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Post by the light works on Sept 18, 2016 23:45:07 GMT
I was thinking about artificial horizons in airplanes, today, and I realized I couldn't remember whether the artificial horizon showed true to the ground, or true to the G-forces in the aircraft. and then considering it would theoretically be intended to indicate the plane's angle relative to the ground, how one would build a mechanical instrument that would not be confused by G-forces.
anyone got some expertise to input on the question?
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Post by GTCGreg on Sept 19, 2016 0:24:15 GMT
I was thinking about artificial horizons in airplanes, today, and I realized I couldn't remember whether the artificial horizon showed true to the ground, or true to the G-forces in the aircraft. and then considering it would theoretically be intended to indicate the plane's angle relative to the ground, how one would build a mechanical instrument that would not be confused by G-forces. anyone got some expertise to input on the question? The atrificial horizon shows the attitude of the plane (pitch and roll) in respect to the ground. I suspect new ones are completely solid state, but the older ones used gyroscopes and did not depend on gravity. |
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Post by the light works on Sept 19, 2016 2:48:00 GMT
I was thinking about artificial horizons in airplanes, today, and I realized I couldn't remember whether the artificial horizon showed true to the ground, or true to the G-forces in the aircraft. and then considering it would theoretically be intended to indicate the plane's angle relative to the ground, how one would build a mechanical instrument that would not be confused by G-forces. anyone got some expertise to input on the question? The atrificial horizon shows the attitude of the plane (pitch and roll) in respect to the ground. I suspect new ones are completely solid state, but the older ones used gyroscopes and did not depend on gravity. that makes sense. though that leaves the question of whether a solid state device exists that has the same inertial characteristics as a gyroscope. |
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Post by silverdragon on Sept 19, 2016 7:09:00 GMT
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Post by the light works on Sept 19, 2016 13:58:30 GMT
interesting, though wiki pages don't do good stream of consciousness. |
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Post by silverdragon on Sept 20, 2016 9:31:49 GMT
I put it up as a reasonably good place to start... it gives the terminology used in AHRS systems.
There are more and more solid-state systems much like a pad that can tell attitude if you twist the pad.
Some of them also use Satellite technology to correct small errors, some use Radio signals from ground based systems, some use onboard maps, radar, and a whole host of other systems to auto-correct small interdependencies.
The art of the "Glass cockpit" has come on a hell of a lot with micro-chip technology that can be mush[?] better than Gyro precession [sp?] because it doesnt "creep" under extended tilt.
[note, spell chuckler has taken a holiday whilst it updates... "mush better"?... wassat den?.. ]
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Post by the light works on Sept 20, 2016 14:43:08 GMT
I put it up as a reasonably good place to start... it gives the terminology used in AHRS systems. There are more and more solid-state systems much like a pad that can tell attitude if you twist the pad. Some of them also use Satellite technology to correct small errors, some use Radio signals from ground based systems, some use onboard maps, radar, and a whole host of other systems to auto-correct small interdependencies. The art of the "Glass cockpit" has come on a hell of a lot with micro-chip technology that can be mush[?] better than Gyro precession [sp?] because it doesnt "creep" under extended tilt. [note, spell chuckler has taken a holiday whilst it updates... "mush better"?... wassat den?.. ] gyros are an interesting critter. the physics of them fall under a "we know forces you don't know" sort of thing. but yeah, in flight, you are putting "down" in some pretty strange places, sometimes. I can see aerobatics confusing a gyroscope, unless the gimbal mounts are all that and a tin of biscuits. |
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Post by GTCGreg on Sept 20, 2016 15:27:29 GMT
I put it up as a reasonably good place to start... it gives the terminology used in AHRS systems. There are more and more solid-state systems much like a pad that can tell attitude if you twist the pad. Some of them also use Satellite technology to correct small errors, some use Radio signals from ground based systems, some use onboard maps, radar, and a whole host of other systems to auto-correct small interdependencies. The art of the "Glass cockpit" has come on a hell of a lot with micro-chip technology that can be mush[?] better than Gyro precession [sp?] because it doesnt "creep" under extended tilt. [note, spell chuckler has taken a holiday whilst it updates... "mush better"?... wassat den?.. ] gyros are an interesting critter. the physics of them fall under a "we know forces you don't know" sort of thing. but yeah, in flight, you are putting "down" in some pretty strange places, sometimes. I can see aerobatics confusing a gyroscope, unless the gimbal mounts are all that and a tin of biscuits. They call it gimbal limit. You exceed it and the "This Side Up" label no longer applies. |
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Post by the light works on Sept 20, 2016 15:57:58 GMT
gyros are an interesting critter. the physics of them fall under a "we know forces you don't know" sort of thing. but yeah, in flight, you are putting "down" in some pretty strange places, sometimes. I can see aerobatics confusing a gyroscope, unless the gimbal mounts are all that and a tin of biscuits. They call it gimbal limit. You exceed it and the "This Side Up" label no longer applies. that happens with people, too. |
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Post by silverdragon on Sept 21, 2016 6:26:07 GMT
They call it gimbal limit. You exceed it and the "This Side Up" label no longer applies. that happens with people, too. I know people like that... one of them may be me?. I have heard pilots state never trust an artificial horizon if you can look out the window. Its there really when you cant see much outside and your doing flat and level passenger stuff and they are about to serve the soup?. As for my first flight in a Chipmunk, the pilot was explaining the controls, the artificial horizon was explained as "If it turns all brown, were going down." he then proceeded to show me gyroscopic Precession by spinning the plane through a barrel roll, at which point the thing turned into a spinning marble, as did my Lunch. A lot of the flying that day was VFR, we had our own "Box" out over Southport beaches, as long as we stayed over that part, no one would bother us. It was fun... |
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Post by the light works on Sept 21, 2016 15:25:16 GMT
that happens with people, too. I know people like that... one of them may be me?. I have heard pilots state never trust an artificial horizon if you can look out the window. Its there really when you cant see much outside and your doing flat and level passenger stuff and they are about to serve the soup?. As for my first flight in a Chipmunk, the pilot was explaining the controls, the artificial horizon was explained as "If it turns all brown, were going down." he then proceeded to show me gyroscopic Precession by spinning the plane through a barrel roll, at which point the thing turned into a spinning marble, as did my Lunch. A lot of the flying that day was VFR, we had our own "Box" out over Southport beaches, as long as we stayed over that part, no one would bother us. It was fun... don't know if it is still there, but there used to be a public fighter jet dogfight facility in Texas. they had a bunch of gently used trainers with electronic simulation rigs. they'd take the customers up above a 1000 foot floor, and turn them loose to play high dollar laser tag. they said non-pilots generally beat out private pilots, because the non pilots tended to use the plane as their basis for up and down, where the private pilots tried to use the planet as a reference. obviously things would be different at lower altitude where you have to worry bout banging into the thing, but at high altitude, you simply rotate the plane until the target is above your cockpit and then pull back to bring your gunsight to him. - even if that means the planet is above you. |
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Post by silverdragon on Sept 26, 2016 10:03:07 GMT
An airline pilot wrote that on this particular flight he had hammered his ship into the runway really hard. The airline had a policy which required the first officer to stand at the door while the passengers exited, give a smile, and a "Thanks for flying XYZ airline." He said that in light of his bad landing, he had a hard time looking the passengers in the eye, thinking that someone would have a smart comment. Finally everyone had gotten off except for this little old lady walking with a cane. She said, "Sonny, mind if I ask you a question?" "Why no Ma'am," said the pilot, "What is it?" The little old lady said, "Did we land or were we shot down?"
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Post by Cybermortis on Oct 10, 2016 12:21:12 GMT
I've read several stories of RAF pilots in the 30s and early 40s flying into clouds in formation, then flying out of the clouds to discover they were headed straight for the ground or upside down. Sometimes both.
The reason was that they failed to look at the artifical horizon, relying instead on their own senses, and gentle turns pulled enough G force to fool then into thinking they were in level flight.
This seems to have been most common with pilots who went from biplanes to monoplanes, or were asked to try night flying for the first time. Those pilots were more used to using visual clues than instruments.
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Post by oscardeuce on Oct 21, 2016 3:12:32 GMT
I've read several stories of RAF pilots in the 30s and early 40s flying into clouds in formation, then flying out of the clouds to discover they were headed straight for the ground or upside down. Sometimes both. The reason was that they failed to look at the artifical horizon, relying instead on their own senses, and gentle turns pulled enough G force to fool then into thinking they were in level flight. This seems to have been most common with pilots who went from biplanes to monoplanes, or were asked to try night flying for the first time. Those pilots were more used to using visual clues than instruments. Called the "Death Spiral" It is very hard to override your orientation to gravity. You have to believe your instruments, not your body. |
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Post by c64 on Nov 6, 2016 21:28:39 GMT
The classic artificial horizon uses a Gyroscope. When the avionics is fired up during the pre-flight checks, the artificial horizon adjusts itself horizontally. If the airplane isn't standing on levelled ground, manual corrections must be made. Sometimes, runways are located on the sides of hills but the parking places are usually levelled so you must calibrate your instruments before taxiing to the runway. Planes have crashed because the pilots didn't wait for the avionics to spin up completely before taxiing onto a sloped runway.
A common Gyro stays accurate for a couple of hours, good enough for normal purposes.
Hard manoeuvres can throw a Gyro off easily. Stunt airplanes can only be flown by sight and jet-fighters have a special radar capable to detect the horizon to recalibrate.
Since gravity is nothing but an acceleration force, gravity forces are mixed with forces caused by motion acceleration. There is no way to figure out the attitude of an airplane using gravity. You can only watch your bearing (compass) and altitude to figure out if your artificial horizon is off. If your artificial horizon is de-calibrated, you must use the climb indicator to gain a safe altitude and figure out what to do.
A Gyro-compass is different. It is not trying to keep pointing into its original position as the artificial horizon. It is affected by the force on the gyro caused by the spinning earth. After an hour or two it points North since this is the only stable position where the rotation of the earth doesn't drag on the spin of the Gyro.
The same effect is ever de-calibrating an artificial horizon so a classic one is only good for up to 8 hours.
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