Indian Military Aviation- September 29 2013

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Re: Indian Military Aviation- September 29 2013

Postby shiv » 01 Jun 2014 18:50

Pilots need to learn the conditions under which stalling occurs and then avoid those conditions. Secondly, if a stall does occur and the plane then falls into a spin they need to know how they might recover. from the spin

In general there are a few aircraft types (cannot recall names) which will never recover from a spin. On the other hand trainer aircraft are designed to recover predictably from a spin so that pilots experience the frightening and disorientating feeling of a spin and still have their wits about them to either conduct what needs to be done to recover, or if that does not work, eject appropriately.

Trainer aircraft must stall, spin and recover predictably.

Here is a fantastic article by Air Marshal Rajkumar about test flying the Alpha Jet and Hawk long before the AJT came and their stall/spin characteristics

http://vayuaerospace.in/images1/Advanced_Jet.pdf

Read it all - but here is a quote
The Hawk did not want to spin and one had to sit with prospin controls applied for several seconds before she dipped the nose and settled into what appeared to be a steep nose down corkscrew motion. Standard application of anti spin controls ensured quick recovery. After the Alpha Jet experience this was an unimpressive spin.

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Re: Indian Military Aviation- September 29 2013

Postby Victor » 01 Jun 2014 19:03

deejay wrote:If the aircraft is having problems in stalling…

There is no problem in stalling afaik. The problem is the plane tends to roll when stalled which in turn is caused by an "inherrent" design issue. I think I also read somewhere that the tail "is too high" or something to that effect. As mentioned above, it could very well be that the wing surfaces are inadequate to counter the inherrent roll. Just going by moments, it seems to me that if the wings were a little higher up and closer to the centerline, they would become more effective and may even reduce/eliminate the "tail too high" issue if that were indeed an issue. All beer and pakora theorizing onlee of course. Am sure BAE or someone will spill the beans if given enough crores and maska.

A plane can enter a spin without warning (ie. emergency manouvers, explosion nearby or even a missile hit) no matter how docile its "normal" handling and afaik, it is mandatory for all pilots to learn how to recover.

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Re: Indian Military Aviation- September 29 2013

Postby deejay » 01 Jun 2014 20:03

Victor saar I said "if the aircraft is having problems in stalling..."

I read some pages back on the thread that the aircraft was rolling prior to stall and therefore the pilots discontinued with the mission profile. This is because, while one may stall an aircraft at any pitch and/ or bank angle, here we are determining the stall characteristics of an aircraft, therefore we need to remain straight and level. At this point I would add that one may Google for definition and explanation of 'Basic Stalling Speed'.

Further, this aircraft will be spun after the stall. In spin, one needs to opt for either right spin, left spin and enter such a spin from a straight and level flight or one may get into an inverted spin and the fun of the roller coaster you enter magnifies manifold. This is especially important from a trainee POV. Remember, these pilots are pretty green behind the ears.

The 'Spin' process for a trainee is to get in a straight and level flight, proceed as one would for a normal stall and just at the point of stall you apply the chosen rudder to spin in the chosen side (left / right). The aircraft shall yaw in the chosen direction and then suddenly flip. Oh boy!. This flipping can be fairly violent and the spin thereafter is vaguely like a downward roller coaster ride (except mama earth approaches you fast) and then you recover after a few turns if you take the correct actions. The exact nature of spin may vary with aircraft.

Now how do you spin an aircraft in control when you can not control the roll at stall from a trainee POV? Since, the aircraft is in certification stage even experienced Test Pilots would prefer straight and level. Plus they would need to report the speeds, drop in altitude, other parameters and flight handling in a controlled situation. An uncontrolled roll is definitely not acceptable.

Why does it roll? I think the engineers at HAL are pretty clued up. I was once at their facility (long back) and I don't think we could second guess a problem which they cannot see. I have absolute faith in the HAL engineers and scientists. Its just that this stuff is so cutting edge. Things don't always pan out the way we plan.

Bradmins, if I have digressed from Topic please feel free to move / delete. I have tried to keep the procedure correct and brief, avoid aerodynamics AFAP. In case something important is missed/erred please correct.

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Re: Indian Military Aviation- September 29 2013

Postby Victor » 01 Jun 2014 21:27

On the contrary, its obvous that the HAL guys involved are not clued in, hence the BAE "experts". That call was a brave and prudent one as it helps no one to paper over these problems, least of all the kids who are expected to fly these things. If anything, the call for help came too late and now I am certain the IAF will get another IJT.

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Re: Indian Military Aviation- September 29 2013

Postby deejay » 01 Jun 2014 21:41

^^^ I was only refering to their know-how in general. Of course, the roll issue is causing heart burns at HAL. I just hope it is some minor issue which may be corrected with something like a few Votex developers placed correctly. If it is basic design flaw then we may be back to the drawing board. Me thinks the BAE guys are more for corrective action with minimum input then just for identifying the problem (I am guessing that at HAL, the folks probably have isolated the cause and they think it may be solved short term with BAE guys expertise which is why they are only thinking of short term/ one year delay and not longer).

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Re: Indian Military Aviation- September 29 2013

Postby Shreeman » 01 Jun 2014 23:09

rrao wrote:shreeman shiv sir, please catch hold of shreeman shreeman sirji and take him to HAL honcho. After all , a flurry of R&D agreements are being signed up with IITs these days by GMs. Shreeman sir somehow smells HAL to me..... :D


Matter is well outside my cave complex. I dont know what I am talking about. Seriously. My apiologies for smelling HAL.

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Re: Indian Military Aviation- September 29 2013

Postby Indranil » 02 Jun 2014 02:42

Lot's of theories. Some right, some wrong. Here are my thoughts:

Theory 1. Let the students learn recovery from flat spin on the PC-7 and the Hawk. Use IJT for every other role envisioned for it.
Does not work. Though stall and recovery from stall is taught at 1 G, it can happen at any speed. At 'n' gs, your stall speed is V1 * squareroot(n), where V1 is the stall speed at 1 G. This is called accelerated stall and can be encountered by student pilots during a moment of over-enthusiasm or panic. Therefore, they need to solve this problem. Somebody said that it might affect landing and take off. Till now, it hasn't. There seems to be enough cushion between landing and stall speed.

Theory 2. IJT has a big tail.
Big vertical tails are good for stability. The problem happens if the horizontal tail comes in the wake of the wing during stall. This is called a deep stall and generally occurs in T-tail configurations. This is a very dangerous condition and almost always results in the loss of the plane. There is no report of a deep stall for IJT. Looks unlikely to me.

Theory 3. Design flaw which should have been caught at wind tunnel testing. What about CFD?
Many phenomenons do not manifest on the wind tunnel model. This is called scaled effect. Sometimes, plane makers are in for a nice surprise when they fly the actual plane. For example the Su-27 flies at higher AoA than inferred from the wind tunnel models. And sometimes plane makers are in for a bad surprise, as in the case of IJT. Unfortunately, they can't put the real plane in a wind tunnel and study.
Well, why not use the virtual wind tunnel, aka CFD analysis. The problem is that this phenomenon is happening at near stall speeds, a time when the airflow is very turbulent. Simulation of this airflow needs enormous computing ability and CFDs are not very accurate in their predictions in this flight regime. My information is a little dated here. Any gyan from CFD experts?

Probably it is good case for testing on TBRL's new test track.

P.S.
Hakim, LCA LSP-6 was for high AoA testing. Though AoA and stall are deeply related, generally modern fighters reach their AoA limit much before their critical angle (AoA of wing at stall). For example Tejas may at most go to 28 degrees AoA, but it wing stalls at around 35 degrees AoA. Anyways, IJTs are now armed with spin chutes, a key feature of LSP-6. Let us wait and see what comes out of the testing.

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Re: Indian Military Aviation- September 29 2013

Postby chackojoseph » 02 Jun 2014 06:29

Stall and recovery are being done in gliders. I myself have done it on Rohini and Setberg back in 1980's. Spins are also being done on gliders. JMT.

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Re: Indian Military Aviation- September 29 2013

Postby Indranil » 02 Jun 2014 06:44

Of course. My reading of the news report is that they are worried to enter a stall with an uncommanded roll (quite naturally). They aborted the tests before inducing the inducing the spin.

May be with the guarantee of the spin chutes, they have gone further.

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Re: Indian Military Aviation- September 29 2013

Postby shiv » 02 Jun 2014 07:43

indranilroy wrote:Of course. My reading of the news report is that they are worried to enter a stall with an uncommanded roll (quite naturally). They aborted the tests before inducing the inducing the spin.

Yes. That was my reading too.

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Re: Indian Military Aviation- September 29 2013

Postby Austin » 02 Jun 2014 09:10

Updates on AL-55I Engine ( via keypubs )

http://bmpd.livejournal.com/776841.html

Development program to create the engine AL-55I

"Saturn" fulfilled the requirements of the Indian customer's resource jet engine AL-55 single-engine training aircraft for HJT-36, said the managing director of the association Ilya Fedorov.

"The engine is created, it has 300 hours, they have been confirmed in tests. We fully understand how to do 600 hours and 1200 hours. There is a margin to 6400 hours on the cold side and 4000 - by the hot part. This is something that asks the Indian side "- said Igor Fyodorov reporters at an international technology forum" Innovations. Technologies. production ", which opened on Tuesday in Rybinsk.

According to him, made a contract for the developmental work, in which the supposed increase engine life up to 300 hours and the delivery of a certain amount of products.

"Today is the engine for the Indian side is, we are willing to cooperate, will be a series of talks with Indian customers that will identify further ways of development of this engine. They want this engine and after negotiations it will become clear what to do next," - said Igor Fyodorov.

It is reported by the news agency "Interfax-AVN"

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Re: Indian Military Aviation- September 29 2013

Postby rrao » 02 Jun 2014 15:04

Image


IJT babies on parade!!! still we want to import?

tushar_m

Re: Indian Military Aviation- September 29 2013

Postby tushar_m » 02 Jun 2014 17:20

please add a bigger pic

from what i see there are 6 IJT's in the pic

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Re: Indian Military Aviation- September 29 2013

Postby Rahul M » 02 Jun 2014 17:35

somehow looks like PS to me. need bigger pic.

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Re: Indian Military Aviation- September 29 2013

Postby rrao » 02 Jun 2014 18:35

Image

https://www.flickr.com/photos/65231028@N03/14142606608/


cant do better than this! :(( !! Rahul ji !!! its up to you to believe or not. definitely not PS!!!

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Re: Indian Military Aviation- September 29 2013

Postby rrao » 02 Jun 2014 18:55

Image

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Re: Indian Military Aviation- September 29 2013

Postby Indranil » 02 Jun 2014 19:41

There you go.

Image

But where did you find this?

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Re: Indian Military Aviation- September 29 2013

Postby KBDagha » 02 Jun 2014 21:54

Looks like PS to me too..

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Re: Indian Military Aviation- September 29 2013

Postby Victor » 02 Jun 2014 22:20

Let's rock and roll baby :mrgreen:

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Re: Indian Military Aviation- September 29 2013

Postby member_26622 » 02 Jun 2014 23:18

Need some PS swiss cheese in the picture and IAF will start lapping it up.

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Re: Indian Military Aviation- September 29 2013

Postby NRao » 03 Jun 2014 00:21

The three guys - are they cardboard cutouts?






And, you mean to say that Russia actually supplied that many engines? Impressive.

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Re: Indian Military Aviation- September 29 2013

Postby Skanda » 03 Jun 2014 04:36

Narendra Modi govt to fast-track $1.5-bn deal, Army to get 197 light utility helicopters
Sources told FE that a fresh request for proposal (RFP) for the chopper deal will be issued by the new government within a month's time. Defence minister Arun Jaitley has already been been briefed about the delayed/on hold projects, including the procurement of the LUHs.

Once the RFP process is competed, it would take another two to three years before the first helicopter is delivered. The delays in the previous rounds of bidding have already hurt the army badly as it has been searching for a modern helicopter to replace the aging Cheetah/Chetak helicopter. Most of these are already running on an extended lease of life and need immediate replacement.

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Re: Indian Military Aviation- September 29 2013

Postby Indranil » 03 Jun 2014 04:37

Though this picture looks photo-shopped to add the guys in the front, I wouldn't be surprised to know that there are 6+ planes in the air now. LSP-5 flew in the last week of Sept last year. Add PT-1 to this and you have 6+ planes flying now.

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Re: Indian Military Aviation- September 29 2013

Postby rrao » 03 Jun 2014 13:41

indranil the original pic was taken from pdf copy image .i enlarged it to full screen and with a camera i took a photo shoot(pS) of my computer screen and later you pasted the correct size.Thanks for that. otherwise the pic is genuine!!!no PS!!!!
now coming to the point the tail of IJT is high... The intakes are above the wings and not in-line as seen with hawk AJt. I think Alpha AJT uses two LARZACs with bigger air intakes and the wings are drooping!!! so these variations does make some aerodynamic difference. IJT resembles polish IRYDA M93 a bit!!!

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Re: Indian Military Aviation- September 29 2013

Postby Kartik » 03 Jun 2014 14:04

NRao wrote:The three guys - are they cardboard cutouts?


:rotfl:

I cannot even imagine how on earth that picture came about into existence, its that bad!

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Re: Indian Military Aviation- September 29 2013

Postby uddu » 03 Jun 2014 14:59

Hope in the near future all exercise with foreign air forces will see the participation of Tejas. :)

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Re: Indian Military Aviation- September 29 2013

Postby rrao » 03 Jun 2014 16:30

kartik ,i dont think there is any necessity for HAL CO to circulate PSed photos to its Engineers!!! As i explained the original picture was of thumb nail size. i enlarged it and took a photograph of it..in that process the contrast got lost and you are seeing three card board cutouts!!!
N rao sirji, have some faith in HAL!!! its not all that bad!!! The It-vity style has spoiled HAL work culture!!! IJT is bad and HAL is bad ,Reliance is good ,I am hearing these things since quite long. i was wondering what is basically wrong with the IJT and i just wanted to hear some analytical comments from our Gurus here!!! Hope my anguish is heard!!!

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Re: Indian Military Aviation- September 29 2013

Postby jamwal » 03 Jun 2014 18:12

rrao,
Take a screenshot instead of taking picture of screen with a camera.

http://www.wikihow.com/Take-a-Screensho ... ft-Windows
http://www.take-a-screenshot.org

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Re: Indian Military Aviation- September 29 2013

Postby Austin » 04 Jun 2014 15:06


shiv
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Re: Indian Military Aviation- September 29 2013

Postby shiv » 04 Jun 2014 17:38

rrao wrote: i was wondering what is basically wrong with the IJT


As far as my knowledge goes the IJT, provided the Russians have sorted out the engine - is fine for many aspects of initial jet training. However it is not yet proven for stall and spin recovery training. So far it has been flown only by test pilots and there have been 3 incidents/accidents. Two involved the late Baldev Singh - including an incident at Aero India when the canopy was not locked and it flew off. I think the plane itself was recovered in both these instances.

The most serious incident was a crash in which both pilots bailed out and IIRC that crash had something to do with the Al 55 engine - maybe someone who remembers the details can correct or corroborate. It was after that incident that we saw a clampdown on news until now - we suddenly see 6-7 IJTs in a photo.

As I said - the plane does fly and I think there is even a simulator for it (I have flown that simulator for a few minutes)
http://www.youtube.com/watch?v=KFjX3d1nwPU

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Re: Indian Military Aviation- September 29 2013

Postby Austin » 04 Jun 2014 18:17

IIRC the single IJT crash was attributed to pilot putting the IJT into High AoA or Spin/Stall and could not recover from it , which subsequently lead to stopping of IJT flights.

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Re: Indian Military Aviation- September 29 2013

Postby rrao » 04 Jun 2014 18:42

shiv sir, Thats very nice video of IJT during Aero India show. The IJT looks deceptively small, but actually its as big as the Hawk... Two accidents, aircraft survived and the third one aircraft perished and as far as the tragic fourth one Late Baldy sir left for an untimely heavenly abode!!! Austin sir you are spot on!!! I too heard the same thing!!!

why cant scaled down RC models of IJT,LCA and SARAS be made and flight performance to some extent be evaluated? The YAK130 with micro turbo engines resembles the original one!!! companies like TAAL, NAL and IITs and university students can make these RC planes...of course making them is not an easy one with available tech resources!!!





P.S : i came across one youtube video of LCA RC plane made by IISc students!!!

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Re: Indian Military Aviation- September 29 2013

Postby vsunder » 04 Jun 2014 19:36

@rrao. This is not a new idea for India. In fact the legendary designer Kurt Tank built full scale glider models that he flew himself for almost anything he designed. He built a full scale glider model of the HF-24 that he wanted to fly himself over the Bangalore skies, much to the astonishment of HAL engineers, who tried to dissuade him from flying the plane himself. The argument was if Tank died there would be none to continue the project. Eventually Tank relented. 1:10 scale models were also tested in the IISc wind tunnels for low speed handling, while at high speeds I think V.M. Ghatage had to go to Switzerland(??) to use wind tunnels there. I have photographs of this HF-24 glider flying. In fact some of you may have the entire chapter with many photographs, abstracted from a large book on Kurt Tank. I recall several of you asked me for a scan of the chapter of Kurt Tank in Bangalore. I suppose computational power has reached the point when people feel more confident with numerical simulation.
Last edited by vsunder on 04 Jun 2014 19:53, edited 3 times in total.

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Re: Indian Military Aviation- September 29 2013

Postby shiv » 04 Jun 2014 19:40

Austin wrote:IIRC the single IJT crash was attributed to pilot putting the IJT into High AoA or Spin/Stall and could not recover from it , which subsequently lead to stopping of IJT flights.


Wasn't this because of engine packing up or some such thing?

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Re: Indian Military Aviation- September 29 2013

Postby NRao » 04 Jun 2014 19:51

I suppose computational power has reached the point when people feel more confident with numerical simulation.


That is what a "5th Gen" plane is. A mathematical model that is designed to reflect very little and (nearly as an after thought) is able to fly. Much as the F-16 was a "brick" that flew.

That said, I am not sure where India stands in this world. But, I am fairly confident they are not shabby - to say the very least.

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Re: Indian Military Aviation- September 29 2013

Postby vsunder » 04 Jun 2014 19:59

@Nrao: That is what I was saying earlier, transmission eigenvalues, "reflects very little" all EM waves gets transmitted, little scattering. Eigenvalues are the frequency if you wish of the scanning radar.
USAF is dumping lots of money for this sort. No India in CFD is not shabby, but various groups do not talk to one another, that is the rub.

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Re: Indian Military Aviation- September 29 2013

Postby Philip » 05 Jun 2014 09:53

Funny.If the IJT survives and is passed by the IAF,it will further validate Russian engines,which many have tried to discredit despite they being used and manufactured for the MIG-29,MKIs,etc. without any problems! If it is dumped,and there is a possibility that it may happen if by Dec. IOC isn't attained,it will be a major setback for HAL. It will also bring into Q HAL's ability to deliver on its share of the FGFA,if it is both cash strapped and (human) resource strapped. Some time ago,due to the shortage of HR,the IJT team was double tasked with that of the FGFA! If it is dumped,what should our plan "B" be? Whom have the IAF shortlisted?

The priorities for HAL should firmly be on the the LCA,getting MK-1 with its underpowered GE engine for which 40 have been ordered in to series production asap,as we are told that the definitive production version is nearing completion,all prototypes thus far differ from each other to an extent.Another 40MK-1s should be ordered,so that there is a long run until the definitive Mk-2 with its more powerful engine (hopefully,if it doesn't also put on too much extra weight) also enter series production. One would still like to see the GOI/MOD build extra prototypes of MK-2 with alternative engines (EJ,SNECMA,whatever) just in case the 414 fails to deliver after the modifications to Mk-1.Increased production rates may also require a second manufacturing centre,esp. if the MMRCA fructifies and HAL will be overwhelmed with aircraft orders for new aircraft plus upgrades.

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Re: Indian Military Aviation- September 29 2013

Postby Kartik » 05 Jun 2014 10:06

Philip wrote:Funny.If the IJT survives and is passed by the IAF,it will further validate Russian engines,which many have tried to discredit despite they being used and manufactured for the MIG-29,MKIs,etc. without any problems! If it is dumped,and there is a possibility that it may happen if by Dec. IOC isn't attained,it will be a major setback for HAL. It will also bring into Q HAL's ability to deliver on its share of the FGFA,if it is both cash strapped and (human) resource strapped. Some time ago,due to the shortage of HR,the IJT team was double tasked with that of the FGFA! If it is dumped,what should our plan "B" be? Whom have the IAF shortlisted?



wait wait..so if the IJT makes it, it will validate Russian engines ?! The MTBO of the Al-55I is in the lower hundreds and you're telling us that entering service will validate Russian engines? What about the delays it has caused, which I've never seen you criticise while you rail against HAL on other aspects? What about the fact that the IAF will NEVER accept the IJT as long as the Al-55I has such pathetic overhaul requirements ??

if it is dumped, the lion's share of the blame will go to the rather poorly thought-out decision to go for the totally unproven Russian engine and an substantial portion of the blame will also be apportioned to the Russian side for the delays and the rather unbelievably poor and low MTBO specs.

So if it makes it, credit to the Russians, if it doesn't blame HAL for a poor design. Nice.

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Re: Indian Military Aviation- September 29 2013

Postby RKumar » 05 Jun 2014 12:28

Philip wrote:One would still like to see the GOI/MOD build extra prototypes of MK-2 with alternative engines(EJ,SNECMA,whatever) just in case the 414 fails to deliver after the modifications to Mk-1


:eek: :eek: :eek:

:rotfl: :rotfl: :rotfl:

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Re: Indian Military Aviation- September 29 2013

Postby shiv » 05 Jun 2014 19:01

Here is the story of a plane that rolled before stalling because one wing stalled before the other
http://www.ntsb.gov/doclib/reports/2012/AAR1202.pdf
Gulfstream did not determine (until after the accident) that the cause of two previous uncommanded roll events was a stall of the right outboard wing at a lower - than - expected AOA. (Similar to the accident circumstances, the two previous events occurred during liftoff ; however, the right wingtip did not contact the runway during either of
these events.)


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