Landing on an aircraft carrier always has been a challenging maneuver, distinguishing naval pilots from all others. Since the earliest days of the experimental USS Langley (CV-1), pilots have been aided by the landing signal officer (LSO). At first, the LSO’s outstretched arms waved semaphore flags to indicate whether the pilot’s approach was too low, too high, or okay. As aviators gained more experience with carrier landings, new signals were added: arms outstretched signified a clear deck; a 45-degree slash told the pilot to throttle back and land; a frantic waving of the flags overhead indicated it was unsafe to land.
LSOs became ubiquitous figures on flight decks, positioned on the port side near the stern. The semaphore flags eventually were replaced with various types of paddles, some with brightly colored strips of cloth that fluttered to catch the pilot’s eye. “Paddles” soon became the LSO’s trademark and nickname. LSOs, naval aviators themselves, continue to aid pilots today as they approach U.S. carrier decks, but the semaphore flags and paddles long since have given way to sophisticated optical landing systems.
The first such system used mirrors and was conceived by Commander Nicholas “Nick” Goodhart of the Royal Navy in 1951 in response to the high landing-accident rates experienced by the fast, heavy jets then coming into service on board carriers. Early jets had a slow throttle response thanks to the need to spool up the engine, which left little margin for error.
Goodhart, an experienced test pilot and engineer, proposed the use of a concave mirror to project an optical path that would provide guidance for landing on board ship. He had verified the concept in his office using a secretary’s pocketbook mirror and flashlight. He drew datum lines on the mirror in lipstick and placed it on the desktop. “Flying” down to the desk, and keeping the light between the lines, his nose and chin would always touch the desk at the same spot. Goodhart convinced the naval aeronautical research committee to approve the idea, which was tested at the Royal Aeronautical establishment, Farnborough, in November 1953.
Goodhart’s system consisted of a cylindrically concave cast-aluminum mirror, 5-feet, 6-inches wide and 4-feet high. Four evenly spaced 100-watt reference lights extended 6 feet on either side of the mirror at its midpoint. Each had a parabolic reflector with a 10-degree beam width. The light sources for the mirror came from eight 240-watt lights, on a 20-foot line 160 feet from the center of the mirror.
Don Engen, then a U.S. exchange officer with the Royal Navy at the Empire Test Pilot School, was one of the pilots to evaluate the new system. As he wrote years later for The Hook, the journal of the Tailhook Association, “The system was so simple and easy to fly that I saw the field trials could be very short.”
The prototype was moved to Portsmouth, England, where it was installed on board HMS Illustrious, a World War II aircraft carrier. Engen, flying a Sea Vampire Mk 21, arrived over the Illustrious at 1130 on 19 November 1953 and descended to begin his part of the landing trials, which were conducted without an LSO. Someone forgot to turn on the main light source on his first pass. Engen landed without guidance from the system, catching the “4-wire.” After lunch, he tried again. This time, the light was on, and the trials proceeded smoothly. Over the next two days, Engen made 17 approaches and landings using the mirror system. It performed as envisioned. The Royal Navy’s mirror landing system, Engen reported, was an unqualified success and should be used by the U.S. Navy. Engen’s report prompted the Navy to conduct its own trials of the new system.
These were held in late September 1955 on board the USS Bennington (CVA-20), which had just been converted to an angled deck carrier—another British innovation. Commander Bob Dosé made the first landing. Dosé, also writing in The Hook, remembered coming down the glide slope on the mirror thinking, “How easy. Why didn’t we do this long ago: It’s just a natural.”
The experimental system installed on board the Bennington consisted of a line of source lights located far aft, on the angled deck’s port side, with green datum lights located on each side of a large concave mirror, which was mounted farther forward on the same side of the deck. The amber-colored source lights were beamed forward and reflected aft by the mirror, which centered the reflection so that it appeared as one elongated spot. The green datum lights indicated whether the approach was high, low, or on the glide slope.
The pilots of Air Development Squadron (VX) 3 who conducted the trials liked the new system because it gave them immediate knowledge of their vertical position in the groove, whether they were high or low. Their reaction and control of the airplane was not filtered through a person on deck, outside the airplane. They instead received information immediately and at first-hand, which improved pilot reaction time by seconds, which was especially important because of the jets’ faster speed/closure rate with the deck.
The British called the mirror’s reflection the “blob of light,” but someone in VX-3 dubbed it the “meatball,” World War II slang for the Japanese hinomaru emblem, which the light resembled. Later, this was shorted to the “ball.” When an aircraft is on approach in the groove, the LSO will ask the pilot in the approaching aircraft to “Call the ball,” meaning “Tell me when you can see the light.” Answering in the affirmative, the pilot will then “fly the ball,” so to speak, onto the flight deck.
The original optical mirror landing system adopted by the Navy has been improved and upgraded, and today the concave mirror is replaced by a Fresnel lens. This allows more feedback to be given to pilots on final approach. Colored lights project through the Fresnel lens to indicate when the aircraft is at the desired altitude in the approach at any distance from the ship. If the aviator sees a red light at the bottom, it means the aircraft is dangerously low, and the LSO may make the light flash to signal a wave-off, requiring the pilot to go around for another attempt.
The latest version of the Improved Fresnel Lens Optical Landing System MK 13 Mod 1 was installed on board the USS Dwight D. Eisenhower (CVN-69) in 2015. Newer aircraft carriers also are being equipped with a software-based landing system, originally known as Magic Carpet but since renamed “precision landing modes,” that will soon manage the landings for most carrier-based fixed-wing aircraft.
Douglas E. Cambell and Stephen J. Chant, “Fresnel Lens Optical Landing Systems (FLOLS),” Patent Log (Syneca Research Group, 2013).
Robert G. Dosé, “The First Mirror Landing,” The Hook 15, no. 3 (Fall 1987): 27.
Robert Dunn and Robert C. Rubel, “Gear Up, Mishaps Down: The Evolution of Naval Aviation Safety: 1950–2000,” Naval War College Review 71, no. 3 (Summer 2018).
Donald D. Engen, “‘Roger, Ball’—How It Started,” The Hook 15, no. 3 (Fall 1987): 24.
“It’s Done with Mirrors,” Naval Aviation News, 20 (date of publication unknown).
“Obituary: Rear-Admiral Nicholas Goodhart,” The Telegraph, 22 April 2011.
“USS Bennington Tests Out New ‘Mirror Landing Aid,’” USS Bennington Association.