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September 09, 2020

During an aircraft's service life, rare events and circumstances may arise when something out of the ordinary could perhaps influence the airplane's airworthiness.

When such occasions occur, special and unique inspection methods, also known as conditional inspections, are done to figure out if any damage to the aircraft structure has happened. The inspection methods are general and are meant to inform and familiarize the aviation technician about the affected areas. It is important to note that the procedures are not all-inclusive.

When doing any of these inspections, the aviation mechanic should always follow detailed procedures mentioned in the aircraft maintenance manual. In situations where the manual does not address a problem, advice must be taken from highly experienced aviation welders and technicians. Below we describe some of the most common types of special/conditional inspections.

Hard or Overweight Landing Inspection

The structural stress caused by a landing depends not only upon the total weight of the airplane at the time but also upon the amount of force with which it hit the ground.

The hard landing inspection is done when hard landing takes place at or below the maximum design landing limits. An overweight landing inspection is done when an aircraft lands at a weight beyond the maximum landing weight limit. However, due to the difficulty in determining vertical velocity at the time of contact, it is hard to decide whether a landing was severe enough to cause any structural damage. For this reason, special inspection is performed after a landing is made at a weight greater than the design landing weight limit or after a rough landing.

Possible damage detected after the above two conditions are wrinkled wing skin or fuel leakage along riveted seams.

Other possible damage locations are spar webs, bulkheads, nacelle attachments, firewall skin, and wing and fuselage stringers. If none of these regions show adverse effects, it is okay to assume that no severe damage has happened. If the damage is identified, a more thorough and detailed inspection becomes necessary.

Severe Turbulence Inspection

When an airplane faces a gust or a storm, the air load on the wings surpasses the standard wing load carrying the aircraft's weight. This leads to a situation where the wind tends to accelerate the aircraft while its inertia tries to resist this change. If the airspeed becomes too severe, the induced stress will cause structural damage.

In this case of severe turbulence, special inspection is performed right after the plane's landing. Emphasis is given to inspecting the upper and lower wings for excessive buckles or wrinkles. Where wrinkles have appeared, remove a few rivets and check the rivet shanks to see if they have experienced any damage.

Bird Strike Inspection

Bird strike is strictly defined as a collision between a bird or a flock of birds and an aircraft. It is a common incident and can cause a significant threat to the plane. Many a time, commercial jets have made emergency landings due to suspected bird strikes.

When such an eventuality occurs, the airplane's external areas are inspected where the bird struck. If the initial inspection shows structural damage, then the airplane's internal structure must be examined as well. Hydraulic, pneumatic, and other systems in the area of the bird strike should also be inspected.

These are the three most common events that can initiate condition inspection. These inspections should be performed by any licensed A&P mechanic or a TCCA approved aviation welder like Acorn Welding.

About Acorn Welding

Acorn Welding is an expert aircraft parts manufacturer and maintenance provider based in Edmonton, Canada. Visit our website to learn about our welding services or contact us for personalized assistance.