DC Sonic Boom/Citation Down in VA

[tubby linton]

A Cessna C560 that has been unresponsive to ATC has crashed in Staunton Virginia. A number of air-defence assets were launched to intercept it.The aircraft was heading from Elizabethton, TN to Ronkonkoma, NY (Suffolk County) and was approaching DC and was unresponsive to Air Traffic Control, causing fighter jets from Andrews AFB to approach the Cessna.

[JanetFlight]

https://www.thedrive.com/the-war-zone/sonic-boom-spooks-washington-d-c-area?fbclid=IwAR2SYbQa5pN0uYl5T_qsHoit8jMiDxT4aE1i2dzum0swcK Nle6kFTdRxkLc

[silkox]

Sonic boom heard across D.C. region caused by military flight, Md. officials sayThat's the headline. In the article (link below) it is said a Cessna Citation was reported down after having flown over DC.

https://www.washingtonpost.com/dc-md-va/2023/06/04/sonic-boom-washington-virginia-maryland

[BFSGrad]

Boom shook the house around 3:11 p.m. local.

[TRW Plus]

I saw elsewhere that the plane had made it to near its planned destination and circled round, flying back towards the southwest and MD-DC, was unresponsive, and was in restricted air space near the White house. Fighter jets were scrambled to intercept a potential threat. Some speculation the jet was shot down, unconfirmed. The other obvious theory is pilot incapacitation due to medical emergency such as heart attack or hypoxia.

Numerous region-wide reports of a sonic boom (from the fighter jets, presumably).

[BFSGrad]

Flightaware shows aircraft (N611VG) never initiated a decent approaching ISP destination, maintaining cruise altitude of FL340 through course reversal to SW. Track continued to the SW at FL340 across DC, passing to the N of P-56 areas, but those prohibited areas extend up to only 18,000 ft.

[JohnnyRocket]

Interesting to view the flight path - but what would cause it to loop back around like that?
I presume the flight plan would have taken it as far as Suffolk County airport... but why a U-turn?

https://twitter.com/PenguinSix/status/1665451958570737665?ref_src=twsrc%5Etfw%7Ctwcamp%5Etweetembe d%7Ctwterm%5E1665451958570737665%7Ctwgr%5Ed545bcd1ecbef11a36 f2f5d1e669ed9661bc70a4%7Ctwcon%5Es1_&ref_url=https%3A%2F%2Fwww.dailymail.co.uk%2Fnews%2Farticle-12158901%2FNRA-director-pays-heartbreaking-tribute-daughter-granddaughter-killed-Cessna-crash.html

[Feathered]

Interesting to view the flight path - but what would cause it to loop back around like that?
I presume the flight plan would have taken it as far as Suffolk County airport... but why a U-turn?

Would be interesting to see what the default behavior of the C560 FMS is after completing its route without landing and remaining on autopilot. Perhaps it was simply heading to the departure waypoint. Or perhaps there was some fragment of a flight plan beyond KISP that included the departure aircraft (or something else along that line). Or perhaps it wasn't heading to any particular waypoint at all, just a heading direction that pointed back to the origin direction. Very puzzling behavior for an FMS. At any rate, it flew inbound to but above the SFRA/FRZ near Washington DC and caused quite a stir.

Despite the tragedy for those aboard, it is fortunate that the plane crashed in the national forest in a very remote area. With additional fuel, it may easily have crashed closer to whatever waypoint/direction it was heading to and in a populated area, causing something even worse, unless the fighter jets decided to shoot it down first.

This was a 1990 model, so the original Citation V before the later upgrades (Ultra than Excel).

More details to come....

[procede]

Sounds a lot like the one that ended in the Baltic sea last year.
https://en.wikipedia.org/wiki/2022_Baltic_Sea_Cessna_Citation_crash

[Fonsini]

More information about the owners and occupants, the political “twist” will no doubt result in a few conspiracy theories. May they rest in peace.

N611VG Owners (https://www.thedailybeast.com/crashed-plane-behind-dc-chaos-owned-by-maga-donor-couple)

[Liffy 1M]

Aviation Safety Network's succinct summary: https://aviation-safety.net/database/record.php?id=20230604-0

[MechEngr]

On more modern aircraft are there design/regulatory mandates to override the throttles when the cabin pressure goes over 10,000 feet? It seems obvious enough. How many crashes would have been avoided by such a mechanism?

[AmarokGTI]

On more modern aircraft are there design/regulatory mandates to override the throttles when the cabin pressure goes over 10,000 feet? It seems obvious enough. How many crashes would have been avoided by such a mechanism?

Please can you elaborate on what you mean/are suggesting?

[MechEngr]

If the cabin pressure gets above 10,000 feet (or some other agreed upon value) that the engines throttle back to a setting appropriate for cruise at that altitude.

I think it would have saved at least 3 aircraft that I know of - all turned into long-range cruise missiles waiting to drop on unsuspecting landscape. Lucked out so far they have missed cities.

There is likely some pressurization warning but it seems not to be reliable or sufficient.

[Luc Lion]

Isn't it premature to conclude that the pilot passed out due to an absence of pressurisation ?

[MechEngr]

Sure. And no other occupants were seen waving. Just like every other pressurization failure. But maybe they all had the fish,

[what next]

If the cabin pressure gets above 10,000 feet (or some other agreed upon value) that the engines throttle back to a setting appropriate for cruise at that altitude.

There are later Citation 560 models (the 560XLS and XLS+) whose autopilot has an automatic emergency descent mode. One prerequisite for that are electronically controllable engines (FADEC) which this 1990 model did not have, unless retrofitted at some later stage.
But there is a much easier and non-technical way by which some of these accidents, including the one over the Baltic Sea referenced above, can be prevented: Employ a second pilot. Money seems to have been no issue here, the aircraft owners could even afford to donate hundreds of thousands of Dollars to politicians. What are a few hunderd Dollars per flight in comparison to that?

[MechEngr]

I was remarking on it being required, not if it was available. Typical hypoxia causes** lead to the victims having no idea of the seriousness of the problem, so they would never start an emergency response. They should already have oxygen available - they just don't choose to use it.

**In the non-aviation cases it occurs when some volume is filled with atmosphere displacing gases. One horror story was a rail road tank car that a guy was sent to clean out. His buddy noticed he had taken too long and went to the car, climbed up and, looking down the hatch, saw the guy motionless at the bottom. So his buddy climbed in to help, and also died. They get confused, often giddy, and then die. A second pilot might not help.

[Luc Lion]

There are some very few cases where an external help saved the day.
I would hope (or recommend) that all controllers here have listened to the audio recording underneath and be able to recognise hypoxic incapacitation.

<iframe width="969" height="646" src="https://www.youtube.com/embed/XGdYb2J6Wbk" title="What a Pilot Sounds Like With Extreme Hypoxia" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture; web-share" allowfullscreen></iframe>

https://www.youtube.com/watch?v=XGdYb2J6Wbk (https://www.youtube.com/watch?v=XGdYb2J6Wbk)

[Jonty]

If the cabin pressure gets above 10,000 feet (or some other agreed upon value) that the engines throttle back to a setting appropriate for cruise at that altitude.

I think it would have saved at least 3 aircraft that I know of - all turned into long-range cruise missiles waiting to drop on unsuspecting landscape. Lucked out so far they have missed cities.

There is likely some pressurization warning but it seems not to be reliable or sufficient.


There are areas of the Earth where that would put you into the side of a mountain.

What I do think would help is if all pilots of pressurised aircraft were subjected to a hyperbaric chamber. They would then know the warning signs of a slow depressurisation, and be able to act accordingly.

[Feathered]

There are later Citation 560 models (the 560XLS and XLS+) whose autopilot has an automatic emergency descent mode. One prerequisite for that are electronically controllable engines (FADEC) which this 1990 model did not have, unless retrofitted at some later stage.
But there is a much easier and non-technical way by which some of these accidents, including the one over the Baltic Sea referenced above, can be prevented: Employ a second pilot. Money seems to have been no issue here, the aircraft owners could even afford to donate hundreds of thousands of Dollars to politicians. What are a few hunderd Dollars per flight in comparison to that?
I have no clue what caused this accident at this time, but perhaps it was low cabin pressure / hypoxia. A second pilot may help in some situations or cross checks, but if there is not enough oxygen to keep one pilot conscious, how would a second pilot remain conscious unless there is a mandate that they are more physically fit / able to stay conscious with lower oxygen levels?
Are there any deficiencies in cabin low pressure warnings that could be addressed to provide better alerting BEFORE the O2 levels fall too low to keep the pilot(s) conscious enough to hear them?

[MechEngr]

Those same mountains will kill a pilot that has passed out. But maybe if the plane refuses to climb then a pilot with his wits about him will either put on oxygen and push the override or will avoid hitting the mountains, possibly after turning up the pressurization.

[Feathered]

On more modern aircraft are there design/regulatory mandates to override the throttles when the cabin pressure goes over 10,000 feet? It seems obvious enough. How many crashes would have been avoided by such a mechanism?

Don't try that method in places like Colorado, Utah, California, Alaska, Hawaii, portions of: China, Tibet, India, Pakistan, Chile, Peru, Chile, western Canada, Kyrgyzstan, France, Georgia, Switzerland, Italy, Indonesia, Japan, Greenland, Guatemala, etc.

Especially if there is a static sensor problem inhibiting throttles and the pilots are wide awake to see the cumulogranite approaching at 12 o'clock.

[what next]

I have no clue what caused this accident at this time, but perhaps it was low cabin pressure / hypoxia. A second pilot may help in some situations or cross checks, but if there is not enough oxygen to keep one pilot conscious, how would a second pilot remain conscious unless there is a mandate that they are more physically fit / able to stay conscious with lower oxygen levels?

People react differenty to oxygen starvation. Whilst some become unsconscious very quickly others stay awake a few seconds longer, maybe just sufficiently long to get one's oxygen mask on or not. And we do not even know if this accident was caused by a pressurisation problem. It can have been any kind of medical incapacitation in which case a second pilot would certainly have saved the flight.

[Magplug]

For whatever reason this Zombie aircraft continued to fly the pre-programmed route without communication from Tennessee until reaching it's destination on Long Island where it ran out of FMC waypoints to follow. The autopilot likely dropped into Hdg/HdgHold at that point. The aircraft overflew it's destination (ISP) down runway 24 maintaining FL340 and continued with that heading and level until the final spiral descent in mid-Virginia. My guess is that was at the point it ran out of gas. On passing Washington, had that a/c started a descent towards the Capitol Area it would have been shot down immediately. Instead it maintained FL340 and was allowed to carry on.

It seems very likely the pilot had become incapacitated. Had that incapacitation been confined to the pilot and evident to the passengers either visually or after the expected flight time expired then likely one of them would have attempted to communicate on a radio in some manner. There is no report of any such communication which points to an incapacitation affecting all on board. LIkely a depressurisation. We understand all on board perished and our thoughts are with the family. It may be small relief to the family but it is likely that all on board were peacefully unconscious for some time before the crash took place.

As an ex-military pilot I was obliged to carry out depressurisation training at two-yearly intervals throughout my service. After I moved to the airlines I never understood why that was not mandated for professionally licenced airline pilots.

[island_airphoto]

Is a loud buzzer that goes off at say 12,000 feet cabin pressure a thing? I don't fly pressurized aircraft myself.

[what next]

Is a loud buzzer that goes off at say 12,000 feet cabin pressure a thing?

The various Citation 550 and 560 models that I flew and fly have no audible warning for low cabin pressure. You get a flashing red warning light in the annunciator panel and a flashing red master warning light. Above 14.000 ft (plus minus a few) the passenger oxygen masks will drop automatically which may or may not be seen from the cockpit. There is no door, but some sort of divider and an optional curtain.

[BFSGrad]

But there is a much easier and non-technical way by which some of these accidents, including the one over the Baltic Sea referenced above, can be prevented: Employ a second pilot. Money seems to have been no issue here, the aircraft owners could even afford to donate hundreds of thousands of Dollars to politicians. What are a few hunderd Dollars per flight in comparison to that?Are there any examples of a loss of cabin pressure event incapacitating one pilot while the other pilot maintained consciousness allowing for a successful emergency descent? I can think of at least two accidents (N47BA, Helios 522) where the 2nd pilot made no difference.

If this was a pilot incapacitation event unrelated to cabin pressure, a 2nd pilot likely would have safely landed the aircraft. However, initial reports seem to support the loss of cabin pressure. ABC News reported a “U.S. official” stated that the pilot was observed passed out. Had the other two adult passengers been conscious (i.e., not a loss of cabin pressure), I would expect the F-16s to have observed some activity onboard the aircraft, especially in the cockpit.

Regarding the comment that the owner could have spent more money on a 2nd pilot, wealthy folks tend to be risk takers. That’s usually how they became wealthy.

Some news reports are stating that the Citation violated or entered DC restricted airspace, triggering the NORAD response. The DC FRZ and SFRA extend upward to but not into Class A airspace. The Citation was in Class A at FL340 during the entire transit of the DC area. Seems likely the NORAD response was triggered as soon as ATC lost radio contact with the Citation, which would have been on the leg to ISP, which tracked well south of DC airspace.

[what next]

Are there any examples of a loss of cabin pressure event incapacitating one pilot while the other pilot maintained consciousness allowing for a successful emergency descent?

I did a very superficial google search and only quote 3 incidents from the first page of results: 1994 - Kalitta Flight 861 (http://www.fss.aero/accident-reports/dvdfiles/US/1994-03-15-US.pdf), 2012 - Metroliner from Narrabri to Sydney (page 19 in this report: https://www.laserpointersafety.com/resources/Studies/Australia-study-of-pilot-incapacitation-events-and-outcomes-ar-2015-096-final.pdf), 2018 - Qantas (https://www.heraldsun.com.au/news/victoria/qantas-cargo-plane-loses-cabin-pressure-leaving-pilot-incapacitated/news-story/201f2c1bc3f30b7b348f00fb35c44504).

[Magplug]

Where do you stop with mandating stuff that MIGHT have made a difference?

In a 737-300 I once experienced exactly the same circumstances that led to the Helios crash. My ears told me something was wrong as we passed about 4000'. It was quickly fixed but without depressurisation training the pilot gets zero exposure to this situation.

[BFSGrad]

I did a very superficial google search and only quote 3 incidents from the first page of results: 1994 - Kalitta Flight 861...The Kalitta 861 report should render any reader speechless. Slightly non-responsive as you can’t lose what you never had.

[AmarokGTI]

If the cabin pressure gets above 10,000 feet (or some other agreed upon value) that the engines throttle back to a setting appropriate for cruise at that altitude.

I think it would have saved at least 3 aircraft that I know of - all turned into long-range cruise missiles waiting to drop on unsuspecting landscape. Lucked out so far they have missed cities.

There is likely some pressurization warning but it seems not to be reliable or sufficient.

Ok I understand what you mean now. The trigger in your idea would have to be cabin altitude above 10,000ft (differential pressure would be zero if completely de pressurised, or reducing towards zero if gradually happening).

I see others have responded quicker than me about flaws in this idea, however (terrain).

[Lake1952]

FL340 the whole flight... track log stops abruptly without any evidence of descent.

Reportedly, the flight stopped communicating approximately 14 minutes after departure. The flight log shows that at that point in the flight, it was passing through FL300. So it Is entirely possible that the plane never pressurized and this was not detected by the pilot.. There was a single pilot and three passengers, including a 2 year old child.

https://flightaware.com/live/flight/N611VG/history/20230604/1700ZZ/0A9/KISP

[EXDAC]

It was quickly fixed but without depressurisation training the pilot gets zero exposure to this situation.

I have been on two "chamber rides". The USA civilian profile is (or was) a gradual decompression that stops at 25,000 feet with all test subjects wearing masks. Each subject in turn removes his/her mask and has time to experience his/her own syptoms and reduction in cognition. No one is allowed to experience loss of consciousness but sometimes a subject is very reluctant to put the mask back on.

I suspect this 25,000 ft exposure would be very different from slow or rapid depressurization at FL340. (My chamber rides were for high altitude glider flying and I have no experience as PIC of pressurized aircraft.)

[MechEngr]

That would be an interesting option - build a full motion platform hypobaric chamber for check flights with 20 - 30 minute bleed-down from the correct pressure. See how many crews notice. Make sure they are kept busy with a bunch of ATC requests and simulated chatter with the company about a late departure and maybe a re-route for weather.

[whitav8r]

Aircraft should come equipped with Garmin emergency Autoland that could safely do an emergency descent while knowing the height of terrain below as well as nearest airport location for the landing. Safest thing especially for single pilot.

[B2N2]

Aircraft should come equipped with Garmin emergency Autoland that could safely do an emergency descent while knowing the height of terrain below as well as nearest airport location for the landing. Safest thing especially for single pilot.

Apparently you don’t understand that requires an entirely different set of avionics and certification?
A Citation of this vintage does not have quick donning oxygen masks unless retrofitted.
The listed owners have two aircraft, a twin turboprop and the C560.
I’m guessing they had a single pilot flying both aircraft for this family under the less stringent regulations of 14 CFR Part 91.
This was either a medical event or a (de)pressurization issue.
Autopilot went into HDG hold after overflying the last fix in the flightplan followed by the destination.

[421dog]

That would be an interesting option - build a full motion platform hypobaric chamber for check flights with 20 - 30 minute bleed-down from the correct pressure. See how many crews notice. Make sure they are kept busy with a bunch of ATC requests and simulated chatter with the company about a late departure and maybe a re-route for weather.

One doesn’t need a hypobaric chamber to do this. FAA CAMI has a plastic tent that they fill with a hypoxic air/nitrogen mixture to the O2 concentration at 25000 ft. They do it without masks on, and there are a couple of attendants keeping tabs on the airmen in the tent, and putting masks on them if they get too out of it. It would be a simple thing to put a pressure mask on a pilot in a sim and do the same thing to him.
Of course, none of it is as impressive as an actual chamber with a vacuum accumulator set up for explosive decompression to 35k.
(But there’s not too much that’s insidious about that, especially when it starts snowing in the tank)
Civil airmen can go to CAMI and do not only hypoxic training, but a bunch of other useful things, and it’s all free.

[Mk 1]

As an ex-military pilot I was obliged to carry out depressurisation training at two-yearly intervals throughout my service. After I moved to the airlines I never understood why that was not mandated for professionally licenced airline pilots.

Even trained military aviators sometimes don't recognise the symptoms. An F/A-18 pilot I know in the RAAF was last seen by his wingman in a gentle climb through 51,000 ft over the Gulf of Carpentaria with his oxygen mask dangling, the wingmen hit bingo fuel and had to RTB.

[whitav8r]

What I meant to say about the Garmin Autoland capability is obviously not for this Citation, but was aimed at a possible solution for all new single ( or even dual ) pilot jet aircraft. It might need some new programming to support early detection of improper cabin pressure. The goal would obviously be to get the vehicle down to safe altitude ( it has a worldwide terrain database) as soon as possible after detection. then, even if the pilots were temporarily incapacitated, Hopefully all would recover, and if not, the aircraft wouldn’t become an unguided missile

[MechEngr]

Before advanced autoland, perhaps FDRs and CVRs. could be added to decrease the mystery and investigation costs? If a traditional FDR isn't easily retrofitted, then a system that captures video of the majority of the controls and the entirety of the control panel would be enough? A high-def web cam and a single board computer in a tough box would likely suffice. Apparently all the NTSB has found so far is aluminum confetti.

[alf5071h]

Before considering extreme technical fixes for a particular accident, and without knowledge of the cause; question if FAR 23 GA aircraft have warning systems - visual and audio, as required by FAR 25 for commercial aircraft - high cabin alt.

[what next]

Before considering extreme technical fixes for a particular accident, and without knowledge of the cause; question if FAR 23 GA aircraft have warning systems - visual and audio, as required by FAR 25 for commercial aircraft - high cabin alt.

The Cessna C560 is an FAR 25 aircraft. Single pilot operation like in this case requires special FAA certification.

[keri]

For whatever reason this Zombie aircraft continued to fly the pre-programmed route without communication from Tennessee until reaching it's destination on Long Island where it ran out of FMC waypoints to follow. The autopilot likely dropped into Hdg/HdgHold at that point. The aircraft overflew it's destination (ISP) down runway 24 maintaining FL340 and continued with that heading and level until the final spiral descent in mid-Virginia. My guess is that was at the point it ran out of gas. On passing Washington, had that a/c started a descent towards the Capitol Area it would have been shot down immediately. Instead it maintained FL340 and was allowed to carry on.

It seems very likely the pilot had become incapacitated. Had that incapacitation been confined to the pilot and evident to the passengers either visually or after the expected flight time expired then likely one of them would have attempted to communicate on a radio in some manner. There is no report of any such communication which points to an incapacitation affecting all on board. LIkely a depressurisation. We understand all on board perished and our thoughts are with the family. It may be small relief to the family but it is likely that all on board were peacefully unconscious for some time before the crash took place.

As an ex-military pilot I was obliged to carry out depressurisation training at two-yearly intervals throughout my service. After I moved to the airlines I never understood why that was not mandated for professionally licenced airline pilots.

Back in my RAF days and even as an engineer who flew in fast jet back seats (air tests, trips to assess/repair landaways) I was required to regularly attend North Luffenham for hypobaric chamber hypoxia training etc. I was surprised to discover that civvy airline pilots (and cabin crew) do not do likewise.

[BFSGrad]

Before advanced autoland, perhaps FDRs and CVRs. could be added to decrease the mystery and investigation costs? If a traditional FDR isn't easily retrofitted, then a system that captures video of the majority of the controls and the entirety of the control panel would be enough? A high-def web cam and a single board computer in a tough box would likely suffice. Apparently all the NTSB has found so far is aluminum confetti.In this specific accident scenario, what useful information would you expect from a CVR and FDR?

With the increased use of digital electronic devices (e.g., mobile phones, tablets/EFB, engine instrument monitors), accident investigators are finding useable data for accident investigation even though these devices are not designed for crash resistance. There’s also increased use of FDM/FOQA devices, some of which provide video (e.g., N13GZ, Appareo 1000).

[RatherBeFlying]

If the cabin altitude is left to climb, you are steadily losing IQ points. I don't know what warnings the 560 shows, but there's a possibility that by the time the warnings come on, the crew may not have sufficient cognition to react properly.

I remember one flight in my glider before I installed oxygen and being perplexed about which hand of the altimeter was what at 12,500.

[alf5071h]

what next - FAR 25, thank-you.

Thence if an alerting system was fitted, was it functional, was it adhered to ?

I recall that it was suspected that the Helios 737 audio alert was mistaken for overspeed - warning horn.

[what next]

Thence if an alerting system was fitted, was it functional, was it adhered to ?

I recall that it was suspected that the Helios 737 audio alert was mistaken for overspeed - warning horn.

I am pretty sure that the investigation will thoroughly look into these items. According to internet wisdom, the aircraft was only recently imported from Venezuela in January this year. What equipment was installed and functional should be listed in the maintenance records. The little information that has been disclosed about the pilot is that he was a retired airline captain with over 25.000 flying hours.

As written above, the C560 has no aural cabin pressure warning. Only annunciator lights. When then sun shines directly onto the annunciator panel, a warning light coming on can easily be missed. As a backup warning, the passenger oxygen masks drop automatically when passing 14.000ft, startling the passengers, who will certainly ask the pilot what's going on. But this only works if the relevant switch is in the correct position and the oxygen bottle has enough pressure and the bottle valve is open.

[Speed_Trim_Fail]

what next - FAR 25, thank-you.

Thence if an alerting system was fitted, was it functional, was it adhered to ?

I recall that it was suspected that the Helios 737 audio alert was mistaken for overspeed - warning horn.

On the Helios flight it was confusion between the takeoff config horn and the cabin alt warning horn (which were identical as they used the same horn), coupled with the fact that in the 737 Classic a secondary symptom of excessive cabin altitude was the EFIS instruments (EADI and EHSI) going monochrome as the thinner air failed to cool the avionics effectively.

The already hypoxic crew were trouble shooting entirely irrelevant problems; hence why afterwards Boeing installed lights to indicate which warning was going off.

I have not flown the Classic for a long time, it was an absolutely marvellous machine, but it could be very very unforgiving compared to more modern aircraft. That said, hypoxia is one of the biggest threats we face, not least as the condition itself can interfere with your ability to realise you are in difficulty.

[GBO]

There have been a few hypoxia related accidents which could explain this flight
eg Helios 522, Malaysia MH370, Payne Stewart’s Lear Jet, VH-SKC.

However, there are other pilot incapacitation scenarios
eg pilot suffering from a medical condition

[TWT]

MH370 was a hypoxia related incident ?

No-one knows what happened to MH370 with any certainty.

[tarkay01]

N611VG Was NOT a loss of pressurization By Dan Grader On YouTube

https://youtu.be/s0G9sthn8bU

This analysis by Don Gryder seems to make a lot of sense. Basically the pilot had a medical incapacitation ( heart attack, stroke, etc) early in the flight which none of the passengers noticed. On a loss of pressurization incident, the windows will fog over. This plane had clear windows. Basically, there was no copilot to take over when the pilot became incapacitated.

Dan covers all the salient points.

[GlobalNav]

N611VG Was NOT a loss of pressurization By Dan Grader On YouTube

https://youtu.be/s0G9sthn8bU

This analysis by Don Gryder seems to make a lot of sense. Basically the pilot had a medical incapacitation ( heart attack, stroke, etc) early in the flight which none of the passengers noticed. On a loss of pressurization incident, the windows will fog over. This plane had clear windows. Basically, there was no copilot to take over when the pilot became incapacitated.

Dan covers all the salient points.

Perhaps, but I wouldn’t be so hasty. Yes, rapid depressurization will lower the temperature and may fog the windows. But the slower, insidious depressurization would not. Was the 14,000 foot cabin alert working? Or noticed? Was the single pilot already physically compromised when the alert appeared? Too early for rash conclusions.

[jolihokistix]

Did we know if the Andrews F-16 pilot(s) saw the passengers?

[MechEngr]

Gryder mentions the Payne Stewart plane was reported to have frosted windows - covered here: https://en.wikipedia.org/wiki/1999_South_Dakota_Learjet_crash#First_interception

On the other hand, the windows on the Helios flight were all clear enough to see the cockpit with slumped pilot and then the entry by the flight attendant on oxygen bottle and the dangling oxygen masks in the passenger area.

Both aircraft had previously reported for problems with pressurization.

I'm not sure the passengers in the instance of a medical problem would fail to notice the additional time, nearly an hour, in the air no matter how distracted. All falling asleep is possible, but it's not that long a flight.

The current report is that ATC failed to establish contact about 15 minutes after takeoff, about the time for hypoxia to set in but, sure, stroke or heart attack could happen any time.

[aeromech3]

I recall that it was suspected that the Helios 737 audio alert was mistaken for overspeed - warning horn.
I think most Mach over-speed warnings are a clacker sound (similar to a football supporters rattle clacker) not a horn.
Remembering the BAC1-11 400 very easily flew on the clacker.

[BraceBrace]

On more modern aircraft are there design/regulatory mandates to override the throttles when the cabin pressure goes over 10,000 feet? It seems obvious enough. How many crashes would have been avoided by such a mechanism?

I would think you would create many extra hazards as well? Linking a throttle override to cabin pressure seems a very dangerous/confusing thing to do. Think about other traffic, terrain clearance,... It might also creates other problems in regard to scheduled unpressurized flights due to (ie) technical problems known in advance with the pressurization system. There are more simple solutions.

TUC at 10000ft is not the same as a depressurization at +30000ft. There is plenty of time to react, so as long as you have a good system informing the pilots correctly, there should be no issue.

[EDLB]

I would not rule out a pressurization problem that quick.Even so the passengers have no formal training, you would expect that on a GA single pilot operation they will get an idea if the sole pilot is incapacitated and some flares are shot by an F16 while they gaze into your windows.
There is no door between row 0 and the passenger area.

[Lake1952]

Question I do not know the answer to...is the the "frosted windows" effect more likely to happen when a decompression occurs at altitude vs. a situation where the plane essentially never pressurizes as it climbs to altitude?

[BFSGrad]

DG’s thesis rests on two key points: (1) the momentary pause at FL230 (about 9 min into the flight) shows that the pilot was alive and well at that point with a properly functioning pressurization system, and (2) the passengers in the back were oblivious to the pilot status for the entire duration of the longer-than-planned flight.

Unfortunately (but typically) he combines a plausible analysis with clumsy drama at 4:08, unnecessarily emphasizing with great certainty that the passengers were conscious and died a horrible death. There was a statement attributed to Churchill where he described John Foster Dulles when U.S. Secretary of State as a bull that brings along his own china shop. An apt description for DG.

Regarding the first point it also seems possible that, given the rapid rate of climb along with the TUC at that altitude, that the pilot would still able to operate aircraft controls and respond to ATC while experiencing the onset of hypoxia. Curious to know if the pause at FL230 was ATC directed.

As to the second point, I find it unlikely that both mother and nanny would sleep, leaving a 2-year-old unsupervised. As to the 2-year-old sleeping, my experience is that, when cooped up in an airplane cabin, sleeping is not among the top 3 potential activities for a 2-year-old. I also find it unlikely that, if awake, the passengers were so engrossed in some unspecified activity, that a slumped-over pilot or extended flight time would go unnoticed until the final spiral to the ground.

[visibility3miles]

https://www.washingtonpost.com/transportation/2023/06/06/virginia-plane-crash-wreckage-ntsb-investigation/

[the pilot] was a retired Southwest Airlines captain and former member of its pilots union’s board of directors, the group confirmed. He had recently obtained the highest-level Federal Aviation Administration medical certificate and was rated to fly Boeing 737s, among other planes.

…[his] flight history… included 25 years and more than 25,000 flight-hours with Southwest. He also was certified as an aircraft mechanic

[DaveReidUK]

N611VG Was NOT a loss of pressurization By Dan Grader On YouTube

https://youtu.be/s0G9sthn8bU

This analysis by Don Gryder seems to make a lot of sense. Basically the pilot had a medical incapacitation ( heart attack, stroke, etc) early in the flight which none of the passengers noticed. On a loss of pressurization incident, the windows will fog over. This plane had clear windows. Basically, there was no copilot to take over when the pilot became incapacitated.

Dan covers all the salient points.

Or, for an alternative perspective:

vY15feS9Va4

[albatross]

If it was not a cabin pressurization problem I would expect there would have been some very concerned people looking out the windows at the F-16s. Not to mention some cell phone activity and perhaps a pax in the cockpit trying to figure out how the radio PTT switch works.

[visibility3miles]

BFSGrad. I find it highly likely that a two-year-old would fall soundly asleep amidst the gentle hum and vibration of a relatively short airplane trip.

However, I’ve joked with others about the “baby barometer,” perhaps more applicable to infants, who have trouble clearing their ears and start wailing when the plane begins to descend.

I assume that one or both of the adults in the passenger cabin might have been checking their watches and the ETA as they were trying to go elsewhere upon arrival.

The lack of ATC communication happened extremely early into this trip, and we don’t know why, but hypoxia would go a long way to explain it. As to the passengers, per the Washington Post article I cited earlier, they’d known this particular pilot a long time and presumably weren’t strangers to the cockpit.

And yes, frost on the windows does reflect an abrupt loss of pressure at high altitude, not a slow leak. After all, when you hike up a mountain, the air gets thinner, but you don’t see your breath crystallize until it is really, really cold.

With a slow pressure leak, I assume the humidity from your breath in the cabin would leak away too, hence less to cause the windows to ice up.

PV = nRT. Pressure drop = temperature drop. Avogadro’s law. Ideal pressure law.

Pure speculation on my part.

[BFSGrad]

Useful update in the comments section of the video linked in post #62.

UPDATE: 6/6/23 ATC Audio Timeline:

1722:22Z N611VG checks in with Atlanta Center (ZTL) at FL230 and issued a climb to FL290 which was read back correctly.

1725:50Z ZTL issues N611VG a climb to FL340 as the aircraft was passing through FL277. This clearance was acknowledged and read back correctly.

1728:33Z ZTL amends the altitude to FL330 because of traffic in the next sector in Washington Center’s (ZDC) airspace. N611VG was passing through FL320. This transmission was never acknowledged and ATC was unable to contact N611VG again.

So somewhere between 1725Z and 1728Z (Shortly after takeoff, while climbing out) the event occurred that caused the remainder of the flight to out of contact with ATC. Jb.

[Magplug]

The guy in the video appears to have made up his mind already. They should have had a co-pilot is his unwavering view. To suggest the F16 action in intercepting a Zombie headed for DC was something to do with whose campaign he donated to tells you all you need to know about the commentator (and the US mindset).

An insidious depressurisation above FL300 will not fog out the cabin or freeze out the windows. An explosive decompression might.... But it will also have you going straight for your oxygen mask! I have done a few decompression test flights at altitude so I speak from experience. The passengers asked no questions of the pilot after the expected flight time had been and gone? Why not?

[Loose rivets]

Descriptions of the Comet depressurisations have the passengers suffer catastrophic physiological failure in next to no seconds. Wiki tells a distressing tale, deaths caused by ruptured lungs.

[MerrillParker]

Magplug:

Gryder specifically stated his opinion was the F16 action in intercepting the aircraft had nothing to do with politics or who the owner did or did not donate money to. He said the conspiracy theories had nothing to do with the accident.

Dan Gryder is definitely opinionated. We will find out in the future if he was correct in whole or in part.

[DaveReidUK]

Descriptions of the Comet depressurisations have the passengers suffer catastrophic physiological failure in next to no seconds. Wiki tells a distressing tale, deaths caused by ruptured lungs.

Indeed so.

Though of course there is no suggestion that the Citation was subject to an instantaneous decompression.

[hoistop]

There are later Citation 560 models (the 560XLS and XLS+) whose autopilot has an automatic emergency descent mode. One prerequisite for that are electronically controllable engines (FADEC) which this 1990 model did not have, unless retrofitted at some later stage.
But there is a much easier and non-technical way by which some of these accidents, including the one over the Baltic Sea referenced above, can be prevented: Employ a second pilot. Money seems to have been no issue here, the aircraft owners could even afford to donate hundreds of thousands of Dollars to politicians. What are a few hunderd Dollars per flight in comparison to that?

Helios Airways Flight 522 had two proffesional, experienced pilots in the cockpit. That did not prevent death of everyone aboard.
I think that some automation might help - as already sugggested it is available on some more modern airplanes. And there is even emergency panic button for passengers available, that sends certain types of GA airplanes to automatic landing. (in case of pilot incapacitation, but passengers staying alert)
It seems there will be more single pilot incapacitation incidents in the future, as average age of pilots in those small jets goes up, methinks.

[what next]

Helios Airways Flight 522 had two proffesional, experienced pilots in the cockpit. That did not prevent death of everyone aboard.

We have had this discussion two pages up already. Of course there are plenty of examples of pressurisation related accidents that were not or could not be prevented by a second pilot on board. But there are many more happy outcomes due to an additional crewmenber. Not to talk about non-pressurisation related incidents that can only be recovered by a second pilot. Or, as you write, some kind of technical solution. There are some newer planes which can have this feature installed (e.g. Beechcraft Denali, Piper M600, Cirrus Vision Jet) but retrofitting an older aicraft like this C560 here is going to be a lot more expensive - if possible at all - than to pay for a second pilot for the next 20 years.

[BFSGrad]

The guy in the video appears to have made up his mind already. They should have had a co-pilot is his unwavering view. To suggest the F16 action in intercepting a Zombie headed for DC was something to do with whose campaign he donated to tells you all you need to know about the commentator (and the US mindset).

An insidious depressurisation above FL300 will not fog out the cabin or freeze out the windows. An explosive decompression might.... But it will also have you going straight for your oxygen mask! I have done a few decompression test flights at altitude so I speak from experience. The passengers asked no questions of the pilot after the expected flight time had been and gone? Why not?DG is out with a second video that I find even less compelling. When he gets into his medical analysis, he wanders completely off the reservation.

There is a mindset that any decompression—fast, slow, explosive—will frost the windows. I agree that there is evidence that is not always the case; e.g., 2022 OE-FGR.

His medical (non-hypoxia) incapacitation theory hinges on the assumption that the two adult passengers would not have noticed the slumped-over pilot. While I’ve never flown in an older Citation, the few online videos from a cabin perspective show that the flight crew is clearly visible from the cabin. Seems unlikely that two conscious adults would not have attempted to render aid to the pilot and take action to address their urgent situation; i.e.. raise the cabin window shades, move to cockpit and start pushing buttons and twisting knobs. Then there’s the discussion of whether it’s technically feasible for a cell phone to make a connection from FL340.

[Magplug]

Dan Gryder is definitely opinionated. We will find out in the future if he was correct in whole or in part.

Sadly I don't think we ever will:

Gryder's assertion that the pilot was a fine upstanding union man with a spotless record has absolutely no bearing on his useful time of consciousness when experiencing a subtle decompression.

Captain Heffner may well have passed a class one medical yesterday but that does not reduce his chances of suffering a massive heart attack today. When I reached the age of forty it was mandatory to switch to a 6 monthly periodicity for UK class one medicals. I must have done two or three medicals like that. One day an RAF loadmaster aged in his late forties walked out of his medical and straight into a brief for a sortie. As he walked out to the aircraft 30 minutes later he dropped dead from a massive heart attack. It was at this point that the medical establishment reconsidered the validity of giving 6 monthly ECGs and the practice ceased. Now it is only mandatory for the over 60s.

We understand that there was no flight recorder on this aircraft and the dynamics of the crash simply left aluminium confetti. In the circumstances it seems very unlikely that any post-mortem evidence will be available to witness an explosive decompression. The Comet incidents mentioned above involved massive failure of the rear pressure bulkhead resulting in high speed loss of the empennage. That alone would have resulted in bodies being sucked clear of the aircraft and free-falling to earth around 120mph. Post mortem examination might have revealed at least some of what led to the death of the victims. A bizjet impacting at 29,500 fpm is quite another proposition. Therefore it seems unlikely that any evidence remains in this case that might witness the true cause of the crash.

There is a good reason that ATP pilots stop flying at the age of 65. It's nothing to do with the individual and all to do with balance of risk that comes with age.

[DaveReidUK]

DG is out with a second video that I find even less compelling. When he gets into his medical analysis, he wanders completely off the reservation.

To be fair, Dan does give a pointer right at the start of the video - as he sits there with his "DTSB [geddit?] - Probable Cause" hat on - as to the likely value of what follows.

[JRBarrett]

There is a mindset that any decompression—fast, slow, explosive—will frost the windows. I agree that there is evidence that is not always the case; e.g., 2022 OE-FGR.

I think Dan Gryder is off the mark on this. “He doesn’t know what he doesn’t know.”

I’m not a pilot, but am a mechanic, with many year’s experience working on air conditioning and pressurization systems on small, medium and large jet aircraft.

A loss of pressurization at altitude will not (necessarily) inevitably lead to the windows frosting. It depends on what caused the loss of pressurization.

All jet aircraft use heated engine bleed air to condition the cabin air. In larger aircraft, that have a full ACM (Air Cycle Machine) the bleed air temperature can be modified to as low as 32 degrees F by using an expansion turbine combined with heat exchangers. (The bleed air cannot be pumped directly into the cabin from the engines as it is far too hot.)

The Citation 560 does not have a full ACM. Like many smaller GA jet aircraft, it uses bleed air and heat exchangers to set the incoming air temperature for heating. For cooling, (typically only needed on the ground on hot days, or at lower altitudes), it has a standard freon vapor cycle refrigeration unit, little different from a home or automobile air conditioner.

Larger aircraft, with a full ACM, can provide heated or cooled air (as needed) from a single unit.

Cabin air temperature will usually be automatically controlled by adjusting the mixture of heated bleed air and refrigerated air to keep the temperature at a comfortable level.

The incoming conditioned air is what pressurizes the cabin. The degree of pressurization is controlled by outflow valves, typically located at the rear of the pressure vessel, which permit the cabin air to discharge to the external atmosphere. On the ground, the outflow valves are fully open, and all incoming conditioned air flows right back out again, so the cabin pressure remains the same as external ambient air pressure.

Upon takeoff, the outflow valves begin to close under the control of the pressurization system, which permits the cabin air pressure to increase above ambient external pressure as the aircraft climbs. At high altitude, the outflow valves will be almost completely closed.

If a loss of pressurization is caused by a failure of the outflow valves - either because of a fault in the valves themselves, or the pressurization controller, (or failure by the pilot to enable the pressurization system in the first place), then the cabin pressure will drop to external ambient pressure.

But, in this scenario, the cabin temperature does not automatically drop to ambient temperature. The air conditioning system is still dutifully pumping heated bleed air into the aircraft. If the outflow valves are wide open, all that air is discharged to the external atmosphere so the cabin pressure remains at, or near external atmospheric pressure - but the air temperature inside the aircraft will not necessarily fall to ambient as long as a continuous supply of heated air continues to flow.

A pressurization loss caused by by a failure of the incoming air supply is another matter. In this case, the outflow valves might be working perfectly, and would quickly go fully closed, but with no incoming heated air, cabin altitude will rise to ambient, and the cabin temperature will quickly fall to extremely cold levels. The ambient air temperature at FL 340 is typically between -45 to - 55 Celsius (depending on the season).

In this scenario, the cockpit and cabin windows will likely frost over relatively quickly.If the cockpit windows are electrically heated, they might not frost up completely. If they are heated by the conditioned air supply (like an automobile defroster), they likely will frost up.

A third scenario is explosive decompression, which is anything that results in a major breach of the pressure vessel. That could be caused by a window or door blowing out, or structural failure of the pressure vessel. In this case there will obviously be loss of pressurization, and if the “hole” is large enough, even the best cabin air supply system would not be be able to maintain the temperature.

TL / DR

Pressurization failure caused only by a problem with the outflow valves will not necessarily cause cabin temperature to drop to sub-freezing levels, if the heated cabin air supply is otherwise working.

Pressurization failure caused by a total loss of incoming cabin air supply will cause the cabin temperature to fall to very cold levels quickly, with accompanying frosting of cockpit and cabin windows. Likewise for an explosive decompression event caused by a major breach of the integrity of the pressure vessel.

Jim Barrett

[cavuman1]

An excellent and very informative post, JRBarrett. Many misconceptions are cleared and gaps in knowledge filled. Thank you!

- Ed

[hans brinker]

I think Dan Gryder is off the mark on this. “He doesn’t know what he doesn’t know.”

I’m not a pilot, but am a mechanic, with many year’s experience working on air conditioning and pressurization systems on small, medium and large jet aircraft.

A loss of pressurization at altitude will not (necessarily) inevitably lead to the windows frosting. It depends on what caused the loss of pressurization.

All jet aircraft use heated engine bleed air to condition the cabin air. In larger aircraft, that have a full ACM (Air Cycle Machine) the bleed air temperature can be modified to as low as 32 degrees F by using an expansion turbine combined with heat exchangers. (The bleed air cannot be pumped directly into the cabin from the engines as it is far too hot.)

The Citation 560 does not have a full ACM. Like many smaller GA jet aircraft, it uses bleed air and heat exchangers to set the incoming air temperature for heating. For cooling, (typically only needed on the ground on hot days, or at lower altitudes), it has a standard freon vapor cycle refrigeration unit, little different from a home or automobile air conditioner.

Larger aircraft, with a full ACM, can provide heated or cooled air (as needed) from a single unit.

Cabin air temperature will usually be automatically controlled by adjusting the mixture of heated bleed air and refrigerated air to keep the temperature at a comfortable level.

The incoming conditioned air is what pressurizes the cabin. The degree of pressurization is controlled by outflow valves, typically located at the rear of the pressure vessel, which permit the cabin air to discharge to the external atmosphere. On the ground, the outflow valves are fully open, and all incoming conditioned air flows right back out again, so the cabin pressure remains the same as external ambient air pressure.

Upon takeoff, the outflow valves begin to close under the control of the pressurization system, which permits the cabin air pressure to increase above ambient external pressure as the aircraft climbs. At high altitude, the outflow valves will be almost completely closed.

If a loss of pressurization is caused by a failure of the outflow valves - either because of a fault in the valves themselves, or the pressurization controller, (or failure by the pilot to enable the pressurization system in the first place), then the cabin pressure will drop to external ambient pressure.

But, in this scenario, the cabin temperature does not automatically drop to ambient temperature. The air conditioning system is still dutifully pumping heated bleed air into the aircraft. If the outflow valves are wide open, all that air is discharged to the external atmosphere so the cabin pressure remains at, or near external atmospheric pressure - but the air temperature inside the aircraft will not necessarily fall to ambient as long as a continuous supply of heated air continues to flow.

A pressurization loss caused by by a failure of the incoming air supply is another matter. In this case, the outflow valves might be working perfectly, and would quickly go fully closed, but with no incoming heated air, cabin altitude will rise to ambient, and the cabin temperature will quickly fall to extremely cold levels. The ambient air temperature at FL 340 is typically between -45 to - 55 Celsius (depending on the season).

In this scenario, the cockpit and cabin windows will likely frost over relatively quickly.If the cockpit windows are electrically heated, they might not frost up completely. If they are heated by the conditioned air supply (like an automobile defroster), they likely will frost up.

A third scenario is explosive decompression, which is anything that results in a major breach of the pressure vessel. That could be caused by a window or door blowing out, or structural failure of the pressure vessel. In this case there will obviously be loss of pressurization, and if the “hole” is large enough, even the best cabin air supply system would not be be able to maintain the temperature.

TL / DR

Pressurization failure caused only by a problem with the outflow valves will not necessarily cause cabin temperature to drop to sub-freezing levels, if the heated cabin air supply is otherwise working.

Pressurization failure caused by a total loss of incoming cabin air supply will cause the cabin temperature to fall to very cold levels quickly, with accompanying frosting of cockpit and cabin windows. Likewise for an explosive decompression event caused by a major breach of the integrity of the pressure vessel.

Jim Barrett

C525, no ACM, bleed air used to directly pressurize the cabin with jus a heat exchanger in the engine mount. yeah, blew my mind too.

[procede]

Likewise for an explosive decompression event caused by a major breach of the integrity of the pressure vessel. Not necessarily major. I think a failure of the pneumatic door seal would also do the trick.

[visibility3miles]

the F16 action in intercepting the aircraft had nothing to do with politics or who the owner did or did not donate money to.

If ANY plane violates Washington, DC, airspace without approval, it gets attention, especially if they fly over prohibited airspace.

Yes, this plane was too high to be within prohibited airspace, but it stopped communicating with air traffic control around fifteen minutes after takeoff, according to the newspaper. It certainly didn’t land at its planned destination.

The F 16 action may be due to concern about a hijacking, not who donated money to whom.

[visibility3miles]

JRBarret - How much moisture is there in the heated engine bleed air?

[mnttech]

Jim Barrett nicely stated

[mnttech]

JRBarret - How much moisture is there in the heated engine bleed air?
Not much.... that air can be several hundred degrees.

[RatherBeFlying]

Time of useful consciousness at 28,000 (last reply to ATC at FL277) is about 3 minutes, which should be enough time to get on a mask. Less than 3 minutes later the pilot failed to respond to ATC. It's a coinflip between medical event or pressurisation failure.

Was the oxygen cylinder open? If not, was it in reach of the pilot? We will in due course hear from the NTSB.
​​​​

[JRBarrett]

JRBarret - How much moisture is there in the heated engine bleed air?

Not much at altitude. Even so, with a full ACM that can cool the air using a compressor driving an expansion turbine, there can be a significant amount of water that condenses at the outlet of the turbine, and which is removed by a centrifugal water separator. That is mostly an issue on the ground when the ambient air is very humid.

At altitude, the cabin air supply tends to be extremely dry. Many people tend to have sinus problems when flying for hours in a pressurized cabin. Some aircraft (primarily airliners) have systems to humidify the cabin air.

[galaxy flyer]

Not much at altitude. Even so, with a full ACM that can cool the air using a compressor driving an expansion turbine, there can be a significant amount of water that condenses at the outlet of the turbine, and which is removed by a centrifugal water separator. That is mostly an issue on the ground when the ambient air is very humid.

At altitude, the cabin air supply tends to be extremely dry. Many people tend to have sinus problems when flying for hours in a pressurized cabin. Some aircraft (primarily airliners) have systems to humidify the cabin air.

How much maintenance experience do you have on Citations? I ask because you are wrong on several points. Freon A/C is used to augment cabin cooling and is off at cruise. All Citations use an Air Cycle Machine during cruise for cabin pressurization and temperature control. I have 2,500 hours flying them.

See pages 2-51- 2-57 here

http://www.corporatejetsolutions.com/PDF/Encore%20Manuals/Citation%20Encore%20Operating%20Manual.pdf

[hans brinker]

How much maintenance experience do you have on Citations? I ask because you are wrong on several points. Freon A/C is used to augment cabin cooling and is off at cruise. All Citations use an Air Cycle Machine during cruise for cabin pressurization and temperature control. I have 2,500 hours flying them.

See pages 2-51- 2-57 here

http://www.corporatejetsolutions.com/PDF/Encore%20Manuals/Citation%20Encore%20Operating%20Manual.pdf

CJ3 does not have an ACM....

[what next]

CJ3 does not have an ACM....

We may be nitpicking here, but the CJ3 belongs to the the line of "CitationJets" which are all part 23 certified aircraft, whereas the line of "Citations", to which the accident C560 belongs, are part 25 certified and all of them have, among other differences, an air cycle machine. In my 3.500+ hours on Citations I have had two pressurisation issues so far. One was due to pilot error (because of "finger trouble" the pressurisation switch was selected to "Manual" when really the switch next to it should have been flipped - these things happen when switches are moved without looking) and the other was caused by a faulty outflow valve.

Because it has been mentioned above: 1) The cabin air at altitude is very dry because it always passes through a water separator. 2) A door seal fault is indicated by an amber warning light together with a master caution. There is a secondary (passive) door seal and even a failure of the inflated door seal should not result in a rapid decompression. 3) Some malfunctions of the air cycle machine will automatically switch the system to "emergency pressurisation" mode, which means that the cabin will continue to be pressurised with pure bleed air. Hot and uncomfortably loud (they say) but breathable. 4) The optional freon air conditioner is totally unrelated to the pressurisation system. It is electrically operated and can be used from the ground up to 18.000ft.

[Magplug]

I have never held a US ATPL or flown any jet smaller than a 737 so I am not so familiar with bizjets under US regulations....... Stop me if I get this wrong!

This CJ3 would have been operating under FAR Part 23 with a single pilot permitted by the MTOW being less that 12,500lbs and less than 10 passenger seats. Did I get that right?

FAR Part 23.1457 appears to require a cockpit voice recorder with the functionality described in Part 23.2500 ? Furthermore I don't believe this aircraft would be permitted to operate with a single pilot under any other worldwide jurisdiction (other than those few states that have decided to adopt FAA rules).

BTW.... That's not a question for the engineers !

[vilas]

Now serious allegations are being made against the pilot about on board usage of a drug Oxicontin an habit forming opiate used for pain. Post mortem may be able to throw some light on it.

[hans brinker]

I have never held a US ATPL or flown any jet smaller than a 737 so I am not so familiar with bizjets under US regulations....... Stop me if I get this wrong!

This CJ3 would have been operating under FAR Part 23 with a single pilot permitted by the MTOW being less that 12,500lbs and less than 10 passenger seats. Did I get that right?

FAR Part 23.1457 appears to require a cockpit voice recorder with the functionality described in Part 23.2500 ? Furthermore I don't believe this aircraft would be permitted to operate with a single pilot under any other worldwide jurisdiction (other than those few states that have decided to adopt FAA rules).

BTW.... That's not a question for the engineers !

No. MTOW for the CJ3 is 14K Lbs. We operated the CJ with 2 pilots, and an "SIC required" on the PIC license. All of us were trained as PIC, and qualified to fly as SIC.

[jtgibbs]

Vilas please quote your source.

[galaxy flyer]

I have never held a US ATPL or flown any jet smaller than a 737 so I am not so familiar with bizjets under US regulations....... Stop me if I get this wrong!

This CJ3 would have been operating under FAR Part 23 with a single pilot permitted by the MTOW being less that 12,500lbs and less than 10 passenger seats. Did I get that right?

FAR Part 23.1457 appears to require a cockpit voice recorder with the functionality described in Part 23.2500 ? Furthermore I don't believe this aircraft would be permitted to operate with a single pilot under any other worldwide jurisdiction (other than those few states that have decided to adopt FAA rules).

BTW.... That's not a question for the engineers !

CJs, in later 3, 3+ and 4 exceed 12,500 pounds, but are still Part 23 SP planes. All require type ratings. This was a 560, derivative of the Citation II, with a Part 25 exemption

https://downloads.regulations.gov/FAA-2020-0806-0002/attachment_1.pdf

[hans brinker]

We may be nitpicking here, but the CJ3 belongs to the the line of "CitationJets" which are all part 23 certified aircraft, whereas the line of "Citations", to which the accident C560 belongs, are part 25 certified and all of them have, among other differences, an air cycle machine. In my 3.500+ hours on Citations I have had two pressurisation issues so far. One was due to pilot error (because of "finger trouble" the pressurisation switch was selected to "Manual" when really the switch next to it should have been flipped - these things happen when switches are moved without looking) and the other was caused by a faulty outflow valve.

Because it has been mentioned above: 1) The cabin air at altitude is very dry because it always passes through a water separator. 2) A door seal fault is indicated by an amber warning light together with a master caution. There is a secondary (passive) door seal and even a failure of the inflated door seal should not result in a rapid decompression. 3) Some malfunctions of the air cycle machine will automatically switch the system to "emergency pressurisation" mode, which means that the cabin will continue to be pressurised with pure bleed air. Hot and uncomfortably loud (they say) but breathable. 4) The optional freon air conditioner is totally unrelated to the pressurisation system. It is electrically operated and can be used from the ground up to 18.000ft.

Didn't realize that was a difference between the C&CJ, and I am sure you know/remember more about it than I do, but I flew the Bravo/550 (with ACM) and the CJ3/525 (without) for 8 years & 4500 hours.
But if you want to have an FAA moment, read the MEL for leaking (optional) sink in the CJ lav. "secure door closed and put do not use sign on lav door". Copied straight from the C550 MMEL. But the CJ has the emergency exit in the lav in the back, and the Bravo has it up front. Regulations with holes you can fly an airplane through... (disclaimer, this was true in 2013, after 10 years in service, but maybe fixed 10 years later)

[galaxy flyer]

Vilas please quote your source.


I think this is it. If you don’t like the article, I have it from several pilots who knew him that’s there’s a lot of fact in these accusations.

https://www.the-sun.com/news/8319382/john-rumpel-pilot-jeff-hefner-past-fraud-repairs-crash/

[mnttech]

This CJ3 would have been operating under FAR Part 23 with a single pilot permitted by the MTOW being less that 12,500lbs and less than 10 passenger seats. Did I get that right?
FAR Part 23.1457 appears to require a cockpit voice recorder with the functionality described in Part 23.2500 ?
Just a small note or two here...
Part 23 or 25 is the certification rules for the aircraft, not the rules they are operated under. That would be 91, or 135, or 121 etc. Even a 121 Airline has to operate under parts of 91.
Also, the 23.2500 rule would be for new aircraft after the part 23 re-wriite. The 560 is under 25, up to amendment 17, with a bunch of other rules at Higher amendments, depending on the aircraft SN
See rType Certificate Data Sheets (TCDS) - A22CE Rev 73
t

[jtgibbs]

Vilas I read the article and if true I will be surprised. I personally knew Jeff and while he had a temper, I find many of the accusations to be a stretch. I would also urge you to check the reputation of the us sun as it is reviewed to be tabloid reporting.
I will reserve judgement until the investigation is complete in any accident and will not utilize tabloids to attack any pilot’s character.
just my personal code of conduct.

[Ivor_Bigunn]

I absolutely agree that The Sun is a tabloid, but their long article referenced above by galaxy_flyer includes the following quotes from the judge in a 2017 civil court case against his business partners that Mr Hefner lost:

"In his findings, Judge David Dugan wrote: "There was an abundance of testimony from McBride, MacDonald [...] of Hefner's improper conduct."Much of this testimony was actually corroborated by Hefner’s own testimony.

"These acts include but are not limited to changing locks on hangars and having improper airport access privileges denied to McBride and MacDonald to prevent them from accessing ICC’s business premises; removing and hiding property of ICC [...] denying McBride and MacDonald access to important tax and financial information.

"[And] Hiding aircraft owned by subsidiaries of ICC; pointing a gun at [MacDonald] and threatening the life of McBride and MacDonald on separate occasions; acting in a threatening and belligerent manner to employees of businesses with whom ICC did business; failing to maintain aircraft to an appropriate standard; and making improper unauthorized filing with the Florida Secretary of State’s office."

Hefner twice unsuccessfully appealed the decision.

He later filed for Chapter 13 bankruptcy on March 3, 2021.

The status of the filing at the time of his death remains unclear."




Wow ! It does look as if there is some explaining to come........

IB

[Magplug]

Wow ! It does look as if there is some explaining to come........

If that back-story is true it opens new lines of enquiry for the NTSB team.

Isn't the First Amendment the very reason these tabloids can get away with saying exactly as they like? I choose not to read unsubstantiated tripe written in the gutter press..... it will turn you brain to mush!

[BFSGrad]

Isn't the First Amendment the very reason these tabloids can get away with saying exactly as they like?First Amendment does not negate U.S. libel laws. Tabloids in U.S. are frequently sued for libel.

Article linked in post #94 looks to be well sourced. A basic tenet of public affairs is, if you know there’s negative information regarding your client, flood the media with a positive narrative first; i.e., the “Mr. Safety” stories.

[EDLB]

I assume a CVR was not installed, so the investigation will have not much information beside the two F16 visuals and ATC recordings.

[Fly-by-Wife]

First Amendment does not negate U.S. libel laws. Tabloids in U.S. are frequently sued for libel.
At least in the UK, a deceased person cannot be libeled, nor can the relatives or estate of a deceased person sue for libel. The reason being that Defamation is defined as an act or statement that damages one's reputation. The dead do not have reputations to damage (in the eyes of the law).

[MechEngr]

I assume a CVR was not installed, so the investigation will have not much information beside the two F16 visuals and ATC recordings.

I read a report claiming the NTSB was searching for the recorder; I was unable to confirm anything on the NTSB website.

[Bksmithca]

At least in the UK, a deceased person cannot be libeled, nor can the relatives or estate of a deceased person sue for libel. The reason being that Defamation is defined as an act or statement that damages one's reputation. The dead do not have reputations to damage (in the eyes of the law).
Only prblem I see is it's a UK tabloids reporting on a US Accident so First Ammendment might not apply. The lawyers will get rich arguing the point

[Magplug]

If a UK parented company is doing business in the US it is subject to the laws of that land, including libel actions.

It happens that The Sun newspaper USA has nothing to do with the Murdoch tabloid rag 'The Sun' which is owned by News International. The Sun USA was founded in 1936 as the 'Myrtle Beach News' and is owned by the McClatchy Company of Myrtle Beach SC.

[Obama57]

On more modern aircraft are there design/regulatory mandates to override the throttles when the cabin pressure goes over 10,000 feet? It seems obvious enough. How many crashes would have been avoided by such a mechanism?
G550 if A/P engaged at FL400 or above, low cabin pressure warning, would turn left 90 degrees, descend at Vmo and level off at 15,000/250 kts.

[Magplug]

The Airbus A350 is even smarter. An emergency descent autopilot function is available to the crew for use. When armed the squawk is set to 7700 and TCAS set to look down. The mode is initiated by the crew by selecting speedbrake. The target altitude auto-sets to FL100 or the safest altitude above the MOA from the EGPWS terrain database and the speed bug runs to Barber's Pole -5kts. The NAV initiates a 3nm right offset (presuming the aircraft is on a NAT track). At the target altitude the level off is completed automatically with the speed-target going to Green Dot.

If an imminent cabin pressure above 14,000' is detected the Emergency Descent autopilot system arms. If the procedure is not pilot initiated within 15 seconds the system triggers. The AP/FD engages (if not already) and the sequence above is carried out completely automatically. The mode will even take the appropriate action to a TCAS RAs in descent so it's pretty damn clever.

[Liffy 1M]

Preliminary report here (https://data.ntsb.gov/carol-repgen/api/Aviation/ReportMain/GenerateNewestReport/192300/pdf)

The last transmission from the aircraft was when it was passing through FL280, at 1325 hours. Three minutes later the pilot did not reply to a further ATC instruction, to level off at FL330. No FDR fitted, CVR not found yet.

[Red_giant]

Potentially slow Decompression

[Magplug]

Potentially slow Decompression
Potentially a medical incapacitation or even a subtle fumes incapacitation to name but three possible causes. We understand everything from the crash site is completely destroyed so there is no evidence to learn from. Given that it is probable the cause will remain a mystery.

Here's an idea.... Aside from Helios (where there were several other factors involved), public transport aircraft don't usually suffer from pilot incapacitation due to subtle decompression (due 2 pilots & better alerting systems). Notwithstanding, to make them more robust a downlink of cabin altitude could be added to CPDLC to warn controllers of an impending situation. I hit some turbulence once on the NAT tracks in a 744 and the AP coped well with going up and down +/- 250'. Within moments of hitting the turbulence we got a CPDLC message from Gander requesting..... 'CONFIRM MAINTAINING FL360'. It was comforting to know that Big Brother was watching and Flight Safety was enhanced.

The frequency of decompression accidents is very much higher in the bizjet community, even more so considering the smaller number of flights compared to commercial. As a stop-gap perhaps mandate modified transponders that have their own integral baro capsule. They could be rigged to squawk (say) 7400 in the event of cabin altitude above 14,000 feet. That might save the occasional single pilot 'Zombie' accident. It would certainly alert ATC to the possibility of an unguided aircraft they would need to clear other traffic away from.

Anyone remember the call from ATC... 'Oxygen! Oxygen! Oxygen! '

[Gizm0]

That, Magplug, is an extremely sensible idea. I can see no reason why it should not be adopted (not very expensive) and, in due course, mandated. It certainly might very well have saved Helios and all those poor souls on board. A very loud audio repeater on the flight deck could easily be incorporated - not everyone passes out fully at the same time and at Helios there was evidence to suggest that at least one cabin crew was on portable oxygen. The ATC forward knowledge aspect is also very relevant.
Well done sir / madam for posting one of the very few sensible comments / suggestions seen on PPRuNE in quite a while. Anyone see any flaws with Magplug's reasoning - or indeed have any other forward thinking sensible & practical ideas??

[DaveReidUK]

not very expensive

How much do you think it would cost ?

[Gizm0]

I have no idea Dave - and I am not going to quote the usual phrase of "if you think .... then try an accident". But when you consider that ATC can now see (for example) the preset altitude and the actual pressure setting used (+ a myriad of other stuff) on their screens I am sure the boffins could work something out without it being prohibitive. Cabin altitude is already a recorded parameter on virtually all modern FDRs. And when you consider how much biz jet owners are willing to spend on their expensive kit then such a safety related item would be relative peanuts. Particularly if it was either mandated or would attract a discount in insurance premiums - like many other safety related options do. Think of the days before OFDM was mandated (or GPWS or TCAS or .........).
But what are the general thoughts on Magplug's idea?

[RatherBeFlying]

Many GPS navigators on the market offer an emergency automatic landing capability. It's simple enough to add an altitude sensor open to the cabin that would trigger an automatic landing at a couple thousand feet over where the masks automatically deploy. That would give the crew time to get their act together before the automatics take over.

Agree squawking 7400 or such would help ATC.

[Magplug]

And when you consider how much biz jet owners are willing to spend on their expensive kit then such a safety related item would be relative peanuts.
As has already been discussed... most bizjet owners are successful business people who are not enthusiasts of 'splashing the cash' on equipment (or extra pilots) where they are not mandated. It is an unfortunate reality of both private and commercial aviation that money is only spent on the very minimum levels required by law. (Just as carefully researched maximum FTLs immediately become the new rostering target.)

[gums]

Salute!

I am surprised nobody has mentioned monitorng the "single pilot" as well as the plane. I realize the SLF may not be aviators and would be fairly helpless if the pilot was suddenly incapacitated, but several fairly cheap devices are available if the pilot is dozing off or still can communicate.

The ring I wear for a breathing disorder (COPD) got rave reviews from private pilots flying out west in high terrain. It uses bluetooth to talk with my iPhone on its continuous mode if I wish, but I get alerts when it vibrates fairly strong with or without continuous comm. The pilot reviewers say it tells them when they need supplemental oxygen if their oxygen saturation gets to a specific level, the FAA says - 92% or so, if I remember. The thing also also monitors pulse rate and records for up to 10 hours so you can reconstruct your history later.

Gums sends...

[Magplug]

I have to admit that the B747s 'Pilot Response' warning woke me a few times. With your young colleague on 'controlled rest' in the other seat and the other in the bunk it is rather soporific just staring at empty sky at 04:00 on the body clock. FOs always seemed to sleep about 20 hours a day..... is that a thing?

The Helios aircraft was presumed to have left the KEA hold after overflying LGAV as a result of manual intervention on the flight deck. This was supported by the F16 pilot's observations. There was a steward on the crew with a little flying experience but clearly a 737 with one engine already out was a little bit too much to handle.... (My memories of the 737 recall an absolute trim-pig). The chances of any SLF being able to find the field, let alone the runway are slim to nil.

[Timmy Tomkins]

I have to admit that the B747s 'Pilot Response' warning woke me a few times. With your young colleague on 'controlled rest' in the other seat and the other in the bunk it is rather soporific just staring at empty sky at 04:00 on the body clock. FOs always seemed to sleep about 20 hours a day..... is that a thing?

The Helios aircraft was presumed to have left the KEA hold after overflying LGAV as a result of manual intervention on the flight deck. This was supported by the F16 pilot's observations. There was a steward on the crew with a little flying experience but clearly a 737 with one engine already out was a little bit too much to handle.... (My memories of the 737 recall an absolute trim-pig). The chances of any SLF being able to find the field, let alone the runway are slim to nil.
I think he had a CPL

[Magplug]

Timmy Tomkins You are correct. From the Helios accident report:-

​​​​Cabin Attendant number four (age 25) also held a UK Commercial Pilot License (JAR CPL A/IR) with an issue date of 2 October 2003, and valid to 1 October 2008. His JAA Class 1 Medical Certificate was valid from 15 July 2005 to 17 July 2006.​​​

The accident occurred on 14th August 2005 some 22 months after he gained his CPL. He therefore had some twin prop experience and had passed an IR. I don't recall the job climate at the time but clearly he was still working as cabin crew 2 years after becoming employable as a pilot. He was keeping his medical up to date so presumably still job-hunting.

Notwithstanding his experience..... Helios' last RT communication was at 0620 passing FL290 for 340. The F16 pilot later witnessed a person entering the FD at 0818, some 2 hours later. That's a long time to be waiting to intervene.