Warbird Information Exchange

Rich are you familar with how new drugs are supposed to get FDA approval? It is not just one person or even a few people saying hey, I wore this magnet and my liver cancer was cured, therefore the matter is proven.

To market a new drug, you have to have double blind studies, that is you might treat 800 people who have an illness, half with the new drug, and half with a placebo. Neither the patient nor the doctors know which dose is the real one,until after the study. You would record things like weight gain, nausea, other side effects. The study is supposed to be done by an unbiased source not being paid for their report. I even know someone of Wix who has been in such a study. The idea that the big drug companies have so much money and influence that they can subvert some rules, does not change the concept.

I am not familiar in detail with all the ground running Jack has done. Has he for instance run two similar Merlins side by side for the same time and varied one factor like type of oil used or boost/rpm used? Aviation Consumer has been touting the value to adding Camguard to Aeroshell straight weight A D oil for a few years, BASED ON LAB TESTS.. I haven't heard of any engine guys or even pilots who have tried this in Merlins or even are familiar with it. How do you think Rolls did it? The Rolls book that I mentioned on page 27 has the saying "Don;t fly with your revs too high or your boost too low,or you won't get home." Guys now say,"Fly by the book, but both P-51 and Spitfire manuals in WWII give cruise rpm settings at 1800 or even 1600 rpm. Of course, range was the big factor, but they also would not have used these figures if they thought it would dump their pilots into the Pacific or deep into Germany with a blown engine.

And if I understand what Jack and Mike have said, is first there have been some carb oh that have not been done right. Also and even more so, that 100 LL is different and worse than the WWII 100 octane gas, and thus you need to run your engine different. He may well be right, but I still don't see the facts to back this up. It seems to me, that at low power cruise, 100 ll lead meets the engine needs ok. And if the fuel is really inferior, perhaps in some way other than just octane, then maybe that can even be shown in a lab tests with factual results like we do with oil analysis.

By the way, I was once doing some military flying at PAX River test school and got some 115/145 avgas, which sure tended to foul the plugs at any kind of low power.

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Bill Greenwood
Spitfire N308WK

Have you ever filled up your car on two different occasions with two different brands of gasoline of the same octane rating and had your engine rattle and ping on one of the brands?

Both claimed to be the same octane rating, so how can that be?

Do you think it's possible for avgas to be different and still claim that it is 100LL?

The point is, I'm sure the words "meet or exceed" are in the fuel spec somewhere. Perhaps the older aviation fuel exceeded the spec regularly, and the newer fuel just barely meets the spec. They used to test the fuel with an octane engine by running the engine which had a variable compression ratio. The compression ratio was raised as the engine ran until knock was detected and the octane rating was determined from that test. Now the rating is determined from chemical analysis.

It's quite possible that the older fuel was better then todays fuel.

Just a thought!

Glenn offers the most valid point in this discussion and it stands with no need for further clarification. Formulations are likely different from refinery to refinery and perhaps even the method of determining the octane rating (RON or MON). All could create subtle differences in the actual octane number and flame speed, the latter of which these big pig engines are quite sensitive to because the jugs are so big and they turn so slow.

Some in this discussion are comparing 100 octane avgas from 1940 to today’s 100LL avgas…an apples to oranges comparison at best. Back in the day the easiest, quickest and cheapest way to increase the octane rating of a fuel was to add more lead (TEL). Other adjustments were needed to alleviate some of the negative side effects of the high TEL content but octane number, by in large, was increased simply through the addition of TEL. Today’s 100LL has so little TEL in it that the octane has to be boosted though other chemical contrivances. The least variance to this cocktail will mean minor batch to batch inconsistencies which affect at a minimum octane and flame speed. The upshot is the fewer variables there are to deal with when changing something, the greater the likelihood of getting a more accurate end product consistently. 1940 vs. 2009. How that relates to us as operators means we need to add in a “fudge factor” or pay with burned pistons, cracked heads, broken head studs, bent rods, etc. As was noted by Vlado, using a little more fuel is cheap compared to a $125,000 engine, or worse.

The bottom line is: If we need to turn a Merlin ~100 RPM higher, jet it 5% to 8% richer and run it 10 to 15 degrees cooler to save parts and increase reliability (Which has been proven), then why not? I’d like to think we’re getting smarter and that we are better engineers than our predecessors, especially given the fine engineering tools we now have available. Why not put that to good use?

John

Rich, if 100 ll is the culprit as Jack and Mike say, then one would think that other engines would have trouble with it also. How about the P38s, P-40s, T-28s(man they SOUND like they ate something rotten). I know some T-6 guys and I have not heard them say anything about engine troubles due to fuel. T-6s normally cruise at 1850 rpm, I think, and I have not seen or heard of any guys using climb rpm for cruise.

Glen, I personally have not had one brand of gas knock in my car, but perhaps my 76 BMW with the inop odometer, or my 21 year old Mercedes with 161,000 miles on it is not the best test bed and I drive pretty mild, to save money cause I 'm too tight to buy a new car.

John, maybe you have a point. Maybe there is something in 100 ll so that it meets the octane rating, but still does not behave the same as the old 100. But still this is a maybe, I just don't see any hard evidence that we know for sure that the fuel is inferior. And I don't think anyone ever bent a rod just from cruising a Merlin at 34in and 2000 or so. I don't really buy that the avgas varies so much from batch to batch or that some is below spec. If that was true, then likely oil would have the same variety and that doesn't seem to be anyone's concern. And congrats to you on the P-51C.

I have flown behind one of Jack's engines and it ran well and the owner liked it. We will see over time. His pistons look great and seem to be proving themselves,and it is great that he is making so much new.

I expect we will send my engine our for overhaul in the next year, it was running just fine, but has almost 1000 hours, much of that at 1800 rpm cruise. With the stoppage, we want to have it checked and will probably go the whole OH. The thought of it makes my checkbook hurt! So we will see what it looks like inside. By the way it is pretty stock, except for Merlin fingers, has Rolls factory pistons. One other operating factor, while Spitfires may get hot idling on the ground, it runs very cool in the air, even with the doors closed it is about 85* rad temp.

I wonder about other warbird guys, overseas, or overcheese (that is north of Wisconsin). do they have the same thoughts about 100ll? I know some of the Brits are still using all mineral oil, not even AD, and some use 100 not 120 in Merlins. Of course they don't fly very far. I have personally flown my plane to Canada and well as all 4 corners of the US and points in between. Hope to do it again. And I wish I could fix them like you guys can.

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Bill Greenwood
Spitfire N308WK

I have a PDF file on the use of 100LL in warbirds. How can I get it posted here?

Basically it states there is a minor difference in the use of 100/130 (green) vs 100LL (blue). 100/130 has up to 5ml of TEL per gallon, and 100LL has up to 4ml per gallon. The difference is 100LL has more aromatics (toluene or xylene) added to make up the difference. Automotive octane boosters use toluene or xylene.

You can run your engines at low RPM/high MAP as long as you stay within the flight manual guidelines. On FIFI, we could run as low as 1400 RPM with 32" MAP and still stay within the guidelines but we never did as the airplane would fly like a dog.

For those of us without too much B-29 flight time, what is PDF?

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Bill Greenwood
Spitfire N308WK

(Portable Document Format) It's a file format from Adobe that all computers can read using a free program from Adobe called Adobe Reader. Works wonders if you have a Mac and need to communicate with someone using a PC.
It's computer stuff Bill, not aviation stuff )

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Dudley Henriques
International Fighter Pilots Fellowship

Thanks Dudley

Bill,

Thanks for kudos’ on the Mustang. Not to be picky but it’s a “C” model, not a “B”. Jack Roush has the only flying “B” model.

I’m leaving oil out of the discussion for now and keeping the scope narrowed to avgas and engine system operating variables for now.

You’re looking for scientific documentation on one hand and on the other are making statements like:

“…one would think that other engines would have trouble with it also. How about the P38s, P-40s, T-28s. I know some T-6 guys and I have not heard them say anything about engine troubles due to fuel. T-6s normally cruise at 1850 rpm, I think, and I have not seen or heard of any guys using climb rpm for cruise.”

To be fair, balanced, honest and objective, you need to compare identical engines. How can you compare an R-1340 putting out 650 hp to a V-1650 putting out ~1500 hp? Apples to apples now Billy! Although some of the engines you mentioned may appear similar, how physics is at work inside each is often quite different from another. Those differences along with how each has been set up (Tuned) equate to how they will react to the of quality fuel. That holds true in identical engines that have been set up differently as well.

You’re fixating on one set of operating parameters Bill and throwing out your own empirical judgments to support the island you stand on as well. Issues don’t normally arise at cruise settings when the engine is healthy and all the variables (EI: ignition timing, A/F mixture, oil and coolant temperature, etc.) are all set correctly and you have fuel at its “As advertised” quality. Move any of those things around the wrong way and you get closer to detonation (What we’re trying like he11 to avoid) if not all the way there. You may not bend a rod at a low cruise power setting but you’re certainly priming yourself for burning a piston, cracking heads and so on. Take the same set of circumstances and push the power settings up to max continuous power or take off 55” to 61” and 3000 RPM. Can’t bend a rod? I’ve seen one…held it in my two own hands and was simply dumfounded that it could actually happen, but there it was. I’ve stared at cracked heads (So have you), I’ve replaced broken head studs and cracked head nuts…most all because of detonation or excess heat build up.

You want hard evidence of anomalies in fuel runs? You need to contact as many refineries that produce avgas as you possibly can and get all their run data on each batch and compare them all. Even if they would supply you with the data (Which they won’t), it wouldn’t do you much good unless you’re a Petrochemical Engineer familiar with the data placed in front of you. That said, unless somebody out there has limitless money to spend accruing and crunching such data, we have to go by seat of the pants based on the best engineering data and failure analysis we have at hand (Which is not an insignificant or trivial amount).

Your Spit in flight operates where Jack Roush recommends the Merlin should be operated (for good reason). The Mustang book says 100 to 105* C. 212 to 221*F??? That’s insane! I can’t think of another liquid cooled autocycle engine that operates at those temps. Most are in the 185 to 195*F range. Lower coolant temps buy you at the very least more cushion against detonation and longer casting life.

Maybe gas is radically different in Colorado than it is in Minnesota and [presumably] Indiantown, Florida or perhaps the way each of us is in tuned to our vehicles, but I have to agree with Glenn. On more than one occasion I’ve pumped a tank full of gas that was notably inferior to the last. I have no reason to believe avgas would be any different.

John

Dudley, Computers?, gosh you guys are really trying to confuse me. And I thought you were an old pilot like myself, well let's call it extended middle age. You know one of the great things about a Merlin, it doesn't have any computers in it.
I am not too good at computers, I do know some general things about piston engines, after all I really was an honor graduate of the A F mechanics tech school at Chanute AFB, not the place you'd want to spend a winter. The explanation is that those who passed the course with an A got to go home early,back to Texas. That was a motivator. And no, they did not let me work on the P-51 H there. They missed at chance to make a convert.

John, I think you guys may have something with the idea that the volative additives in 100 ll to replace T E lead may react different in an engine. But I do think that if 100 ll is such a bad fuel,that it would show problems in something in other planes,besides Mustangs. No one is advocating low rpm or lean mixture in high power like takeoff or climb. But I certainly think you can do an economy cruise at low rpm and relatively low boost, say my Spit at O (30 in) and 1800 rpm without engine damage. Maybe I have just been lucky. I guess we may get an idea when my Rolls 76 goes to OH, I'll try to get some photos then.

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Bill Greenwood
Spitfire N308WK

Bill,
Nobody is saying 100LL so bad and it's going to turn your Merlin into a pumpkin. Obviously that's not the case. The jist of the discussion is, to be safe (With regards to engine life and well being) some safeguards should be taken to ensure there is a little larger delineation between clean running and detonation, that's all. If you're comfortable continuing on the path you've been on for the last 20 years, by all means, you should stay the course since you're the stick actuator in that airplane.

The next hurdle is what to do when blue juice goes extinct and we start burning swamp grass without lead for valve lube?

John

Believe it or not I never had a computer in the house until I stopped flying and started getting involved in flight safety. I even had to learn to type. I use the bible method. "Seek and thou shalt find" [ the keys that is]
It's hard to get anything done today without at least a bit of computer savvy. I'm actually getting quite good at it for an old grumpy bald guy Then I have the kids and the grand kids to help me if the cat eats my megabytes

I've been following this thread with some interest and haven't chimed in as our Mustang operation was 30 years ago. I flew ours strictly by the book didn't play around much with the settings. I will say this however. I wish back in those days we had the goodies on our engine that came on line a bit later. Fingers sure improved things up top, and people like Roush have done wonders with their in house engineering Merlin research.
I'll tell you the honest truth Bill. If I was operating a Mustang today with the available fuel, I'd be very prone to follow the advice of people like Rich and Glenn, not to mention Jack Roush.

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Dudley Henriques
International Fighter Pilots Fellowship

I guess I am a bit of a natural skeptic, and I like to understand the why of things, not just take opinion as fact.
Sometimes experts, no matter how experienced can still be wrong. Maybe they have a domain to protect, or it is just human nature to want to be right.

For example: for years there were problems with structural failures of v tail Bonanzas. I recall something like 150 people being killed over a few decades. No big problem, the experts, of which there were many, could blame it on bad pilots and thus easily explain it away, so that nothing has to be done to the airplane, and dead people tell no tales. Some of the breakups did happen in IMC and to low time pilots. Barry Schiff even wrote in Flying or AOPA about how great the plane was and therefore it was the pilots fault. I even talked to him in person and got the same mantra. But anyone that took a fair and unbiased look with common sense at the problem would be struck that very few other planes were breaking up. Why were all the bad pilots or most of them in v tails? How about straight tail Bonanzas, rare to break up. And most of all Mooneys, almost unheard of to break up in flight, even if the average Mooney pilot like myself had less time, less experience, less imc time, than the average Bonanza pilot. And some of the breakups happened in clear air, not imc. Finally, a few pilots even survived a close call and landed with some tail damage, but still intact.

After literally decades of inactivity, the FAA finally acted. They found problems with the Vtail and it was not just the pilots. If the rudervator balance was off, like after painting, or if the trim control cables were lose you could get destructive flutter in otherwise normal conditions. After the FAA study, the regs were changed, so that repair shops were cautioned to really make sure about these two items were correct and they also called for a reinforcing bracket to strengthen the tail. And guess what, despite what Schiff and all the experts, after that v tail breakups pretty much went to zero, I think I may have read of one in recant years. So conventional expert opinion may be correct most of the time, not all.

Another example is that ulcers were kn0own for years to be caused by stress. Now doctors know it actually is caused by a bacteria, but when the Australian researcher first reported his findings he met hostility and ridicule from many other doctors. It is not easy for the human mind to look past what we believe.

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Bill Greenwood
Spitfire N308WK

A couple of comments from a certified amateur:

1. A T-6 can use 80 octane fuel or better, even autogas with an STC, so 100/130 or 100LL is overkill (unless racing I guess).

2. Standards have been tightened and variability reduced in all areas of manufacturing. I would expect that fuels would be more consistent from batch to batch and manufacturer to manufacturer now than they ever were in the 1940s, 1950s, 1960s, 1970s or 1980s. That's not to say that there aren't occasional snafus, but I believe this to be generally true. The industry has also consolodated greatly, so the number of vendors has been dramatically reduced.

Bill, I think you might be making some glittering generalization here that isn't even close to the way pilots involved in high performance aviation view these issues. First of all, the first thing one learns, or at least I learned anyway, when entering into the world of high performance airplanes, is that these metaphors that are unrelated to aviation such as drug approval etc, don't necessarily equate when an attempt is made to equate them in a flying scenario.
It's fine to be skeptical, but only to the point where you gather all pertinent information from all available sources then make a decision based on your own experience as to what is fact and what isn't fact.
A pilot who takes information and accepts it as is without thoroughly vetting it out won't live long flying high performance airplanes. I think both of us can agree on this.
When a pilot like me says that I would put a lot of value on data supplied by someone like Glenn, Rich, or even Jack Roush, I'm saying that I have great respect for their proven expertise. If that pertained to MY airplane and how I would be operating it, I can assure you all 3 of us would be having some serious discussion before I made a final decision on procedure.
It's a bit of a stretch I think, if you believe that any pilot out here flying behind a Merlin is the type of individual who accepts ANY expert opinion without asking a WHOLE lot of questions
Personally, when it came to this type of thing, I always gathered any and all information available, then proceeded as I saw fit with a step by step process that either proved out the expert opinion or disproved it.
You live longer this way........trust me ))))))))
Dudley

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Dudley Henriques
International Fighter Pilots Fellowship