crazydave98 said:
Almost right. MTOW is the sum of aircraft basic operating weight (empty apart from a few odds and sodds) plus fuel plus payload. We have 180 seats in our B737-800s while Qantas have 164ish (can't recall exact number). So the situation can arise where we have a higher payload and less "room" (actually weight) for fuel, and have a higher fuel burn because of the heavier payload. Therefore less range for the same aircraft.
Sorry, I think my wording may not have been as clear as my thought process
. I was not suggesting that QF and DJ 738/73H have the same range, but that all DJ 737-800s would have the same range as each other if carrying the same same payload, and all QF 737-800s would have the same range as each other if carrying the same payload. As you have pointed out, the different configurations between QF and DJ would lead to some variations between carries. My comparison was meant to be within each operator, not between operators.
crazydave98 said:
Also, there are multiple different MTOW's available for the B737-800 (although the changes are just paper and chips as noted earlier by Standby). We have some of our 800s as High Gross Weight and some at Low Gross Weight (the leased ones that we needed to get in a hurry after Ansett fell over). The HGW are the -26 engines and the LGW have the -24 engines as NM noted, but I would be interested to know NM's source for saying that we have them registered at the same MTOWs. Obviously if a HGW aircraft is operating at close to its MTOW and has to be downgraded to a LGW, something has to give and hopefully that something won't be a few tonnes of fuel.
My source is the downloadable database from CASA or the Australian Civil Aircraft Register. I downloaded it yesterday so assume it is pretty much up to date and reflective of the actual registration details. It can be found here:
Civil aircraft register - Data files
Note that QF's fleet of HGW and LGW 73H aircraft are also all registered with the same MTOW (according to the CASA register).
Note that registered MTOW does not need to match the manufacturer's declared MTOW for the aircraft. Obviously it should not be higher, but can be lower. The aircraft cannot legally be operated above the registered MTOW. In most cases, aircraft operating fees are based on the registered MTOW of the aircraft, not the operating take-off weight, so there is a cost incentive to only register the aircraft to the lowest MTOW that is required for planned operations or you may be paying higher fees and rarely require the extra weight. The registered MTOW is noted on the aircraft registration plaque which is usually located inside the coughpit.
At least one Australian aircraft operator had a system in place where through an engineering change they could alter the registered MTOW when needed. This was doe with approval from CASA and required an engineer to replace the registration plaque inside the coughpit whenever the change was performed. This allowed the aircraft to be used for long-haul international ops where the increased weight was required, and then be "converted" for short-haul domestic ops. I am not sure how such an aircraft would show on the above mentioned Civil Aircraft Register??? I will see if I can dig out any further info on that one.
