Maybe only with G-suits? – Although acceleration normal to Earth is not disappeared–your blood, if not most definitely the fluid in your ear canals, still responds to that, no?
I especially can’t see it in propeller aircraft. But I post this query now because I vaguely remember something about John-John night flying, thinking he was pulling up, and splashing. (I guess someone who knows could tell also me how, if that is correct, they found that out.)
ETA: “Invert” in the early 20th century meant “homosexual.” Not what I mean. Although perhaps worth wondering about.
Nobody flies around inverted mistakenly thinking they’re flying right side up.
What non-instrument pilots can do easily if they blunder into clouds is start turning a bit without realizing it. So now they’re in a slight bank. The airplane will descend and speed up a bit. So they think, wrongly, that they’ve simply begun to descend. The cure for that is to pull back a bit.
But that just tightens the spiral. And whatever tended to create the bank at first tends to continue to work to increase the bank. So they think they’re descending more. So they pull back some more.
After about 25 or 30 seconds of this they’re in a 90 degree bank descending like mad and likely to pull a bit more and rip the wings off the airplane.
Like so much in aviation, you can go from fine to utterly ***ked in a very short time.
The rest of the story is that whether an airplane is flying straight and level or is in a properly flown banked turn, the direction you feel as “down” is directly towards the bottom of the airplane, not towards the center of the Earth.
So no, you don’t feel, in either butt or ears, anything about which way the Earth is. At least not while flying a properly flown turn.
Your body responds to the net total of all forces imposed on it. If the aircraft is moving in a straight line at a constant speed, that force will be the force of gravity; otherwise, the aircraft’s accelerations contribute, and can (indeed, will) quickly confuse a pilot without visual reference or blind-flying instruments.
This isn’t really right. In straight and level flight - or indeed in straight flight at any constant rate of climb or descent - “down” will always be toward the center of the earth. This includes inverted flight, and “knife-edge” flight.
I used “down” in quotes as shorthand for “the direction you feel as 'down”, believing that the context made this clear.
I’m definitely saying that in unaccelerated flight, the direction you feel as “down’” is always toward the center of the earth, not towards the bottom of the airplane. Think of a pilot flying straight and level while inverted.
**Xema **is correct. To avoid confusing **Leo **I limited my description to “straight and level and properly flown turns”. In those cases and (unstated by me) in *mostly only *those cases, is the direction of felt “down” *is *towards the bottom of the airplane.
(@Xema: IMO “straight and level” normally implicitly includes “upright”; I would not describe constant altitude, constant heading inverted or knife edge flight as “straight and level” without further qualification. But reasonable minds may differ.)
In other more elaborate regimes of flight, felt “down” can be in darn near any relationship to the aircraft, including towards the side or top of the aircraft. As **Xema **says.
My thinking was that the flight regime of both light plane flyers and airline riders is limited to those simple cases. And even the classic graveyard spiral which Bijou Drains correctly says was JFK Jr’s undoing is an example of that kind of flight. See Graveyard spiral - Wikipedia for more.
All the rest is IMO muddying Leo’s waters unnecessarily. I should have included a parenthetical that I was simplifying things a bit.
I seem to recall an experiment where they took pilots and had them fly a Cessna or the like blindfolded. In no time flat they were often in the “death spiral” or the like.
This is video is probably the best demonstration of why you can’t depend on your sense of up/down when flying as performed by one of the best pilots of all time. Your sense of gravity is not constant and you can literally be at a perfect 1G at any attitude including upside down. Combine that with restricted visibility to the horizon and you can see why you can’t trust your senses to know your true orientation without instruments.
The first post is true, but it doesn’t address LSLGuy’s post. The second completely misses it. Turning the airplane IS accelerated flight. That’s why you can’t “seat of the pants” tell you are in the death spiral - your pants think you are level, and you’re not.
An artificial horizon does exactly that - mirrors the real horizon. However, your vestibular system is a powerful input to spacial awareness, and the artificial horizon is small. If your butt tells you one thing and your artificial horizon tells you something different, it takes a lot of training to ignore your butt and trust the instrument. I liken it to spinning around in circles for 30 seconds then stopping suddenly. Does the world feel like it’s spinning the other way, even though your eyes tell you it’s not? If you had a little 3.5" instrument also telling you otherwise, would that be enough to prevent you from falling down?
That is what artificial horizons are for. They can tell you your true attitude even when the pilot can’t sense it because they are gyroscopic instruments.
In flight training student pilots will wear a type of helmet that only allows them to look down at the instruments. They have to learn to trust their instruments to tell them the plane’s attitude because it is difficult to determine otherwise. The problem gets worse after reaching stall conditions and the plane is literally dropping like a rock. Recovering from that without instruments is a serious challenge as the plane begins to fly again, the pilot senses the return of control but may not be aware of their attitude. They’ll attempt to keep the plane flying straight and level according to what their senses tell them, and soon could be spinning and diving toward the ground.
:eek: I question the safety protocols of that experiment. “Damn, there goes another plane. Guess we better ask for more funding. These next-of-kin payments are killing us.”
The others above accurately covered the basics. Here’s some follow-on details / asides that may be of interest.
In the pre-electronic days artificial horizons were driven by purely mechanical spinning gyros. Which *tended *to remain stable in space and, once manually aligned with the local horizon, would stay that way.
But it wasn’t perfect. Over time mechanical imperfections and other forces acting on the aircraft cause the gyro to drift out of alignment with local vertical/horizontal. So it would have to be periodically re-aligned by making the aircraft straight, level, and unaccelerated followed by resetting the gyro to be aligned with the aircraft which was in turn had just been aligned with the Earth. In early days this was needed every few minutes and in later years more like every hour.
So far so good, but how to do this two-step alignment when cruising for hours in clouds or darkenss over open ocean with no precise way to align the aircraft with the Earth other than the erroneous gyro you’re trying to reset?
So they added a sensor that detects local “down”. Which is the sum of earth gravity and any turning forces on the aircraft. So this sensor is just as prone to getting confused by a spiral dive as is a human butt and inner ear. IOW, it *is *sensing local G forces and could be confused just as you asked.
The way to make the whole system work well is to have the “down” sensor average its reading over several minutes and periodically gently nudge the gyro towards alignment with what it thinks is up/down and local horizontal.
So the gyro provides instant moment-to-moment stability in maneuvers while the “down” sensor provides long term alignment with the real world. Together they create a stable and reliable version of the truth.
And the whole reason all this is necessary is that the human body has a “down” sensor but not a gyro. If we had an internal gyro we wouldn’t need instruments to stay right side up in clouds and/or darkness.