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TBM Technique: Landing in style

Prop-strike prevention 101

All airplanes have their quirks and “gotchas”—traps for the unwary. The TBM series of turboprop singles has its modest share, but one in particular—the propeller arc’s proximity to the ground—has drawn increasing attention lately.

Landing

Some views from Simcom’s TBM 930 simulator: Taking off from Orlando Executive Aiport. Between layers above the Sierra Nevada. Descending to the Palm Beach International Airport. On a high-speed ILS approach into Palm Beach International Airport.

Click on image for slideshow

An effort has emerged to educate TBM pilots about the risk of a prop strike while landing. The exact number of prop strikes is unknown. Yarns and lore aside, some members of the TBM pilot community say insurers are taking note.

The setup begins with a few of the TBM’s design essentials. Its Pratt & Whitney PT6A engine provides the power (700 shaft horsepower in earlier models; 850 shp in more recent versions) to give late-model TBMs max cruise speeds as high as 330 knots. The engine is installed at the end of a longish nose section, which gives TBMs such aggressive-looking—and, some would say, attractive—snouts.

Out on the tip of that snout is a huge four- or five-blade Hartzell propeller with a 7.5-foot diameter. This provides the thrust needed for the TBM’s light-jet speeds. But that large-diameter propeller arc spins a mere 8.15 inches from the ground—assuming a properly inflated nosewheel strut. That’s pretty close. So, a tight propeller-to-ground clearance endures as a TBM quirk.

So does a nearly horizontal stance. As it sits on the ramp, the airplane’s pitch is a tiny 1.7 degrees nose-up. From the cockpit this gives a great view ahead, over that long nose. It should also serve as a reminder of just how low the prop arc rides.

Touchdown

Photography by Mike Fizer Dierk Reuter's graph shows ideal and risky combinations of touchdown pitch and airspeed values. The ideal touchdown attitude (next image) is four to seven degrees nose-up pitch, and airspeed at or slightly below 1.3 VSO. The TBM 930’s Garmin G3000 primary flight display includes a green circle on the airspeed tape, showing 1.3 VSO for the airplane’s specific weight and landing configuration. An angle of attack (AOA) indicator is below the airspeed tape. The white line extending from the AOA’s scale also marks 1.3 VSO. The airplane’s yellow attitude indicator matches the pitch attitude set by the magenta flight director command bars. The simulator—technically, a Level 6 Aviation Training Device—doesn’t move but its visual presentations are impressive..

Click on image for slideshow

By themselves, this collection of quirks is of little import. But add poor landing technique to the mix and you’ve got a recipe for trouble. Like all too many other pilots, some TBM drivers fly their final approaches too fast. Igor Lucas, an assistant manager and TBM instructor at Orlando’s Simcom Aviation Training Center, says that there’s a tendency to come down final at 90 knots, or faster. “That’s way too fast,” he says. “The goal is to approach the touchdown zone at a VREF of 1.3 VSO [1.3 times the stall speed in the landing configuration]. At lighter landing weights, for example, the TBM 930’s proper approach speed can be 75 knots [at a 5,700-pound landing weight] or 77 knots [at a 6,000-pound landing weight].”

A body of evidence indicates that some pilots fly faster, no matter the landing weight...the result can be wheelbarrowing in a nose-down attitude; excessive floating as airspeed is bled off; and, in the worst case, a prop strike.At max landing weight, VREF is precisely 83 knots for the TBM 900/910/930/940 series, although it’s most often rounded off to 85 knots. For the TBM 700 and 850 models, it’s 80 to 85 knots. In the TBM 910, 930, and 940, pegging the primary flight display’s angle of attack indicator at its white reference line is a quick way to accurately fly at 1.3 VSO.

But for whatever reason, a body of evidence indicates that some pilots fly faster, no matter the landing weight. Perhaps they’ve gotten away with this in the past. Perhaps it’s the “10 knots for the wife and kids” calculus that equates extra speed with safety. Maybe pilots like to see the runway over that longish nose. Maybe airspeeds hovering around 80 knots make pilots uncomfortable knowing that the airplane is designed for 300-knot-plus cruise speeds. Whatever the case, the result can be wheelbarrowing in a nose-down attitude; excessive floating as airspeed is bled off; and, in the worst case, a prop strike—with or without porpoising. It’s worth emphasizing that this behavior isn’t exclusive to TBM pilots. You can see pilots making high-speed, flare-free landings at any airport on any given day.

Higher approach speeds translate into lower angles of attack and a flat attitude over the threshold. “We see 2-degree pitch attitudes all the time,” Lucas says. “And that’s when a prop strike is very likely. A little bit of strut compression is all it would take. Think of that 1.7-degree ramp attitude. You need to fly at a pitch attitude of 4 to 7 degrees nose-up to have a good margin at touchdown, and certainly no lower than 3 degrees. That way you’ll land main gear first.”

John Warnk, Simcom’s Orlando, Florida, training center manager, puts it this way: “You can’t just fly to the runway and do a chop and drop.” He says pilots must learn to land the main gear first, then slowly lower the nosewheel for its own landing. “It’s more like an airliner landing,” Warnk says. “You have to fly precise airspeeds for the approach and touchdown.”

Dierk Reuter, a TBM 930 owner, became interested in the issue when he kept hearing anecdotal reports from flight instructors and prop-strike victims. A pilot’s typical description of events leading up to the strike usually involved a “normal” approach disrupted by a wind gust. A self-professed “data guy,” Reuter began recording several TBM pilots’ landing performance on data cards installed in their multifunction displays. One dataset sampled 100 pilots’ data cards for a one-year time frame. The cards logged landing performance parameters—airspeed and attitude on touchdown—in files that recorded 10,000 landings. These results were extrapolated to compare against estimates of landing performance among all TBMs in the fleet, assuming each pilot flew 150 hours per year. The assumption was that pilots in the entire TBM fleet have 70,000 landings per year.

“You can’t just fly to the runway and do a chop and drop. You have to fly precise airspeeds for the approach and touchdown.”Based on his findings, Reuter’s analysis showed that 14 percent of his 100-pilot sample experienced touchdowns in the “caution” range, where landings were made at airspeeds in the 90-plus-knot range, and pitch attitudes were 3 degrees or less. Three percent of landings were flat-attitude arrivals with nosewheel touchdowns, where prop-strike potential is high. If this was representative of those 70,000 TBM landings, it meant there could have been a fleet annual total of 10,000 “caution” landings and 2,000 nosewheel touchdowns.

Reuter’s next step was publicizing his findings at TBM Owners and Pilots Association conventions, and sharing his data with Daher. The intent is to use the landing performance findings in publicity and teaching campaigns.

Reuter and a fellow TBM owner, Phillip Bozek, used the landing data to create learning experiences incentivized in the form of spot-landing contests. The first contest in July 2020 had eight contestants and was held at Howell, Michigan’s Livingston County Spencer J. Hardy Airport. The emphasis was on stabilized approaches and, of course, landing at the proper airspeed and attitude. Some contestants hired instructors to practice up, so this learning approach seems to show promise. Coming in at first place was TBM 850 owner Jason Robertson, who took home a distinctive, ornate trophy. “I landed right on the target zone—the beginning of the ILS touchdown bars—but I guess I forgot that the main gear are behind me, so they touched down four feet short,” Robertson said. “But I was still the closest.”

A second spot-landing contest is scheduled to take place at the Naples, Florida, Municipal Airport in February 2021. Another trophy—and, of course, commemorative T-shirts!—will await the most precise pilots.

Reuter continues to collect data and promote education. Most encouraging is that pilot scores are on an upward trend. A year ago, one new TBM pilot’s landings had a 14-percent compliance score with target airspeeds and attitudes. Since then, he’s been practicing. Now his scores are among the top four, and he qualified to land on the very short (2,119 feet), challenging Runway 10/28 at the Gustav III Airport in St. Jean, Saint Barthelemy Island in the Caribbean.

Simcom has incorporated a prop-strike awareness module in its TBM courses, using the data Reuter gathered. It’s heavy on promoting stabilized approaches and strict landing profiles.

For example, on precision approaches at maximum gross weight, the steps begin with a power reduction to 35 percent torque, which yields approximately 150 KIAS. At two dots above the glideslope, extend the landing gear. At one dot above the glide-slope, extend the flaps to the first, takeoff position. At glideslope intercept, reduce power to 22 percent torque, leave it there, and go to full flaps. The airplane will slow to the recommended 85 KIAS (with an acceptable deviation of minus 5 knots/plus 10 knots) as it follows the glideslope to the runway. It’s important to trim for 85 KIAS so that you won’t be nose heavy and holding excessive back-pressure during the flare and touchdown. Additionally, at 50 feet agl, make sure that torque is at or slightly above 10 percent; this also prevents the airplane from becoming nose-heavy as the threshold nears. Right before touchdown, begin adding back-pressure for the flare. Going to flight idle should be delayed until immediately before touchdown—at which point you should be holding the nose at the 3-to-7-degree “sweet spot” pitch attitude.

Simcom also provides a “high-speed” approach procedure that uses the same torque setting but delays full flap extension until 1,000 feet agl. After that, the airplane slows to 85 KIAS (again, minus five/plus 10 knots) by 500 feet agl. At 50 feet agl, back pressure should be applied slowly, and then held at three to seven degrees nose-up for the touchdown.

It all boils down to this: Fly final at an appropriately slow airspeed, reach 1.3 VSO on short final, and flare to hold the nose up for a full-stall touchdown. If this sounds anything at all like the approach and landing profile you’d perform for any high-performance single, you’re right.

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Thomas A. Horne

Thomas A. Horne

AOPA Pilot Editor at Large
AOPA Pilot Editor at Large Tom Horne has worked at AOPA since the early 1980s. He began flying in 1975 and has an airline transport pilot and flight instructor certificates. He’s flown everything from ultralights to Gulfstreams and ferried numerous piston airplanes across the Atlantic.

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