40 votes
Accepted

Why didn't the Concorde have flaps or slats?

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 ...
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13 votes
Accepted

How does the use of Leading Edge Root Extension help in increasing stall angle?

The idea is to generate a vortex near the fuselage. In most cases we do not want any vortexes, as the unnecessary air movement always causes an increase in drag. In this case however, you need them. ...
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13 votes
Accepted

Under what circumstances does the F-16 and possibly similar fighters deploy leading edge slats?

Technically, F-16 and "similar fighters" have leading edge flaps (LEF) (or droop flaps), rather than slats. The difference is that they don't form a gap between themselves and the main ...
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  • 8,605
11 votes
Accepted

How do droops help to avoid stalls?

Similar to a leading edge flap, fixed in the extended position with no gaps: The nose is lowered, so at high angles of attack the flow still has its stagnation point at the round nose where on an un-...
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11 votes

What is the purpose of extending one degree of flaps (perhaps with spoilers)?

Normally, one degree of flaps in fact only translates to an extension of the leading edge devices (e.g. slats), trailing edge flaps remain fully retracted. On some aircraft this configuration can be ...
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  • 74.8k
10 votes
Accepted

Would a slotted "wing" work?

This might be a bit late but the short answer is, again, no. Check NACA report 427 and Experimental investigation of a Handley Page 44f wing. Slots at locations other than the vicinity of the leading ...
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9 votes

How does the use of Leading Edge Root Extension help in increasing stall angle?

@DamalaniSingh: I wonder why you see the need for a bounty when web pages such as this give a good explanation already. In order to avoid a link-only answer, I will summarize the LEX-related gist here ...
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8 votes

Would a slotted "wing" work?

No, it will not work in the way you plotted it. First, the corners of the duct should be nicely rounded. With the sharp corners you will get a lot of vorticity, but little lift increase. Actually, ...
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8 votes

Under what circumstances does the F-16 and possibly similar fighters deploy leading edge slats?

According to a F16 forum.. Those are the LEF's (leading edge flaps). They are there to produce extra lift to the wings during high AOA and low airspeeds. The reason they are up on the ground is they ...
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  • 343
7 votes

Would a slotted "wing" work?

It works but your description is not so clear about the real size of the gap. Gliders sometimes have little holes along the wing on the upper side where air from beneath is provided to them by a ...
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  • 199
7 votes
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Why aren't leading edge root extensions used on airliners?

Leading edge extensions like slats are used in airliners. Most of these are controlled ones, so as to improve low speed characteristics. By Adrian Pingstone (Arpingstone) - Own work, Public Domain, ...
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  • 98.5k
7 votes
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How do blow holes compare to other means of tripping the boundary layer?

In modern gliders, active tripping of the laminar boundary layer helps to reduce or avoid a laminar separation bubble. There are three ways of doing this: Noppenband (dimple tape): Close-up picture ...
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6 votes
Accepted

What is that protruding fuselage part?

The strakes function as giant vortex generators. They generate vortices at high AOAs to improve airflow over the rudder at low speeds. During the Q400 test program it was found that there was some ...
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  • 104k
6 votes

Do leading edge flaps increase the critical angle of attack?

Yes leading edge devices indeed postpone stall to a higher Angle of Attack. They are particularly useful for: Airfoils which are prone to leading edge stall. Deflection of the trailing edge flap ...
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  • 57.8k
5 votes
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Why don’t aircraft have interlocks to prevent high-lift devices from being retracted when doing so would stall the airplane?

Most modern airliners have some form or other of mechanism that does exactly that, mostly for the slats (which are more important in stall prevention, anyway). E.g. on modern Airbusses, there is a ...
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  • 4,522
5 votes

Would the Concorde have been better off using a tailed delta wing?

The beauty of the pure delta configuration was you could get a reasonably low supersonic drag configuration in a planform with a lot of wing area, essential for really high altitude cruise and for ...
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  • 104k
5 votes

Why do Leading Edge Flaps (LEFs) create lift while down at slow speeds, but decrease lift while down at higher speeds?

Leading edge flaps, also known as slats, don't really create lift. The effect on lift coefficient is minor (less than 10% in general) but they help increase the stall angle of attack. As a summary, ...
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  • 1,787
5 votes

Why have high lift devices on both leading and trailing edge?

Slats increase the stall angle, flaps do not, that is the key issue - safety margin. Plus on aeroplanes with high wing loading even triple slotted fowler flaps may not cut the mustard, slats are ...
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  • 57.8k
5 votes

Why have high lift devices on both leading and trailing edge?

Slats are a necessity when the wing uses slotted flaps or Fowler flaps for maximum lift. Those flaps cannot reach over the whole span of the wing to leave room near the wingtips for ailerons. Once the ...
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4 votes
Accepted

When should I use the global Reynolds number and when the local Reynolds number?

Definitely use the local Reynolds number on each of the flaps! The flap will only work properly if it is allowed to produce its own, fresh boundary layer. If instead it inherits the slow, thick ...
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4 votes

Why didn't the Concorde have flaps or slats?

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 ...
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  • 104k
4 votes

Why do Leading Edge Flaps (LEFs) create lift while down at slow speeds, but decrease lift while down at higher speeds?

This site has some info on what the F-16 leading & trailing edges do during the flight - symetrically. We can see that at high speeds the wing is straight: it is at a low angle of attack, and at ...
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  • 57.8k
4 votes

Why didn’t the Concorde have flap-canards like the Tu-144?

It did not need them. Concorde could operate from most commercial airports and did not need especially long runways. Retractable canards add drag and the mechanism is a point of failure. I fail to ...
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  • 2,805
4 votes
Accepted

Does deploying flap change the aspect ratio of the wing?

The aspect ratio of a wing is defined as: $$ \text{AR} \equiv \frac{s^2}{A} , $$ where $s$ is the wingspan and $A$ is the total wing area. Some types of flaps are not only increasing wing camber, ...
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  • 44.5k
4 votes
Accepted

Do any regional turboprop aircraft have leading edge high lift devices?

Neither the Dash 8 nor ATR families (which cover the bulk of regional TP market) do. Your last two sentence pretty much summarizes it. Some of the additional lift potential of a slatted wing is from ...
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  • 104k

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