Revisiting Merlin's Magic Accident

[Hawkeye]

I have been doing some thinking about the Oxygen accident at Reno. Can someone tell me if there is a over-pressure switch in the low pressure oxygen system in the P-51. if there was a pressure relief switch in the system, there is no way the system could be over-serviced and blow up due to too much pressure. it is an easy modification to do and would protect the A/C from suffering the resulting damage. I hope if Merlin's Magic is going to stick with the low pressure oxygen system, they consider doing this.

[number17fan]

Re: Revisiting Merlin's Magic Accident

A small placard stating "max PSI 450" or whatever would be much lighter.
Saving a pound one gram at a time.

[Hawkeye]

Re: Revisiting Merlin's Magic Accident

But the placard is NOT foolproof. The pressure relief switch is!!

[AAFO_WSagar]

Re: Revisiting Merlin's Magic Accident

A small placard stating "max PSI 450" or whatever would be much lighter.
Saving a pound one gram at a time.

I don't know about the feasibility of using a pressure relief valve when pulling G's would be an option but *if* it were something that could be implemented, I can think of two accidents that could have been avoided if the tank had been fitted with an overfill valve set to say, 200lbs beyond recommended...

Certainly more fail safe than a placard and would probably weigh less than a bottle of water.. maybe two but hardly significant...

Again, I do NOT know if you can use the spring loaded popoff valves when pulling G's.. but they are pretty simple, light and fairly fail safe...

Certianly food for thought at the very least..

[Hawkeye]

Re: Revisiting Merlin's Magic Accident

The system on Race 22 was rated for 500 psi and failed at 600 psi. On a low pressure ,high volume system you would have to set the pop off valve at 500 psi to protect the system. You mount the pop off valve parallel with the thrust line to minimize the g-load affecting the valve. The effects of positive and negative G's should be minimised. WHEN you need it is when you are filling the system.

[Apteryx]

Re: Revisiting Merlin's Magic Accident

I think any one that flies, knows of at least one fueling error. Bit Bob Hoover in the butt, real good, as did over pressurizing. Placards don't work.

[On Site Grafix]

Re: Revisiting Merlin's Magic Accident

I'm really ignorant on this subject but here's my thought.

If the O2 cylinders were mounted with quick release mechanisms wouldn't it just be easier to have filled tanks standing by and exchange them as needed. Almost no risk to the aircraft since bottles would be filled and sitting for some time before installation. Is this a possibility?

Couldn't exchanging bottles be a trained crew members responsibility? I realize the engineering on the fuselage for a quick-change system may not be a reality currently but if it was my aircraft and it didn't get destroyed by an explosion, I think I'd be willing to do the math and install a quick release system.

I'm probably all wet but it seems logical to me!

[DPK2]

Re: Revisiting Merlin's Magic Accident

What about something as simple as a rupture disk? Very simple, fool proof, and very little extra weight involved.

David

[On Site Grafix]

Re: Revisiting Merlin's Magic Accident

They work on blown and turbocharged motors in drag racing, seems like they might be a workable solution here. They certainly wouldn't be affected by 'g' forces and the effects of temperature are pretty much inconsequential.

Might be the cheapest and most practical solution if you can't remove the potential problem from the fuselage with a quick release bottle exchange system. Hasn't somebody already implemented this?

[BellCobraIV]

Re: Revisiting Merlin's Magic Accident

Couldn't exchanging bottles be a trained crew members responsibility?

Lets see if some people are not overanalyzing a situation, In the entire history of the Reno air races we have had one tragic accident regarding this process. SO, if we take the above quote and change a few words we get;

Shouldn't filling bottles be a trained crew members responsibility?

The answer is yes, pressure bottles should be handled and serviced by someone that knows the risks involved. Most FBO's can service oxygen for aircraft that require it. Rare Bear has a standard Cessna adapter for doing so complete with a remote gauge next to it. So the equipment is available and most teams have it already. It just takes a responsible amount of due diligence in a maintenance procedure to accomplish this task. I don't mean in anyway to reflect criticism on the Merlin's Magic crew. I am speaking in general terms as to what it takes to do the job. A new rule or oxygen servicing only area is not required. Moving oxygen service to a remote location will only cause more of a traffic jam to servicing the aircraft. Where would you move the oxygen service to? not next to the fuel trucks, not in front of the Formula/Bipe areas, neither of those would be safe and fair to other competitors. So just train and pay attention to the system in place. When somebody dies in a car accident because another ran a red light they don't outlaw intersections. Just my opinion but watch your game.

[On Site Grafix]

Re: Revisiting Merlin's Magic Accident

Lets see if some people are not overanalyzing a situation, In the entire history of the Reno air races we have had one tragic accident regarding this process.

Of course my comments were made not being familiar with the frequency of this type of event. If it is an infrequent occurance then air racing probably doesn't need further regulation to curtail it, just more diligence and education.

Over-regulation can create it's own set of problems perhaps more dangerous than the problem being regulated. I'm not for additional procedures unless the problems they seek to regulate warrant it.

I was no more than 30ft from Merlin when the bottle blew and all I remember was how sad it was after all the effort that had been put into getting the aircraft to Reno and the subsequent engine change. Thank God no one was seriously injured I guess I'm kind of a sentimental guy in the end!

[fenceliner01]

Re: Revisiting Merlin's Magic Accident

[. SO, if we take the above quote and change a few words we get;

Shouldn't filling bottles be a trained crew members responsibility?]

Ahhh, a simple, elegant solution to the problem. Spot on, John.

[Air Race Addict]

Re: Revisiting Merlin's Magic Accident

When somebody dies in a car accident because another ran a red light they don't outlaw intersections. Just my opinion but watch your game.

They would if they could........ Probably has been tried and has been successful somewhere. Good grief.
Good post John, as usual. So, as someone with a lot of experience with these birds, what's wrong with installing a blowout disk like we use on commercial aircraft, (every one I know of at least). We generallly have two, one for a thermal expansion and one for an overpressure while servicing. Is it an issue of having to retrofit the regulator on the bottles? I am sure it could be a little spendy. And like you say, there is no substitute for training. I think the MM guys are trained, it was an accident, eh? Unfortunate, and really, REALLY, lucky no one was hurt worse than they were.

[jarrodeu]

Re: Revisiting Merlin's Magic Accident

Sure, lets put in a roundabout! Whose with me?

Jarrod

[BellCobraIV]

Re: Revisiting Merlin's Magic Accident

I don't know about you guys but every time I look at a ladder and see all the "warnings". It makes me think about being a kid and how I survived the "disasters" that were put in front of my very existence on a daily basis. One of the things that amazed me when I first started Street racing years ago, (Yes I know that was a violation of Ca VEH. 23109, A, B, C, & D, depending on your concurrent participation) was the lack of other guys studying what they were doing. Now granted I had Dave Zeuschel's and Randy Scoville's ears to confer with. But their best and most consistent advice was read. So for things you are doing in life critical situations, read, study, learn. It's simple, thoroughly know what you are doing it's the best idea. If you don't know then ask.