Slots Slats Flaps

Flap and slat positions are indicated by two pointers in the flap position indicator. There are L and R pointers for the left and right wing flaps and slats. The right pointer is normally hidden from view by the left pointer. In the flaps 1 position, the flaps and slats move. Flaps 1, 5, 15, 20 are takeoff flap positions. Airfoil camber, flaps, slots, slats & drag. The first double-slotted direct replacement for the stock PA-18 flap, Performance STOL flaps represent a broad jump forward in the short takeoff and landing performance of certified Piper Super Cubs. The STC'd flaps come in a two-hanger configuration with the flaps extended inboard to the fuselage. When speed is below V FE, =, flaps 1 can be selected. Slats deploy first. Note that flaps 1+F cannot be selected from flaps 0 in the air. When flaps 2 is selected, both the slats and flaps are deployed. Alpha/speed lock function Inhibits slats retraction at high angle of attack and/or low speed when the flap lever is moved from 1 to 0.

Krueger flaps, or Krüger flaps, are lift enhancement devices that may be fitted to the leading edge of an aircraft wing. Unlike slats or droop flaps, the main wing upper surface and its nose is not changed. Instead, a portion of the lower wing is rotated out in front of the main wing leading edge. Current Boeing aircraft, and many others, use this design between the fuselage and closest engine, where the wing is thickest. Outboard of the engine, slat flaps are used on the leading edge. The Boeing 727 also used a mix of inboard Krueger flaps and outboard slats, although it had no engine between them. Most early jet airliners, such as the Boeing 707 and Boeing 747, used Krueger flaps only.

Operation[edit]

While the aerodynamic effect of Krueger flaps may be similar to that of slats or slots (in those cases where there is a gap or slot between the flap trailing edge and wing leading edge), they are deployed differently. Krueger flaps, hinged at their foremost position that once deployed actually become their trailing edges, hinge forwards from the under surface of the wing, increasing the wing camber and maximum coefficient of lift.^[1] It produces a nose-up pitching moment. Conversely, slats extend forwards from the upper surface of the leading edge. Also, when deployed, Krueger flaps result in a much more pronounced blunt leading edge on the wing, helping to achieve better low-speed handling. This allows smaller-radius wing leading edges, better optimized for cruise. Leading edge Krueger flaps enhance wing's low speed lift production especially on swept wing aircraft. ^[2]

The Krueger flaps developed for the Boeing 747 were constructed from fiberglass honeycomb material and were designed to be intentionally distorted into an aerofoil section on deployment.^[3]

History[edit]

Krüger flaps were invented by Werner Krüger in 1943 and evaluated in the wind tunnels in Göttingen, Germany.^[4] One of the earliest civil applications was the Boeing 707 whereas swiss FFA claimed the first use of the flap in its FFA P-16 fighter which flew in 1955.^[5] The flap was added to prevent wing stall with an extreme attitude take-off with the tail dragging on the runway, a scenario that had caused two de Havilland Comet accidents. A preliminary flight test had been made on the Boeing 367-80 using a fixed flap and a skid on the after-body.^[6] After the Boeing test flight on the B-707 prototype on 15 July 1954, Krueger flaps were first used in production for the B-727 which made its maiden flight on 9 February 1963.^[7]

• Krueger flap operation

• Slat operation

Boeing commenced a series of test flights on 17 March 2015 with a modified Boeing 757, incorporating new wing-leading-edge sections and an actively blown vertical tail.^[8] The left wing has been modified to include a 6.7 m-span glove section supporting a variable-camber Krueger flap which will be deployed during landing and which protrudes just ahead of the leading edge. Although Krueger flaps have been tried before as insect-mitigation screens, previous designs caused additional drag. The newer design being tested is variable-camber and designed to retract as seamlessly as possible into the lower wing surface. Increasing the use of natural laminar flow (NLF) on an aircraft wing has the potential to reduce fuel burn by as much as 15%, but even small contaminants from insect remains will trip the flow from laminar to turbulent, destroying the performance benefit. The test flights have been supported by the European airline group TUI AG and conducted jointly with NASA as part of the agency’s Environmentally Responsible Aviation (ERA) program.

See also[edit]

References[edit]

Notes[edit]

1. ^Gary V. Bristow (2002). Ace the Technical Pilot Interview. McGraw-Hill Professional. ISBN0-07-139609-8. Retrieved 2009-02-16.
2. ^Wyatt, David (21 August 2014). Aircraft Flight Instruments and Guidance Systems: Principles, Operations and ...books.google.com. ISBN9781317938316. Retrieved 16 July 2020.
3. ^Taylor 1990, p. 114.
4. ^Niels Klußmann; Arnim Malik (2012). Lexikon Der Luftfahrt. Springer. pp. 193–. ISBN978-3-642-22500-0.
5. ^X-Planes of Europe II, Tony Buttler Hikoki Puplication 2015. Page 193. ISBN978-1-9021-0948-0
6. ^'The Road to the 707' Cook, William H., TYC Publishing Company, Bellevue, 1991, ISBN0-9629605-0-0, p.249
7. ^Hitchens, Frank (25 November 2015). The Encyclopedia of Aerodynamics. books.google.com. ISBN9781785383250. Retrieved 16 July 2020.
8. ^'757 EcoDemo Focuses On Laminar And Active Flow'. Aviation Week. 23 March 2015. Retrieved 23 March 2015.

Bibliography[edit]

• Taylor, John W.R. The Lore of Flight, London: Universal Books Ltd., 1990. ISBN0-9509620-1-5.

Welcome to part four in of a five-part series on airframe structures. In the previous tutorial we discussed the wing structure, now we will focus exclusively on the aerodynamics and structural design of the high lift flap and slat system.

Introduction

Almost all modern aircraft make use of a high-lift system to provide additional lifting capacity at slow speeds. This system takes the form of trailing edge flaps, leading-edge slats, or a combination of both. Slats are rarely used on light aircraft, except for some STOL models that are built with fixed leading-edge slats to improve take-off and landing performance. Flap systems range from simple plain flaps to very complicated multi-element fowler type configurations. This tutorial will provide an overview of the different high-lift systems in use today and discuss the various trade-offs between performance and simplicity.

Slots Slats Flaps For Dodge Ram

Why a high-lift system?

Aircraft typically operate across a wide range of speeds. A wing is generally designed to be most efficient during cruise, which for most general aviation or commuter types is the aircraft’s primary mission. Wings designed for a cruise condition are not necessarily well suited to low-speed flight, and so taking-off and landing would be considerably more difficult (read dangerous) if the wing could not be modified through a flap system to increase the lifting capability of the wing at low speeds.

How do flaps and slats work?

Flaps and slats work by increasing the camber of the wing through the mechanical actuation of leading-edge devices (slats) and trailing edge devices (flaps). Flaps generally span the inboard half of the wing and make up the last 25% – 30% of the wing chord. They are mechanically actuated and controlled by the pilot in the cockpit. The pilot can deploy the flaps to a number of predetermined angles below a certain speed; and does so before landing and often for a take-off as well.

Camber is the measure of the curvature of the wing aerofoil profile. Aerofoils that are more highly cambered produce more lift at a given angle of attack. A deployed flap or slat works the same way and increases the camber of the wing, which produces more lift at a given angle of attack, or the same lift at a lower angle of attack.

Increasing the lifting capability of the wing through the deployment of flaps increases the maximum lift coefficient of the wing. The lifting equation can be rearranged to solve for velocity, and the stall speed determined if the maximum lift coefficient is substituted into the equation. Increasing the maximum lift-coefficient by extending flaps reduces the stall speed of the aircraft, which is ideal during take-off and landing.

A typical graph of lift-coefficient against angle of attack for a light aircraft at three flap settings is shown below. The effect of adding flap during an approach and landing can be demonstrated by referring to the graph.

Each flap setting results in the aircraft operating on a different lift curve. Larger flap angles result in an increase in lift produced for a given angle of attack. This means that during the approach to land, adding flaps not only reduces the stall speed, but also reduces the angle of attack needed to maintain a given lift value. This results in a lower pitch attitude (more nose down) during the approach which gives the pilot better visibility during this critical phase of the flight.

Adding flaps not only increases the lift produced but also the drag. This is an important consideration which must be well understood when learning to fly. Increased drag can be useful when trying to slow the aircraft down to the approach speed but can present a problem when trying to climb away, for example during a go-around. You should always refer to your pilots operating handbook for the particular aircraft you are flying, and use the manufacturer recommended flap settings for take-off and landing. Large flap deployment angles also make the aircraft more susceptible to gusts. On windy days it is common in a light aircraft to fly the approach and landing at a reduced flap angle to improve control authority in these conditions.

Types of Trailing Edge Flaps

There are many variations of trailing edge flap in use on modern aircraft today. Plain or simple flaps merely deflect the trailing edge region downward to increase camber. More complicated multi-element designs make use of slots between flap sections to reenergise the airflow over the flap, delaying separation and increasing the lifting capability of the wing.

Slots Slats Flaps For Jeep

Plain Flap

Plain flaps deflect downward to increase the camber and therefore lift produced by the wing.

Split Flap

Split flaps are rarely used today, but only the lower surface of the trailing edge is deflected downward when operated.

Slotted Flap

Slotted flaps are designed to extend downward in such a way so as to create a slot between the trailing edge of the parent aerofoil and the flap. This slot is carefully designed to allow higher pressure air from the lower surface to move through the slot, and to reenergise the airflow over the upper flap surface. This allows higher pressure air to flow over the upper flap surface, reducing the tendency for the air to separate. Slotted flaps provide greater lifting capability at steeper flap angles, reducing the stall speed of the aircraft further.

Flap systems can be designed to be single-slotted, double-slotted, or even triple-slotted. The more slots employed, the more complicated and expensive the design is to manufacture and maintain.

Fowler Flap

Referring to the lift formula, more lift can be produced either by increasing the lift coefficient (introducing camber through flaps), or by increasing the area of the wing. Fowler flaps do both; extending backwards and downwards to increase camber and wing area. Fowler flaps are the most effective flap systems in operation today but are more complicated to design, and heavier to implement. Fowler flaps can be combined with multiple slots to produce a slotted-fowler flap.

Leading Edge Slats

The principle of operation of a leading-edge slat is similar to a trailing edge flap. The camber of the aerofoil is increased by drooping the leading edge downward, and a slot or gap between the slat and the parent aerofoil allows the passage of air from the lower surface to the upper surface.

Slats are most often seen on larger jet airliners, but fixed slats have also found use on some STOL light aircraft where high lift is deemed more important that cruise performance. The permanence of a fixed slat creates additional drag at cruise when the additional lift generated by the slat is not required.

Properties of a High-lift System

We’ll close this post off with a short discussion of some important properties of a typical high-lift system, and how this should direct the way in which you use flaps in your light aircraft.

Design Trade-offs

It is important that a flap system is not only considered in terms of the additional lift being produced but also the additional drag that extending the flaps produces. Flap drag has two components: (1) the additional drag generated by the protrusion of the flap into the freestream, and (2) the additional lift-induced drag that is formed by trailing edge vortices shed off the edges of the flap.

The ratio of lift-to-drag is termed aerodynamic efficiency and is a measure of how much lift is produced relative to drag. The higher the ratio of lift-to-drag, the more efficient the aircraft and the lower the total drag signature. Extending flaps always reduces the aerodynamic efficiency of the aircraft. This means that the increase in lift that is produced is less than the additional drag that results. This is particularly important when discussing the use of flaps during a take-off where the aircraft is flying slowly, and any additional drag makes it difficult to climb out.

The example below shows the change in lift produced with angle of attack for three different flap settings (LHS) and the resulting aerodynamic efficiency of those flap settings (RHS). For all three flap settings, the additional lift generated by the increased flap angles reduce the overall aerodynamic efficiency of the aircraft.

Take-off Flap Settings

Slots Slats Flaps For Ezgo

The flap setting used for take-off is very important as it will determine how the aircraft operates on the ground roll and the initial airborne segment.

A take-off is defined as the horizontal distance covered from a stationary position on the runway to the point when the aircraft is airborne at a particular height above the ground (35 ft or 50 ft depending on the airworthiness regulations used). A take-off is therefore split into a ground roll and an airborne segment. Increasing the flap deflection angle used for take-off has the following effects on the two segments.

• Increasing the flap deflection angle reduces the stall speed which means that the aircraft can get airborne quicker, reducing the overall ground roll.
• The increased drag associated with the larger flap deflection angle reduces the aerodynamic efficiency, increasing the drag and making it more difficult to accelerate and climb out. This has the effect of increasing the airborne segment of the take-off.

It is very possible that an increased flap setting will therefore increase the total take-off distance. This could be a real problem if trying to get airborne from a short runway and clear a treeline at the end. It is important to always consult the pilot operating handbook and follow the advice given by the manufacturer with regards to selecting the most appropriate flap setting for a particular situation.

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Did you enjoy this post? Why not keep reading through this series on airframe structure and control surfaces.