Questions tagged [aerodynamics]

Aerodynamics is the study of how air moves and interacts with solid objects. It is an essential part of aircraft design.

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How would you adjust C_l airfoil values for different Reynolds numbers?

I have graph of C_l (airfoil lift coefficient) as a function of AoA, for Mach 0.7 and Re = 6x10^6. For a given value of C_l, what would be a good way to estimate that value at a different Reynolds ...
0 votes
1 answer
414 views

How to calculate lift coefficient using pressure distribution?

Above is the image of the question I want to ask. Please clarify on how the pressure coefficients of the upper and lower surfaces of an airfoil can be used, also if there is a set equation to ...
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4 answers
149 views

How to calculate optimal flight climb angle?

I am trying to calculate the optimal flight climb angle based off of some basic power calculations for an aircraft on steady climb with an angle of theta. Doing a balance of forces I obtained the ...
4 votes
1 answer
138 views

Relationship of propeller RPM, blade pitch, and drag at very low blade pitch angles

I'm researching the 2016 crash of a PIA ATR-42 in Pakistan, the report on which was recently released. Link to the report: https://www.caapakistan.com.pk/Upload/SIBReports/AAIB-386.pdf During the ...
7 votes
4 answers
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Can the lift equation be used for the Ingenuity Mars Helicopter?

I am currently working on a basic simulation of the Mars Helicopter Ingenuity, and I am having trouble interpreting the outputs I am receiving from the lift equation. The equation reads as follows: L =...
61 votes
11 answers
43k views

How do wings generate lift?

Just the basic question that every aviation enthusiast must be curious about: exactly how does a wing generate lift?
2 votes
3 answers
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Do aircraft pitch down even at very low angles of attack (below 0°) in a strong sideslip?

I was doing an analysis of an aircraft (specifically the PZL Koliber 160 with the NACA 63A416) strong sideslip conditions (beta=30° for example) in OpenVSP at various angles of attack, and observed ...
-3 votes
1 answer
85 views

How to calculate thrust force of an aircraft for steady flight? [closed]

I was tasked with finding a mathematical model for obtaining thrust power in a UAV in steady level flight by a professor, and he has yet to tell me whether my approach was appropriate or not. I would ...
0 votes
1 answer
191 views

Are there retractable, compact hang gliders?

I was wondering if there were hang gliders that you could, say wear on your back, in which the wings would retract into the suit. Kind of like the falcon in the mcu? If they aren't there, why not?
4 votes
1 answer
261 views

Why is the cross-sectional shape of some airliners' nose not perfectly a circle?

I found that the cross-sectional shape of some jet airliners' nose is not perfectly a circle. For example the Boeing 737 aircraft: (source: aeroprints.com via Wikimedia Commons, CC BY-SA 3.0) Look at ...
12 votes
7 answers
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Are there cases where a double horizontal stabilizer is useful?

I was watching Agents of Shield recently, and in it the team fly a plane that's claimed to be a modified C-17 Globemaster. It has two extra engines, rotary turrets, and, according to the wiki, a pair ...
1 vote
1 answer
349 views

Does altitude affect glide ratio?

Lower altitude means higher air density, which means more liff, which means a glider can maintain a given glide slope at lower airspeed. As a rule, aircraft tend to have higher peak L/Ds at low ...
-1 votes
2 answers
116 views

What are the loads in a horizontal stabilizer? [closed]

I am doing a project and I can't really find any complete information on how to estimate and calculate de loads (lift, weight, drag...) in a horizontal stabilizer. If someone could give me good papers ...
1 vote
2 answers
8k views

What types of maneuvers increase the load factor on the aircraft?

Out of turns, stalls and climbs, which of the basic maneuvers increases the load factor on an airplane as compared to straight and level flight?
5 votes
1 answer
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When were airbrakes used for the first time in aviation?

I would like to have some information about the history of airbrakes.
2 votes
3 answers
135 views

Does twist increase spanwise flow?

Generally speaking, does twist increase spanwise flow, because high pressure at wing root stream toward lower pressure at the tip? I will write example with sailing jib: When sail upwind, jib windward ...
15 votes
2 answers
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Does the Fairchild Metroliner have any unusual handling characteristics?

I have been told by several people that the Fairchild Metroliner is a quite difficult to handle aircraft. Aside from that, I have seen that it has suffered several accidents throughout its history. ...
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1 answer
102 views

Can I calculate fuel consumption for given reduction of drag coefficient?

If plane or car has Cd of 0.35 and 5L/100km, how much will be fuel consumption if Cd is reduced to 0.20 and everything else stay the same(weigth, frontal area,power etc)? Is it possible to calculate ...
2 votes
3 answers
83 views

Fixed-Wing Stall Speed Equation Valid for Differing Planetary Conditions?

For some time I have been looking for a simple stall speed equation that can factor in differing planetary conditions (gravity and air density) and changing vehicle mass, but have failed to find ...
0 votes
1 answer
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Can a Supersonic aerofoil have Max thickness near the middle?

I’m really unsure about this question: Can a supersonic aerofoil have maximum thickness near the middle? so by middle of the aerofoil I mean 50% along the chord Also, how would you actually calculate ...
3 votes
1 answer
422 views

Could the Wright Flyer II takeoff without wind?

The Wright Flyer II could reach about 20 mph of airspeed on the track alone. The aircraft needed an airspeed of about 30 mph to make a proper takeoff (without hanging in ground effect). Before the ...
3 votes
1 answer
179 views

Why does the condensation cone disappears when the airplane starts flying supersonic

In this answer How are condensation cones created by supersonic airplanes? it is said that the condensation cones appear only when the airplane flies at speeds below Mach 1. I am wandering why does it ...
0 votes
1 answer
319 views

Why is there a a nose-up pitching tendency during a forward slip in a Cessna 172?

Why is there a tendency for the nose to pitch-up during a forward slip in a Cessna 172 (According to the TC Flight training manual)? Quote: "If full rudder is used, considerable aileron pressure ...
3 votes
3 answers
126 views

How does an extended slat generate drag?

I am wondering how does an extended slat generate drag because I often read that slots agument lift by increasing critical angle of attack, but they do generate some extra drag. I am curious what is ...
1 vote
1 answer
91 views

How do streamlines look on the wing of a hang glider?

How do streamlines/flow look like on single surface wing of hang gliders, especialy on the lower side? Has anyone installed tufts or done CFD analysis on this?
2 votes
3 answers
319 views

Why increase chord length for supersonic aircraft (swept vs delta wings)?

TL/DR For supersonic transport and a given sweep angle, why are delta wings used instead of swept wings? If you write the drag equations, a sweep of $55^{\circ}$ seems sufficient with no modification ...
4 votes
1 answer
189 views

Matching the Drag Equation to Real Airplane Data

I am trying to compute airplane performance for a piston-driven airplane with constant speed prop using the standard equations for Lift, Thrust and Drag. I have found that there are a couple of useful ...
10 votes
2 answers
2k views

The F/A-18 Hornet and MiG-29 ailerons from the external parts of the wings go up some degrees in flight ,meaning adding " crow" type of winglets.Why?

In some parts of the flying envelope of the F/A-18 Hornet and MiG-29 the ailerons from the external parts of the wings go up in sync. They're made to go one up one down in order to get rolls, not up/...
5 votes
2 answers
113 views

2D to 3D Non-Elliptical Lift Curve Slope Correction Factor Reference

I'm working on automating some aerodynamic calculations for a particular multidisciplinary design tool and in the course of setting it up I ran across this formula from the input theory manual $$ {CL_\...
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0 answers
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Upper critical Mach number

I read on the Wikipedia that some (all?) supersonic airplanes have upper critical Mach number: Supersonic aircraft such as Concorde and combat aircraft also have an upper critical Mach number at which ...
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3 answers
490 views

Induced drag - where does it actually arise from?

Several explanations about induced drag exist. Even if these explanations are simple and appealing (and not necessarily correct) they lack any connection to how actually the concept of induced drag ...
57 votes
4 answers
23k views

Why are the F/A-18 rudders deflected in opposing directions during takeoff?

Looking at some videos and photos of F/A-18 Hornets and Super Hornets taking off from carriers and from airfields, I recognised that the left rudder is pointing right, and the right rudder pointing ...
3 votes
2 answers
403 views

What aerodynamic improvements were introduced on the Boeing 787?

When discussing the Boeing 787, three topics are brought up most often: The new, extremely high-bypass GEnx engines The shift to carbon composite construction and The significant troubles Boeing ...
4 votes
3 answers
150 views

Where to find out the correct values of AOA of Boeing 737 during different phases of flight?

We can say that practically there are minor differences in AOA for each flight (in the same range of weight). But is there any document that states what flight angle is recommended for each of the ...
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V-tail induced roll and main wing design considerations

If the only difference between two hypothetical aircrafts is that one has a conventional V-tail, while the other has an inverted V-tail, then, when rudder pedal is pressed a conventional V-tail ...
1 vote
1 answer
261 views

Are there any lift or lift coefficient equations which factor in the flap deflection angle?

I'm asking this because I tested a NACA 2412 wing with an adjustable flap in a subsonic wind tunnel and I'm getting the lowest Cl values for the highest flap deflection angle.. which to my knowledge ...
4 votes
3 answers
478 views

Is it a better idea to put propellers on the wings than the nose?

Most propeller aircraft have either a single propeller at the nose or two propellers on the wings. Nose propellers have a big disadvantage as the big fuselage can obstruct the airflow of the propeller ...
0 votes
1 answer
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Is air less dense at the upper wing surface,for subsonic speeds?

If pressure drop at top wing side,density of air must also decrease because density depend on pressure and temperature. Same apply on the bottom side where density must increase. So why density ...
8 votes
3 answers
4k views

What is compressibility drag?

I don't mean wave drag here. What is compressibility drag, which is understood to be a form of miscellaneous drag?
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1 answer
128 views

Why does air density drop when speed nears the Mach 1?

In many questions and answers about high speed aerodynamics here it is said that as speed approaches the speed of sound, there is also a decrease in air density. Can someone explain why?.
1 vote
3 answers
255 views

Why can't supersonic flow work its way upstream?

I am reading this textbook today. And it described supersonic flow as follows: In a supersonic flow, because the local flow velocity is greater than the speed of sound, disturbances created at some ...
3 votes
1 answer
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What causes a normal shock wave on a wing?

I am wondering what causes a normal shockwave on a wing? I mean why does the airflow (that becomes supersonic over a part of the airfoil) slows down somewhere over that wing suddenly to a subsonic ...
2 votes
3 answers
1k views

Aerodynamics moment of a wing

An old flight book that I am reading discusses the aerodynamic moment about a wing and talks about an upper and lower lifts. I can see how the pressure distribution on the top surface produces an ...
0 votes
2 answers
2k views

What is the most efficient symmetrical airfoil shape?

What is the most efficient symmetrical airfoil shape to make for a covering for a round upright bar that measures 40mm outside diameter? The speed of travel will be 25Kph and I also need a shape to ...
4 votes
5 answers
1k views

Explained intuitively, why does aspect ratio affect induced drag?

Over the last few hours, I've been trying to intuitively understand induced drag, and how aspect ratio affects it. I already know the equations, but while they explain the relationship, they do not ...
12 votes
5 answers
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What is the Beggs/Mueller emergency spin recovery technique?

I've always used PARE for spin recovery: Power to idle Ailerons neutral Rudder opposite the spin until rotation stops Elevator forward to break the stall What is Beggs/Mueller emergency ...
27 votes
9 answers
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Why do the missiles on an F-16 point slightly down?

I've been wondering this for quite a while: Why do the missiles on the F-16 point down a little bit? I went and did a little searching and found out that the F-16 isn't the only plane that has this ...
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1 answer
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what reference of airfoil is used to define lift and drag?

On aerofoil section, the force of lift acts perpendicular to, and the force drags acts parallel to the : A: chord line B: flight path C: aerofoil section upper surface D: longitudinal axis
1 vote
3 answers
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How do I calculate the center of lift?

See my other question here for the background context. Consider this simple plane. I have applied the 4 basic forces: lift, drag, weight, and thrust. My question is, where, precisely, do I apply the ...
3 votes
2 answers
280 views

In the context of aerodynamics, what is a polar?

Many aerodynamics discussions (including several on this site) talk about "polars" without ever explaining what they actually are. As with any technical term common to a field, once the ...

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