A high-wing twin is on final approach on this video found on YouTube. The airplane nears the threshold, and moments later, the pilot’s belated and excessive rotation results in the airplane ballooning upward and then slamming down hard on the runway in a flat, or even a nose-down attitude. A classic porpoising sequence follows.
Another YouTube video shows a similar sequence in a Cessna 172. One difference: A go-around breaks the sequence of bounces and nose-low ground impacts. The moment of recovery is lost to the viewer as the airplane passes behind an intervening snowbank, but the roar of the engine as it comes up to climb power provides a comforting reassurance that corrective action has been taken.
Such videos retain some value as teaching tools for pilots. Watching the two scenarios unfold, it is only in the last few seconds of each approach when you can clearly diagnose the excessive airspeed, and the failure of each pilot to pitch the airplane to a proper landing attitude. Finally, the failure to recover correctly from the first bounce exacts its toll.
Porpoising takes longer to explain verbally or in writing than it does to ruin a landing. That’s what makes it so important to recover at the first indication—the first bounce.
Porpoising is official training lingo because it is so precisely descriptive. “In a bounced landing that is improperly recovered, the airplane comes in nose first setting off a series of motions that imitate the jumps and dives of a porpoise—hence the name,” explains the FAA’s Airplane Flying Handbook. “The problem is improper airplane attitude at touchdown, sometimes caused by inattention, not knowing where the ground is, mistrimming or forcing the airplane onto the runway.” Improper airspeed control is another known cause, obviously related to the others listed.
Do yourself a favor on your next flight: Add a practice go-around to whatever else is on your flying agenda for the day.
The most regrettable thing about porpoising is that the mishaps can be stopped as easily as they get started—at least until the out-of-phase oscillations (pitch increasing as the airplane rebounds into the air, followed by a desperate lowering of the nose as the aircraft begins to descend) result in gear damage.
A decision must be made: How you respond to the problem depends on the severity of the bounced landing (but a go-around is never a wrong response).
Immediately after a light to moderate bounce, the pilot should make a simultaneous addition of power and a pitch correction. The added power buys some time before the next touchdown, and should cushion it somewhat. The pitch adjustment should establish a proper landing attitude. The pilot must resist temptation to shove the nose down, which will only result in a worse impact than the first as the aircraft sinks toward the ground. With order restored, the pilot can proceed to reduce power again and perform a normal roundout and flare or at least execute a “cushioned” touchdown.
If the aircraft has rebounded into a severely nose-high attitude several feet above the runway, with recovery impossible before the next ground contact, the other option is a go-around. This may not avoid the second bounce, but the response can still terminate the porpoising scenario.
A typical end result of a porpoising left uncorrected is a collapsed nosewheel, done in by being made to bear the full brunt of the aircraft’s contact with the ground. That was the consequence of a landing attempt pursued (in a tailwind) beyond safe boundaries last June in Ann Arbor, Michigan.
“The pilot was cleared to land on Runway 30. The recorded wind was 110 degrees at 12 knots, gusting to 17 knots. The airplane touched down at 50 to 60 knots and about 700 feet short of the intersection with Runway 6-24. A slight upward slope at the intersection caused the airplane to bounce and become airborne. The pilot contemplated making a go-around, but elected to continue the landing. Upon touching down again, the airplane began to porpoise, the nosewheel collapsed, and the airplane came to a stop,” a National Transportation Safety Board accident summary said.
Things happen fast after that first bounce. So practice your landing technique until your corrective responses are accurate, instantaneous, and—because of your growing skill—unnecessary.