New answers tagged

-1

First a caveat-- please keep in mind that this answer is focussed on steady-state linear gliding flight. Throughout this answer, when we talk about what happens when we change the angle-of-attack and L/D ratio, we're assuming that we've waited long enough for the glider to settle back into equilibrium at whatever airspeed is appropriate for the new angle-of-...


-1

The general "textbook" formula to show calculate the max range speed (at least the one I was taught), goes more or less as follows: For a piston engine, fuel consumption is roughly proportional to engine power: [1] fuel_consumption_per_hour = constant * power Hence fuel_consumption_per_mile = constant * power / ground_speed Assuming no wind, gs = ...


3

Let's start with a Lift/Drag/Weight diagram, and draw the velocity vector as well: Since no thrust is involved, Lift+Weight+Drag must sum to zero. Let's shift the origin of these vectors around a bit: Now, let's finish the velocity triangle, drawing a (horizontal distance), and b (vertical distance). The ratio between a and b is by definition the glide ...


-1

Here is another vector diagram, accounting for greater speed and rate of descent, holding weight constant, and assuming a higher stick pull will give a slower airspeed, lower rate of descent, and a greater angle of descent to the horizon in a glide: As we can see from the lift equation, the slower glider at V min sink must have a higher coefficient of lift ...


-1

First a caveat-- please keep in mind that this answer is focussed on steady-state linear gliding flight. Throughout this answer, when we talk about what happens when we change the angle-of-attack and L/D ratio, we're assuming that we've waited long enough for the glider to settle back into equilibrium at whatever airspeed is appropriate for the new angle-of-...


2

Best L/D is a purely airframe concept, whereas best range is a wholistic system concept. (This answer builds on @LDMax's answer) Analysis Airframe's best L/D This is the exact point on the glider polar where any faster or slower results in a shorter glide range (in still air). However, sometimes that peak is very shallow, that is to say that accelerating or ...


0

The fact that less lift is required in gliding flight than in level flight is a bit of red herring. The difference is tiny and can be accommodated by flying at the same angle-of-attack and L/D ratio and Cl/Cd ratio but at a (indistinguishably?) slower airspeed. For all practical purposes, for reasonably efficient airframes, this effect is so tiny that any ...


-2

we are not at the same L/D max AOA at Vmaxxrange that we are at Vbg That is correct. You are going faster, there for less wing AOA is needed to equal your planes weight in lift. So many people attribute the higher Vmaxxrange to greater engine/prop efficiencies, and it may well be that the A36 Bonanza burns the least amount of fuel per mile at 125 KIAS, but ...


6

I'm going to answer with the caveat that I don't have as deep of an understanding of this as I would like, and someone smarter than me may be able to correct or expound on my response. Best Glide is a purely aerodynamic concept. There is no powerplant involved, so you're simply converting potential energy (altitude) into forward motion, at a rate and L/D ...


-1

how can power be increased without increasing speed... but in the real world, energy is used or lost in many places... You answered your own question. Drag is what limits speed for a given power setting. Excluding adding drag by dropping flaps for now... The drag of an airplane is dependent not only on its speed, but also on its angle of attack, and on ...


3

Now, how can be power increased, without increasing speed? Think of the airplane for a moment as a black box. It moves through air, creating a drag force. This drag force needs to be overcome by supplying a thrust force which works in opposite direction. Basic physics, equilibrium of forces, no integrals required. Moving an object against a resistive force ...


2

Regarding the question about raising altitude and increasing power, airplanes are no different from cars or people: To transfer from level movement to one that has a vertical component, you are going to need more power to maintain the same speed. The need to increase power in all of the aforementioned cases comes from increasing the potential energy as we (...


2

Start by studying gliders -- note that while they cannot maintain a climb in the absence of updrafts, they can certainly be flown at a wide range of airspeeds, with no influence from a motor at all. An airplane is nothing more than a glider with power added. Fundamentally, the power setting governs the climb or descent rate for a given airspeed, but doesn't ...


0

In level flight if you increase power, speed will indeed rise. If you are talking about rising the RPM with a constant speed propeller, the speed will only slightly change (because the engine may produce a different power output at a different RPM). Changing RPM in a constant speed propeller does not produce great changes of power. It's just like selecting a ...


2

To fully understand the answer you are striving to get, you have to understand the four fundamental forces of flight. These are best explained in the Pilots Handbook of Aeronautical Knowledge. It will explain more about the forces interaction. The ones you are most concerned with are thrust and drag. Thrust is a function of the engine-prop combination, not ...


8

The problem is your assumption of speed = rpm * coef This is only true as long as there is a rigid connection between the RPM and the medium against which the speed is measured. Let us consider a car for a moment. In a fixed gear, there is a fixed relationship between the engine RPM and the RPM at which the tires rotate. As long as the tires are not ...


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