Military Flight Safety

[cbelwal]

Actually the forward velocity of the craft is also used to open the shute. This is more applicable when ejection happens at a very low altitude. The seats seem to eject at an angle which is approx 110 degree to the forward motion. Watch this slow motion video capture:

http://www.youtube.com/watch?v=MgcPhl1UIhA

Let me explain what I think I know know. A "zero-zero" ejection seat works at both zero altitude and zero speed - which means that the seat is boosted up to an altitude that allows the parachute to billow and fill with air to ensure a safe landing. All parachutes need a certain amount of free-fall descent before the parachute fills and becomes effective.

[A Sharma]

Su 30 MKI fleet remains grounded, checks on

Sources familiar with the investigation say that the fighter, which was flying as part of a four-aircraft group at over 20,000 feet, went into an involuntary ‘bunting’ manoeuver that tossed it around at an angle of 270 degrees.

Following the violent manoeuver, the fighter plummeted to the earth in an uncontrollable spin and did not respond to controls, forcing the two pilots to eject. An official said that this could point to either a technical fault or some sort of structural damage to the fighter.

[sum]

What is a "Bunting" manoeuvre?

[Shameek]

Sources familiar with the investigation say that the fighter, which was flying as part of a four-aircraft group at over 20,000 feet, went into an involuntary ‘bunting’ manoeuver that tossed it around at an angle of 270 degrees.

Earlier reports mentioned 'few minutes after takeoff'. This one seems to paint a different picture. Also, earlier it was mentioned that the aircraft was guided to a vacant spot. This one says it did not respond to controls. Guess we need to wait for further details before we know more.

[Arun_S]

What is a "Bunting" manoeuvre?

Looks like a nose down, Negative-G manoeuvre.

See link.

[Surya]

these are nonsense DDM reports

samples

- few minutes after take off , something wnet wrong

- aircraft was on a routine flight and exploded


best things is to be calm, pray for the pilots and families and wait for more details from IAF.

[skher]

http://www.hindustantimes.com/StoryPage ... c327b2bd98

Jaisalmer (Rajasthan), May 02, 2009
First Published: 14:08 IST(2/5/2009)
Last Updated: 14:10 IST(2/5/2009)
IAF team recovers black box of Sukhoi

An investigation team of Indian Air Force has recovered the black box of Sukhoi-30 MKI fighter jet that crashed near Rajmathi village here on Thursday killing a pilot.

The black box was recovered from the wreckage of the aircraft on Friday. It is expected to detect the exact cause behind the crash, sources said on Saturday.

The Su-30MKI from one of the squadrons based in Lohegaon near Pune had crashed near Jaisalmer leaving a pilot dead and another injured.

The two were on a routine sortie after participating in an exercise in Pokhran ranges when the mishap occurred.

As the aircraft was flying, the pilots sensed trouble and after reporting it, successfully ejected out of the aircraft.

However, rescue teams found one of the pilot seriously injured on the ground and rushed him to a military hospital, where he was declared dead.
http://www.hindustantimes.com/StoryPage ... c327b2bd98
© Copyright 2007 Hindustan Times

[neerajb]

What is a "Bunting" manoeuvre?

In the Bunt, you pushed the nose down, past the vertical and still further, until you were in horizontal inverted flight, and came out on the other side and rolled it out.

http://www.bharat-rakshak.com/IAF/Histo ... R-FIS.html

Cheers....

[JaiS]

IAF seeks Russian help in Sukhoi crash probe

IAF denies grounding Sukhoi fleet

[shiv]

http://www.bharat-rakshak.com/NEWS/news ... wsid=10799

Air Chief Marshal F H Major described the crash as ‘bizarre’ when asked about the possible cause of the accident on the sidelines of a defence function on Tuesday. Another top officer said the Air Force was ‘confounded’ by the way the fighter crashed after going out of control last week.

Clearly something really odd has happened. The plane has just gone out of control. I am rminded of those NatGeo aircrash investigation programs that have come up with oddball chance events (and sometimes maintenance issues) that have led to mysterious crashes. Like the sensor that got frozen up with ice or the rudder that that suddenly developed a mind of its own. Not to forget the real life Jaguar hydraulics story that is on BR.

[putnanja]

‘Fly by wire’ fault may have led to Sukhoi crash

...
“It is very difficult to imagine that the fly by wire system could have collapsed just like that, given that it was backed up four times independently. However, this was a very strange crash and this seems to be a probable explanation,” an expert said.


...

[shiv]

‘Fly by wire’ fault may have led to Sukhoi crash

...
“It is very difficult to imagine that the fly by wire system could have collapsed just like that, given that it was backed up four times independently. However, this was a very strange crash and this seems to be a probable explanation,” an expert said.


...

Well if proved - it won't be the first time FBW with tripe/quadruple redundancy has failed. Other examples exist eg the A 320 crash at the airshow IIRC and one of the Gripen prototype crashes. A unique condition of failure of some sensors along with some other failures could do peculiar things.

[Rahul M]

from the above article :

However, the sudden and involuntary 270 degrees ‘bunting’ manoeuver that sent the fighter into an uncontrollable spin leading to the crash has led experts to consider a malfunction in the system.

we don't know the height at which this occurred, nor the speed, but if this happened at a low altitude as mentioned in some reports, then the fact that even one pilot survived is a matter to be thankful about.

[neerajb]

The article mentions that MKI was cruising at over 20000 feet when the incident happened. It is safe to assume that it would be doing around 0.8 - 0.9 Mach at that time. What I feel is the aircraft went into the bunt maneuver involuntarily and went into a spin at almost 90 degree nose up attitude after having done 270 degrees in pitch plane. I guess the plane lost airspeed and altitude abruptly and quickly since the rate of rotation of aircraft in pitch is greate when it is pulling +ve gs than when it is pulling -ve gs. The slower rotation of plane through 270 degrees would have caused airspeed and altitude loss abruptly. Then the aircraft went into a spin at low altitude/speed and nose up attitude with both pilots having very less time to respond.

Cheers....

[Rahul M]

I am not an expert but the phrase "sudden and involuntary 270 degrees ‘bunting’ manoeuver" brings to my head images of the a/c abruptly going nose-down (if 90 degree is nose-up, 270 degrees is nose-down) and going into spin thereafter.
it may not be maneuver through 270 degrees.
may be the gurus can answer better.

[neerajb]

My interpretation says, AC is level flying. Suddenly it's nose starts dropping down untill it's in 90 degree nose down attitude. It further carries on with the involunantary bunt maneuver till it's upside down (180 degrees) and pointing opposite to the original flight heading. It further pitches down till the nose is up at 90 degrees (270 degree) and stalls.

Since the elevator travel is less for pitching down then pitch up (assuming FBW failure and no structural damage), the aircraft rotates slower and looses lots of altitude before stalling. I guess that could be a possible reason for pilots ejecting at low level.

Cheers....

[shiv]

I don't know enough about even elementary aerodynamics to comment - but that never prevented me from doing so.

I am guessing that there are two control surfaces that can start off a bunting maneuver if those surfaces go out of control.

The most probable one is the tailplane. If the tailplane suddenly decides to lock into an "up" position - it will send the plane into an uncontrollable bunting maneuver until the loss of lift is bad enough to set up a spin and perhaps flame out the engines.

I was wondering if a "down" position of the canards could do the same on their own - but I think that will merely pitch the nose down and end the plane into a steep but controllable descent. Just my guess.

But a combined movement of tailplane up and canards down would probably produce bunting.

If it happened suddenly - I am sure the sudden G forces would themselves have temporarily disorientated the pilots. Frightening and sad.

[tsarkar]

The inherent issue with unstable / relaxed stability aerodynamic configuration like Su30MKI and LCA is a dependency on flight control system. Normal planes with positive stability like a Kiran or MiG 21 will have a tendency to return to stable flight whenever the error control input is rectified.

However a Su30 MKI is unstable in its longitude while the Tejas in its vertical. Hence its the flight control computer that flies that plane rather than pilot inputs to control surfaces. It is practically impossible to validate control laws for every aerodynamic possibility. So the flight control computer isnt 100% error free for any unstable aircraft. That is the reason why LCA testing is taking so long and would need Boeing/EADS support.

So in the case of flight control failure, there is not much that a pilot can do to aerodynamically control the plane. All he can hope is that he's providing the right inputs to the flight control computer and that the computer listens to those inputs. However if the computer decides to do something else based on its control laws, then all a pilot can do is eject.

I'm speaking from memory rather than research here, so not everything may be 100% accurate.

[Vinod Ji]

I am complete novice so take what I write with a shipload of salt.

Could it have been Russian sending a message to India? I have read that all manufacturer put a trojan.

[Shameek]

^^ A trojan that kills a pilot? That would be murder dude. And also one of the worst marketing tactics to advertise the safety and reliability of a sophisticated aircraft. And the message you speak of being 'Buy our aircraft and we will randomly kill your pilots?'
Lets not go into conspiracy theories here. The facts by themselves are shocking enough.

[chetak]

So in the case of flight control failure, there is not much that a pilot can do to aerodynamically control the plane. All he can hope is that he's providing the right inputs to the flight control computer and that the computer listens to those inputs. However if the computer decides to do something else based on its control laws, then all a pilot can do is eject.

I'm speaking from memory rather than research here, so not everything may be 100% accurate.

tsarkar ji

The FBW system on the MKI has quad redundancy. All four channels are not the same either in software or hardware. Very remote chance of complete FBW failure. Even assuming complete FBW failure Why would the aircraft bunt? the control surfaces would more likely freeze rather than result in a run away situation.

The pilot would still have had limited TVC.

Quote
Also the relatively conservative Sukhoi flight control system philosophy, which combines manual, analog and digital systems with simple back-up modes, such as the manual mode for the TVC system which returns control of the deflection angle to the pilot.

Quote:

Su-30MKI
The Su-30MKI aerodynamic configuration is an unstable longitudinal triplane. The canard increases the aircraft lifting effectiveness. It deflects automatically and allows high angle-of- attack flights. The integral aerodynamic configuration combined with thrust vectoring results in practically unlimited manoeuvrability and unique taking off and landing characteristics.Stability and control are assured by a digital FBW.

Su-30MKI has no AOA limitations which gives advantage to pilot in deploying weapons in any direction.
Quote:
The term "super-maneuverability" was coined by Dr. Wolfgang Herbst, initiator of the USA's X-31 prototype program, in defining controllability up to 60° to 70° Angle-of-Attack with transients of 120° or more.The Su-30MKI has no AoA limitations: it can fly at even 180 degree AoA and still recover. This high super-agility allows rapid deployment of weapons in any direction as desired by the crew. The addition of another seat means that the pilot is free to concentrate on flying the aircraft while the second pilot can engage targets

The Su-30MKI is a highly integrated twin-finned aircraft. The airframe is constructed of titanium and high-strength aluminium alloys. The engine nacelles are fitted with trouser fairings to provide a continuous streamlined profile between the nacelles and the tail beams

For flight control, reliability and survivability, the aircraft has a FBW with quadruple redundancy. Depending on the flight conditions, signals from the control stick position transmitter or the automatic FCS will be coupled to the remote control amplifiers. Upon updating, depending on the flight speed and altitude, these signals are combined with feedback signals fed by acceleration sensors and rate gyros. The resultant control signals are coupled to the high-speed electro-hydraulic actuators of the stabilizers, rudders and the canard.

The Su-30MKI is powered by the Al-31FP (P for povorotnoye meaning "movable"), which is a development of the Al-37FU (seen in the Su-37 Terminator). The Al-37FU (FU stands for forsazh-upravlaemoye-sopo or "afterburning-articulating/steerable-nozzle") basically added 2D Thrust Vectoring Control (TVC) Nozzles to the Al-31F. 2D TVC means that the Nozzles can be directed/pointed in 2 axis or directions - up or down. TVC obviuosly makes an aircraft much more maneuverable. Al-31FP builds on the Al-37FU with the capability to vector in 2 planes i.e. thrust can be directed side-ways also. The nozzles of the MKI are capable of deflecting 32 degrees in the horizontal plane and 15 degrees in the vertical plane.

The aircraft is capable of near-zero speed airspeed at high angles of attack and super dynamic aerobatics in negative speeds up to 200 km/h.

http://www.defencetalk.com/forums/air-f ... 0mki-3383/

http://www.sci.fi/~fta/Su-30.htm

[chetak]

I am complete novice so take what I write with a shipload of salt.

Could it have been Russian sending a message to India? I have read that all manufacturer put a trojan.

Trojans in aircraft embedded systems?

Different channels of the FBW system will run different software on different hardware all doing the same job. The Su system would at the very least be running two totally different and fully independent hardware and software systems. Individual channels are also independent thereby providing the quad redundancy.

[tsarkar]

Chetak - You're right in your description of how the flight control would work. However, if there is a flaw in the control law, then hardware like quad channels cannot compensate for it. Because the logic inside the computer is reading the data provided by the quad channel incorrectly. Or sending incorrect responses to the control surfaces via the quad channels.

The logic in the flight control computer is constant irrespective of the parameters measured by the sensors and conveyed by the redundant channels. Even if there are two computers, they'll have the same control laws coded into them.

The critical issue is when the flight control system believes it is doing the right thing and refuses to take inputs from the pilot. In all 4 gen planes, the pilot provides input to the computer and its the computer that flies the plane. Unlike older planes like MiG 21, the stick doesnt directly connect to the flaps or rudders. There is a bloody computer in the middle.

"Stability and control are assured by a digital FBW" works fine when the logic inside works the way its supposed to. For a 38 tonne plane, its simply not possible for manual stick to drive large hydraulically driven control surfaces that probably weigh a tonne each. Or without FADEC, a simple throttle cannot control 120 kN engines. For example, on older planes like MiG 25, the engines took time to respond to pilot controls. In Su 30, the engines respond near real time with precise thrust adjustments.

http://en.wikipedia.org/wiki/Aircraft_f ... ms#Digital

The fly-by-wire flight control system eliminates the complexity, fragility and weight of the mechanical circuit of the hydromechanical flight control systems and replaces it with an electrical circuit. The cockpit controls now operate signal transducers which generate the appropriate commands, that are in turn processed by an electronic controller. The autopilot is now part of the electronic controller.

A digital fly-by-wire flight control system is similar to its analog counterpart. However, the signal processing is done by digital computers and the pilot literally can "fly-via-computer".

As the computers continuously "fly" the aircraft, pilot workload can be reduced. It is now possible to fly aircraft that have relaxed stability. The primary benefit for military aircraft is more maneuverable flight performance and so-called "carefree handling" because stalling, spinning and other undesirables can be prevented.

I am speculating here, but all indicators in this crash point to a computer inability to control the plane and pilot inability to control via the computer, probably because the computer believed what it was doing was right and refused to accept pilot inputs.

[bala]

Strange and mysterious causes could have another explanation: willful sabotage. There are numerous cases of such activity. Sullying the name of the SU-30MKI could have many subscribers and they will spare nothing in achieving their goals.

[chetak]

Strange and mysterious causes could have another explanation: willful sabotage. There are numerous cases of such activity. Sullying the name of the SU-30MKI could have many subscribers and they will spare nothing in achieving their goals.

A likely possibility may be the failure or faulty inputs of some sensors ( inertial / vertical reference ?) feeding into the FBW system. IMHO, the bunt suggests some sort of uncommanded canard involvement seeing as to how fast the situation developed.

There is heightened security and increased surveillance everywhere in the Forces due to our dear neighbors. Notwithstanding the vigilance, sabotage will be one of the most crucial points being investigated.

[chetak]

I am speculating here, but all indicators in this crash point to a computer inability to control the plane and pilot inability to control via the computer, probably because the computer believed what it was doing was right and refused to accept pilot inputs.

tsarkar ji,

software ??

Its quite likely that the FBW software had not caused any incident until the crash, and the problem was therefore unknown till now.

Without pointing fingers, this by itself does not imply that the problems were the error of the software developers. They were most likely due to anomalies in the analysis and maybe formulation of system requirements. The MKI aircraft as well as its subsystems is very highly developed and has undergone rigorous multiple levels of testing. Notwithstanding, the problems if any, may not have been found because the tests did not cover the specific conditions that caused the failure. The lack of test coverage implies incomplete requirements specification because compliance with every stated requirement must be established by at least one test, if not more.

To be fair, it must be clear that it is very difficult to specify requirements for all abnormal situations that an aircraft or a control system may encounter. Single failure modes that arise
within the subsystem are usually well understood by the designer. But multiple failures that can happen are less clearly understood, often subject to varied interpretation and they can lead to unexpected and dangerous results.

Additionally, the subsystems don’t operate in isolation and there are multiple interactions with other subsystems. Experience shows that initiating events that are often not the classical computer hardware or sensor failures but interactions between abnormal states in several subsystems. Such interactions occur much less often than conventional failures but practically they do occur and are therefore not inconceivable.

Such conditions may not always result in triggering a warning to the crew either via the caution or warning systems.

A rigorous requirement for testing of every possible fault condition of a flight critical system with each of the (im)possible fault states of every interfacing function may be unaffordably expensive but a systematic approach may have been adopted for assessing the cruciality of possible interactions of fault states that may occur across systems and functions.

Obviously in such a systemic approach scenario , some conditions will get missed out because the aircraft and its subsystems have grown past the initial system requirements and the manufacturers may have been lulled into a sense of comfort because of the undoubtedly excellent safety record of the aircraft while testing and certifying software upgrades.

just my two bits

[JaiS]

Russian experts to investigate Su-30 jet crash in India

NEW DELHI, May 8 (RIA Novosti) - A group of Russian experts has arrived in India to look into the cause of a recent Su-30MKI fighter jet crash, a source in India's Defense Ministry told RIA Novosti on Friday.

An Indian Air Force Sukhoi-30MKI crashed on April 30 during a routine training flight near a village 170km from the town of Jaisalmer in the northeastern state of Rajasthan, killing one of its two pilots.

The source said 20 Russian experts arrived on Wednesday at the crash site to examine the wreckage of the plane. The incident was the first since the Su-30MKI was put into service with the Indian Air Force in 2002.

[chetak]

Russian experts to investigate Su-30 jet crash in India

NEW DELHI, May 8 (RIA Novosti) - A group of Russian experts has arrived in India to look into the cause of a recent Su-30MKI fighter jet crash, a source in India's Defense Ministry told RIA Novosti on Friday.

An Indian Air Force Sukhoi-30MKI crashed on April 30 during a routine training flight near a village 170km from the town of Jaisalmer in the northeastern state of Rajasthan, killing one of its two pilots.

The source said 20 Russian experts arrived on Wednesday at the crash site to examine the wreckage of the plane. The incident was the first since the Su-30MKI was put into service with the Indian Air
Force in 2002.

JaiS ji,

This will be a very expensive affair.

The russians would have given a fantastic quotation in dollars for the investigation teams visit to India and the Indian authorities would have had no option but to accept the quote prior to the russian team's departure, given the circumstances.

[sum]

The source said 20 Russian experts arrived on Wednesday at the crash site to examine the wreckage of the plane.

Team of 20?

[kobe]

Russians are keen to show some "customer service" in light of the MRCA competition, so I don't think they are stupid enough to send a expense report to IAF for those who arrived for investigating the MKI crash. There are many other ways to recover the expenses.

[JaiS]

JaiS ji,

This will be a very expensive affair.

The russians would have given a fantastic quotation in dollars for the investigation teams visit to India and the Indian authorities would have had no option but to accept the quote prior to the russian team's departure, given the circumstances.

chetak ji,

IMO, the need of the hour is to home into the real cause of the accident as soon as possible, and all efforts to that effect are welcome. Whether the Russians have charged a high amount for this team/investigation, is something which I prefer not to comment about, till I have seen the figures for the same.

[chetak]

JaiS ji,

This will be a very expensive affair.

The russians would have given a fantastic quotation in dollars for the investigation teams visit to India and the Indian authorities would have had no option but to accept the quote prior to the russian team's departure, given the circumstances.

chetak ji,

IMO, the need of the hour is to home into the real cause of the accident as soon as possible, and all efforts to that effect are welcome. Whether the Russians have charged a high amount for this team/investigation, is something which I prefer not to comment about, till I have seen the figures for the same.

JaiS ji,

Of course we need to urgently get to the cause of the tragedy.

The quotation figures will not come out in the public domain.

Going by past experience, gora accident investigation teams come pretty expensive and also they tend to blur the findings if intricate design aspects are involved. They will always carry away much more information from the crash than they will give you.

[chetak]

Russians are keen to show some "customer service" in light of the MRCA competition, so I don't think they are stupid enough to send a expense report to IAF for those who arrived for investigating the MKI crash. There are many other ways to recover the expenses.

I appreciate what you are saying but there is always a financial implication when such teams come to investigate.

It has always been so, its not a new procedure being followed now.

"Expenses" are not just an expense report for the team. Even though this will be a major amount, its chicken feed compared to the rest of the expenses.

It is also for the investigation, deployment of forensic resources back in russia, chemical and metallurgical analysis, flight parameter simulation and reconstruction of accident as best as possible.

A number of Sukhoi flight simulators may have already begun to try to fly the fatal sortie based on best inputs available trying to induce a similar failure. They would have to reprogram extensively to simulate multiple subsystem involvement and sensor inputs to induce some sort of catastrophic failure response. Simulator time costs a bomb! These software guys also don't come cheap. Experienced test pilots are also not given to working for free.

Russian test pilots who will form part of the investigating team will be most anxious to get to the bottom of this mystery.
They may have already asked Sukhoi test pilots to investigate some aspects on the factory Sukhois back in russia. Each sortie will cost tens of thousands, including instrumentation and all.

Other Su 30 operating airforces would also be anxious.

Money is not the major issue here. The reputation for reliability is.

The GOI will gladly pay the expenses and hope for a very early closure.

[putnanja]

Saras crash probe yet to progress

...

The NAL remains tight-lipped on the progress made in the probe. However, sources said the DGCA held a meeting in the national capital last week to discuss the progress achieved in the course of investigations that is yet to be completed.

Director General of Civil Aviation (DGCA) Dr S A Nasim Zaidi who spoke to Deccan Herald over phone from New Delhi on Tuesday said, “Data from the flight data recorder and voice cockpit recorder is being analysed on a day-to-day basis. We have not arrived at any conclusion yet as to what could have caused the crash. All angles are being explored. There is no deadline to complete the investigation”

...

[narayana]

History Repeats

MiG-27 aircraft crashes, 7 injured

A MiG-27 fighter aircraft on a routine sortie crashed in a village in this district on Friday, injuring seven persons on the ground.

[Shameek]

Very unfortunate. I am sure the media is rubbing their hands at the prospect of pointing fingers at the IAF again. I have noticed how the reports begin with "Yet another.... crashes". That in itself tarnishes the image of the IAF in the eyes of the common public.

[sum]

History Repeats

Sorry but what does "History repeats" mean?

[shiv]

Very unfortunate. I am sure the media is rubbing their hands at the prospect of pointing fingers at the IAF again. I have noticed how the reports begin with "Yet another.... crashes". That in itself tarnishes the image of the IAF in the eyes of the common public.

This is an astute observation. It indicates a mindset that thinks that there are buffoons and incompetents about whom the journalist has a right to make comments. And that itsel;f serves as an excuse for Indians journalists to be completely ignorant.

And why not. They get paid whether they know anything or not.

[Shameek]

^^ Sadly enough their ignorance is never pointed out to the common public. Even the report of the current accident on IBN had a picture of five Jaguars flying with a caption naming them as MiG 27's. This is why the common public has little idea about our armed forces. The DDM feed off this ignorance knowing that they can pass judgements on anything they want even if they can't distinguish a MiG 21 from a Boeing 747. And in doing this they ensure that the public attention is focussed on their 'scoop' about the "deficient" IAF standards and not the quality (lack of) in their reporting.

[Arun_S]

History Repeats

MiG-27 aircraft crashes, 7 injured

Sorry but what does "History repeats" mean?

That people will breath again in next 2 seconds is repetition of history.
That some person who is born will also die some day is repetition of history.
That cars that are sold on Indian soil some of them will be wrecked in accident is also repetition of history.

Narayan: Please share some gems on where the history does not repeat!
Or do you wish to withdraw your "History Repeats" pontification?