Chirac is a genius

And a genius is something I'll never accuse you of being.

Really? Thanks for pointing out the obvious. Well that's all fine and dandy Tehran would be "razed", but what about all the dead Israelis?

Idiot.

Well of course he would say that as France has been selling Iran nuclear tech. Thats the same as Phillip Morris claiming cigerrettes arent really harmful. Same reason France was against the invasion of Iraq but just begging to be part of the reconstruction process.

All of the money and none of the blood.

Really? Thanks for pointing out the obvious. Well that's all fine and dandy Tehran would be "razed", but what about all the dead Israelis?

Idiot.

Well of course he would say that as France has been selling Iran nuclear tech. Thats the same as Phillip Morris claiming cigerrettes arent really harmful. Same reason France was against the invasion of Iraq but just begging to be part of the reconstruction process.

That and Iraq bought almost all their military tech from France. France is the first country to object to conflict, but they're also the first to sell weapons to dangerous regimes.

I'm sure someone will argue the US does the same thing. And we do... but we don't piss and moan about losing money when push comes to shove.

i read yesterday that we JUST now stopped selling parts for F-14's to Iran. lol.

but yeah, i read that bit about us selling F14's to Iran a couple years ago. thankfully the F14 won't last a second against modern fighters like the f-22, f-15/16/18, or JSF. regardless, we'd blow the shite out of those f-14's before they could even get in the air. no one ever see's the B2 coming... muahahaa

Actually we stopped selling Iran parts years ago , the rub is when we retired the F14 recently all the spare parts we had which we didn't need anymore went to surplus sales. As it so happens Iran was the only country we ever sold F14's to , so who the fcuk did they think would be interested these parts & would set up middle man buyers for them??? Fcukin' idiots....

Here you couldn't be more wrong. The F22 is the only one above that has any advantage over the F14 , JSF not included since it's not yet in production. The F16 & F18 being "Fly by wire" give the pilot less to think about while flying , yet a skilled pilot & R.I.O. flying a single Tomcat could easily dispatch four or five of each the 16 or 18. Superior speed,manuverability, avionics & Firepower are all enjoyed by the F14 , which is why it took 12 yrs after the deployment of the F18 Hornet to retire the Tomcat. Its role was reduced upon the arrival Hornet (Hornet, took over role of penitrator/strike fighter simply because if lost to enemy fire were far less expensive to replace) The Tomcat retained the prestigous role of "Fleet Interceptor" (Protector of the fleet since it was the vastly superior air to air fighter) , it took several genorations of the F18 for it to become a suitable Interceptor , culminating in the "Super Hornet"....It was totally an economic decision to retire the F14 , the complex "Swing Wing Geometry" Was too dam expensive to Build , maintain & convert to Fly by wire. Fly By Wire aircraft require Far less "Hands on" training fights to master & the physical training of an F14-F15 pilot has to be vastly superior to that of a fly by wire aircraft.

Every argument made here for F14 Vs F18 is mirrored in the F15 vs F16 battle.

Now F14 vs F15 ...Tough call , they were both in competition with each other for Air Force / Navy contracts.
The Navy had no choice but to take the F14 with it's vastly superior low speed performance for carrier based operation due to its "Swing Wing Geometry".

The Air force having no need for short take off & landing capability took the less expensive yet very similar air to air capability F15 even though at their inception the F14 had superior "Beyond Horizon Radar" which wasn't shared with the F15 until about 2 years after it went into production...Remember Until only six months ago the F14 was tasked with protecting our nations most expensive & vital military assets...Our carriers.

What do you want to know about?
Sopwith Camel? F4U corsair? Eindekker, Newport 17, Folk/Wolfe 190 , Super Sabre , Mig 15 ?

Which is better: P-51, P-38? And why? (and sub-models if you care to elaborate)

[quote="fishmahn"]

Without looking anything up I'd go against popular opinion & say the P38.

If memory serves it was the first piston engine plane to exceed 400 MPH , while the P51 had much further range , The P38's twin counter rotating engines totally eliminated "Prop Torqing" and Its 50 caliber Machine guns coupled with 20 mm cannons mounted on the center axis gave it superior and intuitive firepower. And the twin tail with fully manipulating elevator as opposed to trailing edge elevators most common in the era gave it un-matched manuverability.

Plus it just looked bad ass,and the nazis gave it a bad ass nick name...The Forked Tail Devil. 8)

Edit to add pic.

What is that the 25 or 21...I forget....Ill go with 25 & say not a hell of alot except that it was the 1st attempt at countering the F15 & scared the pants out of the pentagon until they realized the Soviets were blowing smoke about it's spec's

That and it's guns were mounted in the nose which gave it an advantage at long range as well as for ground attack because it's ammunition followed a straight line from the aircraft. The downside being you had to be a good shot. In contrast, wing mounted guns crossed paths at a certain point away from the aircraft. Range was limited but you didn't have to be an expert shot to be effective.

All notes aside, both were very competent aircraft in their day.

Actually we stopped selling Iran parts years ago , the rub is when we retired the F14 recently all the spare parts we had which we didn't need anymore went to surplus sales. As it so happens Iran was the only country we ever sold F14's to , so who the fcuk did they think would be interested these parts & would set up middle man buyers for them??? Fcukin' idiots....

Here you couldn't be more wrong. The F22 is the only one above that has any advantage over the F14 , JSF not included since it's not yet in production. The F16 & F18 being "Fly by wire" give the pilot less to think about while flying , yet a skilled pilot & R.I.O. flying a single Tomcat could easily dispatch four or five of each the 16 or 18. Superior speed,manuverability, avionics & Firepower are all enjoyed by the F14 , which is why it took 12 yrs after the deployment of the F18 Hornet to retire the Tomcat. Its role was reduced upon the arrival Hornet (Hornet, took over role of penitrator/strike fighter simply because if lost to enemy fire were far less expensive to replace) The Tomcat retained the prestigous role of "Fleet Interceptor" (Protector of the fleet since it was the vastly superior air to air fighter) , it took several genorations of the F18 for it to become a suitable Interceptor , culminating in the "Super Hornet"....It was totally an economic decision to retire the F14 , the complex "Swing Wing Geometry" Was too dam expensive to Build , maintain & convert to Fly by wire. Fly By Wire aircraft require Far less "Hands on" training fights to master & the physical training of an F14-F15 pilot has to be vastly superior to that of a fly by wire aircraft.

Every argument made here for F14 Vs F18 is mirrored in the F15 vs F16 battle.

Now F14 vs F15 ...Tough call , they were both in competition with each other for Air Force / Navy contracts.
The Navy had no choice but to take the F14 with it's vastly superior low speed performance for carrier based operation due to its "Swing Wing Geometry".

The Air force having no need for short take off & landing capability took the less expensive yet very similar air to air capability F15 even though at their inception the F14 had superior "Beyond Horizon Radar" which wasn't shared with the F15 until about 2 years after it went into production...Remember Until only six months ago the F14 was tasked with protecting our nations most expensive & vital military assets...Our carriers.

ABL is correct, however, he didnt quite emphasize the importance of the most critical factors....training and experiance. A better trained pilot in an inferior aircraft will almost always defeat a poorly trained pilot in a superior aircraft.

As ABL pointed out, the Fxx vs Fyy debated is an old one. In WWII, the average life expectancy for a 'green" US fighter pilot was 5 combat missions. For those who made it past the 5th mission, life expectency increased exponentially. Those 5 flights were the experiance a green pilot could not receive in training or mock ACM. The US learned this rapidly.
From the inferior P40 Warhawks of the "Flying Tigers" which performed amazingly against the superior A6M zero to dealing with the Me Bf109 which could literally fly circles around any allied aircraft, even to the end of the war.

As WWII progressed, American combat aviation philosophy quickly diverged significantly from its enemies as well as the Brits. Where as the germans and japanese placed high value on manuevering performance, (radius of turn) speed and economy, America began to place higher emphasis on durability, power, range and firepower. As the war progressed, the US's planes grew in wieght and size, enabling them to carry heavier armour to protect the pilots, as well as more guns and more fuel. To compensate for increasing wieght more powerfull engines were required and added. This benefited top speed.

There were numerous significant factors to keeping pilots alive. 3 of these (but by no means all) were, in simplified terms:
1)The US knew that by keeping its pilots alive each successive sortie would add to their experiance making them more effective in combat
2) By keeping its pilots alive to the end of thier combat tours, the US could rotate these combat experianced aviators back to stateside training squadrons to provide better training/preparation to student aviators.
3) Pilots could bring their experiances back for tactical analysis. The US could learn from their experiances and develope tactics to counter the enemies tactics and equipment.

This last point was critical to the US's aircraft which could not manuever as agily as the enemies, this being generally considered an inferior trait for combat aircraft. Tactical analysis resulted in nne of the prevelent tactics to come out of WWII: The hit and run tactic--using an aircrafts superior speed to close the enemy, strike, then open and extend beyond the enemies weapons range. This was the the most succesful tactic against the more manueverable axis aircraft. To engage an axis aricraft in a turning fight, relying on lead, lag and pure pursuit curves was a losing tactic. This tactic later came back during the early days of the Viet Nam war when the US kill to loss ratio (4-1 ~ 5-1 depending on which books you read) was deemed unacceptable. The Navy formed its FWS (well known by its "popularized" nickname -TopGun) to train fleet pilots in advanced ACM tactics-- most notablely the hit and run tactic of WWII. This allowed the Navys winged bricks aka F4 Phantoms along with its much more nimble F8 Crusaders to sucessfully engage the much more manueverable Mig 17s and Mig 21s, raising the kill to loss ratio to 11 - 1. It is important to note reports indicate that early on Mig pilots had little fear of engaging F4s, but were far less willing to engage the not so unmanuverable F8s

Oh, and to correct a point on which ABL was mistaken. The F14 and F15 were never in direct competion for any Navy or Airforce contracts. The F 14 (Grumman model 303) was a response to the failed F111 (TFX-Tactical Fighter eXperimental) program, more popularly known as "McNamara's Folly". Then Defense Secratary Bob "Viet Nam was not My Fault" McNamara was convinced one aircraft could be built to fullfill both the AirFarces requirement for a supersonic strike aircraft and the Navys requirement for a Fleet Defense Fighter. The Chairforce was to receive the A varient, while the Navy would receive the B varient. Long story short..the F111B sucked hind tit, and Vice Admiral Thomas F. Connolly testified before congress as such, uttering a cult-fame phrase "There isn't enough thrust in all Christendom to make that airplane a fighter". The F111B program was killed and replaced by the Navy VFX program, which the Grumman 303 won. Trivia: The name Tomcat was given to the F14 for respect of VADM Connolly, whos fleet callsign was "Tomcat"

lmao

If memory serves, a pilot could have his mechanic set the distance that the paths met to suit his style/needs.

site's giving me a dns error but I'll Take you're word for it. I put That chapter of my life away 25 yrs ago. 8O 8O 25 yrs 8O Wow.

Mike

Dat's cause' I fooked up the linky.

It's ok I fixed it.

There aren't that many delta winged craft in the US's arsenal anymore (or so I think, please excuse my unlearnedness, as I am but a n00b), why not? It seems like a more aerodynamically sound concept than the conventional design.

Delta wings offer poor low speed performance (Dog fighting speeds) hence those huge forward canards on that Valkyre to help stabilize the plane at subsonic speeds.

Edit: this is just a guess but the position of the engines on that B-58 and the ability to trim each engine individually would compensate for the decreased stability of that particular delta wing set up.

Dam Ninja,

you dont know what a can of worms this is. I was trying to answer without pictures, but I cant. So, its gonna be a while as I have some drawing to do.

Hey... I at least remember what angle of attack is... I think.

The advent of ICM's also made it unnecessary. For aircraft, I prefer old school
stick and rudder types. No computers and Nintendo pilots. Better stories too.

My grandfather was a flight-test engineer at Kaman. In the 60's in Italy one of
their choppers devoloped a full leak on the way to the Farnborough International
Airshow. He and his partner flew over with the needed parts and fixed it. Non
of them knew Europe very well, and too embarrassed to ask headings and such
to get there, they grabbed an atlas and followed rivers and highways to get there.
That's his story, but me thinks is was more of a joyride. Knowing my grandfather,
he had his legs out the side door at 1500ft with a bottle of Scotch. 8)

(He wasn't a drunk, but liked to "enjoy" his trips to Europe)

He he...Has nothing to do with alignment to take a shot if thats your thinking , unless your at a much higher altitude than your opponent at the time...Thats a very vague hint by the way.

I applaud Turpit for even attempting to explain some of this since it took me years of being spoon fed small bits of info to get to the level of understanding that I'm at.

I can grasp it...But I sure as hell can't explain it.

When I was a kid my next door neighbor was an Air National guard pilot and he & my father were big time into building WWI planes from scratch , just balsa wood stock & fabric...Most 1/32 scale.
But my neighbors brain was the one to pick on things like wing dihedral & principals of aerodynamics , lift & such.
We built a rocket powered (by we I mean He) styrofoam a-7a corsairII that flew great...About 120 yrds under power & almost 200 yrds total , I did get to rough carve the fuselage he did the wings ,stabilizer & finished the fuselage & made an engine housing & exhaust out of a block of Pencil grade graphite. The nose weight was simply a 6-32 piece of threaded rod with a small cluster of nuts adjusted back & forth until the proper weight balance was achieved...Although he did have to make a streamlined "Cap" for the chin intake because it created too much drag.

I'm Suprised R.C. hasn't joined this thread...How Can you have a Nic like R.C. Pilot & not have an itch to talk about planes.

Edit: for dodgy BB code[/Tomsmart]

Theres the key , at Mach+. 8) Thats where a delta's performance is recognized...The problems are in the 600 mph - supersonic speed range where the air moving over top of the wing approaches or exceeds the speed of sound before the aircraft does...It gets major stability problems and lift loss and all kinds of nasty sh[b][/b]it can happen.

Its because of this phenomenon that they thought there was a speed barrier "Wall" at the speed of sound.

Here it is, as short as I can. This is in no way all inclusive, I’m leaving out a huge amount of info. When I got to 10 pages of text in Word, I decided to start cutting it down. But I think I can get a concept across that will make it understandable.

I don’t know how much you know about aerodynamics but I suspect you have the basics, if for no other reason than from playing with your cars. Since I can’t be sure, I will reference this from ground zero and simplify as much as I can.

First, before we even start, you may want to understand how lift really works. I’m not going into it here, but most if not all of what you may have learned is probably inaccurate. Most lift explanations are extensions of Bernoulli’s Theorem which is easy to understand, but not wholy correct.

For an accurate explanation, along with debunking of Bernoulli Lift, Newtonian Lift and spatial lift, you can go to NASA's public site, here:

NASA Presents: What is Lift.


Some terms I may or may not reference

Longitudinal Axis (pitch axis): the axis from the front of the plane to the tail
Lateral Axis (roll axis): the axis horizontally perpendicular to the longitudinal axis
Yaw axis: the axis vertically perpendicular to the longitudinal axis
Airfoil: That which produces lift!
Camber: the curve of the surface of the airfoil
Wingspan: the lateral distance from one wing tip to the other
Leading Edge (LE): the forward most edge of a wing as referenced longitudinally
Trailing Edge (TE): the aft most edge of the wing as referenced longitudinally
Chord: the longitudinal distance or mean distance (span wise) from the LE to the TE
Thrust line: the axis of thrust generated by the propeller or turbine
Angle of Incidence (AI): the angle between the chord (referenced longitudinally) and the longitudinal axis
Aspect Ratio (AR): The ratio of wingspan to mean chord line
Airspeed (AS): the speed at which the object itself moves through the air
Relative air flow: the vector of air relative to the aircraft as it moves through it.
Angle of Attack (AOA): The angle of the chord line (referenced longitudinally) as referenced to relative air flow
Span wise flow: Flow of air laterally across the wing.
Fence: An aerodynamic device used to straighten airflow over a surface. I.e. correct span wise flow.
Center of Gravity (CG): the point on the body at which gravity acts
Aerodynamic Center (AC): the point on the airfoil at which the generated lift effectively acts
Center of Pressure (CP): the actual sum of lift generated by the wing. Moves with changes in AOA, based on airfoil camber. Acts through the AC
Lift: The force generated by turning a moving fluid.
Induced Drag: Drag resulting from the production of lift. Decreases with increases in AS due to decrease in AOA
Parasite Drag: Drag from antenna, rivets, landing gear, fences etc. Increases as AS increases.
Wave Drag: Drag at the point of occurrence of localized supersonic shockwaves. Caused by the increased velocity at high subsonic speeds when specific areas of airflow over a surface may exceed the speed of sound.
Laminar airflow: the smooth undisrupted flow of air layers over a surface.
Stall: Turbulent airflow. The opposite of laminar airflow. Results in loss of lift.
Stall speed: the speed below which AOA has increased to the point that laminar airflow cannot be maintained
Accelerated Stall: Monetary stall resulting from a rapid excessive increase in AOA.
Flaps: Lift increasing devices located at the training edge of the wing. Function by increasing the camber of the wing
Slats: Lift increasing devices located at the leading edge of the wing. Dual function. 1) Increases the camber of the wing. 2) “Droops” the LE allowing the wing to maintain laminar airflow at higher AOA’s
Wing Loading = Total aircraft weight distributed over total wing surface area

The above list is in no way all inclusive. I tried to simplify the definitions as much as I could, so some of them leave a little to be desired.

The easiest way I can think to answer your question, without spending the next 4 years of my life doing so is to relate it to Aspect Ratio(AR) Please note, this is a super simplified answer, it is not wholy true and does not cover anywhere near 100% of the factors involved.

Aspect ratio, as noted, is the ratio of wing span (tip to tip) to mean chord length
The chord as noted is the distance from the leading edge (LE) of the wing to the trailing edge (TE) of the wing. In swept, tapered, elliptical or delta wings, the ratio is more easily expressed by wingspan (squared) to area

Some AR examples are:

Generic glider = 20+:1
Straight wings
A 10 = 6.54:1
Cessna 172 = 7.32:1
Swept wing aircraft
F 86 = 4.78:1
F8 = 3.42:1
Boeing 707 = 7.1:1
Boeing 737 = (100)8.83:1 (400)9.16:1 (700ER)9.45:1
Boeing 747-100 = 7.0:1
WWII Fighters
P47 = 5.61:1
P40 = 5.89:1
P51= 5.58:1
F 4 Corsair = 5.33:1
Modern fighters
F4 Phantom = 2.77:1 (arguable whether this aircraft was delta wing or tapered)
F16 = 3.09:1
F15 = 3.01:1
F18 = 3.52:1
Conventional Delta wing fighters
A4 Skyhawk = 2.91:1 (OK, OK, it’s an attack plane, not a fighter, and not a true delta, but close enough)
MiG 21= 2.2:1
Tailless Delta wings
B58=2.09:1
F106 = 2.1:1
Concorde = 1.85:1
Canard Deltas
EF2000 = 2.4:1
Viggen 2.45:1
Grippen 2.76:1
Kfir 1.86:1


“Aberrations” to conventional AR philosophy
F104 = 2.45:1 (nicknamed “the manned missile”, this plane was fast as lightning, but could not turn)
X15 = 2.5:1

Variable Geometry or “swing” wings (variable sweep results not only in variable LE sweep, but variable AR as well)
Panavia Tornado = 7.73:1 @ full extension, 2.96:1 fully swept
F14 = 6.95:1 @ full fwd position, 2.85:1 at full “flight” sweep (the wings swept further for carrier storage)

What’s the big deal about aspect ratio? In relation to a supersonic fighter: Speed. Maneuverability. Lift. There are soooo many variables related to those. Speed and maneuverability optimization depending on LE profile, TE profile, wing thickness, LE sweep, camber, taper, wing span, twist, control surfaces, lift increasing devices, structural strength, relation of CG to AC, shifting CG from fuel burn, shifting AC at supersonic speeds, strenth of materials, yada, yada yada. What you want to know goes very deep. People have been working on these problems since WWI, when they first realized airplanes could be used as weapons. We still dont have it all figured out

Note AR exapmles above, typical current conventional fighter aircraft have aspect ratios of 3~4:1 Delta wings commonly have lower aspect ratios of 2~3:1, while commercial aircraft go 7~9:1. Gliders have the highest aspect ratios- 20:1 and higher.

The most efficient wing for producing lift is a simple straight wing, regardless of Aspect Ratio. Great maneuverability, but not real good for going very fast and have some “handling” issues. The best wing for going fast is a delta wing. Deltas are not nearly as efficient for producing lift as a straight wing though, and not great for maneuverability. The absolute most efficient lift producing aircraft is a “flying wing” but unstable and not super fast. The few of these built tend towards higher aspect ratios, though the A12 (had the prototype been finished) would have had a low AR. The absolute fastest lift producing aircraft (miniumum drag) is a lifting body, but super unstable. Lifting bodies have super low aspect ratios.



Seeing the trend? The lower the aspect ratio, the faster the plane. Higher aspect ratios = slower. So why not a delta winged F 15? Maneuverability. Fighters need to turn. As noted in another post, WWII saw the development of the hit and run tactic. Viet Nam saw its re-emergence. So why do fighters need to turn, why can’t they just hit and run all the time? Simple. The reality of experience. A long time ago when guided missiles came along, our tactical analysts in their infinite wisdom decided that planes didn’t need guns anymore because they believed engagements would be concluded long before combatants closed to gun range. Combat experience taught pilots differently. The pilots told the analysts to go stuff themselves and had the engineers put guns back in the planes. OK, so what about the hit and run tactic? The hit and run tactic is great, but what happens if you don’t hit? Well, you extend for another run. But what if while you are extending, the guy you were chasing decides to chase you? If he has missiles, you can’t run fast enough. If he doesn’t, you may have to run a long time (depending how fast his plane is) to open enough distance to be able to turn back for another run. There’s a whole lot more to it than that, but that’s close enough for our purposes. So why not just build a plane that can go fast AND turn tight? Simple - You can’t have it all. You have to prioritize your needs and compromise. You can’t build a plane that’s faster AND turns tighter than anything else. So how about a plane that can turn tight and is reasonably fast or a very fast plane that can turn reasonably tight? That’s a little more doable.

So what effects radius of turn aka maneuverability? Excess lift. The more excess lift your plane can develop, the more maneuverable the aircraft. Simple! And that’s where the simplicity ends.

Let’s say you want to pull a 9 G turn in an 8500 lb aircraft. The engine produces 8500lb of thrust. 1:1 thrust to wieght ratio. A good thing to have in a combat aircraft. The centripetal acceleration at 9Gs is going to result in an aircraft “weight” of 76500 lbs. Before we can pull our turn, our wings have to be structurally capable of handling that kind of strain. Try to pull a 9G turn in a Cessna 172 or Boeing 737 and the wings wave “by by” to the fuselage. The structural strength to handle high accelerations incurs increased structural weight. So we strengthen the wings and our plane now weighs 9500 lbs. In our 9 G turn, it “weighs” 85500 lbs.

Our wings can now handle the stress of a 9 G turn, but can they produce 85500lbs of lift?
If not, we’ll never get to 9Gs. In level flight we need 9500lbs of lift. 9.5K to 76.5K is a big leap in lift production. A 9 G turn will require a much greater AOA than level flight. But if our AOA is too high we will experience an accelerated stall. No more laminar airflow = no more lift= no more turn. A nice big gently rounded leading edge design can help solve that problem, but it will result in a thick wing. A thick wing will also help to keep the AOA down and generate plenty of lift, but is not conducive to high speed flight. How can we keep the wing thin for speed but still achieve a 9G turn? Part of that is camber. There’s some trickery we can do, but I’m not going into that. Something else we can do in addition to camber trickery is to add slats to the leading edges. By drooping the slats at high AOAs, the LE AOA is lowered presenting a favorable profile to relative airflow while the overall AOA for wing remains high, allowing us to generate more lift. Nice solution, but it adds complexity, cost and weight to out aircraft. Like I said, you can’t have it all. Our 8500 lb aircraft can now successfully pull a 9 G turn, but now it weighs 10000 lbs and the 9 G turn is 90000 lbs. Our little 8500 lb thrust engine now has to push an “extra” 13500lbs in our turn, and we lost our 1:1 thrust to wieght ratio. Time for a bigger engine. This adds even more weight, increases fuel consumption which decreases range and total load, etc etc etc. See the way this is going?





The Need for Speed: the problems of supersonic flight. (I’m not going to discuss transonic in depth)

Problem #1: Shockwaves. Sound cannot travel faster than……the speed of sound.
Sound is a mechanical vibration. The speed at which sound travels depends on the medium through which it travels. For air that speed varies due to temperature, pressure, moisture content, etc. Assuming a homogenous medium, sound will radiate outwards from its source as uniform spherical “waves”.
As an object travels faster, sound waves produced by the object begin to compress in the direction it is traveling. To a stationary “listener”, the result is the Doppler Effect. (I’m sure you know what Doppler is, if you don’t, look it up) The faster the object goes, the greater the compression of the waves. To put it as simply as I can, when an object exceeds the speed of sound, the waves can no longer radiate beyond the source. As a result, they converge along a ‘cone’ defined by the max speed of sound for the medium through which they are traveling. This concentration of sound waves along that front, or ‘cone’ greatly amplifies the magnitude of the force generated creating a highly localized shockwave, or pressure front. This can impinge upon the wing. BAD



Problem #2: Compressibility
One oversimplified version of lift (and incorrect) is Bernoulli's equation. But for our purposes it’s good to illustrate a point. In subsonic flow:
P(total) = P1 + P2 = (P(static)+½(D V1(sq)))+(P(static)+ ½(D V2(sq))
When you break down Density to its root (pressure / gas constant x temperature)
and mix it in, what it tells us is that pressure is inversely proportional to velocity.
The faster you push an airfoil through the air, the lower the pressure over the camber. Again, this is not wholly accurate, but it’s close enough and helps illustrate the problem.
At supersonic speeds, this reverses. The faster you go, the higher the pressure. (Its how we get compression lift for our XB 70) It also causes the AC to move backwards along the chord, going from 25% chord to 50% chord. This causes stability and controllability problems by shifting the AC away from the CG. As you increase the distance between AC and CG, you increase AC’s moment arm. This results in greater torque at the CG, requiring a proportionally higher counter-force from the horizontal stabilizer. If you increase the moment arm too much, your stabilizers or control surfaces will be “overpowered” or unable to exert sufficient force to maintain control of the aircraft.

Problem #3: Wave Drag
Remember how we produce lift? By increasing velocity to decrease pressure (not really, but for our purposes, it works). So what happens when we start getting fast? Airflow over the wings and fuselage is not uniform. In some areas it’s faster than others. You can actually achieve supersonic flow on localized portions of an airframe while other remain trans or subsonic. This causes localized shockwaves which result in localized increases in drag, as well as localized areas of compressibility. BAD. This can cause control reversal and loss of control effectiveness and all manner of bad stuff. Very bad especially in a medium/ medium high AR straight wing aircraft.

Many of the faster WWII aircraft were capable of approaching supersonic flight (transonic flight) in steep dives. They tended not survive the experience. The problems were those noted above. The shockwave would impinge upon the wing, and along with compressibility and wave drag cause all manner of problems: In addition to control reversing and loss of control effectiveness, extreme buffeting, incredibly high localized pressures etc could also occur.

We know what we need to do for maneuverability: maintain laminar airflow at high AOAs. But how do we solve the problems of super sonic flight?

A very easy solution to the problem of the shockwave impinging on the wing is to move the wing back along the fuselage, behind the shockwave. The problem with that is the center of gravity. Current axial flow turbine engines are placed aft in the fuselages of fighters pulling the CG aft., helping to partially alleviate that problem, but we still have to deal with compressibility and wave drag. We have to flatten the wing a bit and get the aspect ratio down to solve these problems though. This means stretching the wing chord wise We can do that, but no matter how much we fiddle, the big straight wing is not good for high speed flight..

Another solution is to “sweep” the wings back. Pulls the wing out of the shockwave, but reduces AR depending how much you sweep them. The more you sweep, the more the AR decreases. Highly swept wings also place the AC behind the wing root resulting in torsional stress on the wings. Swept wings are also susceptible to span wise flow resulting in wingtip stall at high AOA=very very bad. But these are all solvable problems. It will add weight and drag, but we can fix them. What we can’t fix is that swept wings are susceptible to control surface issues resulting from compressibility and wave drag. We either have to stay subsonic or stretch the wings chord a bit.

Another possible solution is to shorten the wings to the point they do not extend into the shockwave. Short stubby wings like the F104 or X15 solve the problem of shockwave impingement, but do not provide a lot of lateral stability. Additionally, at supersonic speeds, that old compressibility bugaboo rears its ugly little head. To compensate for the AC moving aft from the 25% chord position to the 50% chord position we are going to have to stretch the wing. We discussed that in passing already. It matters little, because this is not the solution we are looking for. Like the low AR delta wing, stub wings are great for speed, but aren’t great for maneuverability.

How about those deltas? Great for speed. Also solves the problem of torsional stress since the AC is on the root chord vs. behind it. Carries more fuel than a swept wing too, but not as efficient at producing lift. Still susceptible to span wise flow but this helps as well as hurts. Due to the high sweep of the wing, the delta has a neat little backwards effect where airflow delaminating at the root spirals span wise down the LE keeping airflow attached at high AOAs. This allows the delta to achieve high AOA, but doesn’t benefit maneuverability as much due to of loss lift at the tips and root resulting in low net lift gains. At the same time induced drag increases. The end result is you can “pop” the nose of a delta wing and whip it around a bit, but the plane will “squat” (significant divergence of direction of travel and direction the nose is pointing) and slows dramatically from the increases in induced drag. Not real good overall for maneuverability. But if you need to get from point A to point B, the only design that will get you there faster is a lifting body. Still though, not the compromise we are looking for.
There are some other things we can do to a delta to improve its maneuverability. Canards are one thing, but they come with a price. That price is increased drag and some nasty stall characteristics if both the canards and wing are stalled. Aircraft such as the Eurofighter Typhoon (EF2000), IAI Kfir (An Israeli modified Dassault Mirage) Saab Gripen and Saab Viggen are canard deltas. Another is fences to keep airflow straight, but as mentioned, they come at the cost of drag, not to mention, they also make excellent radar reflectors! You can use a “cranked arrow” plan form such as the Avro Vulcan or F 16 AFTI experimental demonstrator. An excellent wing design for solving a lot of the deltas problems, it’s just not that maneuverable. The “double” delta, such as used by the Viggen is another adaptation, but still not so great for maneuvering. Yet another approach is the “dogtooth” wing, as used by MiG 19, MiG 21, and the ill-fated Avro Arrow.



To sum up quickly:
High AR Straight wings: Great maneuverability, poor high speed characteristics, and with a little twist and taper, great low speed characteristics
Medium AR Swept wings: Good maneuverability, good high (sub/trans sonic) speed characteristics. Some solvable low speed/high AOA/structural problems, some solvable supersonic problems
Low AR Delta wings: Poor to Fair maneuverability, Great high speed characteristics, some low speed/high AOA issues
Low AR Stub wings: Poor maneuverability, inherently poor lateral stability Great high speed characteristics after solving a few problems

None of the above gets us what we what without compromise and sacrifice. Can we minimize the compromises and sacrifices? Yes. What is it we want? The speed benefits of the delta and the maneuvering of the high AR straight wing. What if we took the straight wing, and combined it with the delta? What we arrive at is the asymmetric tapered wing with a medium low AR, and a less aggressive LE sweep. Like the F16 and F15. A trade off. Not as fast (for a given thrust) as a delta but more maneuverable. Not as maneuverable as a straight wing, but a whole bunch faster. No significant structural issues, No shock wave impingement, and wave drag/compressibility problems as they impact controllability are mitigated. We still have some span wise flow, but the depth of the tapered wing alleviates to low speed high AOA problems sufficiently.


But wait, there’s more!!!
Yet another factor is wing loading and its affect on stability. Aircraft like the F104 have very small wing areas. This results in high wing loading. Although the short, small wings of the F 104 are bad for lateral stability, their high wing loading provides a more stable ride in turbulent air. That could come in handy when trying to aim your plane at another for a gun shot. The down sides are structural stress and maneuverability.

The supercritical wing. The super critical airfoil is a deviation from typical airfoil design. It is designed to function at supersonic speed and minimize or eliminate. I’m not going into depth on it because I’m sick of typing this, but I will say it solves/minimizes many problems with supersonic flight, and because it is an airfoil profile, it can be applied to any plan form, though is doesn’t solve problems of LE sweep.

But wait, there’s still 3 1/2 more years of crap to go through! Literally, but I’m not going there. This is more than enough for a free lesson. If you want to know more, you can seek admission to the school where I instruct.

So, skipping the next 3 1/2 years of remaining explanation, compromise is the answer to your question. Deltas go fast, but don’t give us the maneuvering capabilities we want. Straight wings give us our maneuverability, but don’t go fast. Thats as simplified as I can make it.

Oh. It makes sense now. ^_^