Debunked: High Bypass Turbofans do not make Contrails [actually they make more]

[Mick West]

In a rather odd reversal of known science, the latest chemtrail theory is that modern high-bypass engines do not create contrails. A comprehensive explanation of why this is incorrect can be found in the following video:

As noted towards the end of the video, the idea can be debunked simply by a review of the scientific literature. The likelyhood that a particular engine will create a contrail is governed by the "contrail factor", and this is higher for high bypass engines - I encourage you to research this for yourself, and I give some links below.

The classic demonstration of high bypass engines producing more contrails is the study:
Ulrich Schumann and Reinhold Busen, 2000, Experimental Test of the Influence of Propulsion Efficiency on Contrail Formation
http://elib.dlr.de/9247/1/aerscitech-2000.pdf

For a direct test, a formation flight of two different large jet air- craft was arranged, wing by wing, during an ascent and a descent of the aircraft. Contrail formation and ambient conditions were observed simultaneously from a research aircraft. The two contrail
forming aircraft were 1) a Boeing B707-307C built in 1968 and equipped with four jet engines of type PW JT3D-3B with bypass ratio of 1.4 and 2) an Airbus A340-300 built in 1998 with four jet engines of type CFM56-5C4 with bypass ratio of 6.8.
...
A contrail was observed to form during ascent first behind the A340 at 7:28:40, at flight level 33,300ft. The B707 continued to ascend nearby without a contrail (Fig. 2). About 50 s later, at altitude of about 33,700 ft, a contrail formed also behind the B707 at 7:29:30. The contrails were observed to be forming very suddenly and persisted thereafter. During descent from flight level 35,000ft, the contrails disappeared first behind the B707 and disappeared shortly thereafter behind the A340.
...
As documented in several photographs, an altitude range exists in which the A340 causes contrails while the B707 causes none. Figure 2 shows this fact during ascent and Fig. 3 during descent. The photographs show the contrails best during descent due to the more favorable sun and Falcon positions relative to the two other aircraft. We clearly see the four contrails forming from the four engines of the A340 while the B707 is seen flying without contrails.

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As you can see, the newer high-bypass A340 produces contrails more frequently than the older, low-bypass B707

Schrader, Mark L., 1997: Calculations of Aircraft Contrail Formation Critical Temperatures. J. Appl. Meteor., 36, 1725–1729.
http://journals.ametsoc.org/doi/full/10.1175/1520-0450(1997)036<1725:COACFC>2.0.CO;2

Appleman diagrams for specific engine types (Saatzer 1995) are shown in Figs. 4a–c. Tables are provided in the appendix. Contrail factors for bypass engines are higher than those for nonbypass engines because the core exit temperature is reduced by extracting some energy to turn the fan.

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Fig 4 shows contrails forming at a wider range of temperatures than non or low-bypass engines. You don't have to follow exactly what the graphs mean, just note that for the high-bypass engine, the curves intersect the bottom axis at a higher temperature than the low-bypass or non-bypass engines.


Walters, Michael K., Jeffrey D. Shull, Robert P. Asbury, 2000: A Comparison of Exhaust Condensation Trail Forecast Algorithms at Low Relative Humidity. J. Appl. Meteor., 39, 80–91.
http://journals.ametsoc.org/doi/full/10.1175/1520-0450(2000)039<0080:ACOECT>2.0.CO;2

Although the contrail factor for an individual aircraft varies as flight parameters change, Schrader (1997) pointed out that one can use representative values for the contrail factor that account for the generic propulsion efficiencies of typical engine types when preparing contrail forecasts used for different types of aircraft at the same time. This procedure is currently followed by the AFWA, which produces separate contrail forecasts for high-bypass, nonbypass, and low-bypass engine types. Because propulsion efficiency is highest for high-bypass engines and lowest for nonbypass engines, high-bypass engines have the highest contrail factors, and nonbypass engines have the lowest contrail factors (Schrader 1997).

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Influence of propulsion efficiency on contrail formation Ulrich Schumann
http://www.sciencedirect.com/science/article/pii/S1270963800010622

Aircraft cause contrails when flying in an atmosphere colder than a threshold temperature which depends on the overall efficiency η of propulsion of the aircraft/engine combination. Higher η causes contrails at higher ambient temperatures and over a larger range of flight altitudes. The ratio of temperature increase relative to moisture increase in engine plumes is lower for engines with higher η . Thermodynamic arguments are given for this fact and measurements and observations are reported which support the validity of the given criterion. The measurements include contrail observations for identified aircraft flying at ambient temperature and humidity conditions measured with high precision in-situ instruments, measurements of the temperature and humidity increases in an aircraft exhaust plume, and an observation of contrail formation behind two different four-engine jet aircraft with different engines flying wing by wing. The observations show that an altitude range exists in which the aircraft with high efficiency causes contrails while the other aircraft with lower efficiency causes none. Aircraft with more efficient propulsion cause contrails more frequently. The climatic impact depends on the relative importance of increased contrail frequency and reduced carbon dioxide emissions for increased efficiency, and on other parameters, and has not yet been quantified.

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Lynch, David K., et al, 2002: Cirrus, Oxford University Press
http://books.google.com/books?id=58v1fg4xeo8C&lpg=PA233&ots=_-uNkL6yUM&dq=contrail factor high bypass&pg=PA233#v=onepage&q&f=false


See also:
https://www.metabunk.org/threads/engine-efficiency-high-bypass-and-contrail-frequency-how-much.226/

So what did the theorists get wrong?

This theory is particularly odd in the context of the chemtrail theory, as that normally claims that in previous decades (generally the 1980s and before) there were no persistent contrails, and that the contrails we see now are something new. But this new spin on the chemtrail theory seems to be arguing the opposite - that older planes would make contrails, and new planes will not.

The thinking behind the "high-bypass = no contrails" seems to be the idea that the contrail is made from the air that an engine pushes backwards. This is incorrect - simply pushing air does not create an exhaust contrail. An exhaust contrail is created from, as the name implies, the exhaust of the the engine.



The exhaust of the engine is the gasses that come out of the combustion chamber. It's the product of burning kerosene (hydrogen and carbon) with the oxygen in the air, and the result is carbon dioxide and dihydrogen monoxide (water). It's the water in the exhaust that makes the contrail. And the exhaust gasses are basically the same regardless of if it's a low-bypass, no-bypass, high-bypass or even an internal combustion engine.

What creates a contrail is the mixing of the exhaust with cooler air. It does not matter if it's mixing with the air that passed through the bypass fan, or if it's mixing with the air that passed around the engine. It's still just exhaust gases mixing with the air. As the gasses mix, the temperature falls, and the water condenses out.

The only difference with a high bypass engine is that the exhaust gasses in a high bypass engine are a little less hot (more of the energy has gone into producing thrust from the bypass fan). So they reach the condensation point quicker, and so are more likely to form contrails.

In reality, any plane can make a contrail. High bypass, low bypass, no bypass, even prop planes will make contrails. And they always have.

 

[MikeC]

The following is the text of a posting I made about this on ATS a couple of months ago titled "How many times can a contrail believer be wrong?". As some with noted, the answer is blowing in the wind

And so...:

Global Skywatch has published something that I am sure they think is the definitive Truth about Contrails, but the truth about this is that it serves only as an illustration of how many "facts" can someone get wrong in a short bit of writing!

Every Condition is Wrong for Contrail Formation
The formation of condensation trails requires high vacuum,

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there is no such thing as "high vacuum" - perhaps he means "low pressure"? And of course that is wrong- contrails will form at sea level if the humidity and temperature are suitable - hence "ice fog" in Alaska!

cold temperatures, and high humidity, however, the output side of a jet engine contains mostly outside air that has been pushed through the engine by the large ducted fan (The ducted fan is the set of spinning blades that you see when you look at the front of the engine). This high-pressure at the output of the engine is contrary for the formation of condensation trails because pressurized air has the ability to hold much more water in suspension, without condensation.

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Actually this is more-or-less correct - albeit in a pidgin-technical manner - denser air such as that compressed by a turbo fan will hold more moisture. As long as it remains denser of course....which isn't very long once it leaves the engine!

A fraction of the air that enters the engine is taken in by the turbine engine. This air is mixed with jet fuel (essentially kerosene), combusted, and then exits the engine under very high pressure and high temperature. Condensation formation requires a decrease in ambient air pressure to form, but the output of the turbine is under very high pressure which prohibits the formation of condensation trails.
Physics also tells us that condensation forms when air is cooled, but since the exhaust of the turbine engine within a jet is very hot, condensation formation is - once again - prohibited.

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lol - and that is why the contrails do not form at the output of the turbine, and why they form some distance behind - when the pressure is rapidly reducing - thus also rapidly reducing the temperature!

Furthermore, the ratio of air-to-fuel used in turbofan engines is as high as possible (lots of air but relatively little fuel) so as to keep engines efficient and cost-effective, and this lack of fuel in this ratio results in a lack of water vapor; yet another reason jet turbofans cannot produce condensation trails.

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There is no lack of fuel "in this ratio" - all jet engines seek a "perfect" mixture, which IIRC is about 14:1 air to fuel - some get closer than others, but there is always fuel!!

In short, the more efficient the engine, the less fuel it uses per unit of air moved, and this renders turbofans incapable of producing condensation trails, unless they use water injection (see section below).

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Using less fuel does not render them "incapable" even by his own reasoning - it should render them less LIKELY by simplistic reasoning - however other considerations actually make it MORE likely- put simply the higher the efficiency of the engine, the higher the temperature at which contrails can form, and so the more likely they are to do so - the math is in the link if you want to examine it closely.

Simply said, every condition necessary for contrail formation is absent in a high-bypass turbofan engine.

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simply said this guy is [wrong]

If you go to an airport and watch jets take off, you will see that they emit a faint trail of black soot, which is typical of burnt jet fuel (kerosene), but you will not see water vapor.

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WATER VAPOR IS INVISIBLE - YOU NEVER SEE IT!!

 

[Mick West]

While that's all true, the reason I posted this new debunk (over TWCobra's) is that your rebuttals (while accurate) will be viewed as as simply opinions. I'm trying an approach of just giving references.

 

[Hama Neggs]

Do we have a version of this vid here for debunking? Maybe it needs to be specifically addressed as well.


Dane Wigington is touting this vid as being the 'slam-dunk' end to all arguments concerning contrails vs chemtrails.

 

[Hama Neggs]

At about 49:00 in this show, Dane Wigington claims to have heard from "an engineer that works at Rolls Royce jet engines" who told him that the info in that vid is "spot on - it's correct". I can only guess that Dane is just flat lying about that.

http://globalskywatch.com/assets/mp3/gwradio/2014-02-22.mp3

 

[Mick West]

At about 49:00 in this show, Dane Wigington claims to have heard from "an engineer that works at Rolls Royce jet engines" who told him that the info in that vid is "spot on - it's correct". I can only guess that Dane is just flat lying about that.

http://globalskywatch.com/assets/mp3/gwradio/2014-02-22.mp3

What more debunking is needed other than what is in the first post?

And if you want a point-by-point, the second.

 

[Hama Neggs]

What more debunking is needed other than what is in the first post?

And if you want a point-by-point, the second.

If Dane is going to specifically point to the vid as proof of something significant, the debunk should prominently include the vid, I think.

 

[KC-10FE]

A pretty good video of a KC-10 with contrails

Engines: General Electric CF6-50C2 High Bypass turbofans; Fan: 73%, Core: 27%

 

[Efftup]

They have also missed , possibly on purpose, another point here with their descriptions.
A higher PERCENTAGE of the air going into a High Bypass Turbofan does not go through the combustion chamber, BUT
look at the SHAPE of the engines:

I would say that just by looking at them, it would be fairly obvious that a similar amount of air is going into the combustion chamber in both engines, but the newer one sucks in LOADS of extra air to lower the overall output temperature and to increase fuel efficiency.

 

[Balance]

Yes. Fuel requires a certain amount of oxygen to burn. For efficiency, there is an optimum balance of oxygen/fuel known as stoichiometric combustion http://www.engineeringtoolbox.com/stoichiometric-combustion-d_399.html

I'm pretty sure this means, regardless of how much air bypasses the combustion process, the engine still needs to consume the same amount of air per fuel into the combustion chamber to get the most efficient burn.

 

[Hama Neggs]

They make such a big issue about the air passing through the fan. It's no different than if it was a propeller (or if it wasn't there at all) in terms of contrail production. Of course you can't present such points to the likes of Tanner or Wigington- they are protected from direct engagement on their claims.

 

[TWCobra]

They make such a big issue about the air passing through the fan. It's no different than if it was a propeller (or if it wasn't there at all) in terms of contrail production. Of course you can't present such points to the likes of Tanner or Wigington- they are protected from direct engagement on their claims.

Agreed. The numerous photos available of propellor aircraft making contrails should be enough. Once again however one of their brethren, in this case Jack Baran, makes something up and confirmation bias does the rest.

 

[Hama Neggs]

Agreed. The numerous photos available of propellor aircraft making contrails should be enough. Once again however one of their brethren, in this case Jack Baran, makes something up and confirmation bias does the rest.

They say something "science-y" sounding about 80-90% of the air not being "combusted", whatever that is supposed to mean, as if the same thing isn't true about all the air which passes around the combustion chamber in any other jet engine ever built, whether it passes through a fan or not.

 

[WeedWhacker]

They say something "science-y" sounding about 80-90% of the air not being "combusted", whatever that is supposed to mean...

Yes, indeed.

Combustion of a fossil-based fuel (in internal combustion engines, as they are termed) requires the fuel to be "atomized" (another unfortunate term, that is commonly used). It means that the liquid is shot through very fine nozzles, so that as it mixes with the air, it becomes "combustible".

(A bit similar to your normal "rattle can" that sprays paint. The paint is a liquid, and is combined with a gas inside the can....so the paint itself is "atomized", mixed with the propellant [the gas] and thus sprays out...forced through a very small nozzle. No "combustion" in this scenario, because that is not the desired effect! Although, some pranksters have found a way.... ).

BUT, when you want a fuel-air mixture to ignite and 'combust', then you extract energy from that combination. (This is also happening in the pistons of your car's engine...unless you own a Tesla!).

Now, having written all of that....a High-Bypass TurboFan engine STILL needs to extract energy from combustion. The significant thing about these types of jet engines is: They DO produce MORE pronounced contrails, and this is directly related to the amount of air that is "bypassed"...which acts as a sort of 'shroud' that contains the hotter air (that has undergone the combustion cycle, in the fuel/air mixture). The hotter air in the core, or center of a column (a horizontal column, in this case) encircled by the cooler 'bypass' air. Thus, increasing a mixing effect, and affecting the surrounding atmospheric effect on the hot exhaust.

 

[MikeC]

And while high bypass ratio fans are certainty more efficient, it is not by order of magnitude, so they still burn more fuel to produce more thrust.

Eg the specific fuel consumption (SFC) of a Jt3D common in the days of 707's and DC-8's is ~0.78 lb/(lbf·h) (22 g/(kN·s)) @ 4000lbf thrust M 0.82,35000ft,ISA

For a Rolls Royce Trent 500 HBR it is 0.54 lb/lbf-hr (at cruise) - so this is almost 50% more efficient assuming cruise is also at M0.82 and 35,000 ft ISA.
(both figures from the respective wiki pages)

assuming the cruise thrust is the same ratio as the max sea level thrust (which it probably isn't, but for illustration purposes), the Trent 500 will be making 56,000/17,000 * 4000lbs = ~13,176lbs. And to do so it will burn 7115 lbs/hr to do so.

The JT3D will be burning 3120lbs/hr.

So the newer high bypass ratio engine is burning 2.28 times as much fuel as the older engine.

 

[WeedWhacker]

So the newer high bypass ratio engine is burning 2.28 times as much fuel as the older engine.

But of course, is producing more thrust (?)...yes? Which is the point. For ever, and ever larger and heavier airplanes. (Talking commercial passenger jets, here).

EDIT: But of the specific science, and the "numbers" just make some people's eyes roll back into their heads. The MAIN point here is: "High-Bypass TurboFans DO produce contrails".

 

[MikeC]

But of course, is producing more thrust (?)...yes? Which is the point. For ever, and ever larger and heavier airplanes. (Talking commercial passenger jets, here).

Yes - ~13,000 lb vs 4000 lb - 3.25 times as much thrust for 2.28 times as much fuel.

 

[WeedWhacker]

Yes - ~13,000 lb vs 4000 lb - 3.25 times as much thrust for 2.28 times as much fuel.

YES!! SO, we see more efficiency, per "unit" of fuel consumption. Which IS THE POINT of inventing better jet engines.

"Side-Effect"(??) More pronounced, often more persistent contrails.

 

[cloudspotter]

YES!! SO, we see more efficiency, per "unit" of fuel consumption. Which IS THE POINT of inventing better jet engines.

"Side-Effect"(??) More pronounced, often more persistent contrails.

More persistent? Isn't that a function of the RH once the contrail has formed?

 

[Trailblazer]

More persistent? Isn't that a function of the RH once the contrail has formed?

It is, but high-bypass engines produce persistent trails in conditions that older engines would not. (If you compare the charts for contrail formation in the opening post of this thread, you need lower RH for persistent trails at a given temperature with high-bypass engines than with low-bypass ones.)

 

[cloudspotter]

It is, but high-bypass engines produce persistent trails in conditions that older engines would not. (If you compare the charts for contrail formation in the opening post of this thread, you need lower RH for persistent trails at a given temperature with high-bypass engines than with low-bypass ones.)

Forming or persisting?

 

[PCWilliams]

The color image above and the black & white image in the PDF file (http://tinyurl.com/oqdagjq) (Figure 7) are not the same images. Just an observation.

 

[Mick West]

There's a color version of the B&W image here:
http://core.kmi.open.ac.uk/download/pdf/11132500.pdf


And here:
http://wakenet.eu/fileadmin/user_upload/2nd_major_WN3E-Workshop/presentations/WN3E_Session_special_Burkhardt.pdf


Here's a video from inside the plane on a different mission.

 

[Efftup]

the OTHER thing they neglect to mention when talking about how much of the air is NOT going into the combustion chamber is how much BIGGER the cross section of a modern Hi Bypass turbofan is compared to an old style engine.
a JT3D has a 1.31m diameter. The Trent 500 has a 2.47mm diameter.

So it has an 88% bigger cross section in the first place, as well as other fan shapes etc .

I am not 100% certain of my maths on this one so please feel free (as always) to correct any mistakes.

A JT3D has a bypass ratio of 1.42:1 and an air mass flow of 196kg/s. Therefore the actual amount of air going into the combustion chamber is 196/2.42 = 80.99kg/s.

A Trent 556 has a bypass ratio of 7.6:1 and an air mass flow of 879kg/s so therefore the actual amount of air going into the combustion chamber is 879/8.6= 102.2kg/s.

 

[Mick West]

Bunnykins digressions/misunderstandings/etc. moved to
https://www.metabunk.org/threads/bunnykins-on-high-bypass-turbofans-and-contrail.5829/

 

[Mick West]

and somethgblue's digression moved to:
https://www.metabunk.org/threads/somethgblue-on-science-vs-personal-truth.5830/

 

[Belfrey]

Russ Tanner made a post about the Schumann and Busen article yesterday on GlobalSkyWatch. The argument mostly consists of assertions that the article is incorrect, and an example of intentionally faked, false scientific evidence:

In hundreds of cases, thousands of pages of fake studies have been published in professional journals touting research that was never done by doctors who don't even exist. Other studies were completely fabricated while real doctors were paid (bribed) to have their names falsely placed as the authors of the fictional studies. Unfortunately, This is how the world works today and is a fact that the public has become much more aware of. The art of controlling a population using false science is called "Scientism".

This contrail study happened to be conducted in 2000; at the same time governments were dramatically increasing their chemical-aerosol spraying program. Despite the fact that turbofan efficiency has been steadily improved since their initial design, this study came out at the same time the public was getting concerned about widespread aerosol lines saturating their skies day after day. This study appeared just in time to quell public concern about the massive and sudden changes witnessed over our heads. In fact, a lot of disinformation came out during this time which opposed the emerging truth that spraying was occurring. This disinformation attempted to convince the public that contrails are common despite the fact that it is virtually impossible for high-bypass turbofans to produce contrails at all.

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Tanner then makes some familiar errors:

For example, we know that contrails can only form at high humidity (70% or above) and low temperature (-70 degrees Fahrenheit) conditions, however, cold air cannot hold much water and therefore this condition is very rare. These statistics are directly from the NASA website, but have since been removed.

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The actual temperature figure is less than approx. -40 degrees (C or F, as they are the same at that point), and it's approx. >70% relative humidity that is pertinent, i.e. the amount of moisture relative to the saturation point at that temperature. These approximate values can be found in scientific papers published at least as far back as 1953. This paper by Knollenberg ("Measurements of the Growth of the Ice Budget in a Persisting Contrail," 1972), for example, examined the the development of a contrail and documented the conditions at which it formed:


Russ then repeats the claim that turbofan engines are less likely to make contrails for the following reason:

Also, we know that small portions of water occur in turbofan exhaust from the combustion of jet fuel, yet more efficient engines use less fuel and therefore have less water in their exhaust. The more efficient an engine is, the less fuel it burns in ratio to the amount of air it ejects making the engine less capable of producing condensation trails, the exact opposite conclusion drawn from the study.

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[deirdre]

Russ then repeats the claim that turbofan engines are less likely to make contrails for the following reason:

this is pretty much off topic but reminded me of a question. you know how if i dont change the oil in my car regularly i butn more fuel? do airplanes use oil like a car? and if so do they have to change the oil everytime they land?

 

[WeedWhacker]

do airplanes use oil like a car? and if so do they have to change the oil everytime they land?

The oil in a turbine engine is used for the same purpose as in an automobile...lubrication.

Oil in airliner engines is changed regularly (per prescribed maintenance protocols, as per the engine manufacturer and governing authorities' procedures), but not after every flight, no.

Also, the notion that not changing one's car engine oil regularly results in higher fuel burns? Well...not that simple. IF one were to severely neglect the car engine (by letting it continue to operate with very dirty oil) then yes....there will be erosion of the mechanical surfaces and this could result in higher fuel consumption levels...but only a tiny and almost insignificant amount compared to the repeated need to keep adding oil!! (LOL)...since such 'abuse' to an engine would mean it would not only burn the gasoline, but also the oil that was not meant to get into the combustion cycle at all.

If you see an old jalopy (like me!) with bluish smoke coming out the exhaust? That is oil being burned, in combustion.

Eventually you will face a more expensive bill than higher gas prices....either a ring and/or valve job, or even an entire engine replacement (if it goes that far).

 

[MikeC]

Actually we would never change the oil in jet engines - just top it up!! Except at engine change of course, when it has to be emptied.

However modern turbine engines use quite a bit of oil compared to cars - because they operate at much higher stresses they are "looser" when cold and "tighter" when hot. Oil consumption is recorded in the maintenance logs - how much is used to top up at each stop.

 

[blargo]

My memory of this is that they look for metal in the oil and based on the type they can make a good guess what part needs to be replaced.

 

[Jay Reynolds]

The oil in a turbine engine is used for the same purpose as in an automobile...lubrication..

Even though reciprocating piston engines and gas turbines are both internal combustion engines, the oil in a piston type engine is more directly exposed to the gases of combustion than oil in a continuous combustion gas turbine. Pistons and their piston rings have a direct contact with combustion gases and require lubrication while a turbine engine has no parts within the hot gas path which require lubrication. Because of this intimate contact with combustion gases, the oil in a piston engine becomes contaminated with acids and carbon from combustion and therfore eventually turns black and acidic and must be replaced. Oil breakdown in a properly running turbine is mainly a factor of temperature and time rather than contamination.

 

[WeedWhacker]

My memory of this is that they look for metal in the oil and based on the type they can make a good guess what part needs to be replaced.

This is a common factor in some turbo-prop engines. There are sensors in the oil system that will detect very small particles of metal....depending on the airplane, it is usually referred to as a "Chip" detector. Such a sensor will then illuminate a warning light, (often merely called a "Chip Light") appropriate to the engine where a "chip" was detected in the oil.

Rest assured that the on-going maintenance, and also design of the large turbo-fan engines used on modern airliners have sufficient safeguards and procedures....including many levels of filtering during operation, and inspections during "ground-time" as part of routine inspection protocols.

 

[MikeC]

SOAP sampling was (20 years ago - I forget what the acronym stands for - Standard Oil Analysis Procedure??) a routine analysis that was done on oil samples - it was different from analysis of chips on chip detectors or metal in filters.

SOAP looked at things like chemical contaminants as well as metal particulates to give some indication of engine health every few hundred hours.

Fragments on chip detectors are a sign of failure somewhere rather than condition monitoring.

 

[blargo]

SOAP sampling was (20 years ago - I forget what the acronym stands for - Standard Oil Analysis Procedure??) a routine analysis that was done on oil samples - it was different from analysis of chips on chip detectors or metal in filters.

SOAP looked at things like chemical contaminants as well as metal particulates to give some indication of engine health every few hundred hours.

Fragments on chip detectors are a sign of failure somewhere rather than condition monitoring.

Well that dates me, I worked TF-39 and TF-33 from 1985-1990.

 

[MikeC]

I was working on JT8D's, ALF502's and PW120's at the same time. We did SOAP on all of them and also on the APU's - IIRC it was actually offered free by Mobil - covered by the cost of Jet Oil II!

 

[GavinMacQueen]

Great thread! Does anyone know how exactly the myth about high bypass engines "NOT" producing contrails get started?

 

[TWCobra]

A Canadian guy called Jack Baran made it up.

 

[Hama Neggs]

A Canadian guy called Jack Baran made it up.

Seems so, and then Russ Tanner and Dane Wigington promoted the heck out of it.

 

[TEEJ]

Great thread! Does anyone know how exactly the myth about high bypass engines "NOT" producing contrails get started?

See following for Jack Baran.

https://www.facebook.com/jack.baran.376?pnref=story

https://www.youtube.com/user/catagd/videos

http://www.executivereasoning.com/turbofan/

http://www.drinkplentyofwater.com/

http://www.oocities.org/healingsecrets/filters1.html