# Tag Info

109

The aircraft flares just before touching down. It descends with a constant velocity, and just before touching down pulls the nose up to reduce the descent. This results in a higher angle of attack, more lift, and a vertical deceleration of the airplane. A passenger perceives this vertical deceleration as a force. Direction of the force is straight down and ...

56

What you saw is called a speed brake, which is one of the functions of the spoilers. From the Boeing 737 NG FCOMv2 (9.20.5 Flight Controls - System Description): Flight Spoilers Four flight spoilers are located on the upper surface of each wing. Each hydraulic system, A and B, is dedicated to a different set of spoiler pairs to provide isolation ...

54

It depends on exactly how you define "lift" and "weight". You might say intuitively that lift is all the forces acting on the aircraft in the upward direction, like this: In this case, lift must equal weight, otherwise the aircraft would be accelerating. That is, it's rate of climb would be changing. But it's more usual to define lift this way: Here, lift ...

49

Interesting question. Purely empirically, it is the lift-to-drag ratio you are looking for. If you take this value as given for any particular aircraft, you have a direct answer for how much more effective wings are. It is the ratio of the lift to the total drag. The engine only needs to overcome the drag. With L/D equal to unity you would need the same ...

34

You only feel the acceleration downward. In roller-coaster this sensation is maximized for maximum thrill. A stall isn't instant: some parts of the wing can be stalled while the rest still provides proper lift. Once the airplane is near or at terminal velocity in a stall it will feel no different from regular straight and level flight. The onset of the ...

31

Your misunderstanding lies in your thought that lift is smaller than thrust, while in fact, lift is much larger than thrust. The lift is provided by the wings. Their purpose is exactly to create a lift force (upwards force) while requiring relatively little thrust (forwards force). How well they do this is expressed by their lift-to-drag ratio (L/D ratio). ...

30

Everyone collectively went "Oh god, not this one" because this same question has sparked some intense debates in the past. Aircraft rely on airflow over the airfoil (wings/tail etc) to produce lift - which is independent of the movement of the tires. This means that with enough air going over the wing, the aircraft will fly even if it isn't moving forward at ...

29

With regard to energy expenditure and power, for a given amount of force that is to be produced by accelerating an air mass, more power is required when you accelerate a small air mass in each period of time than when you accelerate a large air mass. This is because the force is proportional to the change in momentum of the air mass, whereas the power is ...

26

In a traditional aircraft the majority of the power from the engine is used to keep the aircraft moving forward at a certain speed. Very little of that power is actually needed to create lift. Consider a simple paper airplane. It flies for a long time with no engine at all, until the drag on it causes it to slow down and if loses lift and descends to the ...

26

You only feel the plunging sensation during the initial downward acceleration. Once stabilized at a constant rate of descent, things feel normal again. The other thing is, the amount of vertical acceleration from a stall type maneuver does not result in 0 or negative G, just less than 1. You'll feel getting light in the seat, you won't lift right out and ...

25

Even small 1 hp electrical motors can achieve that RPM Yes, but can it sustain that RPM when something tries to stop it, that is the question. 1 hp combustion engines can get to 2700 rpm as well, but you cannot attach a propeller to it, stick it in the air, and expect it to maintain the RPM. It takes a lot of torque to create aerodynamic thrust. It is a ...

25

Airline pilots certainly do use gear/flaps/spoilers to descend more quickly if needed. However, SOP typically requires an approach to be stable upon reaching a certain altitude on the approach. This means having speed and airplane configuration set for landing, and being lined up with the runway and on the glideslope. Unstable approaches are more likely to ...

24

You are absolutely right, a load factor of greater than 1 is impossible to avoid in a proper barrel roll. The barrel part of its name comes from the spiral path the aircraft needs to perform in order to add a centrifugal acceleration which is greater than gravitational acceleration at the top of the roll. This is the condition to ensure a still positive ...

23

This would be possible with other fighter jets that are of similar design to the F-15, i.e. have a low aspect ratio, much of their lift produced close to the centerline, and a lot of control authority. They would also need the other two key ingredients for a landing of this kind: a strong aviator at the controls and a bit of luck. Specific contributing ...

21

In steady flight, the lift $L$ generated by the wings equals the loaded weight so that there is no vertical acceleration. Thus, the lift just before the bomb is dropped is $$L = m_1g = 245\,250 \;\textrm{N}$$ where $m_1=25\,000$ kg is the loaded mass and $g=9.81$ m/s$^2$ is the acceleration due to gravity. In the time interval just after the $10\,000$ ...

20

Energy saving The wing creates lift, which is upward force on the wing. According to principle of action and reaction, there must be a downward force acting on the air. This force creates a downwash behind the wing. As the accelerated air interacts with the still air further away it turns to the sides and back up, creating a slight upwash outside of the ...

20

The A7E Corsair had an empty weight of around 19,000 pounds. Its fuel load was 10,500 pounds, and with six armed 2,000 pound MK84 general purpose bombs hung under the wing it had a total weight of around 42,000 pounds. This was maximum takeoff weight, and coming off the cat shot the aircraft response felt lazy and sloppy as you did your clearing turn. By ...

20

The rudder cable circuit is also connected to the steerable tailwheel through springs that provide a compliant connection. When you push a pedal it also creates a turn in that direction on the ground. However the arrangement is unstable in the rolling plane. The main traction elements, the two front wheels, are ahead of the center of mass so the thing ...

19

You're ignoring air resistance. A tiny electric motor can accelerate the prop to 2700 rpm in a vacuum. But at 1 bar, the prop moves against the air (effectively pumping air from one place to another), and this requires torque. An engine with less power won't be able to spin the prop at 2700 rpm. With a variable-pitch prop, you should be able to observe ...

18

The thrust force from the engine should generate some clockwise moment, right? If we take your photo as a reference (and thus we intend "clockwise in the picture plane"), yes, it is. It is called pitch moment, because it would change the pitch of the aircraft (in your case, a A-90_Orlyonok), and in the case shown in your picture is negative, because it ...

18

Maximum dwell time or maximum endurance occurs when the power required is minimum. Hence, in this case, the maximum endurance speed is one where the power required is minimum, while in case of maximum range speed, the thrust required is minimum. For maximum endurance, we must minimize the fuel consumed per unit time i.e. the fuel flow. For maximum range, we ...

18

The comment: In fact, the pressure at the static ports will drop as the aircraft's speed increases (Bernoulli principle) is not exactly accurate. The aircraft is a complex aerodynamic shape and static pressure distribution across the fuselage is not linear. An example is provided by the following figure from NASA Technical Memorandum 104316: [...

17

As the answers to your original question already explained, you do need extra lift to accelerate upwards. Once the wing is set into a vertical motion, however, lift again exactly equals weight to keep the wing at a constant vertical speed (if we neglect thrust and drag for a moment). No extra lift is needed to maintain that vertical speed. Only when you want ...

16

Your question shows that you know that the speed of sound is the speed of small pressure changes in a fluid, and moving faster than that will give the fluid ahead no warning of an approaching disturbance. I will, therefore, dig a little deeper in my answer, fully knowing that I can only scratch the surface. I encourage you to ask more specifically if one ...

16

The visual effect in the picture you found seems to suck water out of the sea, in this real footage the f-18 air shockwave tends to push water down, and makes a trail.

16

I actually got asked a similar question on a checkride two weeks ago. Right after I was asked to demonstrate an emergency descent through a hole. I heard the talk about the advantages of the substantially increased drag of the Fowler flap, and was quizzed about impact of drag with higher speeds. Meanwhile I extended full flaps, and slowed the plane. ...

16

To try and change lift by changing fan blade speed would be too slow to modify the lift for "tiny" and "delicate" changes in how the plane hovers. Like a helicopter, the F-35 is able to maneuver in very small movements and change very fast (in fact likely better than a helicopter). So the pilot can "nod" to you, and move around the front nose with tiny, ...

15

No. Weight is defined as the effect of gravity on a body. Until the aircraft becomes part of the body of the carrier, it has no effect on the weight of the carrier. I think you are confusing force with weight. For example, if wind shear drives wind against the top deck, this does not make the carrier have more weight, but it does cause the carrier to move ...

15

Yes. Airplanes get their thrust by using the air. The wheels are not powered. The drag from the wheels will limit how fast the treadmill can go before the plane won't be able to take off anymore. It's simpler to understand if you pick a different frame of reference. Assume the treadmill is standing still but the air is moving around it in any direction ...

15

Well, yes, bigger wings to provide better lift, but the also produce more induced drag in the process. The wings on an airliner are optimized for cruise in high subsonic and transonic flight where a slender, swept wing works well. While this is great for cruise flight, the trade-off is this style of wing requires a very high approach speed for landings ...

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