Aces High Bulletin Board
General Forums => The O' Club => Topic started by: Latrobe on February 17, 2009, 12:56:26 PM
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Just a really weird (and possibly dumb) question that popped into my mind this morning. If an aircraft is flying along at 15,000ft level flight continuesly, will that aircraft eventually start to climb higher in altitude due to the Earth being curved and NOT level? Or, are aircraft attitude indicators designed to keep you flying level according to the curvature of the Earth?
My mind comes up with some wacky questions :)
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Not sure about this, but I would think that an altimeter uses gravitational force to calculate altitudes. I assume auto pilot uses readings from an altimeter?
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Altitude indicators go by barometric pressure and require periodic adjustments. Attitude is a gyroscopic measurement.
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Altitude indicators go by barometric pressure and require periodic adjustments. Attitude is a gyroscopic measurement.
Wondered if that may be it as well, but I thought "attitude" was a alcoholic measurement. :D
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Just a really weird (and possibly dumb) question that popped into my mind this morning. If an aircraft is flying along at 15,000ft level flight continuesly, will that aircraft eventually start to climb higher in altitude due to the Earth being curved and NOT level? Or, are aircraft attitude indicators designed to keep you flying level according to the curvature of the Earth?
In aviation feets and flight levels are used to measure altitude. There is a transition altitude at which point the altitude is changed from feets to flight levels and vice-versa. In the USA and Canada the transition altitude is at 18,000ft. Altitude is always dependant on the atmospheric pressure. Below transition altitude feets are used to measure altitude above mean sea level and this requires the pilot to set the local atmospheric pressure. Stantardised pressure is used above transition altitude, which is 1013.25 millibars or 29.92 inches of mercury and altitude is referred to as flight level. Flight levels are not at a fixed altitude above MSL, but change according to the pressure. Because of the stantardized pressure everyone above the transition altitude are flying at similar altitudes. Like wise everyone below transition altitude are flying at similar altitudes as long as everyone is using the local pressure - if someone isn't using the local pressure, he'll be flying either above or below the indicated altitude above MSL. Which can be fatal without ground proximity warning radar (or GPWS) when below indicated altitude.
The short answer to your question is that air pressure along with stantardisation and flight regulations defines the altitude. Above transition altitude aircrafts are not flying at a fixed altitude above the sea and the actual altitude above the sea level depends on the pressure, however due to the stantardisation this is irrelevant. Below transition altitude aircraft are required to use the local pressure for indicated altitude, if they fail to do that then they will not be flying at the indicated altitude above sea level.
Historically, altitude has been measured using a pressure altimeter, which is essentially a calibrated barometer. An altimeter measures air pressure, which decreases with increasing altitude, and from the pressure calculates and displays the corresponding altitude. To display altitude above sea level, a pilot must recalibrate the altimeter according to the local air pressure at sea level, to take into account natural variation of pressure over time and in different regions. If this is not done, two aircraft could be flying at the same altitude even though their altimeters appear to show that they are at considerably different altitudes. This is a critical safety issue.
Flight levels solve this problem by defining altitudes based on a standard pressure. All aircraft operating on flight levels calibrate to this setting regardless of the actual sea level pressure. Flight levels are described by a number, which is this nominal altitude ("pressure altitude") in feet, divided by 100. Therefore an apparent altitude of, for example, 32,000 feet is referred to as "flight level 320". To avoid collisions between two aircraft due to their being at the same altitude, their 'real' altitudes (compared to ground level, for example) are not important; it is the difference in altitudes that determines whether they might collide. This difference can be determined from the air pressure at each craft, and does not require knowledge of the local air pressure on the ground.
Flight levels are usually designated in writing as FLxxx, where xxx is a one- to three-digit number indicating the pressure altitude in units of 100 feet. In radio communications, FL290 would be pronounced as "flight level two niner zero", in most jurisdictions. The phrase "flight level" makes it clear that this refers to the standardized pressure altitude
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Just a really weird (and possibly dumb) question that popped into my mind this morning. If an aircraft is flying along at 15,000ft level flight continuesly, will that aircraft eventually start to climb higher in altitude due to the Earth being curved and NOT level? Or, are aircraft attitude indicators designed to keep you flying level according to the curvature of the Earth?
:lol No, an aircraft trimmed for level flight will not begin to climb because of the curvature of the earth.
Did you notice that your premise contains a contradiction? That's why you were able to reach an absurd conclusion.
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Latrobe...I see what you are getting at....it seems if the plane made a continuously perpendicular to the earth flight, his alt would continually increase and he would eventually be in orbit. That is if he isn't using a standard altimeter and just flying "straight".
Okay, so what about this....if two planes were traveling, one directly over the other....the first at 500 feet and the second at 50000 feet. If both of the planes had to travel from point A to point B staying at the exact orientation throughout. Both starting over point A and finishing over B at the same time....would the higher one have to travel faster to reach point B at the same time? Because of the curvature of the earth, wouldn't he have to cover more distance in the same amount of time?? The same thing with a merry-go-round. The outside seats would go faster because of the same principle....right?
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Latrobe...I see what you are getting at....it seems if the plane made a continuously perpendicular to the earth flight, his alt would continually increase and he would eventually be in orbit. That is if he isn't using a standard altimeter and just flying "straight".
Okay, so what about this....if two planes were traveling, one directly over the other....the first at 500 feet and the second at 50000 feet. If both of the planes had to travel from point A to point B staying at the exact orientation throughout. Both starting over point A and finishing over B at the same time....would the higher one have to travel faster to reach point B at the same time? Because of the curvature of the earth, wouldn't he have to cover more distance in the same amount of time?? The same thing with a merry-go-round. The outside seats would go faster because of the same principle....right?
Yeah... since with the increased radius it's a longer distance. But fuel economy is better up there, so... is it worth the extra speed?
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If the plane wouldn't have to fight earths gravity in combination of thinning atmosphere, a direct flight path would indeed take it to outer space.
Physics dictate that a moving object moves in a straight line unless no force deviates it. In this case both gravity and thinning of atmosphere both force the aircraft to stay inside certain thresholds despite the attempts of the pilot to maintain an absolute level flight in 3D space (relative to earth's orbit and roll of course, nothing we do on this planet really goes directly from point a to point b in true 3D or 4D space).
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It depends on if the treadmill is built to include the curvature of the earth. If the treadmill is truly and definitely flat, than the airplane will be forced to continue completely flat and launch into space. Assuming it could take off, of course.
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It depends on if the treadmill is built to include the curvature of the earth. If the treadmill is truly and definitely flat, than the airplane will be forced to continue completely flat and launch into space. Assuming it could take off, of course.
:rofl
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This is the contradiction:
If an aircraft is flying along at 15,000ft level flight continuously, will that aircraft eventually start to climb...?
The answer is no, by definition.
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Crap, You beat me to it... Once the treadmill gets tossed in there all known physics goes out the window.
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I see a MythBuster episode in the making.
"A plane takes off from San Fran and flies level at 100 ft at after takeoff....."
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This is the contradiction:
He may not have worded it correctly, but it's pretty apparent what he's asking.
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Due to the effect of cetrifugal force, do you weigh more at the poles than you do at the equator?
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There really is no hope for this country if the denizens of a computer flying game are this uninformed on this topic.
If you can't figure it out from the limited education you received in government schools, try google.
Or is there absolutely no desire to make an effort to learn if there isn't going to be a test?
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nm
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Due to the effect of cetrifugal force, do you weigh more at the poles than you do at the equator?
No because gravity is constant.. Created by the mass of the earth...
More mass, more gravity... Less mass, Less gravity...
:rofl funny question tho...
RC
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No because gravity is constant.. Created by the mass of the earth...
More mass, more gravity... Less mass, Less gravity...
:rofl funny question tho...
RC
Yes but centrifugal force directly counters gravity. Remember, the earth spinning at around 1000 mph.
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He may not have worded it correctly, but it's pretty apparent what he's asking.
Ya, English wasn't my best subject :D . I'm sure pretty much everyone understands what I'm getting at.
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Yes but centrifugal force directly counters gravity. Remember, the earth spinning at around 1000 mph.
Yeah, but we are moving at the same relative
speed as our environment, including the atmosphere,
so it seems null...
I forgot what escape velocity is, guessing about
17,000mph.. Thats to escape gravity, and going
opposite of earths rotation...
Damn, you are gonna make me dredge up my
memory of highschool physics, arent ya......
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Damn, you are gonna make me dredge up my
memory of highschool physics, arent ya......
do it man i bet you can't
learn me a few things
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If you can't figure it out from the limited education you received in government schools, try google.
Or is there absolutely no desire to make an effort to learn if there isn't going to be a test?
i dunno, so far the best method of learning i've found is asking a question...asking google is okay, asking here is a helluva lot more entertaining. and if its that necessary to make them figure it out for themselves, answer the question with a couple other questions.
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If an airplane flew truly straight, in terms of outer space and negating gravity, yes, an airplane would begin to "climb" and eventuallly fly out of the Earth's atmosphere. Of course, this is in an entirely theoretical situation.
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All this thread proves is that you should never leave home without you towel. You never know what might happen
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He may not have worded it correctly, but it's pretty apparent what he's asking.
We probably guessed what he meant but flying constantly at 15k would keep the plane in a steady circle since altitude is measured relative to ground level. Absolutely level flight starting from 15k however is different matter.
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"Escape velocity".
Just a really weird (and possibly dumb) question that popped into my mind this morning. If an aircraft is flying along at 15,000ft level flight continuesly, will that aircraft eventually start to climb higher in altitude due to the Earth being curved and NOT level? Or, are aircraft attitude indicators designed to keep you flying level according to the curvature of the Earth?
My mind comes up with some wacky questions :)
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"Straight" is poorly defined and so the original question (the intention, if I understood it) has no correct answer. It would depend on how you define a straight path and in what frame of reference.
Due to the effect of cetrifugal force, do you weigh more at the poles than you do at the equator?
If you mean the acceleration you feel toward the center of the earth then yes. However, what you will perceive as "down" direction will not point toward the center, except exactly on the equator and the poles. The ratio between the centrifugal acceleration and gravity is of the order 10^-20, so you are not likely to feel this (punched with my thick finger on the calculator so I might be off).
Here is another funny tidbit. When you are running, you are "lighter" when you run east, then when you run west.
Okay, so what about this....if two planes were traveling, one directly over the other....the first at 500 feet and the second at 50000 feet. If both of the planes had to travel from point A to point B staying at the exact orientation throughout. Both starting over point A and finishing over B at the same time....would the higher one have to travel faster to reach point B at the same time? Because of the curvature of the earth, wouldn't he have to cover more distance in the same amount of time?? The same thing with a merry-go-round. The outside seats would go faster because of the same principle....right?
Yes, the arc is longer due to longer radius. However, consider this: the length of the arc is proportional to the radius, being the radius of the earth (~6400 km) plus the altidude (500 ft ~ 0, 50kft ~ 17 km), so the ratio between the distances the planes travel is ~(6400+17)/6400 = 1.003. that is less than 1/3 of a percent. If the lower one flies 10,000 km, the higher one will have to fly about 30 km more. For a big jet this is about as big as its holding pattern. Also, he has to climb 17 km and then decent 17 km. That is already more than the difference due to the curvature.
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Due to the effect of cetrifugal force, do you weigh more at the poles than you do at the equator?
yes, about 0.1% more iirc at sea level :aok
edit: I should explain - the earth is bulged around the equator due to its rotation (ie centripetal accel) so at the poles you are closer to the the earth's centre of mass, therefore gravitational force on an object is stronger at the poles than the equator. :)
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It's less homogeneous than that, iirc.
(http://farm4.static.flickr.com/3125/3289859855_b4841f246b_o.gif)
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All this thread proves is that you should never leave home without you towel. You never know what might happen
Exactly. I wear mine as a sling-pack, turban, or cape. How do you like yours?
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Exactly. I wear mine as a sling-pack, turban, or cape. How do you like yours?
Wrapped between my legs - I can tell front and back side from brown / yellowish markers.
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yes, about 0.1% more iirc at sea level :aok
edit: I should explain - the earth is bulged around the equator due to its rotation (ie centripetal accel) so at the poles you are closer to the the earth's centre of mass, therefore gravitational force on an object is stronger at the poles than the equator. :)
Thx RTHolmes. After reading all this "My Physics teacher can beat up your Physics teacher" stuff, it was nice to see someone simply state the obvious. :aok
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Latrobe...I see what you are getting at....it seems if the plane made a continuously perpendicular to the earth flight, his alt would continually increase and he would eventually be in orbit. That is if he isn't using a standard altimeter and just flying "straight".
Okay, so what about this....if two planes were traveling, one directly over the other....the first at 500 feet and the second at 50000 feet. If both of the planes had to travel from point A to point B staying at the exact orientation throughout. Both starting over point A and finishing over B at the same time....would the higher one have to travel faster to reach point B at the same time? Because of the curvature of the earth, wouldn't he have to cover more distance in the same amount of time?? The same thing with a merry-go-round. The outside seats would go faster because of the same principle....right?
NO... the low one hit a mountain :rofl
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Two airplanes circumnavigate the earth at the equator. One is travelling at 20k and the other is travelling at 40k. How much further does the plane at 40k travel?
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I understand completely, like for instance -- if I am walking west- am I walking uphill due to the spin of the Earth? Or the opposite- am I walking downhill if I walk east?
Please do not throw the treadmill equation in, it confuses me, because I am sure at some point the treadmill would be perpendicular to the curvature of the earth - and my drink would fall out of that little cupholder thingy.
:O
NwBie
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you weigh more at sea level than on top of everest because you are closer to the center of the Earth. Gravitational attraction is a function of both mass and distance.
And in answer to the OP you are flying straight....through curved space that is warped by the Earth's gravitation
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Two airplanes circumnavigate the earth at the equator. One is travelling at 20k and the other is travelling at 40k. How much further does the plane at 40k travel?
L=2xPixR=> L2-L1=2xPIx(R2-R1)=2x3.14( 6400km+12km-6400km-6km)=37.68km======>23 miles
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The original question mixes terms that mean different things depending on your frame of reference.
In most aircraft, "trimmed for level flight" means constant airspeed for a given pitch/power setting. That means as a plane flies "level" around the earth, the aircraft will have a miniscule nose-down pitch rate to keep the airspeed constant, keeping it from climbing. This has nothing to do with the attitude indicator.
Now let's consider that attitude indicator... Any attitude system must have a reference plane. In spacecraft, the attitude system is arbitrary, and may or may not be set to precess or rotate in any or all axis to match that arbitrary reference plane. The reference could be relative to the sun, to stars outside our solar system, the earth, even the moon or any other object moving relative to the earth, sun, etc. In an aircraft, the reference plane for the attitude indicator is the earth directly below the aircraft and it is tangential to the surface of the earth (assuming a perfect uniform sphere). Some aircraft systems (usually ones based on a ring-laser gyro) are sensitive enough to detect the earth's natural wobble and rotation around the sun and must be specifically programmed to cancel that out, and are therefore programmed to precess as required to always reference the tangental plane directly below the aircraft. Cheaper attitude gyros simply precess to reference "down", ie. the relative vector of the local gravity. This is not a problem if the plane is usually in straight and level flight for most of the flight, but it can be a problem if the plane is maneuvering wildly or spends a lot of time in a constant turn. In those cases, the attitude gyro will precess to reference the aircraft's attitude as "level", even if it's in a turn. This is of course not good, which is why those types of gyros have caging knobs so you can re-cage them as required during flight.
The practical effect is that in an aircraft, if the pilot keeps the attitude gyro "level", he will not climb because the attitude gyro is generally set up to reference straight down, not reference an arbitrary absolute plane or attitude reference geometry. A vehicle that has a gyro that references an arbitrary but absolute geometry, would fly "straight" reference to that plane if the attitude reference was kept "level", and it would therefore climb (or dive, roll, yaw, etc) relative to the earth if it's absolute attitude was held constant without regard to the presence of the earth.
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Two airplanes circumnavigate the earth at the equator. One is travelling at 20k and the other is travelling at 40k...soo....WHY do the Jonas Brothers suck?
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Yeah, but we are moving at the same relative
speed as our environment, including the atmosphere,
so it seems null...
I forgot what escape velocity is, guessing about
17,000mph.. Thats to escape gravity, and going
opposite of earths rotation...
The minimum speed needed to accelerate an object not to fall back on Earth is 17000mph, doesn't matter in what direction is launched if is out of atmosphere and the friction with the air doesn't slow it down. From poles to equator the spinning speed of any point on surface of the earth grows from Zero mph @ poles to 1400 mph @equator.Now, if you launch a rocket at the equator estwards ,you have to accelerate it from 1400mph to 17000 mph,takes less fuel, less working time for engines which burns tons of fuel every second, it can lift more usefull load. Same rocket from poles needs to accelerate from 0-to 17000mph, so it takes more energy, and launching it westwards from equator against earth spinning direction , start from minus -1400mph to 17000mph,takes lot more energy. That's why are launched as close as possible from equator from Florida,French Guyana and mostly eastwards .
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My Brain Hurts
(http://www.ichlache.com/wp-content/2007-04/tumbs/tmb_brain-hurts.jpg)
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As you can see with my cheap-o 1337 paint skillz... due to current effects we have, no, it will maintain "level" flight...
(http://i435.photobucket.com/albums/qq73/TheKinSlayer_1993/Untitled.jpg)
:salute
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That's why are launched as close as possible from equator from Florida,French Guyana and mostly eastwards .
Except Israel that launches its satellites westward. Somehow, I get the feeling that a rocket launched from Israel, that heads east toward Iraq and Iran will not be appreciated.
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Just a really weird (and possibly dumb) question that popped into my mind this morning. If an aircraft is flying along at 15,000ft level flight continuesly, will that aircraft eventually start to climb higher in altitude due to the Earth being curved and NOT level? Or, are aircraft attitude indicators designed to keep you flying level according to the curvature of the Earth?
My mind comes up with some wacky questions :)
was it, at any time, on a treadmill?
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Off topic a bit, but this subject makes me think of another physics question that haunts me. Water in a lake more or less "self-levels". What about water in a river? Is its surface "sloped" downhill/downstream? It can't really "self-level" like water in a lake, unless it undulates or "stair-steps"... I realize it's constantly moving, but in a slow-moving stream I'd think it would level out quicker than it would flow downstream. What about a lake with an entry and exit stream? Does the water slope downhill in the top stream, level out in the pond, and then slope downhill again as it exits the pond?
Anyway, sorry for the hijack- just another "head-ache" question...
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Off topic a bit, but this subject makes me think of another physics question that haunts me. Water in a lake more or less "self-levels". What about water in a river? Is its surface "sloped" downhill/downstream? It can't really "self-level" like water in a lake, unless it undulates or "stair-steps"... I realize it's constantly moving, but in a slow-moving stream I'd think it would level out quicker than it would flow downstream. What about a lake with an entry and exit stream? Does the water slope downhill in the top stream, level out in the pond, and then slope downhill again as it exits the pond?
Anyway, sorry for the hijack- just another "head-ache" question...
When i first navigate through Panama Canal,working on cruise ships, i read in daily informative flayer about the Canal .I was surprised to find out the level of the Pacific waters are higher than Atlantic in that zone. If would have been built like the Suez Canal without locks, the water from Pacific would flow into Atlantic.
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Waters of the oceans arent nearly level. Look it up on an atlas, it's pretty dramatic.