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Hi all,

How do you turn on the cockpit G-meter?

And in real life, when in a climb you loose a G, and when in a dive you gain a G. Is the cockpit G-meter supposed to show you the -/+ G when performing vertical maneuvers? What is the difference between "radial G" and "Cockpit G?"

http://navyflightmanuals.tpub.com/P-1276/Fig-1-Vertical-Plane-Maneuvering-Egg-8.htm

Thanks,

hawker111

 

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I don't understand the original question of "how do you turn on the g-meter". In the sim, it is always on. In real life, it will be one of the loads on a circuit breaker switch.

The accelerometer always shows you the actual load on the aircraft, so in level flight you will see 1 g. But the 1 g of lift is canceled out by the 1 g of the earth, so you fly level instead of pitching up in a 1 g loop.

So if you pull 2 g per the meter, you will start pitching up in a 1 g loop, but as you approach 90 degrees, gravity is aligned with the drag vector and perpendicular to the lift vector. At that point you will be pitching in a 2 g loop if you can still maintain 2 g while climbing vertically. At the top of the loop, if your meter still indicates 2 g, gravity will now add performance, pulling you into a 3 g loop.

The 2 g you see through the entire loop is what is indicated on your instrument. Its purpose is to show the load on the wings so that you don't break them.

Radial g is the actual acceleration parallel to the lift vector that acts on the radius of the turn or loop. You must use trigonometry to solve determine the radial g taking into account the angle between the lift vector and the pull of gravity. Radial g determines the actual radius of the turn. So, holding constant indicated g through a loop produces the egg in the diagram. You need to hold constant radial g to make a true circle.

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This pdf has an excellent section describing radial g and shows the vector geometry that takes into account lift and gravity to determine the resulting radial g: http://www.flightlab.net/Flightlab.net/Download_Course_Notes_files/8_Maneuvering.pdf

In a flat circle, the radial g is parallel to the ground, and therefore perpendicular to gravity. So you wouldn't think gravity would have anything to do with radial g, but it does! Since the aircraft has to maintain 1 g parallel to gravity to keep the circle flat (no altitude change), the aircraft must bank at a certain angle to split its lift vector between holding altitude and providing radial g. This presents a problem when analyzing aircraft performance: If someone says an aircraft can sustain a 9g turn, is it 9gs of force on the wing or 9gs of radial g? Generally, when they say a 9g turn, I would expect that to be indicated g, so the actual turn is the radial g of a triangle using the Pythagorean theorem (c^2 = a^2 + b^2) where the indicated g is the long side of the triangle. So for level turns, the actual radial g used to determine the turn radius and turn rate (deg/sec) is: square root ( (indicated g)^2 - gravity (1g) ). For 9g, the radial g is: (9^2 - 1^2)^0.5 = (81 - 1)^0.5 = 8.94.

If we choose (or observe) the indicated g and we know the turn is flat, there is a unique angle of bank that satisfies this condition that can be solved for using trigonometry. The trivial solution is at 1g, your bank must be zero degrees to fly level, so your radial g is 0 giving you a turn rate of 0 and an infinite turn radius. At the same time, it is impossible to fly a level turn at 90 degrees of bank because 100% of the lift vector is going into the turn leaving no lift to provide 1g to maintain altitude. But for 9g, the angle of bank = arcos (1g/9g) = 83.6 degrees, which is pretty darn close to 90 degrees when you are in the cockpit.

Edited by streakeagle

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Was the original question how to turn using a g-meter?

Traditionally when using the word "turn", this implies a flat turn. So more important than the g meter is the rate of climb indicator. For a given speed and g-indication, you have to maintain a certain bank as described above. But you don't need a g-meter at all to perform a level turn. Bank as desired and pull back on the stick just enough to hold the rate of climb to zero. As long as the rate of climb is zero and the angle of bank is constant, the indicated g must remain constant as determined by the angle of bank as discussed above.

This has a nice graph of bank vs g load: http://avstop.com/AC/FlightTraingHandbook/loadfactorsinsteepturns.html

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Streakeagle,

I'm flying WOV and I would like the Gs I am pulling to be displayed at the bottom of the screen. At the bottom of the screen there is a translucent box that shows:

Speed:
Altitude: (in red color)
Heading:
Throttle:

Is it possible to display Gs in a translucent box at the bottom of the screen?

Thank you,

hawker111

 

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No.

That's what's instrument panels are for

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It is possible to see the g load at the top of the screen via the debug mode. I don't know what is/isn't possible with modding the normal on screen data since I rarely used it and never modded it.

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Flight / HUDData.ini

[Debug]
DisplayDebug=FALSE

change FALSE for TRUE

 

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