Smaller passenger transport organizations operating aging aircraft will need to deal with aircraft aging, fatigue, and corrosion issues that have not been encountered before.
The ramifications of this change area depend on the type of operation. Aging aircraft maybe covered adequately for Part 121 commercial operations. The same aircraft certified under Part 23 (less stringent certification rules) and operated under Part 135 Commuter and On-demand Operations, may be treated differently from an aging aircraft airworthiness perspective.
Of the 205,000 fixed-wing GA aircraft currently flying in the U.S., less than 10,000 are certified under the FAA’s Part 23 rules that require a manufacturer to perform a fatigue-life analysis. More than 80% of the fleet was certified under the old CAR 3 rules that did not take metal fatigue into account. Current estimates are that 140,000 of them are more than 30 years old, and 25,000 are more than 50 years old.
One operator’s fleet has the following characteristics and some seriously high-time aircraft. They include a 20,000-hour Piper Lance, a 23,000-hour Cessna 402B, a 24,000-hour Piper Chieftain, a 27,000-hour Piper Navajo, a 30,000-hour Swearingen Merlin III, a 32,000-hour Beech 1900 and a 50,000-hour Beech 99. These aircraft have been worked hard for 20 to 30 years, sometimes more, and the only time they’re hangared is while undergoing maintenance. Prior generations of aircraft had higher safety margins designed from the beginning, allowing for longer lifespans and continued operations in situations for which there was no design requirement. The B-52 is one example of such an aircraft, and still sees use in operations today.
Examples of transport-category aircraft types operated by small organizations include: Grumman G73T, Tupolev 154 (3), Ilyushin 62M, Boeing 707, MD-11F, Embraer 110, Antonov AN28 (2), Dornier 228, Let410 (5), Tupolev 134 A, Ilyushin 76TD (5), Boeing 727 (3), Boeing 737-200, Yakovlev 42D, Beech 1900 D, Dash-8-100, Convair CV 340, Swearingen SA-227 Metro (3), Saab 340, Antonov AN24 (3), Antonov 12 (2), Casa/Nurtanio NC-2, Curtiss C46, and Antonov 26.
- Uncertainty about the quantity or type of maintenance and inspection required to ensure a high level of safety
- Structural failure due to fatigue cracking and corrosion
- The biggest impediments to keeping vintage aircraft safe are the unavailability of parts and approved data, together with the near impossibility of getting field approvals for substitution of modern parts and materials. These problems are most acute with “orphaned aircraft” whose type certificate holder has either disappeared or decided not to support the aircraft with parts and data.
This issue is not to be underestimated because FAST found in their 2015 analysis of ten years of accidents 42 cases which related to this AoC. It involved (numbers between brackets are number of cases) Grumman G73T, Tupolev 154 (3), Ilyushin 62M, Boeing 707, MD-11F, Embraer 110, Antonov AN28 (2), Dornier 228, Let410 (5), Tupolev 134 A, Ilyushin 76TD (5), Boeing 727 (3), Boeing 737-200, Yakovlev 42D, Beech 1900 D, Dash-8-100, Convair CV 340, Swearingen SA-227 Metro (3), Saab 340, Antonov AN24 (3), Antonov 12 (2), Casa/Nurtanio NC-2, Curtiss C46 and an Antonov 26. These are predominantly out of production aircraft.