What does "weight" mean?

[Connetts]

Would someone take a moment and sort me out?

My profile explains my interest.

Curently I am working on a paper for submission to a refereed legal journal on the criminal liability of professional pilots. The readers will generally know even less about aviation than I do -- and I'm interested in aspects of the subject!

For context, I am referring to the statistics published by Boeing on accident ratess, and they refer to "commercial jet airplanes that are heavier than 60,000 pounds maximum gross weight".


I want to illustrate this figure by mentioning some types as examples. Is "m g w" == MTOW, which appears in some specifications??? The familiar B737 specifications, for example, give weights on either side of 60,000 lbs. It's the smallest a/c by Boeing and very common round here, and I just want to write a line or two in a footnote to make the text more interesting than the rather arid law I'm dealing with. What standard figure in manufacturers' specifications am I looking for?


For example, a detail which an interested reader of the SA Jnl of Crim Justice (to which I hope to submit the ms, and who knows nothing about a/c except that (s)he flies to conferences in one) might ask is -- "So what common type is just within the 60,000 lb range? Do I ever fly in one?"

Can someone give me illustrations of a/c at the bottom of the range, and somewhere in the mid-range? I assume that the 747, 777, and A380 are at the top. The Cessna Citation is outside, right?

To save clutter, it may be just as well if replies went privately to me as the question is really quite trivial to experts such as yourselves.

I would be very grateful for clarity, and will acknowldege the help in the usual manner appropriate for learned journals.

Thanks!

[kenparry]

The simple bit is that max gross weight is also MTOW. In Europe, the scientifically more correct term "mass" has now been used for some years, so the abbreviations become MGM and MTOM, but in practice there is no significant difference.

Then it starts to become messy. Boeing conduct certification testing for each model to a specific MTOW, which may vary with the engine fitted to a particular variant. Also, individual customers may choose in their purchase contract to "buy" a reduced MTOW - because overflight and landing charges are based on the declared MTOW of the individual aircraft. This "declared" MTOW can be varied, for a fee, by the relevant national aviation authority.

For example: I used to fly the B757, for which the Boeing MTOW was somting like 113398 kg (a strange number, but Boeing work in lbs), but the fleet, of identical aircraft, had a mix of declared MTOW which included figures of 112699kg and 103699 kg. From season to season, as the route pattern changed, the declared MTOW of individual aircraft would change.

Regarding the B737, I think you are confusing lbs and kgs. The B737-200 had MTOW varying from 49442 kg to 55111 kg among those I flew, and I think some went a little higher. The current B737-800 goes up to 79010 kg, according to the Wikipedia entry.

For a type under your 60000 lbs, try the Embraer 145, shown in Wiki as 46500 lbs for one variant.

The B747 started at around 735000 lbs and now goes up to 875000 lbs.

You can get lots of detailed info from Wikipedia - just type in the aircraft type you are interested in, and you will find (for most) a fairly detailed article.

Hope this helps.

[kenparry]

Further info:

The Cessna Citation series go from about 12000 lbs to around 16000 lbs, so well under your dividing size.


The Grumman Gulfstream IV, a large business jet, is shown as 73200 lbs MTOW.

Only a few airline jets, such as the Embraer noted above, are below 60000 lbs. Some turboprops bracket that size, for example the Bombardier Dash 8; the early versions were 36300 lbs, later ones 43000 lbs then 64500 lbs.

[Connetts]

Thanks, kenparry..... just what I wanted.

"Connetts"

[CR2]

B747-400ERF is 922K LBS (or was is 933K? memory fading...)

[Northbeach]

Connetts,


Perhaps it would help to think of your question in these terms. Professional boxing divides their fighters into different weight classes. This division allows for a more accurate comparison between fighters and puts them into boxing events that are appropriately matched according to power, weight and experience.

What Boeing is doing is grouping like aircraft for accurate statistical comparison that allows for meaningful analysis.

In aviation there are different maximums; maximum certified ramp weight, takeoff weight and landing weight and many others. Consequently, just because you see the word “maximum” and a number associated with it that does not necessarily mean that weight is the most the airplane can weigh under any circumstance.

Prior to permission being granted to produce and introduce aircraft into commercial passenger service engineering and actual physical performance capabilities are established by the overseeing governmental agency tasked with final certification approval of any airplane type. The aircraft must meet all of those requirements. Going back to the sports analogy; let’s say you had to compete in an Olympic decathlon. To win this event as an athlete you would have to achieve a specific level of fitness. Realistically that would necessarily limit your size and weight to being within a specific range.

So it is with these jets. They have to successfully meet or exceed numerous performance requirements stipulated by the governmental agency they are seeking the approval of. Above a certain weight, the airplane is no longer able to achieve the required performance. So a maximum weight is established.

At and below a certain limiting weight the airplane will do what it was designed to do and achieve the required goal(s) that were in place when certification was granted for this type of airplane. If the jet is heavier than that specific “maximum” weight-then the airplane is being operated outside the scope of what it was designed by the manufacturer to do, beyond what the overseeing governmental agency granted permission for it to do and will most likely not be able to achieve the specific performance requirement (it would fail that test). It becomes an illegal and unsafe operation.

Please send me a link to your article when you have finished writing it.

Respectfully,

[BelArgUSA]

Hola Connetts - or shall I say "Goeienaan" als U bent in Kaapstad...?
xxx
This may be of interest to you...
The old concept of weight (or "mass" if you are out of a physics class) was aircraft classification in the old days of aviation, and still is actually. It also imposed on commercial operators some limits as to the "size" (by weight) of aircraft they could operate.
xxx
The "small aircraft" or "light aircraft" class was considered to be airplanes below 5,700 kg of maximum takeoff weight. The number 5,700 (metric) is merely 12,500 lbs converted in kilos. Then you will ask "where is 12,500 bs coming from" - when I was a teenager, my aviation instructors told me that it was the maximum gross weight of a DC-3 Dalota "divided by 2"... I assume they then considered the DC-3 as an aviation standard.
xxx
Small airplanes (less than 5,700 kg) were then "private airplanes" often flown by "private pilots" - often VFR only, single pilot, not requiring a specific type qualification other than "single engine" or "multi-engine"... Such classification of airplanes, if operated commercially, as in "air taxi" required the pilot to hold a CPL Commercial Pilot Licence. A limitation of 19 passengers seats was also another limitation observed., such as "commuter airplanes"
xxx
The next classification were airplanes 5,700 kg to 20,000 kg. These were generally airplanes operated by "regional airlines" - a typical example were the original Fokker F-27 "Friendship", if you wonder why they had a 20,000 kg limit. Pilots had to hold a SCPL "Senior Commercial Pilot Licence" (a rare level of licence in this day and age, but still exists in some nations) to be captain and co-pilots required a CPL licence. There was a limitation of 44 seats (49 in some of my notes from long ago).
xxx
And then, we get to the heavy/large airplanes, above that class, with no upper limit of weight and passenger seats. There, the pilot must hold ATPL Airline Transport Pilot Licence to be captain, and co-pilot, depending on the national legislation, must hold a CPL (or SCPL, if applicable there).
xxx
The above are old concepts, which ICAO has now long modified, but maybe it explains some "numbers" that appear in today's legislations. I recall also that in the USA, a flight engineer was required (initially) for aircraft exceeding 80,000 lbs takeoff weight...
xxx
With your background, I thought you would like to know the above.
Best regards -
:8
Hapy contrails

[Connetts]

Goeie moré, BelArgUSA (http://www.pprune.org/members/113788-belargusa). Ek's baie dankbaar vir jou hulpsaam berig..... en ja -- ek het 'n mooi uitsig oor Tafelbaai en Tafelberg.

One problem of dealing with a Dutch speaker is that my tongue trips over my teeth/fingers thereafter when I try to speak/write Afrikaans....!

You and others -- thanks to all for your courtesy -- have set me right.

[Connetts]

Sorry..... yes, of course I'll send a copy as an attachment (there may well be no www link accessible outside an academic library and its restricted-access resources), but do realise that legal journals have strict copyright rules and the paper may not be circulated.