Aircraft carrier landings are highly automated
Today President Bush will fly aboard a US Navy S-3B Viking to USS Abraham Lincoln, hundreds of miles west of San Diego. The Viking is a four-seat jet aircraft that makes cable-arrest landings on carriers, just as fighters do.

Carrier landings are highly automated nowadays. The toughest things pilots have to do to land safely is make sure they are flying straight down the centerline of the landing strip on the carrier deck and make sure their rate of descent onto the deck is correct. When these things are done right the plane hits the deck and its arrestor hook grabs one of the cables across the deck that slow the plane to a halt within a couple hundred feet or so.

Squaring up on the centerline is not as easy as it seems. Modern carriers are "angle deck" ships, meaning that they are designed to launch and recover aircraft at the same time. Launching aircraft are catapulted off the bow straight ahead, but landing aircraft fly onto a part of the flight deck that angles off to the ships port (left) side. Hence a pilot cannot line up straight down the ship. (The angle deck can also launch as well as recover.)

The further away pilots can square on the centerline, the happier they are. But even enormous aircraft carriers appear too small from about a mile away to offer visual clues to line up. Lights aboard the ship called drop lights are effective inside a mile, as is the visual image of the ship itself, called the "carrier box." A laser system called Long-Range Lineup System uses eyesafe colored lasers to guide the pilot well over a mile away. Seeing an amber laser means that the plane is on centerline, right means green and red means left. This system is installed aboard Abraham Lincoln.



As for glide path, carriers use fresnel lens systems similarly color coded, except that the colors indicate whether the plane is too high or too low or on path for landing. Commercial airports use fresnel systems, also. The pilot flies so that he sees the correct color all the way to the deck. An improved fresnel system uses 12 fiber-optic cells to give the pilot the reference about twice as far as with the older system, as much as a mile. This system is also installed aboard Lincoln.

A new system, completely automated, is in final development. It is called Joint Precision Approach Landing System (JPALS) and it uses GPS technology to replace the colored lights systems. Potentially, this system could enable aircraft to land with the pilot simply observing rather than actually flying the plane. It is also intended for helicopters and unmanned aircraft. This system was successfully tested aboard USS Theodore Roosevelt using an F/A-18 as a test plane.

Hands-off landings are not new; the first one was made 40 years ago, using the then-new automatic carrier landing system. ACLS uses ship's radar, radio and automatic systems aboard the plane to control flight controls and engines to bring the plane to landing automatically. JPALS' advantage is that it is more precise and can perform air traffic control as far as 200 miles away from the carrier, potentially eliminating the need to "marshall" airplanes in the sky in order to begin landings.



The centerline is obvious here. The "ball," or the fresnel lens for glide path control, is the green light on the left side of the deck. Below it, at about eight o'clock, is the landing signal officer's station. Altogether, the landing area is 450 feet long. There are four arresting cables; pilots try to hook the third one.

I should also mention that for conditions of poor visibility such as fog or rain, there is an instrument carrier landing system that simulates the optical aids on the pilot's head-up display.

So carrier landings are still challenging, but are generally not the white-knuckle experiences that they were in the old days.

Update: I spoke this morning to a retired rear admiral whom I know. He was a naval aviator who commanded a carrier battle group before he retired. He said: