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Florianopolis
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Simulators and Spatial Disorientation

Mon Oct 05, 2020 3:52 am

I've been wondering about something and would like to tap into the forum's collective wisdom.

TLDR: Do simulators contribute to spatial disorientation problems because they intentionally utilize our vestibular weaknesses to create illusions of flight? Every time an airline pilot goes back for a sim ride, his or her brain is being trained to accept the wrong vestibular messages as correct.

Every pilot from Private Pilot training on up learns about spatial disorientation and vestibular illusions. Our inner ear gets confused between acceleration and attitude. There's even a whole section in the AIM. For instance, the "Somatogravic illusion" cited in the Atlas 3591 accident at Houston is described in the AIM: "A rapid acceleration can create the illusion of being in a nose up attitude. The disoriented pilot will push the aircraft into a nose low, or dive attitude. A rapid deceleration by a quick reduction of the throttles can have the opposite effect, with the disoriented pilot pulling the aircraft into a nose up, or stall attitude."

Much professional pilot training is in full-motion simulators. These ride on hydraulic Stewart Platforms that can pitch, roll, and yaw the whole simulator to mimic flight attitudes, but they can only rotate; they cannot translate (NASA has an exception). Accelerations are all faked: when you accelrate in level flight in the sim, the sim pitches nose-up, and for deceleration it pitches the sim nose-down. In other words, the simulator intentionally creates the vestibular illusions confusing acceleration and attitude that we are hoping pilots will not confuse in the real airplane.

I know we're supposed to "trust the instruments", and I suppose it's possible that feeding our brain confusing motion information will reinforce that point in training: no matter what your body is telling you, fly the instruments. Old WWII-era Link trainers could be made to do all sorts of pitch and bank while the student pilot inside was ignoring that to fly his instruments. But in modern sims, we're intentionally feeding pilots' inner ears with the wrong acceleration/attitude information, and teaching their brains to accept them as correct.
 
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Starlionblue
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Re: Simulators and Spatial Disorientation

Mon Oct 05, 2020 6:27 am

It's an interesting question.

Faked acceleration is quite realistic. The body has no mechanism that can differentiate between acceleration comes from gravity (pitching the sim up to simulate accelerating down the runway) or from increasing forward speed (accelerating down the runway in the aircraft). In the same way that if you were in space, riding a hypothetical 1G thrust spaceship, the body can't tell the difference between that g force and standing on the ground on Earth.

It isn't perfect of course, but personally, I find the experience very immersive. "Breaking the illusion", for example if the instructor freezes the sim as you're accelerating down the runway, can be quite disconcerting. The visuals are frozen but the body feels as if it is decelerating as the panic box slowly pitches forward to neutral.

Furthermore, we are trained to discard all "vestibular messages" (I love this phrase) when they conflict with the instruments. I don't think it matters whether these messages are generated by fake motion or real motion.

The one area where the sim feels less than realistic is taxiing. But it isn't exactly something that needs super accurate representation.
Last edited by Starlionblue on Mon Oct 05, 2020 6:51 am, edited 2 times in total.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
CanadianNorth
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Re: Simulators and Spatial Disorientation

Mon Oct 05, 2020 6:45 am

Good question, and I'm not sure the answer. My amateur opinion though is I don't think the typical human brain can really tell enough of a difference, considering the lack of being able to tell the difference without matching clues from other senses is what causes a lot of disorientation problems in the first place.

I've had the opportunity to do some training in the big boy simulators twice now and both of them blew my mind with how real they felt.
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Woodreau
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Re: Simulators and Spatial Disorientation

Mon Oct 05, 2020 1:19 pm

While the simulator can represent acceleration and deceleration, the simulator cannot simulate sustained g forces like zero g Negative g Or more than 1 g after it reaches the limits as to how far it can pitch on its axis.

This does present a training limitation when trying to do deep stalls or unusual attitude recoveries from an inverted state.

During enhanced envelope training we’ll approach stall at FL350 get the stick shaker but instead of recovering we keep forcing the aircraft into a deep stall. You’ll end up with an aircraft that’s in a relatively level attitude but the flight path vector will be pointed towards the ground.

Apply TOGA thrust but observe how little the engines affect the attitude of the aircraft and does little to slow or stop the altitude tape from indicating the aircraft is doing anything other than plummeting towards the ground.

Recover by forcing the nose of the aircraft to the flight path vector (“unload - pitch to zero lift vector” the instructor coaches you) to regain the airspeed to reattach the airflow to the wing to get the airplane flying again.

During that maneuver the g forces in the simulator do not correspond to what we should be feeling. So during the exercise the instructor has other pilot read the g-forces off the g-meter that we are supposed to be feeling. “Oh look at that - you exceeded 2.5g (or -1g) and “broke” the plane. Lets see if you can do that again but stay within in the g limits next time..... “

you definitely didn’t feel that 2.5g or -1g exceedance in the simulator. The inner ear is a poor instrument anyway for that.

Would you know if you were falling if you were inside an airplane that is accelerating towards the ground at 9.8m/s^2? For all you know you’re weightless and can float around freely inside the airplane but won’t know you’re falling until the plane experiences a sudden deceleration when it gets to the ground.
Last edited by Woodreau on Mon Oct 05, 2020 1:28 pm, edited 3 times in total.
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CosmicCruiser
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Re: Simulators and Spatial Disorientation

Mon Oct 05, 2020 1:20 pm

AS Starlionblue said it's done very well and I always found it as real as it can be. The only inaccuracy I ever saw was making tight turns taxiing and looking out the side window. The projection could cause a little dizziness for a split second but that's all I ever saw.
 
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Starlionblue
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Re: Simulators and Spatial Disorientation

Mon Oct 05, 2020 1:53 pm

CosmicCruiser wrote:
AS Starlionblue said it's done very well and I always found it as real as it can be. The only inaccuracy I ever saw was making tight turns taxiing and looking out the side window. The projection could cause a little dizziness for a split second but that's all I ever saw.


Plus you can't look beyond a certain angle sideways. It always hits me when I look out the side window before taxi. Or as you say when making a tight turn and needing to look sideways and back a bit. :)

Woodreau wrote:
While the simulator can represent acceleration and deceleration, the simulator cannot simulate sustained g forces like zero g Negative g Or more than 1 g after it reaches the limits as to how far it can pitch on its axis.

This does present a training limitation when trying to do deep stalls or unusual attitude recoveries from an inverted state.

During enhanced envelope training we’ll approach stall at FL350 get the stick shaker but instead of recovering we keep forcing the aircraft into a deep stall. You’ll end up with an aircraft that’s in a relatively level attitude but the flight path vector will be pointed towards the ground.

Apply TOGA thrust but observe how little the engines affect the attitude of the aircraft and does little to slow or stop the altitude tape from indicating the aircraft is doing anything other than plummeting towards the ground.

Recover by forcing the nose of the aircraft to the flight path vector (“unload - pitch to zero lift vector” the instructor coaches you) to regain the airspeed to reattach the airflow to the wing to get the airplane flying again.

During that maneuver the g forces in the simulator do not correspond to what we should be feeling. So during the exercise the instructor has other pilot read the g-forces off the g-meter that we are supposed to be feeling. “Oh look at that - you exceeded 2.5g (or -1g) and “broke” the plane. Lets see if you can do that again but stay within in the g limits next time..... “

you definitely didn’t feel that 2.5g or -1g exceedance in the simulator. The inner ear is a poor instrument anyway for that.

Would you know if you were falling if you were inside an airplane that is accelerating towards the ground at 9.8m/s^2? For all you know you’re weightless and can float around freely inside the airplane but won’t know you’re falling until the plane experiences a sudden deceleration when it gets to the ground.


Ah yes. I remember this. Indeed then it doesn't feel like the real thing would.

But we're not flying fighter jets. For the vast majority of training we're not going to hit the simulated g limit. :)
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
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Florianopolis
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Re: Simulators and Spatial Disorientation

Thu Oct 08, 2020 6:52 pm

Thank you to all for sharing your thoughts
 
VSMUT
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Re: Simulators and Spatial Disorientation

Thu Oct 08, 2020 8:30 pm

They work well while flying, but many pilots get sick while taxiing the simulator.
 
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Starlionblue
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Re: Simulators and Spatial Disorientation

Fri Oct 09, 2020 12:57 am

VSMUT wrote:
They work well while flying, but many pilots get sick while taxiing the simulator.


Yuuuuup!

I don't often get sick in "normal" operation, but if there's a reposition, especially when you are pulled back to the departure end after a rejected takeoff (AKA "slingshotting"), I can feel a bit queasy. Most instructors are kind enough to tell you to close your eyes before they do it.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Redbellyguppy
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Re: Simulators and Spatial Disorientation

Fri Oct 09, 2020 5:25 am

It’s quite real in the air. But taxiing... ugh. Vomitado. That was the worst part of all of my type ratings.... taxiing.
 
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Starlionblue
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Re: Simulators and Spatial Disorientation

Fri Oct 09, 2020 8:13 am

First time in the A350 sim. We started taxiing and soon I heard and felt the traditional "ka-donk... ka-donk" of rolling over the taxiway centerline lights. So I subconsciously turned slightly right to get off the lights. But I kept hearing and feeling. Turned slightly more right. Still hearing and feeling. What...?

Voice from behind me: "I know you're trying to avoid the centerline lights. Believe me, you are off them. One of the weird things about this sim is that it models the small gaps between concrete surface plates in the taxiway as if they are great big trenches..."

Ok...


Redbellyguppy wrote:
It’s quite real in the air. But taxiing... ugh. Vomitado. That was the worst part of all of my type ratings.... taxiing.


To me, it feels like you're taxiing a bar of soap. Sliding around and the visuals don't always quite track. You move the tiller and it doesn't quite follow.

Once you've slowed down during the landing roll has a bit of the same weirdness. Harder to stay on centerline compared to the real aircraft because pedal inputs don't quite have the same effect, or are delayed slightly or something. Blech...
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Woodreau
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Re: Simulators and Spatial Disorientation

Fri Oct 09, 2020 6:59 pm

Wait till you get in a ship simulator - I set in sea state 7 in the simulator because someone asked how bad the weather could get in the sim...., so while the 360-degree exterior screen display is pitching up and down as the ship plows thru the sea in all directions. the bridge deck doesn't move as it's fixed to the same ground as the building. the helm, quatermaster and boatswain's crew is all fine and all - they're focused on the helm and engine controls, the charts. The conn, though - the movement the eyes were telling him was going on but the ears not - was too much, he quickly transitioned shades of green as blood drained from his face, reached for the trash can and emptied his lunch in to the can...
Bonus animus sit, ab experientia. Quod salvatum fuerit de malis usu venit judicium.
 
Redbellyguppy
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Re: Simulators and Spatial Disorientation

Sat Oct 10, 2020 6:03 pm

I bargain with the check airmen... please take us off motion when we exit the runway snd I promise I won’t puke at the gate...
 
LupineChemist
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Re: Simulators and Spatial Disorientation

Sat Oct 10, 2020 11:28 pm

Woodreau wrote:
Wait till you get in a ship simulator - I set in sea state 7 in the simulator because someone asked how bad the weather could get in the sim...., so while the 360-degree exterior screen display is pitching up and down as the ship plows thru the sea in all directions. the bridge deck doesn't move as it's fixed to the same ground as the building. the helm, quatermaster and boatswain's crew is all fine and all - they're focused on the helm and engine controls, the charts. The conn, though - the movement the eyes were telling him was going on but the ears not - was too much, he quickly transitioned shades of green as blood drained from his face, reached for the trash can and emptied his lunch in to the can...


I work on FNPT and FTD sims (so no motion aside from vibration for helps) and even then I swear I feel motion and disoriented just from the visual response.

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