Yet ask five line mechanics for anecdotes about their work and one will probably reveal not everything is done by the book.
The lightly overseen area of engine test runs (on aircraft) is one concern, as demonstrated in 2007 when an Etihad A340 was written off even before it had left the tarmac of its Toulouse production site.
Investigators blamed the accident on a deviation from manufacturer-approved procedures – a failure still all too common across airlines and lessors, argues Mark Goodrich, senior status consultant with Aviation Consulting Enterprises.
“Often, neither the pilot's operating data nor the maintenance and inspection manuals for an airline are updated to stay abreast of new operating procedures,” writes Goodrich in the forthcoming Engine Yearbook 2016.
During his time as an engineering test pilot and inspector, Goodrich identified a couple of recurring issues: cursory training for engine test crews; and the application of start and run-up procedures specific to one engine type to many other models.
Aircraft test crews also need to be properly trained. In 2008 an A320 performing a lease return test flight crashed, killing all on board, after an air crew with minimal test flight training encountered problems during low-speed, low-altitude manoeuvers.
“Had the aircraft been operated by an engineering test crew, such manoeuvers would not have been undertaken at low altitude,” says Goodrich.
Such incidents have thankfully forced operators to broaden flight crew training in recent years, though Goodrich argues that the operations of modern, computerised engines remain poorly understood by many air and ground crew.
Too often, he says, monitoring is delegated to the engine’s computers, but without an associated understanding of how those automated sensors work.
Subscribe to the next edition of the The Engine Yearbook to read Goodrich’s full account of the shortcuts that are sometimes taken.