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DC Sonic Boom/Citation Down in VA

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DC Sonic Boom/Citation Down in VA

Old 5th Jun 2023, 13:35
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Originally Posted by what next
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?
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Old 5th Jun 2023, 13:38
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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.
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Old 5th Jun 2023, 13:44
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Originally Posted by 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?
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.

Last edited by Feathered; 5th Jun 2023 at 13:57.
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Old 5th Jun 2023, 13:46
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Originally Posted by Feathered
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.
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Old 5th Jun 2023, 14:42
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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.


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Old 5th Jun 2023, 15:28
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Is a loud buzzer that goes off at say 12,000 feet cabin pressure a thing? I don't fly pressurized aircraft myself.
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Old 5th Jun 2023, 15:42
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Originally Posted by island_airphoto
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.
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Old 5th Jun 2023, 16:01
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Originally Posted by what next
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 ďU.S. officialĒ 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. Thatís 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.
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Old 5th Jun 2023, 16:30
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Originally Posted by BFSGrad
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...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).
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Old 5th Jun 2023, 16:34
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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.

Last edited by Magplug; 5th Jun 2023 at 19:15.
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Old 5th Jun 2023, 19:15
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Originally Posted by what next
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 canít lose what you never had.
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Old 5th Jun 2023, 23:10
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Originally Posted by 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.
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).
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Old 5th Jun 2023, 23:30
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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



Last edited by Lake1952; 6th Jun 2023 at 02:36.
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Old 6th Jun 2023, 00:02
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Originally Posted by Magplug
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.)



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Old 6th Jun 2023, 00:34
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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.
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Old 6th Jun 2023, 02:53
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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.
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Old 6th Jun 2023, 03:17
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Originally Posted by 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.
Apparently you donít 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.
Iím 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.
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Old 6th Jun 2023, 04:04
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Originally Posted by 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.
One doesnít 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 thereís not too much thatís 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 itís all free.
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Old 6th Jun 2023, 05:10
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Originally Posted by Magplug

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.
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Old 6th Jun 2023, 11:34
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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 wouldnít become an unguided missile
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