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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0answers
11 views

Do surfaces ahead of propellers decrease thrust?

I have had this question for ages, nearly impossible to find anything on the web. My experiments confused me even further! Its concerning the blockage effects of surfaces ahead of a propeller. For ...
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1answer
58 views

Does a high pitching moment symetrical airfoil exist?

Looking for high pitching moment symetrical airfoil. I understand the Zenith 701 uses a reverse NACA4412 as it has a high pitching moment. This allows for a smaller horizontal tail. What about a ...
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Are exoskeleton wings technically possible?

While there have been a robot simulating a bird, could be there also an exoskeleton wing system for a human? Main design considerations: a) only human powered b) using an additional, or exclusive ...
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2answers
81 views

Shouldn't the upwash on an airfoil increase the effective angle of attack?

From what I understand, induced drag comes from a reduction of the effective angle seen by the airfoil. However, from wind tunnel smoke visualization, we can see that the streamlines at the leading ...
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1answer
117 views

Do Airbus avionics give good deadstick landing outcomes? [on hold]

We have recently had a second good outcome, in Russia, of a no power landing of an Airbus aircraft. The first was the "miracle on the Hudson". It appears to me that the avionics of this aircraft are ...
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How do you design a NACA intake?

What are the construction guidelines to geometrically build a NACA intake (submerged intake) for aircrafts? The relationships between the aerodynamic performance parameters (ram recovery, drag, and ...
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2answers
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What is the function of cross bracing of interplane strut?

Pic 1 is the top and lower wing of a biplane called Bloop Ultralight,what is the function of the cross bracing between the interplane struts as seen in pic 1(I'm not talking about landing and flying ...
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2answers
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Does the explanation of why slower airfoils are more efficient involve less energy loss from heating or compression of the working fluid?

We read time and time again, how more efficient slower airfoils such as helicopter rotors, props, and sailplane wings are compared with rapidly rotating fan blades or faster (still subsonic wings). ...
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How to calculate the minimum radius of a turn at high alpha, without banking?

How to calculate the minimum radius of a turn at high alpha, without banking? One sees the radio control guys flying their planes at 30deg AOA in a 5' circle at walking speed, without banking. ...
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3answers
109 views

Is a high alpha sideslip possible and safe?

Is a high alpha sideslip possible and safe? We use a sideslip to increase drag when trying to reduce altitude before landing on a short runway, etc., which is crossing your rudder and ailerons, to ...
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Why does this Jet Provost strikemaster have a textured leading edge?

I was at Duxford recently, and spotted a Jet Provost Strikemaster that had a rough texture applied to a portion of the leading edge of the wing. Does anyone know why this was applied?
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5answers
287 views

Wouldn't a triplane be much more efficient than a monoplane of same wing area?

Note: not a duplicate of Can biplane or triplane designs be revived with modern materials? This question compares a high performance triplane with high aspect ratios and high gap, to a monoplane. It ...
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Does flying an airplane upside down imply negative AoA? Why?

I saw the statement below in this answer: Note that for normal level unaccelerated flight $C_L$ is always > 0. The minimum $C_L$ is a negative value for negative AoA, and would mean that the ...
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1answer
67 views

Does using wings with different wing loadings work the same as a swing wing, without swinging the wing?

Does using wings with different wing loadings work the same as a swing wing, without swinging the wing? Was just wondering: we need the maximum co-efficient of lift at slower speeds at takeoff, but a ...
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4answers
949 views

What costs less energy? Roll or Yaw?

Let's say you want to perform a turn anywhere from 1 to 90 degrees. Which will cost less energy? A bank or a yaw? Using the rudder does produce extra drag, because the control surface is deflected ...
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131 views

Is an 400+% increase in lift with distributed propulsion realistic?

Is an 440% increase in lift with distributed propulsion realistic? I understand NASA swapped out the wings on their test plane with distributed propulsion from 17psf to 45 psf. That's a factor of 2....
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2answers
202 views

What would happen if ultralights had mountain bike style treaded tires?

What would happen if ultralights had off road treaded tires? Mountain bike tires are made for going off road through mud, etc. They have voids between the tire lugs to clear mud etc. Why not off ...
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1answer
95 views

Does the wing always have an adverse pressure gradient along the chord?

I know that there is an adverse pressure gradient on the upper surface of the wing, which leads to boundary layer separation. Is there any condition under which there is no such adverse pressure ...
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Do contra-rotating props have worse tip-vortexes than single props?

As I understand it, blades from a propeller have their own tip vortexes, because the blades produce lift under the same aerodynamic principles as wings. So they must have tip vortexes too. So with ...
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1answer
99 views

When Airplane is reducing altitude from flight level (cruise), which one is more efficient

When an airplane is reducing altitude, say due to preparation for landing, the nose is tilted down. That I got from a video on Youtube which explains the way an airplane is going down until it reaches ...
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1answer
72 views

How to calculate minimum flying speed in distributed propulsion?

How to calculate minimum takeoff speed due to distributed propulsion? Is there a quick way or rule of thumb way to calculate effects of distributed propulsion? I understand NASA is doing research in ...
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4answers
5k views

Does a 4 bladed prop have almost twice the thrust of a 2 bladed prop?

Does a 4 bladed prop have almost twice the thrust of a 2 bladed prop? As a general rule, I'm told GA planes generate 4 lbs of thrust per horsepower. (Source: Zenith School of Airplane Design, Flying ...
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How do Alaskan bush pilots land and take off in 10'? [closed]

How do Alaskan bush pilots land and take off in 10'? Just looked at a video of the Valdeez STOL competition with pilot's taking off and landing in 10' How do they do it? And no, they don't have a ...
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1answer
118 views

How to design a near vertical take off airplane?

How to design a near vertical take off airplane, conceptually? Say I have an airplane, similar to a Zenith 701. Say that it has a stall speed of 50 mph and a wing area of 60 sq ft, and it weighs ...
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1answer
71 views

At what angle-of-attack (sideslip angle) would a symmetrical vertical fin stop “helping” a deflected rudder produce sideforce? [duplicate]

For rudder deflection angles of 5, 10, 20, 30, and 45 degrees, at what (negative) angle-of-attack does a fin-rudder combination (including dorsal fin if present) create exactly the same amount of ...
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2answers
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At what angle-of-attack (sideslip angle) would a symmetric vertical fin plus a deflected rudder have a lift coefficient of exactly zero?

For rudder deflection angles of 5, 10, 20, 30, and 45 degrees, at what (negative) angle-of-attack does a fin-rudder combination (including dorsal fin if present) have a lift coefficient of exactly ...
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1answer
2k views

What is this flat plate sticking out of the tail of Learjet 24D?

What is this protrusion on the tail of Learjet 24D (shown just above the avro museum logo) and what is its function? Learjet 24D Tail closeup Zoomed out image of the Learjet tail Source: images ...
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3answers
148 views

Does a biplane need wing twist?

Does a biplane need wing twist? I understand wing twist is used to: creat a soft/partial stall ( hopefully create a partial stall before a full stall) balance the wing so a smaller horizontal tail ...
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7answers
9k views

Why are prop blades not shaped like household fan blades?

My two projects right now are learning to fly and 3D modeling a replacement blade for antique fan, and a question occurred to me: Why are airplane propeller blades not shaped like household fan ...
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2answers
216 views

Historical gap in high aspect ratio wing transport aircraft

Reading about recent Boeing's high aspect ratio wing concepts for commercial aircraft, such as TTBW and SUGAR, I couldn't help but think of the Hurel-Dubois aircraft, where similar aerodynamic choices ...
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2answers
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How can I calculate the speed gain from using multiple STC modifications together?

Looking at a parts manufacturer website, they list various STC'd modifications for Mooneys with estimated (cruise?) speed gains for each. However, I've heard that those gains are not additive. For ...
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1answer
68 views

Does a decreasing shape factor correspond to greater or reduced probability of separation?

The shape factor ($H=\frac{\delta^*}{\theta}$) is the ratio of displacement thickness, a measure of the thickness of the boundary layer, to the momentum thickness, a measure of the shear stress. I ...
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2answers
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What would be the ideal plane specs that minimizes consumption for 1000 kg of cargo payload (slow speed, wing span, whatever..)?

Speaking of electric planes, I wonder what'd be the optimal specs if the only variable that we'd try to optimize was consumption (assuming a 1000 kg payload and 600 mile legs, unrestricted runway)?
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Why does RPM for a fixed-pitch propeller change with an aircraft's pitch?

Talking bout a C-152 - If I pitch the aircraft down, and without adjusting the throttle, the RPM would show an increase. Pitch up, and without adjusting the throttle, the RPM shows a decrease. I've ...
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3answers
154 views

How can an all flying rudder be almost 100% more efficient than a vertical stabilator and rudder?

How can an all flying rudder be almost 100% more efficient than a vertical tail and rudder? According to the Zenith school of aircraft design, a rule of thumb for the size of an all flying rudder is ...
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1answer
90 views

Where is the midspan airfoil located on the 737?

The 737 has a root airfoil, two midspans, and one outboard. Is the midspan located under the fuselage or between root and tip?
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1answer
98 views

How is the flow of air through a NACA submerged inlet determined?

This question pertains to the design and/or selection of NACA submerged inlets. I am trying to understand what kind of airflow would enter a NACA submerged inlet/scoop and am looking for a good ...
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2answers
216 views

Does a skinless fuselage add to the likeliness of an unrecoverable spin?

While at Air Venture this week, I happened to hear a pilot of a small experimental airplane say that he liked the skinless (Naked) look his airframe had at one point during the build, but that he ...
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2answers
102 views

Do vortex generators increase Re of a wing?

Do vortex generators (VGs) increase Re of a wing? I understand that VGs re-energize the boundary layer on a wing. I understand it turns laminar flow into attached turbulent flow. Doesn't that mean ...
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1answer
103 views

Does using a reverse high Cm horizontal tail airfoil coupled with a low Cm wing increase horizontal tail effectiveness?

Does using a high Cm reverse horizontal tail airfoil coupled with a low Cm wing increase horizontal tail effectiveness? Just noticed that the Zenith 701 wing uses a NACA650-18 which is low $C_m$, ...
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1answer
95 views

Could helicopters use a rear wing to get more lift from the rotor vortex?

Could a wing be added to the rear of a helicopter to catch the vortex from a helicopter for more lift? How would that affect transitional lift while in forward flight? Source: https://www.danubewings....
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What is MCAS trying to fix on B737 MAX?

New sources such as Seattle Times and Aviation Week provide a pretty good overlay of the MCAS function on B737 MAX. However, I'm unclear as to the issue that MCAS is attempting to fix. From what I can ...
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2answers
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What happens when you put vortex generators on both sides of a symmetrical vertical tail?

What happens when you put vortex generators (VGs) on both sides of a symmetrical vertical tail? I understand a horizontal tail with a classic foil like a NACA 0012 has a max cl of about 1.5. I ...
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1answer
143 views

Why limit the bank angle to 10° when passing through FL300 on a B737-800?

When passing thought FL300, we are instructed to set the bank angle limiter on the MCP to 10°. I know one of the reasons for this is that we are thrust limited so maneuver capability decreases. Are ...
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1answer
102 views

Does a RC aircraft require suspension in landing gears?

we engineering students are preparing for a particular competition with dimensions of 170 in. (length + breadth + width) for that competition we require landing gear but for that are we supposed to ...
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1answer
150 views

Is lower wing loading safer?

Is lower wing loading safer? Looking at the ultralight specs in Canada, they call for a max wing loading of 12psf. In fact, amateur built aircraft in Canada cannot have a wing loading over 20psf,I'm ...
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Do open propellers experience pre-entry drag (additive drag) like an engine in nacelle?

Engines in a nacelle experience pre-entry (also called additive) drag. Do unducted propellers experience it too?
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2answers
298 views

What is the function of interplane strut of a Biplane?

What kind of load does the interplane strut(s) carry,is it compression, tension or shear? In order words,what's their function and how do you calculate the force that the interplane strut carries?
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114 views

Compression and tension members of a biplane wing

I get why the upper wing of a biplane is a compression member (because the flying wire is attached to it at an angle) but what I fail to understand is why the lower wing is the tension member of a ...
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1answer
100 views

Why does the use of reverse thrust in flight on the DC-8 cause areas of separated/reversed airflow over the wing?

The DC-8 is one of only a few jetliners that can safely use reverse thrust in flight; even so, reversing the inboard engines (the outboard engines can only be reversed on the ground) while flying ...