Proficient Pilot

A herd of CATs

April 1, 2005

Pilot and journalist Barry Schiff has been flying for more than 50 years.

My first instrument instructor told me that once I learned to shoot an ILS approach at home, I would be able to do the same everywhere else in the world. "This," he said, "is because all ILS approaches are the same. Master one and you've mastered them all."

That might have been true in the 1950s when there was only one type of ILS approach. Today there are several.

The conventional ILS approach is called a Category I, or CAT I, approach. It has a decision height (DH) of no less than 200 feet and requires a minimum visibility of no less than a half-mile (or a runway visual range, RVR, of 2,400 feet near the touchdown zone). An exception allows us to make an ILS and land when the RVR is only 1,800 feet if the runway has centerline lights.

In 1962 and in response to a growing need by the airlines for reduced approach minimums, the FAA issued a notice of proposed rulemaking (NPRM) that sought comments on what eventually would become known as a CAT II approach (with a DH of no less than 100 feet and a minimum RVR of 1,200 feet).

Then-AOPA spokesperson Michael V. Huck responded to that NPRM by stating, "Light aircraft are more maneuverable and can operate more safely under lower minimums than can transport aircraft. We suggest, therefore, that the minimums for light aircraft performing [an ILS] approach be just half those established for transport aircraft."

Huck persevered and ultimately became the first general aviation pilot to be certified for CAT II approaches. This set the stage for the drama that unfolded at John F. Kennedy International Airport on April 2, 1968. The reported weather consisted of a 100-foot ceiling with the RVR down to 1,200 feet. This forced jetliners to divert while others — I was a copilot aboard one of them — held helplessly, hoping for conditions to improve. Huck arrived in the area on a personal flight from Washington, D.C., and neither diverted nor held. He instead guided his Piper Aztec toward the runway and made the first-ever CAT II approach at JFK. (You cannot imagine how embarrassing it was for the captain to tell our Boeing 707 passengers that the only aircraft to land at JFK that morning was a Piper Cub.)

This eventually led the FAA to allow GA pilots to become certified for CAT II approaches when operating Category A aircraft (those with an approach speed of less than 91 knots).

My friend and accountant, Gene Korney, plans to obtain CAT II certification in his Beechcraft F33A Bonanza. Will he have an opportunity to use it during actual conditions during the six months for which it will be valid? Probably not, but he savors the challenge of improving his instrument skills in this manner.

The airlines have the edge over general aviation when it comes to CAT III approaches. This is because the airplane must be equipped with either a head-up display or an autoflight system capable of making automatic landings.

There are three types of CAT III approaches, and all can be made with "ceiling zero." CAT IIIa allows an approach and landing at an RVR of less than 1,200 feet but no less than 700. CAT IIIb permits an RVR of less than 700 feet but no less than 150. No aircraft has yet to be certified for CAT IIIc, which eventually will allow an approach and landing during "zero-zero" conditions.

In a sense, the first CAT IIIc, or "blind" approach and landing, was made on September 24,1929, by then-Lt. James H. Doolittle. He used a Consolidated NY-2, the first airplane ever equipped with an attitude horizon and a directional gyro (designed for this flight by Elmer Sperry Jr.). The biplane also was equipped with a Kollsman precision (sensitive) altimeter and a system of vibrating reeds that enabled Doolittle to follow a radio beam aligned with the runway. The landing gear was reinforced to absorb excessive shock.

On that historic morning at Mitchel Field in New York, Doolittle climbed into the front cockpit of his biplane and pulled a canvas hood over the entrance so that he could not see outside the aircraft. A safety pilot, Lt. Ben Kelsey, sat in the rear.

Doolittle took off toward the west, climbed to 1,000 feet, made a one-eighty to the left, and then flew several miles until he was sufficiently east of the airport. He made another one-eighty, intercepted the beam, descended to 200 feet, and leveled off. After passing a fan marker near the end of the runway, he began another descent and "flew the plane down to the ground using the procedure that [he] had developed," Doolittle wrote in his book I Could Never Be So Lucky Again.

The first automatic landing was made in 1937 by Army captains Carl J. Crane and George V. Holloman at Wright Field in Ohio. They used a Fokker-designed high-wing monoplane, the General C-14B, equipped with a Sperry "gyropilot."

The first airplane certified with an autoland system was the Lockheed 1011 TriStar in 1972. The autoflight system was designed by Lockheed, Collins, and Lear-Siegler, and was based on the one developed for the space shuttle. It still is regarded by many as the autopilot of choice when making a CAT III approach.

Join me next month, and we'll make a CAT IIIb approach into the Paris Charles de Gaulle International Airport using the autoland system in a Lockheed 1011.


Visit the author's Web site ( www.barryschiff.com).