A few thoughts ..
Flight has to be discontinued and a land back is required at the departure aerodrome. Reason for land back is Depressurization. However no emergency
Then one would suggest that the land back is desired, rather than required, and one would be looking to observe all regulatory requirements as part of one’s decision process. One needs to keep in mind that the MLW is a Type Certificate limitation and, as such, is an underpinning factor in the aircraft’s design airworthiness.
Landing over gross for convenience would be a bit like trying to explain to the nice policeman that you were doing 110km/hr just before he pulled you up ... because the speed limit changed in the next few km, anyway, and you were saving the company some travelling time .... I have discovered, in my occasional discussions with the good constabulary folk, that that sort of argument has never worked really well ...
A) Make a heavy weight ... landing.. Intention is to save fuel and 2 hours holding time.
Hard to argue when the Regulator seeks to revoke your licence ?
B) Hold for 2 hours and reduce the A/C weight .. Intention is to enhance safety.
A good call, I suggest.
C) Some other better course of action
B) is a conservative strategy and you could quite easily plan with a bit more finesse to land pretty well right on MLW.
The aircraft is designed to land at MTOW
Irrelevant if the AFM limit is MLW and MLW is less than MTOW
I would land - 7000kg of fuel and 2 hours flying time is a lot of money.
Fine, but would you not then chose to engineer an emergency situation for the record ?
The 1.67 only applies to the planning-stage
I suggest not, unless you have an emergency and chose to invoke the emergency powers of the commander .. and, even then, you may need a good story for the investigation ...
The answer to your scenario is: 'It depends..........'
exactly
Inter-polate between the two examples above and you will have your answer.
Distances will be related to a quadratic sort of relationship rather than linear so a simple interpolation needs to be approached with some care.
So a "perfectly fine" aircraft (short of a cabin fire), but the company wanted us to return to Perth were we had engineering ... hold over the water
The commander gets paid to think on his/her feet. Some discussion with ops/eng and a sensible decision is the result.
the passengers became increasingly nervous about the vibration ... and we nearly ended up with a riot
Sandgropers .. what did you expect ?
The extra weight is taken into consideration in the landing calculations
Run that one past us again ? The landing calcs are for the declared weight .. if there is some “extra” weight involved, then the calcs change accordingly.
the 1.67 factor is to allow for ..
The raw FT data should be viewed as being unachievable. Even the TP couldn’t do it every time. What may end up as the base, unfactored, data in the AFM may have a little bit of negotiated fat but still represents a routinely unachievable brick wall.
Whatever regulatory factor (generally 1.67) is applied covers all those other reasonably expected things which might cause a problem and seeks to achieve the relevant failure rate which is built into the certification process.
Boeing data usually doesn’t include the 1000ft+ from threshold to touchdown
Can you cite any objective evidence to support this claim ?
So if the runway is dry, is it still worth it to waste 7000 Kg of fuel and 2 hours operational cost?
You don’t have the option. If the situation is not an emergency then the normal operational/certification standards must apply.
let them consider the implications (cost) of an overweight landing
And what are your considerations regarding the implications of the regulator’s seeking to revoke your licence ?
Why is a 1.67 factor used in the first place?
Unfortunately I don’t have sufficient information to comment with any authority on the specific factor.
However, in the olden days, the early regulators had to come up with a range of arbitrary “seems a good idea” figures to start the process going. These were then varied, as necessary, on the basis of historical accident data.
So, for instance, the 70 mph single stall speed was a FITWWAG which still is enshrined in FARs as 61 kts ... the 50 ft approach height clearance likewise came from the trees around a military parade ground ...
One would need to dig into the ancient archives to follow the history through to determine the origin and sequence for the present factor presuming that were possible .. but, I suggest, it will have followed the basic philosophy described above.
Always consider whether a lawyer could make mince meat of you if an incident were to happen on that landing.
Whatever story you come up with after the event, the legal system is going to endeavour to hang you out to dry and go for both the jugular and the deepest pockets.
Every time you take it upon yourself to be innovative, you stick your neck on the figurative chopping block ... I am convinced that all pilots, maintainers and engineers should review, if not be involved in, significant legal actions following serious or fatal accidents ... very sobering. So far I have thwarted attempts to sue proceeding beyond lodging a defence .. all due to a conservative approach to the way I do business.
Although not of direct relevance to this thread and I have no knowledge of the specifics, the
following thread and a
related one hark back to a recent Australian damages case which, I suggest, is of relevance to this thread ..
Consider a hindsight view and turn it into foresight.
Succinct.