Block foam method of accomplishing ignition mitigation in aircraft fuel tanks

In an aircraft equipped with at least one fuel tank consisting of multiple compartments, each compartment having interior surfaces contoured for the accommodation of compartment structural members, and equipment a method for providing fuel ignition mitigation within each individual compartment, comprising the steps of:

• a) determining dimensions, contour, and precise location of structural members for each compartment as encountered at sequentially-measured linear increments along either width or length dimension of the compartment interior;
• b) rendering a scaled engineering drawing of a vertically-oriented cross-sectional profile at each measured linear increment in each compartment;
• c) numerically sequencing each drawing corresponding to a respective drawing location along the measured linear increment within its respective compartment;
• d) providing a plurality of planar sheets of reticulated polyurethane foam (RPF) material, said RPF material comprising a thickness in-dependent upon size and type of aircraft fuel tank;
• e) excising an aggregate of cutouts of RPF blocks from said planar sheets of RPF, each cutout conforming to each of the scaled engineering drawings for each particular compartment, and further, designating each RPF block by a part number, an orientating “UP” arrow, and an orientating “FORWARD” arrow;
• f) for each compartment, arranging the aggregate of said RPF blocks in a progressive sequence corresponding to the sequence of the cutout part number of each RPF block;
• g) for each compartment, sequentially packaging said aggregate of RPF blocks into groupings containing a specified number of RPF blocks per grouping;
• h) composing instructions for each compartment, to be used by technicians and/or installers for the purpose of inserting the RPF blocks into the compartment;
• i) parking the aircraft on a level surface and emptying and purging all compartments of the fuel tank;
• j) commencing installation in a selected compartment by removing a fuel tank access panel or other external tank cover which i) functions as an opening for entry of maintenance personnel and/or technicians into the compartment, and ii) is proximate the selected compartment;
• k) inspecting the interior surfaces of the selected compartment to ensure cleanliness and accessibility by the installers;
• l) placing the first sequential RPF block at a specified location within the selected compartment as so designated in the instructions;
• m) placing each successively-ordered RPF block at its designated location within the compartment as set forth in the instructions, until the compartment is filled in accordance with the instructions;
• n) for each remaining compartment of the fuel tank, performing steps j) through m), above;
• o) performing an inspection of the installed RPF blocks, and afterwards, closing all open compartment or fuel tank access panels;
• p) re-fueling all compartments of the fuel tank and verifying the fuel tank's maximum fuel quantity in accordance with FAA-certified fuel gauge calibrating procedures for the subject aircraft.

A method for providing fuel ignition mitigation for the interior of the center wing tank of an aircraft of the type having a center wing tank consisting of a forward, center, and aft compartment, in which each compartment manifests interior surfaces contoured for the accommodation of compartment structural members and equipment, said method comprising the steps of:

• a) determining dimensions, contour, and precise location of structural members for each of the compartments as encountered at sequentially-measured linear increments along either width or length dimension of the interior of each compartment;
• b) rendering scaled engineering drawing of a vertically-oriented cross-sectional profile of each of the forward, center, and aft compartments at each measured linear increment;
• c) numerically sequencing each drawing corresponding to a respective drawing location along the measured linear increments within the respective forward, center and aft compartment;
• d) providing a plurality of planar sheets of reticulated polyurethane foam (RPF) material, said sheets of RPF comprising a thickness dependent upon size and type of aircraft fuel tank;
• e) excising an aggregate of cutouts of RPF blocks from said planar sheets of RPF, each block cutout conforming to the scaled engineering drawing for each particular compartment, and further, designating each RPF block by a part number, an orientating “UP” arrow and an orientating “FORWARD” arrow;
• f) arranging the aggregate of said RPF blocks in a progressive sequence corresponding to the sequence of each RPF cutout part number for each of the forward, center, and aft compartments;
• g) for each compartment, sequentially packaging an aggregate of RPF blocks into groupings containing a specified number of RPF blocks per grouping;
• h) composing instructions for each compartment to be used by technicians/installers for the purpose of inserting and installing said RPF blocks into each compartment;
• i) parking the aircraft on a level surface, and emptying and purging all compartments of the center wing tank;
• j) beginning with the aft compartment, removing a tank access panel or other external tank cover which i) functions as an opening for entry of maintenance personnel and/or technicians into the aft compartment, and ii) is proximate the aft compartment;
• k) inspecting the interior surfaces of the aft compartment to ensure cleanliness and accessibility by persons;
• l) placing the first sequential RPF block at a specified location within the aft compartment, as so designated in the instructions;
• m) placing each successively-ordered RPF block at its designated location within the aft compartment as set forth in the installation instructions, until said aft compartment is filled in accordance with the previously determined aggregate of RPF blocks;
• n) performing an inspection of the installed RPF blocks in the aft compartment, then closing any previously opened tank/compartment access panels,
• o) placing successively-ordered RPF blocks at their designated locations within the center compartment as set forth in steps j) through n), above until said center compartment is filled with the required aggregate of RPF blocks;
• p) placing successively-ordered RPF block at their designated locations within the forward compartment as set forth in steps j) through n) above, until said forward compartment is filled with the required aggregate of RPF blocks;
• and
• q) re-fueling all compartments of the center wing tank and verifying the tank's maximum fuel quantity in accordance with FAA-certified fuel gauge calibrating procedures for the aircraft.