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# Tag Info

2

For an ultralight with rudder only roll control, which achieves lateral control with a lot of dihedral to create a really strong roll/yaw couple, the issue would be how much reserve rudder authority is there once enough has been applied to counteract asymmetric thrust. That would determine how much roll rate you could still achieve trying to yaw toward the ...

0

Not a good thing about take-off at higher speed because the wear and tear of the tyres. Deployment of the flaps will change the camber of the wings, also this modify the local AOA. But the feeling effect for pilot is increase in lifting force and that happens at slower speed . When the lifting increases the same happens with the induced drag.

4

When turning on the Anti-Ice, the demand for bleed air increases and the EEC (Electronic Engine Control) will increase the target N1 to provide enough pressure by injecting more fuel. From the Boeing 737 NG FCOMv2 (7.20.5 Engines, APU - Engine System Description, emphasis mine): In the normal mode, the EEC uses sensed flight conditions and bleed air ...

3

Turning on Engine Anti-Ice causes the engine idle N1 to automatically increase so that it can supply additional bleed air and not flame out. This means that for descent planning, an earlier descent should be planned since idle N1 is now producing higher thrust.

0

It sure can; in fact, they are equivalent (with an offset of 1G). In the body frame, the vertical equation of motion is: $$Z+mg\cos\theta\cos\phi=m(\dot{w}+pv-qu)$$ Accelerometers can't measure inertial or gravitational forces, so vertical acceleration as measured is $N_z=Z/m$.

-1

The surprise of some engineers about comparing kinetic energy to lift?!?. Yes, let's look at the formulas, and how we apply them. In steady state flight, we talk about the 4 FORCES of flight. F = kg m/s^2 = ma: Lift, Gravity, Thrust, Drag So why not Kinetic Energy KE = kg m^2/s^2 = F × d, or even Power P = kg m^2/s^3 = F × d/t? Because, in describing ...

2

Wouldn't it be better to use no flaps, and rotate at the higher speed that is required? Well, now we are talking about a short field take off. If you ever watched Lindbergh's takeoff the day of the famous journey across the Atlantic non-stop flight, barely clearing a power line on climb out, or even actually done one off a muddy or snowy runway, you know ...

2

Because without flaps extended there is less safety margin for stalling in the landing. Picture above from this answer shows the lift coefficient as function of the angle of attack. With flaps extended, a certain amount of lift is reached at a lower AoA than without flaps. It is a safety feature during landing, when speed needs to be reduced as much as ...

3

Increasing the flaps does increase the drag, but not by that much initially. For the first stages of flaps you gain more by reducing required takeoff speed. If you would increase the flaps more and more, eventually the drag would become too much and you would lose takeoff distance again. Flap setting has an affect on the wing’s lift coefficient and on the ...

5

In the most simple model for subsonic aerodynamics, drag is split into two components: Zero-lift drag, that is all the drag created when the airplane produces no net lift. This kind of drag has again two components: Friction and pressure drag, that is the aerodynamic drag parallel and perpendicular to the local surface. This drag would dominate in a ...

0

No energy is 'lost' to lift. All the energy delivered by the engine is spent, directly or indirectly, in accelerating air downwards in order to produce lift...

0

I don't know if your question relates to the approach phase or the flare. The later as explained above has to do with the elevator, the former i.e for the approach phase you will notice that airliners and even more so fighter jets come on the approach indeed with a high noze up attitude. That has to do with swept wings. Swept wings allow an aircraft to fly ...

7

The change in pitch during the landing is called the flare and it is controlled by the pilot (or autopilot for an autoland) using the elevators (i.e. pulling on the yoke). From the Boeing 737 NG FCTM (6.10 Landing): When the threshold passes under the airplane nose and out of sight, shift the visual sighting point to the far end of the runway. Shifting ...

0

For landing an airplane has to slow down. When looking at the lift equation, $$L=\frac{1}{2}c_L(\alpha)\rho v^2A$$ We find that, to get constant lift $L$ with lower speed $v$ we need to increase either $c_L(\alpha)$ or wing surface area $A$ (we can't change the air density $\rho$). Note the explicit dependency of the lift coefficient on the angle of ...

0

Flaps help to increase the lift at low speed, allowing the aircraft to fly at a lower than cruise speed speed. The pitch up is caused by the elevator on the rear wing.

3

When flying at the airspeed that yields the maximum L/D ratio, which is also the airspeed that yields the lowest total drag force, 50% of the total drag is "induced drag", i.e. drag due to the creation of lift. At higher airspeeds, a lower % of the total drag is "induced drag". At lower airspeeds, a higher % of the total drag is "induced drag".

-3

About 6% You're looking for the "Lift to Drag" ratio - see here for some examples of different things: https://en.wikipedia.org/wiki/Lift-to-drag_ratio A paraglider is a 10:1 glide ratio. A 747 at cruise is 17:1 - thus - 6% of the power keeps it up, and the rest, 94%, offsets the drag of flying at mach 0.85.

1

Yes, those are speed brakes, used to slow the aircraft down. In this case, they also double as spoilers to kill lift once the aircraft has touched down. A propeller aircraft can be slowed down while in flight by throttling down and in some cases flattening the pitch on the prop blades... this created a lot of air resistance and slows the aircraft. When ...

0

The spoilers decrease the wing's lift coefficient. Yet in the context of flight, as opposed to the context of after touchdown, it's not really correct to imagine that they are forcing the wing to generate less lift. In a steady-state descent, lift is only slightly less than weight, unless we are talking about a really extreme dive angle. So what the "lift ...

6

As you can see on the photo, the flaps are slightly extended, allowing the aircraft to fly at a lower airspeed. This is common for aircraft to do during an approach, to keep a constant distant between incoming flights. An aircraft flying into an airport, can perform a continuous descent or a step down decent. Illustrated in the figure below: From the figure ...

12

Though your photos refer to a specific commercial airliner, your question is general, so I will describe a more specialized use case for speed brakes. A glider (also known as a sailplane) has no engine, and it is designed to have a very high glide ratio so that it can travel further between sources of lift. If a glider were to come in for a landing without ...

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 ...

2

Yes, deploying the speedbrakes makes for a steeper descent - can be seen quite often.

2

According to Airbus Airbus quote a single range figure of 6300km for the A320neo This is 100km more than Airbus claim for the A320ceo with sharklets but the difference is probably due to increased fuel capacity in the A320neo and possibly to revised wingtip arrangements. The difference in range between older A320 (~5700km?) and A320 with sharklets (~...

0

I would think this would not be practical for two reasons. The drag caused by the non-running engine coupled with the increased fuel demands of the remaining three would negate any fuel savings. I'm not sure of the the systems in the Olympus but most jet engines do not have any oil-pressure when windmilling and this can create problems. You may also have ...

4

Note that your plots show lift coefficient over angle of attack. This lift coefficient is referenced to a reference area which must be defined somehow. It is customary to use the projection of the clean wing area in the x-y plane for all flap settings in order to keep coefficients comparable. The lift curve slope increases because the real wing area ...

7

V1 is the speed at which you are committed to take-off, it doesn't mean you are off the ground. You can't retract the gear at V1 because you are still rolling on it heading down the runway. Vr is the speed at which you rotate the nose up to get into the air. Again you are still rolling down the runway with your nose in the air, you can't retract your wheels ...

3

This sort of scenario happens from time to time. Before a flight the crew will calculate the flap setting and speed at which the aircraft rotates based on aircraft weight, the weather conditions, and runway length. If any of these are entered incorrectly, the aircraft could rotate too soon and not lift off when expected. To decrease wear on the engines, ...

11

The first thing I would do is advance thrust to maximum available thrust, make sure both engines are indeed operating. Next I'd check is if the speedbrake is stowed. I would not consider retracting flaps because when you are too slow to climb you are definitely too slow to retract flaps... could be deadly. Normally this kind of situation can't happen ...

3

The FDR would show exactly what the control inputs were so they would know from that. It's important to understand that pitch trim effectively controls the airspeed the airplane will seek naturally without any control input (FAR 25 pitch stability requirements specifically require airplanes to effectively seek a trimmed speed within certain parameters ...

2

Transonic buffet, or Mach induced buffet, or high speed buffet, is a flow separation due to the combined presence of shockwave and "high" angle of attack. The boundary layer separation results in random high frequency vibrations. As the AOA increases, the separation and the associated vibrations worsen, up to the point where the crew can no longer read the ...

5

At gate aircraft is usually hooked up to an external power source to reduce emission. This can be in the form of ground power cable like your power socket at home or ground power unit. During taxi APU is not strictly needed as main engines would be already running and provide all the electricity or bleed air needed. Lugging around a HUGE external ...

5

As Ron points out in the comments the question is not so much where as it is when. Aircrafts see the density altitude of the air around it not the true altitude they are at. On a very hot day at a very high altitude airport the density altitude may very well be higher than the true altitude by a significant amount which affects takeoff performance. The FAA ...

3

There are several considerations for flying polar routes, but no special modifications are necessarily needed. Navigation is different, as Lat/Lon (specifically longitude) converge to become meaningless close to poles, so aircraft traditionally use a grid navigation system. Aircrew should also be aware of the difference between magnetic and true north, as ...

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