Hypoxia Suspected In Mysterious Citation Fatal Accident


The investigation continues into Sunday’s fatal flight of a 1990 Cessna Citation 560, which crashed in Virginia killing all four occupants. Incapacitation due to hypoxia, most likely resulting from a pressurization issue, is strongly suspected, as the Citation pilot stopped responding to radio calls 15 minutes into the flight, according to the National Transportation Safety Board. Also, the Citation apparently followed the lateral track of its flight-planned path, turning toward and then overflying its destination, New York Long Island McArthur Airport (KISP). But it flew the flight-planned path at 34,000 feet and continued on a consistent track until apparently running out of fuel and spiraling to the ground at a high rate of descent.

Further, according to reporting in The New York Times, pilots of F-16 fighters that were scrambled to intercept the business jet (alarming residents and government officials around Washington, D.C., with sonic booms) reported seeing the pilot slumped over the controls and unresponsive to radio calls and flares.

Much of the news coverage focuses on the widely heard and recorded sonic booms, which were authorized by NORAD due to the Citation’s track overflying—but not penetrating—Washington’s restricted airspace, which caps at 18,000 feet. But the unknowns surrounding the circumstances of the actual accident flight are drawing more attention from the aviation community.

As yet unanswered is what caused the Citation to turn toward the destination airport, then fly on at 34,000 feet on what appears to be a direct line back toward the departure airport in Elizabethton, Tennessee (0A9). Perhaps coincidentally, that heading also corresponds closely to the final track of the Runway 24 ILS approach at KISP. Investigators are exploring whether the flight management system (FMS) commanded the autopilot to fly the lateral track of a programmed flight plan after the pilot lost consciousness. As shown on flight tracking service FlightAware, the Citation followed a normally assigned IFR routing, which includes a dogleg over the Sea Isle VOR in southern New Jersey, to help remain clear of more congested airspace farther inland.

The incident is similar to the hypoxia-related Learjet crash that killed golfer Payne Stewart in October 1999. Except in that case, the aircraft did not make any autopilot-generated turns. Intercepting fighters tracked the Learjet on a straight line until it, too, ran out of fuel and spiraled to the ground near Mina, South Dakota.

Some observers (including AVweb readers commenting on our initial coverage of the accident on Sunday night) suggested that the pilot might have included the departure airport in the original flight plan as a check to see if there was enough fuel on board to return—and never removed the waypoint. Thus, the Citation would have continued on autopilot back toward the departure airport at the programmed altitude. After engine flameout from fuel exhaustion, the autopilot would have raised the nose attempting to maintain the programmed altitude until the aircraft stalled and spiraled to the ground.

The aircraft owner, reportedly a pilot, told The New York Times the passengers were his daughter, two-year-old granddaughter and the child’s nanny. They were returning to their home on Long Island, New York, after visiting him at his home in North Carolina.

Mark Phelps
Mark Phelps is a senior editor at AVweb. He is an instrument rated private pilot and former owner of a Grumman American AA1B and a V-tail Bonanza.

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  1. There is another possibility another individual has brought up online. The possibility that the single pilot onboard became incapacitated due to health issues ( passed away) not related to pressurization. The passengers in the passenger cabin may not have realized what may have happened to the pilot prior to the fuel exhaustion. The F16 pilots have only reported the pilot slumped over, nothing said about any passengers. I have flown this type of Citation and the pressurization system is pretty simple and reliable. Also for those who have little experience with FMS systems the flight track shown on FlightAware is easily programmed prior to flight and the autopilot would have followed it quite easily. The 180 degree turn at CCC vor is normal ATC routing in the New York area. Until the voice recorder is recovered, if there is one, and analyzed, we may never get an answer as to why this happened. RIP to those lost, condolences to the families involved.

    • This is small jet. There is no door between the passengers and cockpit. I think passengers probably would have noticed the pilot slumped over the controls for 3 hours.

  2. The BlancoLirio channel has a report on it and oddly the “return” flight track passes directly over the Montebello (MOL) VOR, so precisely that it implies that it was part of a flight plan. Doing so could also have been a simple coincidence as part of being in DR mode, however.

    • If you zoom in on the final part of the straight leg and the spiral on ADS-B Exchange you’ll see it didn’t not directly overfly MOL. Close, but not to it.

  3. “…the Citation, which is not equipped with autothrottles that would have automatically initiated a descent to execute the approach.” Does that mean if the aircraft had been so equipped it could have descended into the heavily populated area surrounding the destination airport?

    • The later Gulfstream airplanes have this feature. The auto-descent is to a preselected altitude, typically 10,000. Then, if it is hypoxia the crew should recover.

  4. If the pilot’s responses ceased only 15 minutes into the flight, it might be that the pressurization system did not fail, but that it was never turned on? I read that hypoxia can occur in minutes, and at the 15 minute point the aircraft was already at 30k feet.

    • Pressurization system is normally on even during takeoff. The system would have to be deliberately turned off by the pilot for this to happen. During normal flight there would be no reason to do so.

  5. In typical media fashion, a key item in the story nationwide was the attempt to attach some dire significance to the “delay” in scrambling fighters to intercept, implying that was both a dire national security concern and a lost opportunity to have prevented the accident.

  6. Mark, who is suspecting hypoxia; the masses of armchair investigators or the real investigators?

    Loss of communication as early as 15 minutes into this flight caught my eye immediately as something potentially other than hypoxia. The small private jet owning community should not be waiting for the final report on this one to have serious conversations with their inner souls about how much they are really saving by conducting single pilot operations. Even with highly experienced pilots as is the case here, they are breaking the redundancy chain. At a minimum, they should have this conversation for the sake of the next, and the next, and the next 2 year old they put on board.

  7. Why do rich clients skimp on having a second pilot onboard a complex aircraft flying in a complex airspace?

    • That depends on the client. A lot of clients I have flown actually want that second pilot on board. According to the DO of a company I flew for, the increase in insurance coverage for single pilot pt 135 jet ops was easily the same amount of money as paying the salary for a first officer. So there may not be that much of a cost saving operating single pilot. I think the single pilot operation was geared more toward owner/operators of those jets certified for that.

  8. In the Payne Stewart Lear jet crash, the pilots stopped responding to ATC less than 15 minutes after departure – both pilots in a 2 pilot crew.

    • In the Payne Stewart crash it was reported that the crew had been flying several legs with the crew emergency oxygen depleted. Without the oxygen, no number of crew members could have saved the flight.

  9. The cause is yet to be determined. My question is since this plane was NORDO since 15 minutes after departure and had been heading dead center toward the DCA TFRs for no less than 20 minutes, why did the military wait so long to scramble the jets, and why did they just feel the need for speed as it was already way past Washington?
    In my mind, this splatters egg all over the DCA defenders faces.
    Don’t even get me started on ALL the erroneous headlines about the “private plane violating restricted airspace”.

    • Nope. The Citation technically had not violated DC airspace. It was flying at a reported 34,000 ft. AGL. The DC restriction is only applicable for flight under !8,000 ft. AGL.

  10. Most (all?) large-cabin long-range business jets are equipped with Emergency/Automatic Descent Mode (EDM or ADM, depending on the manufacturers nomenclature). Above a certain altitude, say 30,000’, the system is armed to recognize a sudden drop in cabin pressure. The autothrottles reduce power to idle, the autopilot turns the plane 90-degree to the left and descends to (usually) 15,000’. It will level off there and increase thrust to maintain 250 KIAS until (hopefully) a pilot is able to take back control.

    Unfortunately, this airplane type has neither autothrottles nor EDM/ADM. Because of this, pilot intervention would be necessary for the plane to begin a controlled descent from 34,000’. Once captured/level, selecting a lower altitude and commanding a vertical mode are required to descend, even in airplanes equipped with autothrottles.

    Pretty safe to say that pilot incapacitation (hypoxia or medical) is to blame in this tragic accident.

  11. Concerning the turn back after reaching destination.
    When I taught IR, I always suggested that a Departure Instrument Approach be added to the end of the FMS route. If an emergency occurred after take off, the pilot flying could access the approach with a simple button press.

    In this accident, was the departure approach added to the flight plan and caused the autopilot to reverse course after overflying the destination and then fly back to the departure airport?

  12. “Also, the Citation apparently followed the lateral track of an instrument approach, turning toward and then overflying its destination, New York Long Island McArthur Airport (KISP). But it flew the “approach” at 34,000 feet and continued on a consistent track until apparently running out of fuel and spiraling to the ground at a high rate of descent.”

    I disagree with your track analysis.

    The airplane followed the flight plan/cleared path. The last part of the plan was SARDI DCT CCC DCT KISP. The airplane smart turned from SARDI-CCC to CCC-KISP, it didn’t line up with an approach. After passing KISP it followed an extended, great circle path from CCC-KISP. If you put that on ForeFlight, and put KISP-0A9 on there as well you’ll see a divergence of about 1º. It is simply an incredible coincidence that it is so close.

    I think my theory satisfies Occam’s Razor as well.

    • That makes sense. I will rewrite that section to replace “instrument approach” with “flight-planned path.”

  13. Lots of good info in all these comments but no one really knows yet. I’m sure they will pin it down. However a few comments noted the auto throttles will reduce power and bring the aircraft to an altitude 10,000 – 15,000 ft and allow pilot recovery from hypoxia.

    But what is the result of a pilot suffering hypoxia for 2+ hours? Can you just snap out of it once you get a normal supply of oxygen or is there brain damage?

    • Steve, the automatic system I mentioned above would immediately descend an equipped airplane (not this accident airplane) to 15,000’ within 15 minutes from 40,000’ (even quicker if a pilot is able to extend speed brakes/spoilers during the episode). So, responsiveness after prolonged exposure would not be an issue in that case.

      Perhaps somebody else could speak to the effects of long-term hypoxic exposure, but I imagine that there is a “point of no return.”

    • Above about 20K, you have just seconds to think logically, then unable to comprehend, then unconscious, then dead, all in a super short time. Higher the quicker it all happens.

      • Roger, according to Wikipedia, time of useful consciousness (TUC) at 22,000’ could be as much as 10 minutes (normal ascent) or as short as 5 minutes (rapid decompression). At 35,000’, those numbers are 30-60 seconds and 15-30 seconds, respectively. And at 40,000’ the numbers are 15-20 seconds and 7-10 seconds, respectively. While unconsciousness certainly occurs quickly at the higher altitudes, many stowaways have survived several-hour flights in the mid-30s. I imagine the outcome isn’t as good after a couple of hours in the upper 30s to low 40s.