One of personal aviation’s historic Achille’s heels has been vacuum-driven flight instruments. Mechanical versions of the artificial horizon or directional gyro slowly are being replaced with more-reliable electronic implementations, but there’s still a bunch of aircraft flying around with what is a quaint technology: vacuum-driven instruments. And the record is littered with examples in which a failed vacuum system or related instrument led to a fatal accident.
Until the 1990s, when backup options became widely available for personal aircraft, a vacuum system failure in instrument conditions was an extreme emergency. These days it still is, but electric backup instruments are relatively inexpensive and easy to install.
