V-n Diagram Of Aircraft Pdf
Penny Bozic
Flew into McCarran today and shut the airplane off at the gate, then decided i wanted to check Navigraph Jeppesen KLAS Airport chart to see if gate numbers were showing up, but the Aircraft icon was not visible on the airport plate (?)
On the subject of the airport diagrams that are do not support moving maps is that a Jeppesen issue or is that an issue with your software? In other words does Jeppesen make some plates that support moving maps but not others?
At the time I was actively speaking at web conferences in the US & Europe on the topic of problem solving among other things, and Wald's story was a terrific demonstration of solving (and defining) the right problem. I wasn't aware of anyone who had visualized this, so sometime around 2005 I hastily plotted fictitious red dots on a poorly-chosen commercial aircraft outline and began including this in slide decks and blog posts.
I've received many copyright requests over the years to include the original artwork in books and articles. The image you've seen repeatedly on the socials is from Wikipedia (creator unknown) and is a recreation of my diagram. Look closely in the Wikipedia caption and you'll see me credited.
This page shows the parts of an airplane and their functions. Airplanes are transportation devices which are designed to move people and cargo from one place to another. Airplanes come in many different shapes and sizes depending on the mission of the aircraft. The airplane shown on this slide is a turbine-powered airliner which has been chosen as a representative aircraft.
For any airplane to fly, one must lift the weight of the airplane itself, the fuel, the passengers, and the cargo. The wings generate most of the lift to hold the plane in the air. To generate lift, the airplane must be pushed through the air. The air resists the motion in the form of aerodynamic drag. Modern airliners use winglets on the tips of the wings to reduce drag. The turbine engines, which are located beneath the wings, provide the thrust to overcome drag and push the airplane forward through the air. Smaller, low-speed airplanes use propellers for the propulsion system instead of turbine engines.
At the rear of the wings and stabilizers are small moving sections that are attached to the fixed sections by hinges. In the figure, these moving sections are colored brown. Changing the rear portion of a wing will change the amount of force that the wing produces. The ability to change forces gives us a means of controlling and maneuvering the airplane. The hinged part of the vertical stabilizer is called the rudder; it is used to deflect the tail to the left and right as viewed from the front of the fuselage. The hinged part of the horizontal stabilizer is called the elevator; it is used to deflect the tail up and down. The outboard hinged part of the wing is called the aileron; it is used to roll the wings from side to side. Most airliners can also be rolled from side to side by using the spoilers. Spoilers are small plates that are used to disrupt the flow over the wing and to change the amount of force by decreasing the lift when the spoiler is deployed.
The wings have additional hinged, rear sections near the body that are called flaps. Flaps are deployed downward on takeoff and landing to increase the amount of force produced by the wing. On some aircraft, the front part of the wing will also deflect. Slats are used at takeoff and landing to produce additional force. The spoilers are also used during landing to slow the plane down and to counteract the flaps when the aircraft is on the ground. The next time you fly on an airplane, notice how the wing shape changes during takeoff and landing.
The fuselage or body of the airplane, holds all the pieces together. The pilots sit in the cockpit at the front of the fuselage. Passengers and cargo are carried in the rear of the fuselage. Some aircraft carry fuel in the fuselage; others carry the fuel in the wings.
As mentioned above, the aircraft configuration in the figure was chosen only as an example. Individual aircraft may be configured quite differently from this airliner. The Wright Brothers 1903 Flyer had pusher propellers and the elevators at the front of the aircraft. Fighter aircraft often have the jet engines buried inside the fuselage instead of in pods hung beneath the wings. Many fighter aircraft also combine the horizontal stabilizer and elevator into a single stabilator surface. There are many possible aircraft configurations, but any configuration must provide for the four forces needed for flight.
I have a reasonable understanding of what a V-n diagram shows and what the envelope and the boundaries mean. However, the question I have is how does the weight of the aircraft specifically affect the diagram?
I know that reducing the weight will mean a lower load factor and therefore potentially more manoeuvrability. But is there a mathematical way of showing this? Also, how does the weight relate to lift? Again, lower weight means less lift is needed. But how does that specifically affect the V-n diagram?
When an aircraft is heavier (say wing tanks or fuselage tanks full of fuel), a given amount of pounds of force generated by the wings results in a lower G-load and thus less force on components of fixed weight, like the battery or engine(s). Therefore the mounts holding these parts of the aircraft in place are subjected to less stress. Therefore the maximum amount of force the wing can be permitted to exert --measured in pounds or Newtons, not G's-- can be raised-- again assuming it's the stress on things like the motor mounts, etc that we're concerned about-- and that's why the maneuvering speed (Va) in many aircraft increases as aircraft weight is increased. (Below maneuvering speed, the wing will stall before generating some critical amount of force that has been judged by the designer to be too much.)
A simpler way to state this is that if we are setting the maneuvering speed to protect the mountings of items of fixed weight, then all that matters is the max G-load that we allow the aircraft to develop. When the aircraft is heavier, for any given G-load, the stall speed will occur at a higher airspeed. Maneuvering speed is the speed where the aircraft will stall before exerting so much force that it damages the structure. So if we are setting the maneuvering speed to protect the mountings of items of fixed weight by not allowing the aircraft to exceed some given G-load, then we can increase the maneuvering speed as we increase the weight of the aircraft.
On the other hand, if were worried about ripping the wings off the fuselage-- if that was the limiting factor in setting our limiting speed-- then it wouldn't make any sense to raise our limiting speed as we increase aircraft weight, at least if all the increased weight was going into the fuselage. In a simplified case where the weight of the wing is negligible compared to the weight of the fuselage, when the wing is generating X pounds of lift, the same amount of force is being transferred from the wing to the fuselage, regardless of how heavy the fuselage is and therefore what the G-load is. If the weight of the wing is not negligible compared to the weight of the fuselage, then adding weight to the fuselage means a lower percentage of the wing's lift force will be "absorbed" by the wing itself, and for a given X pounds of lift force generated by the wing, the force exerted by the wing on the fuselage, and the stress on the wing-fuselage connection, will go up as we increase the aircraft weight. In such a case, if the wing-fuselage connection is our critical concern, then it would make sense for the maneuvering speed to go down as the aircraft weight is increased. On the other hand if the extra weight is going into the wing (fuel, external stores hung from the wings) then for a given X pounds of lift generated by the wing, some of the wing's lift force will be "absorbed" by this weight and the total G-load in any given situation will be less and there will be less force transferred from the wing to the fuselage and less stress on the wing-to-fuselage mounting, so again it would make sense to raise the maneuvering speed as we increase the aircraft weight, if areas such as the wing-to-fuselage mounting are the critical concern.
Similarly, if more of the weight is distributed along the wingspan, the bending stress on the wing spars will be less, for a given total force in pounds generated by the wing. So if the wing spars are the critical component of concern that governs our choice of maneuvering speed, then if we increase weight by adding it to the wing, the maneuvering speed should go up, but if we increase weight by adding it to the fuselage, the maneuvering speed should go down.
So, it's complicated. The simplest case is when the limiting concern is the stress on the mountings of items of fixed weight, such as motor mounts, battery brackets, etc, as described at the start of this answer. My understanding is that that is in fact this most common case and explains why on the Vn diagram, the maneuvering speed typically goes up as the aircraft weight goes up. Again, in this case we are simply setting a maximum allowable G-loading.
"Maneuvering speed" is not explicitly shown on the figure linked in the question, but generally, it occurs at the point where the line representing the max G-load allowable meets the curved left edge of the envelope representing the stall, with some extra safety margin added. The discussion above of whether the maneuvering speed Va should be raised or lowered as we add weight to the aircraft, depending on where we are adding the weight, is exactly equivalent to a discussion of whether we should raise or lower the limiting G-load, or neither, as we add weight to the aircraft. Note that on the V-n diagram, adding weight to the aircraft will shift the curved left edge of the envelope representing the stall further to the right. You can see how, if our goal is simply to set the maneuvering speed in a way that prevents the aircraft from exceeding some fixed maximum allowable G-loading, then an increase in weight will automatically change the V-n diagram in a way that increases the maneuvering speed in proportion to the square root of the increase in the weight. However, if the goal is to limit the stress on the wing spars, or the wing-to-fuselage connection, then the situation may be completely different, depending on where we are adding the weight.
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