Armed F16 Supersonic Intercept of Unresponsive Cessna | Hacker News Reader

Armed F16 Supersonic Intercept of Unresponsive Cessna

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19 pointsdjyaz120010 comments

This was not a typical sluggish wayward Cessna 152 or 172 with a cruise speed of 122 knots that tend to violate airspace by ignorance. The Cessna 560 Citation V Business Jet cruises at 430 knots/Mach 0.755 and can probably fly faster. I wish news articles would include the model family in the headline.

At Mach 0.755 with supersonic barrier being at Mach 1.0, it becomes obvious why it had to be a supersonic intercept.

> The Citation 560 business cruises at 430 knots and can accelerate to Mach 0.755 and probably faster.

430 knots is about Mach 0.75 at the Citation’s cruising altitude of 45,000 ft.

As the other commenter mentioned, I think that it's important to note that this Cessna is not a little prop plane, but rather a light business jet, likely with multiple people on board.

FYI: The Cessna in question was a Citation jet that went unresponsive and crashed in a Virginia forest later. Before it crashed it flew over DC causing this incident.

Sounds like a zombie plane (AFIAK all jet zombies have been oxygen/pressurization failures) but why the extreme descent at the end rather than simply gliding in once the engines ran out of fuel?

Because autopilot tries to correct the plane, it doesn't have any logic for 'run out of fuel'. And without the engine power any action only destabilise the plane further. Also even without the autopilot the planes aren't stable at flight (besides brobably An-2?) and are flying in gigantic sea of air which has its own tides, waves, turbulences, zones of higher/lower pressure... Look at that wiki article, probably a similar situation.

https://en.m.wikipedia.org/wiki/1999_South_Dakota_Learjet_cr...

Edit: and even if everything is 'good' the unconscious pilot's body can brush against the stick (bump from turbulence eg) and force autopilot to disengage (or it was already disengaged by itself by being not able to correct the plane course) and push (quite literally) the plane to the downward spiral.

While the autopilot doesn't understand out of fuel it does understand angle of attack and shouldn't depart controlled flight in an effort to maintain altitude. Or perhaps the autopilot doesn't know what to do and turns off.

I do think you might have a point about the body causing a disengagement.

> shouldn't depart controlled flight in an effort to maintain altitude

Aircraft isn't inherently stable in a level flight, otherwise there would be no need for autopilot. There are constant small corrections.

And when the engines dies the plane starts to drop the nose but not with an exactly 0 degree roll, because nor the weight is distributed ideally nor the atmosphere is an ideal gas. And while I don't know how far the plane should be out of the flight parameters for the AP to disengage, you should remember what it is still tries to correct the plane (while not yet disengaged) but the dwindling engine power (and hence airspeed) make the control surfaces less effective, so now the AP needs to over-correct and this how you end with rudder and elevators stuck in weird positions and sending the plane anywhere but the stable gliding path.

Though in this case it's less probable becaue looks like the engines were still working, if I understood some sources right.

Track: https://flightaware.com/live/flight/N611VG/history/20230604/...

Registration: https://registry.faa.gov/aircraftinquiry/Search/NNumberResul...

Aside from shuttle launches, first sonic boom I've ever felt. I couldn't guess what would rock this whole row house like that!

The F-16 is a pretty small jet, comparatively. I wonder how different other jets would be.

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