Move up from most training airplanes into high performance aircraft and you’ll confront a number of new gauges and devices. One of these, so very basic yet commonly misunderstood, is the manifold pressure gauge. Let’s look at what the manifold pressure tells us—and what it doesn’t.

The engine failure didn’t happen suddenly.... I was flying a Mooney M20C in clear, cool air, 7500 feet above the Kansas/Oklahoma border.  I’d flown the 1962 speedster from Augusta, Kansas (just easy of Wichita) to Oklahoma City, picked up a passenger and flew to a meeting in southeast Oklahoma, and was now, on the solo leg of my trip homeward.  My first clue of impending trouble, however, appeared much earlier that day.

Recently we looked at engine-failure case studies of aircraft that are close to identical in design and performance -- except for the number of engines.  We discovered that significant, regular pilot training is needed to enjoy the safety advantage of a second engine.  Translation: For many pilots (those with 'twin' ratings, included) the single-engine airplane may actually be the safer machine.  And yet, regardless the number of engines, there's still that pesky engine failure scenario, especially hazardous in the clouds.  If you fly a single-engine airplane, you need to prepare for the catastrophic power loss in instrument conditions.

In a single-engine airplane engine failure introduces relatively few decision steps. The airplane's tendency during the emergency is to continue ahead in a straight line, descending. This characteristic helps prevent either a stall or a spiral. In a twin, engine failure introduces a large number of sequential pilot decisions, each with potentially adverse consequences ... all while the airplane (under the influence of asymmetric thrust) is attempting to radically diverge from a controlled path in all three axes. It takes regular, intense training (ideally in a simulator where such things can be realistically presented and safely practiced) to be proficient in overcoming aircraft tendencies, and making safe and proper decisions.

It’s hard to argue the 'single vs. twin' debate ... especially with someone who had just put a single-engine airplane down off-airport following a catastrophic engine failure.  This endless debate has no statistically provable answer (many twin-engine failures end with a successful single-engine landing and no accident report, and even some in-flight engine failures in single-engine aircraft end up with a glide to a runway and don’t land in the record books).  I do have some information, however, that helps draw some conclusions about the relative safety of single- and twin-engine airplanes.

Once a year, aircraft owners lay their airplane bare while an expert methodically checks and prods it for any indication the standards under which it was produced or modified are no longer met. It's called the annual inspection. A vital task to assure airworthiness (all too often this is the only real going-over an airplane gets each year), the "annual" is a pass/fail exam ... and owners wonder what their options are if the inspector turns thumbs down.