Auto-GCAS Saves Unconscious F-16 Pilot
m.aviationweek.com
m.aviationweek.com
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!
https://en.wikipedia.org/wiki/Value_of_life#Life_Value_in_th...
You always hear stories about engineering failures, but it's good to see such a nice success story.
Side bar: favorite F-16 HUD footage: https://youtu.be/2uh4yMAx2UA?t=164
Incredibly chilling.
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.
Within the cockpit, on the left side, there's a CAT switch that's used to switch between CAT-I (lighter loadouts, such as A-A) which permits more G-intensive maneuvering, and CAT-III (external tanks or A-G ordinance).
As far as sustained loads higher than 5G's, I could see the potential to kill someone, but I would also guess that the more immediate threat after G-LOC is probably the ground.
Most likely there is a test mode that raises the altitude floor/projected flight path at which it takes over. You could then perform the level-off at a safer altitude.
So maybe one way to test this on a real plane would be to trick the software into thinking the terrain is 5000 feet higher than it is. Then it can execute the maneuver against a safe fake "ground", still giving the test pilot time to intervene if it doesn't work properly.
https://www.nasa.gov/offices/ipp/centers/dfrc/technology/DRC...
Essentially what you'd expect, in software then models then UAVs then full-scale planes with test pilots and finally roll-out to service aircraft.
https://www.warhistoryonline.com/war-articles/ju-87-diving-p...
Edit: It would be engaged after dropping bombs; not when the pilot was unconscious.
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.
[0] https://en.wikipedia.org/wiki/Terrain_awareness_and_warning_...
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.
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?
The aviation industry is veeeerry conservative, not to mention hesitant to retrofit perfectly functional airplanes.
On the other hand, fighters are expected to fly fast and aggressively close to terrain. The goals of the F-16 auto-GCAS are
1. Do No Harm (don't initiate a maneuver that causes a crash)
2. Do Not Interfere (the pilot may be in an aggressive combat maneuver)
3. Avoid Ground Collisions
The conflict between 2) and 3) is tough. The rule of the F-16 system is not to interfere until a crash is less than 1.5 seconds away. This was established by flight testing with fighter pilots flying aggressive profiles that might be used in combat.
Larger aircraft are seldom flown that aggressively. Nor do they have the power and maneuverability to get out of trouble in 1.5 seconds. Today's GPWS and EGPWS systems provide up to 60 seconds of time from the warning to airplane impact. The FAA says "The GPWS mandate reduced CFIT (controlled flight into terrain) accidents from about 9 per year in the seven years immediately preceding the mandate to about 4 per year after. This rate has remained fairly constant". So there's room for improvement through automated recovery that isn't last-second.
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?
> Auto-GCAS continuously compares a prediction of the aircraft’s trajectory against a terrain profile generated from onboard terrain elevation data.
> 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)
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.
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...
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.
You could crash a plane into the ground and nobody on board could do a thing about it.
You could crash every plane into the ground at once.
Maybe that's preventable by more automated safety systems that override if you're going to crash, but there are other equally bad options and I doubt we could block them all. Flying planes out over the ocean until fuel runs out, for instance.
Writing UAS software is hard. Only operating UAS in warzones helps with the overheads for this. Effectively "drone-ifying" a commercial airliner is a complete nightmare which would probably require government assistance to implement in the form of cutting of red tape or funding the handling of existing red tape.
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.
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.
Without that he would have taken an extra second or two to reorient himself and take appropriate action.
That delay, plus what I wrote above would make it a certainty in my mind that he would have had an unscheduled plane to ground rendezvous without the Auto-GCAS.
Yet it won't take over until it really, really has to. Pilots can fly close to terrain.
It's interesting that the GCAS took over based on data other than the radar altimeter. There's no radar altimeter data when the plane is on its back, because the downward-pointing radar is looking in the wrong direction. Note that the GCAS arrows are moving in before the radar altimeter data reappears.
High corner speed entry into the merge as well, should have been around 420-440 at that altitude, he was nearly at 500 at the break.