Originally Posted by
V1... Ooops
No, the supplement does not "approve" operations above the certified MTOW of 12,500 pounds. The supplement provides performance data for overweight operations, but it is always the responsibility (and legal obligation) of the operator to obtain written approval for any overweight operations from the appropriate regulatory authority (or authorities, if the flight is international) before conducting such a flight.
How do I know this for sure? Because I wrote the AFM and the supplements for the DHC-6 Series 300 and 400. FWIW, I also delivered that aircraft from the factory to the operator when it was new.
As noted above, there is no factory certification of any kind for overweight operations. The manufacturer provides performance information to enable planning for ferry flights. It is the responsibility of the operator to obtain regulatory approval for each and every overweight flight.
A CVR is standard equipment on Series 400 Twin Otters, every one that ever left the factory was equipped with both a CVR and a FDR.
The main fuel tanks of the Twin Otter are located in the fuselage, below the cabin floor. Optional wing tanks are located at the end of each wing.
The change in CG between full fuel (with or without wing tanks) and empty fuel is negligible and normally does not need to be considered as long as the fuel load was equal (front/rear) to begin with, and fuel is consumed equally from each tank.
I appreciate your knowledge of the Twin Otter in this discussion.
In my comment, I was assuming the Twin Otter had ferry fuel bladders in order to have the fuel needed to cover the 2000+ nm flight to Honolulu. The fuel bladders were, presumably, on the floor of the aircraft, and probably extended to the rear of the cabin. If that is true, then as the fuel in the main tanks was consumed the CG would have moved aft.
As others have said, the flight to/from Hawaii from the west coast of the US is the longest over water distance without an alternate on the planet. I have made that crossing 3 times, the last one solo in a light twin.
Thanks for your comment.