A Tale of Two Hydraulic Systems

shiv
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A Tale of Two Hydraulic Systems

Postby shiv » 05 Nov 2002 13:45

This is an article that appeared in "INDIAN AVIATION" in August 2002, authored by Wg Cdr K.S.Suresh.

JAGUAR AIRCRAFT HIGH VOLTAGE DRAMA : AS IT PLAYED ITSELF OUT

Wg Cdr KS Suresh VrC (Retd) describes an unusual situation and how a Jaguar aircraft was saved with high degree of professionalism and quick thinking

Introduction.

Jaguar a twin engined strike aircraft, jointly developed by British and French entered service in the mid seventies. Jaguars are operating in India, Ecuador and Oman besides UK and France. Indian Air Force (IAF) acquired the Jaguars in 1979 to meet the Air Staff Requirement (ASR) of Deep Penetration Strike Aircraft (DPSA). To speed up induction, pending manufacture and supply of "Jaguar International" meant for the IAF, aircraft from the Royal Air Force (RAF) were released to equip the first two squadrons of the IAF. As the strength of IAF's own Jaguars built up progressively, RAF aircraft were returned. Jaguars of the IAF are fitted with two Rolls Royce Adour Mk 811 engines. Hindustan Aeronautics Ltd (HAL) also started producing Jaguar aircraft and Adour Mk 811 engines, under a Licence Agreement. Aircraft produced within the country were inducted to augment the direct supply Jaguars and form additional squadrons. HAL has produced more than 100 aircraft so far and the production run continues. The very first innovative and bold move made by the IAF was, to replace the old generation Navigation Attack System with a state of the art system called the DARIN. The architecture and the software of the new system were entirely Indian.

IAF had no serious problems with the Jaguars, for over a decade, barring a few unavoidable accidents. There is an old saying, ?every aircraft, after about 10 to 15 years of use, irrespective of thought and care during the design stage, presents an unusual problem, that could not have been foreseen?. This statement is substantiated when history of different aircraft is examined. Serious problems had occurred on most of aircraft, world over, usually after about a decade of service exploitation.

In the year 1993, after the IAF had operated the Jaguars for about 14 years, a very serious problem occurred. This emergent situation was something that had never been foreseen or anticipated and was also not listed as an emergency.

Brief Description of Jaguar Hydraulic System.

A brief description of the aircraft system is necessary to follow the events. Jaguar has two independent hydraulic systems, Hyd-1 and Hyd-2, each having a reservoir with a capacity of 6 litres. The two systems are energised by engine driven pumps of respective engines and are independently capable of operating all the services and flying controls. The services include, flaps, slats, airbrakes, undercarriage, wheel brakes, etc. System design is such, that the two systems do not meet and have no common pipelines. The hydraulic system also has necessary back up in accumulators and emergency electrical pump. In the event of hydraulic fluid leak, as the level in the reservoir drops to 1 litre, a solenoid-operated valve is energised electrically, to stop fluid supply to the services. This residual fluid of 1 litre is now available exclusively for the primary flying controls, to ensure that the aircraft can be flown safely away from populated areas and also avoid possible unusual attitude prior to ejection. In the Jaguar aircraft, the slats (leading edge high lift devices) can be selected to operate automatically and depending on the prevailing flight condition, slats take up appropriate position. They can also be operated manually. The slats are operated by an electric motor (slat motor) and its engagement and disengagement is through a hydraulic brake. The body of brake unit receives hydraulic fluid under pressure from both No 1 and No 2 hydraulic systems, to ensure uninterrupted operation of the slats, even if one of the hydraulic systems fails. It is this design feature that takes away the redundancy of the duplex hydraulic system in case of a mechanical failure, like breakage of the brake body of the slat motor.

First Accident.

On 22nd November 93, at Air Force Station Ambala, Jaguar No JS 120 (a direct supply aircraft) flown by Fg Offr Pareek was on a routine training flight. After about 35 minutes of flying, the pilot noticed that the hydraulic pressure for operating the "Services" was 'zero' in both the systems. However, the hydraulic pressure for operating the "Controls" was normal. He returned to base and found that the undercarriage could not be lowered and all other services like flaps, slats and airbrakes were inoperative. An emergency was declared and on advise from the ground, the pilot tried all known methods to lower the undercarriage. The wheels just did not come down. He had flown close to 90 minutes and was desperately short of fuel and all attempts to get undercarriage down had failed. Since belly landing of Jaguar is not permitted as per Pilot?s Operating Manual, the pilot ejected safely and was quickly picked up by the rescue helicopter. Aircraft was destroyed in the accident. Air Headquarters (Air HQ) ordered a court of inquiry and at their request, two HAL engineers were deputed to be members to assist the investigation. The inquiry team also had members from Government departments - Directorate of Aeronautics and Directorate of Technical Development & Production (Air), besides the regular complement of IAF officers.

I being in-charge of Flight Operations and Safety at HAL Corporate Office, responsible for interaction and co-ordination with operators on safety matters, was in touch with our specialists on the progress of the investigation. After about two weeks, the investigation was still inconclusive but I learnt that several improbable theories were being put forward. It was necessary to correct these distortions. At that stage, I was confident to the extent of saying that the accident certainly had not happened the way it was being visualised by the court. I immediately mobilised support of my colleague, Head of Quality Assurance at HAL Corporate Office, Mr GS Jamadagni (Jam). He and I had been working as a team for over five years and had tackled many problems. We complemented each other's efforts, had excellent coordination and working relationship. The very first thing we did was to visit the factory and study the Jaguar Systems thoroughly. We then requested Air Vice Marshal (AVM) Bharat Kumar (Bharat), Officiating Inspector General IAF at Air HQ to permit us to interact with the court of inquiry, mainly to correct distortions and facilitate possible explanations for the accident. Bharat readily agreed to our proposal, as he was also not happy with the progress of the investigation. Thus the entire inquiry team (about to submit its report) was held back at Ambala (weekend ruined). They were asked to await our arrival and have brainstorming sessions with us.

Suspense at Air HQ.

Jam and I left Bangalore for Delhi on Monday, 13th December 93 by the morning flight. We were to meet Bharat at Air HQ and then proceed to Ambala in the evening. As we reached Air HQ at about 1130 hrs, we were asked to rush to the office of Assistant Chief of the Air Staff (Operations) (ACAS (Ops)). On reaching there we found that the atmosphere was very tense and ACAS (Ops), AVM Nadkarni, was talking to Ambala. Bharat and other senior Air Force officers connected with Jaguar were also present. There was a communication patch up with Ambala. It transpired that another Jaguar aircraft (JS 139 - HAL manufactured aircraft) flown by Sqn Ldr K Palit (Palit), Flight Commander of the squadron and a test pilot, had a problem exactly like that of JS 120; "Services pressure zero", "Controls pressure normal" and not able to get the undercarriage down. At that very moment, he was still in air, having flown close to 85 minutes and making attempts to get the wheels down. Air Officer Commanding (AOC), Air Force Station, Ambala and his team were at the Flying Control advising the pilot to try various methods. Air HQ had even contacted the Original Equipment Manufacturer (OEM), British Aerospace (BAe) for a possible solution. ACAS (Ops) had kept the Chief of the Air Staff (CAS) informed about the situation. As the time passed, fuel state was getting lower and lower. AOC Ambala called to say that the pilot was being advised to eject and that the rescue helicopter was already airborne. After this, there was an eerie silence; unbearable suspense and seconds appeared to be hours before the next communication. All of us heard with joy that the aircraft had landed safely with minor damage. There was no time to get the details, as we had to rush to Ambala along with Bharat and Air HQ team. At Ambala, we learnt the sequence of events leading to the relatively safe recovery of the aircraft.

Recovery.

At the end of 95 minutes, the situation was desperate, as all attempts to lower the undercarriage had failed. The AOC who was at the flying control, in sheer desperation sent word for the HAL specialists (part of JS 120 investigation team) told them that "the aircraft has about 3 minutes of fuel left, suggest anything, even the most ridiculous thing, I will ask the pilot to try it before he ejects". One of the HAL engineers, Mr Jayamohan who had his thinking cap on, quickly came out with a solution, "advise the pilot to put OFF the battery, explaining that this would de-energise the solenoid-operated valve and the trapped fluid would then be available to operate the services. There would be no instruments, lights and radio for a short duration and aircraft may yaw a bit. Battery could be put ON after hearing the thud of the undercarriage coming down".

This was precisely what the pilot was asked to do. At this stage, Palit had about 170 kgs of fuel and in terms of duration, just about 3 minutes. He carried out the drill as advised and heard the thud of the undercarriage coming down. Aircraft, which was very light at that fuel state, developed a pronounced yaw (due to small differential in wheels coming down) and Palit put the battery on. The main wheels had locked down, but the nose wheel, which was in the process of coming down, remained half cocked, as the fluid reverted back to controls once the battery was put on. The nose wheel of the Jaguar extends forward, against the airflow and thus takes a while longer. Palit had no fuel to try the procedure once more; he did a quick turn and with his experience and finely honed skill of a test pilot, landed the aircraft safely on the reciprocal runway. He held the nose up as long as he could, used the tail chute and then gently lowered it on to the runway. Aircraft came to a stop with minimum damage to the nose area. One of the engines flamed out during landing run, as the aircraft ran out of fuel.

Observations on JS 139.

We found that the aircraft had been cleared off the runway and parked in the dispersal. It had been quarantined for investigation by specialists from BAe, who had been specially requested to come down to India. In order to preserve the evidence, we were allowed to make external observations only. We found that there were telltale marks of profuse hydraulic fluid leak on the left hand side of the fuselage. Origin of leak could be traced to the panel housing the slat motor. On opening the panel, we found that the brake unit body of the slat motor had cracked resulting in profuse hydraulic fluid leak. Slat motors had been manufactured by AVIACA France, a sub-contractor of BAe. As mentioned in the previous paragraph, the aircraft had minor damage to its nose section.

Four specialists from BAe arrived at Ambala on the 19th of December and left on the 23rd to be back in UK for Christmas. During their stay, they made extensive notes on all their observations and spoke to the pilot and maintenance crew. They were noncommittal on the possible cause of twin hydraulic failure, an unusual problem. BAe team stated that they would study the problem after they got back to UK and then respond. IAF had to take stock of the situation and introduce interim measures as it was clear that breakage of brake unit body of slat motor could cause rapid leakage of hydraulic fluid from both the systems (operating at a pressure of 3000 psi), leading to the situation encountered in both the accidents. Since the failed brake units had done more than 1000 hrs (About 1700 and 1400 hours respectively), as a first step, flying on aircraft fitted more than 1000 component hours was suspended. Action was initiated to procure and replace these slat motors. This measure reduced the availability of aircraft. Air HQ also issued instructions to manage the emergency, should it occur, by resorting to putting off the battery. This severely limited operations at night and in bad weather, as putting off the battery would take away the instruments, lights and radio.

Indian Efforts.

As explained above, since there were serious limitations to unrestricted operation of the aircraft and no tangible solution was forthcoming from BAe, we had to do something. There were several insinuations from BAe: IAF aircraft were being subjected to excessive number of cycles of slat operation. Strictures were passed on IAF maintenance practices, permitting entry of air into the system, during the process of charging hydraulic fluid. The first allegation of excessive slat operation was negated after our Air Advisor in London checked with the RAF and found that their slat operation cycle was identical to that of IAF. The second allegation was negated after it was pointed out that the Jaguar had a self-bleeding hydraulic system and there was no scope for air remaining within the system.

Bharat from Air HQ exhorted HAL to study the whole problem and come up with quick solutions, so that the aircraft could be cleared for unrestricted operations at the earliest. The damaged slat motor of JS 139 was brought to Bangalore for detailed metallurgical examination at National Aerospace Laboratory (NAL). By now it was clear that the accident of JS 120 could also be due to the same reason. On our request the wreckage (of JS 120) was searched again and the damaged slat motor located and brought to Bangalore. Jam put in relentless effort to analyse the cause of failure by interacting continuously with metallurgists of NAL and scientists of Aeronautical Development Agency (ADA). Detailed analysis was made using ELFINI, structural analysis software. It was found that the brake body of the slat motor had inadequate corner radius (by design) in the body unit, at the circlip holding groove, resulting in a sharp corner, leading to be a stress raiser. This component was prone to early failure even with normal load and duty cycles. The corner radius of 0.01 mm to 0.1 mm was permitted as per design. Jam and his team of scientists then worked out the duty cycles obtainable at different radii. Calculations revealed that even under normal operating conditions, units with corner radius of less than 0.03 mm were likely to fail prematurel,y around 1500 flying hours. This was precisely what had happened in both the accidents.

Jam presented the detailed analysis to BAe who were very reluctant to accept the findings. After a number of meetings and presentation of accurate facts and figures, BAe did accept the shortcoming. In the meantime, BAe had also examined RAF aircraft with about 1500 flying hours and found that the brake bodies of slat motors with lower corner radius showed signs of impending failure. BAe then took action to correct the design requirements and advise AVIACA accordingly. The reluctance on the part of BAe was probably to avoid any liability or legal hassles. We had learnt our lesson at the cost of one aircraft and almost another one.

Modifications.

There were a number of brainstorming sessions at the Aircraft Division of HAL to develop and introduce suitable modifications. The aim being to clear the aircraft for unrestricted operations by being able to manage the emergency, should it recur. The first modification was the introduction of a warning light on the Central Warning Panel (also wired to the Master Warning Flasher), to come ON the moment the reservoir levels dropped, consequent to a hydraulic fluid leak This was relatively easy and Mr Veluswamy, Design Engineer came up with trumps in no time. The second and most important part was to be able to use the residual fluid to lower undercarriage without putting off the battery. Jam came up with a concept; ? why not selectively de-energise one of the solenoid-operated valves, so that the fluid trapped exclusively for controls from one of the systems could be diverted to operate services like undercarriage. Controls could still be operated with the fluid from the other system?. This idea took shape and with tremendous encouragement from Mr Haridas, then General Manager of Aircraft Division and Bharat from Air HQ. Veluswamy, Rajshekar, Jayamohan and the team of the Division came up with a viable modification scheme. An additional switch was provided in the cockpit, which enabled the pilot to selectively isolate one of the hydraulic systems and divert the fluid for services, while the other system took care of the controls. Aircraft could thus operate unrestricted, as it was not required to put off the battery.

Both the modifications were rigged on one aircraft in record time, (less than two weeks). These were assessed and evaluated by HAL test pilots. In early February 94, Bharat and a team from Air HQ came to Bangalore and assessed the modifications. Aircraft and Systems Testing Establishment (ASTE) was also involved at this stage. Air HQ gave a go ahead to fabricate the required components and introduce the modifications on the Jaguar fleet of the IAF. HAL undertook the task on priority, sent teams to Jaguar operating bases and the entire fleet was modified within six weeks. The limitations on Jaguar operations were removed by April 94. In June 94 it was found that BAe introduced these modifications as applicable to the Jaguar fleet all over the world. Interestingly the Company Notice of BAe was identical to that of HAL, word for word; expect that the letters BAe substituted letters HAL. There was a very fine print (visible only through a magnifying glass) that the modifications were based on ?work done by HAL?

Contract.

Since the modifications were developed in India and adapted by BAe, it was decided to examine the possibility of claiming "Intellectual Property Rights" from them. Some interesting features of the Jaguar contract and licence agreement signed in 1978 by Government of India with the BAe emerged. The gist without actual legal terminology is given below:

Operator (India) may introduce modifications on their own aircraft, the details of which are to be communicated to BAe. If we (BAe) have any technical observations, we will inform you within two months. In any case, the introduction of modification is at your own risk and cost.

If we (BAe) find that the modification is useful and should be introduced on the entire Jaguar fleet world over, we shall do so. However, this does not attract any "Intellectual Property Rights" or Commercial considerations.

It is amazing that the contract signed even before the aircraft were inducted had incorporated clauses as above. We learnt that a team of experts specialised in drawing up contracts draft these documents and bring to them the desired thoroughness.

Awards.

Mr Jayamohan and Mr Jamadagni were commended by the CAS. HAL management gave a cash award to Jayamohan and very reluctantly promoted him (he had less than year?s service at that stage). Jayamohan?s role had been invaluable. It was his accurate analysis, commitment, intimate knowledge of the Jaguar systems and clear headed thinking during crisis, that saved an aircraft. It also provided material evidence for identifying the exact cause of the problem and take corrective actions. He for one certainly deserved a National Award. Sqn Ldr Palit kept his cool throughout the 97 minutes he flew and displayed a very high degree of professionalism and airmanship in bringing back the aircraft safely. He richly deserved the award of Vayu Sena Medal.

The others from Aircraft Division like Haridas, Veluswamy, Rajshekar who burnt mid night oil remained unsung heroes. An irony that has baffled me for years; HAL management did not recognise the role and contribution of Jamadagni in solving the unusual Jaguar problem, although he had earned a commendation from the CAS. It was only in April 2002, that the present Chairman, HAL honoured him at a small function.

Conclusion.

There are a number of lessons to be learnt from the Jaguar crisis described in this article. These are:

No design is foolproof. There would always be surprises in aviation.

No problem is insurmountable, provided it is tackled with purpose and synergy, setting aside narrow organisational loyalties.

Jayamohan's timely advise during the crisis, has once again reinforced the fact that there is no substitute to thorough professional knowledge.

The thoroughness with which BAe drew up contracts is to be admired. Hopefully our experts have learnt to be as thorough.

© Copyright Wg Cdr KS Suresh VrC (Retd). All rights reserved

shiv
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Re: A Tale of Two Hydraulic Systems

Postby shiv » 05 Nov 2002 13:51

I have photos of the Jaguar aircraft in question - supplied by ..who else?

Sanjay Simha

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Re: A Tale of Two Hydraulic Systems

Postby Jagan » 05 Nov 2002 13:54

Shiv,

Pictures Pictures!

-Jagan


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Re: A Tale of Two Hydraulic Systems

Postby davidn » 05 Nov 2002 14:39

OMG! :eek:

They weren't kidding when they said minimal damage, that pilot must have been one hell of a flyer.

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Re: A Tale of Two Hydraulic Systems

Postby SK Mody » 05 Nov 2002 16:13

The article reads like a first rate thriller with some shocking bits:

Operator (India) may introduce modifications on their own aircraft, the details of which are to be communicated to BAe. If we (BAe) have any technical observations, we will inform you within two months. In any case, the introduction of modification is at your own risk and cost.

If we (BAe) find that the modification is useful and should be introduced on the entire Jaguar fleet world over, we shall do so. However, this does not attract any "Intellectual Property Rights" or Commercial considerations.
Reminds me of the blurbs that have to be read when installing software from Microsoft. So add Microsoft also to the list of companies whose contracts are to be emulated.

The feature of these companies that draw up such cold hearted contacts is that the legal department is totally separate from the rest of the company. The employees who actually work on the company's products are totally insulated from this legal packaging and that I think is what enables these watertight contracts - humans are not supposed to have any hand in it :D . I wonder what the situation is in India in this respect.

Regards,
Sandeep.

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Re: A Tale of Two Hydraulic Systems

Postby JCage » 05 Nov 2002 16:34

Shiv,
Thanks!The original story was itself hair raising.All kudos to the gutsy pilot SqnLdr Palit :) and the HAL techs without whom the plane would have been lost.
Would love to see more articles like this.All this investigation of minute facets of the a/c by Indian specialists is always ignored and no-one ever gets to know the work put in by the Indian side,both the IAF and their support structure-HAL,NAL,ADA.Kills the canard/whining that they are useless,at any rate.

Superb read!

Regards,
Nitin

PS:Kapil,if you're on this thread,you lucky bugger,from the horse's mouth eh?... :)

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Re: A Tale of Two Hydraulic Systems

Postby JCage » 05 Nov 2002 16:36

Originally posted by davidn:
OMG! :eek:

They weren't kidding when they said minimal damage, that pilot must have been one hell of a flyer.
Right on.The pics are superb,are they not?

Regards,
Nitin

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Re: A Tale of Two Hydraulic Systems

Postby nathan » 05 Nov 2002 17:12

So the problem was the faulty design of the brake unit body. Indian solution was to add a warning light and a switch to redirect fluid when the need arises. My question is why didn't India also do a third improvement, that being redesign of the brake unit body too? Anyway the whole time I was reading this article I was thinking how the LCA must be really good because India also did focuses research for LCA on a component by component basis. LCA should be probably the best aircraft of its class in the world.

By the way did you guys read that article about a new material being developed from ancient texts which is invisible to all radar. I really hope India puts that material on its LCA, MCA and HCA, and also on all Navy ships. Just as West keeps its engine and other tech closely guarded secrets, India should do the exact same with its own developed techs so it has advantages over other nations of the world.

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Re: A Tale of Two Hydraulic Systems

Postby shiv » 05 Nov 2002 17:53

Originally posted by davidn:
OMG! that pilot must have been one hell of a flyer.
Those who saw the 2001 Aero India show would have seen the Jaguar flown by Wg Cdr Palit - who also attended the BR meet along with Wg Cdr Suresh and Rakesh Sharma and others and the story was related there first.

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Re: A Tale of Two Hydraulic Systems

Postby shiv » 05 Nov 2002 18:01

Originally posted by nathan:
So the problem was the faulty design of the brake unit body.
The exact fault is given here (quote from article)

It was found that the brake body of the slat motor had inadequate corner radius (by design) in the body unit, at the circlip holding groove, resulting in a sharp corner, leading to be a stress raiser. This component was prone to early failure even with normal load and duty cycles. The corner radius of 0.01 mm to 0.1 mm was permitted as per design. Jam and his team of scientists then worked out the duty cycles obtainable at different radii. Calculations revealed that even under normal operating conditions, units with corner radius of less than 0.03 mm were likely to fail prematurel,y around 1500 flying hours. This was precisely what had happened in both the accidents.
Apparently this part had been manufactured by a French company to which the work had been subcontracted.

This story illustrates something that I never tire of repeating. Aircraft have little parts that we cannot even imagine and some of thes eparts can be crtitcal. The actual part may cost only $2 or $10, but setting up a manufactiring unit for JUST THAT SINGLE PART will make the whole venture very expensive. Hence people import parts. In this case BAe had a French subcontrctor.

When we talk of local manufacture - we still cannot set up factories for every single part and critical little ones will have to be imported. THAT is the crunch. That is what we let ourselves in for when we say "Let us make the Rafale" or something.

I think this story should go in the BR archives as a permanent reference.

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Re: A Tale of Two Hydraulic Systems

Postby Jagan » 05 Nov 2002 18:07

I think this story should go in the BR archives as a permanent reference.

Amen!

Can we have permission to use it as we have done with the other articles?

regards

Jagan

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Re: A Tale of Two Hydraulic Systems

Postby shiv » 05 Nov 2002 18:11

Originally posted by Jagan:
[

Can we have permission to use it as we have done with the other articles?
Yes of course Jagan - only, we need to acknowledge the author AND say that this article first appeared in Indian Aviation.

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Re: A Tale of Two Hydraulic Systems

Postby daulat » 05 Nov 2002 18:12

don't forget that the Jaguar was an anglo french programme and that all aircraft programmes have one (in this case two) prime contractor(s) and hundreds of tier one contractors and thousands of component suppliers. many of the suppliers would have been of necessity French in origin (or indeed American)

the jaguar undercarriage was designed by hispano-suiza if i recall correctly, who are a reputable manufacturer of aircraft landing gear systems. BAe and Aerospatiale would never have designed the details of the landing gear itself, apart from setting out the system parameters that someone like a Hispano-Suiza would have to conform to. What happens inside the box is H-S's concern

fatigue problems are complex to find yet simple to resolve once you know which component is actually going to fail and what mechanism of failure is to be expected. unfortunately it often takes a catastrophic failure in order to locate the problem

the article also seems to imply that IAF jaguars are seeing more flying hours than RAF or Armee de l'Aire jaguars hence finding of the problem earlier

AFAIK RAF jags also crash 'frequently', usually due to low cloud and high hill and distracted pilot at 100' AGL errors

any reports on jaguar ops during Kargil?

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Re: A Tale of Two Hydraulic Systems

Postby Aditya G » 05 Nov 2002 18:37

Daulat: the article also seems to imply that IAF jaguars are seeing more flying hours than RAF or Armee de l'Aire jaguars hence finding of the problem earlier
excellent observation! :roll: but maybe it was the local climate which caused it earlier on? Though I am not sure how the "the brake body of the slat motor" will be affected due to the climate.

WTF is a "the brake body of the slat motor" anyway? :confused:

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Re: A Tale of Two Hydraulic Systems

Postby dsandhu » 05 Nov 2002 19:46

Shiv
Thanks for the article and pictures

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Re: A Tale of Two Hydraulic Systems

Postby Sribabu » 05 Nov 2002 19:52

Originally posted by aditya.g:
Daulat: the article also seems to imply that IAF jaguars are seeing more flying hours than RAF or Armee de l'Aire jaguars hence finding of the problem earlier
excellent observation! :roll: but maybe it was the local climate which caused it earlier on? Though I am not sure how the "the brake body of the slat motor" will be affected due to the climate.

WTF is a "the brake body of the slat motor" anyway? :confused:
Aditya,

If you read Daulat's comment carefully, he says the RAF jags crash due to completely different reasons.
AFAIK RAF jags also crash 'frequently', usually due to low cloud and high hill and distracted pilot at 100' AGL errors

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Re: A Tale of Two Hydraulic Systems

Postby Raman » 05 Nov 2002 20:44

Originally posted by shiv:
Originally posted by davidn:
[b]OMG! that pilot must have been one hell of a flyer.
Those who saw the 2001 Aero India show would have seen the Jaguar flown by Wg Cdr Palit - who also attended the BR meet along with Wg Cdr Suresh and Rakesh Sharma and others and the story was related there first.[/b]
Yup --- there's a picture in the BR jaguar pages of him in a grey jaguar, brake chute out.

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Re: A Tale of Two Hydraulic Systems

Postby Sridhar K » 05 Nov 2002 21:22


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Re: A Tale of Two Hydraulic Systems

Postby Jagan » 06 Nov 2002 00:12

Another time, another pilot, same type of aircraft, same type of situation.

http://www.bharat-rakshak.com/Temp/Anindo.jpg

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Re: A Tale of Two Hydraulic Systems

Postby JTull » 06 Nov 2002 01:58

Amazing story! :eek:

This goes to show the quality of experience with IAF and how it rubs off on younger blood.

Also reinforces the need for training on easier to handle aricraft (AJT?) before more punishing ones such as Mig21.

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Re: A Tale of Two Hydraulic Systems

Postby ramana » 06 Nov 2002 01:59

This is a classic example of a successful Failure Anaysis and Corrective Action in the aerospace industry. It shows the far reaching impact of problem - potential grounding the Jaguar fleet with impact to Operational readiness of the Air Force in times of crisis. It shows the importance of multi- disciplinary teams in resolving problems - Flight Controls (Jayamohan), Structural Analysis (using ELFINI), Systems Engineering, Quality Assurance and the Customer. The role of the last cannot be over emphasized. The IG of the IAF is the crucial link. Had he been non-pragmatic the whole thing would have been a disaster. He understood the impact and supported the team in exploring all possible causes and determine the root cause. The quick thinking by Jayamohan and the implementing of his idea by the AOC saved the aircraft and permitted a through investigation. On an aside it shows the importance of deep knowledge of the aircraft systems for trouble shooting emergencies and such knowledge is acquired by life long assignment to particular systems. Jayamohan was one year from retirement. Last but not the least - good liason/interface between the Customer and Contractor- Wg. Cmdr. Suresh. Someone who has good rapport with the Customer and sees their viewpoint and conveys it elegantly to the contractor.

Once the aircraft was available it required very short time to identify the problem and determine a corrective action. Here again the importance of multi- diciplinary teams cannot be over emphasized. I disagree with the term 'insinuations' for characterizing the possible causes. All causes are valid till proven otherwise. That is how one comes to finding the root cause.

All aerospace problems need short term and long term fixes. The first to restore fleet availablity and the latter to restore reliablity. Discovering the problem was fatigue related helped in providing a short term fix - allow flying aircarft under 1000 hrs service and switching off battery power. Short term measures are implemented till the corrective action is determined and implemented. The article would be enhanced if a failure analysis chart was included to show the systematic apporach used to find the root cause.
The Corrective action is also typical of the aerospace industy of belt, suspenders and rope to hold up the trousers. The warning light is the belt and the modification to the hydraulic system was the suspenders. In addition the rope would be to fix the drawings to limit the corner radius of the retaining ring groove.

The implentation is typical of the aerospace industry. The trial or proof of concept vehicle was ready in two weeks and the corrective action demonstrated. This action was reviewed by the IAF (Customer Review) and accepted. The fleet implementation was rapid and took five months from the first crash to final completion. In terms of problem solution (Feb 94) to final completion (April 94) was only two months. Thats rapid in any book. And on BAe 's part to issue the modifications in June 94 was also significant.

The BAe behavior is to be expected. Its not their headache for there are no contract penalties for non-performance or negative incentives. Moreover their reluctance to accept the problem could be due to the not invented here syndrome in addtion to contract ramifications. Besides a good IITM graduate is worth a ton of BAe/Western experts!

The article is very good and if enhanced with a failure analysis chart will be useful in providing a roadmap to solve most problems. The article could have wider audience if trade specific terminology were avoided. For example instead of 'brake body of slat motor' use ' structural housing of the brake for the slat motor' and use ' switch battery power off' instead of 'put off the battery'. But that is the old Wren and Martin in me!

On the matter of incentives and rewards am sure the team felt quite happy for solving the problem so throughly and teaching the BAe experts a thing or two. Money is nice but for an engineer solving the problem and using the skills learned over a lifetime is worth more. But HAL could have been more generous for its bacon was saved by these engineers.

I suggest that this article be sent to AIAA journals after suitable vetting by local IISC profs and getting rid of unnessary details.

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Re: A Tale of Two Hydraulic Systems

Postby Umrao » 06 Nov 2002 02:27

Fantastic story. Very interresting for engineer turned DOO like me.
Those of who attended the (small) Ann Arbor meet will recall the same analysis (with all due modesty) by your s truely on a 63 tonne press involved in a shop floor accident ( the stress concentration part on the radius of curvature at the the shaft changing in dia).

I have couple of questions

1) Why is the landing gear not spring loaded against hydraulic pressure? Ie the the hydraulic pressure should oppose the spring force which should default to deploy mode?

2) Why are the hydraulic systems driven by main engines, what if the engines fail? Is there a battery powered hydraulic pump back up?

I have to read many more times.
Reminds me of Fredrick Forsythe "The Sherpard"

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Re: A Tale of Two Hydraulic Systems

Postby SRay » 06 Nov 2002 02:31

Jagan, great story as well...! this is definitely turning out to be a thread to archive.

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Re: A Tale of Two Hydraulic Systems

Postby Umrao » 06 Nov 2002 02:33

also note the luck of the same problem occuring while investigation of the first was in progress.

This is extremely important as a team was already analysing the problem and has been in place while the next one occured.

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Re: A Tale of Two Hydraulic Systems

Postby Jagan » 06 Nov 2002 15:42

Tailpiece.

JS-139 is said to be the same aircraft that crashed earlier this year in which Fg Offr Palarwal lost his life

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Re: A Tale of Two Hydraulic Systems

Postby ramana » 06 Nov 2002 23:46

Jagan are we sure for that would mean the a/c has seen quite a few hrs in flight?

Also what does this mean? and why doesnt the chronolgy talk about the Nov. 93 crash as documented by Wg. Cdr. Suresh?

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posted 06 November 2002 09:13 AM
--------------------------------------------------------------------------------
NDTV.com - Latest News from India

Jaguar crash embarrasses IAF, Fernandes calls meet

Vishnu Som

Wednesday, November 6, 2002 (New Delhi, Ambala):

Defence Minister George Fernandes has called a high-level meeting of
Indian Air Force officers on November 8 to review why crashes are
taking place with such regularity in the country.

"It was an accident," said Fernandes referring to the Jaguar crash,
which took place on Tuesday in Ambala Cant.

"We will also go into the maintenance aspect of the fighter planes.
The Jaguar is the safest plane in Indian Air Force," he added.

Official version of crash

The Air Force says the fighter took off at 3:20 pm (IST)
from Ambala and within moments of take-off, the plane went
into a roll after a possible control systems failure.

The pilot sent out a distress call to the Air Traffic
Control, which never lost sight of the jet.
The Jaguar managed to reach a height of 300 feet at which
stage the pilot ejected.

The plane then crashed into a residential area near the air
base.

Unlike the MiG-21, which has serious engine defects, Jaguars
have crashed for a variety of reasons - from technical
defects to blatant pilot neglect.

Black box found

The Indian Air Force officials investigating the crash of the Jaguar
fighter-bomber in Ambala have also recovered the black box of the
plane.

The box contains a flight data recorder, which contains valuable
information on what went wrong with the aircraft, moments before the
pilot had to bail out.

Meanwhile, the toll in the crash has risen to six with two more
persons succumbing to injuries today.

Past crashes

In August 1990, two Jaguars collided mid-air over Gorakhpur in Uttar
Pradesh.

In June 1994, a twin-seat Jaguar was lost when the pilot blatantly
violated rules by reportedly placing a cardboard box in the rear
seat making it impossible to control the aircraft.


And in May this year, a Jaguar crashed on its take-off run after the
pilot aborted his take-off at the last moment.

"Jaguars have been with the Indian Air Force for more than 20 years
now and they have a very good flight safety record. I think one
particular incident should not raise questions on the reliability
and safety of the aircraft," says Squadron Leader RK Dhingra,
spokesperson, Indian Air Force.

The loss of yet another aircraft and indeed the loss of innocent
lives on the ground is another embarrassment for the Indian Air
Force which has a reputation of having some of the highest crash
rates in the world.

For the latest in news visit http://www.ndtv.com
© 2002 NDTV. All rights reserved.

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Re: A Tale of Two Hydraulic Systems

Postby putnanja » 06 Nov 2002 23:51

Over the years, IAF, HAL and other industries related to IA and IN too would have experienced problems and would have come up with indigenous solutions just like the one for Jaguar. If anyone else has articles related to any such efforts, please post them here.

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Re: A Tale of Two Hydraulic Systems

Postby Umrao » 07 Nov 2002 00:03

I dont understand that Jaguar can crash because of a card box placed near the seat.

Every time I see a flight from London/Amsterdam to Bombay the passengers put hand bags which are more dense than lead on over head compartment. :)

Also I just had a horrowing experience in replacing an alternator on MY GMC jimmy (1998 66K miles). If ever anybody is under the illusion that western designs are fantastic, should revist the equipment to repair them in the field.
(its a different matter altogether that most of my batch mates work at GM tech center Warren MI designing cars :D )

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Re: A Tale of Two Hydraulic Systems

Postby Vick » 07 Nov 2002 00:10

Maybe the box in the back seat was oversized and hence limited the full motion of the stick or the box fell from the seat and depressed a rudder pedal or some control apparatus. My assumption is that the stick in the back seat is hard connected to the stick in the front seat and the movement of the stick by either occupant would make the other stick move.

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Re: A Tale of Two Hydraulic Systems

Postby Rudra » 07 Nov 2002 00:23

does the MKI have control stick in back ?

I would assume there is a ON/OFF to make it alive.

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Re: A Tale of Two Hydraulic Systems

Postby Umrao » 07 Nov 2002 00:35

I dont think they would hard link front cockpit controls with rear cockpit controls (you never know western designs but they wouldnt expect any pilot to carry 'Alfanso Mangoes to superiors in a rare(!) cockpit seat'!!.

The real story must have been much more than just a box in a seat.

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Re: A Tale of Two Hydraulic Systems

Postby ArunK » 07 Nov 2002 01:16

Pardon me for being dense, but let me see if I get this straight..

The box in the rear seat of the jaguar prevented the rear stick from moving freely, which of course was linked to the stick of the pilot in the front seat and thus he could not move his stick freely...

Is this right?!!!

I sincerely hope not. But, if it is, then that pilot should have been court martialled and shot for being dumber than a dead door nail..

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Re: A Tale of Two Hydraulic Systems

Postby Umrao » 07 Nov 2002 02:28

Images of Jaguar that was once.

Image

Image

Image

Image

Image

Image

from sify

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Re: A Tale of Two Hydraulic Systems

Postby Surya » 07 Nov 2002 02:44

It is a shame that Vishnu Som of all people had to author that stupid Jag piece.

The last crash was a sad affair and the IAF lost a extremely talented pilot due to a terrible emergency. The pilot did not abort a take off.

What hope do we have for the Hypes etc?

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Re: A Tale of Two Hydraulic Systems

Postby Rudra » 07 Nov 2002 03:17

in the photos one sees a vast crowd gathered doing absolutely nothing , but probably obstructing those doing something.

who are these people ? are they employed gainfully?

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Re: A Tale of Two Hydraulic Systems

Postby rajkumar » 07 Nov 2002 03:24

Originally posted by Rudra Singha:
in the photos one sees a vast crowd gathered doing absolutely nothing , but probably obstructing those doing something.

who are these people ? are they employed gainfully?
It's called MELA. Next time you watch Star or for that matter any Indian TV reporter do a outside piece count the number of people in the background who are just standing & watching.

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Re: A Tale of Two Hydraulic Systems

Postby Umrao » 07 Nov 2002 03:29

Folks I was part of that kind of "Mela" (cutting my 5 th grade classes in Mahbub college) when a vampire crashed in 'Sikh Village' in 1965/66 (IIRC). So its a tradition going strong since then.
Jagan garu>> your records will show IAF Vampire crash in sikh village also the HS-748 crash on my friends (Vakil a parsee gentelman)home (roof top) near secunderabad station.

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Re: A Tale of Two Hydraulic Systems

Postby Umrao » 07 Nov 2002 04:48

"Reports reaching here suggest a preliminary survey of the site and the events leading to the mishap have led officers to conclude that yesterday’s crash was a “freak”. The pilot, Flight Lieutenant Rehani, tried to stabilise the Jaguar immediately after take-off but the controls did not respond.

“It is almost akin to a car driver finding that the steering and gearshaft of the automobile not working even though the engine is running,” one officer said. “It was definitely not pilot error. In fact, he tried to stabilise the plane and bailed out as a last resort.”

Jaguar Crah at Ambala. (from telegraph)
similar to the Hydraulic failure discussed here?

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Re: A Tale of Two Hydraulic Systems

Postby shiv » 07 Nov 2002 06:54

Originally posted by ramana:

The loss of yet another aircraft and indeed the loss of innocent
lives on the ground is another embarrassment for the Indian Air
Force which has a reputation of having some of the highest crash
rates in the world.

For the latest in news visit http://www.ndtv.com
© 2002 NDTV. All rights reserved.
What this lovely bit of news DOES NOT mention is the unrestrained selling of land for development near airbases while local corporators and politicians make big money.

Ficking hell - any idiot knows that if you stand under a ladder which is being used for painting - sooner or later something is going to fall on your (empty) head.

With 1000+ aircraft and a sortie rate higher than most neighbouring conntries I think it is essential that CIVIL authorities cooperate to keep the areas around air bases clear of built up settlements or slums. I hope Vishnu Som is reading this.

The Air Force - like a typical armed force will only murmur this fact - because of their requiremennts for discipline and need to be subservient to Civil authority. I think the press would do well to look into this - rather than make the knee jerk announcement of "embarrassment" of the air force. Shouldn't the idiots who authorize building in the line of runways also be "embarrassed"?


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