Yes.SaiK wrote:Q: Did the pilot die?
http://www.bangkokpost.com/learning/adv ... to-bangkok
Few ppl see problem with canards..Read comments.
https://theaviationist.com/2017/01/14/t ... -thailand/
Yes.SaiK wrote:Q: Did the pilot die?
Gripen max alpha 26 degreesFlight testing has been going "extremely well", according to Saab, with the aircraft recently being cleared to fly its full operational envelope. So far, maximum speed at altitude (which Saab will not disclose, but is likely to be about Mach 2.2), has been achieved, but low-level speed checks await flutter clearance. The aircraft has been validated to the maximum 9g load factor, and has achieved 5g. Angle-of-attack tests have reached 20°, and will soon reach the maximum 26°, says Saab.
Firing of an unarmed AIM-9L Sidewinder missile at the Vidsel firing range was a "complete success", and the aircraft will begin full weapons deployment trials shortly. Performance of the General Electric/Volvo RM12 engine has been "flawless" in the more than 230 JAS39 flights to date. "We have the same comment about the avionics and databus, " claims Saab's director of flight operations, Per Pellebergs. On systems, however, "...wehave had our moments of disappointment", with flights interrupted by malfunctioning fuelsystem components, troubles with air-conditioning and cooling and problems with the auxiliary power unit.
Zero-lift and induced drag of the JAS39 is "much better than specification", says Pellebergs.
There were other problems that plagued its early development as well, but I won't be posting on that here.
The Saab JAS39 Gripen programme has run into further problems following the discovery by Volvo Flygmotor of cracks in compressor blades of three RM12 jet engines. The Swedish engine manufacturer was expecting to announce this week the effect on the flight-test programme. Volvo discovered the cracks during routine inspections of RM12 engines being groundtested late last year at its plant in Trollhattan, Sweden, but news of the problem has only just emerged. The three affected engines had each accumulated between 500h and 800h—the longest running of the ten built. A total of ten cracks has been detected by ultrasound in a region near the blade roots in the third-stage compressor of the three engines.
The engine firm is analysing the nature of the cracks and Engine problem casts new shadow over Gripen attempting to ascertain the cause. Fatigue or vibration are suspected. It says that it is too early to say whether flight testing of the second Gripen prototype will be delayed.
Volvo says that it developed the RM12 with General Electric and that the firms would have to bear the cost of curing the problem. The Gripen's engine "thrustdroop" problem which recently came to light threatened to hit the new aircraft's quick-response time, a crucial design requirement (Flight, 24-30 January). Volvo says that it has designed cures and that the Government must choose between them. Options are a switch in materials or an increase in turbine temperature at take-off. Volvo admits that these could affect maintenance costs and engine
life-cycle costs.
No, please not "HAL Tejas". Tejas is not HAL's product alone. You can call it Tejas to differentiate it from the Naval LCA, which now has its separate thread.Rakesh wrote:Can we please rename this thread to HAL Tejas: News & Discussion?
Once it has completed all its tests and is in IAF squadron service we can call it Tejas.Rakesh wrote:I just meant to remove the LCA name. Just Tejas works as well. No need for LCA anymore.
linkSaab's JAS39 Gripen prototypes are flying with a redesigned,less advanced control stick than that planned initially after the original system, which featured advanced-technology electric-torque motors, suffered problems during early testing. The Swedish company has contacted foreign control-stick manufacturers for price quotes in case the new system is unsuccessful.
Saab says: "The control stick, centrally located in the cockpit, has been subject to an elaborate design and test phase before flight testing started. That included a range of standards, from a totally undamped stick to a design incorporating very advanced, and also complicated, internal mechanisms, such as torque motors." The latter design is the one understood to have been favoured initially, but which has been dropped because of problems which, industry sources say, included jamming. Saab, which developed the original stick, says that from "...extensive simulator studies we have chosen the present stick design with a fairly uncomplicated spring system".While saying that, after more than 200 test flights, no reason has been found to change the present system, the company adds that "...we still have not tested all flight conditions — for example , we have not yet reached the 9g acceleration level in the test programme, and we have not encountered either the most adverse weather conditions or the most demanding tactical manoeuvres".Saab adds that "...in order to be prepared, • should a need for changes arise, we continue to develop both minor improvements and more complicated solutions". The recent report on the Gripen flight-test programme says of the control stick: "The pilots have noticed a tendency to get somewhat tired in arm or hand after some time in manoeuvring or formation flying. We are keeping an eye on this and have modifications to the stick in store in case the need should arise."
linkSAAB IS BEING forced to introduce further changes to the hand stick-controller for its JAS39 Gripen, having previously abandoned its initial design as being unairworthy. The current controller is uncomfortable for pilots' hands, leading to strain on the lower arm. The Swedish air force will take delivery of the first JAS39 Gripen multi-role fighter, equipped with the latest revise of the hand-stick controller, at the end of the year.This longer stick replaces the current mini-stick and is designed to ease arm fatigue, particularly when carrying out operations which require frequent rapid manoeuvres, such as dog-fighting. To prevent strain, the new, 17mm-longer, stick has a lower pivot point in the cockpit and is now curved to fit the contour of the pilot's hand. It was previously virtually straight. Flight testing of the new equipment has been carried out on JAS39 development aircraft.
The change to the centrally mounted control stick is the second major modification to the system. The original design had torque motors which damped the motions of the mini-stick. This system was discarded before the first flight of the Gripen, as it was judged unairworthy. The stick now in use is mechanically damped.
linkThe crash of Sweden's first prototype Saab JAS39 Gripen fighter was caused by a flight control software fault, the accident investigation committee concludes. Committee chairman Olaf Forsberg confirms earlier assumptions that the flight control system was at fault for the February 2 landing accident. "The accident was caused by the aircraft experiencing increasing pitch oscillations (divergent dynamic instability) in the final stage of landing, the oscillations becoming uncontrollable. This was because movement of the stick in the pitch axis exceeded the values predicted when designing the flight control system, whereby the stability margins were exceeded at the critical frequency," he says.
A separate investigation by the JAS Industry Group concludes: "The control laws implemented in the flightcontrol system's computer had deficiencies with respect to controlling the pitch axis at low speed. In this case, the pilot's control commands were subjected to such a delay that he was out of phase with the aircraft's motion. This caused uncontrollable pitch oscillations, which resulted in the aircraft hitting the runway in the final phase of the landing. JAS is now introducing the necessary modifications to the control laws." The accident occurred as Gripen, flown for the first time by Saab pilot Lars Radestrom, was landing after its sixth flight. On finals the aircraft displayed a lack of stability, pitching down, then up markedly, then pitching down again to an angle from which it was not possible to recover before the aircraft hit the runway. On its first five flights the aircraft had experienced problems with lateral oscillations, and on the sixth and last flight oscillation in pitch was also apparent.
Gripen first flew on December 9, some 18 months behind schedule. The delay was attributed to difficulties in proving the software for the flight control system developed by Lear Seigler (now GEC Astronics). Gripen is naturally unstable and has a triplex digital flyby-wire system with a triplex analogue backup. After the first flight, Saab chief test pilot Stig Holmstrom remarked that the control system seemed too sensitive and that the control laws would probably need to be changed.
linkIn its efforts to revalidate the Saab JAS39 Gripen's flight control laws, the JAS Industrial Group has doubled its staff of software development engineers. It has also hired a number of outside consultants to assist with the programme.
The investigation into the crash of the first Gripen figher prototype on February 2 blamed unsuitable control laws, particularly in pitch at low level. The report highlighted that the manufacturers should have analysed the test data from the first two flights in greater depth.
Gripen programme manager Tommy Ivarsson says: "I admit that we should have been more thorough . . . but that was the best judgement of our pilots and engineers at the time . . . There are things which you can never do on the ground which still have to be done in the air."
Since the crash, the JAS39 consortium has been working to rewrite the flight control laws and the number of people on the project has been increased by 30.
Ivarsson says: "We are engaged on a long and tedious validation phase, checking all aspects of logic change to ensure that no combination of factors has been missed." Increased resources have been made available for simulation, and the test pilots are being stretched to a greater extent in the simulator. Two new Swedish test pilots have been selected to fly the second Gripen prototype.
Irrespective of the fate of a second batch, the Swedish Air Force will start taking delivery of the first 30 Gripens in 1992.
The initial aircraft will not contain the full avionics and weapons systems, but will be used to train instructors and for tactical
evaluation. The first Gripen squadron will form in 1993.
link
Three systems need more work. The British Aerospace electronics cooling system was inadequate and electronics overheating led to several precautionary landings.
The fuel system proved over-complex, suffering numerous spurious low-fuel or transfer warnings.
Lastly, the auxiliary power unit (APU) demonstrated a short time between overhaul and is extremely noisy.
Saab says that the fuel system problem has been solved partly by re-written software, which is being flight-tested. Similarly, the company says that a fix is being developed for the cooling problem and that APU troubles have yet to be resolved — the short time between overhauls being the hardest to redress. The company, while trying to cure the problem by re-designing the Microturbo TGA 15 APU, is also looking at alternative APUs.
linkRevisions to the flight control system of Saab's JAS39 Gripen have turned it into a "very stable airframe, with very good flying characteristics",
according to the Swedish company.
Saab also says that there is a solution available to the problems which have dogged the Gripen's Volvo RM12 engine in early flight trials and which have limited its available flight envelope. Changes in the FCS's software were all that was required to transform the aircraft's behaviour, according to Saab's Stig Holmstrom. The modifications included: changed priorities in the auto-trim; changes to gust response and crosslink between angle of sideslip and roll; decreased gain in some of the feedback loops; and different responses to stick inputs.
The environmental control system malfunction which caused overheating of the avionics and shortened the second prototype's first flight has now been cured, says Holmstrom.
A more pressing matter is resolution of the engine problem which has limited the envelope in which the aircraft can be flown. This has called into question the aircraft's acceptability to the Swedish Air Force.
The first problem is flutter in the blades of the third stage of the engine's compressor. This is being addressed by redesigning the blade and its root. The second problem is that this uprated version of the established General Electric (GE) F404-400 engine suffers from "thrust droop": while the engine is warming up the differential expansions between its static and rotating parts lead to excessive clearances, and prevent it from delivering rated performance for "several minutes" after start-up. This is unacceptable as the Air Force wants rapid response. Volvo and GE have been trying solutions which involved temporary over-rating of the engine to restore cold take-off performance.
linkGripen gets to grips on engine difficulties
Engine troubles on the JAS39 Gripen fighter have been overcome, according to Saab Aircraft. Together with successful revisions to the flight control system software, the three prototypes now flying are exceeding the aircraft's performance expectations.
The Volvo RM12 engine (derived from the General Electric F404-400) had suffered from fan-blade flutter in the third fan stage, and from "thrust droop" — a failure to deliver required power within the specified time from a cold start. Saab director of ground and flight testing Tore Forsstrom says the fan flutter has been cured, and that the thrust droop is "close" to being cured on the production-standar d engines now in use. Company test pilots say that the engine is now delivering acceptable cold-start performance, and add that any further advance to a 100% cure would "... trade off engine life and use extra fuel".
Radestrom's description of what happened, in a release approved by the Flight Investigation Department, reveals his loss of control over the aircraft.
He had kept the aircraft's manoeuvres to an undemanding profile dictated by safety rules, because the display was being held above the city's populated harbour area."It was like sitting on a big ball feeling like you're sliding off it," said Radestrom shortly after the accident. "When I entered the turn [a shallow turn], the computer overcompensated by roughly 10°. When I then straightened out the aircraft, I got an undemanded pitch oscillation and, when I tried to compensate for that one, the aircraft kind of sat down and became impossible to control." At that point, the pilot ejected and the aircraft was seen to perform a nosehigh "cobra" manoeuvre. "I had no other choice than to eject," says the test pilot. Radestrom described the feeling of loss of control as being "...like butter on a hot potato".
Saab says that it was aware of the fly-by-wire (FBW) system software inadequacy which caused the crash of its JAS39 Gripen multi-role fighter on 8 August in Stockholm. The "software limitation" had been reported by one of the company's programme test pilots, but was believed to be at a corner of the flight envelope unlikely to be used. Saab says that the corrections were being held until the next planned development-update of the FBW system-control laws. This was set for October, but may be delayed.
The Swedish Accident Investigation Board's preliminary report says: "The accident was caused by the flight-control system's high amplification of stick commands in combination with large, rapid stick movements by the pilot. This led to the stability margins being exceeded and the aircraft entering a stall." A contributory factor, says the report, was the "late display" of the angle-of-attack warning, "...which gave the pilot too little time to react".
The report, based on flight data-recorder information, says that Saab test pilot Lars Radestrom had flown a left-hand turn at 154kt (285km/h) with 65° bank, at 2g, with a high 21° angle of attack. Radestrom attempted to roll sharply out of the turn by applying full-right aileron and, simultaneously, a sharp pitch down. Instead of stopping at wings level, as intended, the aircraft continued to roll to 20° right bank. The pilot reacted to the bank by a full control column movement to the left, still with pitch down. At this point, the software started to produce control over-reaction, and the pilot started compensating with three or four more full deflectioncontrol-column cycles. Radestrom felt that he had
lost control and ejected. As the aircraft then entered a steep descent, it appeared to have recovered to stable flight. "The aircraft's control system includes a recovery mode. We have observed that this mode has operated in the intended manner," says Saab, while admitting that there was not enough height for recovery.
link
Saab has been forced to modify the most recent flight-control software update on the JAS39 Gripen to improve low-level and low-speed, handling, following the loss of a second aircraft. The modifications follow the recommendations of the Swedish Government Accident Investigation Board into the 8 August, 1993, crash of the second production JAS39.
They are designed to create a "softer" response from pilot inputs to the flight-control system via the control stick.The digital flight-control system's software has also been further modified to prevent events such as pilot-induced oscillations (PIO) because of inadvertent over-controlling of the aircraft. The modified flight-control software is being installed on all five of the JAS39 flight-test aircraft in a bid to minimise any delay caused by the accident and the subsequent investigation. Flight tests resumed on 29 December, 1993, with a flight lasting 45 min. The final report of the board says: "The accident was caused by an imbalance in the flightcontrol system. The imbalance allowed the pilot to apply control commands that did not give the elevons sufficient time to produce the expected response from the aircraft." The report says that the resulting time delays led to a combined PIO in roll and pitch axes, adding that "...the flight control system was unable to limit the command signals".
The Swedish press has reported that the Gripen's weight is over the required eight tonnes. Bengt Schmitdh confirms that there is a slight difficulty over weight. But he puts this in its context: "It is very normal for a development aircraft to have weight problems," he says.
ramana wrote:Thanks for highlighting the issues. Puts the Tejas/LCA program in proper perspective. And the Nirbhay too!!!
Ages ago Air Marshal (retd) Rajkumar had told me that AoA testing for the Gripen continued as it went into serviceKartik wrote:Gripen was rushed into service, without its full avionics or weapons system.
3) Gripen enters service without full avionics or weapons system
Irrespective of the fate of a second batch, the Swedish Air Force will start taking delivery of the first 30 Gripens in 1992.
The initial aircraft will not contain the full avionics and weapons systems, but will be used to train instructors and for tactical
evaluation. The first Gripen squadron will form in 1993.
link
Smriti Z Irani @smritiirani
Components of Tejas & Cartosat-3 Satellite developed by ATIRA from advanced Technical Textiles
The maximum angle of attack limit for the F-16 is actually prescribed as a function of the airplane's g-load. At 1G conditions, the airplane is limited to 25 deg AoA. At around 7G conditions, however, the airplane's software limits the pilot to just over 20 deg AoA and at 9Gs, the airplane is limited to 15 deg AoA.
I hope thats good enough to make folks understand that G limiter is not a function of AoA.Kartik wrote:Ok, another data point for comparison with the Tejas- at 1G, the F-16's max AoA limit is 25 deg. at 7Gs, it is 20 deg AoA and at 9Gs, it is 15 deg AoA.
The maximum angle of attack limit for the F-16 is actually prescribed as a function of the airplane's g-load. At 1G conditions, the airplane is limited to 25 deg AoA. At around 7G conditions, however, the airplane's software limits the pilot to just over 20 deg AoA and at 9Gs, the airplane is limited to 15 deg AoA.
I happen to talk to the Babu who signed the paperwork approving the LCA for RDP. He said he saw three foreign engines, so he signed.Pratyush wrote:What is a single injune phiter doing over rajpath. Isn't that privilege solely for the 2 injure imported jets, with people having orgasm merely at the sight of a Natasha standing erect.
Indranil wrote:I heard that it will be a 5 plane flypast including the three SPs. However, I wish AK had not spoken till the official word came out.
Don't think the Rajpath is wide enough for that.. But the sheer sight of Tejas coming in for landing at Rajpath!!!suryag wrote:A baahubaliesque thing would be to have an aborted landing(touch and go) on rajpath(in front of the chief guest) by two birds followed by flypast by the other three birds
The LCA Tejas will make its maiden appearance in the upcoming Republic Day parade by participating in the fly past over Rajpath, New Delhi.
In the Photo - Five Tejas Aircrafts Lined Up at the NAL Air Force Station in Bikaner.
In order: LSP-03, PV-6, SP-01, SP-02 & SP-03
The Tejas had earlier flown at Indian Air Force Day in 2016 when its maneuvers left the spectators spellbound. It has also flown at the IAF's Fire Power Demonstration - The Iron Fist Exercise, Aero India and the Bahrain International Airshow.