53 Fuselage

TTP	B1-L3	ATA 53
Beech 90 Series	B2-L1	Fuselage

 

The  King Air  C90A/B/GT/GTi  fuselage  is  of semimonocoque construction and is fabricated from formers, frames, bulkheads, and keels reinforced by longerons and stringers. The structure is enclosed by a skin formed from high strength aluminum alloys.

 

The fuselage is pressurized to the skin between the  pressure  bulkheads  at  FS  84.00 and FS 298.00. To minimize loss of pressurization, all skins, doors, windows, and structural joints are thoroughly sealed. The control cables, O/B torque shafts, and plumbing and wiring connections that pass through pressure walls are installed with fit- ted seals or plug connectors to minimize leakage.

 

 

DYNAMIC VIBRATION ABSORBERS

 

C90B aircraft have dynamic vibration absorbers in the flight compartment and forward cabin area to reduce vibration and sound. Twenty-six absorbers are in pairs along each side of the fuselage. The absorbers are on the aircraft frame  and  consist  of  spacers,  clips,  weights, and leaf springs. The weights are secured to the leaf springs with bolts, washers, and nuts; the leaf springs are secured to the clips with bolts, washers, and nuts. At the time  of installation, each absorber is tuned to a frequency of 126.7 Hz. This frequency is determined by the specific propeller speed (1,900 rpm) at which a vibration or noise exists. 

This number is determined by the following formula: 

PROPELLER RPM MULTIPLIED BY 4 BLADES AND DIVIDED BY 60 SECONDS (e.g., 1,900 (rpm) times 4 (propeller blades) = 7,600 divided by 60 (seconds) = 126.7 Hz).

 

The absorbers are tuned to a specific frequency and marked with torque paint so no adjustment, disassembly, or relocation should be attempted. If removal becomes necessary, the absorber must be removed as an intact unit and reinstalled exactly as it was removed. Ensure the absorbers do not contact any insulation, wiring, or other objects after installation.

FUSELAGE INSPECTION

It is requested that Hawker Beechcraft Aircraft Company be notified of any indications of structural

fatigue and that the total aircraft time be included when such indications occurred. Please forward

this information to Hawker Beechcraft Technical Support, Hawker Beechcraft Aircraft Company, Wichita, Kansas 67201. 

NOTE : Aircraft which have exceeded the initial  inspection  cycle are permitted a tolerance of 600 cycles or one year (whichever occurs first) from the date of this revision to comply with the initial fuselage inspection.

Inspect the following areas of the fuselage to ensure the structural integrity of the component parts. Should damage or corrosion be detected in any structural component during this inspection, all adjacent  structures must be examined for indications of related damage or corrosion. All damage and corrosion must be repaired or replaced. Should there be a noticeable decrease in  the  efficiency of  the  pressure  vessel,  these additional inspections should be made. Remove access plates, upholstery panels, and floorboards as necessary to permit a careful visual inspection of the skin and underlying structure in the areas noted in the following procedure.

NOTE : Do not permanently remove any of the upholstery support strips riveted to the bulkheads or basic airframe structure.

 

Flight Crew Compartment Area Inspection

 

1.   Inspect the fuselage for damage and loose rivets at points of juncture with the instrument panel support brackets.

 

2.   Inspect  the  flanges  of  the  bulkheads  and frames for damage or loose rivets near the instrument panel substructure.

 

3.   Check the intercostal area FS 107–FS 125 for cracks and sheared or stretched rivets.

 

4.   Inspect for loose rivets and cracks or other structural damage in the bulkheads and longerons that intersect under the finger doublers and gussets at the upper and lower corners of the storm windows on each side of the crew compartment.

Fuselage Floor Line Inspection

 

1.   Carefully inspect the floor line of the pressure vessel at all points of juncture with the adjacent support structure for cracks and for loose rivets or fasteners.

 

2.   Check all bulkhead flanges and web lightening holes for cracks or other damage in the area near points of intersection with the floor line of the fuselage.

 

3.   Inspect for cracks and loose rivets in splice plates, support doublers, stringers, clips, and angles adjacent to, or tying into, the floor and its substructure throughout the length of the pressure vessel.

 

4.   Check  the  floor-rail  support  structure,  the floor support channels, and the stringer ties to the floorboards for damage and sheared, loose, or stretched rivets.

Forward Pressure Bulkhead Inspection

 

1.  Inspect the rivet pattern for indications of sheared or loose rivets on each side of the forward pressure bulkhead at FS 84.

 

2.   Check for cracks in the skin or supporting structure emanating from the attaching rivets.

 

3.   Inspect the bulkhead web and stiffener flanges for cracks or other structural damage.

 

AFT Pressure Bulkhead Inspection

NOTE: Scotch® foam is a white insulation material with a foil facing and a self- adhesive backing used as a sound deadener.

Do not reapply Scotch® foam to any surface of the vessel after it has been removed. It can retain moisture which may initiate corrosion.

 

1.   Carefully  inspect  all  Scotch® foam panels on both sides of the aft pressure bulkhead for indications of separation from the skin or for white powdery residue around the perimeter.

 

2.   If signs of separation or residue are detected, remove the individual Scotch® foam panel using a plastic scraper and methyl propyl ketone  (MPK). After  removing  a  Scotch® foam panel, carefully inspect for loose primer, corrosion, and structural damage.

 

3.   Inspect the webs and their supporting stiffeners, clips, angles, and plates for cracks and loose rivets.

 

4.   Check the bulkhead flanges and the stringers at the cutouts in the bulkhead flanges for cracks and loose rivets.

5.   Check the mounting brackets for the oxygen bottle and the box for the outflow and safety valves for cracks and loose rivets at their points of attachment to the pressure bulkhead.

 

6.   Inspect the area adjacent to the relief tube for corrosion where it feeds through the fitting.

NOTE: The stringers are numbered consecutively down each side of the fuselage from the first stringer to the right to left of the centerline at the top of the fuselage.

Escape Hatch Area Inspection

 

1.   Inspect the escape hatch frame assembly and the fuselage frame encompassing it for cracks or other indications of structural damage. Inspect the hinge, hinge plate, latch pins, and the longeron below the hinge plate for corrosion.

 

2.   Check bulkheads, longerons, doublers, clips, straps, angles, and other structural members adjacent to the escape hatch for damage and loose rivets.

 

Cabin Door Area Inspection

 

1.   Inspect the cabin door, the doorframe, and the nearby supporting members for evidence of damage.

 

2.   Check the hook catch plate and the stringer adjacent to it immediately above the doorway for cracks or other signs of damage.

 

3.   Check all door hooks, latch bolts, and their striker plates in the doorframe for indications of damage.

 

4.   Inspect the bulkhead, bulkhead flanges, support doublers, stringers, clips, and angles adjacent to the doorframe for cracked or loose rivets.

Fuselage Area Inspection

1.   Inspect all frames for cracks or other indications of structural damage.

 

2.   Check bulkheads, longerons, doublers, clips, straps, angles, and other structural members adjacent to the frames for damage and loose rivets.

NOTE: The  following  steps  are  performed from the exterior of the fuselage and the flaps fully extended to gain access to the fuselage-to-wing cover.

3.   Drill off four rivets on each of the right and left lower aft fuselage-to-wing covers attached to the fillet assembly.

4.   With a flashlight, carefully inspect this area for looseness of the Scotch® foam or for white powdery residue.

5.   If either condition is suspected, remove the individual Scotch® foam panel using a plastic scraper and MPK. After removing a Scotch® foam panel, carefully inspect for loose primer, corrosion, and structural damage
6.   Reattach both lower fuselage-to-wing covers with blind rivets.

AFT Fuselage Moisture Drainage System Inspection

 

1.   Visually ensure that all drain holes in the ventral fin are clear of debris.

 

2.   Open the aft fuselage door.

 

3.   Ensure  that  the  0.19-inch  diameter  drain holes in the four stringers just aft of the rear pressure bulkhead are clear of debris. One stringer is to the right of the centerline and the other three stringers are to the left of the centerline.

 

4.  At the aircraft lower centerline, locate the channel that parallels the access door. Visually inspect the drain hole at the lower forward end of the channel. Ensure that it is 0.50 inch in diameter and is clear of debris. Ensure the KEEP DRAIN HOLE OPEN decal is on the channel.

 

5.   Close the aft fuselage access door.

PTP  Beech 90 Series	B1	LOC					TS
	B2