Hot answers tagged

38

Why no flaps? Flaps change the pitching moment of a wing. After all, they add lift over the full chord, so the sum of the increased lift attacks at about mid-chord, which is a quarter chord aft of the regular lift. If there is no separate tail surface to compensate for the pitching moment caused by that extra lift, the aircraft will quickly pitch nose-down ...


19

For the Boeing 727-100 and 747-100/200 the answers are: when does the system know when to sound the alarm? When the thrust levers are advanced to begin the takeoff, if flaps and slats and a few other things are not in takeoff position, a loud horn sounds. figure out at what speed they can take off without flaps and slats. Takeoff is not permitted ...


13

The item 1 is a Krüger flap, a leading edge device which allows the wing to operate to a higher angle of attack. The wing-root fairing makes a small triangular segment necessary; outboard of it slats are used. The item 2 is a NACA inlet for cabin air, as commented by @mins.


11

A flap increases airfoil camber, and can be on the leading edge or trailing edge. The Krueger Flap is a Leading Edge Flap, the actual generic term. The Krueger dude developed the LE flap used on some airliners so his name is attached. A slot increases stalling AOA, without necessarily increasing camber, as in the fixed slots used on a lot of light ...


11

It's because leading edge devices allow a higher Angle of Attack. The four types of leading edge devices work by pointing the nose of the wing downwards so that at higher AoA there is no flow separation at the upper surface near the nose. Deflecting the slats does not increase $C_L$, the aeroplane must increase AoA to do that. Lower stall speed comes with ...


10

This is from memory and applies to 747-100/200 aircraft, which I last flew in 1999. The video shows, I think, a -400. However, to the best of my knowledge, it has the same flap settings. The flap selection handle detents and resulting device positions are: 0° — leading and trailing edge retracted 1° — leading edge inboard of the engines ...


8

On most aircraft I have flown, the Takeoff Config warning sounds when the thrust levers are advanced for takeoff power.


7

The Piper Aztec has standard (plain) flaps: Source: Sky4Buy.com Another View: Source: Same as above The Aztec does not have slats as can be seen in the image from the front of the wing: Source: NWAviators.com Here is a close-up view of the wing of the plane in the first two images (damaged, but no slats): Source: Sky4Buy.com Other than the flaps (and ...


6

For a leading edge high-lift device to be called a slat, it has to have a slot behind it. Otherwise, it is a leading edge flap (or, if it's of a specific design, a Krueger flap). Because: By definition, the word slat means a thin, narrow strip. Its etymological roots lay in Middle English word slate, first recorded use in the aforementioned meaning dates ...


6

What usually happens is the crew doing the walkaround spots something that looks like damage, calls airline maintenance, and techs come look at it. For a ding, they will consult the Structural Repair Manual guidance on allowable limits on dents. Based on the SRM it may be ok to leave as is, or require repair, or require further evaluation. If the SRM ...


5

If the slats would increase L/D, they would not be retracted in cruise. TomMcW is right, any high lift device increases drag when compared to a polar point that is within the regular operating envelope of the clean wing. How much so can be answered when looking at old wind tunnel data published by Sighardt Hörner in his classic "Fluid Dynamic Drag": Figure ...


5

There are different types of Krueger flaps used, with increased efficiency coming at the cost of increased complexity. The simple ones are basically flat panels that folds out from the wing lower surface into a very steep, deployed position and seals against the wing leading edge; though these are extremely simple, they don't offer much in the way of stall ...


5

Slats increase the camber of the wing, which increases the coefficient of lift. When you deploy slats, the AOA is actually lowered for that part of the wing. This is the same washout principle Dunne ingeniously applied to the D.8 swept wing bi-plane in 1912! You now have a more heavily cambered wing at a lower angle of attack, so more lift is to be had ...


5

A slat is a retractable version of a device known as “leading edge slot”. It is basically a slot just behind the leading edge. When an airplane is flying slow, it will probably either be somewhat nose-up to maintain level flight, or be descending, or somewhere in between. In either case, the air strikes the wing at a higher angle than when the plane is ...


5

A "sealed" slat has no slot between it and the main wing. According to b737.org.uk, sealing flaps allows for more lift at a lower AOA (Angle of Attack). Reference from Flightglobal.com "Short Field 737 goes into flight test" states that sealing of up to 25 degrees of slats will be available for take-off, an improvement from 1 and 5 degrees. Slots (not ...


4

The two main leading edge devices are leading edge slots and leading edge flaps: Slots energize the boundary layer to delay stall by allowing higher pressure air from below to "leak" in a controlled way to the upper surface. The slot is effectively a convergent duct, large at the bottom and small at the top, so the air is slightly accelerated as it flows ...


4

The number below the flap indication is not the position of the flaps/slats, but the position of the flap lever. When the lever is moved, the number becomes cyan indicating that the flaps/slats are in transit and when they have reached the selected position the number becomes green. Edit: As per FCOM, there is no mention of amber XX indication for flap ...


4

Because with a delta wing the trailing edge has the elevators and it's too far aft to have a flap. They depend on wing area and the ability to operate at much higher AOAs than straight wings to get the speeds down. As for slats, they don't increase Clmax all that much, only a little bit from the increase in chord in drooping the leading edge. The main ...


4

Many large airliners, particularly Boeings, use Krueger flaps closer in to the fuselage and slats further out on the wing. This is primarily because slats resist a stall more effectively, so by placing Krueger flaps on the forward parts on a swept wing and slats on the rearward sections, it encourages a more balanced, controlled landing stall. Another reason ...


3

1) Appears to be where the inboard leading edge slats retract into. 2) Ram air inlet for the air conditioning/equipment cooling.


3

To answer your question, I suggest to look at the effect of slats. NACA technical report 407 studied a fixed slat similar to what is used on the Zenith CH-750, and the result of the optimum geometry is plotted below. Dashed lines are for the airfoil with a fixed slat and solid lines for the airfoil with the slot between slat and wing filled: Lift and drag ...


3

The theoretical maximum lift of a cylinder is 4π. At that point the forward and rear stagnation points coalesce on the bottom of the cylinder. Practical solutions use rotating cylinders (Flettner rotor) but will not reach this theoretical limit. This should illustrate that 6.5 is not outright impossible but the distance between a cylinder and an airfoil is ...


2

Prior to the NG, the total number of slats is 6, that is 3 slats per wing Thus there are 6 slats numbered from 1 to 6, that is slats 1 and 6 are the outer slat The NG's have an extra outboard slat on each wing giving 8 in total. They have the same sequencing as the classic Thus a 3 slats per wing refers to 737 prior to the NG more precisely Leading edge ...


2

It depends. Are the c$_l$ values referenced to the local chord? Then you need to convert them to the chord of the full airfoil so they can be added. I wonder, however, how you can have individual lift coefficients without the total lift coefficient. If the single parts are isolated, their pressure distribution is different from that in the context of the ...


2

Flaps, Krueger flaps, and slats are all ways of modifying the wing's airfoil to effectively increase its camber. Stalling happens when the air-flow separates. That is, rather than continuing to flow along the surface of the wing, it starts to simply flow away from the wing. It typically happens at high angles of attack. When the wing's camber is increased, ...


2

The Dash8 - Q400 - Aeroplane General PDF (courtesy of smartcockpit.com) indicates on page 27 that there are inboard and outboard flaps. Reading through the Dash8 - Q400 Flight Controls PDF (also from smartcockpit.com) indicates that: Two single-slotted inboard and outboard fowler flaps are attached to the trailling edge of each wing (Figure 12.8-1).page ...


2

The leading-edge slat was independently invented by Gustav Lachmann and Handley Page just after WWI. (Lachmann presently came to the UK to work for Handley Page.) It diverts airflow downwards over the wing, allowing the wing to operate at a higher angle of attack and hence at lower airspeeds, without stalling. It is most needed near the wing tips and, as it ...


1

Putting slats and flaps on a 10 cm model is extreme, but would add a touch of realism for the serious hobbyist. At which point in scale do slats and flaps become unnecessary? We turn to the lift equation: $Lift$ = Air density x Area x Lift Coefficient x Velocity$^2$ $Weight$= $Lift$ for steady state flight so we derive: $Weight/Area$ = Rho x Lift ...


1

Slats and slots are two different concepts. Slats are on the front of the wing, flaps on the back. Both serve to change the camber, or curve of the wing, increase wing area, and change the angle of attack (angle of the aerodynamic chord of the wing, to the relative wind. They affect upwash, or the airflow ahead of the wing, and downwash, airflow behind ...


1

What slats do is increase the camber of the wing, which enables it to generate more lift at a lower airspeed. They perfectly compliment flaps to transform a finicky "supercritical" wing (designed for optimal transonic performance) into a lower speed lift producing machine. Camber has to be minimized at transonic speeds to avoid drag producing shock waves ...


Only top voted, non community-wiki answers of a minimum length are eligible