Can the Eurofighter fly w/o canards?

By: djcross - 7th February 2011 at 13:29 Permalink - Edited 1st January 1970 at 01:00

Traditional canard design for stability and control places the CG between the center of lift (CL) for the wing and canard. This makes the canard statically stable with the forward and aft wings producing up forces. NASA tutorial

By removing the canard without adjusting the CG, the trim forces are unbalanced. If the CG is too far from the wing's CL, there probably isn't enough control authority in the elevons to produce a balancing force.

By: obligatory - 7th February 2011 at 13:49 Permalink - Edited 1st January 1970 at 01:00

A very substantial flight test program that recently was concluded for both the single as well as the two seat Gripen versions has also fully verified the excellent recovery capability, both in manual test mode and in the normal automatic mode. There exists a requirement in the Gripen project specification for a spin recovery capability, and if this can not be shown, a spin prevention system must not allow a departure to happen. Flight testing has also verified that the EFCS matches this additional demand. Double insurance might be said to exist.
__________________________________________

Delta canard’s inherent good aerodynamics are:

· Stable detached leading edge vortex flow, high maximum lift coefficient.
· Positive trim lift on all lifting surfaces.
· Floating canard offers stable aircraft if EFCS fails.
· Good field performance (take off and landing), enhanced by special aerodynamic breaking mode.

· Battle damage tolerance good, “overlapping” control surfaces.
· Potential for future adaptations, like steep approach, fuselage aiming.
· Low buffeting levels made even better with leading edge flaps.

Spin recovery known to be acceptable for close coupled delta canard (not necessarily so for a long coupled canard configuration)

http://www.mach-flyg.com/utg80/80jas_uc.html

By: Scorpion82 - 7th February 2011 at 14:11 Permalink - Edited 1st January 1970 at 01:00

Gripen and Rafale both offer an analogue back up channel in the case the digital system should fail. The canards are decoupled in this case. The Typhoon lacks such a channel and is probably not flyable without the canards, though I have heared the opposite that removing the canards would make the aircraft stable. There has been definitely no flights without canards and I'm certain no flights with fixed canard positions either. In the Typhoon's case the canards act as primary pitch control surfaces.

By: gubben - 7th February 2011 at 16:32 Permalink - Edited 1st January 1970 at 01:00

Didn't a (South African) Gripen loose a canard in a birdstrike some time ago and flew on just fine?

The FCS is built to be able to compensate for some damages i assume the same or similar way it compensates for asymmetrical loads.

By: arquebus - 7th February 2011 at 17:44 Permalink - Edited 1st January 1970 at 01:00

Traditional canard design for stability and control places the CG between the center of lift (CL) for the wing and canard. This makes the canard statically stable with the forward and aft wings producing up forces. NASA tutorial

By removing the canard without adjusting the CG, the trim forces are unbalanced. If the CG is too far from the wing's CL, there probably isn't enough control authority in the elevons to produce a balancing force.

The information you give is true for conventional canard aircraft, not FBW. Conventional aircraft put the CoG ahead of the CoL so that the a/c will stall properly. A FBW a/c is artificially (electronically) stable and so the CoG can be put directly on the same point as the CoL of the Wing. This greatly reduces the control forces that have to be imparted to change the AoA of the wing and which is why a FBW jet is order of magnitudes more maneuverable than a conventional jet. Now more to the point of the original question:

In case of battle damage: Can the Eurofighter be flown without the canards?

Or: Was it ever tested with fixed or removed canards?

Can any of the Eurocanards?

First of all, when you say "without canards" Im going to assume that means completely removed, because canards stuck in even slightly non-neutral AoA would make the a/c uncontrollable. As far as removed, the answer would be that the delta winged canards like the eurofighter and rafale can because they have delta-wing shape which is inherently stable, where as the gripen could not because it (very unwisely) chose a conventional wing shape that offers no stability. This is why the gripen has had problems with "deep stalls" whereas the eurofighter and rafale has not.

By: Jwcook - 7th February 2011 at 21:25 Permalink - Edited 1st January 1970 at 01:00

The Typhoon can't fly without the Canards (Ok I will concede that it will fly for about 1/50 of a second after they fell off)

This is how it was explained to me by a Typhoon pilot.

The foreplanes are not actually physically connected in any way, but in practical terms they can be thought of as being connected. There are in perfect sync all the time, there is absolutely no asymetry at all generated by them.

The FCS is a marvel, tolerances are incredible and the amount of cross monitoring is staggering.

In a stable aircraft the moving control surfaces are used to make the aircraft manoeuvre. In an unstable aircraft the moving control surfaces are used to "stop" the aircraft from manoeuvring. The center of lift and the center of gravity are such in an unstable aircraft that any disturbance is going to result in a huge divergence. In a C150 or B747 such a disturbance would be naturally damped out.

If you look at any pictures of Typhoon in a hard turn you will see that the foreplane is actually leading edge down (ie against the turn). What has happened is that from the S+L condition the foreplane has briefly "let go" allowing the aircraft to pitch up and has then "caught it" again before the jet has swapped ends.

When you fly Typhoon in a gusty day, you have the stick in the middle (ie no manoeuvre demand) and the foreplane is constantly moving to counteract the gusts, in the cockpit the result is an incredibly smooth ride. The Hawk or Tornado chase is being thrown all over the place!!

So to summarize, Typhoon pitch control comes from a combination of symmetrical foreplanes and trailing edge flaps. Roll and yaw contol come from a very clever combination of differential flaperons and rudder. An even more clever schedule of leading edge slats is used to optimise the lift and trim drag throughout the flight envelope.

The question might be more relevant can the Typhoon fly with only one foreplane? I know there are routines for battle damage written into the FCS, but its a one in a million event that you can blow off a titanium foreplane from the carbon fibre front end without removing the front half of the aircraft.

As the canards move in sync IMHO I would imagine that it may be able to fly with one canard, but it would be a close run thing.

Cheers

By: MSphere - 8th February 2011 at 01:41 Permalink - Edited 1st January 1970 at 01:00

First of all, when you say "without canards" Im going to assume that means completely removed, because canards stuck in even slightly non-neutral AoA would make the a/c uncontrollable. As far as removed, the answer would be that the delta winged canards like the eurofighter and rafale can because they have delta-wing shape which is inherently stable, where as the gripen could not because it (very unwisely) chose a conventional wing shape that offers no stability. This is why the gripen has had problems with "deep stalls" whereas the eurofighter and rafale has not.

:confused:No matter how hard I look, I don't see substantial differences in shape of the wings of the JAS39 and Rafale..

By: Erkokite - 8th February 2011 at 02:15 Permalink - Edited 1st January 1970 at 01:00

I don't know- the Gripen looks like a delta to me. :D

By: arquebus - 8th February 2011 at 02:54 Permalink - Edited 1st January 1970 at 01:00

:confused:No matter how hard I look, I don't see substantial differences in shape of the wings of the JAS39 and Rafale..

After looking at line drawings of the rafale and gripen, I have to admit the plane shape of the wing is almost identical as well as the placement of the wing in relation to the fuselage. So I'll admit Im wrong, and will remember to not go by memory but verify statements I make about a/c next time.

By: Amiga500 - 8th February 2011 at 22:29 Permalink - Edited 1st January 1970 at 01:00

This is why the gripen has had problems with "deep stalls" whereas the eurofighter and rafale has not.

WHAT?!? :confused:

Do you know what a deep stall actually is?

I look forward to you explaining how a canard configuration can experience unrecoverable deep stall.

By: haavarla - 8th February 2011 at 23:54 Permalink - Edited 1st January 1970 at 01:00

'Deep stall'?

Thats a new one.:)
Does this qualified as a 'deep stall'?

http://www.youtube.com/watch?v=KKMS6zgVJww&feature=related

Whats important is not if an aircraft somehow could enter a 'deep stall', but can it 'recover' from it and how 'fast' its done!

Different aircraft has different stability from the overall design, this regardless of any carnards.
The IAPO made Flankers with its carnards, aka MKI is second to none when it comes to spinn/stall recovering ability.
Same story if it is damaged, aka loss of some control surface.
In that respect the two engine Rafale and EuroF has an edge in survival, over a singel engine fighter.

When an F-15 could land, missing a wing. The EuroF can make due with one or both carnards disabled me think..

By: arquebus - 8th February 2011 at 23:57 Permalink - Edited 1st January 1970 at 01:00

WHAT?!? :confused:

Do you know what a deep stall actually is?

I look forward to you explaining how a canard configuration can experience unrecoverable deep stall.

very easily actually. All the eurocanards have thrust to weight ratios less than unity, so unrecoverable stalls are a major area of concern as they cant power out of them. Keep in mind the eurocanards are all FBW, a computer is both steering and stabilizing the a/c, the the pilots input is only telling the computer where to go. This is why the F-18 has to be launched off a carrier on autopilot, the jet is pitching back and forth to try and maintain stability balanced between lift and speed. A pilot cant know which pitching movement is being caused by the jets FBW computer and and which is caused aerodynamically so they just give all control to the plane.

Back to the point of deep stalls: All the eurocanards have CoL of the main wing behind the CoG, with the canards much smaller area ahead of CoG, so the canard is contributing lift to balance, but a very small amount. Although the size of the canard is very small in relation to the wing, it is positioned very far forward of the CoG for better leverage requiring less drag inducing AoA. This means CoL of main wing and canards is balanced squarely over CoG and so the a/c will not pitch down in a stall. And the eurocanards cant fly out of a stall because....theyre stalled, the wings and control surfaces have lost aerodynamic control, neither does the FBW computer know whats forward at such drastic speed loss and lack of indicated AoA. And as I mentioned, they cant power out of a stall because of their sub-unity thrust to weight ratio.

The situation is even worse in non-FBW canard jets like the viggen. Such a jet cannot be controlled aerodynamically at anything but the slightest AoA and therefore the plane must land without an increased AoA using autothrottle to control speed of decent and make a brutal non-flare landing.

The IAPO made Flankers with its carnards, aka MKI is second to none when it comes to recovering ability.

keep in mind the current generation of mig-29/su-30 family of jets are not FBW by design, these jets would not be able to manuever like they do with artificial stability and would become uncontrolable in maneuvers like the cobra. The thrust to weight ratios being well in access of unity is a major factor in these jets maintaining control when stalled.

By: haavarla - 9th February 2011 at 08:18 Permalink - Edited 1st January 1970 at 01:00

arquebus@
keep in mind the current generation of mig-29/su-30 family of jets are not FBW by design, these jets would not be able to manuever like they do with artificial stability and would become uncontrolable in maneuvers like the cobra. The thrust to weight ratios being well in access of unity is a major factor in these jets maintaining control when stalled.

Now you lost me..:confused:
Pls provide some sources or explain this further..

Do you know when the first Russian FBW system on a fighter was official put into service..?

Here is a readup on the MKI Flight control:

Mk.3, a further development over the existing MKI variant, will integrate avionic systems being developed for the Indo-Russian Fifth Generation Fighter Aircraft program. The aircraft has a fly by wire (FBW) with quadruple redundancy. Depending on the flight conditions, signals from the control stick position transmitter or the FCS will be coupled to the remote control amplifiers.
These signals are combined with feedback signals fed by acceleration sensors and rate gyros. The resultant control signals are coupled to the high-speed electro-hydraulic actuators of the elevators, rudders and the canard. The output signals are compared and, if the difference is significant, the faulty channel is disconnected. FBW is based on a stall warning and barrier mechanism which prevents development of aircraft stalls through a dramatic increase in the control stick pressure. This allows a pilot to effectively control the aircraft without running the risk of reaching the limit values of angle of attack and acceleration. Although the maximum angle of attack is limited by the canards the FBW acts as an additional safety mechanism.

By: arquebus - 9th February 2011 at 09:22 Permalink - Edited 1st January 1970 at 01:00

Now you lost me..:confused:
Pls provide some sources or explain this further..

Do you know when the first Russian FBW system on a fighter was official put into service..?

no I dont know when the first russian FBW system was put into service, I havent kept up on military aviation the last few years, but Im sure that russian next generation jets being worked on will be FBW. But the mig-29 and su-30 is not

By: quadbike - 9th February 2011 at 09:28 Permalink - Edited 1st January 1970 at 01:00

The Su 30 MKI has digital fly by wire. The failure of which crashed a jet as well.

By: haavarla - 9th February 2011 at 12:22 Permalink - Edited 1st January 1970 at 01:00

The Su 30 MKI has digital fly by wire. The failure of which crashed a jet as well.

Wasn't that a pilot error?
Tought the report showed the pilot had messed with the G-limit switch or something..
Soukhoi and HAL did improve the 'safty' switches controlling the FCS and G-limit, so it couldn't be accidently tampered with..
I swear there was some news of this back.

no I dont know when the first russian FBW system was put into service, I havent kept up on military aviation the last few years, but Im sure that russian next generation jets being worked on will be FBW. But the mig-29 and su-30 is not

ok.
Sorry for going off-topic a bit, but i have some readup for you on the MKI and now the latest Su-35S, which have an new and improved FCS.

"Russia & CIS Observer / Archive / №3 (22) August 2008 / DEFENSE / Sukhoi Su-35 Achieves Supercruise Flight /
Vladimir Karnozov

Sergey Bodgan Sukhoi Su-35 chief test pilot:

Russia's new Sukhoi Su-35 fighter is already showing its high-performance capabilities. This new single-seat aircraft — which combines the proven Su-27 Flanker airframe, 16% more powerful engines and a totally new set of onboard systems — is said to have reached supercruise speed, a distinct feature of fifth-generation fighters.
According to Sukhoi's strategy, the introduction of its single-seat Su-35 multirole fighter as a "4++" generation of combat jets will help maintain sales of the Flanker aircraft series until an exportable fifth-generation fighter becomes available. The Su-35 also will serve as a platform for testing the onboard systems of is intended next-generation successor.
The importance of this new aircraft in the Russian defense doctrine is so high that on the day after its 55-minute maiden flight in February 2008, the Su-35 prototype was inspected by the country's President Vladimir Putin and his successor Dmitry Medvedev. Sukhoi test pilot Sergei Bogdan briefed the Kremlin guests on the fighter. He recalls that the first question Vladimir Putin asked was: "Will the fifth generation fighter differ in appearance to this one?" The answer was: "Yes, it will. The fifth generation fighter is to have a totally redesigned airframe, while keeping [the Su-35's] onboard systems."

Surplus power

During the test flight at the highest thrust regime without the use of afterburner the Su-35 achieved Mach 1.1 speed and was still accelerating
By late June, the no. 1 flying prototype had completed 13 test missions. These were devoted to assessment of the airplane's stability and controllability, maneuvering characteristics and powerplant performance. In addition, the operation of onboard systems was closely monitored. Having received a generally positive assessment of the aircraft, Sukhoi sent it into the supersonic regime. On mission 12, the airplane accelerated to Mach 1.2 at medium altitudes (up to 6,000 meters). The next flight went as high as 11,000 meters and reached speeds of Mach 1.3.
Importantly, the airplane demonstrated its ability to maintain supersonic speed at military power (the highest thrust regime without the use of afterburner). Sergei Bogdan selected his words carefully, but did state: "At medium altitudes and with military power, the airplane was making a moderate supersonic speed and still accelerating. In one of the flights, I achieved Mach 1.1, and while the aircraft could accelerate further, I had to slow down because I was approaching the end of our supersonic flight zone."
Sukhoi continues assessments of the recorded parameters in order to determine whether the airplane had actually attained supercruise. Additionally, the company continues to define altitudes, weights, external and internal loads at which the Su-35 can reach its supercruise performance. A number of additional missions shall be devoted to these assessments.
"The power reserve is clearly seen when the Su-35 is accompanied by a Su-30," Bogdan says. "During the very first mission, I had the chance to assess how well the Su-35 responds to the throttle. When I was accelerating at combat power, the chase plane's pilot had to use afterburner from time to time. And still, he was going slower."
In afterburner, the Su-35 accelerates much faster than the original Flanker. This is due to the increase in engine power at full afterburner from 12,500 to 14,500 kgf. During takeoff, the ground run is shorter, as the pilot is given much more freedom in pulling back on the stick. The onboard computer takes responsibility for preventing tail strike and other unwanted consequences of over-rotation. With smart computer control over critical regimes, the Su-35 can become airborne much faster than legacy fighters, taking full advantage of excessive power and superagility.

"Artificial intellect"

Generally speaking, an "artificial intellect" takes care of everything in the Su-35, easing the pilot's job. "In the air, the aircraft feels smooth and comfortable, obedient and highly responsive at the same time," one program designer said. "The computers also care for the airplane's 'crisp reaction' to a pilot's input. For example, the computer activates the rudder to automatically compensate for any yaw effects that can originate from pilot deflecting the stick sideways for banking with the ailerons. In 'classic' airplanes, it is the pilot's job to compensate for cross-channel influence, a skill he amasses as his flight experience grows."
Powerful onboard computers significantly improve the Su-35's responsiveness and reaction time compared to the original Su-27. Experienced pilots flying both the MiG-29 with its mechanical linkage and the "fly-by-wire" Su-27 routinely praise the MiG's better responsiveness. They also feel a short delay in the Flanker's response to control inputs. Even when pilots prefer the Su-27 over the MiG, they'd like to eliminate the Su-27's flight control delays — something that will be a reality on the Su-35. Bogdan claims Sukhoi achieved a real breakthrough in the field of controllability with the Su-30MKI — a follow-on version to the Su-27. Most of the new algorithms for the successor Su-35 were successfully evaluated on the Su-30MKI. The Su-35 builds on the Su-30MKI's experience, and goes even further in the area of computer-aided flight controls. In part, this improvement is due to the use of an all-new system for the measurement of airborne parameters, employing latest technology.
The newest Sukhoi jet does not have canards, reducing the drag generated by these forward fuselage-mounted control surfaces (which are used on the Su-30). However, canards do provide improved performance and controllability at high angles of attack. Since the size of the wing remains the same, removing the canards from the Su-35 results in a smaller total area for the horizontal surfaces. However, by reworking the airframe for lower weights (with the use of more composites, for example), removing the canards and deleting the aircraft's large upper air brake along with the activators, Sukhoi designers managed to reduce Su-35's structural weight to that of the original Su-27. Choosing a more classic layout for the Su-35, its designers were also driven by the super cruise considerations.

Controlling the thrust

Sukhoi designers have no doubts that thrust vector control is a must for modern fighters
What the Su-30MKI and the Su-35 do share is their thrust vector control. Sukhoi has no doubts that thrust vector control is a must for modern fighters. With the Su-30MKI now operational in India, the Su-30MKM in Malaysia and the Su-30MKA in Algeria, vectored thrust has now earned its place in the history of supersonic combat aircraft.
Sukhoi pilot Sergei Bogdan underscores the benefits of vectored thrust at slow speeds. "We can fly slow, keeping a high angular speed during a bank. Inertial forces try to increase the angle of attack when the airplane rotates with the ailerons, but we use vectored thrust to create a compensating force generating a pitch-down motion," he explains. "Thereby we keep the angle of attack under control. In the end, the airplane remains controllable in a much wider flight envelope. Besides, it can demonstrate faster angular speed in bank."
Thrust vector control provides a maneuvering advantage in air combat, with the pilot having the ability to get the enemy in sight faster than its opponent to shoot first. Bogdan acknowledges, however, that air-to-air combat is more and more rare, leading to some skepticism within military circles about the value of investing in thrust vector control.
Admittedly, thrust vectoring is not completely useful at low speeds. A small nozzle deflection helps in supersonic flight as well and it also can provide stand-by control functions in case of failure with the primary flight controls.
For air combat involving long-range missile engagements, the Su-35's high climb and acceleration rates, plus super cruise regime, modern missiles and extended-range electronically-scanned radar are considered as clear advantages for the new Russian-developed fighter. The aircraft's Irbis-E radar, developed by the V.V. Tikhomirov Scientific-Research Institute of Instrument Design (NIIP), is a follow-on to the Su-30MKI's N-011M Bars radar.
By combining "something old, something new," Sukhoi hopes to be able to offer the Russian military and overseas customers a highly capable combat jet with good "out of the box" reliability from its entry into service."

By: Levsha - 9th February 2011 at 12:40 Permalink - Edited 1st January 1970 at 01:00

I always thought the original Su-27 uses an analogue FBW system for flight control?:confused:

By: haavarla - 9th February 2011 at 12:43 Permalink - Edited 1st January 1970 at 01:00

yes you could be right, but not the later Su-30 series.

Pretty sure the Su-27SM got some better FCS vs the legasy Flanker.

Also note that the RuAF legasy Flanker has gone through several small upgrades years back like the Su-27S=domestic SK variant, Su-27P, Su-27PD etc etc.
Don't have any data on the FCS history though..

Perhaps 'Flanker Man' could shedd some light on this..?

By: Scorpion82 - 9th February 2011 at 13:37 Permalink - Edited 1st January 1970 at 01:00

very easily actually. All the eurocanards have thrust to weight ratios less than unity, so unrecoverable stalls are a major area of concern as they cant power out of them.

What? The Rafale and Typhoon actually have a TWR in excess of 1:1. It's about 1.15:1 for the Typhoon and 1.07:1 for the Rafale. The Gripen is the sole type with a slightly inferior to 1 TWR!

Back to the point of deep stalls: All the eurocanards have CoL of the main wing behind the CoG,

The point of instability actually is to have the CoL in FRONT of the CoG and that's true for ALL THREE ECDs.

keep in mind the current generation of mig-29/su-30 family of jets are not FBW by design,

Wrong the Su-27 was a FBW aircraft from the very beginning, not pure FBW (yaw and roll axis were still controlled by mechanical links), but FBW for pitch as the aircraft was designed with relaxed stability in mind. Newer variants are even more unstable and all the newer variants such as the Su-27M, Su-30MK, Su-27KUB, Su-35UB, Su-32/34 and Su-35S are fitted with all electronic digital FBW controls.

these jets would not be able to manuever like they do with artificial stability and would become uncontrolable in maneuvers like the cobra.

They obviously can!