Now how are the aeronautical geniuses of this forum concluding that the "uncommanded pitch up" - 3 words in some article means that the air brake is too far aft of the CG?
Any aeronautical engineer, or for that matter any mechanics student who has read Ferdinand L Singer will confirm that the moment arm created by the airbrake not aligned with the CoG causes the pitch up.
If you don't know where the CG is…
The flight control computer’s job is to know where the CG is at all times. Otherwise how will it apply corrective inputs via FBW and keep the aircraft flying. If the Flight Computer doesn’t know where the CG is, the aircraft won’t fly in the first place.
From those I spoke to, the FBW is not able to detect and actuate the elevons well in time to correct. FWIW, the services do not consider this as a showstopper, and this is not considered either for IOC or FOC.
This was just an example of the complex FBW development process that could have been avoided using a proven technology for getting the aircraft in the air, and zero base FBW development could have commenced as an enhancement.
tsarkar ji, doors of the main landing gear were used as air-breaks in Gnat as well.
Agreed. However, the MLG doors do not just provide aerodynamic housing, but also protect the LG from the elements in flight. The 737 doesn’t have MLG doors, but the LG is designed for this. I was told moisture ingestion and icing of LG moving joints/parts as one of the possible side effects, if the aircraft flew into clouds and extended LG door.
What was different about their design considerations?
The F-18 has oversized stabilators and flight control surfaces for adequate flight control. Hawk airbrake might create a downward pitch, but the aircraft is designed to be very stable, since it’s a trainer.
Yeah..we know from reports (from a former IAF senior pilot) that even the F-16 Block 60 and Super Hornet didn't meet the IAF's STR requirements. Does that mean that if these were available for induction in the IAF, that the IAF would decline and reject them altogether? Very unlikely.
They were rejected for failing the technical evaluation, that included these very parameters. Your statement completely contradicts reality.
The F-16 was designed as a A2A fighter, and the bells and whistles added for A2G role ate away flight performance required for the A2A role.
The F-35 apparently doesn't meet its STR requirements, but is the USAF now insisting that the F-35 purchase be curtailed to a token order?
F-35 is worst aeronautical disaster in history and political pork barrel. Should we be going down the same route? What can one expect when Business Men / Managers / Politicians and their coterie run programs rather than engineers and aviators driving development.
It is mature and hasn't proven to be troublesome.
Then why can’t the FCS correct the uncommanded pitch created by the original airbrakes.
but that isn't the reason that the IAF is keeping Tejas Mk1 orders to 40
Agreed, from what I have been told, the IAF considers the pitch effect a nuisance but definitely not a showstopper. It has no effect on the induction plans.
What does the second statement even mean? What is a simpler design process?
Thank you for asking this question. It means assessing all the available means to achieve an end, and choosing the simplest and least riskiest means of achieving that end.
Like having airbrakes closer to CoG than having it elsewhere and having FCS mitigate any side effects. FWIW, using MLG door is reverting back to simpler design philosophy. Now, I am sure that the designers would have had some valid reason for not doing so in the first time itself, like avionics in the dorsal or fuel tanks in the ventral or wings, however, a simpler approach would have given precedence to placement of airbrakes.
Karan M wrote:
troubles with the MiG 21 are in this phase…
If you or I were to teach our young ones to drive using a Ferrari or a Shaktiman, I am sure they would not be able to handle the acceleration of the former and the momentum of the latter. Should we then say, “troubles with the Ferrari are in the acceleration phase” and “troubles with the Shaktiman are in the stopping phase” because we’re using them for a purpose they were never intended for?
Flying Officers just start OC flying. How many FLt or Sq Ldr or Wg Cdr crash while landing because they couldnt handle the landing speed, which all supersonic fighters of that era with high wing loading will have?
FWIW, Pakistani F-7 OC training crash rate is the same as India.
Issues with MiG-21 as an OC trainer is meaningless while discussing Tejas as a fighter.
Lastly, the reason I am saying all this is because of the misdirected angst against the user, who are doing all they can to support the program. But a basic performance level has to be met.
Which BR member will volunteer his son or father or brother or husband to go to fight knowing fully well they cannot outturn the enemy in a sticky situation? I am sure your perspective of “IAF not supporting…” will do an Immelman turn when your own flesh and blood goes to a fight in a Mk1.