Talk:Jet engine

Caption of the photo of the first 747
The JT9D in the picture in the 'Uses' section is not undergoing maintenance. The airplane shown is the first 747, and it is on display in the Airpark section of the Seattle Museum of Flight. The engine nacelle has (most likely) been removed so that the inside is visible to visitors. I haven't made enough edits to be able to edit this caption, perhaps someone else can do it.

Merge proposal
I propose that Airbreathing jet engine be merged into Jet engine. The two topics are essentially the same. Although there are issues around the exact meaning of the term jet propulsion, that already has its own article and no reliable source (that I am aware of) has ever defined any actual kind of "jet engine" that differs from the airbreathing variety. Some definitions of jet propulsion include rocket propulsion but no definitions of a jet engine appear to include rocket engines, which also have their own article, while both are usually classified as types of reaction engine - another existing article. &mdash; Cheers, Steelpillow (Talk) 21:58, 9 July 2018 (UTC)
 * I Support a merge --Marc Lacoste (talk) 07:03, 10 July 2018 (UTC)
 * Support Andy Dingley (talk) 10:23, 10 July 2018 (UTC)
 * Support. I browsed a handful of sources covering aviation technology and thermodynamics (including Rolls-Royce’s The Jet Engine), and none use the term "jet engine" to mean something else than "airbreathing jet engine". I believe the distinction with non-airbreathing jet propulsion devices is already clearly made and well illustrated in the current article’s section "Other types of jet propulsion". Ariadacapo (talk) 11:54, 10 July 2018 (UTC)
 * Support: I have checked several college aerospace propulsion texts and none refer to non-airbreathing engines (e.g. rockets) as "jet engines". I have a bachelor's degree in aero propulsion engineering and have worked in the industry for 42 years, and never heard such a reference; I have no reason to believe the industry regards it as such. That "definition" is WP:original research which must be removed. Airbreathing jet engine is less well cited than Jet engine; the page is redundant, and what little that is good in the other should be merged here. JustinTime55 (talk) 12:32, 10 July 2018 (UTC)
 * Oppose On practical grounds. It's a silly idea. The two articles are too big to merge. They were originally merged but were separated due to size. Remerging will just make the resultant article too big again. GliderMaven (talk) 19:43, 10 July 2018 (UTC)
 * The split was made by, following a lone post six months earlier that had gained no consensus at the time of the split. That editor is now permanently blocked for being a Bad Bunny. If a split is still needed, then we could do one of two things:
 * Merge the two articles back together and then agree a scope and meaningfully different title for the new child article. &mdash; Cheers, Steelpillow (Talk) 20:48, 10 July 2018 (UTC)
 * First agree the new scope and title, then move Airbreathing jet engine across and update the content of both articles accordingly.
 * I have no real problem with either process, though I think that an initial merge and tidy-up should make it more obvious whether a split is really needed and, if so, where the cut should be made. &mdash; Cheers, Steelpillow (Talk) 20:48, 10 July 2018 (UTC)
 * We would do much better to merge jet propulsion and reaction engine to this one. They're both short articles, and are overlapping topics. Airbreathing jet engine is already a subarticle and isn't even the primary topic. GliderMaven (talk) 21:57, 10 July 2018 (UTC)
 * Jet propulsion encompasses a whole bunch of things, including rockets and pump-jets. I don't see it as ever being a terribly useful article as a result, but it fills an obvious conceptual space. Andy Dingley (talk) 23:17, 10 July 2018 (UTC)
 * But this article is already on that topic, and seems to be terribly useful, and as you note, fills an obvious conceptual space. GliderMaven (talk) 16:59, 11 July 2018 (UTC)
 * "The two articles are too big to merge": excess material should be moved in the relevant subarticles (Turbojet, Turbofan, Turboprop, turboshaft, Propfan, Ramjet, Scramjet, and Thrust with its 5 subsections), not in a dubious "airbreathing" concept.--Marc Lacoste (talk) 10:43, 11 July 2018 (UTC)

As for the merge itself, I see no objections to merging this article with the one on airbreathing jet engines and using the name "jet engine" for the merged article, as it appears to be the more common use of the term term by far among aeronautical engineers. The stuff about rockets etc that doesn't fit in the merged article should then be moved to the "jet propulsion" article, which is currently rather short. However, the new article should give both definitions in the lede, state that the current article uses the narrower definition because it is the most common interpretation among engineers, and then link to the "jet propulsion" article for details about engines that do not fit the narrower definition. Martijn Meijering (talk) 16:17, 12 July 2018 (UTC)
 * Neutral It has now been conclusively shown that the claim that "no definitions of a jet engine appear to include rocket engines" is false. Dictionaries show that two meanings of the terms "jet engine" and "jet propulsion" are in common use, a broader one that includes rockets and a narrower one that doesn't. It has also been demonstrated that the term "jet engine" simply means "engine that works by jet propulsion", just as you would expect from the everyday meanings of the words involved. Nevertheless it has also been more or less settled that the broader use of the term is very uncommon among aeronautical engineers, as we've heard several ones weigh in on that topic. That said, Sutton clearly belongs to a minority that does use the term that way. It would be nice if we could get an explicit citation of a RS that says the broader interpretation is uncommon among aeronautical engineers, but unless others object I'll be happy if we state so explicitly as it is.
 * Support – Too much fragmentation and duplication. Airbreathing jet engine seems to be mostly composed of chunks of the turbojet, turbofan, ramjet etc articles plus a summary of Components of jet engines. If you take that out, what's left (Engine cycle, Thrust lapse, safety aspects and Terminology) could fit, with a bit of trimming, into Jet engine without much trouble. It's irritating, especially to the uninitiated reader, having to jump back and forth between articles only to find a lot of stuff that you have just read about. --Deeday-UK (talk) 21:57, 12 July 2018 (UTC)
 * Support. The jet engine is always an airbreathing jet engine, so this is a distinction without a difference. Non-airbreathing engines that use some form of jet propulsion are referred to by other names, such as rocket engine or thruster. Binksternet (talk) 22:03, 12 July 2018 (UTC)

Discussion

 * GliderMaven, once again you have diverted attention from the main issue which is the tautology of "airbreathing jet engines" (not necessary to disambiguate jet engine) and the definition of rockets as jet engines. The size of the article is not an insurmountable reason not to merge, and does not justify WP:OR.
 * Also, Airbreathing jet engine (which is completely uncited) contradicts Jet engine by omitting all the other European and Japanese pioneers of the jet engine except the English Whittle and the German von Ohain; the top half of the former certainly can go in the dustbin. JustinTime55 (talk) 13:08, 11 July 2018 (UTC)


 * There's no OR tags on the article, nor could there credibly be so. On the contrary, size is a limit that you have no current plan to tackle, and is a critical issue. GliderMaven (talk) 16:59, 11 July 2018 (UTC)


 * I have a plan though. Turn this article into jet engine (jet propulsion) and airbreathing jet engine into jet engine (airbreathing), and then temporarily make 'jet engine' into a disambiguation. Then go through the internal links and move them across, manually. AFTER you've done that and sorted out all the links (there's over 500 of them), you could then point/move 'jet engine' over to jet engine (airbreathing).


 * In Jet engine (jet propulsion) you would then define thrust simply as Fn = Mf Ve (where Ve is the effective exhaust velocity, including any inlet drag and any pressure term), and in Jet engine (airbreathing) define it as Fn = (Mair + Mf) Vex - Mair, where Vex is the average exhaust velocity and move everything related to airducts, and I mean everything, sections on turbojets, turbofans, ramjets all moved over to jet engine (airbreathing). But stuff like propulsive efficiency that has nothing specifically to do with air ducts and is only to do with Ve, leave it in the jet propulsion article. GliderMaven (talk) 16:59, 11 July 2018 (UTC)


 * If you do that, in that order, then you've achieved everything you guys want, and have evened out the two articles as well. GliderMaven (talk) 16:59, 11 July 2018 (UTC)
 * Can you find sources that treat the jet engine as both the "jet propulsion" kind and the "airbreathing" kind separately, or is that just your own preferred way of covering the topic? Ariadacapo (talk) 17:18, 11 July 2018 (UTC)


 * Certainly. Merriam Webster defines it as: "an engine that produces motion as a result of the rearward discharge of a jet of fluid" and then adds a more specific definition as: "an airplane engine that uses atmospheric oxygen to burn fuel and produces a rearward discharge of heated air and exhaust gases". So no, since dictionaries record usage, both definitions are in use, no I didn't invent it, nor did anyone else in Wikipedia. GliderMaven (talk) 17:47, 11 July 2018 (UTC)


 * OK thank you. Ariadacapo (talk) 18:26, 11 July 2018 (UTC)
 * The term "jet propulsion" is ambiguous. It can mean specifically jet engine propulsion, as distinct from say rocket propulsion, or it can treat jet propulsion more widely as using any jet of fluid, in which case rocket propulsion is a form of jet propulsion. See for example the Collins dictionary definition. What has invented is the idea that any engine that works by jet propulsion must necessarily be a jet engine, regardless of which meaning is being used. &mdash; Cheers, Steelpillow (Talk) 18:28, 11 July 2018 (UTC)


 * Now you're just being insulting. GliderMaven (talk) 19:42, 11 July 2018 (UTC)
 * No, just open. You are welcome to either cite that idea or refute it, but refusing to do either leaves you open to such remarks. &mdash; Cheers, Steelpillow (Talk) 19:54, 11 July 2018 (UTC)


 * ? As I already noted, Wikipedia just uses the Merriam Webster definition. GliderMaven (talk) 15:58, 12 July 2018 (UTC)
 * Merriam Webster (or the OED) don't have any privileged position on WP, and layman dictionaries are rarely of great use for trying to define encyclopedic content. It goes with the territory that an encyclopedia will need a more technically detailed definition than dictionaries manage with. Andy Dingley (talk) 16:04, 12 July 2018 (UTC)
 * And you're just being disruptive with your edt-warring to keep re-adding rockets:
 * I would agree broadly with your presumed scope for "jet engine" and "airbreathing jet engine". However much better titles for these are, as everyone else seems to favour, jet propulsion and jet engine.
 * Jet engine is a large scope and will be a large article. We can manage that size by functional splits to well-defined sub articles such as history of the jet engine, turbojet, turboprop etc. That makes far more sense than a very unclear and largely overlapping break into "jet engine" and "airbreathing jet engine". Andy Dingley (talk) 16:02, 12 July 2018 (UTC)
 * I vehemently agree with here. In any case,, please stop changing the scope of the article (re-writing the lead…) before consensus is reached here. Ariadacapo (talk) 16:19, 12 July 2018 (UTC)
 * Huh? Isn't the longstanding consensus version of many years the one that does include rocket engines in the definition? Aren't we supposed to go back to the last version before the dispute until we reach a new consensus? If so, I don't think GliderMaven is the one who's edit-warring here. We clearly haven't reached a consensus yet, though I hope we're getting close. Martijn Meijering (talk) 16:23, 12 July 2018 (UTC)
 * It was a disputed split back in 2010, by an editor who managed to get themselves indef blocked twice under two different accounts, even before their socking was recognised. It has never been an accepted split, but the WP model is that a single-issue editor who cares nothing for disruption can force one viewpoint, just by their persistence. Andy Dingley (talk) 17:17, 12 July 2018 (UTC)
 * Thanks, that changes things, I didn't know that. Martijn Meijering (talk) 17:20, 12 July 2018 (UTC)
 * In the first half of the 20th century, Jet propulsion and jet engine pretty much meant the same broad class of largely experimental machines. In mid-century, rockets and turbojets became highly important for different applications. This caused a nomenclatorial split, with "jet engine" usually meaning air breathing turbine machines without airscrews sticking out. Rockets remained part of "jet propulsion" especially in scientific contexts, but mostly used their own name in popular, commercial, and engineering contexts. Yes, as encyclopedists it behooves us to embrace lexicological conservatism, but not archaism, so I think it better to follow this division that became conventional just a few decades ago. A sentence in the intro to the jet engine article ought to say something like, "Rocket engines also work by Jet propulsion and let it go at that. Jim.henderson (talk) 12:58, 29 July 2018 (UTC)
 * Actually, that's the main reason to not do this- we're not lexicographers, as encyclopedists we don't divide up articles on lexicographic lines- which is what this very ill conceived discussion is trying to do. If the article is on jet propulsion engines then rocket engines are a hundred percent on-topic. Or, if the article isn't on jet propulsion engines any longer and is only on airbreathing jet propulsion then you've changed what the article is about, and you have to go through thousands of internal links to work out whether they're still correct. GliderMaven (talk) 14:33, 29 July 2018 (UTC)

Split article?
We've just had an undiscussed and uncredited split of the thrust content. However this has moved it to Thrust, rather than a new article at Jet engine thrust. As thrust was a tiny article deserving vital article status as basic principle of physics, that's now a worse article than when the content was here. If we're going to split, we should split; not just move to an equally bad location. Andy Dingley (talk) 14:37, 27 September 2018 (UTC)
 * I readily confess that my choice of target may be poor. In the longer view I'm trying to make the present large article, and related ones, fit better with the suggestions in Summary style. The material I moved is a detailed theoretical study of one important aspect of airbreathers, and I figured it should go into a theoretical article. Yes, moving a fraction of this large article will make a small article several times bigger. The main alternative target I was considering was the airbreather one, and perhaps that would be better, or maybe someone can suggest an even better one. I am entirely open to suggestions in that vein, though somewhat less open to any idea that none of the several large detail parts of this article properly belong in various more narrowly focused articles. Making a new article would be something of a last resort, as there are already many related articles that, to my eye at least, look undernourished. If an alternative is decided in a couple days, it will just be a case of undoing my two edits and doing the agreed move, followed by a bit of cleanup for redundancy or article layout or similar reasons. Jim.henderson (talk) 15:43, 27 September 2018 (UTC)
 * Quicker than that. It is undone. I face an objection from an editor with an excellent track record, and for the thrust article an objection from a stranger with not quite the same concern. Those, together with a second reading of the moved material, were enough. Umm, wet thrust? Yes, I read that before moving it, but what was I thinking? This obscure detail doesn't belong in either of these broad articles. So, the choices narrow to finding a better existing home, or making a new article. Hmm, moving details to the particular kind of engine? Water injection, far as I know, is only for Fighter planes and not many of those. I shall look into that article, and Turbojet and maybe someone can make a better suggestion and save me from surrendering and accepting a new article. Jim.henderson (talk) 18:48, 27 September 2018 (UTC)
 * Hee-hee. Should have checked Water injection (engine) before showing my ignorance. Wet is old, rarely used anymore and was even a feature in an airliner designed in the 1960s. Jim.henderson (talk) 18:53, 27 September 2018 (UTC)
 * No, it's not time for a compromise. It's time for me to surrender unconditionally, having failed to find an alternative existing home, or to be rescued by a smarter editor who agrees with me, and I am sorry for the delay. Incidentally I am surprised at how many decades have passed since I paid much attention to developments in aircraft engines. Anyway, you seem to have exactly the right idea, so I propose that you go ahead and do the honor of creating a new article from the section. Jim.henderson (talk) 01:29, 1 October 2018 (UTC)

ETOPS discussion in lede
Why does the lede say, "This, combined with greatly decreased fuel consumption, permitted routine transatlantic flight by twin-engined airliners by the turn of the century, where before a similar journey would have required multiple fuel stops?" This seems to be confusing two entirely different issues. Aircraft had sufficient endurance to fly trans-Atlantic non-stops many decades before twins were allowed to fly the routes in passenger service. Fuel consumption had nothing to do with why twins weren't flying trans-Atlantic passenger routes until the 1980s. Twins weren't allowed to fly those routes even with fuel stops. The requirement was that they remained within 60 minutes flying time of an airport to which they could divert in the event of an engine failure.

If there had been airports close enough to each other such that they could have legally flown across the Atlantic with stops at those airports, then they could have equally legally just flown over those airports without stopping. As jet engines became more reliable, ETOPS began gradually increasing the flying time radii within which twins were required to remain from a possible diversion airport until trans-Atlantic and then trans-Pacific legs became legal. Vbscript2 (talk) 06:21, 21 April 2019 (UTC)
 * That sentence should just go. For WP:UNDUE (EROPS / ETOPS doesn't fit into the lead of jet engine), because ETOPS isn't about fuel consumptions, and mostly (as you note) that non-stop transatlantic flying was commonplace decades before the turn of the century. Andy Dingley (talk) 09:32, 21 April 2019 (UTC)

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