Why would the flight control computer for Tajas need more processing capacity? It suggests that it was under specced and that Tejas is not flying its optimal performance until this upgrade takes place?
Is this why the Dubai crash happened? Was the flight computer overwhelmed ?
It is unusual to upgrade processing capacity of flight control computers for any plane once the design is complete(the JF17 only did because it went from a partial manual setup to a full digital setup which required it ) and the fact the Tejas needs it, suggests another fundamental design issue from the outset that the IAF is nursing on this platform as of now...
I think you're reading way too much into the words "more processing capacity".
A newer fcc having more processing power does not mean the older one was struggling to keep the aircraft under control whenever the pilot started pulling Gs.
Mk1 already has a fully digital, quad redundant FBW system. DFCC has 4 computing channels, cross channel communication, redundancy management, failure detection and reconfiguration. They're constantly taking pilot commands and sensor inputs, running the control laws and sending the required commands to the flight control actuators.
Older Mk1 computer was based around the Intel i960 family of 32-bit RISC processors.
Mk1A is basically moving that old computing architecture to a much newer PowerPC based DFCC using MPC5566 processors. It is still quad redundant but now you've got considerably more computational headroom, faster I/O, a high speed autonomous state-machine I/O controller and newer DO-178C Level-A flight critical software.
More processing power here means more room for the software to grow. More control law functions can be added. More failure management logic can be accommodated. You can handle more interfaces and I/O, make future changes without constantly fighting the limits of an old processor architecture and generally give yourself much more room for upgrades over the aircraft's life.
It does NOT automatically mean old computer couldn't calculate fast enough when the aircraft manoeuvred hard.
A fighter's flight control computer isn't a gaming PC where you pull 8G and suddenly the CPU hits 100% and the frame rate drops. These are deterministic real time systems.
A FCC reads the pilot's commands and sensor data, runs the control laws, works out the required aircraft response, calculates the actuator commands, runs the redundancy and fault management logic and sends those outputs within a tightly defined time window.
Existing Mk1 control laws were designed, tested and certified to execute inside those timing requirements.
So if you're claiming the Dubai aircraft crashed because its flight-control computer was overwhelmed, then show the actual evidence of that.
Did the DFCC miss its execution deadlines? Did one or more channels drop out? Was there a watchdog reset? Was there a disagreement between the 4 channels? Did the system revert into some degraded flight control mode? Was there an actuator command problem caused by computational saturation? Did telemetry show control law execution overruns? Where is any of that?
As of now, none of it has been established. Mk1A has a faster processor isn't evidence of any of those things.
In fact, your claim that fighters don't normally receive more powerful flight control computers after their design is complete is just plain wrong.
Look at what BAE Systems is doing with the F/A-18E/F Super Hornet and F-15EX.
They're upgrading the actual FBW FCCs. Not the radar computer. The flight control computers.
And one of the explicitly stated reasons is
MORE PROCESSING POWER.
They're changing hardware and software, dealing with obsolescence and creating more capacity for future functionality. Super Hornet upgrade goes even further. They're adding another processor to its flight control computer specifically to provide additional processing capability for future functions.
So what do we conclude from that?
That the F/A-18E/F has spent decades flying around with a fundamentally underspecced flight-control system? That every time a Super Hornet pilot pulled hard G the old computer was struggling to keep the aircraft in the sky?
Obviously not.
The old system performs the job it was designed and certified to perform. The new computer gives engineers more room to do things they couldn't conveniently keep piling onto an older computing architecture.
Processor obsolescence is also a very real thing in military aircraft. These fighters remain in service for 30, 40, sometimes 50 years. Nobody seriously expects the processor architecture selected during development to remain state of the art for the entire life of the aircraft.
And ironically, bringing up the JF-17 actually makes your argument worse.
Early JF-17 blocks themselves didn't have the same full 3 axis digital FBW arrangement that Block III has. They used the earlier hybrid flight control arrangement.
Block III moved to a full 3 axis digital FBW system. That's a pretty major evolution of the flight control architecture itself.
So should I use your logic and say: JF-17 Block III needed full 3 axis digital FBW, therefore Block I was fundamentally underspecced and wasn't flying at its optimum performance?
Of course not.
Because that would be silly too. The requirements changed. Technology moved on. More capability became available. Aircraft evolved.
Same thing happened with JF-17's A2A refuelling capability.
It wasn't all there from day one. The refuelling capability came later with Block II, aircraft were modified for it and eventually the Block-II Configuration C aircraft received the capability.
Again, nobody sensible says that proves the original aircraft was incapable of flying properly. Then Block III comes along with AESA, major avionics changes, cockpit changes, EW/MAWS changes, weapons changes and the full 3 axis digital FBW setup.
That's normal fighter development. And that's exactly why this whole if you upgrade something later, the original design must have been fundamentally flawed argument doesn't survive its own JF-17 example.
Now come back to Dubai. You're linking a Mk1A FCCs upgrade to the crash of a Mk1. What's the evidence connecting those two things?
There isn't any at the moment. Look at what the aircraft was actually doing immediately before the accident. It was performing a very aggressive airshow sequence at extremely low altitude, including negative-G manoeuvring.
That's an entirely different environment. When you're doing that kind of flying close to the ground, altitude becomes your recovery margin. At 10,000 feet, if something doesn't go exactly according to plan, you've got thousands of feet to work with.
At airshow height, you may have secs.
Your entry speed matters. Your altitude matters. Your attitude matters. Your G application matters. Your G release matters. Your turn radius matters. Your energy state matters. Your nose position matters. Your roll state matters.
And the exact point at which you begin the recovery matters.
Be slightly lower than planned, slightly slower than planned, slightly late in changing the trajectory or end up with a slightly different attitude and the amount of height required to recover can change very quickly.
And that's before we even get into the other possibilities that an investigation has to look at: spatial disorientation, pilot input, physiological effects, control system problems, actuator problems, sensor problems, engine problems or some other technical failure.
That's exactly why low-level display flying is dangerous even in very mature aircraft.
F-16s have crashed at displays. F/A-18s have crashed during low-level demonstration flying. MiG-29s have crashed during displays. Sukhois have crashed during displays.
Plenty of aircraft with decades of operational history have been lost while doing this kind of flying.
That doesn't mean their CPUs became overwhelmed. Tejas was being deliberately flown through an aggressive negative-G display sequence close to the ground.
Air forces don't just let somebody turn up at an international airshow and improvise whatever manoeuvre comes into his head. Display routines are practised, worked up and flown within defined display parameters.
Tejas had also already gone through years and years of flight testing before this. Envelope expansion. High AoA testing. High-G manoeuvring. Flutter testing. Loads testing. Weapons separation and firing trials. Different stores configurations. Operational flying. Squadron flying. Aerobatic displays.
The whole purpose of flight test envelope expansion is to progressively push the aircraft through the combinations of speed, altitude, G, angle of attack, configuration and manoeuvre that it is cleared to perform.
If the flight control computer fundamentally couldn't keep up with the aircraft once manoeuvring became demanding, that's exactly the sort of flight critical problem you'd expect to start showing itself during the development and envelope expansion programme.
Tejas had been flying for roughly 24 years by the time of the Dubai accident and had suffered only two aircraft losses. That doesn't prove the aircraft is flawless. Nothing is.
And since we're apparently talking about fundamental design issues, let's look at the JF-17 with the same standard.
Its flight control architecture changed substantially between the earlier blocks and Block III. Its aerial refuelling capability was introduced later. Its radar changed. Its cockpit changed. Its EW setup changed. Its sensors changed. Its weapons integration expanded. Its flight controls evolved into full 3 axis digital FBW. Again, none of those things automatically means the original JF-17 was defective. It means fighters evolve. And then there's the RD-93. JF-17 is powered by a single RD-93 which comes from the Russian RD-33 family.
Pakistan has spent years trying to develop and improve the overhaul and maintenance ecosystem for those engines while the supply chain itself has always been a slightly awkward arrangement because you've got a Russian origin engine going into a Chinese Pakistani fighter programme.
Pakistan has even looked at alternatives over the years including the RD-33MK and Chinese WS-13 family. And if we're going to talk about engine reliability and supposedly fundamental engineering problems, the RD-33 family isn't exactly the hill I'd choose to die on. Look at what happened to the Indian Navy with the MiG-29K and its RD-33MK.
And remember, RD-33MK is a more developed member of the same engine family. Indian CAG documented dozens of those engines being withdrawn or rejected because of design related defects and deficiencies. It also recorded 10 single engine landings following in-flight engine problems. Russia had to identify a whole series of modifications to deal with the problems.
MiG-29K itself had other reliability headaches too including airframe issues associated with carrier operations and poor FBW reliability during the period examined by the audit.
And that's on a TWIN engine fighter. JF-17 is sitting behind one RD-93.
Now, does that mean I'm going to claim every JF-17 is inherently unsafe and its engine is going to explode?
No.
Because that would be exactly the same kind of lazy argument you're making about Tejas. Aircraft have problems. Engineers find them. Hardware becomes obsolete. Processors run out of spare..........................
@Nimble
