"Aircraft logs" as used in this handbook is an inclusive term which applies to the aircraft logbook and all supplemental records concerned with the aircraft. The logs and records provide a history of maintenance and operation, control of maintenance schedules, and data for time replacements of components or accessories.
The aircraft logbook is the record in which all data concerning the aircraft is recorded. Information gathered in this log is used to determine the aircraft condition, date of inspections, time on airframe and engines. It reflects a history of all significant events occurring to the aircraft, its components, and accessories, and provides a place for indicating compliance with FAA Airworthiness Directives or manufacturers' service bulletins.
During the service life of an aircraft, occasions may arise when landings are made in an overweight condition or part of a flight must be made through severe turbulence. Rough landings are also experienced for a number of reasons.
When these situations are encountered, special inspection procedures should be followed to determine if any damage to the aircraft structure has occurred. The procedures outlined on the following pages are general in nature and are intended to acquaint the aviation mechanic with the areas which should be inspected. As such, they are not all inclusive. When performing any one of these special inspections, always follow the detailed procedures in the aircraft maintenance manual.
Hard or Overweight Landing Inspection
The structural stress induced by a landing depends not only upon the gross weight at the time but also upon the severity of impact. However, because of the difficulty in estimating vertical velocity at the time of contact, it is hard to judge whether or not a landing has been sufficiently severe to cause structural damage. For this reason, a special inspection should be performed after a landing is made at a weight known to exceed the design landing weight or after a rough landing, even though the latter may have occurred when the aircraft did not exceed the design landing weight.
Wrinkled wing skin is the most easily detected sign of an excessive
load having been imposed during a landing. Another indication which can
be detected easily is fuel leaks along riveted seams. Other possible locations
of damage are spar webs, bulkheads, nacelle skin and attachments, firewall
skin, and wing and fuselage stringers. If none of these areas show adverse
effects, it is reasonable to assume that no serious damage has occurred.
If damage is detected, a more extensive inspection and alignment check
may be necessary.
Severe Turbulence Inspection
When an aircraft encounters a gust condition, the airload on the wings exceeds the normal wingload supporting the aircraft weight. The gust tends to accelerate the aircraft while its inertia acts to resist this change. If the combination of gust velocity and airspeed is too severe, the induced stress can cause structural damage.
A special inspection should be performed after a flight through severe turbulence. Emphasis should be placed upon inspecting the upper and lower wing surfaces for excessive buckles or wrinkles with permanent set. Where wrinkles have occurred, remove a few rivets and examine the rivet shanks to determine if the rivets have sheared or were highly loaded in shear.
Inspect all spar webs from the fuselage to the tip, through the inspection doors and other accessible openings. Check for buckling, wrinkles, and sheared attachments. Inspect for buckling in the area around the nacelles and in the nacelle skin, particularly at the wing leading edge.
Check for fuel leaks. Any sizeable fuel leak is an indication that an area may have received overloads which have broken the sealant and opened the seams.
If the landing gear was lowered during a period of severe turbulence, inspect the surrounding surfaces carefully for loose rivets, cracks, or buckling. The interior of the wheel well may give further indications of excessive gust conditions. Inspect the top and bottom fuselage skin. An excessive bending moment may have left wrinkles of a diagonal nature in these areas.
Inspect the surface of the empennage for wrinkles, buckling, or sheared attachments. Also, inspect the area of attachment of the empennage to the fuselage. The above inspections cover the critical areas. If excessive damage is noted in any of the areas mentioned, the inspection should be continued until all damage is detected.