In real life, there are significant differences between a flat bottomed airfoil, semi symmetric airfoil and symmetric airfoils; I have significant flying time in all three types and they are all different in their lifting capabilities, efficiency and stall characteristics. In SP, the three airfoil choices are also significantly different from one another and guess what? The three types do quite a good job in simulating the differences shown in real life. The following information may be of use to the builder who wants to advance to the next level of realism on their next build:
Flat Bottom (or "Cambered"):
Common aircraft types -- slower, more forgiving aircraft, light civil types, early aircraft. Aircraft I've flown with this type of airfoil design: Cessna 152, 172 (among others).
Characteristics -- SP's "Flat Bottom" airfoil selection uses the NACA 23016 profile. Good lift at low speeds but the highest drag airfoil design, lower stall speed, predictable stall characteristics with pronounced stall warning. Produces lift more through Bernoulli's principle than through impinging airflow.
Discussion -- Due to its more curved upper surface, where faster moving air on the top of the wing produces low pressure on the top of the wing and a lifting effect (Bernoulli's Principle), the flat bottomed airfoil produces lift at all times, even at zero Angle of Attack (AoA - the angle at which the moving air meets the chord line). Any time lift is produced, a lot of drag is produced--this type of lift is known as "induced drag", as opposed to "parasite drag". Since a flat bottomed airfoil will produce lift even at zero AoA, the amount of drag produced by this airfoil will always be greater than other airfoil types. This is great for slow moving aircraft, which need the lift in spite of their low flying speeds, but not the most efficient airfoil design for faster and/or longer ranged aircraft. The flat bottomed wing is typically used on light aircraft where forgiveness and predictability of stall characteristics are important, as stalls of this wing type will typically be preceded by a noticeable buffeting produced as the airfoil over the top of the wing separates, followed a nose down pitching as lift is lost and the wing becomes stalled. However, recovery is typically quick as the speeds required to generate lift are low (there's an entire discussion on stalls, critical AoA and airspeeds which I will not get into at this time). In SP, builds with this airfoil tend to be "floaty" on landing, just like a light plane, produce plenty of lift at low speeds, stall with a noticeable nose down pitching and are inefficient at high speeds. Unfortunately, the buffeting preceding a stall is NOT replicated in SP.
Symmetric:
Common Aircraft Types -- Fighters and other aircraft which typically operate in the transonic and supersonic flight regimes. Aircraft I've flown with this type of airfoil design: T-38.
Characteristics -- SP's "Symmetric" airfoil selection uses the NACA 0009 profile. Requires a positive or negative Angle of Attack to generate lift, produces less lift than other airfoil shapes, more efficient than other airfoil designs at high speeds. Produces much of its lift by moving air impinging on the bottom of the wing.
Discussion -- To be clear: Very few wings are actually 100% symmetric...however, wings which are close to symmetric are termed as "symmetric" wings. The closest wing I know of to the ideal symmetric design is the F-104's wing, which possessed ALL of this design's benefits and drawbacks in spades. A symmetric wing needs a positive AoA to produce lift and allow the aircraft to take off, though it will, in theory, produce lift with either a positive or negative AoA. The great benefit of this design is the fact that at zero AoA, zero lift is produced, which means zero induced drag and a far more efficient airfoil. The pilot flying an aircraft with this wing only needs to produce as much lift as necessary to keep the jet flying, there is no default drag produced by simply moving through the air as there is with a flat bottomed wing. Of added benefit, on most aircraft (FBW types excepted) equipped with a conventional tail, the tail will push DOWN as most aircraft are designed to be slightly nose heavy for stability. The amount of downward push needs to increase as a wing produces more lift, so for a flat bottomed wing, the wing may be producing more lift at high speeds than is required due to the fact the wing is producing a default amount of drag by simply moving through the air. So, for a flat bottomed wing, the tail is pushing down more than it would on a symmetric airfoil. This downward push is lift, which produces additional induced drag. The symmetric wing has no such problem as it's possible to fly with exactly the amount of lift required to remain airborne and nothing additional from either the wing itself or the tail pushing down, which makes it highly efficient and the best design where low drag and high speed are most important. However, there are many drawbacks to this design. First, the fact that no lift is produced without an associated AoA makes high speeds necessary to allow the tail to push down and raise the nose of the aircraft. In fact, as opposed to high speed flight, this wing is less efficient than a cambered airfoil in the slow flight regime. These are all drawbacks during takeoff, in the landing pattern and when landing, especially on shorter runways. Additionally, this wing's stall characteristics will kill a pilot who doesn't recognize the wing is stalled. As the wing approaches it's maximum lift, as it will in the pattern and during landing, it begins to produce a separated airflow and a light buffeting. As the wing transitions to a nearly completely stalled state, the buffeting will increase to a heavy buffet and the pilot needs to recognize the difference between a lightly buffeting wing (good) and a heavily buffeting wing (very, very bad). Additionally, a symmetric wing will not produce a downward nose pitch when completely stalled...instead, the buffeting increases, the wing loses nearly all it's lift past the critical AoA and a very high sink rate results (the T-38 would peg out the rate of descent on the variometer--that's more than 4,000 fpm!). Pulling back on the stick just makes it worse by producing more AoA plus drag, and an unrecognized, fully developed stall in the traffic pattern will result in the jet hitting the ground in a nearly flat attitude, even with both throttles in full afterburner. Added to this, this huge rate of descent and the higher speeds required for the wing to produce lift requires a lot of altitude to recover. "Max [afternburner], relax [ease off the back pressure to reduce AoA] and roll [wings level to maximize the lift vector]" was the mantra to recover from a stall in the T-38. However, to a fighter pilot, "SPEED IS LIFE" and the performance advantage from a symmetric wing is so great that pilots are simply trained to recognize the appropriate buffet, AoA indicators are typically installed and pilots simply avoid stalling in the first place. SP does a pretty good job simulating these effects except, unfortunately, there's no buffeting modeled in game, though there are ways of doing it with a piston.
Semi-Symmetric:
Common Aircraft Types -- Heavies such as airliners, bombers, subsonic aircraft. Aircraft I've flown with this type of airfoil design: 737.
Characteristics -- SP's "Semi-Symmetric" airfoil selection uses the NACA 23015 profile. More curved ("cambered") than symmetric airfoils, but not flat bottomed, these airfoil designs attempt toe the line between the good and bad attributes associated with flat bottomed and symmetric airfoils.
Discussion -- Having a more curved (or more curved) upper surface with a lesser curved bottom surface, these wings produce much of their lift due to faster airflow over the top of the wing, though increasing the wing's AoA will also produce more lift through impingement. The more curved a semi-symmetric airfoil, the more good and bad characteristics it will share with purely flat bottomed airfoils and the more symmetric a wing, the more good and bad characteristics it will share with purely symmetric wings, so designers will toe a line where their desired attributes balance out to produce an the most lift, while remaining relatively efficient. This is why they are common on transport category aircraft, which operate in the subsonic speed range, cruising at Mach .78 - .93. Stall characteristics are a mixed bag, as any stall is exacerbated due to a transport aircraft's large size, heavy weight and, often, swept wing design.
SP specifics: I've always designed my builds using an accurate airfoil shape. I would never use SP's "Flat Bottom" airfoil on a fighter aircraft build...it's just too noticeable to me personally as I notice things such as how a build lands, better acceleration and associated stall characteristics. SP actually does a pretty good job in distinguishing between the wing types, though stall characteristics are a bit iffy sometimes, probably due to the fact modeling the complex events happening in a stall is difficult. One thing I wish were present is a stall buffet. Often, I'm just testing a design with a symmetric wing and I'll just develop a high sink rate and lose control without recognizing the stall...oops! Better open up the Dev Console and monitor the AoA in real time or build an AoA indicator or stall warning system while I conduct flight test.
Wing profile is also highly correlated with fuel consumption, which is what led me to post this topic...all too often the community will gripe that they're burning way too much fuel. We can have really long discussion on how drag is a huge determinant on fuel consumption at cruise speeds and how IRL, SP RPM is linear with thrust (IRL, 80% RPM produces about 1/2 the thrust in a jet engine), that no one flies around in full AB at Mach 3.3, except for SR-71s (which had a high fuel consumption but was a pretty big jet with lots of fuel), etc., etc.
Suffice to say, yes, SP fuel consumption is probably a bit higher than IRL, however, if you're flying your F-15 built with a flat bottomed wing at Mach 2.5, yeah, it's going to be WAY, WAY higher than IRL. Case in point, on a recent build I was flight testing for a friend, I substituted "Semi-Symmetric" wings for his "Flat Bottom" airfoil. At approximately 40,000' and the type's published cruise of 432 knots TAS, the flat bottom wing required 55% power and could only fly for 53 minutes on about 80% fuel. Using a semi-symmetric wing...the wing change ALONE increased the endurance to 73 minutes, and this was on 70% fuel! Proof that the wing design has a huge effect on aircraft performance within SP!
(To calculate endurance, open up the Dev Console and type in "DebugExpression (100/rate(Fuel*100))/60"...don't omit the space.).
Happy hunting and fly safe!
I prefer flat bottom for my primary wing, and semi symmetric for my horizontal stabilizer because it can make flawless maneuvers using my fighter.
neat
Thanks for sharing, that is very helpful. @Zaineman
@ChiChiWerx
oh i see there's a typo, some how i cut and pasted a double
here you go again
@GorillaGuerrilla the link is incomplete and doesn’t take me anywhere when I paste it into the browser. Can you repost and I’ll take a look? To create links in comments or posts, use the following format: [whatever text you want to use for your link] (https//webpagelink.com). Be sure to delete the space between the “]” and “(“ and the link will be created when you post your comment.
@GorillaGuerrilla yes, IMHO, just to make a WAG, SP physics is around 80% accurate, but only 65% of the time. Don’t bother with the area rule test as there aren’t any supersonic effects in game, which is why swept wings make no performance difference. One of the biggest shortfalls, in my opinion. I’d love to see the rapid increase in drag in the transonic range, but as there isn’t even real “airflow” in game, so it’s not unexpected. The way drag and lift increase in game is because the SP environment simply increases drag and lift as a part or wing moves “faster”. It’s a calculation, not actual airflow, which is why putting one part behind another doesn’t block the “airflow”. Sadly, no way to fix it either.
@ChiChiWerx i don't know. sometimes i wonder how close aerodynamic details and physics rules were represented in the codes. like if all behavior are shape based/ area base in relative to oncoming airflow. i had made planes with extreme washout (almost but less than 10 degrees) that seems to be ignored by in game physics. (sorry havent put that plane in my profile yet but will let u know if it's available later). and yes i have been testing the in game physics to some extent i am happy like 99% of the time tho. but then many things are hard-coded in a way so even the so called aerodynamics have lots that have been omitted, i need to be careful of my designs so i dont come up with things that work ideally irl but not here ;) i havent tested the area rule yet but i think i am going to
@GorillaGuerrilla yes, I am well aware of burying wings to simulate lifting body effects. Useful for emulating builds such as F-14, F-16 or Space Shuttle. Also useful in simply using a built up wing instead of the stock block wings available. But this post doesn’t really have much to do with that, it’s really about the different characteristics between the flat, semi-symmetrical and symmetrical wings in SP; my point being there is much more modeled in game than people realize in those options. However, to your point: You’re not the first to maintain that there are brilliant builders who can defy the in game physics model. I say you can’t really do so, though you can exploit the characteristics and gaps of the in game modeling to achieve some interesting and unexpected characteristics. Burying a wing in a fuse and having it still able to produce lift is a perfect example of a gap in the SP physics model that can be exploited—that’s not something that happens IRL. IRL, lifting bodies don’t conceal a wing inside, their very shape produces left as they move through the air at an angle (AoA). FT and good old fashioned XML editing gives the ability to manipulate attributes of individual parts, but it doesn’t allow anyone to alter the basic code of the physics engine. All the code is there and all the variables are being crunched to produce a rational result. A good example of this is drag reduction/deletion—the builder may be causing the physics engine to use “0” as the drag value on that part, but the physics engine is always there in the background, working as expected. So, I’m not sure what you mean by “brilliant” people defying SP physics because you can’t—the SP physics code will always be operational in game.
@ChiChiWerx sometimes the lifting body effect is done well by people who hide extra wings in places like intake ducts or main fuse. here in sp we have brilliant people defying all sorts of sp physics to mimic real physics
@ChiChiWerx Thank you for the quick response ill put this to good use!
@Deputydangle there are many reasons why your build might not replicate exactly the F-14’s performance, default drag is unrealistically high and needs to be edited down, jet thrust doesn’t decrease enough with altitude, so speeds tend to be slow at sea level and too high at altitude and there is no such thing as transonic drag. Simply cranking the power up on SP engines also results in ludicrously unenjoyable acceleration. All that being said, there are ways of coping with these problems, Funky Trees can do a lot. But, recommend using symmetrical wings for any jet fighter, especially the Tomcat, which is designed to fly at high speed and has a symmetric wing IRL. The lifting body effect is harder to replicate; the F-14 isn’t really a big, curved wing shape, it’s a broad, flat area of the rear half of the fuse that works at higher angles of attack, much like a symmetric airfoil. Think about it, the F-14’s fuselage was not designed to produce excess induced drag at zero angle of attack, that would prevent it from flying at fast as possible and the F-14 is a Mach 2.3 jet, very, very fast. Where that rear fuse lift comes in is at high angles of attack, the same at any other symmetric airfoil. I’d recommend using symmetric airfoils for all your wings for your build. That way, you keep the drag at low angles of attack (high speeds) and have the increased lift at higher angles of attack, during slow speed flight as during approach and landing and fighting at slower airspeeds (but don’t get slow in an F-14!).
Hello everyone, Im editing another users F-14 Tomcat and was wondering if anyone could recommend a good wing type for the main wings and the lifting body between the engines. I currently am using a flat bottom airfoil for the fuselage and symmetric airfoil main wings but cant seem to get it right for the most realistic F-14 flight performance. Cheers!
hmmmmmmm interesting....
@Rakoval500k all things being equal, extending flaps, leading edge flaps or slats generally causes the nose to pitch down slightly. The reason is that extension of these devices causes an increase of lift. In order for everything to remain the same, the wing should decrease its angle of attack to produce the same amount of lift, which is why the nose will generally pitch down slightly. The pitch down is probably not nearly as much as what occurs in SP, though, because what happens IRL isn’t replicated in game. The difference is that extending flaps IRL generally changes the shape of the wing (makes it more curved) and often increases the lifting area of the wing as well, in the case of most modern flap designs, which makes the same wing produce more lift. As SP doesn’t actually consider camber, or changes in camber, except for which type you use when building you plane initially (cambered, semi-symmetric or symmetric options), what you get when you “extend flaps” in game is a simulation of what might happen if you have two different wing surfaces which are unrelated, and one happens to be turned at a greater angle to the relative wind (increased angle of attack). Yes, the wing at the greater angle will produce more lift (up until it exceed the critical AoA), but there is no simulation that the flaps produce a more cambered airfoil with better lift characteristics.
Greetings, i have a quection: do the leading edge slats and droops produce a pitch-down moment when deployed in real life? I'm asking because there's no leading edge control surfaces, so we have to simulate the slats/droops by using narrow structural wings on rotators. The game seem to think that our supposed "slat/droop" is actually a canard, thus a noticeable nose-down-pitching moment is produced in our game.
TLDR?
@SnoWFLakE0s really? imagine how more realistic replicas can be
Thamks
If I recall correctly, you can use NACA wing profile types directly using XML edit, so you have a bit more freedom than that of just the default selection types.
@jamesPLANESii 👍
That was a fun novel to read
me over here making the mistake of using a squashed naca 6716 on my knockoff hornet
Very in-depth!
One thing I find is many people highly underestimate just how good SP’s wing physics are. They are actually extremely good, until you get into a stall!
One thing I do is I choose my wing based on how I want my plane to stall, like, I only ever use flat bottom wings on my bush planes since it stalls at a 30 degree AoA, which is way higher than basically any plane other than bush planes. Semi symmetric wings stall at about 20 degrees, and symmetric stall at 15 degrees. I used symmetric on my Airtruk because the wings on the real thing are kinda semi-symmetric, coming on symmetric with an AoA, and shared more characteristics with the symmetric wing than the semi symmetric wing. I made my wings a realistic size and the performance of the plane almost matched exactly with the real thing.
One thing I would say is it would be nice if we could have more choice over the aerofoils we can use. Like, the ability to type in the NACA profile. That would be so cool.
This may take me 20 minutes to read, but I’m gonna read it anyway. Lol
wow, thanks