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Elevons

Pips

Pips

Charter Member
Was performing a walk around of my beloved Mirage III prior to a flight when I got to thinking about elevons.

I can't say that I notice any real difference between flying delta wing aircraft (in FSX) as opposed to swept wing aircraft. Although I do suspect that the delta's do not react as quickly in pitch and roll as swept wing aircraft. But then again that may simply be more related to the Mirage itself, as it is slightly quirky in flight.

In real life just how effective are they? It's a limit of the delta design that aircraft so equipped have to use elevons. I would think that a control surface that has to perform both pitch and roll is not as effective (in either plane) as an aircraft with separate control surfaces.

Am I right? Thoughts?

And just taking it a bit further, which angle is first actuated? For example in straight forward climb or roll, the elevon would (I suppose) perform as per an elevator or aileron. But what happens in a combined flight manoeuvre like a climbing turn such as a chandelle? Does the elevon first pitch, then roll? Or is it related to the pilots first stick movement ie if he brings the stick back before rolling, or visa versa?
 
Well, I never laid hands on a Mirage per se, BUT: I did work on the Kfir for a few years, and it's essentially a Mirage with a J-79 engine, and a few modifications. Israeli bird. In Yuma Az. Go figure. Still, same basic wing, and control surfaces as a Mirage. There is no "first" of the control movements, any more than in an "regular" aircraft. If the pilot pulls up and right, for example, the controls make the correct motions. No axis is first though. There is a complicated, but not overly complex, geometrical set of rods and bell cranks that move the surfaces according to the pilot's requirements. If he pulls up and right, the elevons both deflect upward, but the one on the right deflects farther than the left. I think. But you see the basic Idea. You need to pitch and roll at the same time, the elevons deflect accordingly, just as the elevators AND the ailerons do on a regular aircraft. If he needs greater roll during the pitching, one elevon will even deflect downwards slightly, while the other deflects up, but not as far.
It was fascinating, during our training on the aircraft, to see someone deflect the stick in a certain manner, and see what the elevons did. I may still have my training manual around someplace, and if I do, I'll upload a picture of how the push-rods, and bellcranks were arranged. It's really quite ingenius, especially for the time. Now, I'd wager they're all fly-by-wire, and thus computer conter controlled, but in my day, the Kfir was strictly mechanically controlled. Hydraulically assisted, yes, but there was a direct connection between the stick, and the elevons. It did have a Stab-aug system, but it frequently disabled it's self during abrupt maneuvers, with no performance degradation.
Anyway, don't think of which axis is "first". There isn't one.

Does that help at all?
Pat☺
 
Interesting question and answer.

Are there any spoilerons involved, or are the elevons the only control surfaces on the Mirage and Kfir?

The USN and Marines used the Kfir in the Aggressor role, right?

Cheers,
 
Neat question. The Delta actually provides some substantial advantages over the swept wing. Especially in the transonic region. But, like anything in aircraft design, configuration is all about give and take. Like money, spending money in one area usually leaves you deficient in another, for any number of reasons. However all things being equal, I don't think the question is. Asking the question from the perspective of stabilized, what might be considered "normal" flight envelope, where ailerons induce roll moments, elevators prduce pitching moments, and rudder produce yawing moments may not be as logical is first thought. Especially on the modern day deltas which use fly-by-wire coupled with Canards. If the design incorporates neutral to negative stability then comparing control surface effectiveness of one airplane to the next is not 1:1 comparison. What might produce full authority for one aircraft in a specific design may not provide much at all to another design. Things like CG, CL, and moment arms can greatly affect the ability to control the aircraft.The mirages appear to have a very short moment arm, so at first glance I'd say they would have very good reaction to any inputs. But being a delta would induce a lot of drag with the addional excess lift, causing the loss of airspeed in say a turn. Needing excess thrust or altitude to compensate.

I'd like to hear more about those Kfirs! Sounds super interesting!
 
Never tried the Mirage or Kfir, but the F4D Skyray (aka: Ford) is a long time favorite and about the newest aircraft I care to fly. The Northrup XB-35/RB-49 flying wing bombers also used elevons as did the Horton Ho 229.
 
The Marine Corps got the Kfirs in late '87. Righ after I got out, they stood up. I'm a plank owner. I got into the training just as it started, a weekend after I left Beaufort. Kinda nice, being on Terminal Leave for 2 months, drawing a paycheck from the Corps and '401 both. The squadron was VMFAT-401, the Snipers. All Russian stuff to encourage the thought patterns in the Pilots. The big SNIPERS in the hallway where all the offices were was in Cyrillic, stuff like that. They acted as agressors for whoever needed them. Especially during WTI. Weapons & Tactics Instruction course the Corps holds every year. We put in some flight time during WTI, let me tell you. It's great plane for the role, simulating several other aircraft's flight envelopes. Thankfully, Yuma has a LONG runway. Those things land fast. They even had a couple birds cleaned up, made as slick as they could get, waxed and everything, and simulated cruise missiles. Flew very close formation, CLOSE formation, then were "dropped" and flew a flight course and envelope of a cruise missile. Had to keep it short. Those J-79's drink gas fast, and there's not a lot on-board.
Of course, Israel isn't that big a country. They had to take-off, and make a sharp turn to stay in-country, when at their home base.
Unfortunately, the love affair didn't last but about 3 years or so. The Israeli managers were very arrogant, and the Americans just couldn't understand their way of settling arguments. They get all involved, and many not usually, in a big group, and yell at each other until things are ironed out. Sounds sometimes like they're going to kill each other, arms waving, all talking at once, the whole thing, but that's just their way. Americans couldn't quite get on-board with that. So they took their planes back, and went home.

Are there any spoilerons involved, or are the elevons the only control surfaces on the Mirage and Kfir?

The USN and Marines used the Kfir in the Aggressor role, right?
Click to expand...

Nope, no spoilerons. Not on he Kfir. The elevons were split into 3 sections (maybe 4, but I'm pretty sure 3), each wing, and they would move in sequence, with the innermost first, depending on the control input. The farther the stick was deflected, the more sections moved. Like for example, when it was just the little movements, like during formation or regular cruise, just the innermost sections (closest to the fuselage, each side) would move. For middle sized stick deflections, like entering a pattern, and so on, the first AND second sections, and so on. The Stab-Aug did the same, small motions, mostly involving the innermost section. Of course, what moved and how far, depended on what was required for a particular motion of the aircraft. Snap roll, all 3 sections on each side would deflect in opposite directions. Sudden pitch up, same direction. See the pattern? Also, if the stick was deflected far enough, fast enough, like during ACM, the Stab-Aug would kick off. There were 3 large buttons in the cockpit, lower left of the control panel, for the Stab-Aug. Pitch, Roll, Yaw. So the pilot could easily re-engage the Stab-Aug after the sudden, sharp maneuvers were over.
Having gone through all that, there were speed brakes on each wing, top and bottom, right about 1/2 way back from the joint with the fuselage at the leading edge, and 1/2 way out from the fuselage to the wingtip. Hard to describe the 'middle" of a triangle, sorry. Open and closed by the pilot. Just a 2'X3' (roughly, it's been a long time), rectangle of wing surface that would open up, all the way to vertical. Actuated very rapidly. They used them to bleed off the hyd pressure after engine shutdown too. It would open them about 1/2 way. Just don't be on or under one when they do! But they were strictly speed brakes, not a "control surface" to speak of. No connection to the elevons or rudder, no way to use differential deflection of them to enhance pitch or roll. They always opened the same distance, top and bottom, left and right.
There were canards near the front of the intakes for the engine, top of the intakes, but they were fixed. No movement at all. Hopefully, anyway :D

Hope that all helps a little...
Pat☺
 
I saw one of ATAC's Kfir's up close at SJAFB about a decade ago. Here's the photos from my encounter:
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PhantomTweak said:
Nope, no spoilerons. Not on he Kfir. The elevons were split into 3 sections (maybe 4, but I'm pretty sure 3), each wing, and they would move in sequence, with the innermost first, depending on the control input. The farther the stick was deflected, the more sections moved. Like for example, when it was just the little movements, like during formation or regular cruise, just the innermost sections (closest to the fuselage, each side) would move. For middle sized stick deflections, like entering a pattern, and so on, the first AND second sections, and so on. The Stab-Aug did the same, small motions, mostly involving the innermost section. Of course, what moved and how far, depended on what was required for a particular motion of the aircraft. Snap roll, all 3 sections on each side would deflect in opposite directions. Sudden pitch up, same direction. See the pattern? Also, if the stick was deflected far enough, fast enough, like during ACM, the Stab-Aug would kick off. There were 3 large buttons in the cockpit, lower left of the control panel, for the Stab-Aug. Pitch, Roll, Yaw. So the pilot could easily re-engage the Stab-Aug after the sudden, sharp maneuvers were over.

Hope that all helps a little...
Pat☺
Click to expand...

Wonderful explanation Pat, many thanks.

I had in mind that the elevon was simply one unit, not broken up into several as you mention. Which is why I couldn't picture how it could perform both pitch and roll at the same time, without decreasing the effectiveness in one plane or the other.

But being made up of several separate components, all moving individually depending on the level of input makes clear sense.

So to the second part of my question. Is the elevon (in the older jets like the Mirage III) able to provide as much control deflection as dedicated ailerons and elevators on equivalent fighters like the F-100, A-4 Skyhawk, MiG-21 or F-4 Phantom?
 
That sure looks like what our Kfirs look like. That's a Martin-Baker ejection seat.
A friend of mine rode one once. Went a couple hundred feet up, then fell, bounced off the fuselage, then the wing, then didn't bounce on the ground. Came within a gnat's whisker of killing him. It was lucky for him Crash Crew was the next hangar down the flight-line, or he'd have been gone. He was standing on the seat, facing backward, arming the main gun (mortar that kicks the seat up out of the plane) after the plane had been brought out to the flight-line after a Phase inspection, during which, for safety and time inspection, the seat had been removed and replaced. Doing so required pulling the "trigger", an upside down U shaped piece, with a roller at the apex of the inverted U shape, up against spring pressure, and inserting a triangular shaped piece of aluminum (I believe), which is pulled out by pulling the face curtain or lower handle. When it's withdrawn, it pulls the trigger piece up, then is pulled out, allowing the trigger piece to slam down, setting off the main gun. He slipped, releasing the trigger before he got the triangular piece in, and setting off the main gun. the rest, I already told. Needless to say, that was his last day working there, or at all. Aside from nearly killing him, it removed a large percentage of his lower jaw, broke arms and legs, and several ribs, along with his back. He did learn to both walk and talk again after several years, though.
He was a 30 year Marine seat shop veteran, and a guy I drank with sometimes when I was in. Older, gruff, seemingly grouchy, curmudgeonly type, but a good guy overall. Martin-Baker did send him the pin and tie, I understand.
Sorry, bad memories seem the clearest...

Is the elevon (in the older jets like the Mirage III) able to provide as much control deflection as dedicated ailerons and elevators on equivalent fighters like the F-100, A-4 Skyhawk, MiG-21 or F-4 Phantom?
Click to expand...
Well, our Kfirs managed to fight to a standstill F-4's, F-5's, F-14's and most others they were sent against, so i would say they had as good or better control authority than all the others.
Although we had one pilot return from a flight in worse shape than usual after a fight with a couple F-14's. Normally, they would be sweaty, dehydrated, and tired, but this guy, Orca was his call-sign, was in really bad shape. Flight suit soaked like he'd just gotten thrown in a pool, sweat still rolling down his head and face, guzzeling water like it was going out of style. All he said was "Never, ever get slow with a '14!!"
Remember, the Kfir's landing speed was around 200 kts, iirc. Very high stall speed, unlike a Tomcat. And the Tomcat crew can "trick" opponents by holding the wings back, even when they have much less energy than they would if the wings were allowed to sweep automatically. When the opponent over-flies them, THEN they allow the wings to do what they need to, and can maneuver very tightly. dirty trick, indeed.

Those pictures of the cockpit are real familiar, too, although we didn't have that large electronic screen in the upper center. Other than that, I could probably tell you what most, if not all, of the switches do, and what to do for a Daily inspection, a Turn-around, and so on. Brings back memories. I would be VERY careful about making certain the 7 pins were in the seat, looking to see each and every one was in the correct position. I wouldn't even come any higher up the ladder than needed to verify the pins, and until I had I made sure I leaned back, with both hands on the ladder, never on the plane. I'm a chicken. Besides, I saw way too many stains on VMFAT-101's, and VMFA-333's, hangar roofs. The inside of the roof. After my friend, Don Henderson, took his short flight, I got even more chicken, oddly.
I would never, EVER, enter the cockpit, unless the seat had been removed. They had a wooden adapter seat they would install when the regular M-B seat was out, like when it was in the hangar for inspections, people could sit in to do whatever work in the cockpit was required. If you look at the pictures of the side of the seat, there's a pin that's in the top-center, behind the Face-Curtain handle, and JUST forward the drogue chute pack. That set of folded over flaps you can see atop the seat. That's the pin for the main gun trigger. Can't be pulled when it's in.

The picture of the inside of the tail-pipe brought back a memory. We took the planes to high-power for a run, after engine work, and I got elected to walk the wing a few times. Even when it's in AB, which is an amazing feeling, standing beside the plane at the rear, in and of it's self, you can actually slide your fingers into the tail pipe, as long as you keep them flat to the metal of it. You sort of make your fingers into an upside down L, and slide them on in. Scary as hell, but very exhilarating to actually have your fingers that close to that much flame, but feeling no heat. It's called Laminar Airflow. The J-79 ducts some of the compressor air into the tail pipe to keep the exhaust, including the AB flame, off the metal. Keeps it off your fingers, too, thankfully. We were shown the trick by the lead Plane Captain, an Israeli. And the feeling of the AB...it's a rumbling that your whole body feels. Odd as heck.

Just as a side note, those black "MiG's" in Topgun were F-5's, Not Kfirs. The Corps didn't have any, when Topgun was filmed, although we got them very shortly after it was released.

Something the Israeli's DID bring with that stayed, and spread rapidly to most of the Marine Corps Air Stations, was the Shelter out on the flight-line. The off-white, wall-less stand-alone roof looking thing that's everywhere now. They brought a set to Yuma for '401, and they were so incredibly beneficial, they spread like wild-fire to other bases. My friend wasn't under one, thankfully, when he went to arm #12's (iirc) seat. That would have killed him, no question. The shelters made it so the planes didn't remove skin if touched during the day with bare hands. Without them, the planes got so hot, one touch would mean second degree burns, at least.

Sorry, gang, I reminisce too much...
Pat☺
 
hairyspin said:
No apology needed Pat, you don't get that sort of info touring museums.
Click to expand...

Too true. Fascinating stuff Pat. Thanks for all the info.

I kind of had an idea about the control authority of the Mirage and aircraft with elevons, as I've been flying one flat out in DCS World lately, but I sure am glad to hear your explanations.

Anyone reading this thread has learned more than one thing today.

Thanks for all the photos too Storm. Great pics!

Cheers,

Scott
 
PhantomTweak said:
The Marine Corps got the Kfirs in late '87. Righ after I got out, they stood up. I'm a plank owner. I got into the training just as it started, a weekend after I left Beaufort. Kinda nice, being on Terminal Leave for 2 months, drawing a paycheck from the Corps and '401 both. The squadron was VMFAT-401, the Snipers. All Russian stuff to encourage the thought patterns in the Pilots. The big SNIPERS in the hallway where all the offices were was in Cyrillic, stuff like that. They acted as agressors for whoever needed them. Especially during WTI. Weapons & Tactics Instruction course the Corps holds every year.
Click to expand...

Sounds like the squid version of the 64th and 65th squadron.

For peak russian outside the Soviet Union, there was nothing better than the 4477th though. Real MiGs, even featuring some Navy and one or two Marine drivers. Hard to come by for exposure though since they were just so damn busy.
 
My coworker-- an aero engineer in Super Hornet program, weighedin"...Youso need to make some pretty severe assumptions. Delta wings are almost exclusively used for super-sonic aircraft where swept wings are used for purely subsonic. So a swept wing airplane at supersonic speed is probably a lawn dart, and makes the question a problem. Then you're only comparing subsonically. And subsonically we already know that the delta wing is used because the supersonic airfoil won't provide lift at slow speeds, so it uses the vortices off the delta wing to create the subsonic lift.So you're comparing a severely disadvantaged delta wing with a subsonic wing that is at it's peak efficiency.So, I think it's a pretty unfair comparison. Then you have to take into account the roll and pitch inertia of the airplane which is another comparison that causes problems.Overall though, thinking through the inertia part and the aerodynamic part, I would bet that the swept wing produces a larger rolling rate than the delta wing. Pitch rate is dependent on so many other things that get compromised in design, that I don't think you could compare the two wing types at all.But, with modern flight controls you could make a fly-by-wire system that makes the airplanes artificially fly exactly the same... so does it really matter?That last comment is my snottiness coming through... :p ".So I think it's fair to say that the mirage is a great design and good example of one that works. But not all Delta's could be lumped in together on this.This is a great thread!!! Thanks for all the info guys!!
 
Am glad I asked the question. The knowledge displayed here is fascinating, and enlightening. :)
And I could listen to those stories of yours Pat all day! :encouragement:
 
I'm here a day late as usual. PhantomTweak described the Mirage III/5/Kfir/Cheetah (same basic Dassault designed wing) control surface movement accurately.
Amazing what they engineered back in the day. And yes, there are three sections. Thanks also for the extra information on US Navy/USMC Kfir C1 (F-21A)
operations (reminisce all day, Pat) and the later ATAC version images. Always interesting to see how different users equip the cockpit.
:ernaehrung004:
 
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