Winco,
On what exactly do you base that comment? Do you not think that with the several recent AAR fuel leak problems with the MR2 and the loss of 230, AAR in a Nimrod is just slightly more dangerous than say an E-3 or a VC-10 or a fast jet maybe?
Well, I have conducted AAR on different aircraft throughout the years; tanking and receiving. While different aircraft types route the pipes differently, the same principles and materials are generally used. But, I have heard that there are some types that have double-skinned pipework. The MR2 has the same where the pipe passes through the crew compartment. I agree that the Nimrod is far from the the latest design in AAR, but that doesn't make it unsafe just because of that. What makes it safe, if safe means that it will not suffer a fire, is answered below.
Can you also tell us what exactly has been done to eliminate the possible causes of fire in the bomb bay?
Prior to the accident, Nimrod AAR might have carried a fire risk that is not there now: fuel flowing at high pressure in pipes in the vicinity of other pipes carrying hot air. I cannot say (because I haven't been told) that on 2 Sep 06 fuel leaked from its pipe and then came into contact with a nearby charged up air pipe, but it is a recognised possibility. Due to that possibility, the use of all hot air pipes in the fuselage is now prohibited during flight. The bomb bay and surrounding areas is now cold and dormant. Only fuel, hydraulic fluid and warm air to/from the cabin, pass through there. Yes, there is electricity, but unless you want to believe that there is a risk of a simultaneous major electrical fault, not known to the crew (otherwise they wouldn't do/continue the AAR), any fuel leak in that bay will not ignite. We dump fuel using the same pipes, except for one pipe dedicated to AAR due to an NRV. The pipes, throughout the jet, are liable to leak during dumping and they occasionally do so. Should we now cease dumping for fear of a leak from the same pipes that are used for AAR, despite the fact that dump pipe leaks have occurred regularly, without any fires, throughout the life of the Nimrod?
The system operating limitations we have now imposed on the Nimrod have removed all possible causes of a fuel fire while it is airborne with fully serviceable electrics. Someone here asked about motors and commutators, etc, in the bay. There are one or two in there, but they are sealed units, checked regularly and are not unreliable.
FYI I am a captain of a large 4 engine aircraft, and if I had a major fuel leak similar to that of 235, then I wouldn’t hesitate in putting out a MAYDAY, because you ARE in serious and imminent danger, and you DO need immediate assistance (CAP413)
Firstly, it was reported by the media as a "major" fuel leak. I didn't edit the news, so I might be wrong, but if the crew use "Mayday" it would be a reasonable deduction by the media to report it as a major leak; even you believe it was a major leak. It wasn't. It was a spray that ceased shortly after the disconnect and was later described by the crew themselves as probably a few gallons.
We can argue about the use of Mayday until the cows come home, but if you are on fire: mayday, if you are without engines: mayday; if you are out of control: mayday, if you are about to crash: mayday. If you have 300 pax you might want to get the ATC on your side for lesser problems and a mayday achieves that.
I will refrain from commenting about what you wrote about Fuel and Ignition, because you are fundamentally wrong.
But you didn't refrain:
High pressure fuel vapour is NOT difficult to ignite at all (why do you think we have such severe restrictions around aircraft during fuelling?)
I agree that its not difficult with a naked flame, which is at the core of the severe restrictions. However, remove the naked flame and all heat sources and it becomes very difficult. Aircraft do not power down to take on fuel. 200V is humming everywhere and despite the "no switching" rule, many refuel systems include float switches on the walls of the tanks and electrical contents systems (including your big widebody jet with all the crew and cleaners in there on a refuel stop, yes?). The systems are allowed to switch on/off while refuelling because they are serviceable. We do not cater for double faults: ie a fuel leak/vapour with a simultaneous unrelated electrical fault nearby. Even when we want to deliberately light the fuel on an aircraft we have to employ HE igniters then spread the naked flame around the liners.
PPrune isn’t responsible for that, and to suggest that the crews wouldn’t have known about it if they hadn’t read it on PPrune is stupid.
I wrote that the lesser experienced guys could be influenced by what they read here.
we should not be doing this, I read it on pprune, etc"
You and others have been writing words to the effect that AAR is not safe. Using the name Winco isn't accidental. I doubt that you left us as an SAC. You write in an authoritative manner and you clearly intend to influence people (as I do). My point is that, while pprune, "etc" might not spawn distractions, your influence and contributions run the risk of adding to them.
And to say that PPrune doesn’t have a voice – how wrong you are!
In the context of my statement, pprune does not have a voice that would influence CAS and others to stop AAR. Anonymity carries no authority. Yes, pprune has a function. TD has asked questions and we have answered some of them with fact, not opinion, unless we said so. Discussions about policy before 2 Sep 07 is clearly useful to those who wish to seek compensation.
Clearly, Winco, we do not share the same opinion on this and I doubt very much that either of us will give much ground to the other. I accept that my comments about the Mayday were cutting, but I simply wished to make it known that it was not a major fuel leak.