viperzerof-2 wrote:https://www.flightglobal.com/combat-ready/27260.article
Prototype Rafales are limited to a maximum take-off weight of 19,500kg, although, after a modification to the undercarriage, the production aircraft will be cleared to 22,500kg. Eventually, the maximum take-off weight may be further increased to 24,500kg. The empty weight of the aircraft was 10,000kg, with the external stores contributing a further 4,500kg to give a weight without fuel of 14,500kg. The maximum fuel load that could be carried was therefore 5,000kg, of which 800litres, weighing 680kg, was in the centreline fuel tank.
The prototypes have been tested to 22,500kg using air-to-air refuelling (AAR) to top up the external tanks. This is commonplace because it extends the duration and productivity of test sorties and allows several test points to be achieved in one flight at maximum weight. For this flight, the aircraft had a fixed refuelling probe fitted to the right side of the nose ahead of the cockpit. The Rafale FCS has a sub-mode tailored for AAR.
The engines took 5s to achieve full thrust, at which point the aircraft was accelerating briskly at 0.56g (longitudinal). The stick back speed was 150kt (277km/h) and the aircraft lifted off at about 165kt after 15s, including the time taken for the engines to accelerate. It was easy to keep straight in the 7kt crosswind component from the right using nosewheel steering up to 60kt, at which point it automatically disengaged.
Rotation to a suitable take-off attitude was easy, although I initially underestimated the pitch responsiveness and corrected forward rather more aggressively than I would have liked to maintain the initial climb flightpath angle (FPA). The undercarriage retracted in 5s, with no trim change. The FCS laws change from angle-of-attack (alpha) to g demand with the undercarriage retracted.
The initial climb to 10,000ft away from the Istres circuit area and westwards across the serene Carmargue countryside was made at full dry thrust at 340kt (a nominal rather than ideal speed) at an FPA of 15º.
The Rafale FCS automatically trims the aircraft in all three axes. In pitch, it trims for 1g flight, so speed changes are made without the pilot needing to retrim manually. The only time that conventional static stability is introduced is above 16º alpha, the normal approach incidence, with the undercarriage down. Throughout this flight, the autotrim system worked well and unobtrusively. I was briefed, but could not check, that the system copes with asymmetric loads, such as a hung-up bomb.
Once level at FL100, at 300kt and 85% engine core speed (NH),I made a few turns before manoeuvring the aircraft more aggressively. Immediately I was reminded how useful a well-sorted HUD is for accurate flying. Level turns at 45º (90% NH) and 60º (93% NH) angle of bank merely required keeping the aircraft symbol on the horizon line and adjusting engine thrust to keep the energy markers at neutral. This was an easy, straightforward and intuitive process that gave level turns accurate enough for any instrument-rating examiner.
Four full-stick rapid rolls through 360º were made at 1g and 2g at 300kt. The roll acceleration was good and, in each case, the roll was completed in 3.5-4s. The peak roll rate was about 150º/s. Without the heavy external stores, the FCS would have allowed a higher roll rate of 250-270º/s. The aircraft was inverted briefly in level flight - something only a test pilot would attempt with two large cruise missiles and three external tanks on board - and remained easy to fly accurately. The FCS limits negative g as well as positive g, although I did not bring in the g limiter during this test point.
Finally, before climbing to high level, a hard turn was made, starting at 330kt using full reheat, principally to test the behaviour of the FCS. This was the first moment in the flight for controlled aggression. I simply rolled the Rafale into a nose-down steep turn and, as the reheat became effective (about 2s), moved the stick quickly to the aft stop. The aircraft responded by rapidly achieving 5g at 17-18º alpha, turning smoothly and without buffet with the stick held on the aft stop.
Heading north towards the mountains, we climbed to 25,000ft. I wanted to explore the Rafale's handling at high level at the Mach limit in the current configuration - 0.9 indicated Mach number - and in a typical long-range cruise condition. The climb also gave me an opportunity to look more closely at the autopilot.
At a typical cruise speed of M0.82/347kt, the aircraft could sustain a 60º banked turn at maximum dry power. Slamming the throttle to maximum reheat and rolling quickly into a full stick-back hard turn to simulate a break away from a threat gave a rapid response, automatically limited initially to 18.8º alpha and 4g. As the turn progressed, the FCS allowed the incidence to increase to 19.2¼ alpha as the airspeed decayed. Again, I was impressed with how easy it was to extract the maximum performance from this heavily loaded aircraft.
Rolling back to wings-level flight, I re-engaged reheat for a level acceleration from M0.6 to M0.9 in 35s. As the aircraft approached the Mach limit (M0.9) for this configuration, there was a slight airframe or aerodynamic rumble from the external stores. At M0.9, I quickly retarded the throttle to idle, without any noticeable trim change, and selected the airbrakes out to decelerate the aircraft rapidly back to M0.6 in 37s. There was no trim change with engine thrust variations at this or any other time during the flight.
Simulating the end of the cruise portion of a high-low attack profile, we descended at idle thrust into the low-level part of the flight over the picturesque ridges and gorges of southern France. On the way down, I reselected the autopilot and the flightplan route and engaged the terrain following (TF)system at a set clearance height of 500ft above ground level (AGL). The aircraft descended at 14º FPA and began to level off automatically as it passed 1,500ft AGL. I engaged the autothrottle at 400kt and sat back with my hands off, but close to, the controls as the aircraft followed the scheduled route across rugged terrain.
Despite many years' experience of flying TF systems, I still found it impressive to allow an aircraft to fly hands-off close to the ground through mountain passes and across ridges. The autopilot used from 3g to 0.2g and accurately crossed ridgelines at 500ft AGL. It is anticipated that the TF system fitted to the Rafale BO1 will eventually be cleared to 100ft AGL over land and 50ft over water.
The Rafale TF system uses a radar altimeter as the primary sensor and a digital data map of the earth, rather than a radar system. This has two advantages. Firstly, it eliminates the radar emissions that can be detected and jammed by an enemy. Secondly, the TF system has information about the terrain profile all around and can manoeuvre the aircraft to the maximum allowed either via the autopilot or manually by the pilot. During this flight, the aircraft, under autopilot control, crossed a ridgeline in an 85º banked turn at 3g - a manoeuvre that would surely get a pilot's attention at night or in cloud.
Much as I was enjoying flying at low level, I wanted to finish my investigation of the aircraft's handling before recovering back to Istres, so, with maximum dry power applied, a climb at 16º FPA was begun, initially to 5,000ft. This brief check in the climb profile allowed time for a dry power level acceleration from 309kt to 460kt in 35s.
When cleared by air traffic control, the Rafale was further climbed into the height block between 5,000ft and 10,000ft. Once level, it was accelerated to M0.88 for a hard turn using full reheat to the FCS g limit. Although I entered the turn quickly, the voice warning (female) informed me that I had slightly exceeded the configuration limit of M0.9 (it was M0.91). The FCS limited the aircraft to 5.2g.
Once in the turn, I adjusted the roll and pitch attitude so that the aircraft decelerated, still turning with full back stick, so that, at 330kt, the FCS transitioned from the g to the alpha limit of 20.8º, an incidence that was maintained until I rolled out at 200kt. Finally, to give the FCS a further hard test, I made full-stick rapid rolls with the stick held fully back. At the incidence limit, the aircraft took 6s for a 360º roll and 5.5s at the g limit of 5.4g. The rolls were smooth and the roll rates even. Given the configuration, this is an excellent performance.
On the way back to Istres, the Rafale was slowed down with the undercarriage lowered (taking 5s) to full back stick. With 1,410kg of fuel remaining (aircraft weight 15,900kg), the minimum speed was 120kt at 18º alpha. As noted before, the ideal approach incidence is 16º alpha and, above this incidence, the control column must be deflected aft of neutral. At 18º, the voice warning reminds the pilot to reduce incidence.
The final manoeuvre before entering the circuit was to loop the aircraft from 3,200ft. As with inverted flight, I suspect only test pilots would expect an aircraft to loop while fitted with two cruise missiles and three fuel tanks. The minimum entry speed was 360kt, but I elected to use 390kt to give myself a slightly wider margin in view of the aircraft's heavy configuration. Using 4.5g at the entry to the loop and full reheat until pointing vertically down, the manoeuvre was easy to fly and totally undramatic. Without trying to minimise the size of the loop, the maximum altitude was 9,500ft and the aircraft was back in level flight, having gained 1,000ft on the entry height.
Compared with simple general aviation aircraft, modern automated fighter systems are easy to manage in the circuit. Two right-hand circuits were flown to Runway 15 with a wind of 190º/16 kt, gusting to 20kt. At Kerherve's suggestion, during the first circuit I used the autothrottle to maintain 16º alpha from midway along the downwind leg all the way to touchdown - this constant incidence technique is favoured by naval pilots.
Although you could invent more checks, the only really important actions are to put the undercarriage down and check the fuel. The aircraft remained easy and straightforward to fly, the HUD helping considerably with the approach. The aircraft symbol was displayed on the HUD velocity vector and there were 3º descent markers. The optimum approach incidence was shown by two bracket symbols, which were either side of the aircraft symbol at the correct incidence. All the pilot has to do is adjust the flightpath so that the 3º markers are beside the touchdown point, put the velocity vector on the threshold and control the speed to achieve the approach incidence. Perhaps that sounds difficult, but in practice it is straightforward in the Rafale or any other aircraft.
Shortly before touchdown, the velocity vector was raised from the touchdown point to about halfway down the runway to give an easy flare into a perfect touchdown at 132kt. Applying full throttle to execute a touch and go tripped out the autothrottle.
The final circuit to land was flown using manual throttle control, which I found no more difficult than with autothrottle and allowed me to fly the final turn at a slightly higher speed and lower incidence. After landing, the gusty crosswind held the right wing up until I positively de-rotated the aircraft on to the runway.
The total flight time was 1h and the landing was made with 690 kg of fuel remaining. As I taxied back, a Mirage 2000 was beginning another rehearsal for the Paris air show.
27 Jan 2022, 08:46
LPI_Jamming_a456960.pdf
I'm currently hiring someone to do simulation of fighters and weapon RCS using blender and HFSS, when the result are available, I will send you (total free). You can add these diagram/map into your file
