When Slower Is Better

Trouble is, we all slip into bad habits now and then, and recently, I did exactly that. I had been flying return-to-service check flights after maintenance and annual inspections on 300/400 Cessnas, Dukes and miscellaneous other twins, and I was so used to seeing 110-/120-knot approach speeds that I had forgotten how much easier it was to fly more slowly. I was sloppily using 85- to 90-knot approach speeds in my LoPresti Mooney.

Part of the good/bad news about flying a variety of airplanes on a regular basis is that you sometimes don't have all the information you need on approach speeds. Though it's true there are other contributors to approach speed besides dirty stall (i.e., stall characteristics, crosswinds, aircraft weight), maintaining a proper margin above stall is the primary concern.

Forty years ago, I flew a Super Cub in Alaska that stalled at less than 40 knots, and I remember droning around the pattern at 50 knots and feeling as if I could jump out and run alongside during the flare. Operationally, the difference between a 50- and 70-knot approach speed is far more than 20 knots. Indeed, it seems as if you're covering ground at double the speed. The Cub's wing was so large and the stall so slow that with any significant wind, the aircraft's owner and I often saw takeoff and landing rolls shorter than 300 feet.

Today, the vast majority of general aviation singles sport stall speeds in the 50- to 60-knot range, with fixed-gear models flying more slowly, and retractables stalling more quickly. Perhaps sadly, there are few Cubs available these days. Discounting LSA, airplanes such as the Top Cub and Aviat Husky are among the few that can claim stall speeds below 40 knots.

Accordingly, I've adopted the universal, super-simple rule for jumping from airplane to airplane. According to the FARs, dirty stall speed on certified singles can't exceed 61 knots, and the generic rule for approach speed is to use 1.2 to 1.3 V_so.

That means on a Bonanza, Mooney, Malibu or Centurion, I typically shoot for a VFR approach speed of about 1.25 V_so. That works out to about 75 knots on a high-performance retractable, and yes, I'm aware that's a little sporty for a PA46, especially at gross. Piper recommends a minimum 78 knots down final on the Mirage, though Cessna allows 72 knots for short-field approaches in the P210.

For lighter, fixed-gear singles that I know enjoy slower stall speeds, I'll stick with 1.2 V_so, or about 65 knots in a Skyhawk/Archer/Sundowner/Tiger.

There's nothing revolutionary here. If the winds are gusty or shifting from side to side, I'll ad lib my speed as necessary. The important thing is to avoid operating so slowly that you enter the region of reverse command in which induced drag becomes so high that more power is required to fly slower (popularly known as the "backside of the power curve"). Naval aviators must learn the procedure to come aboard a carrier, but it's definitely not recommended for most GA types. Experienced bush pilots also sometimes use this technique to land on extremely short runways.

(Back in the early 1980s, Maule demo pilot Dan Spader showed me a minimum-speed approach that was deep into the reverse-command realm. Using full flaps, significant power and an approach speed about three knots above stall, Spader landed a new Maule on the ramp in front of the company factory in Moultrie, Ga., by using a quick blast of power to cushion the touchdown during the nearly nonexistent flare. He planted the airplane perfectly three-point, and stopped in less than 100 feet. Don't try this at home, or anywhere else.)

Sure enough, when I reduced my Mooney's approach speed to between 70 and 75 knots, things automatically improved. The only major disadvantage of the slower speed is an abbreviated flare. If you're having problems judging your height during the round out, it might be better to stick to the higher speed. Accept that you need to be more precise in judging your approach to the threshold, and that you need more runway to stop.

A too-fast approach speed is probably the most common contributor to bad landings. Part of the reason is that student pilots learn early on that stalls are the most dramatic maneuvers most aircraft will ever perform. Even a Cherokee 140 assumes a hobbyhorse pitching during stall that can be disconcerting for a new pilot. For that reason, some pilots avoid even approaching a stall near the ground.

Perhaps ironically, that's exactly contrary to traditional wisdom. Rod Machado, a master CFIIM and author of several books on flying techniques, says all a pilot's problems are compounded by flying too fast on final. "Many pilots land too fast because they're afraid to fly the airplane slowly," says Machado. "They're so frightened of stalling that they fly at 40 to 50 percent above stall. This makes the elevator more sensitive, prolongs the flare, introduces a greater chance of ballooning and makes depth perception more difficult."

For better or worse, some airplanes don't have any choice but to use high approach speeds. The highest speed I've personally experienced on approach was in a Northrop T-38, better known as the "White Rocket." I flew that airplane twice in conjunction with stories on USAF training techniques, and I was impressed by the high landing speed. Air Force regs didn't allow me to actually touch down, but on both flights, my instructor pilot allowed me to make several approaches.

The base approach speed for the T-38 is 155 knots; then, you add one knot for every 100 pounds of fuel on board above 1,000 pounds. In other words, if you return to base with 2,000 pounds of fuel remaining, then you should come across the fence at 165 knots. That's faster than most GA singles cruise. Imagine landing an F33 Bonanza at full cruise, and you have some idea of the problem.

The space shuttle may not hold the record for approach speed, but it returns to earth at high Mach. Without the benefit of power or the ability to go around, the shuttle turns final at an initial 300 knots, with an impressive 20-degree glideslope (standard glideslopes are three degrees) starting at about 12,000 feet, roughly one minute from touchdown. The pilot then slowly pitches the nose up to maintain a 1.5-degree glideslope to bleed off speed, and the shuttle crosses the fence at about 210 knots. (The shuttle has no easily defined stall speed, as it's an unpowered, delta-wing glider, and the minimum usable angle of attack is minus-10 degrees, a pitch-down condition. Most GA wings stall in the 15-/20-degree range.)

Pilots don't purchase fast airplanes to fly slowly, but final approach is no time for speeding.

Bill Cox is in his third decade as a senior contributor to Plane & Pilot. He provides consulting for media, entertainment and aviation concerns worldwide. E-mail him at flybillcox@aol.com.