Nimrod Information
I've never quite understood the reluctance to use MAYDAY demonstrated by some quarters of the UK Mil. It doesn't cost anything and, provided the aircraft has a genuine emergency, no-one other than crew room (and internet) pundits will criticise. It gets you everything you want from ATC (ie mostly silence) - even if the immediate assistance is simply changing your clearance and arranging priority for landing.
Splitting hairs about what is a PAN and what is MAYDAY is all well and good in the familiar Swanick Mil environment, but many parts of the world have never heard of PAN. Even if they have, the UK Mil has decided to change the ICAO PAN PAN x3 to PAN x3. You can pretty much guarantee that any such call will be followed by "Are you declaring emergency?". At least MAYDAY is universally understood.
In my view, high pressure fuel spraying where it shouldn't is serious danger and not just a condition concerning safety.
Splitting hairs about what is a PAN and what is MAYDAY is all well and good in the familiar Swanick Mil environment, but many parts of the world have never heard of PAN. Even if they have, the UK Mil has decided to change the ICAO PAN PAN x3 to PAN x3. You can pretty much guarantee that any such call will be followed by "Are you declaring emergency?". At least MAYDAY is universally understood.
In my view, high pressure fuel spraying where it shouldn't is serious danger and not just a condition concerning safety.
AC Ovee, you are obviously bold, Sir. Are you yet old?
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Ways of reducing the chances of a fuel tank explosion. I just wonder how many are covered by the use of the bomb bay as a fuel tank.
"To prevent tank explosions, designers have always assumed a flammable vapor exists in the fuel tanks and adopted standards to preclude ignition sources from the fuel tanks. The following are some of the design measures taken to satisfy that philosophy:
a. Surface temperatures inside the tanks, under normal and failure conditions, are kept at least 50°F below the minimum necessary to ignite a fuel-air mixture. Pump motors are kept cool by an integral passage of circulating fuel. The motors have a temperature fuse which cuts the electrical supply before an unsafe surface temperature is reached. In addition, the pumps and other similar equipment inside the tanks, are designed and tested to explosion-proof standards. Where hot air-conditioning pipes external to fuel tanks are routed close to tank walls, such as the engine bleed air pipes in the wing leading edge, it is current practice to position heat-sensitive detector wires on the structure to protect it from overheat in the event of pipe failure or joint leaks.
b. Electrical components and wiring within a fuel tank are designed to handle 1500 volts ac which is well in excess of the power available on the airplane and the operating voltage of the fuel quantity gauging system.
c. Electrical energy applied to any component in the fuel tank is limited to a value that is 10 times lower than the minimum energy necessary to ignite a fuel-air mixture. The minimum ignition energy (MIE) for hydrocarbon vapors is thought to be about 0.25 mj.
d. During the flow of a hydrocarbon type fuel through pipes, valves, filters, etc., an electrostatic charge can be generated in the fuel, which, if relaxed sufficiently fast, could allow the accumulation of hazardous potential levels inside a receiving tank. This is kept within acceptable safe limits by avoiding very high rates of fuel flow in the refueling system and by controlled distribution of the fuel in the tanks, such as bottom loading and
the use of diffusers on pipe outlets. In addition, meticulous attention is paid to electrical bonding of all metallic parts to dissipate the charge. Some countries around the world insist on the use of static dissipater additives in the fuels to increase the fuel electrical conductivity."
"To prevent tank explosions, designers have always assumed a flammable vapor exists in the fuel tanks and adopted standards to preclude ignition sources from the fuel tanks. The following are some of the design measures taken to satisfy that philosophy:
a. Surface temperatures inside the tanks, under normal and failure conditions, are kept at least 50°F below the minimum necessary to ignite a fuel-air mixture. Pump motors are kept cool by an integral passage of circulating fuel. The motors have a temperature fuse which cuts the electrical supply before an unsafe surface temperature is reached. In addition, the pumps and other similar equipment inside the tanks, are designed and tested to explosion-proof standards. Where hot air-conditioning pipes external to fuel tanks are routed close to tank walls, such as the engine bleed air pipes in the wing leading edge, it is current practice to position heat-sensitive detector wires on the structure to protect it from overheat in the event of pipe failure or joint leaks.
b. Electrical components and wiring within a fuel tank are designed to handle 1500 volts ac which is well in excess of the power available on the airplane and the operating voltage of the fuel quantity gauging system.
c. Electrical energy applied to any component in the fuel tank is limited to a value that is 10 times lower than the minimum energy necessary to ignite a fuel-air mixture. The minimum ignition energy (MIE) for hydrocarbon vapors is thought to be about 0.25 mj.
d. During the flow of a hydrocarbon type fuel through pipes, valves, filters, etc., an electrostatic charge can be generated in the fuel, which, if relaxed sufficiently fast, could allow the accumulation of hazardous potential levels inside a receiving tank. This is kept within acceptable safe limits by avoiding very high rates of fuel flow in the refueling system and by controlled distribution of the fuel in the tanks, such as bottom loading and
the use of diffusers on pipe outlets. In addition, meticulous attention is paid to electrical bonding of all metallic parts to dissipate the charge. Some countries around the world insist on the use of static dissipater additives in the fuels to increase the fuel electrical conductivity."
Gentlemen, as a non-flying, non-techie, ground-hugging ex-Supplier and before someone yells ’thread creep’ at me, can I make just one post on this very active thread?
A lot of comments have been made about fuel leaks and likely ignition sources with suggestions that any fuel fire may have been ignited in some way by the aircraft’s on-board systems.
Not so very long ago, on the ‘Discovery’ channel, there was a programme about the loss of large ships. One event featured, was that of a Very Large Crude Carrier (VLCC) which caught fire in heavy seas. The ship (the name of which escapes me) was fully laden at the time and suffered a structural failure when part of the bow became detached from the rest of the hull and caused a rupture in the forward tanks. As a result, the cargo started leaking into the sea. The only driver causing the fuel to escape was gravity - no high-pressure pumps, no electrics – and yet the escaping cargo caught fire. The video showed that the fire occurred after the ship, which had already lost part of the bow, had pitched into a large wave and what was left of the bow had risen clear of the water. The cause of this ignition was believed to be static electricity generated in some way by the ship’s movement through the water and not necessarily from a spark caused by broken plates grinding against each other.
Question – Is it possible that a similar phenomenon,i.e a static charge, which apparently caused the VLCC’s leaking cargo to ignite, could also apply to a leak in an aircraft? As I said, I’m a non-flying, non-techie ex-Supplier so please be gentle – but it’s just a thought.
A lot of comments have been made about fuel leaks and likely ignition sources with suggestions that any fuel fire may have been ignited in some way by the aircraft’s on-board systems.
Not so very long ago, on the ‘Discovery’ channel, there was a programme about the loss of large ships. One event featured, was that of a Very Large Crude Carrier (VLCC) which caught fire in heavy seas. The ship (the name of which escapes me) was fully laden at the time and suffered a structural failure when part of the bow became detached from the rest of the hull and caused a rupture in the forward tanks. As a result, the cargo started leaking into the sea. The only driver causing the fuel to escape was gravity - no high-pressure pumps, no electrics – and yet the escaping cargo caught fire. The video showed that the fire occurred after the ship, which had already lost part of the bow, had pitched into a large wave and what was left of the bow had risen clear of the water. The cause of this ignition was believed to be static electricity generated in some way by the ship’s movement through the water and not necessarily from a spark caused by broken plates grinding against each other.
Question – Is it possible that a similar phenomenon,i.e a static charge, which apparently caused the VLCC’s leaking cargo to ignite, could also apply to a leak in an aircraft? As I said, I’m a non-flying, non-techie ex-Supplier so please be gentle – but it’s just a thought.
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AC Ovee,
1. You, my friend, resemble the End of a Bell.
2. Either that, or you're a great wind-up artist.
3. Or you're a stunningly low-average aircrew mate.
4. Or quite possibly you have no knowledge of anything aviation-related at all.
If it's 3 or 4, then 1 applies.
If it's 2, then you've got us all hook, line and sinker. And therefore 1 still applies.
1. You, my friend, resemble the End of a Bell.
2. Either that, or you're a great wind-up artist.
3. Or you're a stunningly low-average aircrew mate.
4. Or quite possibly you have no knowledge of anything aviation-related at all.
If it's 3 or 4, then 1 applies.
If it's 2, then you've got us all hook, line and sinker. And therefore 1 still applies.
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Whilst waiting for a reply from a certain person, anyone care to answer:
......prior to media publication, what detailed information from the Qinetiq report percolated downwards to Nimrod sqn personnel (aircrew/groundcrew) at Kinloss??
......."how many QinetiQ recommendations have been taken up?"
1st Question. As groundcrew, I, as a Propulsion Tech at ISK have heard nothing. Not now, not in the last 6 years. I'm a mushroom as far as Data like that is concerned, wrong, I know, but true!
2nd Question. Haven't got a clue! But probably none!
......prior to media publication, what detailed information from the Qinetiq report percolated downwards to Nimrod sqn personnel (aircrew/groundcrew) at Kinloss??
......."how many QinetiQ recommendations have been taken up?"
1st Question. As groundcrew, I, as a Propulsion Tech at ISK have heard nothing. Not now, not in the last 6 years. I'm a mushroom as far as Data like that is concerned, wrong, I know, but true!
2nd Question. Haven't got a clue! But probably none!
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I am not an aircrew mate and I have no knowledge of the MR2's fuel system but it strikes me that the chaps who are flying the MR2 need a reasonable degree of assurance that the ac is safe. Clearly this does need to be balanced against the need for the operational task, which I understand is important, but whilst some risk may have to be taken it would obviously be wrong to expect crews to fly in a death trap. I am quite sure that the MR2 is reasonably safe because the MOD says that it is and it would not be in the MOD's interest to be mistaken because of the damage that would be done if it was subsequently found to be wrong.
However, I think that if I was the leader who had decided that the ac was safe to fly, I would be able to think of no better way to persuade my chaps that I had thought the matter through than to fly a couple of missions with them. This is easy for me to say of course because I am neither an aircrew mate nor an AOC nor CAS (and will never be) but nonetheless I have always found that of all leadership styles, by example is the most effective.
However, I think that if I was the leader who had decided that the ac was safe to fly, I would be able to think of no better way to persuade my chaps that I had thought the matter through than to fly a couple of missions with them. This is easy for me to say of course because I am neither an aircrew mate nor an AOC nor CAS (and will never be) but nonetheless I have always found that of all leadership styles, by example is the most effective.
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General All Rounder,
Now there's a great idea, unfortunately I think the only chance of it happening would be:
Dear Jim,
Please could you fix it for me to fly my Nimrod with CDS and CAS ...........
Yours,
Mr Point
Now there's a great idea, unfortunately I think the only chance of it happening would be:
Dear Jim,
Please could you fix it for me to fly my Nimrod with CDS and CAS ...........
Yours,
Mr Point
4mastacker
You ask a very good question. In very simple terms, the answer is electrical bonding.
Too many regard this as a design issue - once designed and implemented, that's it. Forget it. But many factors can adversely affect bonding, and hence the safety of the aircraft. A typical example. Corroded joints in which ground currents are flowing can transmit RF radiation. And when faced with the likes of intergranular corrosion,the reduction in strength due to the corrosion is disproportionate to the reduction in thickness of the metal. It follows that, if you penny pinch and skimp on maintenance, the risk increases. (Just illustrating linkages).
Too much wiggly techy stuff. My brain hurts already. Suffice to say, it is critical to the safety of the aircraft. But to my knowledge there is no suggestion this is relevant to XV230.
You ask a very good question. In very simple terms, the answer is electrical bonding.
Too many regard this as a design issue - once designed and implemented, that's it. Forget it. But many factors can adversely affect bonding, and hence the safety of the aircraft. A typical example. Corroded joints in which ground currents are flowing can transmit RF radiation. And when faced with the likes of intergranular corrosion,the reduction in strength due to the corrosion is disproportionate to the reduction in thickness of the metal. It follows that, if you penny pinch and skimp on maintenance, the risk increases. (Just illustrating linkages).
Too much wiggly techy stuff. My brain hurts already. Suffice to say, it is critical to the safety of the aircraft. But to my knowledge there is no suggestion this is relevant to XV230.
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s15
I'm sure he is reasonably familiar with the front end of the Nimrod, but I wonder if he would be happy to go tanking in one now???
What do you reckon?
Just a thought.
I'm sure he is reasonably familiar with the front end of the Nimrod, but I wonder if he would be happy to go tanking in one now???
What do you reckon?
Just a thought.
. I'll now withdraw from this thread and wait for the BOI report.
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Dodgysootie; Many thanks for your straight forward, and honest answer to those two questions. As someone at the sharp end at Kinloss, if any "QinetiQ" changes had been introduced over the past 18 mths you would have noticed them.
DV
DV
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Fuel Tank Inerting System
I note that the BAe Safety report recommends "mandating of heated fuel tank area inerting during flight, and ....... in-service retrofitment of a fuel tank nitrogen inerting system to prevent the occurrence of an explosive vapour in a partially filled tank.
Since the XV230 accident, Nimrods have been flying with drained No 7 tanks (RTI/MIN/173 carried out before every flight). However, drained does not mean completely free of fuel and vapour.
Any thoughts on this one? To me it does not appear to be a safe operating condition.
No 7 tanks featured in the XV227 incident in 2004.
DV
Since the XV230 accident, Nimrods have been flying with drained No 7 tanks (RTI/MIN/173 carried out before every flight). However, drained does not mean completely free of fuel and vapour.
Any thoughts on this one? To me it does not appear to be a safe operating condition.
No 7 tanks featured in the XV227 incident in 2004.
DV
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QinetiQ report
Given the dearth of answers on the QinetiQ report, and the suggestions that it is irrelevant to the issue under discussion, it might be worth giving a little more detail of the report, laying out some of the issues and asking some more explicit questions.
The Qinetiq team visited Kinloss from 14-15 Feb 2006, at which time XV230 was undergoing special attention from MPI. The QinetiQ team had access to XV230 and the three other aircraft with the EO capability that were then in the UK, indeed these were the aircraft it focussed on. The principal author was Qinetiq’s principal airworthiness engineer.
The report, issued on 17 March, was commissioned by the Nimrod Integrated Project Team. It is true of course that it was asked to look at the problem with leaks in the wings, but a number of problems it uncovered were relevant to all the problems with leaks on the MR2 and indeed appear to my admitted inexpert eye to have much wider implications.
A key concern, and one that clearly had implications beyond the wing leaks, centred around problems caused by the contract for the Nimrod Support Group, which:
* was not required to carry out preventive maintenance
* was working to new instructions it had written up itself because the Air Publications the RAF technicians in the RAMS were using were “of little, if any, value” (but had not told the RAMS that this was the case).
* and was not contracted to relay the full extent of the leak problem to the Integrated Project Team.
With regard to this last point, the QinetiQ report said:
“NSG have compiled important datasets of leak maps from major to major that show recurrent problems. This information is not being disseminated effectively. Neither the Nimrod IPT nor BAE Systems appear to be aware of the detailed information available within these datasets.
“NSG have not been required to supply the IPT and BAE Systems with these fuel leak records.”
"Proper interrogation of the existing data would have highlighted a structural problem that needed to be addressed before it became critical.”
With regard to the out-of-date APs, it recommended that: "A system should be set up in the form of a working group to allow contact between Nimrod repair teams at all locations, eg SNCO level where hands-on experience exists. This would provide a mechanism for exchange of information and good working practices.”
So some questions:
Was the Nimrod repair working group ever set up?
Have the APs in the RAMS been updated to the point where they match up to the procedures in use by the NSG?
How could the IPT make any sensible decision relating to the leak problem, including the decision not to follow the BAE Systems recommendation to fit a fire suppression system in the bomb bay, if it didnt know the full extent of the problem?
Are all contracts across the RAF like this and if so what problems are being stored up with other aircraft?
Finally, not a question, perhaps the most damning quote in the whole report, and one that gets to the nub of a problem that clearly still exists:
"It was also suggested that RAMS cannot detect some of the leaks reported in-theatre when the aircraft return to Kinloss. This is partially explained by fuel load in tanks, climatic conditions, ineffective vacuum in tanks, etc, and Qinetiq were unable to establish a clear impression of how these non-detected leaks are addressed.”
The Qinetiq team visited Kinloss from 14-15 Feb 2006, at which time XV230 was undergoing special attention from MPI. The QinetiQ team had access to XV230 and the three other aircraft with the EO capability that were then in the UK, indeed these were the aircraft it focussed on. The principal author was Qinetiq’s principal airworthiness engineer.
The report, issued on 17 March, was commissioned by the Nimrod Integrated Project Team. It is true of course that it was asked to look at the problem with leaks in the wings, but a number of problems it uncovered were relevant to all the problems with leaks on the MR2 and indeed appear to my admitted inexpert eye to have much wider implications.
A key concern, and one that clearly had implications beyond the wing leaks, centred around problems caused by the contract for the Nimrod Support Group, which:
* was not required to carry out preventive maintenance
* was working to new instructions it had written up itself because the Air Publications the RAF technicians in the RAMS were using were “of little, if any, value” (but had not told the RAMS that this was the case).
* and was not contracted to relay the full extent of the leak problem to the Integrated Project Team.
With regard to this last point, the QinetiQ report said:
“NSG have compiled important datasets of leak maps from major to major that show recurrent problems. This information is not being disseminated effectively. Neither the Nimrod IPT nor BAE Systems appear to be aware of the detailed information available within these datasets.
“NSG have not been required to supply the IPT and BAE Systems with these fuel leak records.”
"Proper interrogation of the existing data would have highlighted a structural problem that needed to be addressed before it became critical.”
With regard to the out-of-date APs, it recommended that: "A system should be set up in the form of a working group to allow contact between Nimrod repair teams at all locations, eg SNCO level where hands-on experience exists. This would provide a mechanism for exchange of information and good working practices.”
So some questions:
Was the Nimrod repair working group ever set up?
Have the APs in the RAMS been updated to the point where they match up to the procedures in use by the NSG?
How could the IPT make any sensible decision relating to the leak problem, including the decision not to follow the BAE Systems recommendation to fit a fire suppression system in the bomb bay, if it didnt know the full extent of the problem?
Are all contracts across the RAF like this and if so what problems are being stored up with other aircraft?
Finally, not a question, perhaps the most damning quote in the whole report, and one that gets to the nub of a problem that clearly still exists:
"It was also suggested that RAMS cannot detect some of the leaks reported in-theatre when the aircraft return to Kinloss. This is partially explained by fuel load in tanks, climatic conditions, ineffective vacuum in tanks, etc, and Qinetiq were unable to establish a clear impression of how these non-detected leaks are addressed.”
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Fuel Tank Inerting System
The full paragraph, from the BAe report, dated August 2004, reads as follows:
"Maintain watching brief of current civil regulatory developments regarding mandating of heated fuel tank area inerting during flight. (In line with FAA fireworthiness developments following TWA Flight 800 in-flight fuel tank explosion accident investigation findings recommending of fitment on new build, and possibly in-service retrofitment of fuel tank nitrogen inerting system to prevent the occurrence of an explosive vapour in a partially filled tank)"
There is also a strange statement in the Summary of the report, which reads as follows:
"In view of the above summary, and on the assumption that the recommendations made within the report are reviewed, it may be concluded that the design and operational assessment of both types [MR MK2 and R MK1], together with in-service record of both types, indicate that both types are acceptably safe to operate within contexts and in a peacetime service from a fire/explosive safety haxard point of view."
To me, the word "reviewed" is an odd choice. I can not see how the same conclusion can apply to "reviewd and rejected" and "reviewed and accepted".
Legal advice sought.
DV
"Maintain watching brief of current civil regulatory developments regarding mandating of heated fuel tank area inerting during flight. (In line with FAA fireworthiness developments following TWA Flight 800 in-flight fuel tank explosion accident investigation findings recommending of fitment on new build, and possibly in-service retrofitment of fuel tank nitrogen inerting system to prevent the occurrence of an explosive vapour in a partially filled tank)"
There is also a strange statement in the Summary of the report, which reads as follows:
"In view of the above summary, and on the assumption that the recommendations made within the report are reviewed, it may be concluded that the design and operational assessment of both types [MR MK2 and R MK1], together with in-service record of both types, indicate that both types are acceptably safe to operate within contexts and in a peacetime service from a fire/explosive safety haxard point of view."
To me, the word "reviewed" is an odd choice. I can not see how the same conclusion can apply to "reviewd and rejected" and "reviewed and accepted".
Legal advice sought.
DV
Last edited by Distant Voice; 14th Nov 2007 at 16:39.
DV, God forbid that all this is going to end up in the maw of the legal profession, the words Hell and freezing-over come to mind. I predict that the majority of the questions that Mike Smith poses above will go unanswered here, by the BoI, and certainly by the MOD. The core problem here, as has been said before is of a self-regulating, self-protecting and self-preserving system. It is broken, dysfunctional and beyond repair IMHO. It must be broken up and replaced with a system subject to external and independent authority. In short a Military Aircraft Airworthiness Authority. This must be done soon, for time is not on our side, and is of the essence. Further avoidable accidents must be avoided urgently.
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Chugalug2: I fully agree, and I am sure that all these issue will be addressed by the coroner.
Many postings on this thread have suggested that people like myself are not "currently" qualified to comment and should wait for the BoI findings. Of course I disagree, and I disagree because the main problems we have uncovered will not be resolve by technical changes to Nimrod, but with changes to the system. And those problems have been uncovered by having the relevant experince and know-how to ask the right questions of the system.
DV
Many postings on this thread have suggested that people like myself are not "currently" qualified to comment and should wait for the BoI findings. Of course I disagree, and I disagree because the main problems we have uncovered will not be resolve by technical changes to Nimrod, but with changes to the system. And those problems have been uncovered by having the relevant experince and know-how to ask the right questions of the system.
DV