Originally Posted By: JHZR2
What was the worst sea-state or deck pitch that you've had to take off and land in? Especially in those conditions, what was the rate of being a bolter (attempted vs successful landings)?
In addition to flying the big fighter, I was an LSO. In fact, I was an LSO in the fleet, then in the RAG (where I was the head of the carrier landing phase of instruction...a phase that washed out more young Tomcat drivers than any other...the F-14 was a handful to bring aboard), and then as the senior LSO on the boat, known as CAG Paddles.
https://en.wikipedia.org/wiki/Landing_Signal_Officer
So, I've seen pitching decks both from a pilot perspective and the LSO perspective. Worst I've seen was from the LSO perspective.
The LSO was absolutely critical in getting an airplane safely aboard in pitching deck conditions. The instrument guidance system (Automatic Carrier Landing System - ACLS) would guide the airplane to a commanded touchdown point on the deck. ACLS was stabilized in space, using the ship's own INS, so that the airplane received steady guidance regardless of ship's movement. Pretty interesting system, nothing like civilian approach guidance systems that are bolted to concrete and calibrated to solid, steady ground. ACLS used a radar to track the airplane. It was precise enough that every Navy airplane had a radar augmenter antenna, that allowed for the radar to get a precise lock. If the radar scintillated over the airframe, the guidance precision would be lost. Once the radar had a lock, data-link signals were sent to the airplane for guidance in reference to an ideal path in space. It was also precise enough that a random distribution of about +/- 8 inches was added (about +/- 10 feet fore/aft along the deck in the landing area) so that the F/A-18s wouldn't pound their hook points into the same spot every time, leading to excessive deck wear.
But ACLS, while guiding the airplane in space, couldn't measure the safety margin at the ramp. The back of the carrier moved up and down in high seas...and while the airplane was steady state, the ship moving up and down underneath that ideal path could create a situation of too little clearance (leading to a crash) or too much clearance (leading to a severe landing that would break airplanes).
On a Nimitz-class carrier, with a steady deck, that was trimmed level fore/aft and had no roll or roll trim, and when using the 3-wire as a target (this geometry gets complex as well...but most of the time, we used the 3-wire as a target for the optical landing system as well as the ACLS) the hook point clearance was 14.1 feet. 10 feet was the minimum for safety, which allowed for pilot error, and other factors.
So, once the deck started moving, the LSO had to take over from the automated systems. In particular, the OLS (Optical Landing System - or "Meatball", often called the "ball") could not compensate for rapid motion. The ball/OLS had tremendous adjust-ability in commanding a desired hook touchdown point; it compensated for aircraft type (since it was aimed at the pilot's eye, the difference in aircraft geometry had to be taken into account...in particular, the hook-eye distance was critical, as the lens was trying to target a specific hook touchdown point)
A brief note on glideslope geometry. There were four wires on Nimitz-class carriers. The new carriers will have three but that's another story, and the Nimitz class is representative of today's fleet. The first wire was about 175 feet from the ramp (back of the ship). Each subsequent wire was 40 feet farther. We generally used the 3-wire as the "target" and the ball/OLS was set to command a 235' touchdown point, half way between the 2 and the 3. That gave the pilot the best chance at catching a wire. Now, on a 3.5 glideslope (relative to the ship, the wind over the deck meant that the airplane was actually descending an about a 2.8 degree path through the air, but relative to the ship, it was 3.5 degrees), each foot of vertical deviation worked out to about 15 feet of horizontal deviation.
https://en.wikipedia.org/wiki/Arresting_gear
So, in order to catch the 3-wire (generally considered a good landing, though other factors were included in that assessment), the airplane's hook had to be +/- 15 INCHES from the commanded path. That translated to the +/- 20 feet that kept you touching down just after the 2 and just before the 3.
In order to catch ANY wire the airplane's hook had to be +/- 4 FEET from the ideal/commanded path. This is a big point: if you were more than 4 feet low, the LSO would "wave off" the airplane - remember that 10 foot minimum? - and the pilot would select full power, retract speedbrakes and go around for another try. If the airplane was 4 feet high, the hook would miss the last wire, and a "bolter" would result. The pilot would add full power, retract speedbrakes and have about 250-300 feet in which to get airborne again.
So, when the deck is moving up and down, and it's moving more than about 4 feet, we would rig what was known as MOVLAS (Manually Operated Visual Landing Aid System) in the place of the OLS/ball.
https://en.wikipedia.org/wiki/Optical_landing_system
MOVLAS would allow the LSO to directly control what the pilot saw for visual glideslope. This allowed the LSO to help the pilot transition from a space-stabilized path to a path that corresponded with the deck movement to get them within the 4 feet required for a safe landing.
I've seen the deck move +/- 20 feet. Forty feet of total ramp motion. This presented a challenge in getting the airplane to a safe landing window. Clearly, when the deck went up 20 feet, the airplane, on its space-stabilized path, would be below the ramp (with an impending crash). When the deck went down, the airplane was so high that it was unable to make a safe landing from the space-stabilized path...the sink rate required would break landing gear completely off, or overstress the airplane structure.
This is where the art of "waving" as an LSO came in. When the pilot transitioned from instruments to visual, at 3/4 of a mile, the LSO would present a stabilized picture, referencing the horizon. Then the LSO would begin to move the airplane up or down from that reference to get the airplane closer to where the deck was going to be as the airplane crossed the ramp.
The trust in the LSO had to be complete, as the pilot couldn't feel the ramp motion, or know which was the ship was moving, like the LSO could. When the platform on which you're standing is moving up and down 40 feet every several seconds...you feel it!
Within about ten seconds from touchdown, you would start manipulating the MOVLAS to get the airplane "in sync" with the deck...most of the time you could make it work...but if the deck was going to be at the top of a cycle, or at the bottom of the cycle, the clearances/geometry was simply unsafe and you would "wave off" the airplane...being careful to say "wave off, wave off" to get the instant pilot response and then adding "pitching deck" so that the pilot knew it wasn't their error.
At night, with pitching deck, the LSOs needed a horizon reference. So, we would throw marine flares into the wake of the carrier...but in really big seas, they would get covered by waves, so the only thing that could provide a reference would be a ship...and we would use the lights from that ship to determine the horizon, and from that, the safe/stabilized approach path. I'll never forget one night (big rolling seas in the Atlantic, leading to +/-20 feet) when the Captain of the Carrier called down to my LSO platform and asked, "Hey Astro, the Leyte Gulf (a cruiser that was in formation 3 miles aft of the carrier) wants to prosecute a contact (sonar, a submarine), do you still need him?" To which I replied, "Sir, I absolutely need him to keep station, I can't see the flares and I can't see the horizon!" The CO laughed and said, "That's what I thought, I'll tell to stay put until his ears bleed!"
As a LT, I was determining what the CO of a cruiser, a Captain, could do with his billion dollar warship... But I did need him there, I couldn't have kept safe the dozen or so airplanes that were still to land.
A normal boarding rate: clear, calm seas, steady deck, was generally above 90%. With an all Hornet airwing, I suspect that number is up over 95%. Tomcats, as I mentioned, were a handful...
On a dark night, with pitching deck, we would be lucky to get a 50% boarding rate...you just couldn't get everyone in sync with the deck to a degree that would keep them safe. And once in a while, you would have a pilot that wasn't responding quickly enough to the MOVLAS. You would have to wave them off early, because you can't keep them safe if they're not responding instantly.
We would always have tankers airborne in case an airplane boltered and ran low on gas. In pitching deck conditions, we would put an extra tanker airborne, and often had a tanker on 5 minute alert (crew manned and ready, airplane near the catapult, ready to launch on 5 minutes notice).
Finally, it always seemed to be cold & raining whenever I was waving pitching deck...adding just a bit more challenge (and some misery) to an already challenging situation...
Cheers,
Astro
"There always came that exquisite moment of human judgment when one man - a man standing alone on the remotest corner of the ship, lashed by foul wind and storm - had to decide that the jet roaring down upon him could make it. This solitary man had to judge the speed and height and the pitching of the deck and the wallowing of the sea and the oddities of this particular pilot and those additional imponderables that no man can explain. Then, at the last screaming second he had to make his decision and flash it to the pilot. He had only two choices. He could land the plane and risk the life of the pilot and the plane and the ship if he had judged wrong. Or he could wave-off and delay his decision until next time around. But he could defer his job to no one. It was his, and if he did judge wrong, carnage on the carrier deck could be fearful.”
— James Michener, The Bridges at Toko-Ri (1953)
