View Full Version : Definitions for ZFW, ETW, Basic Weight, etc

Jumbo Driver
29th Aug 2007, 12:13
Can someone please point me in the direction of a source for the definitions of such terms as APS Weight, ZFW, ETW, Basic Weight, Dry Operating Weight, and the like?

I expect some will prove to be synonymous but I would like to refresh my memory on the more subtle differences between the others.

My grateful thanks, in anticipation ...


Flip Flop Flyer
29th Aug 2007, 12:32
APS and Basic Weight (BW) is the same and constitutes an empty aircraft + non-useable fuel, oil, equipment (e.g. gally ovens) and documentation.

DOW = BW + the operating crew and their bagage

ZFW = DOW + payload

ETW: Haven't a clue, never heard of that one before.

29th Aug 2007, 12:42
ETW - Estimated take off weight, for planning purposes.

try www.pilotfriend.com (http://www.pilotfriend.com) and the weight and balance section.

High Wing Drifter
29th Aug 2007, 12:48
The definition of ZFW that I was given during the ATPL theory course, was that for some aircraft it includes fuel in the centre tank :\ Now I know there are some issues with some 737 models in this regard, does this definition of ZFW exist for any other aircraft?

29th Aug 2007, 13:22
Some early versions of the Learjets 20 series had a Max ZFW that included any fuel located in fuselage tank. This is called "wing bending weight"...
Happy contrails

Jumbo Driver
29th Aug 2007, 13:24
ETW: Haven't a clue, never heard of that one before.

FFF, ETW = Empty Tank Weight ...


29th Aug 2007, 13:58
Doesn't DOW add to confusion and is it not just best to use ZFW as it already includes the crew aswell?

Flip Flop Flyer
29th Aug 2007, 14:10

Not for Weight & Balance purposes, as the DOW is associated with DOI. DOI will always be the same for a given aircraft, but LIZFW (Loaded Index at ZFW) will differ depending on how the aircraft's been loaded.

Hence, you'll start with DOW and DOI, then add the weight of the payload to get ZFW (if, indeed, the flight is carrying payload which is not always the case).

For aircraft which requires ballast fuel in order to trim without payload (for instance MD11 or B727), the ZFW will include the ballast fuel.

So is ETW = Empty Tank Weight (and thus the same as ZFW?) or Estimated Take-off Weight, and if it's the latter shouldn't it then be ETOW?

Jumbo Driver
29th Aug 2007, 16:54
Yes, FFF, I would also expect ETW (Empty Tank Weight) to be the same as ZFW.

However, the point of posting this thread was to seek the definitive source - maybe ICAO/IATA or CAA or such - for these terms. It's the source of the definitions I am after - much as I appreciate everyone chipping in with their two penn'orth ... :ok:


29th Aug 2007, 17:10
My bad. Would help if I read the post correctly, seen ETW but forgot about the 'O' in the middle. Sorry.

30th Aug 2007, 00:43
Main thing is to realise that some of the "definitions" are rubbery and may vary across the Industry. Important point is to check the definitions so that you know what the presumptions are when you use the number.