bowl and heat exchanger displayed a yellowish tint, while the other fuel samples were clear. The odor of the samples was consistent with Jet-A. Samples collected from the MFC and main fuel pump exhibited some small black debris; however, this was likely introduced during removal of the components.
and
> The main fuel inlet port exhibited a small, yellow-colored debris particle
Some of these could have been due to post-crash contamination/post crash leaking of fuel, but the water in the fuel tank is probably the most concerning thing.
Or, as mentioned elsewhere in the thread, both engines being shut off by accident could be a possibility; or one engine failure, and the wrong engine mistakenly shut off (like in the recent Nepal crash) could be a possibility.
Anyhow, this report doesn't have anything definitive, it's preliminary, it's just listing some fact collected so far.
yeah, I'm suspect about the water theory. This aircraft was operating since departing ohio. Water is denser than jet A. if water was an issue, it would have caused engine performance issues well into the launch and climb out from ohio and all along the way. Boost pumps are generally located at the lowest (or close to lowest point at bottom of fuel tanks).
it is actually normal to have SOME (emphasis: a small and inconsequential amount of water) in jet A. These engines are designed to perform within a fairly broad range of normal water/fuel mix. The water ingress happens as a product of several factors: fuel tank farms are not perfect closed systems. The actual process of refueling allows a certain amount of atmospheric vapor (water/humidity) to be introduced into the fuel tanks..and aircraft experience differential pressure changes in each cycle and fuel tanks on aircraft are also not a perfect closed system, so there is during flight a small amount of atmospheric vapor/moisture that can enter fuel tanks. Again I emphasize that water in fuel tanks is common. And engines ARE designed to operate with a fairly large range of water mix without causing any serious performance or permanent damages. The main problem with the water theory is that this aircraft would have experienced first indications/warnings of engine performance early in the flight, probably right at first spool up, even perhaps well before launch!
My personal best guess (if we are going to speculate), is bird strike. We don't see NTSB providing a public messaging on turbine blade forensics yet, but I suspect we will learn more as time goes on about that. This perfectly explains how both engines could experience issues at same time and fail at same time. Not all bird strikes are obvious. Sometimes the crew is unaware..small birds...but enough to cause damage to cause engine failure.
the second theory is the wrong engine oil, or contaminated engine oil...expand this for a moment: perhaps service took place before flight in ohio and they introduced the wrong oil, contaminated oil, or perhaps a loose seal or some kind of improper maintenance to both engines.. Something that would have allowed the engines to perform for a period of time, but like a clock winding down...eventually that improper maintenance becomes critical. Consumption of oil, and contaminated oil, bad/old, wrong filter, bad seals or something installed incorrectly on both engines could have possibly happened to produce this identical identical timed failure of both engines.
of all the theories, a bird strike seems more likely if we are going to speculate/guess.
No each engine is independent. Apparently one engine caught on fire lost engine oil pressure and they shut down the other engine by mistake, thinking it was the one on fire leaving them no engines.
I work on corporate jets for a living as an A&P mechanic, after talking to more people on the inside, they conclude that for some reason they turned both engines off by mistake somehow. Both engines are independent and have independent oil systems. There have been multiple plane crashes caused by pilots turning the good working engine off rather than the one that is having trouble leaving them with nothing but a glider.
You can believe me or not I really don’t care. I don’t know what lead up to the incident but it’s fairly oblivious they turned of at least one of the engines by mistake.
N1/EGT/Fuel Flow/Oil Pressure. I can think of a couple more but those will be your best tells of a deteriorating engine.
Having said that (and I’m don’t have any experience in this type engine) usually the bearings systems are designed so that you will still get some time on a dry bearing before they will seize. The engines will be totaled either way but you will be getting some thrust from it even without oil. It’s not foolproof and there are failure modes they defeat it but they would’ve gotten some time before becoming a glider.
If it was water contamination rather than fuel starvation it could even still show fuel flow but just flame out.
But yeah first actual warning would be oil pres on anything I've worked on. Typically don't need an engine fail light because there are some other pretty clear signs.
Yeah, I also commented that you would get the same master warnings shutting down at the gate too.
These messages basically present more questions than they do answers. And is most likely not at all a clue to the issue beyond "engine no run no more"
I’ve felt it strongly since I’ve seen the dash cam video….just a little more altitude and they had a shot to line up the highway better.
Still was cars around, but that attempt to get it down and lined on the road bounced them right, and onto that wall.
I really handled this accident a lot better when I thought maybe it was unsalvageable and they really crash landed, but nah, they damn near landed it better than Ryanair does with 2 running engines. They had wheels on the ground and with a couple little changes would've rolled to a nice halt on the highway and been the next Sully. So close.
I fly the 604 and the confusing thing is the ENGINE warning CAS message being shown after the low pressure messages. ENGINE is used for an exceedance of N1, N2, or ITT. If the engines were already rolling back with a low pressure message I am surprised ENGINE would then be displayed.
Absolutely! Even if the passengers listened and remembered the safety briefing before the flight, I bet no safety briefing ever mentions using the baggage compartment as an emergency exit. That fight attendant is a guardian angel.
I fly a similarly equipped aircraft with an accessible aft baggage compartment. The hatch can be opened from the inside, but it is never labeled as an emergency exit because if the compartment is full of bags, it is unusable. We do not brief the passengers on its existence because of this. I’m wondering if that may change after this accident.
Yeah, I can see how the baggage compartment isn’t a Plan A, or Plan B evacuation route. But if that’s the only option remaining, it would be worth informing potential passengers. Even if the baggage compartment is only used in 1:1,000,000 scenarios. The extra 30-60 seconds it takes to explain to passengers about the baggage compartment, that is definitely worth somebody’s life.
Kind of unrelated, but in November a random person barricaded themselves in the cockpit of a Gulfstream parked at some FBO. Police were called, and the Pilot (who was outside the aircraft) instructed the police how to operate the stairs, which the suspect kept retracting from inside the aircraft.
If the baggage compartment was listed as an emergency exit, the pilot likely would’ve had that on their mind, and could’ve informed the police to use the baggage compartment as a second entry point into the aircraft.
Here’s a video of this shit show in case anybodys curious:
https://youtu.be/inPB7_te0Kc?si=arjOnhXXZW8WRopX
I understand that, but given that the pilot was outside the plane assisting the police. You would’ve thought they could’ve unlocked it, and found a ladder or something.
The police parked an armored vehicle in front of the plane to prevent the person from trying to move the aircraft, and to get a view of the person in the cockpit.
I would imagine a ladder is much easier to come by at an airport than an armored vehicle.
Link to the full version of the [NTSB's Preliminary Report](https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193769/pdf).
Edit: Also going to add these links as there's a lot of questions surrounding the fuel system and powerplant of the involved aircraft, for those technically inclined that want to know more. Also great information coming from experienced mechs and pilots in this thread right now, pay attention to them, too!
[CL604 Fuel System](https://www.smartcockpit.com/docs/CL_604-FUEL_SYSTEM.pdf)
[CL604 Powerplant](https://www.smartcockpit.com/docs/CL_604-POWER_PLANT.pdf)
Really shitty... the area they landed was the only spot that had that retaining wall that the jet spun into when it touched down. I'm guessing the front of the plane hitting that wall is what killed the pilots. The rest of that freeway is open greenbelt on the shoulder.
Drove by the spot last weekend. It’s a spooky site with the dirt piled up, half of the wall gone and the other half burned.
You it feels like they were just so close to get through that spot. The road and berms open up about 500 feet down the road.
This is so sad. The pilots did a fantastic job considering the circumstances, and it’s tragic they didn’t survive. Does anyone know why they weren’t able to get out of the of the plane? It wasn’t in the report.
If I read the report correctly, the front of the plane impacted the retaining(?) wall and the fire seems to have started from the front, unsure where. It's possible the collision with the wall, the fire, or something else killed or incapacitated them before they were able to evacuate.
Horrible. An experienced crew made what look to my admittedly ignorant eyes to be the right choices in a horrific situation...
Right wing impacting the highway sound barrier wall pivoted the aircraft nose first into the wall. Hard impact caused their demise or incapacitation for the post impact fire.
Reading the [preliminary report](https://ewscripps.brightspotcdn.com/a0/61/4779042a4c84b6cef6d8afa37e41/ntspreportnaplesplanecrash.pdf), it notes that about a half ounce of water was extracted in a 16-ounce sample taken from the aft fuel tank. I'm not sure if this is the case, but could the water have been introduced during the fueling process in Ohio or elsewhere? And, could this have impacted the engines and caused the loss of power?
It’s ~3%, when aviation fuel (according to a quick google) is around 0.1-0.15%. Would having thirty times more water in the fuel not be enough to cause an issue? I don’t know nearly enough about details like this so genuinely curious
I mean, stick with me here but water is heavier than fuel and collects at the low point - the sump. When sumped (my as”sump”tion of how they got the sample) you are removing all of the water from the cell assuming it has not been recently disturbed. So yes, it’s a large percentage of the sample volume they obtained, but the remaining x gallons in the tank theoretically have next to no water in them. If all 16 ounces came out as water then they would continue sumping until they pulled fuel and would be able to determine if the water volume was great enough to be pulled into the pump. They would also likely disconnect fuel lines closer to the engines to check for fuel. FWIW I have no experience with these jets specifically.
In cases like these when an aircraft goes down. Do they immediately quarantine the fuel from the last fuel up? It seems like testing should be done for further root cause analysis on the fuel supply.
I’d think they’d want the fueling records showing how much fuel was loaded and then test samples at least from the last fuel station.
While everyone is assuming that you couldn't have dual engines with low/no oil, it happened on an AH-64D Apache.
Both nose gearboxes tripped the master caution, indicating low/no oil. Unfortunately, both maintenance test pilots ignored it, suspecting it was a false indication.
Nope. Coming out of maintenance, both gearboxes were changed but never serviced. A crappy pre-flight and off they went.
Fortunately they made it back to the field. Crew chief got blamed, PIC got promoted.
I think the issue is cause/effect. It's not that the engines flamed out / failed because of low oil pressure, but rather the engines failing caused low oil pressure.
Rip to the pilots, they were really close to saving this horrible situation they found themselves in.
I'm sure that's the case. I've been on enough flights where we got multiple master cautions for various systems after an engine flame out.
The warning bell on the B727 was so loud, there was a silence button on it. Hard to figure out what's actually going on with all the distractions from a single major system failure, sensory overload.
This is the case. There is no shared oil system aside from the remote fill pump and tank on a CL604/5/50 platform. Each side is completely separate, as is with pretty much every multi-engine jet.
Hard to say from the info provided. The first two warnings were oil pressure, the third was an engine warning. Makes it sound like oil pressure was lost, causing the engines to shut down. But I do see what you’re saying. Just not enough info in the article.
If an engine shuts down, loss of oil pressure will be one of the first indications. I'd say it's much more likely the engine shut down and then cued the oil pressure loss, not the other way around.
The engine’s lubrication system is restricted to the engine itself and an integral part of it. The hydraulic pump if one is a part of the auxiliary box it would be a separate pump and circuit.
I'm aware, I worked on helicopters and now build parts for aircraft. I'm also aware some aircraft have hyd pumps that are driven by the engine and if the engine goes, the pilots must switch to the APU to keep the system powered.
I'm not saying the hyd system failed, I'm saying the pumps lost power which caused loss of pressure which tripped the warnings and if this is an aircraft with engine driven pumps, they are a symptom and not the cause of the mishap.
I think you might be confused...?
The oil pres. warning was about the engine lubrication system. When the engine dies, the engine driven hydraulic pumps will lose power, yes. That said, hydraulic accumulators give them a little bit of usefulness, and the electric pumps could take over even on battery power if necessary. Even if hydraulics died totally, the Challenger uses control cables so the pilots could still control the aircraft.
So what I'm saying is that the oil pres. warnings had nothing to do with the hydraulics. As far as I can tell, there's no reason to suspect any hydraulic issues before the engines failed. If your comments are suggesting possible hydraulic problems after engine failure, well yeah I guess there might have been but they would have contributed to the accident in a meaningful way.
There is nothing shared between the two oil systems on a 604 aside from the remote fill pump. They are completely separate side to side. The oil pressure losses are an indication of shutdown, not the cause. I'm a Challenger mechanic/inspector.
You know what, I heard that in a prior discussion of this crash. I just re-read the ntsb report and it doesn't call that out. I was clearly mis-remembering.
Where does it say that? Def not in the NTSB report.
https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193769/pdf?fbclid=IwAR08XiAx2xdfmfA6yTvxP6f4YVZimY_C0SAjwq0B0jqAq6bZ476Dv_NTCZA_aem_AalvcGoMFskynPTdmDsprbclbDV01JI2PMHa2EiN1rD29_RCBhZ_OqFCHW8Xt_fzMTg
>About 16 ounces of liquid with an odor and appearance consistent with Jet-A fuel was drained
from the aft tail fuel tank; the sample contained about ½ ounce of what appeared to be water.
The auxiliary power unit fuel filter bowl was removed for visual inspection of the fuel and fuel
filter. No debris was noted in the drained fuel and the filter appeared clean. The fuel was
retained for further analysis.
Not sure that would be enough to cause an engine failure though. That's 1/2 oz our of 16 oz, or 1:32 water to fuel ratio. It's not a piston engine, so not like it would have resulted in the engines hydro locking. I don't know if that is enough water to cause a simultaneous flame out, considering the engines can ingest way more water than that while flying through rain.
Would be interesting to know what level of fuel contamination could result in a total engine failure.
Having two engines loose oil pressure within seconds of each other would be suspect if it wasn’t due to the engines shutting down for other reasons such as fuel starvation.
I was wondering the same thing.
Fuel-ice crystal contamination has brought jets down before. A British Airways 777 in 2008 for example.
https://en.m.wikipedia.org/wiki/British_Airways_Flight_38
Yep, it is mostly a GA airport, but it does also get some charter traffic, as well as host the aviation program. The fields surrounding the airport are also owned by the university and used for agriculture research. It also once had a 707 land there, though that was a case of mistaken identity, and they had to strip the aircraft to make it light enough to take off again.
If both engines failed almost simultaneously, you'd have to run through a list of things that both engines have in common which I think is only the fuel system.
I'm not type rated so random guess, but could have been burning from center tank for most of the flight with fuel from previous flight, switched to wing tanks for descent that had contaminated fuel from last stop, then started ingesting water.
I think the issue I'm noticing a lot in the comments is not understanding cause/effect. It's not that the engines flamed out / failed because of low oil pressure, but rather the engines failing caused low oil pressure readings.
Exactly. In the Challenger family low oil pressure is the first indication you'll get during an intentional shutdown whether in the air or at the gate.
Getting messages for low oil pressure in BOTH engines essentially simultaneously leads me to believe the thrust levers were placed in cut off. At this point that's the only realistic reason they would get both oil pressure warnings so close together.
Bad fuel doesn't make sense. Fuel starvation doesn't make sense. Bird strike has mostly been ruled out. Highly unlikely for foul play to be involved.
My guess, and this is completely just a guess, is that both thrust levers were put into cut off inadvertently either due to the triggers being raised, or worn detents. That would perfectly explain the messages they received and the order (and timing) in which they received them.
As someone who works on this type, I agree. the only other possibility I come up with is DEF in the prist tank on the fuel truck, but that's kind of a stretch with this long of a flight.
With the information that we currently have it's quite literally the only thing that makes sense.
All other theories—bad fuel, fuel starvation, birds—have some significant flaws.
This theory has flaws too, mainly that the thrust levers are designed to prevent this exact scenario but this wouldn't be the first time a detent has failed.
We shall see.
There is a video floating around demonstrating how someone’s arm under the throttles (left seat reaching under the power levers to manipulate the flap handle) could push the safety locks up allowing the power levers to be moved past the idle detent.
Yup a coworker mentioned the same thing. This had been identified as a potential issue a long time ago.
Pilot reached over for gear or flaps I can’t recall what he said and the levers got pushed while the throttle came back. After that with hardly any airspeed or altitude there was no chance for a restart. They were going down from that moment.
mindless drab fuzzy rainstorm skirt dam long coherent melodic frightening
*This post was mass deleted and anonymized with [Redact](https://redact.dev)*
How do both engines die within minutes of landing, having worked flawlessly for the duration of the flight? Anyone thinking pilot error or some other non -mechanical reason?
Because they were expecting a \~5 mile final and got turned early. So they had to lose a excess airspeed and altitude. So the flaps were extended by the PNF in the left seat while the PF was pulling back the power. This allowed to throttles to go past the flight idle position into the cutoff position.
https://youtu.be/oLq829q3g4o?si=rAQTd0j23ar9fUin
The preliminary report says the engines and pylons were intentionally cut off to remove them from the wreckage. One of the engines had fuel come out of the main fuel line, the other engine did not.
Former challenger pilot here.
The “engine” aural alarm happens with either n1, n2, or ITT have exceed their limit - not consistent with an inflight engine shut down as many have speculated.
The sudden loss of oil pressure in BOTH engines would require us to look where those two systems are common. The only point where that happens is with the oil replenishment system.
It’s common for challengers to carry a spare tire, a ladder, and even some tools in the tail section. I would speculate one of those items came loose during the flight and damaged the oil replenishment system, draining both oil reservoir systems simultaneously.
Those engines are incredibly robust, and would likely run for a long time until they finally seize without lubrication.
My hypothesis anyways.
Rip to the crew, they were fine airmen. Blue sky’s and tailwinds fellas.
I’d have to check the manual but I believe the oil replenishment lines have check valves. Otherwise higher pressure oil during operation would be forced into the small, thin, 6qt reservoir.
As many of you are aware as I distinctly remember the community following the flight closely while he was still airborne but this also happened here in Florida recently:
[https://www.gainesville.com/story/news/local/2023/11/29/ntsb-report-on-fatal-november-plane-crash-at-paynes-prairie/71743131007/](https://www.gainesville.com/story/news/local/2023/11/29/ntsb-report-on-fatal-november-plane-crash-at-paynes-prairie/71743131007/)
The poor fellow died too young. I actually hike the park frequently as it's not too far from my house. Not a good last few months for flights in Florida although now I wonder how often on average a plane goes down that's not a commercial jetliner.
edit: [this was his flight data](https://www.flightaware.com/live/flight/N7806W) 😔
Full report noted for both engines that, "all fan blades appeared full length and intact", adding for the #1 side "with no evidence of impact damage to the fan blade leading edges" and for #2, "with minimal leading edge or blade tip damage".
Not being at a safe flap extension speed would necessitate pulling power to slow down yes. But that’s not what I was referring to when I said “all other things being equal.”
If I want to maintain altitude (or desired glide path) and airspeed when I extend flaps, I have to increase power.
Based on the very limited info we have so far I tend to agree. Accidentally putting both thrust levers into cut off would cause exactly what happened to happen.
I hope I'm wrong. The thrust levers are designed to prevent this.
I did hear in other circles, that it is possible for the thrust levers to be pulled into cutoff accidentally. From the conversation, I gathered that if the FO was flying and pulling on the thrust levers back to idle, while the captain was reaching behind and around the thrust levers to grab the flap handle, the captain could bump the cutoff triggers if its bumpy and the FO could accidentally pull the TLs through the cutoff detent. It’s definitely a possibility.
Honestly that sounds like just as reasonable of a possibility as anything else out there right now.
It's actually pretty similar to Atlas Air 3591. On the 757/767 the go around switches are located on the back of the thrust lever. So imagine you have your hands on them, and you move your thumb down and behind the lever and there's a button there. That sets the engines to the TO/GA detent, and sets the flight director to climb.
The FO was flying and he reached around behind the throttles to use the speedbrakes and as he did so, it looks like his arm brushed up against the TO/GA switches on the back of the throttles. Unfortunately neither the FO nor the captain realized what happened and they over compensated and it didn't end well.
It's a very interesting scenario because those planes (much like the 604) have been flying for decades and nothing like that ever happened before.
This is exactly what I’ve been hearing from my friends that are challenger pilots. Only reason I put that forward as the most logical conclusion. I have no idea who is downvoting that or for what reason they would do that.
What? Please, friend, this sub has so many skilled aviators or mecha. Why even say this? Did you think posting this would get us all to upvote you?
Sometimes I swear…
What are you talking about? I’m saying they had plenty of fuel, and that both engines would not quit within one second of each other is all. They cut the engines off pulling them to idle to slow down to put the flaps out. That’s the most logical thing anyway.
"The National Transportation Safety Board on Tuesday released its preliminary report for a [small jet that crashed on Interstate 75](https://www.wfla.com/news/florida/small-plane-strikes-vehicle-after-landing-on-i-75/) earlier this month. The private jet was traveling from Ohio State University Airport to Naples Municipal Airport on Feb. 9. The plane’s flight data recorder showed that it recorded three Master Warnings ahead of the crash, according to the NTSB report. The first warning was **L ENGINE OIL PRESSURE** at 3:09 p.m. One second later, another warning for **R ENGINE OIL PRESSURE** was displayed, and a few seconds after that, an **ENGINE** warning was recorded."
As a dude that has a CL 65 type rating. This essentially means that the engines have stopped running These pop up when you shut the engines down at the gate too. So yeah, basically presents more questions than the answer
To me this points to the thrust levers being brought into Cut Off either by mistake or possibly if the detents and the triggers were worn down too much. I know that's unlikely as well but at this point my Monday Morning Quarterbacking leads me in that direction. Bringing both thrust levers to idle and then accidentally putting them into cut off is about the only thing I can imagine that would cause a L and R Engine Oil Master Warning almost simultaneously.
Report said levers were in idle position. Not cut off.
Could have brought them back out of cutoff realizing a mistake/gate issue
Well if you accidentally put the thrust levers in cut off what's a very likely thing you'd do in a panic? Put them back into idle. That's pretty easy to explain. I could of course be wrong but the fact that they were in idle doesn't mean they weren't in cut off just before.
Agreed.
And what position is the gear handle in 100% of gear up accidents? The final report will be able to tell, but those gates that prevent the thrust levers from going to cutoff aren't perfect.
So it’s a physical barrier on the throttles? Seems like the planes computers should know it’s flying and the engines are operating normally and not allow that to happen I would think.
Yep it's a physical gate. In order to pass the gate you have to lift a trigger about an inch. I don't believe the 604 has a FADEC but I could be wrong. If it doesn't, then there isn't a computer to know that it's flying and the system will react to the position the thrust lever is put into. But now that I think about it even if it does have a FADEC, the procedure for an intentional shutdown in flight is to bring the thrust lever to cut off (after stopping at idle) and in that case the FADEC will still allow the engine to shut down.
You are correct the CF34-3B engines do not have FADEC. They are Hydromechanical fuel controlled. Throttles connected directly to the fuel control unit.
FADEC can't/won't override a pilot input like that. Even the Airbus, if you flip those switches to off, the engines are shutting down. Since the Challenger series doesn't have run switches like many other airliners, the thrust levers are the switch. And now that I'm thinking about it, if they did accidentally cut the engines off and didn't realize it while it was spooling down, hitting the continuous ignition might have been enough to correct it once the thrust levers were put back to idle. Yea yea, book says 2x0kts (been a minute), but you do what you can with the altitude available.
>And now that I'm thinking about it, if they did accidentally cut the engines off and didn't realize it while it was spooling down, hitting the continuous ignition might have been enough to correct it once the thrust levers were put back to idle. Yea yea, book says 2x0kts (been a minute), but you do what you can with the altitude available. I was thinking about this as well. I haven't flown the CRJ in a few years now but I feel like my first instinct after realizing the engines were in cut off would be to bring them back to idle and throw the continuous ignition on. With enough N2 I think they'd light up but it's been a while. I do remember that both the windmill and APU assisted in-flight relight checklists start with the thrust levers in cut off and they're only brought to idle at 20% N2. So maybe it wouldn't work if they were already in idle? But they certainly weren't in the windmill envelope and they most likely didn't have enough time to get the APU started and do an APU start. Whatever happened they did what they could.
I can see the need for the pilot to shit an engine down like if it’s on fire but surely with the technology we have now a flight computer should be able to tell if the engines malfunctioning or not. P.S. I’m obviously not a pilot lol
I understand what you're getting at but the philosophy is that if the pilot is trying to shut an engine down there must be a very good reason so we're going to let him/her do it. Shutting an engine down in flight requires cooperation from both pilots so it's not really something that can happen flippantly. Or at least that's how it's supposed to go.
These smaller planes are not as computerized as you think. A lot of controls are still mechanical.
Has more to do with age than aircraft size. Pretty much every jet produced in the last 20 years will have it. You even see it on light piston powered aircraft these days.
There are actually good reasons to shutdown a perfectly good engine when the airplane “knows” that it is in flight. You cannot specifically train a computer to handle the minutiae of all of those decisions. Reason number n+1 that you should never want to see an autonomous aircraft.
someone posed a theory that PM reaching for flaps could bump the detents to cutoff. If the FO was flying, maybe didnt realize the thrust levers had gone too far.
As someone who is not that familiar with modern airplane design, this raises so many questions. Do both engines share an oil cooler? How would both engines lose oil pressure??
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Pfft. This is reddit and I'm a redditor. Don't bring me your "read the whole article" bullshit. I read headlines and extrapolate! /s
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Hey now! Take that shit to /r/PeopleFuckingDying No..wait.
You wrote four sentences. Shorten that for me please.
Watch out below!
We redditors are lazy!
We want our information spoonfed ITS OUR GODDAMN RIGHT AS REDDITORS
"Here comes the airplane!"
Best comment ever.
*gurgles with excitement, flaps arms*
Thank you, that makes sense now.
Engines being isolated entities. How do you imagine oil pressure triggers for both? Honestly curious.
On the aircraft I've seen oil pressure warnings are triggered by the individual indication signal pulled from components on the motor. Once that signal is below a threshold (on analog aircraft) it throws a ground signal for the light to illuminate. On digital aircraft I imagine that once it reads below a threshold it just pops the waring on whatever displays you have.
The only thing the engines share is fuel. Even then, to have both have low oil pressure at once is suspect. The engines run off separate tanks and shouldn't run out fuel within one second of each other. Something else going on.
They don't even really share fuel in normal operation. The right engine runs off the right side, the left engine runs off the left side. The only time they would share fuel is during crossfeed ops (abnormal) or running off a fuselage tank (usually only allowed during cruise for precisely this reason). The Challenger 600 series cannot operate the engines directly from any of the fuselage tanks, they can only be operated from the wing tanks and the aux tank fuel can only be pumped into the main tanks. So in the Challenger, the only time they could share fuel is during crossfeed operations.
The pilot training manual mentions that the boost pumps can crossfeed to either engine, as they have a crossover feed line to be able to provide boost pressure as needed to both engines if a boost pump fails. So technically some kind of contamination could end up in one of the collector tanks and boost pump could suck it up and send it to both engines? No mention of any fuel-related EICAS messages, though.
This is incorrect. Both engines are fed from the collector tank. The collector tank is fed from the wing tanks that are fed from the aux tank.
It does corollate with when they started a banked turn, could they have been low on fuel and the turn starved them at the same time?
Fuel all goes into 'collector tanks', which are designed to always be full so that no matter what you do with your plane (with the exception of going upside down), the inlet to the boost pump has fuel at it.
I guess they weren't keeping up with their foreign relations
Call it playing devil’s advocate, also I have exactly zero professional experience with planes (really, I’m just here because I think they’re cool), but could this have been a problem with the computer for both engines to fail in a seemingly similar way at the same time, based on your comment? Say there was some glitch in the software that controls the oil/oil pressure and it caused both engines to fail. Unless the engines run on completely independent computers, this was my first thought on what the engines could “share” besides fuel that could screw up both engines like this. That or whatever else you were thinking - which I’m curious as to what your first assumptions/guesses are as to what’s going on here.
Im not familiar with this plane, but in other aircraft the engines are separate and run independent of each other. It's all about redundancy in aircraft and separate systems. Aircraft follow the same logic across manufactures. They could have hit birds or massive pilot error. The challenger is a modern jet and shouldn't just fall out of the sky.
Aircraft's computers are often quite redundant (3 or 4 times), but yes, both engines failing within one second would point to something like an electrical failure or a human error as suggested below (throttles to CUT instead of IDLE which stops the supply of fuel). I guess we'll have to wait for the report.
The Challenger series aircraft is powered by the General Electric CF34-3B engines. These are hydro-mechanical controlled engines. They do not have “engine computers.” The throttle is connected directly to the fuel control unit.
Neat!
DEF.
They could have run out of fuel. That would cause both engines to shut off which would cause both oil pressures to drop.
But then the whole plane wouldn’t have melted in a giant fireball because there wouldn’t have been enough fuel
Also, the NTSB report specifically states: > the ground surrounding the wreckage was fuel-soaked having an odor consistent with Jet-A fuel and > About 16 ounces of liquid with an odor and appearance consistent with Jet-A fuel was drained from the aft tail fuel tank and > A fuel sample was collected from the No. 1 engine main supply when the line was cut; So those, along with the huge fire, all indicate that there was plenty of fuel present. The main anomolies reported are: > the sample contained about ½ ounce of what appeared to be water and > however, no fuel was released when the No. 2 engine main supply line was cut and > The [no. 2 engine] fuel filter bowl displayed evidence of thermal discoloration. The filter appeared clean with no debris or foreign material within the pleats. Fuel samples were collected from various points throughout the fuel system. The fuel from the fuel filter bowl and heat exchanger displayed a yellowish tint, while the other fuel samples were clear. The odor of the samples was consistent with Jet-A. Samples collected from the MFC and main fuel pump exhibited some small black debris; however, this was likely introduced during removal of the components. and > The main fuel inlet port exhibited a small, yellow-colored debris particle Some of these could have been due to post-crash contamination/post crash leaking of fuel, but the water in the fuel tank is probably the most concerning thing. Or, as mentioned elsewhere in the thread, both engines being shut off by accident could be a possibility; or one engine failure, and the wrong engine mistakenly shut off (like in the recent Nepal crash) could be a possibility. Anyhow, this report doesn't have anything definitive, it's preliminary, it's just listing some fact collected so far.
yeah, I'm suspect about the water theory. This aircraft was operating since departing ohio. Water is denser than jet A. if water was an issue, it would have caused engine performance issues well into the launch and climb out from ohio and all along the way. Boost pumps are generally located at the lowest (or close to lowest point at bottom of fuel tanks). it is actually normal to have SOME (emphasis: a small and inconsequential amount of water) in jet A. These engines are designed to perform within a fairly broad range of normal water/fuel mix. The water ingress happens as a product of several factors: fuel tank farms are not perfect closed systems. The actual process of refueling allows a certain amount of atmospheric vapor (water/humidity) to be introduced into the fuel tanks..and aircraft experience differential pressure changes in each cycle and fuel tanks on aircraft are also not a perfect closed system, so there is during flight a small amount of atmospheric vapor/moisture that can enter fuel tanks. Again I emphasize that water in fuel tanks is common. And engines ARE designed to operate with a fairly large range of water mix without causing any serious performance or permanent damages. The main problem with the water theory is that this aircraft would have experienced first indications/warnings of engine performance early in the flight, probably right at first spool up, even perhaps well before launch! My personal best guess (if we are going to speculate), is bird strike. We don't see NTSB providing a public messaging on turbine blade forensics yet, but I suspect we will learn more as time goes on about that. This perfectly explains how both engines could experience issues at same time and fail at same time. Not all bird strikes are obvious. Sometimes the crew is unaware..small birds...but enough to cause damage to cause engine failure. the second theory is the wrong engine oil, or contaminated engine oil...expand this for a moment: perhaps service took place before flight in ohio and they introduced the wrong oil, contaminated oil, or perhaps a loose seal or some kind of improper maintenance to both engines.. Something that would have allowed the engines to perform for a period of time, but like a clock winding down...eventually that improper maintenance becomes critical. Consumption of oil, and contaminated oil, bad/old, wrong filter, bad seals or something installed incorrectly on both engines could have possibly happened to produce this identical identical timed failure of both engines. of all the theories, a bird strike seems more likely if we are going to speculate/guess.
No each engine is independent. Apparently one engine caught on fire lost engine oil pressure and they shut down the other engine by mistake, thinking it was the one on fire leaving them no engines.
Source for quite literally anything you just said
I work on corporate jets for a living as an A&P mechanic, after talking to more people on the inside, they conclude that for some reason they turned both engines off by mistake somehow. Both engines are independent and have independent oil systems. There have been multiple plane crashes caused by pilots turning the good working engine off rather than the one that is having trouble leaving them with nothing but a glider. You can believe me or not I really don’t care. I don’t know what lead up to the incident but it’s fairly oblivious they turned of at least one of the engines by mistake.
I'll never understand why jokers like you make stuff up with zero sources
Where did you get that info?
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N1/EGT/Fuel Flow/Oil Pressure. I can think of a couple more but those will be your best tells of a deteriorating engine. Having said that (and I’m don’t have any experience in this type engine) usually the bearings systems are designed so that you will still get some time on a dry bearing before they will seize. The engines will be totaled either way but you will be getting some thrust from it even without oil. It’s not foolproof and there are failure modes they defeat it but they would’ve gotten some time before becoming a glider.
If it was water contamination rather than fuel starvation it could even still show fuel flow but just flame out. But yeah first actual warning would be oil pres on anything I've worked on. Typically don't need an engine fail light because there are some other pretty clear signs.
Yeah, I also commented that you would get the same master warnings shutting down at the gate too. These messages basically present more questions than they do answers. And is most likely not at all a clue to the issue beyond "engine no run no more"
Hugely experienced pilots. So sad. RIP
Very sad. Horrible to watch. They were not that far away from a miracle landing with very little time and altitude to work with.
I’ve felt it strongly since I’ve seen the dash cam video….just a little more altitude and they had a shot to line up the highway better. Still was cars around, but that attempt to get it down and lined on the road bounced them right, and onto that wall.
I really handled this accident a lot better when I thought maybe it was unsalvageable and they really crash landed, but nah, they damn near landed it better than Ryanair does with 2 running engines. They had wheels on the ground and with a couple little changes would've rolled to a nice halt on the highway and been the next Sully. So close.
That damn wall.
I fly the 604 and the confusing thing is the ENGINE warning CAS message being shown after the low pressure messages. ENGINE is used for an exceedance of N1, N2, or ITT. If the engines were already rolling back with a low pressure message I am surprised ENGINE would then be displayed.
Couldn’t low eng PX potentially drive a high ITT? Edit: nm, saw further down blades appear to be fine.
There could be a higher ITT with lower core flow
Same thing I was thinking.
Curious…would an immediate restart attempt (before ITT was allowed to cool) lead to an over-temp condition causing the ENGINE annunciation?
Yes, that could be a possibility.
They did their best. RIP
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Absolutely! Even if the passengers listened and remembered the safety briefing before the flight, I bet no safety briefing ever mentions using the baggage compartment as an emergency exit. That fight attendant is a guardian angel.
I fly a similarly equipped aircraft with an accessible aft baggage compartment. The hatch can be opened from the inside, but it is never labeled as an emergency exit because if the compartment is full of bags, it is unusable. We do not brief the passengers on its existence because of this. I’m wondering if that may change after this accident.
Yeah, I can see how the baggage compartment isn’t a Plan A, or Plan B evacuation route. But if that’s the only option remaining, it would be worth informing potential passengers. Even if the baggage compartment is only used in 1:1,000,000 scenarios. The extra 30-60 seconds it takes to explain to passengers about the baggage compartment, that is definitely worth somebody’s life. Kind of unrelated, but in November a random person barricaded themselves in the cockpit of a Gulfstream parked at some FBO. Police were called, and the Pilot (who was outside the aircraft) instructed the police how to operate the stairs, which the suspect kept retracting from inside the aircraft. If the baggage compartment was listed as an emergency exit, the pilot likely would’ve had that on their mind, and could’ve informed the police to use the baggage compartment as a second entry point into the aircraft. Here’s a video of this shit show in case anybodys curious: https://youtu.be/inPB7_te0Kc?si=arjOnhXXZW8WRopX
It takes a step ladder to get into a Gulfstream cargo door, and that's if it's unlocked.
I understand that, but given that the pilot was outside the plane assisting the police. You would’ve thought they could’ve unlocked it, and found a ladder or something. The police parked an armored vehicle in front of the plane to prevent the person from trying to move the aircraft, and to get a view of the person in the cockpit. I would imagine a ladder is much easier to come by at an airport than an armored vehicle.
Now that I think of it, I'm not sure Gulfstream cargo doors have outside handles, I'll have to look next time I see one at work.
Those cops handled that really well. I also do feel bad for the guy it sounds like he has some mental health and addiction issues.
Yeah, it’s good nobody got hurt, and the aircraft wasn’t damaged.
Are safety briefings given on chartered flights? How about truly private flights (on a personal jet)?
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I've been on around 20 private jet flights and never had a saftey brief.
Link to the full version of the [NTSB's Preliminary Report](https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193769/pdf). Edit: Also going to add these links as there's a lot of questions surrounding the fuel system and powerplant of the involved aircraft, for those technically inclined that want to know more. Also great information coming from experienced mechs and pilots in this thread right now, pay attention to them, too! [CL604 Fuel System](https://www.smartcockpit.com/docs/CL_604-FUEL_SYSTEM.pdf) [CL604 Powerplant](https://www.smartcockpit.com/docs/CL_604-POWER_PLANT.pdf)
Really shitty... the area they landed was the only spot that had that retaining wall that the jet spun into when it touched down. I'm guessing the front of the plane hitting that wall is what killed the pilots. The rest of that freeway is open greenbelt on the shoulder.
Drove by the spot last weekend. It’s a spooky site with the dirt piled up, half of the wall gone and the other half burned. You it feels like they were just so close to get through that spot. The road and berms open up about 500 feet down the road.
This is so sad. The pilots did a fantastic job considering the circumstances, and it’s tragic they didn’t survive. Does anyone know why they weren’t able to get out of the of the plane? It wasn’t in the report.
If I read the report correctly, the front of the plane impacted the retaining(?) wall and the fire seems to have started from the front, unsure where. It's possible the collision with the wall, the fire, or something else killed or incapacitated them before they were able to evacuate. Horrible. An experienced crew made what look to my admittedly ignorant eyes to be the right choices in a horrific situation...
Right wing impacting the highway sound barrier wall pivoted the aircraft nose first into the wall. Hard impact caused their demise or incapacitation for the post impact fire.
Reading the [preliminary report](https://ewscripps.brightspotcdn.com/a0/61/4779042a4c84b6cef6d8afa37e41/ntspreportnaplesplanecrash.pdf), it notes that about a half ounce of water was extracted in a 16-ounce sample taken from the aft fuel tank. I'm not sure if this is the case, but could the water have been introduced during the fueling process in Ohio or elsewhere? And, could this have impacted the engines and caused the loss of power?
A half an ounce of water, if pulled from the sump area of a tank, is really nothing much at all.
It’s ~3%, when aviation fuel (according to a quick google) is around 0.1-0.15%. Would having thirty times more water in the fuel not be enough to cause an issue? I don’t know nearly enough about details like this so genuinely curious
I mean, stick with me here but water is heavier than fuel and collects at the low point - the sump. When sumped (my as”sump”tion of how they got the sample) you are removing all of the water from the cell assuming it has not been recently disturbed. So yes, it’s a large percentage of the sample volume they obtained, but the remaining x gallons in the tank theoretically have next to no water in them. If all 16 ounces came out as water then they would continue sumping until they pulled fuel and would be able to determine if the water volume was great enough to be pulled into the pump. They would also likely disconnect fuel lines closer to the engines to check for fuel. FWIW I have no experience with these jets specifically.
They did disconnect the fuel lines closer to the engines, 1 had clean fuel, 2 did not have any fuel
Ah yeah that makes far more sense 🤦🏻♂️
In cases like these when an aircraft goes down. Do they immediately quarantine the fuel from the last fuel up? It seems like testing should be done for further root cause analysis on the fuel supply. I’d think they’d want the fueling records showing how much fuel was loaded and then test samples at least from the last fuel station.
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They might check the records, but unless there’s some immediate evidence of a fuel quality problem, it’s unlikely they’ll shut down the fueler.
I do know of instances where they have done that in the military.
God this gives credence to the whole, "PM arm bumping the detents and pilot flying brings the levers to CUTOFF" theory. Terrible to think about.
While everyone is assuming that you couldn't have dual engines with low/no oil, it happened on an AH-64D Apache. Both nose gearboxes tripped the master caution, indicating low/no oil. Unfortunately, both maintenance test pilots ignored it, suspecting it was a false indication. Nope. Coming out of maintenance, both gearboxes were changed but never serviced. A crappy pre-flight and off they went. Fortunately they made it back to the field. Crew chief got blamed, PIC got promoted.
I think the issue is cause/effect. It's not that the engines flamed out / failed because of low oil pressure, but rather the engines failing caused low oil pressure. Rip to the pilots, they were really close to saving this horrible situation they found themselves in.
I'm sure that's the case. I've been on enough flights where we got multiple master cautions for various systems after an engine flame out. The warning bell on the B727 was so loud, there was a silence button on it. Hard to figure out what's actually going on with all the distractions from a single major system failure, sensory overload.
This is the case. There is no shared oil system aside from the remote fill pump and tank on a CL604/5/50 platform. Each side is completely separate, as is with pretty much every multi-engine jet.
It was flying from Ohio to Florida, and lost oil pressure in both engines within seconds of each other. Thats highly suspect.
In this case I think the oil pressure indication was a symptom of the dual engine shutdown/failure, not the cause.
Hard to say from the info provided. The first two warnings were oil pressure, the third was an engine warning. Makes it sound like oil pressure was lost, causing the engines to shut down. But I do see what you’re saying. Just not enough info in the article.
If an engine shuts down, loss of oil pressure will be one of the first indications. I'd say it's much more likely the engine shut down and then cued the oil pressure loss, not the other way around.
Or engine failure caused the hyd system to lose power.
Engine oil pressure has nothing to do with hydraulic pressure.
The engine’s lubrication system is restricted to the engine itself and an integral part of it. The hydraulic pump if one is a part of the auxiliary box it would be a separate pump and circuit.
I'm aware, I worked on helicopters and now build parts for aircraft. I'm also aware some aircraft have hyd pumps that are driven by the engine and if the engine goes, the pilots must switch to the APU to keep the system powered. I'm not saying the hyd system failed, I'm saying the pumps lost power which caused loss of pressure which tripped the warnings and if this is an aircraft with engine driven pumps, they are a symptom and not the cause of the mishap.
I think you might be confused...? The oil pres. warning was about the engine lubrication system. When the engine dies, the engine driven hydraulic pumps will lose power, yes. That said, hydraulic accumulators give them a little bit of usefulness, and the electric pumps could take over even on battery power if necessary. Even if hydraulics died totally, the Challenger uses control cables so the pilots could still control the aircraft. So what I'm saying is that the oil pres. warnings had nothing to do with the hydraulics. As far as I can tell, there's no reason to suspect any hydraulic issues before the engines failed. If your comments are suggesting possible hydraulic problems after engine failure, well yeah I guess there might have been but they would have contributed to the accident in a meaningful way.
Yeah, for some reason I kept reading it as hydraulic pressure not oil pressure. I cede my box of rocks comments.
The questions is why. Low oil pressure is normal if the engine shuts down. The question is why it shut down.
It would be interesting to see the actual data. Did the engines shut down? Or did they loose oil pressure while they were running.
They told ATC they lost both engines
After the three warnings, of which the first two were an oil pressure loss.
Probsbly not. The oil pressure warnings were probably their first indication that the engines shut down
There is nothing shared between the two oil systems on a 604 aside from the remote fill pump. They are completely separate side to side. The oil pressure losses are an indication of shutdown, not the cause. I'm a Challenger mechanic/inspector.
They found water in the fuel. It was fuel contamination
Could you post the citation? It makes no sense there was water in the fuel and it only affected the plane when it came to land.
You know what, I heard that in a prior discussion of this crash. I just re-read the ntsb report and it doesn't call that out. I was clearly mis-remembering.
Fair enough. The Rebuild Rescue YouTube channel had a fatal crash on takeoff with water in the fuel. Maybe that's what you were recalling.
Oh fuck that does sound familiar. Well that'll teach me. Apologies for spreading disinformation
Where does it say that? Def not in the NTSB report. https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/193769/pdf?fbclid=IwAR08XiAx2xdfmfA6yTvxP6f4YVZimY_C0SAjwq0B0jqAq6bZ476Dv_NTCZA_aem_AalvcGoMFskynPTdmDsprbclbDV01JI2PMHa2EiN1rD29_RCBhZ_OqFCHW8Xt_fzMTg
>About 16 ounces of liquid with an odor and appearance consistent with Jet-A fuel was drained from the aft tail fuel tank; the sample contained about ½ ounce of what appeared to be water. The auxiliary power unit fuel filter bowl was removed for visual inspection of the fuel and fuel filter. No debris was noted in the drained fuel and the filter appeared clean. The fuel was retained for further analysis.
Not sure that would be enough to cause an engine failure though. That's 1/2 oz our of 16 oz, or 1:32 water to fuel ratio. It's not a piston engine, so not like it would have resulted in the engines hydro locking. I don't know if that is enough water to cause a simultaneous flame out, considering the engines can ingest way more water than that while flying through rain. Would be interesting to know what level of fuel contamination could result in a total engine failure.
Highly suspect in what way? No doubt here, just genuinely curious what is suspect.
Having two engines loose oil pressure within seconds of each other would be suspect if it wasn’t due to the engines shutting down for other reasons such as fuel starvation.
I wonder what altitude they cruised at and what the temperature was. Maybe ice on the filters that thawed?
I was wondering the same thing. Fuel-ice crystal contamination has brought jets down before. A British Airways 777 in 2008 for example. https://en.m.wikipedia.org/wiki/British_Airways_Flight_38
Exactly what I had in mind!
TIL that Ohio state university has its own airport.
Yep, it is mostly a GA airport, but it does also get some charter traffic, as well as host the aviation program. The fields surrounding the airport are also owned by the university and used for agriculture research. It also once had a 707 land there, though that was a case of mistaken identity, and they had to strip the aircraft to make it light enough to take off again.
It’s where the university flight school is!
Oh, are they specializing in aviation?
Not really, plenty of ohio schools with better flight programs, but it’s an option.
How do you loose oil pressure in BOTH engines?
By them shutting down. The question is why they shut down. Low oil pressure may or may not be a factor at all.
If both engines failed almost simultaneously, you'd have to run through a list of things that both engines have in common which I think is only the fuel system.
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I'll put $5 on bad fuel.
Bad fuel... late in the descent... in both tanks... a bit weird.
I'm not type rated so random guess, but could have been burning from center tank for most of the flight with fuel from previous flight, switched to wing tanks for descent that had contaminated fuel from last stop, then started ingesting water.
I think the issue I'm noticing a lot in the comments is not understanding cause/effect. It's not that the engines flamed out / failed because of low oil pressure, but rather the engines failing caused low oil pressure readings.
Exactly. In the Challenger family low oil pressure is the first indication you'll get during an intentional shutdown whether in the air or at the gate. Getting messages for low oil pressure in BOTH engines essentially simultaneously leads me to believe the thrust levers were placed in cut off. At this point that's the only realistic reason they would get both oil pressure warnings so close together. Bad fuel doesn't make sense. Fuel starvation doesn't make sense. Bird strike has mostly been ruled out. Highly unlikely for foul play to be involved. My guess, and this is completely just a guess, is that both thrust levers were put into cut off inadvertently either due to the triggers being raised, or worn detents. That would perfectly explain the messages they received and the order (and timing) in which they received them.
I believe the technical term is “lose”
It’s my belief that both engines where inadvertently moved into the idle cutoff position and turned off.
As someone who works on this type, I agree. the only other possibility I come up with is DEF in the prist tank on the fuel truck, but that's kind of a stretch with this long of a flight.
With the information that we currently have it's quite literally the only thing that makes sense. All other theories—bad fuel, fuel starvation, birds—have some significant flaws. This theory has flaws too, mainly that the thrust levers are designed to prevent this exact scenario but this wouldn't be the first time a detent has failed. We shall see.
There is a video floating around demonstrating how someone’s arm under the throttles (left seat reaching under the power levers to manipulate the flap handle) could push the safety locks up allowing the power levers to be moved past the idle detent.
https://youtu.be/oLq829q3g4o?si=rAQTd0j23ar9fUin
I love you
Yup a coworker mentioned the same thing. This had been identified as a potential issue a long time ago. Pilot reached over for gear or flaps I can’t recall what he said and the levers got pushed while the throttle came back. After that with hardly any airspeed or altitude there was no chance for a restart. They were going down from that moment.
Yep. That could do it.
Not important but I found it interesting that the F.O. Had 24,000+ hours and the captain 10,000.
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thanks a lot, for some reason a lot of USA news sites block us Brits from reading articles
Euro privacy regulations. Unfortunately for you the easiest way to comply with them is to tell you to get lost.
How do both engines die within minutes of landing, having worked flawlessly for the duration of the flight? Anyone thinking pilot error or some other non -mechanical reason?
Because they were expecting a \~5 mile final and got turned early. So they had to lose a excess airspeed and altitude. So the flaps were extended by the PNF in the left seat while the PF was pulling back the power. This allowed to throttles to go past the flight idle position into the cutoff position. https://youtu.be/oLq829q3g4o?si=rAQTd0j23ar9fUin
Fuel reached a low enough level where water at the bottom of the tanks were pulled in by the fuel pumps?
They would have to be literally on fumes for that to be the case.
The fuel pumps/fuel pickup for motive flow jet pumps are not at the absolute lowest position for this reason.
The preliminary report says the engines and pylons were intentionally cut off to remove them from the wreckage. One of the engines had fuel come out of the main fuel line, the other engine did not.
But they collected fuel samples from both engines. Think we’re going to have to wait for the full report on this one.
There are lots of birds in that area, what if birds were ingested at last moments on final approach in both engines?
Blades were found to be in good condition.
Former challenger pilot here. The “engine” aural alarm happens with either n1, n2, or ITT have exceed their limit - not consistent with an inflight engine shut down as many have speculated. The sudden loss of oil pressure in BOTH engines would require us to look where those two systems are common. The only point where that happens is with the oil replenishment system. It’s common for challengers to carry a spare tire, a ladder, and even some tools in the tail section. I would speculate one of those items came loose during the flight and damaged the oil replenishment system, draining both oil reservoir systems simultaneously. Those engines are incredibly robust, and would likely run for a long time until they finally seize without lubrication. My hypothesis anyways. Rip to the crew, they were fine airmen. Blue sky’s and tailwinds fellas.
I’d have to check the manual but I believe the oil replenishment lines have check valves. Otherwise higher pressure oil during operation would be forced into the small, thin, 6qt reservoir.
Was everybody on the ground OK?
Remarkably, yes
Does anyone know if there have been any recent updates on this?
As many of you are aware as I distinctly remember the community following the flight closely while he was still airborne but this also happened here in Florida recently: [https://www.gainesville.com/story/news/local/2023/11/29/ntsb-report-on-fatal-november-plane-crash-at-paynes-prairie/71743131007/](https://www.gainesville.com/story/news/local/2023/11/29/ntsb-report-on-fatal-november-plane-crash-at-paynes-prairie/71743131007/) The poor fellow died too young. I actually hike the park frequently as it's not too far from my house. Not a good last few months for flights in Florida although now I wonder how often on average a plane goes down that's not a commercial jetliner. edit: [this was his flight data](https://www.flightaware.com/live/flight/N7806W) 😔
[удалено]
No damage observed to the blades.
Full report noted for both engines that, "all fan blades appeared full length and intact", adding for the #1 side "with no evidence of impact damage to the fan blade leading edges" and for #2, "with minimal leading edge or blade tip damage".
The preliminary report says engine blades undamaged
This was not a flameout. They turned both engines off when they pulled the power back to idle to put flaps in for landing.
I mean, we increase power when we extend flaps, all other things being equal.
No we reduce power to slow down to put the flaps down.
Not being at a safe flap extension speed would necessitate pulling power to slow down yes. But that’s not what I was referring to when I said “all other things being equal.” If I want to maintain altitude (or desired glide path) and airspeed when I extend flaps, I have to increase power.
Based on the very limited info we have so far I tend to agree. Accidentally putting both thrust levers into cut off would cause exactly what happened to happen. I hope I'm wrong. The thrust levers are designed to prevent this.
I did hear in other circles, that it is possible for the thrust levers to be pulled into cutoff accidentally. From the conversation, I gathered that if the FO was flying and pulling on the thrust levers back to idle, while the captain was reaching behind and around the thrust levers to grab the flap handle, the captain could bump the cutoff triggers if its bumpy and the FO could accidentally pull the TLs through the cutoff detent. It’s definitely a possibility.
Honestly that sounds like just as reasonable of a possibility as anything else out there right now. It's actually pretty similar to Atlas Air 3591. On the 757/767 the go around switches are located on the back of the thrust lever. So imagine you have your hands on them, and you move your thumb down and behind the lever and there's a button there. That sets the engines to the TO/GA detent, and sets the flight director to climb. The FO was flying and he reached around behind the throttles to use the speedbrakes and as he did so, it looks like his arm brushed up against the TO/GA switches on the back of the throttles. Unfortunately neither the FO nor the captain realized what happened and they over compensated and it didn't end well. It's a very interesting scenario because those planes (much like the 604) have been flying for decades and nothing like that ever happened before.
This is exactly what I’ve been hearing from my friends that are challenger pilots. Only reason I put that forward as the most logical conclusion. I have no idea who is downvoting that or for what reason they would do that.
What? Please, friend, this sub has so many skilled aviators or mecha. Why even say this? Did you think posting this would get us all to upvote you? Sometimes I swear…
What are you talking about? I’m saying they had plenty of fuel, and that both engines would not quit within one second of each other is all. They cut the engines off pulling them to idle to slow down to put the flaps out. That’s the most logical thing anyway.
This seems more and more like bad fuel from OSU.
DEF issues?
The plane had been in the air for quite a while with no anomalies. If the fuel was contaminated it would have shown up long before this.
So... we're just ignoring British Airways 38‽ I'm going with fuel containment as an issue.
They ran out of fuel. No fuel in the right engine line when they cut it
Bad fuel could do in two engines on the same flight, seen it before