Questions tagged [aircraft-design]

Questions about the different choices that aircraft designers (typically aerospace engineers) make in order to create an aircraft.

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Can the rudder be considered part of the vertical stabilizer, and the elevator part of the horizontal stabilizer?

Or is it strictly correct to say these are separate elements, and you can't call the whole a "stabilizer"?
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1 vote
1 answer
111 views

What are typical CLmaxTO and CLmaxL values for modern aircraft?

Roskam gives these values for typical ranges: However several of his tables are off (for example he estimates typical cruising L/D at 13-15 when many planes are above that). Does anyone know typical ...
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4 votes
1 answer
344 views

What would be the advantage of a Puller vs. Pusher configuration on Embraer's new Turboprop?

Embraer recently teased a turboprop aircraft with aft-mounted, open rotor engines. Why would this aircraft not use a pusher configuration? The reasons that are frequently stated as a benefit for a ...
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3 votes
1 answer
151 views

How can my CD0 estimation be improved?

In this question (link) @PeterKämpf asked me to give a basis for my results. I will share my method for estimation here to see if you guys agree it is correct and how I can improve on it. Note that I ...
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1 vote
1 answer
284 views

What are typical values of CD0 for commercial high-subsonic jets?

Torenbeek (engineer famous for his book on aircraft design) indicates 0.014-0.020. However I've been estimating values for typical planes like the B737/A319 and I'm getting values of 0.026-0.027. I'm ...
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1 vote
0 answers
48 views

How is a design cruise altitude picked? [duplicate]

Different planes have different design cruise altitudes, given by the manufacturer. You can find these in their Airport Planning Manuals or in Jane's All the World's Aircraft. I know that the first ...
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3 votes
1 answer
276 views

What are engineers trying to maximize when they design for takeoff at MTOW? (It seems to me the only free variable is the OEW.)

For a commercial flight, the payload it carries is the weight of passengers and their baggage. Therefore fixed by seat configuration. Fuel weight is determined by the range of the flight. MTOW or ...
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5 votes
3 answers
731 views

How to correct the design of an aircraft that is not speed-stable during approach?

I was just wondering if an aircraft is found to NOT be speed stable during the approach flight phase, what might a designer be able to do to stabilize the aircraft without adversely impacting its ...
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4 votes
1 answer
415 views

Would an oval fuselage fly as well as a round one?

I was looking at various planes, and was wondering why we don't have oval shaped fuselages instead of only round ones. Is there a reason? Perhaps aerodynamics, or stresses?
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2 votes
2 answers
488 views

Use of a solenoid valve over a selector valve

When designing a low-wing light aircraft with two integral tanks at the wings and a collector tank in between, what type of valve should be used to allow the pilot to select the integral tank which ...
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1 vote
0 answers
104 views

Why doesn't the -30% SFC fully account for the dramatic reduction in fuel consumption compared to the 1960s?

In looking at the specific fuel consumption (SFC) of some aero engines I find that for example, the Rolls Royce Conway turbofan engine had typical cruise SFC of 0.874 lb/(h lbf) whilst the most modern ...
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2 votes
0 answers
178 views

Why don't I see this kind of split ailerons on aircraft?

Why don't I see split ailerons that work like spoilers going up and like normal ailerons going down? Isn't that a good way to get rid of adverse yaw?
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6 votes
5 answers
768 views

What is the principle behind flight of airplanes? [duplicate]

What is the principle behind flight of airplanes? Need a simple answer for grade 7 student. Thank you
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3 votes
1 answer
91 views

Angle of Attack influence on Adverse Yaw

we are analyzing an aircraft's lateral-directional control characteristics with self-made code. We have observed that the aileron's influence on the body axis yaw moment is quite sensitive to the ...
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0 votes
2 answers
211 views

How are cabin pressure and oxygen level maintained inside the airplane? [duplicate]

How are cabin pressure and oxygen level maintained inside the airplane?
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1 vote
0 answers
47 views

What's this outlet on the wing of Eurofighter Typhoon EF2000 for? [duplicate]

I was seeing this image and saw this outlet. It's not the outlet of an APU, is it?
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1 vote
1 answer
287 views

What is the dihedral angle of the A380?

It is understood that the A380 has a sweepback angle of 33.5 degrees and a taper ratio is approximately 0.3. However, what is the dihedral angle of this aircraft?
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6 votes
0 answers
122 views

Why was the minimum turbulence intensity that commercial airliners have to withstand increased?

From 50 fps turbulence intensity at VC to 90-100 fps turbulence intensity at VC. The amended FAR design criteria was introduced in 1980 or 1981 for commercial airliners. What prompted this change?
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2 votes
1 answer
425 views

What trailing edge flap design does the A350 use? Is it similar to the A380?

Both Airbuses have similar flap deployment based on some YouTube videos I have watched, just wondering if they both have the same flap design being "Single-Slotted Fowler Flaps".
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7 votes
2 answers
2k views

What flap design does the A380 use? Is it Fowler flaps, slotted flaps or a combination?

I have looked at maintenance manuals, the Airbus website, and Wikipedia but still could not find a definite answer as to what trailing edge flaps the Airbus A380 uses.
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0 votes
1 answer
209 views

I'm trying to replace the Colomban CRI CRI engines with twin 72v 3000w dc electric motor. Will the plane fly?

This is the 72V 300W DC motor: (source)
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5 votes
3 answers
221 views

Why should Mach wave angle be less than wing sweep angle?

This is from my lecture notes: I see that this is so you can have subsonic flow over the wing planform, but why is this desirable? And are there more reasons? I can think of heat being an issue if ...
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5 votes
3 answers
281 views

Ground effect and Lift coefficient

Is there a correlation between the lift coefficient and the proximity between the wing and the ground? I know that the lift coefficient is dependent on angle of attack; However, based on experiments ...
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2 votes
1 answer
170 views

When the F 16 landing the flaperons are used for rolling due to the functionality as ailerons, but after touching the ground it is the same?

In landing gains the flaperons are down 20 degrees. If you have to do corrections of the bank angle on approach then you move upward only one of the flaperons. But after touching the runaway it is ...
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  • 1,805
1 vote
3 answers
234 views

How can I make a serious wind tunnel?

I am looking for specifics of building and the operation of low speed wind tunnels, but most diy wind tunnels on internet are improved versions of science fair projects at best. What would I need to ...
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1 vote
1 answer
129 views

What causes air flow towards fuselage near the winglet?

I am trying to understand how winglets are beneficial in reducing induced drag and I came across this article; https://www.boldmethod.com/learn-to-fly/aerodynamics/how-winglets-work-to-reduce-drag-and-...
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  • 898
0 votes
2 answers
169 views

How can I calculate the tail area required to achieve longitudinal static stability?

I've got a longitudinal stability question. I've not attempted this question yet as I didn't know where to start from, also my lecturer hasn't explained static stability to us clearly and I needed a ...
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4 votes
1 answer
466 views

Are the emergency exits on a Boeing 747-400 plug doors?

Rossiya Airlines flight FV5625 to Antalya suffered an incident at the gate when a passenger opened an emergency exit (seems to be the L3 door, from what I can tell) "because they felt too hot&...
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1 vote
3 answers
117 views

Is the classical definition of induced drag merely a mathematical construct?

I understand that the presence of vortices at the wing tip cause part of wing to see a higher angle of attack and cause more drag. But the explanation that lift vector tilts backwards seems like a ...
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  • 898
5 votes
4 answers
650 views

Can any helicopters use negative collective to descend rapidly?

On a helicopter, the collective is used to adjust the attack angle of all the main-rotor blades in the same direction by the same amount, causing the amount of lift generated to increase or decrease ...
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1 vote
1 answer
81 views

When, and how to calculate this, you can expect too much Wing Dihedral generates Dutch Roll, increases in Drag? [closed]

The question comes from the Arup designs, and the engineer who turned it into blueprints, Hoffmann, ('A Novel All Wing Airplane', Raoul J Hoffman, Popular Aviation, March 1935, pp 163 and 196), they ...
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3 votes
1 answer
289 views

Why is sweep angle measured at the 25% chord?

If you look at wing planforms of e.g. the Spitfire, you can see that the sweep measured at the 25% chord line is 0°. However, the leading edge is rounded/slightly swept and therefore induces spanwise ...
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3 votes
0 answers
68 views

Do high wings aircraft create an additional vortex in the middle?

At the same time, the air on the upper surface has a tendency to flow in toward the fuselage and off the trailing edge. This air current forms a similar vortex at the inboard portion of the trailing ...
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6 votes
2 answers
2k views

Why does a Cessna 172 have dihedral wings if it has high wings?

"Dihedral goes hand in hand with low wing aircraft, and anhedral goes with high wing". This is what I assumed till now. But when I see a Cessna 172, the wings are a little dihedral. So why ...
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6 votes
2 answers
6k views

Why was the C-5 considered the largest plane possible?

We started to build the C-5 and wanted to build the biggest thing we could https://en.wikipedia.org/wiki/Lockheed_C-5_Galaxy The An-225 is 50% larger and has a shorter life. Did they mean the C-5 was ...
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2 votes
0 answers
66 views

How are Fan pressure of and Static pressure in the turbofan engine related?

If the fan air is ducted to the rear, the total fan pressure must be higher than the static gas pressure in the primary engine's exhaust, or air will not flow. By the same token, the static fan ...
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3 votes
0 answers
91 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 ...
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7 votes
1 answer
1k views

What are all the composites used in the making of fighter jets? What is the green and yellow material on the aircraft in the pictures below? [closed]

Below given are images of various fighter jet manufacturing.
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5 votes
1 answer
142 views

How do engineers estimate the aerodynamic effects caused by jet engines or propellers in wind tunnels?

When aircraft models are tested in wind tunnels they don't seem to have engines or propellors on them. So how do engineers get correct parameters from the experiments? Do they just seal the air inlets ...
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3 votes
1 answer
111 views

Which types of aircraft need a gust lock? Is there a size / performance influence?

Which aircraft require gust locks on control surfaces? Is there a certain range in the middle in terms of size / performance where gust locks (external / internal) are required? From a cursory ...
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2 votes
1 answer
145 views

How critical is trailing edge geometry/sharpness on wing performance?

This question occurred to me when I was meshing an airfoil for CFD analysis having a sharp trailing edge. The upper and lower side smoothly converge having tangency at the end. After hours of ...
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0 votes
0 answers
25 views

How to calculate Longitudinal dynamic stability derivative for a wing? Mq and Mα

How to calculate Moment due to rate of change in pitch(Mq) and Moment due to rate of change in AOA(Mα) manually and How to extract from CFD software? Consider a fighter aircraft is in Case 1- Cruise ...
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1 vote
2 answers
267 views

What are the effects of placing the vertical stabilizer at the front of the aircraft? [duplicate]

I am experimenting with different aircraft designs. The one I am trying right now is a canard (horizontal stabilizer at the front) and the main wings are quite far back. I wondered if it would be of ...
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0 votes
0 answers
227 views

Does this Max Faget April 1, 1969 design for the Space Shuttle look familiar? Is it similarity to existing aircraft at the time?

This answer to Who are the actual lead designers of manned spacecraft? in Space Exploration SE says (in its entirety): Max Faget was involved in the design of every US manned spacecraft flown to date....
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2 votes
0 answers
114 views

How can I design a slotted flap?

I have not been able to find satisfactory methods on design of slotted flaps, or flaps in general. Most of the answers are about eyeballing or experience. Can you guide me on what could be good ...
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  • 898
-1 votes
1 answer
55 views

What is the relationship between aspect ratio and lift-dependent drag? [duplicate]

It has been a long held view that aspect ratio of the wing has a significant role to play in the lift-dependent drag. However, mixed opinions have been expressed on the importance of aspect ratio in ...
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14 votes
1 answer
517 views

Why are there large gaps in the spoilers of the Airbus A300?

The spoilers on the Airbus A300 have large gaps at the bottom: (A300-600R, modified from Wikimedia Commons, original picture by Tennen-Gas, CC BY-SA 3.0) I have never seen any other aircraft with ...
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2 votes
2 answers
353 views

Why do large civil airliners use cold rather than hot thrust reversers?

Is it because cold thrust reversers are best for turbofans and most civil airliners have turbofan engines?
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1 vote
1 answer
78 views

How do i find a supercritical airfoil for my preliminary design?

The following information is available but i don't exactly know where to get the information about SC Airfoils from. Do Airbus , Boeing use secret airfoil that they don't disclose? Cruise Speed = 240 ...
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0 votes
0 answers
44 views

Is Bell eVTOL Nexus the only tilt ducted rotor aircraft among the major aircraft manufatures' eVTOL?

I saw some of multicopters have ducted rotor structure but only Bell Nexus has ducted rotor among tilt rotor eVTOL aircraft. Is this just because It is really challenging to control during transition ...
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