New answers tagged

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Well, if all you care about is the fan performance by itself, then you've pretty much got it. Maximize the component cycle efficiency and maximize the propulsive efficiency and that's it. But if you want to start getting more real-world, then things to think about: Off design conditions. You can perfectly optimize efficiency at one condition (i.e. for a ...


1

The amount of time and manpower required to remove empty seats before a flight, transport them to the plane's next destination (presumably on another aircraft), then reinstall necessary seats for the next flight with 450 passengers (instead of this flight's 300 pax) would far exceed any potential cost savings of removing them for the flight. (Oh, don't ...


3

The Cessna 172S has more power (180hp vs 160hp for 172R) and higher MTOW (2550lb vs 2400lb for 172R). This means that folks used to rotating at 55 knots IAS in earlier models would be closer to stall if taking off "clean". Another way of doing it would be to add 5 knots and rotate clean at 60 knots. Vx is also a bit higher in the 172S at 62 knots ...


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Alternate Take-off is a reduced power option feature, similar to flex thrust on turbofans. The aircraft manufacturer will provide performance data applicable to the reduced power setting that can be used when circumstances permit. It's all about reducing wear and tear by not running the engine as hard if it's not essential. The Max Continuous power setting ...


3

A fan blade at the front or turbine blade at the back of a jet engine is a small aerofoil surface which is fixed to the main shaft and spins with it. By contrast, a stator vane is a similar aerofoil surface fixed to the outer casing and remains static. Why do that? The spinning blades of a given stage cause the airflow to start spinning, and that slows the ...


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Technically speaking any airplane generates maximum lift just before the wings come off. Whether that is interesting to obtain or not, depends on your need for adrenaline. During a normal flight in a one engine GA airplane, the moment at which most lift is created is during the first few seconds after rotation. In more agile airplanes like military jets, ...


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The two drawings in the question are confusingly wrong, as far as the names of the lines is concerned. What is called the "relative wind flowing over the wing" and the "total" is actually the chord line. The reason it is not the "relative wind flowing over the wing" or "total" is because it does not show the actual ...


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As some other answers have hinted, the question suffers from the misconception that the physical location of each of the vector arrows, including the small "spanwise" arrows, is intended to show the physical location on the wing where the airflow is moving in some given direction. That is not the intent at all. Any one of the vector triangles is ...


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Thanks to @JanHudec for reminding me that the graph is for a level flight. To keep the flight level at low speeds, the Angle of Attack(AoA) needs to be increased, meaning Cl (coefficient of lift) must be increased and so the lift-induced drag ( proportional to Cl^2) is high at low speeds. With the increase of speed, AoA decreases to keep the flight level, ...


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This happens because Angle of Attack required to maintain flight at a given weight decreases with the increase of speed. As for the zero-lift Tr, also known as "parasitic drag", while its coefficient is a constant, its formula is not: it actually has a cube of velocity.


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Plugging in some values using a True Airspeed calculator seems to confirm Peter Kampf's conclusion that the "steps" are indeed coinciding with transonic flight at various IAS and altitudes. There for, there is no "over lapping" of the curves, though they appear to be on the graph. One might suggest the flattening of the curve once the ...


5

As an airplane approaches Mach 1, all pressure changes grow with the Prandtl-Glauert factor of $\frac{1}{\sqrt{1-Ma^2}}$. Therefore, the lift curve slope increases so the wing produces more lift at the same angle of attack and dynamic pressure the closer its Mach number is to 1. On wings with thicker airfoils and higher aspect ratio the maximum lift ...


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what is causing the "corners" that we see at the following points? Compressibility. Close to Mach 1 the lift curve slope increases according to the Prandtl-Glauert rule with the factor $\frac{1}{\sqrt{1-Ma^2}}$. Since the X-axis shows indicated speed, the Mach 1 point moves left with increasing altitude. Technically, those corners should also be ...


1

Transport airplanes have lateral C of G limits in terms of x distance from the centerline, but this only a certification requirement (related to roll authority in a critical case situation) and is only expressed for the flight crew as a fuel imbalance limit, fuel being the dominant factor, and is not accounted for in weight and balance data that the crew ...


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To analyze the impact of a crosswind takeoff on performance, it is necessary to break down the effects on each phase of the maneuver. For simplicity, let's examine a single engine trainer type aircraft, and see where the crosswind impacts takeoff performance. At the start of the takeoff roll, with a crosswind, full deflection of aileron is made into the ...


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The equation refers to instantaneous thrust in unaccelerated flight. The weight in this equation is instantaneous weight. Indeed, this weight changes over time. This is for example the reason we have to use the Breguet range equation instead of just divide thrust by thrust specific fuel consumption to calculate the range of an aircraft.


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Vx increases with altitude while Vy decreases with altitude. When they coincide, you have reach the airplane’s absolute ceiling, which it can no longer climb and can only maintain altitude at that specific calibrated airspeed. Vx and Vy do exist above you maximum single engine ceiling, however, should an engine fail above the maximum single engine ceiling ...


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Having flown paramotors with around 15hp on tap, you may find that a max rate of climb in the tens of feet per minute might be ok on paper but it makes for an awful flying experience.


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In level flight the lift must equal the weight of the aircraft (which will typically reduce as it burns fuel). If lift exceeds weight then the aircraft will accelerate upwards; thus is something that we typically see at takeoff, and hopefully just before landing when the aircraft‘s rate of descent drops to almost zero. The maximum lift would be generated ...


3

With half the horsepower of the original, it will fly, but just barely, even allowing for a bit more thrust efficiency using a larger slower turning propeller. Your airplane may be 15 kg lighter, but the pilot's carcass is as much or more as a share of the total weight. So figure on maybe, at best, 55 percent of the original's available thrust with a better ...


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In a steep turn, at high speed. In addition to the lift needed to compensate weight, a turn requires the wing to produce additional lift to accelerate the aircraft sideways. Speed is required so enough dynamic pressure is available to produce all that lift. The same happens at the bottom of a tight loop when weight and the lift needed to compensate ...


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