Unstable approach

NTSB Accident No. WPRFA208

By David Jack Kenny

Despite the emphasis placed on it throughout training, one of the lessons that often seems to be forgotten after the checkride is the importance of the stabilized approach. True, some aircraft are more tolerant of imprecision than others, and they differ in their tolerances for imprecisions of different kinds. A Diamond DA-40 doesn’t want to stall with a perceptible break – but cross the threshold 10 knots fast and 100 feet high, and you’ll likely sail right past the departure end. Early-model Cherokees are reluctant to stall, too – but the pilot who lets one get low and slow on final may have trouble persuading it to climb again.

Mooneys are optimized for speed and efficiency in cruise, so their thin, laminar-flow wings produce a lot of lift and relatively small amounts of drag at a given airspeed. That puts a premium on nailing approach speeds precisely. With just a little excess airspeed after entering ground effect, they’ll float for what seems like forever. An experienced Mooney CFI puts it this way. “For every knot you are fast, add 100 feet to the required landing distance”. The only real cures are to be exactly on your airspeed and altitude targets by the time you’re down to 500 feet agl on final ... or prompt and decisive in committing to go around.

Shortly after 8:00 a.m. on the Fourth of July, 2015, the pilot of a 1965 model M20E contacted the tower at McNary Field in Salem, Oregon to report that he was inbound for landing from the south. He’d departed the airport on a local flight about an hour earlier. The controller cleared him to land on Runway 34, and a few minutes later the Mooney appeared on final. The controller later recalled that its landing gear appeared to be down and locked, and its descent path looked normal until it levelled off around 10 to 20 feet above the runway’s aiming point. From there, it continued to float at least another 1,000 feet down the 5,145-foot runway. Around mid-field, it began a shallow climb.

A second witness watching from the southeast corner of the airport agreed that its approach path seemed conventional, and that he’d heard the Mooney’s engine pulled back to idle as it neared the runway. Shortly after the tires touched down, though, he saw the nose pitch up to begin a series of bounces of increasing amplitude, with the last touchdown occurring nose-first to the accompaniment of a metallic noise. That bounce launched the airplane six to eight feet back into the air, after which the engine noise increased – but, in the witness’ opinion, “sounded bad.”

A third witness confirmed that the airplane began a shallow climb with gear and flaps retracted at what sounded like a low power setting with occasional misfires. He and the tower controller agreed that after attaining an altitude of about 100 feet agl, it banked increasingly hard to the left before catching a wingtip and cartwheeling. The solo instrument-rated private pilot died in the crash.

Neither his total flight time nor his experience in that make and model have been determined. His most recent medical application, filed three months before the accident, reported 250 hours in all aircraft, but an application filed eight years earlier claimed 500. His logbook was not recovered, and the NTSB was unable to find any details of his transition training.

They did note that the Mooney’s operating manual cautions that “Under no circumstances should the aircraft be allowed to touch down in a nose-low attitude or at too high an airspeed. Either of these conditions will allow the nose wheel to contact the runway first, which may cause the aircraft to porpoise....” The investigators concluded that that’s exactly what happened, and that the pilot reacted to the bounces with excessive back pressure. By the time he decided to go around, his airplane was already close to its critical angle of attack. Attempting a left turn at low altitude rather than establishing a stable climb was enough to push it over the edge.

It’s not entirely clear whether that final nose-first touchdown caused a prop strike; the NTSB’s probable-cause statement says this was “likely.” If it did, the effect on go-around performance is difficult to estimate, but couldn’t have been beneficial. Easier to gauge is how much better things would have gone if the pilot had decided to go around when it became clear that he was coming in fast – in other words, that his approach wasn’t stable.