Any highly qualified/current Microsoft Airlines veteran 747 captain here...?
Come on, please help. You gentlemen do know better -
xxx
Everyone knows that there are 3 reasons - (sometimes more) -
One "klonk" for the
doors closing.
Another "klonk" when wing gear (outer gear)
tilts up for retraction positioning.
And one other "klonk" for the gear full down or up (extension/retraction).
That is for the 100-200-300-SPs...
In the 400s, the "klonks" sound more like "bang-boom" -
At least if you sit on seats 45A or 45K.
My FOM indicates that the sounds are within Annex 16/3 noise limits.
xxx
And extra "klonks" if I let that darn F/O land (he logs 2 or more landings)...
Happy contrails