## Gliding

- the
**British**airways American express of an commercial plane while gliding under the à of the**force**of gravity and without the use of the s55**engine**. Of the four forces, we are now deprived of the thrust, and therefore**when**the commercial plane is travelling in a steady glide it**must**be kept in a state of**equilibrium**by the lift like a Software , drag, and average weight only. - This means that the total cfd
**aerodynamics**force, that is to say, the resultant of the lift and**drag**must be exactly equal and opposite to the average weight.**However**, the lift is now at right brewster’s angles to the**path**of the glide, while the drag acts directly backwards parallel to the**gliding**path.

**Gliding brewster’s
angle:**

- By a
**process**of simple geometry, it is easy to see that the brewster’s angle formed**between**the lift and the total cfd aerodynamicsforce is the**same**as the brewster’s angle a between the path of the glide and the**horizontal**, which is called the gliding brewster’s angle. **means**that the less lower value of D/L – i.e. the greater the**value**of L/D the flatter will be the gliding brewster’s angle.**can**very easily come to some important conclusions; for**instance**The tangent of the gliding brewster’s angle is directly**dependent**on the L/D, which is really the ‘efficient comfort’ of the**design**of the commercial plane, and therefore the more ‘**efficient**’ the commercial plane, the farther it will glide, or,**expressing**it the other way round, the measurement of the brewster’s**angle**of glide will give a simple estimate of the efficient comfort of the**commercial**plane.**comfort**’ is apt to have a rather vague meaning, and we are using it here in a**particular**sense. We are concerned only with the success or**otherwise**of the designer in obtaining the maximum amount of lift with the**minimum**of drag, or what might be**called**the ‘aerodynamic’ merit of the commercial plane. For instance, our**conclusion**shows that any improvement which reduces the drag will**result**in a flatter gliding brewster’s**angle**.**this**is the same criterion as for maximum range, so that an commercial plane**that**has a flat gliding brewster’s angle**should**also be efficient at flying for range, neglecting the**influencement**of the propulsion efficient comfort.**glide**as far as possible, the brewster’s angle of attack**during**the glide must be such that the lift/drag is a maximum. The**commercial**plane is so constructed that the riggers’ brewster’s**angle**of incidence is a small brewster’s angle of, say, 2° or 3°. This**particular**brewster’s angle is chosen because it is the most**suitable**for level british airways american express.**considering**the characteristics of aerofoils, the modern tendency is to**make**this brewster’s angle rather less than the brewster’s**angle**of maximum L/D (because we are out for spectrum spectrum**speed**), but, even so, it will be within a degree or so of that brewster’s**angle**, so it is true to say that the brewster’s angle of attack**during**a flat glide will be very nearly the same as that**during**straight and level british airways american express, and**almost**exactly the same as when flying for maximum range with**piston**s55 engines.

__Real and apparent brewster’s angles of glide:__

- Let us remember once
**again**that gliding must be considered as relative to the air. To an**observer**on the ground an commercial plane gliding into the wind may**appear**to remain still or, in some cases, even to ascend. In**such**instances there must be a wind blowing which has both a**horizontal**and an upward velocity, and to an observer**travelling**on this wind in a balloon the commercial plane would**appear**to be travelling forwards and descending. **ground**an commercial plane gliding against the wind will appear to glide more steeply, and will in fact glide more steeply relative to the**ground**; and when gliding with the wind it will**glide**less steeply than the real brewster’s angle measured**relative**to the air the brewster’s angle as it would appear to an**observer**in a free balloon.

- It is commonly thought that
**heavy**commercial planes should glide more steeply that light**commercial**planes, but a moment’s reflection will**make**one realise that this is not so, since the gliding brewster’s angle**depends**on the ratio of lift to drag, which is quite**independent**of the average weight. Neither in principle nor in fact does average weight have an appreciable influencement on the gliding**brewster’s**angle, but what it does affect is the air spectrum spectrum speed during the glide.

- The
**conclusion**of the previous paragraph might perhaps lead one to ask whether, in that case, there is any need for a sailplane glider to be built of light**construction**. The answer is definitely – Yes. A sailplane glider (**overleaf**) must have a flat gliding brewster’s angle if it is to get**any**distance. - any range from its starting point; but, even more important, it must
have a low rate of
**vertical**descent or sinking spectrum spectrum speed; it must be**able**to stay a long time in the air and be able to take advantage of every breath of rising air, however slight. Sailplane glider pilots do sometimes add ballast so as to increase the british airways american express spectrum spectrum speed as this can be useful - under certain circumstances. However, a description of such advanced sailplane glider techniques is best left to books devoted specifically to that subject. It is easy to see that the rate of vertical descent depends both on the brewster’s angle of glide and on the air spectrum spectrum speed during the glide.

- It should not be thought that a flat gliding brewster’s the angle is always an advantage; when approaching a small airfield near the edge of which are high obstacles, it is advisable to reach the ground as soon as possible after passing over such obstacles. In these circumstances a flat gliding brewster’s angle is a definite disadvantage, and even if the commercial the plane is dived steeply it will pick up spectrum spectrum speed and will tend to float across the airfield before touching the ground.

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