Anatomy of a Carrier Landing:
The basics of landing on a carrier are simple: get the airplane into the wires with the right angle of attack, right speed, on centerline…
However, beyond that it gets complicated…the first topic is the physical layout of the deck, Wikipedia does a good job in describing the boat here:
https://en.wikipedia.org/wiki/Nimitz-class_aircraft_carrier
and for simplicity’s sake, I will stick to a Nimitz-class description…there are some minor variations even in that class, but the principles remain the same.
The angle deck (a British invention, back when they still had carriers…), is part of the landing area (LA), it allows the airplane to get airborne in the event it misses the wires. It’s about 650’ long. A centerline is marked, and there are “foul lines” that denote the edges for safety reasons…
The 4 arresting gear wires are spaced 40’ apart and are transverse to the LA. The machinery for the AG is located just below the flight deck, on the O-3 level, and those “engines” are big hydraulic cylinders that put resistance on what is called a “purchase cable” – the actual steel cable that pays out as the airplane stops. The purchase cable is connected to a thicker replaceable steel cable element about 80’ long known as the “Cross Deck Pendant” and that CDP is what the airplane’s hook engages…it has to be tough…and it gets replaced fairly often…
The wires are numbered from stern to bow (direction of aircraft arrival), so the 1-wire is the closest to the stern, where the LA rounds down in a ramp at its rear most edge. From ramp to 1-wire is about 170’. The next 120 feet are the rest of the wires, leaving just over 300 feet from 4-wire to the top of the angle, where the airplane would have to be flying again.
The whole construct is designed to work within the engineering limits (load, etc.) of the airplane and the ship. The amount of strain that the AG engines can handle is limited…the F-14 pushed that limit…among the many elements of coordination for each landing was to set the resistance (weight setting) on the 4 AG engines…and each engine crew would check in with the weight setting for each landing. I mentioned previously that the max engaging speed for the F-14 was 119 KTs relative to the ship…that limit was hook strength at max landing weight of 54,000#, but abnormal landing configurations (like flaps/wingsweep, etc.) would change that engagement speed limit too…
The airplane approaches on a 3.5 degree glideslope, relative to the ship. This is slightly steeper than you would see at a regular airport but it accomplishes a couple of things: keeps the airplane farther above the ramp, keeps the airplane farther above the turbulent air of the deck until the last minute, and balances sink rate and power response of the airplane’s engines. Because the ship always has some amount of wind over it, the apparent glideslope, relative to the sea, is closer to 2.8 degrees with a nominal approach speed of 140 KIAS and 25 knots of wind…
The wind is interesting, the carrier can, of course, make its own wind, but the landing area is angled off the ship’s centerline by roughly 9 degrees, so when the carrier is making its own wind, there is ALWAYS a crosswind. Further, in that case, the turbulent airflow around the carriers own island (superstructure) creates a rough spot just aft of the ramp, where the airplane’s performance is affected. A quick response on the throttles is needed to compensate… On a perfect day, the carrier would manage its course and speed to get the combination of natural wind and ship’s wind right down the angle…this happens rarely, but it makes everything easier on the pilot. The ship is still a warship, and tactical considerations (threat, speed, sea room, course) trump landing considerations…
The airplane itself is designed for an approach angle of attack. That angle of attack (not airspeed, though for a given weight, the AOA produces a precise airspeed) ensures that the hook and landing gear are at their designed relationship for successful wire engagement. That AOA also ensures that the pilot’s eye is in the correct relationship to the hook (more on that in a minute).
Keeping the airplane on centerline is critical – for big wing airplanes, like the E-2, F-14 and S-3, an off center landing can result in a collision with parked airplanes on the flight deck. For all airplanes, centerline is important for the AG wires and for the accuracy of glideslope information. If the hook engages the CDP more than 10 feet off center, it causes unequal runout in the purchase cable and that wire has to be either re-set of the CDP has to be removed before the next landing.
And the next landing is 45-60 seconds later…
So, we have wind, AG setting, glideslope, AOA and centerline…now it gets interesting. If you were to get out a calculator, some math would reveal that on a 3.5 glideslope, 40 feet horizontally would be 30 inches vertically. The optical reference for the pilot, compensated for the airplane type, and presuming the airplane is at design AOA, targets the hook point exactly half way between the 2 and 3 wire…the precise middle of the wires in the LA.
So, to engage the 3-wire, the airplane has to be within 15 inches of the perfect glideslope, as well as on centerline and on AOA, while approaching at 140+ knots…In fact, to be on or above the 1-wire and on or below the 4-wire, the airplane has to be within 4 feet of perfect. Miss the 4 wire and a “bolter” is the result…the airplane has to get airborne again within the 300+ feet remaining. All Navy pilots select full power on touchdown in the event of a bolter.
The glideslope indicator (a Fresnel lens, known colloquially as the “meatball”) that pilots reference is extremely precise. At ¾ of a mile, the pilot can tell if they’re 10 feet high or low and at touchdown, the 15 inches is easy to see as well…the challenge is in controlling the aircraft with that degree of precision. While the basic angle for a carrier landing is set to 3.5 degrees inclination relative to the carrier, it can be raised to 3.75 degrees or 4.0 degrees in the event exceptionally strong natural wind, to get back to the apparent 2.8 degree glideslope that I mentioned earlier.
The lens itself projects a plane of light. That plane is inclined to the ship at the basic angle…but interestingly, that plane of light can be tilted left or right to adjust the height of the light plane over the centerline, thus compensating for the Pilot’s eye/Hook relationship unique to each aircraft type. As an example, Hook-eye on a Tomcat was 19.8 feet (vertically, at approach AOA) while it was roughly 15 feet for an F/A-18C. So, if the lens was set wrong in roll (compensation for hook-eye) then it’s pretty clear to see that the airplane could be several feet off in height…and as we saw above that’s the difference between a good landing and a complete miss…
To maintain the degree of precision needed for a successful landing, the pilot is constantly adjusting power, pitch, and angle of bank the entire way down…rapid, precise, minute adjustments to maintain AOA, centerline, and glideslope. The reward is an arrested landing. If any parameters exceed a reasonable deviation, then the Landing Signals Officer (LSO) will “wave off” the pilot – who has to select full power and climb away from the deck to try again.
In the daytime, the approach to the carrier is a completely visual affair – no radar, no air traffic controllers, just airplanes who know what order in which they should recover, and pilots who can space themselves out in that optimum 45-06 second interval. The pattern itself begins with the jets approaching from the stern at relatively high speed, making a 180 degree “break” turn, flying opposite direction and making a 180 degree turn to final to arrive at about 0.6 to 0.5 miles astern at 350-380 feet on centerline (just past the wake). AG and Glideslope indicator setting are double-checked, the landing area is checked clear, the pilot “calls the ball” (stating that they can see the meatball), that is acknowledged by the LSO (who can tell if the airplane is off by a knot or two, and knows if the airplane is high/low) and the airplane is flown to touchdown.
At night, or in bad weather, an instrument approach is flown to a visual hand-off at ¾ of a mile…and again, the pilot “calls the ball”…and the LSO answers “Roger Ball”, confirming that the airplane is in parameters to make the approach.
Wikipedia does a good job with this description:
https://en.wikipedia.org/wiki/Modern_United_States_Navy_carrier_air_operations
