I’ve just turned on Whale Wars, and they have a Hughes/Schweizer 269-series helicopter. (I think it’s a 300C.) Jacques Cousteau had a Hughes 300C on Calypso. Many tuna boats have JetRangers.
Here’s what I’m wondering: Helicopter main rotors are pretty floppy when they’re not spinning. If you tried to support the airframe from the tips of non-spinning blades I think they may break. So I wonder how they keep them safe in rough seas? On the Bell with its teetering rotor system, it seems that oscillations can be confined more or less to one plane. But with fully-articulated systems such as on the Hughes/Schweizer, that seems more difficult. Not only would I worry about damage to the blades (not only from unwanted movement, but also by a large wave), it seems there would be quite a bit of stress put on the hub and hinges. Tying the blades down would prevent them from flexing up, but how do they keep them from flexing down? Some military helicopters have folding blades, but this isn’t an option on light helis.
In short, how do crews on these vessels protect the helicopters from damage?
On rough seas, the pilot drops a cable from his aircraft and a winch on the 'copter of the ship brings him to a firm, safe landing. Once aboard, the rotors are folded (so the are all on top of each other like one blade) and then tied down.
That’s on the military birds. The 300CB I flew didn’t have folding blades. I don’t recall Cousteau winching a heli down as the do in the Navy, so I suspect the light helis are only used in calm seas. What I was wondering about how they’re protected on the deck.
Tuckerfan: Not having flown off of a ship, I’d be concerned about anything that flexes a non-spinning rotor blade.
I was thinking that in a large wave the rotor blades could be flexed violently downward and then upward against the restraints. But I guess if it works, it works.
Just tie 'em down. Also tie the helicopter itself down. I’ve got not-quite 3,700 hours as a helicopter pilot, and some of that have been where the wind blows quite a lot. The thing to worry about with blades is not the downward force, it’s the oscillation that occurs when they’re allowed to flap up and down. Tie 'em down with a good bit of downward flex and the bounce doesn’t happen.
I use bungie cords to lock down the control surfaces on my plane (attaches the yoke to the pedals). I also tie the plane down so there’s some give to the rope. Since the helicopter blades have some flex to them it shouldn’t be a violent amount of stress hitting the rotor assembly all at once when the ship pitches in waves.
It is when the helo in that picture is involved. That’s the MH-68 Stingray, and its only purpose is to stop high speed drug smuggling vessels, or ‘go fasts’. The Stingray carries weapons and a gunner who will first fire warning shots across the bow of a fleeing boat. If the warning shots don’t work, the gunner will take out the engines with sniper rifle.
That’s the Canadian Navy-developed beartrap; do other Navies use that too? It’s only really necessary on smaller ships in heavy weather (imagine trying to land a seven tonne Sea King on a destroyer in ten metre swells, and you’ll guess why it was developed).
I have seen a helicopter on the deck of a large tanker that was lashed down as others have described: the rotors were individually flexed towards the deck and tied to stays. I’m pretty sure that the ship was not designed to have a helicopter aboard, however.
Surely if the rotor assembly can bear the force of the chopper itself when moving at 100+ mph, a bit of wobbling when the seas are rough should be no big deal?
Much of a rotor’s rigidity comes from its spinning. Sort of like a string with a nut on the end. When you’re not swinging it over your head, it’s limp. When you do swing it round and round it will stay horizontal. Since I’m not an aeronautical engineer and haven’t been aboard a ship with a helicopter on it, I thought they might be subject to shocks they would not experience in flight.
In regards to that show Whale Wars, what’s your opinion of the pilots reaction to the small damage it suffered during the Zodiac launching fiasco? It looked like a small bend, maybe 3/4" by 1/2", on the trailing edge of one rotor (not sure how far out on it). The rotors were aluminum and the pilot was worried about a crack forming.
Given that if he ever had to ditch at any distance from the ship he knew he would pretty much die from hypothermia (even if he suffered no injuries from ditching) I can imagine he was being extra extra cautious, but the damage didn’t look that serious to me.
And the pilot ultimately ignored it once he found it flew ok.
Personally I wouldn’t fly it if I had a choice. Airplane propeller blades are also made of aluminum. My dad bought a used Cessna once, and it lost about six inches from the end of one blade because of a nick from which a crack propagated. (Immediate shutdown ensued, followed by an emergency landing at MCAS El Toro.)
Now, helicopter blades are of different construction. Solid aluminum would be too heavy. I suspect that a ding in the trailing edge of the skin isn’t as serious as one in the leading edge of a prop; but rotor blades are constantly flapping up and down, being twisted longitudinally, being ‘stretched’ from the rotation, etc. It’s possible it can crack. I don’t know how a Hughes/Schweizer rotor blade is made. If the skin is a structural part of the blade, then any damage/defromity can be dangerous.
