![\"\"](\"https:\/\/joeclarksblog.com\/wp-content\/uploads\/2011\/07\/Vgn-Diagram.jpg\" "\\"Vgn")
<\/a>The Vgn Diagram<\/p><\/div>\n
This example of a Vgn diagram shows an airplane in the utility category.\u00a0 Load factors determine the category of operation; for normal operations, the maximum g-load is +3.8g and -1.52g.\u00a0 For utility operations, the numbers are +4.4g and -1.76g.\u00a0 For acrobatic aircraft, the maximum permissible positive loads are +6g\u2019s and -3g\u2019s.\u00a0 Here is another practical bit of knowledge\u2014most human beings become uncomfortable at loads over 2g\u2019s.\u00a0 This is what tends to keep us operating in \u201cthe heart\u201d of the envelope, or right in the middle of the green area.<\/p>\n
On the Vgn diagram, the horizontal axis depicts speed while the vertical shows G, or load factor.\u00a0 The generic Vgn diagram above shows the numbers for a relatively heavy and fast airplane.\u00a0 As depicted from this chart, normal cruising speed is near 180 mph, Vne is just over 224 mph, and stall speed is 64 mph.<\/p>\n
To determine the stall speed as 64, you enter the chart on the vertical axis at the 1g line.\u00a0 Moving across until the 1g line intersects the accelerated stall speed curve gives you the stall speed of the aircraft in a wings level attitude at 1g.<\/p>\n
In maneuvering flight, a pilot flying the airplane in a 60-degree angle of bank turn would have a load factor of 2g\u2019s.\u00a0 Similarly, as for the 1g stall speed, enter the chart at the 2g line on the vertical axis and go across until you reach the accelerated stall curve.\u00a0 This gives you a stalling speed of 92 mph.<\/p>\n
The important thing about the accelerated stall curve is this: below the speed of 136 mph (Va), the wing will stall before doing damage to the aircraft.\u00a0 In this example, the illustrated envelope shows the numbers for an aircraft flying in the utility category.<\/p>\n
At speeds less than 136 mph, moving up the chart along increased g-loads, the pilot\u2019s pencil point will cross into the clear space before going through the orange \u201cStructural Damage\u201d area of the chart.\u00a0 In this orange area, at speeds greater than 136 mph, a pilot can damage the airframe.<\/p>\n
This damage may not be obvious to the eye, but has in fact, occurred.\u00a0 The ugly thing about damage of this sort is that it decreases, or shrinks, the available range on the Vgn diagram.\u00a0 This is similar to the idea of taking some of your mother\u2019s favorite silverware and bending it back and forth.\u00a0 You can do this for so long before the utensil breaks.\u00a0 It is the same with the aircraft structure.<\/p>\n
At speeds above 162 mph, the damage goes beyond structural and into the realm of actual failure.\u00a0 Flying anywhere into the red on the chart is\u2014well\u2014bad.\u00a0 It could actually result in the airplane coming apart in-flight.\u00a0 This is something you do not want to experience while sitting in the airplane.<\/p>\n
As mentioned, most of us are comfortable up to 2g\u2019s.\u00a0 Stay inside the green and life is good.\u00a0<\/p>\n
-30-<\/p>\n
\u00a92011 J. Clark<\/em><\/p>\n Note: please go to <\/em>my blog<\/a><\/em>\u00a0to view vids and photos\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0\u00a0<\/em>Subscribe by email<\/a><\/p>\n","protected":false},"excerpt":{"rendered":" When I learned how to fly in 1971, I was a kid who really did not know much about anything, but thought I knew everything.\u00a0 When it came to airplanes and flying, I knew even less than I realized.\u00a0 When … Continue reading