My question is a little different than this similar one.
I was watching a movie where a helicopter landed on a moving ship’s helipad. As it came in to touch down, it very gently touched down, just as I’ve seen them do on the ground. But the ship was moving under it at, let’s say, 20 knots, and the copter seemed to be holding its position relative to the ship quite easily. Is the air supporting the copter somehow moving along with the ship? It’s easier to this than I thought? Or the whole thing was faked and the landing was on terra firma?
Leaving aside pitching and rolling (which to me seem like the much harder problems), landing on a moving platform is just like landing on a stationary platform with that much more wind.
Not particularly. The pilot just pushes forward on the cyclic control (the thing that makes the helicopter move forward through still air) to compensate for the apparent headwind.
Similar to what @Pork_Rind stated, If you disregard the pitching/bobbing of the deck, landing on a ship that’s moving at 20 knots with zero ambient wind is the same as landing at an airport with a 20-knot ambient wind.
After the pilot has attained nearly zero forward velocity with respect to the landing deck, it’s just a matter of reducing lift until the skids or wheels are supporting the craft, ar which point deck crew would chock or tie down the helo.
No doubt it requires skill, but so does hovering stably in place, which I’ve been told is the toughest helicopter piloting task to learn.
Also, there’s this system to help in the bad sea states.
In the Canadian Navy when a helo is being recovered, the helo hovers above the flight deck, a wand is used to discharge any static electricity, and the helo’s cable is connected to another cable from the flight deck (specifically from a helo haul-down system that uses to be called a “bear trap” (I don’t know if that term has been superseded)). Once connected, the helo is pulled in the last 10 feet (or something of that nature), slams to the deck and the bear trap claws slam shut against the cable.
Then the rotor blades are folded aft and the helo is pulled, by the bear trap, into the hangar.
in addition to the ship’s pitching and rolling complicating the recovery, the other significant one around a ship is that the wind field is pretty turbulent and varies a lot by height. For a typical destroyer, frigate, etc., with a helipad on the stern, the pad itself is much in the lee of the hangar just forward. But go straight up another 50 feet and it’s not. As well, the air passing that square hangar produces a bunch of swirling turbulence just behind it = right across the helipad.
All of which gives the pilot a harder control task.
As was just explained, for some services in all weather / sea states and for most services in shitty conditions, they do sort of a helicopter arrested landing. The helo can hover a few feet above the deck and even if, despite the pilot’s best efforts, it’s wandering at random 5 or maybe 10 feet fore/aft and left/right that’s close enough for the ship crew to connect the landing cable between helo & ship. Then the pilot pulls up a bit to put positive tension on the cable, the ship’s crew pushes the button and the helo is rapidly hauled down onto the deck and trapped in place all in one quick motion. If it wasn’t above the right spot before, it is now. Whether the deck is rolling or pitching is immaterial; all the landing gear will end up in contact in some sequence real quickly.
Yeah, this is basically what I was after. In the movie the helo just floated right down with great stability. Did not seem to be fighting the wind at all. So I’m guessing either it was faked, or it’s not that hard, or it was a good pilot.
In case anyone’s interested it’s the series 3 Body Problem on Netflix, episode 4 starting at 35:51.
There’s some interesting footage of helo landings on a carrier deck in the 1954 film The Bridges at Toko-Ri.
After plucking William Holden from the water two Sikorsky H-5s are seen landing consecutively, with the same marshaler sprinting to direct both. They made it look pretty routine and I believe it was actual Navy film from that era. Great movie if you can find it - sort of the Top Gun of the 1950s.
Since there have already been a few straight answers to the original post, this gives me a once-in-a-lifetime opportunity to post this pilot joke:
Three of the best things in life are a good landing, a good orgasm, and a good bowel movement. The night carrier landing gives you the opportunity to experience all three at the same time.
FWIW I have been on a few helicopters landing on seismic survey vessels where the helipad is on the front of the ship. The ships are moving at a reasonable clip and the helicopter was facing the ship, so it was flying backwards to land and just matched relative speed with the ship, obviously nothing behind us to crash into when going backwards.
The pilots were all ex Royal Navy or Air Force pilots.
Also numerous landings on rigs and drill ships which were stationary but could really heave in the delightful North Sea winters , and other than some hovering and finding the right moment to land all landed. I had several aborted landings and a trip somewhere else, but that was when the wind was blowing through the Derrick across the helideck so the air was very turbulent, and the rig was anchored or a platform so could not shift orientation to change that .
Oh and fog, but fog only ever seemed to stop the helicopters landing that were due to take me home.
Stupid question, but I assume the helicopters have brakes for the wheels just like airplanes? Do they have “parking brakes” too? Or is that one more piece of the pedals to hold down?
I’m remined too that the one helicopter for Seal Team Six crashed in bin Laden’s compound due to the rotor wash bouncing off the walls. They’d practiced in a mockup with frost fence simulating the walls, weren’t prepared fo the level of backwash in a tight space.
I imagine the wind conditions could be similarly interesting around all that ship superstructure. After all, it’s not just the direction of travel, in blustery conditions the wind can be gusty.
When landing a helicopter on US Navy vessels, there are diagrams with visually depicted wind envelops to guide the ship’s officers in selecting a course and speed that will ensure safe relative wind conditions. Although we do not have power over wind and sea, we do generally have power over which way the ship is traveling relative to them. So certain variables can be adjusted for the safety of flight operations.
Can’t necessarily do that with a fixed compound on land with high walls and an enclosed courtyard.
