Unresponsive C560
 

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.

DC Sonic Boom/Citation Down in VA
 

Sonic boom heard across D.C. region caused by military flight, Md. officials say

That'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...ginia-maryland

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

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).

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.

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....

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

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

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

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?

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.

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

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

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 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.

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

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.

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?

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.

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.

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.

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.

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

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.

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.

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...4-03-15-US.pdf), 2012 - Metroliner from Narrabri to Sydney (page 19 in this report: https://www.laserpointersafety.com/r...-096-final.pdf), 2018 - Qantas (https://www.heraldsun.com.au/news/vi...8f00fb35c44504).

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.

The Kalitta 861 report should render any reader speechless. Slightly non-responsive as you can’t lose what you never had.

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).

Flightaware.com Track
 

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/...700ZZ/0A9/KISP

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.)

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.

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.

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.

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.

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