7
$\begingroup$

According to the FAA's definitions in 14 CFR 1.1, a Large aircraft is an "aircraft of more than 12,500 pounds, maximum certificated takeoff weight." I have heard this threshold was set based on the DC-3, but that makes no sense to me. Also, there doesn't seem to be any common-sense/international connection to kilograms (i.e. 12,500 pounds is roughly 5670 kg, not a nicely rounded-off 5700 kg).

What is the origin of 12,500 pounds being the cutoff between Large and Small aircraft?

$\endgroup$
  • 1
    $\begingroup$ Well, you can't have number that's round in both pounds and kilograms and FAA works in pounds. Regarding Dc-3, it does not make sense to me either, because it's MTOW is a bit over twice as much (25,199 lbs). $\endgroup$ – Jan Hudec Oct 28 '18 at 19:25
  • 1
    $\begingroup$ Sorry, bringing pounds vs. kg into the question was only to suggest that the requirement doesn't seem to be based on any international standard. I flew a PC-12 for about a year and know their books/specs are metric-based and have been converted to US standards. $\endgroup$ – user16289 Oct 29 '18 at 0:17
  • $\begingroup$ There is nothing to be sorry about. It was just a bit unclear why you brought it up, and now you explained it. $\endgroup$ – Jan Hudec Oct 29 '18 at 7:58
  • $\begingroup$ Actually, 12,500 pounds converts nicely to 6.25 US tons (2,000 pounds to a ton). $\endgroup$ – Juan Jimenez Nov 8 '18 at 21:21
1
$\begingroup$

If you take a look at FAA FAR 14 CFR 23.3 - Airplane categories. you can see the amendment history linked at the bottom. This will take you through a series of changes made to the regulation as well as to the creation of part 23 in 1964 and some provide some background/history for some of the changes. It looks like in 1964 the 12,500 LB limit was not part of Part 23. It was likely included elsewhere so I cant yet trace this full history. However in the amendments that appeared as part of Federal Register: 52 Fed. Reg. 1619 (Jan. 15, 1987). (Page 1806) they go into some specifics and it appears that the weight was chosen as it was somewhere in the middle of the over all range.

Since 1953 the airworthiness standards have distinguished small from large airplanes by a 12,500 pound maximum certificated takeoff weight -(MCTW) limitation regardless of the type of operation. When this weight limitation was established, little concern was expressed that this demarcation would eventually become questionable with regard to airworthiness standards for an airplane of the commuter category. At that time, there were few airplane designs near this 12,500 pound limitation; i.e., they were either considerably above or below that weight.

Effectively at the time (1953) all "small" planes were well below that and all "big" planes well above that. Unfortunately this does not shed any light on your DC-3 note.

$\endgroup$
-1
$\begingroup$

The DC3 was the backbone of reliable air transportation and way ahead of its time....the wonder metal Aluminium. Deice. Autopilot. Two pilots flight crew. Hostess. Blind flying equipment. Comfortable. Reliable.

It set the standard in many areas...I read somewhere that the rudder force limit OEI of 180 lbs is derived from the DC3. Likewise, the Gulfstream 1 cabin crossection was chosen to be same as the DC3, (I guess because it worked - it was comfortable and looked right) and this carried through to the G2 and many corporate jets.

A light aircraft was considered to be less than half the weight of a DC3 - I was told this many years ago. Can't give a reference, can't confirm if it's true or not. It's just one of those aviation things, maybe even common sense?

$\endgroup$
  • $\begingroup$ Welcome to Aviation Stack Exchange. Your answer sounds like it could be true, except that you haven't provided any actual references for your assertions. This site is not a forum, but rather a question and answer site with hard verifiable references being the standard for correct answers and upvotes. Your knowledge and experience are valued here, but as written, your answer would better fit as a comment to the original post. $\endgroup$ – PJNoes Nov 27 '18 at 18:07

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.