
Auto-GCAS Saves Unconscious F-16 Pilot - jakarta
http://m.aviationweek.com/technology/auto-gcas-saves-unconscious-f-16-pilot-declassified-usaf-footage
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kevinastone
4 confirmed "saves" since late 2014!!

Ignoring the loss of life, according to Wikipedia, the cost of an F-16 is just
under $20M. If we consider that two full years, it's earning $40M/year!

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jsmthrowaway
"Earning?"

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kctess5
Presumably, they're implying that loss prevention is functionally equivalent
to earning income, w.r.t. the bottom line.

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Unklejoe
There's something extremely gratifying about watching things do what they were
designed to do, and do it beautifully.

You always hear stories about engineering failures, but it's good to see such
a nice success story.

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tim333
It would be nice to get some footage of self driving systems saving lives.

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steveplace
there's a handful out there already

[https://www.youtube.com/watch?v=9I5rraWJq6E](https://www.youtube.com/watch?v=9I5rraWJq6E)

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tdicola
That's pretty amazing, especially considering how fast everything is
happening. It has to feel pretty good for the engineers, etc. who worked on
this system and see it saving lives like this.

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Neil44
Incredible to think about the kind of systems that were available when the F16
was created compared to what it's flying with now.

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trentnelson
Nominal 5G recover says the article... 9.1 on the pull-up says the HUD!

Side bar: favorite F-16 HUD footage:
[https://youtu.be/2uh4yMAx2UA?t=164](https://youtu.be/2uh4yMAx2UA?t=164)

Incredibly chilling.

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itengelhardt
The article states that the pilot awoke mid-recovery and increased to 9.1G

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Declanomous
I wonder if the 5G limitation on the avoidance system is to allow pilot a
chance to recover from GLOC, or if it is due to other concerns like the
structural integrity of the aircraft or more unpredictable handling at more
than 5Gs. Can more than 5 sustained Gs kill someone if they aren't conscious
and able to counteract the blood pooling in their lower extremities?

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trentnelson
5G is definitely more tolerable than 9G, especially in a GLOC situation, yet
still allows for a pretty aggressive avoidance maneuver.

The 5G limit is going to be decided in concert with the minimum altitude and
an upper speed limit.

GLOC would be most common at the merge, where they'll be at corner speed (the
speed that allows them to get the tightest turning radius whilst bleeding the
least amount of energy) and need to instantaneously load to 9Gs.

So from an engineering perspective, I'm sure they massaged the G limit,
minimum recovery altitude and maximum likely speed into the most optimal set
of parameters, with 5G offering a good trade-off between minimum recovery
altitude and pilot comfort.

The planes themselves are G-rated to 9Gs, which is entirely a flight control
system limit, because the bag of bones in the front seat tends not to do so
well over 9Gs for sustained periods -- but the actual airframe will be able to
sustain much higher before structural failures will start occurring.

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jschwartzi
How would you do system-level testing on this system? Obviously there's going
to be a simulator, but would you ever install it in a plane and dive at the
ground?

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Sharlin
Test pilots have done much more dangerous things. The pilot still has time to
recover from a faux "uncontrolled" descent if the system appears to not work.

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knodi123
Plus, I'd bet a million dollars that the GCAS kick-in threshold is
parameterized, and the test pilots had it set to kick in at a much higher
altitude than the final product.

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srb24
Didn't the Stuka Dive Bomber have something (admittedly analogue) similar in
the 1930's?

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Tuna-Fish
Sort of. They had a system where a single lever would release bombs, then
level and recover. Their system would not engage after the pilot passed out,
rather engaging the system would make the pilot pass out. This allowed them to
"safely" dive bomb at 90-degree angle, making them much more accurate than any
other dive bomber from the period.

The downsides were that the automatic recovery was very-high-g, almost
guaranteed to make the pilot pass out, and flying slowly with the pilot passed
out in a very predictable pattern over enemy troops was not very good for you,
especially after the enemies figured out the recovery pattern.

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popeshoe
I'm kind of astounded that modern planes haven't had this feature for a long
time

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drunken-serval
It requires the aircraft to be aware of terrain around it. Most aircraft do
not have topographical maps in their computers.

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sanj
I believe it work on a radar altimeter.

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trentnelson
The terrain following radar feature that has been in fighter jets since the
late 60s uses radar -- as the name implies, and serves a similar purpose. It
allows the pilot to set an altitude and a "comfort" level regarding how
aggressive the autopilot can be with regards to avoiding danger (basically,
how quickly the plane can pull Gs to avoid terrain, and how many Gs it can
pull).

That works well when you're straight and level, attentive, and the radar can
point at the ground. This system can't rely on radar exclusively though
because the aircraft may not have its radar pointing at the ground (as in the
video, the aircraft is inverted in a pretty steep dive).

So, they have to factor in precision INS/GPS and known topology to assess
terrain altitude in order to perform collision avoidance.

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Animats
The F-16 system doesn't rely on radar, although it can use it, because
fighters often fly with radar off. It tells the enemy you're coming. It's
based on INS/GPS and a terrain database obtained from radar scans of the Earth
made from the Space Shuttle in the 1990s.

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_petronius
Dumb question, maybe, but how long before that data becomes inaccurate? Or
rather, are there any areas where the change in elevation for the purpose of
this system could be big enough in a 30ish year timescale that it would cause
problems?

I assume no geological process alters the land drastically enough, quickly
enough, that you'd notice, but what about water-level changes (dammed
rivers?), melting glaciers, etc? Is "hard" ground consistent enough that no
human processes are going to cause the data to diverge from the database
drastically without the chance to update the database with new topographical
surveys?

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crististm
Can you differentiate between an aggressive maneuver that results in loss of
consciousness and a similar maneuver followed by a controlled one that looks
like flight into terrain but is not ?(e.g. because pilot does aggressive
acrobatics). Or two aggressive maneuvers followed by almost level flight but
where one of them is with loss of control.

I'm interested what would be the cues that can be taken from controllers and
plane attitude that can make the software say something in the line of "this
guy seems lost, I'd better pay more attention". Of course nose down is one,
but what about more subtle ones?

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shoo
in principle the software could be forecasting an envelope of possible future
trajectories of the aircraft given the current state. if we detect that we are
about to commit to a state where our only remaining future options all involve
colliding with terrain, we make an intervention.

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vilhelm_s
Yes, I think this is how it works.

> The [Aircraft Response Model] is a sophisticated simulation of the F-16,
> running at a real-time rate. "It's a fairly complicated algorithm that
> tracks fuel-burn, takes information from the stores management system [about
> weapons weight and drag], and even accounts for system processing delays,"
> said Mark A. Skoog, USAF's AFTI F-16 test director. "Using the aircraft's
> current state, the ARM computes a full six-degree-of-freedom simulation
> during a roll to wings-level. At wings-level, [ARM switches] to a 2D-type
> recovery--a second-order modeling of the jet's pitch response. It calculates
> how much [kinetic] energy it can trade for altitude until the jet reaches a
> desired zoom-climb speed, then holds that speed."
> ([http://www.f-16.net/f-16_versions_article8.html](http://www.f-16.net/f-16_versions_article8.html))

So the system continually computes the best trajectory for avoiding the
ground, and takes over if that trajectory ever goes below the currently
selected "minimum descent altitude". Pilots can adjust the MDA depending on
how low they plan to fly.

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Kerrmit
There is a really good discussion of this on the Aviation Week site:
[http://aviationweek.com/technology/auto-gcas-saves-
unconscio...](http://aviationweek.com/technology/auto-gcas-saves-
unconscious-f-16-pilot-declassified-usaf-footage)

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jheriko
"What would be really useful would be a way for controllers on the ground (not
ATCs) or in chase planes to assume control of airliners performing
erratically, not responding to calls from ATC, air defense fighters, or their
corporate offices. THAT could have averted the Germanwings crash and the 9/11
collisions without the need for highly classified hardware in every airliner."

this comment really resonated with me. we have the tech for this right now, we
had it 10 years ago too... remote piloting drones is now a completely day-to-
day occurance. you could argue we had it down "well enough" in the 80s even

someone somewhere should be pushing for this. i'd never thought of it before,
but now i've seen this comment i'm wondering why we don't have this sort of
thing. especially in light of 9/11...

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harshreality
That (remote control of civilian aircraft) would be such a rich target for
hackers. I would much rather see the civilian aerospace industry implement
carefully audited, carefully deployed autonomy (starting with partial
autonomy), rather than remote control.

Civilian aerospace does not have the security focus that the military has.
Even if you solve the security problem from airplane black-box controller all
the way to the remote control cockpit, and even if you find civilian pilots
willing to fly planes when a remote pilot can override them at any time...
there are there costs of satellite communications, costs of designing and
installing black-box remote controls on dozens, even hundreds of types of
commercial aircraft, and costs of staffing remote control cockpits with pilots
who can fly every type of commercial plane, 24/7.

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Kerrmit
There is a really good bit of info about this on the Aviation Week site.
[http://aviationweek.com/technology/auto-gcas-saves-
unconscio...](http://aviationweek.com/technology/auto-gcas-saves-
unconscious-f-16-pilot-declassified-usaf-footage)

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joering2
_In a little less than another 2 sec., as the now frantic instructor makes a
third call for the student pilot to pull up, the Auto-GCAS executes a recovery
maneuver at 8,760 ft. and 652 kt.

The student pilot at this point comes around and pulls back on the stick,
momentarily increasing Gs beyond the Auto-GCAS standard recovery level of 5 to
9.1._

Since he came around "at this point" and seeing he still had few seconds left
to zero, we don't know with 100% certainty that AGCAS was truly pilot's only
option.

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rurounijones
Auto-GCAS started pulling out at 8,760 feet ASL and bottomed out at a hair
under 3,000ft AGL (Judging by the Radar altimeter).

It looks like the pilot start pulling back on the stick at about 6,690ft ASL
(Based on the G-Meter going above 5Gs). If the pilot had woken up at that
point and immediately pulled back then the AGL clearance drops to about
1,100ft AGL.

Then we have to consider the fact that the plane was already pulling up when
the pilot yanked back on the stick. Had the Auto-GCAS not already been pulling
the plane up then the pilot would have been lower when he started the
recovery.

The "At this point" in the article is not well worded because "At this point"
actually looks to be a second or so after Auto-GCAS activated which, when
plummeting towards the ground at 650 knots in a 55 degree dive. is basically
another 500'ish feet lost

All in all this implies HEAVILY that even if the pilot recovered without Auto-
GCAS the margin between survival and lawn-darting would have been a LOT less
than 1000ft which is far too close for comfort.

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bemmu
To me it's impressive how fast he still responds after losing consciousness.
If you've ever fainted, there's this period where you don't know where you are
or even WHO you are, let alone being able to fly a plane.

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kbart
True, but that's what reflexes are for.

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dtparr
It's probably fortunate that the GCAS had already rolled him back, otherwise
the reflex to "pull up" would have been disastrous.

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gcp
Would it have overruled the pilot input if that would have been the case?

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AstralStorm
No, this system only countermands order to fly into ground, not other high G
manoeuvres. The 9 G would probably end up snapping wings or in an uncontrolled
roll.

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trentnelson
F-16s are G-limited to 9G. You can happily pull 9G day in, day out. The actual
G loading the plane is certified for would be much, much higher than this
(probably at least double).

