Wikipedia talk:WikiProject Aircraft/Specifications survey

17 July 2005

This survey is now underway. Please take further discussion to the WikiProject Aircraft talk page

Could we have a link back to the Project talk page so people will have an overview of the debate before voting --Sylvain Mielot 6 July 2005 20:26 (UTC)

Lommer's comments

My thoughts:

1. It should be noted that for speed and range, a metric conversion will always be applied and present in the page. (i.e. if two imperial units are used, that will make a total of three units in the specs)
2. The comments section should be deleted - comments should go on this talk page instead.
3. Other additions/clarifications/deletions should not be present, if there are contentious issues, they should be identified here and presented as explicit poll options.
4. The "(current standard)" markings are very useful. For questions where there are pages using more than one option, would it be possible to get some idea of the number of pages using each? (not that important)

Other than that, I think this poll is great and that we should get it going ASAP. -Lommer | ^talk 7 July 2005 02:04 (UTC)

Thanks for the kind words.

1. I've implemented your first suggestion straight away.
2. I've removed the section and replaced it with an "other" response to some of the questions. Better?
3. I've now stated an explicit purpose for the section. Better? (Of course, it would be nice to hear of any other issues before polling starts, but we can't be sure that we will, particularly since some participants won't be aware of the survey until it's ready to be listed as underway).
4. I don't think there's any reliable way of knowing. The only figures I have are estimates on how many articles carry/have carried the current standard (around 650-700 out of a total of around 1,550). Would these figures be useful somewhere in the preamble? I'm cautious about it getting too long-winded...

Rlandmann 7 July 2005 03:54 (UTC)

I figures that #4 wasn't really feasible, it was just a thought. Kudos on all your other edits. -Lommer | ^talk 7 July 2005 19:16 (UTC)

Flaws in the survey

The biggest problem is a "one-size-fits-all" attitude. Well, not exactly one; in the templates Ingoolemo implemented, there were too. Apparently too many of you think that the only significant distinction to be made is whether to put English units first or metric units first. Oh, sure, there is also a defacto clumsy distinction between those giving power in watts and those with thrust, and an optional "armaments" field.

The notion that all the units of measurement have to be specified for either inclusion or exclusion is part of the nonsense. There is no reason we cannot say that certain ones should be used, at least in certain contexts, and there are others which might be included or not. The proposed survey is often not seeing the forest for the trees, and dealing with a lot of picky details that might be better dealt with in broader pricniples.

What should be standard is the order of the broad categories, which don't necessarily have to be specifically broken down that way, such as physical dimensions and weight, engine, performance, and tools.

Whether or not it should have a template depends on how the information is presented. The main advantage a text listing has is greater flexibility in presenting information. That is a stupid format to try to force into parameterized templates.

Infobox (in the conventional narrow, upper right format usually found on Wikipedia) and "text" list aren't the only options. We can have a table near the end of the page as well, and tables can be with or without lines, with or without color changes, etc. A table there might well present the information so that it is much more easily picked out than it is in the current listings.

There are several different ways of using templates. I don't even understand all of them. Explain better what you have in mind.

This survey and the example Editing Template talk:Aircraft-jet-mil illustrate one major problem in the paramerized templates. This example has been drawn up identifies many variables as "imp" and "metric". First of all, you get on my bad side right away by calling these units "imperial"; that is not standard terminology in the United States, where "imperial" is only used to identify those gallons and the other volume units based on them, which were invented and introduced in the 1820s. We don't call feet and pounds "imperial" units in the United States.

But the bigger problem, as shown in this survey and in things not yet included in this survey, is that there are often more than one metric unit and more than one "English" unit (calling it that pisses off some other people, of course) that are used to measure the same quantity. There are often differences in this regard based on type of aircraft, other differences are regional based on geographical location, and still others are mostly time-dependent.

Another spec calculated from other specs given is wing loading.

Another quantity for which other units are used include rate of climb. For many users, the standard metric units are meters per second, not meters per minute, the units most often used in the Wikipedia articles. This usage may vary among different kinds of aircraft.

Not enough attention is given to various distinctions, such as

How many zillion different things get put under the field called "Capacity" on the page content page? Apparently this is implemented in the "pilot" and "crew" categories in the Aircraft-jet-mil example. It includes passengers on passenger liners, and many other things such as volume of cargo area, fuel capacity of tankers, etc. in various Wikipedia articles.

What factors are relevant when you discuss special purpose aircraft such as crop dusters, fire fighting planes, flying cranes, etc.?

What information is really relevant in a passenger liner? In a fighter? In a bomber? In a surveillance aircraft? In a towplane for gliders?

1. military vs. civilian
2. engine types including not only piston engines and jet engines, but also rocket engines, no engines, and even a couple of human muscle engines in the general category of aircraft.
3. passenger vs. cargo vs. special purpose
4. fixed wing vs. rotary wing
5. special purpose civilian aircraft
6. lots more

Maybe somebody should just go through as see what useful information a couple of editors have discarded, when they shoehorned the given information into the so-called "standard"? Wouldn't that be a good idea, if we want to see whether or not additional information should be included? Could those of you who have been doing this tell us a little bit about what you have thrown away? Surely you've noticed that you often have a few thing left over after you'll filled in whatever blanks you could. Gene Nygaard 7 July 2005 06:55 (UTC)

Just a few issues to address then :)

I can't speak for others, but to me, specifying particular units for inclusion or exclusion is important because standardising this provides comparability between different aircraft. Are the engines of the F-15 Eagle "more powerful" than those of the Sukhoi Su-27? We can immediately get an answer because the information in the two articles is presented in a consistent, standard way. In this example, you can compare them in lbf or in kN, whichever you are more comfortable with. This survey asks whether people here think that we should offer this comparison in kgf as well.

Certain characteristics are basic and instrinsic to all aircraft, fixed-wing, rotary-wing, powered, unpowered, civil, military, Latvian, Pakistani, flown in 1911 and flown in 2005. These are the characteristics that the specification section has always attempted to detail. But these aren't the only numbers that are ever going to be important. An article about a water bomber should probably say how quickly it can scoop up its load - which is a figure that should feature prominently in the article. An article about an STOL plane should mention its take-off and landing performance, but that doesn't mean that this must be placed in the specifications section.

I'll incorporate your advice on table vs infobox, on wing loading, and on units for rate of climb.

Capacity has always been intentionally broad - is there a problem with it being used to describe different things for different aircraft?

In my experience, the only specification that is contributed with any great frequency that is not part of the current standard is cruise speed, which I'd certainly like to see included. It's a widely-cited specification. Other than that, unit cost shows up from time-to-time, as do landing and take-off roll, and fuel capacity. Generally, even first-timers contribute more-or-less what the standard asks for. This is no surprise, since the data set for our standard is very similar to the data sets for most of the sources that they're using to contribute from. And then, there will always be someone who wants to specify the distance from the ground to the centreline of the propeller hubs of the inboard engines. A uniform standard allows for less-frequently contributed pieces of data to be dealt with equally across the project. ("If that article has that measurement, why can't I specify the diameter of the oil cooler inlet?")

Finally, this is a project to create an encyclopedia. It is not an anarchy. My impression is that few (if any) aviation encyclopedias or general reference works use one set of units to describe one aircraft and a different set to describe the next, and that such works generally adopt a single set of core specifications to describe aircraft. Is this other people's impression as well? --Rlandmann 7 July 2005 11:47 (UTC)

• I agree with Rlandmann on pretty much every point. -Lommer | ^talk 9 July 2005 00:16 (UTC)

Landing weight is another fairly common spec. Gene Nygaard 06:03, 13 July 2005 (UTC)

In some reference works, yes. In contributions here, very seldom. I've seen G-limits more often than landing weight, and they're rarely contributed. --Rlandmann 09:57, 17 July 2005 (UTC)

Fairly often here, too. That's why I mentioned it. I suspect more often than you will find in current articles, with some discarded in past "standardizing" of the specs format. Gene Nygaard 12:09, 17 July 2005 (UTC)

couldn't be bother to wait that long

So I filled the survey in anyway GraemeLeggett 7 July 2005 09:28 (UTC)

Abbreviation

I remember that there was a lot of hot debate over the proper abbreviation for knots statute miles, and nautical miles. Specifically, should knots be kt or kts? should statute mile be abbreviated sm or mi or something else (and is sm even a valid abbreviation)? and should nautical mile be nmi or nm?

Unless the issue was resolved, those questions should be included in the survey.

The above was left by Ingoolemo.

• I would think that sm's use used as an abbreviation in many gov't of Canada publications makes it a valid abbreviation. Whether its use is correct in wikipedia is a valid survey question though I suppose. -Lommer | ^talk 9 July 2005 00:12 (UTC)

You can also, of course, find "mi" in many government of Canada publications. More than "sm", I'll bet. Gene Nygaard 12:10, 17 July 2005 (UTC)

Power/mass

Why is it power/mass and not the obvious (and more readily understood by the non-plane buff?) power/weight ? GraemeLeggett 11:39, 12 July 2005 (UTC)

Because of arguments here in the distant past over the units to use for weight! (IIRC, also one of the reasons why our specifications simply say "Empty" rather than "Empty weight"). Since weight is a force, we would have to specify it in lbf and kgf if we were being technically precise. So we've side-stepped the issue.

A quick Google (flawed as the technique is) gives some idea of the relative usage of power/mass and power/weight (compare also this and this), and supports what you say about the latter being the obvious one to use.

To add to the confusion, in the industry, aircraft are typically specified the other way around - in "Power loading", ie kg/kW and lb/hp. So again, we have to decide whether to lean in the direction of aviation convention, or in the direction of what's going to be most intelligible for most of our readers... --Rlandmann 13:04, 12 July 2005 (UTC)

The units to use for weight depend, of course, on the meaning of the ambiguous word weight which is being used. The "since weight is a force" statement is not a universal truism. That is true for a physics jargon meaning of the word weight, one of several meanings we use in various contexts. Weight is never a force when anybody talks about "net weight" or "troy weight" or "carat weight", for example. It isn't a force when people talk about empty weight and loaded weight of aircraft either; this is properly measured in kg or lb as it should be, not in units of force such as kgf or lbf or N or pdl. It would not be "technically precise" to use those units of force; your option is to not use the word "weight"; it is not a valid alternative to continue to use the word, but to misapply a definition inappropriate for the context. As NIST tells us, [1]

• "Thus the SI unit of the quantity weight defined in this way is the newton (N)"

but also

• "Thus the SI unit of the quantity weight used in this sense is the kilogram (kg)". Gene Nygaard 14:08, 12 July 2005 (UTC)

Graeme, you have the same problem, of course, with the thrust-to-weight ratios. The denominator in either case is the very same measurement, a measurement of mass in the physics jargon meaning, often and quite legitimately called weight (which is usually used with a different meaning in physics jargon).

Of course, Graeme is already well aware of that, as are many others involved here, from the fairly frequent use of units such as N/kg and lbf/lb for the thrust-to-weight ratios.

The only difference is that the thrust-to-weight ratios are often pretend-dimensionless. They aren't really dimensionless, of course, but historically the users of these measurements have often pretended that pounds force cancel out pounds or kilograms-force cancel out kilograms. You can even make the dimensional analysis work out by throwing into the formula a gratuitous g_n factor, something not called for by the physics involved, but only there because of the units of measurement used. That standard acceleration of gravity g_n is not a concept of physics; it is strictly a concept of metrology, and only useful when you use gravitational units such as pounds-force or kilograms-force.

By dividing by g_n, you do not get "weight" in the physics jargon meaning of the word either; for that you'd need to divide by the local acceleration of gravity instead. What you get by dividing by g_n is a measurement of mass expressed in terms of units of force, something often called "Earth weight" or "standard weight", something which has nothing to do with the actual local acceleration of gravity.

Using "dimensionless" thrust to weight is equivalent to giving power to weight (power to mass, same thing no matter which term anybody uses) in units of watts per newton (with appropriate prefix) instead of the normal watts per kilogram. (I don't think I've ever seen anybody do that.) In terms of base units of SI, 1 W/N = 1 m/s, but for the correct units and the ones used 1 W/kg = 1 m²/s³. —Gene Nygaard 14:08, 12 July 2005 (UTC)

So are we going to use power/mass or power/weight? Question for the survey perhaps, to avoid filling up discussion space here? GraemeLeggett 15:02, 12 July 2005 (UTC)

Thrust-to-weight is usually expressed as a unitless ratio when describing aircraft and aero engines. It really doesn't matter whether any one of us believes that this is a sensible convention or not; Wikipedia is not a soapbox. One can choose to view the ratio as meaning kg/kg (using kg to colloquially measure thrust), kgf/kgf (using kgf to measure weight in a physical sense), or simply and annoyingly making no sense at all; in any case it does not alter the fact that this is the way it is usually expressed. --Rlandmann 12:26, 15 July 2005 (UTC)

There is a difference in "usually" and always. Newtons per kilogram are used by some experts in the field. So are lbf/lb and the like. By people who insist that that usage is the proper one. This isn't something otherwise unused, just dreamed up by a couple of Wikipedia editors. The use of a dimensionless number could justify the inclusion that way here; it doesn't justify the exclusion of other ways of expressing it. The only real question is if we need to express the exact same number both without dimensions, and with dimensions lbf/lb or kgf/kg.

For example, click on see first page at this link, which also shows this usage to go back more than thirty years:

Feasibility of Rotating Fluidized Bed Reactor for Rocket Propulsion

HANS LUDEWIG, A. JAMES MANNING, AND CHAD J. RASEMAN

JOURNAL OF SPACECRAFT AND ROCKETS 1974

0022-4650 vol.11 no.2 (65-71)

"The maximum thrust/weight ratio for a 90,000N engine was found to be approximately 65N/kg."

This very same measurement is sometimes called "specific thrust" rather than "thrust to weight". Some people use only one or the other; some use thrust-to-weight with dimensionless numbers and specific thrust when it is expressed in dimensions of acceleration (i.e., force divided by mass). But others use "specific thrust" even when they don't express any units. Gene Nygaard 12:42, 17 July 2005 (UTC)

Proposed triple unit solution is currently forbidden by Manual of Style

We have aviation and car articles where triple units are used, for example (kW, PS, hp SAE) or (km/h, knots, mi/h). The survey asks questions about this solution. However, an editor amended the Manual of Style to say multiple equivalents including metric are cumbersome and shall be avoided. Thus we have opposing conventions.

• I questioned the use of that phrase and others. See Permitting removal of metric units: inconsistency in the Manual of Style.
• I then made a proposal that would eliminate the clash. See Suggested rewrite of 'units' section in Manual of Style

Please feel free to join the discussion and raise the issues of aviation and car articles. Bobblewik  (talk) 11:31, 13 July 2005 (UTC)

"shall be avoided" is not an absolute. there won't be many situations - mostly russian aircraft and german engines - so it will occur only occasionally. eric ✈ 21:28, 17 July 2005 (UTC)

When I see shall statements outside Wikipedia, it is an absolute. The IEEE standards manual says:

• The word shall is used to indicate mandatory requirements strictly to be followed in order to conform to the standard and from which no deviation is permitted (shall equals is required to).

A non-absolute word is should.

That phrase was added without discussion by an editor that deletes metric units from articles. The rationale of that phrase and others is that metric units can 'interrupt the flow' and be 'cumbersome'. Removal of metric units by non-metric readers is now supported by the Manual of Style. If you follow the link I gave above, you can support those that want a revision to those phrases. Bobblewik 11:24, 18 July 2005 (UTC)

Last orders, please

Apologies all for my lack of progress on this for the last couple of days - Real Life stole some of my WikiTime. I intend to open the poll at 00:01 on 17 July. If anyone has any more changes to suggest, please speak up! --Rlandmann 12:54, 15 July 2005 (UTC)

Which weight?

Can I ask some? I don't catch up on the discussions here, but about wing loading and power/mass(wight) issues, I wonder which weight will you use? MTGW, "loaded"(in fact I don't understand this term completely. "usual condition" maybe?), or empty weiht? I guess you've got to specify when you talk about this kind of weight-involved quantities... However, since nobody seems to mention this point here, perhaps it's already solved? Or is it simply a silly quetion...? - Marsian / talk 13:05, 15 July 2005 (UTC)

As the standard was originally developed, the weight used for these derived specifications was to be "Loaded weight". This was set out on the page content page until removed on April 23 this year. "Loaded weight" is a specification in quite a number of reference works and is sometimes given as "Normal take-off weight", "Typical take-off weight", or something similar.

It is problematic because it does not correspond directly to anything used in the industry. When found in published sources, it seems to me to be mostly used to describe the MTOW of military aircraft when these same sources use terms like "Maximum take-off weight" to actually describe Maximum Overload Weight. --Rlandmann 14:29, 16 July 2005 (UTC)

Thanks, as usual.

About loaded weight, I think its meaning for fighters is rather clear: Take-off weight for "ordinal missions" (CAP or scramble maybe?), not the take-off weight for "Ferry mission" (or kind of that) with full of external fuel tanks. And latter may be its MTOW. Weit, er... no, I might be wrong; with aerial refuelings, MTGW may occur without fuel tanks, I thought...

Anyway, I guess I understand. Your "Typical take-off weight" seems to me the most suitable and easily understandable. // BTW, I'm sorry I'm not included your discussion... and sorry for my interruption, too (according to #Last orders, please, you must be busy, Rlandmann. You're very genial). - Marsian / talk 16:19, 16 July 2005 (UTC)

Hope I'm not too late

Ack, I hope its not too late. I just thought of something we should throw in - When is the earliest date at which we should revisit the consensus achieved by this survey. (with options of bi-weekly, monthly, 6 months, 1 year, 2 years, >2 years, never). By setting up something like that we can more authoritatively stick to a standard, though we can still evolve (i.e. if the template system gets improved). Can we throw this in now? -Lommer | ^talk 00:21, 18 July 2005 (UTC)

I've gone ahead and thrown it in. If I am in error it may be removed. -Lommer | ^talk 00:52, 18 July 2005 (UTC)

Range: statute or nautical miles

There is the comment implying that statute miles may have been used in original data for U.S.-built aircraft prior to the 1970s. That seems to me to mean that the nautical mile is the default non-metric unit. Does anyone know any more about this? Bobblewik 10:19, 23 July 2005 (UTC)