Minimum Equipment

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.

Joseph E. (Jeb) Burnside

Wednesday, February 17, 2016 at 12:00 AM ET

Verified

Al Dyczek will fly the Iowa City to Omaha leg of the Airmail100 relay flight in his Bonanza. AirMail100 Project

Key Takeaways:

Vacuum-driven flight instruments are a historic safety weakness in personal aviation, prone to undetected failures that can lead to inaccurate attitude information, spatial disorientation, and fatal accidents, especially in Instrument Flight Rules (IFR) conditions.
A fatal Piper Seminole accident occurred when its *only operating* vacuum pump failed in-flight during an IFR flight, despite one of its two pumps already being known to be inoperative and placarded.
The NTSB concluded the accident was caused by the loss of attitude information and subsequent spatial disorientation of the minimally IFR-experienced pilots, compounded by the operator's decision to dispatch the aircraft into IFR conditions with a known, critical mechanical deficiency.

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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.