Turbulence

My Feedback: (76)

according to our AMA regulations, AMA rule # 5 for twin turbine jets reads:

"enclosed multiple engines must be segregated in separate pods or partitions where exhaust gasses cannot mix causing cross-ignition"

O.K. as most of us think of this rule is maybe a little outdated, let's hear the pro's and con's. Personally I think this rule only applies to the older Sophia engines that used to run on propane. The AMA is at a point where it's comming up on reviewal of the rules. suggestions can be made to Ilona at AMA so before I make the offical suggestion, the questions are as follows:

1. "With modern Turbine Engines that run Kero (but still use propane to start)" Is there a cross ignition problem possible?"

2. "Does it need a wording change to allow open installs?"

3. "I know it should at least be modified for Kero Start engines, what do you think?"

Turbulence

uncljoe

My Feedback: (8)

Ralph
Good Luck on getting the AMA to remove it.or even clarify what a partition is.
Semper Fi
Joe

George

My Feedback: (57)

Ralph, you're on the right track [sm=thumbup.gif]. I agree with you, the "twin" rules should be revisited, but when I brought this up to the JPO, they did not seem interested; they were only interested in raising the single turbine thrust limit to 50# (which by the way is the current max thrust allowed for a twin ). REDICULOUS!!

I agree, the open installs should be allowed with the current engines, but not limited to only kero-start. How do the exhaust gases mix when they are being blown into the pipe via a bellmouth? I was not around during the Sophia era, so I'm not sure I'm clear on the mixing of exhaust, but like you said it was probably a propane issue at the time.

George

Adil Nasim

My Feedback: (61)

I could see both sides of the fence on this one.

Lets say you have an open install even though you have the twin pipes with bell mouths. You start both engines but only one starts with the other one pumping powermax/propane gas trying to light up. What do you think happens? Maybe just a big bang and then nothing or nothing or worse?

What do you guys think?

Adil

Shaun Evans

Has anyone ever even seen a cross-ignition in a twin??

f106jax

My Feedback: (16)

In a "letter of the law" interpretation of rule #5, having the exhaust exit through individual tailpipes complies with the rules. The wording "enclosed multiple engines" refers to engines enclosed in the fuselage as opposed to externally mounted. The goal of this rule being to avoid exhaust gas mixing. This can be accomplished by using "separate pods" or bypasses, or partitions. Individual tailpipes for each engine, as opposed to a bifurcated pipe, does comply with this rule. A partition does not have to be a bulkhead or other structure. In our case of keeping exhaust gases segregated, individual tailpipes certainly are partitions that achieve the stated goal. Since the rule says "separate pods OR partitions", there is no requirement for a bypass if you are using the partition, or tailpipes.

I've worked in the government with law and regulation interpretation long enough to believe that individual tailpipes meets the definition of partition. Since it meets the stated goal, I think that the AMA would have a hard time arguing the point. Of course, working for the government has put me on the section 8 fast track!

Mike

AndyAndrews

Maybe I'm wrong but if you are using the correct precations it shouldn't matter. Shut down valve and cut the engines with the air still on them. Or shut off the one running and hit it with CO2. I see no difference with this issue than handling a wet start.

Andy

seanreit

My Feedback: (60)

Mike, being a government contractor for over 15 years leads me to agree with you. Whenever a rule is written, if there is room for other interpretations of the rule, the writer of the rule has a responsibility to be more specific. Even if their interpretation is reasonable, the modeler's interpretation will prevail every single time, because the writer "could have been more specific".

That's why when the other thread was going on, I said, don't even ask. Cause it does not matter at all.

Turbulence

My Feedback: (76)

Mike,

Great minds think alike. When I started writting this thread I was thinking that just sticking the tailcone of the turbine right in line with the pipe would cure this problem. Sure you loose a little static thrust. Of course adding a bell mouth to the tailpipe will give allow to you leave a gap and be in compliance.

I decided I am willing to take the time to make the suggestion to AMA. I personally do not see the SMALL amount of propane used in starting a turbine causing a "Cross ignition" or anything of the sort. If you have a failed start all modern turbines SHUT OFF the gas via the soleniods right? So my questions are basically to get a greater range of thought on the pros and cons. If it's not safe then why waste time in trying to change things. If we all more or less feel the same, then the worst AMA can say to my suggestion is that it got filed in the "round bin" and I would have lost Nothing. I see lot fo lookie loos and only a couple of suggestions / replies???? Thanks to those of you have made your opinions known

Turbulence

Ray Davis

My Feedback: (1)

Mike, I'm guessing, but in the day of the Sophia, etc., I think the original intent was to prevent, by complete engine compartment separation, any propane supplying one engine from reaching the other. This during any condition...not running, start sequence, running, etc. And so, would seem to mean entirely separate intakes, engine compartments and exhaust systems. Never been fully explained/implemented/enforced, that I'm aware.

However, today that is 99% moot, as the little propane used in starting is unlikley to migrate and is controlled.....further, contrary to someone's above, my understanding is that the JPO is going to address this, looking to the AMA for at leash a fresh interpretation, or elimination, altogether.

Ray
Dist I JPO rep

George

My Feedback: (57)

Ray, I wasn't saying that the JPO wasn't addressing THIS particular issue of clarifying rule #5; only that they were not interested in addressing what I thought was a more important safety issue of twin thrust, but lobbying for increased thrust on a single.

However, this thread is concerning rule #5, and I do not want to highjack Ralph's thread; so let's stay on topic.

And YES, I'm a JPO member!

George
Dist IV JPO ADR

rolsen12

Has anyone tried to do this, or is this just a rule that someone thinks will happen?
Making rules should be backed up with proof.
That costs money, but it proves a valid point.
Other wise it is just a wild guess.

Turbulence

My Feedback: (76)

Please forgive my IGNORANCE,but are you SURE you are in the right Forum. That is an actual rule that we beleive needs updating.


Ralph