The International Rafale forum

Dossier Rafale :

Airframe, fly-by-wire, CAG


Formula :

The extreme versatility required for the new aircraft draw Dassault to choose the delta-canards aerodynamic configuration on a moderate weight of 10-tons airframe with a high thrust (15 tons with two M88-2).

Experts in delta wings, with the need to do the best as well in air-superiority as for very low level penetration, the research departments chose a moderate wing sweep and a high aspect ratio (48° versus 58° for the Mirage 2000). The wing is mounted on a medium height on the fuselage, and is improved with LERX forming a 72° angle, elevons, and one mobile leading edge slate per wing on all their length.

So as to further optimize those wings, large area canards plans are positioned near and slightly above the wing (coupled canards) : this position, ideal for high alpha air flows but also during cruise, provides the best behavior for all regimes, and all payloads.

Another new feature of the Rafale formula : the air intakes are semi-ventral with no moving parts. They provide better air supply from 0 to Mach 1.8, from -3 to 9 g. In addition, again to make the airframe as simple as possible, those intakes as designed so as not to use a boundary layer sucking device.

Requirements in terms of yaw stability being already met with this configuration, the lone vertical fin is proved to be enough.

The aircraft uses no airbrake : canards and elevons were chosen to do the job accoring to the flight parameters.

Material and strength :

The light weith of the aircraft (only one ton heavier than the F-16) has been obtained by abundant use of composite material, from carbon fiber (belly, back, wings, around the cockpit), kevlar (nose and rear fuselage), hybrids, aluminum alloys (with lithium) and titan. Finally, at least 30 per cent of the airframe is made of composite materials. This makes the Rafale very strong while being light, easily exceeding the planned 30 years of service. Even after 10,000 flight hours (the Armée de l'Air plans on 7,000 hours with 3,500 landings), the airframe is still capable to sustain 185 per cent of the nominal efforts before breaking.

Survivability

Also influencing the aircraft shape : the survivability requirements drove to attenuate as much as possible the RCS (Radar Cross Section) as well as the IR (infrared) signature. To achieve this, the airframe has no right angle, or very few, no rupture, no slot of relief and the shape is linear. The air intake ducts are "double-S" shaped so as to hide the compressor blades. Some areas remained very hard to hide, and thus, they were concentrated on the airframe and treated with RAM (Radar absorbant materials), saw tooth on mobile parts, gold layer in the cockpit canopy so as to hide to pit. The radome only allow the RBE-2 waves to pass, then every antennas and little shapes as well as the fin are made of radar transparent materials. Other solutions are applied for the IR signature, some weapons are also treated (Scalp) against radar waves.

All those solutions (but not only those) allow the Rafale to be "discreet", which materialize though the adoption by armies of special tactics to benefit from this discretion affecting the hostile sensors' ranges.

Controls

The aircraft controls are actioned by a double hydraulic circuit providing 350 bars (5,000 psi). The actuators are controlled by digital fly-by-wire.

The CAG (Contrôle Actif Généralisé = Active Global Control ?) acts on three digital channel, and an analog channel for back up, which can be used automatically of if the pilot wants it (less prone to jamming, but less performant). Those four channels are totally independant which blocks any catastrophic software bugs. The system allows for exemple to deal with the moderate longitudinal negative stability, to use an auto-trim, to adapt the controls sensitivity according to the flight phase, due to its high integration to use a extremely sophisticated auto-pilot, and in case of damage, to reconfigure automatically the controls so as to preserve the handling qualities. All of this means that the CAG is a major asset to reduce the pilot workload and let him concentrate on the tactical situation instead of on the flight.

Those FBW also give the aircraft both remarkable agility and maneuverability, as well as for air superiority as for low level penetration during which an heavily loaded Rafale have to cope with 5.5g accelerations in transonic speeds at 100 feet.

For example, even with the maximum payload, the response in roll keeps nearly unchanged.

Some data :

• speeds from 100kts (in all configurations, even 24.5 tons and fully controllable in roll) to Mach 1.8 (though Mach 2.0 is possible). Fuel tanks qualified for Mach 1.6. During dogfights against M2000, a Rafale slowed down to 18 kts without loss of control.
• Corner speed : 360 kts ;
• Software limits :
  
  • Angle of attack : 29 or 30° in air-to-air, 25° with heavy payloads such as Scalp, 2000L fuel tanks, air-to-ground weapons. The aircraft has shown stable at 32°, and even reached 100° with a negative speed of -40kts without loss of control) ;
  • roll rate : 290°/s clean, 270°/s in air-to-air, 190°/s in air-to-ground configuration ;
  • acceleration Gz : 9g in air-to-air configuration (maximum : 11g), 5.5g in air-to-ground configuration.

Other demonstrated performances : take off in 400 meters in air-to-air configuration, 600 meters in heavy configuration, approach speed : 115kts, with a sink rate of 4 m/s without rounding out.

The 10 tons fighter can take off at a MTOW of 24.5 tons, with a possibility to increase it up to 27 tons.


Rafale M

The Rafale M has a strengthened structure and a retractable ladder. Its landing gear is also strengthened so as to cope with sink rate of 6.5 m/s. The nose landing gear uses the "jumper strut" technology so as to allow the fighter to take off after only a 75 meters run with a payload exceeding 21.5 tons (22.5 tons demonstrated). Its bring back capability is of 15.7 tons, which allow not to waste costly weapons.

The commonality requirement induced that all variants are treated against corrosion.





Author notes :
I used very various well know sources here, from HP Grolleau, Dassault documents, Chris Yeo (former BAe pilot), Air & Cosmos, etc.
This page is a translation of my website :
http://tmor.rafale.free.fr/trois.html

Just a little reminder for those who (infortunately) got intoxicated by some unwelcome propaganda about Rafale Maximum g and service life:

The B and C airframes were designed as a downgrade from the M; NOT the other way aroud.

In effect this means that the 11.0g Maximum structural loads is well within the 7.000h service life margin (As opposed to what was sugested by some in a now well known Rafale basher's favourite forum).

http://www.dailymotion.com/relevance/search/Le+Roi+du+Ciel#hp-h-9

Here is a serie of semi-official videos where this information is made available, among other, very useful and intersting stuff.

I do not agree with you on this point. But why arguing ?

Telling the truth is NOT arguing, it is called making corrections.

We have people in forums who are there to look for informations, reason for the desinformation in the first place, so i'll keep "arguing" as long as desinformation will be posted.

We're French, Rafale is France technology "window" (fenetre according to the GIE) and attacking it in a permanent basis is an offense to me and an insult to our country.

Think about it.

Ok.

I'm going to answer you, ONCE. LoL

We have 4 separate public claims :
1) 7.000h service life ;

2) 8 G operational G limit (software) ;

3) 9 G design airframe ;

4) 11 G max limit.

I see no possibility to establish a "the truth" that the 7.000 hours are for the 11G limit. We simply don't KNOW enough.

This is why I respectfully disagree with you.

7.000h service life for all loads below the margin.




What you call "software" is NOT a stop limiter setting but audio and visual warning.




Not it is NOT a "9.0 g design airframe".

This was the Eurofighter design method, and it goes with not 7.000 but 6.000 h.

And aircraft which brakes at 185% of its maximum Operational load of 9.0 g can easely sustain 11.0 g picks in combat situations without seing its service life going under.



Originaly, according to my sources the Mirage 2000 had a hard stop of 13.5 (1984 Farnborough brochures), the 11.0 g must be not only imposed in regards to the airframe fatigue life but also the crew.

Considering RAfale is bulit even stronger to the M structural standards i dont see where yuou have an issue with 7.000 h and 11.0 max.




SORRY, you should write YOU simply don't know enough.

There are International design standards and they apply to all manufacturers.

The Internationl standard is 1.6 above the Operational g limit, on fighters today it is 9.0, that of Typhoon was lowered to 1.5, that of Rafale is 1.85, it's easy to put together when one is willing but as usual you are leveling things by the lowest level.



You have the habit to desagre on everythnig you don't know and it's a lot in this field must i respectfuly say.

http://www.aviationweek.com/aw/generic/ ... l%20System


I don't know what to do about this data, but it's still interesting to keep it on record.