Date: Mon, 12 Mar 2001
From: Mac Miller
To: Elizabeth Miller
Subject: Helicopter 101
I know you’ve been around helicopters before. When I say blade you know I mean one of the long things that spin above the helicopter and not the thing you bring to a knife fight. But I am unsure how vast your rotary knowledge is. Let me presume you want to know more. I will fill you with helicopter facts. When you can’t take one more thin wafer, I will tell you just one more small thing and we will be finished. First off, the spinning thing above the helicopter is the rotor. It has a rotor head, to which are attached the rotor blades. The blades are shaped like wings and when the rotor spins the blades produce lift. The rotor head is hinged to the rotor mast so that the rotor can tilt freely while the helicopter fuselage remains still. It’s like a fancy office chair. You can lean every which way but the chair legs stay put.
Holding the rotor to the mast is a very special nut called the Jesus nut. It screws on to the top of the mast. The Jesus nut has a particular shape and strength that insure it remains tight. If the Jesus nut loosens the rotor comes off and the pilot calls out the nut’s name as the helicopter falls like a brick. (Actually, informal surveys amongst pilot types show that most often the first words spoken after something breaks is “Oh, shit.” Subject matter for another story.) Various gadgets connect the blades to the pilot’s hands. To the left of her seat, slanting forward out of the floor, is the collective stick. When the pilot wants to go up she pulls up on the collective stick with her left hand. This adjusts the blades in a certain way and up the helicopter goes. Positioned vertically between her knees is the cyclic stick. When she wants to go left she uses her right hand to tilt the cyclic stick to the left. This adjusts the blades another way and the rotor tilts on its hinges to the left and flies that direction. Think frisbee. Since the Jesus nut is tight the fuselage is pulled along for the ride. If our pilot wants to go forward, she tilts the rotor forward. Go faster, tilt the rotor more. Slow down, tilt the rotor back.
Because we live in this universe and not another our pilot also must deal with Isaac Newton’s Third Law of Motion. When the rotor spins the fuselage also wants to spin, but in the opposite direction. And it will do so violently. To control this the helicopter designers add a second rotor. Some designers put it on top of the fuselage with the first rotor, some designers put it out back and tilt it vertically. The latter is the one we see the most—must be the cheapest—and it’s called a tail rotor. Our pilot controls the tail rotor with both her feet using pedals like those in a car. She pushes the left pedal with her left foot to pivot the fuselage left, pushes right for right. Push either pedal to the floor to spin like a top in that direction.
So let’s go fly. Our pilot wants to raise the helicopter off the ground and stop at a 10 foot high hover, stationary over a point on the ground. She pulls up on the collective stick to increase the lift from the rotor. Soon the helicopter starts to rise off the ground. Simultaneously she pushes a bit of left pedal for Isaac Newton’s sake. The helicopter will rise to some height, which our pilot adjusts to 10 feet with small collective stick movements. The direction she faces is controlled by pushing the appropriate pedal. If the helicopter drifts forward she moves the cyclic stick rearward a bit to counter the drift, if it drifts right moves the cyclic left, etc. When everything is perfectly balanced our pilot can quit moving the controls and the helicopter will stay motionless in a 10 foot hover.
This lasts for maybe a second. On a good day.
Helicopters are inherently unstable. Throw in the push of the invisible wind and they get worse. So our pilot starts to move her flight controls again, hands and feet together, coordinated and smoothly, precisely and timely. If she is doing a good job she will move the controls only 1/8 of an inch, constantly but only as needed if that makes sense. The helicopter will drift no more than a couple of inches in the air in any direction. If our pilot is not very proficient or if the wind is gusting she will move the controls an inch or two. The helicopter will drift a foot in any direction. If our pilot is just learning to hover she will move the controls half a foot and will not be able to keep the helicopter within a 50 foot circle. It is very humbling trying to learn to hover. But not impossible. During the ‘60s the Army taught ten thousand 19-year-olds how to do it. Lots of humble 50-year-olds out there today.
Now our pilot wants to go to a forest fire. She tilts the cyclic stick forward to begin forward flight, simultaneously lifts the collective stick to begin a climb, pushes left pedal for Isaac Newton’s sake, and tilts the cyclic stick left or right to turn toward the fire. The fire is 500 miles away so she climbs to 1000 feet above the ground (AGL), lets the helicopter accelerate to 120, and while continuing to fly the machine (no autopilot in these things!) she soaks in the view.
In her spare time she cross-checks her instruments, navigates via map and satellite GPS, looks for other aircraft in her airspace, tunes and monitors the aircraft radios and talks to other people on them, calculates her fuel usage and plans where her next stop will be. She can’t make the 500 miles in one jump. Her helicopter gets 3/4 mile per gallon and its fuel tanks hold only 420 gallons.
Hey, it’s a big helicopter. It has two gas turbine engines that produce 2500 horsepower, it weighs 10500 lbs, will carry another 11500 lbs of fuel and cargo on board, it is the size of a school bus, and it has a big, big Jesus nut. This is no Honda Civic.
Okay, you had enough yet? Absolutely stuffed with rotor facts? Then let me tell you just one more small thing. The name of the first helicopter pilot was Igor Sikorsky. Orville, Wilbur, and Igor. Names with a nice sounding roll to them, yes?
March 16, 2001
We had the helicopter parked in Grangeville, ID on fire standby when the chief pilot called. There was a special lift job for us. He needed our expertise on this one. Plus we were close to the job. Since the helicopter rents for a dollar a second that probably was the real reason. A small airplane had crashed in the Salmon river to the west of us. The pilot was unhurt. Our job was to lift the plane out of the river and sling it to the nearest airfield. There it could be repaired. OK, we said, piece of cake. What time do we show up?
We launched for the wreck the next morning with high confidence just as every batter thinks he will get a hit when he steps to the plate. What was Ted Williams failure rate in 1941? Fifty-six percent. We should have remembered that. First off we had a stronger headwind than wed planned so we saw right away we would burn extra fuel getting to the wreck.
We found the wreck right where the satellite GPS navigation screen said it would be (silicone sealant and GPS, the two things from the space program that make the NASA budget a bargain) but were told by our ground contact there that the load wasnt ready to fly yet. We would have to land. Luckily a little dirt airstrip sat close uphill from the wreck. We quickly landed there. The airstrip was cut along the side of the hill. The airstrip was so steep we were afraid our parked helicopter would roll downhill and into the river 200 feet below. These helicopters have little bitty parking brakes on their wheels. We had to park the helicopter pointed diagonally to the airstrip, like youd park a car in San Francisco, and then put rocks against the tires. They land airplanes here!
A guy came up the hill—I mean airstrip—to us (two pilots in our helicopter) and took us down to the river with his four wheeler ATV. The airplane was upside down half submerged in the water, relatively undamaged. The nose of the airplane was toward the shore, the fuselage angled out into the river.
This airplanes engine had lost power while the pilot was fighting a forest fire nearby and he put it down in the best place his glide took him. He was probably planning on stopping upright and hopping from plane to shore, keeping his shoes dry. Almost panned out. He may still have kept his shoes dry since, being upside down, they were out of the water.
Anyway, our guy showed us the way he had the plane rigged to be lifted. Thirty-foot long cables hooked to tail and nose would join about 30 feet above the middle of the fuselage when tight. This inverted V rigging would keep the fuselage level in flight for less drag and more speed for us. The ground crew had also attached 2×4 boards span wise along the wings to spoil the airflow over the wings and kill their lift. When youre hauling an airplane below your helicopter you dont want the plane to start flying on its own when you get into forward flight. Who knows where the thing will fly (like, into the helicopter?) or if it will be controllable. We carry the plane at the end of a 150 foot long line hanging from the belly of the helicopter. That makes for an effective pendulum. A flying load out of control can swing above the helicopter. That would be bad. So, the boards on the wings were a good thing to see.
Well, batter up. It was my turn to fly. We rode back up the hill to the helicopter, fired the thing up, and hovered over to the wreck. I held the helicopter steady at a 150 foot hover over the wreck. Our long line has a big hook on its lower end. I moved the hook within reach of the ground guy, who was standing on the belly of the wreck, surrounded by water. He grabbed the hook and hooked the airplane cables to it, leapt to shore, and I started to pull hard. Nothing moved. The wreck weighed a lot more than advertised. Well, its full of water, dummy.
Actually we had planned for that but there was so much water in the fuselage that it was simply too heavy for us to lift even partly out of the water to begin the draining. So I flipped the plane partially onto the shore. The ground guys climbed on the wreck and started removing body panels to open up the fuselage cavities full of water. And we went back to Grangeville for more fuel. Our original plan was out the window.
Plan B came into effect. Plan B was, well lets put on 300 lbs more fuel than before because of the headwind and tell the fuel truck driver to stay by the phone. Well call if we need him to drive somewhere. How do we call when were in the canyons of the Salmon river? Why, we use the Bat Phone. This thing is trick. It has cell phone/ satellite phone capability. It fits in your pocket. The battery lasts. We can call anywhere in the world from any place in the world. OK, there are three things that make the NASA budget a bargain.
We flew back to the wreck. No landing this time. I brought the longline straight over the ground guy. He slapped the rigging cables into the hook, jumped off the wreck, and yelled Clear! into his two-way radio. I pulled full power. Two thousand five hundred engine horsepower started gulping our limited fuel. The wreck wiggled a bit and then slowly floated a few feet into the air.. I eased out over the river. Immediately one wing lost its 2×4 board but I wasnt stopping. The Salmon River curves through a deep vertical canyon. We had steep walls in front of us to clear, and a gas guzzling thousand foot climb at maximum weight with an aluminum drag chute 150 feet below holding us back. The helicopter climbs best at 50 knots airspeed. I eased our airspeed upward, heading for 50, watching what the sling load would do. At 31 knots the airplane wing that had lost its board began to fly. The load started an escalating swing laterally while beginning to spin. The helicopter rocked side to side from the oscillation of the load. Another 10 seconds and the load would be out of control. I slowed down. At 25 knots the load stabilized but the helicopter quit climbing. So we had our rules set. Fly at 26-30 knots or dont go anywhere.
We grunted up the hill at 29 knots or so, getting whatever climb there was. Now and then a wind gust would hit the load and the no-board wing would start to fly again. Id have to slow down a moment, trying to time the wind gust, and then accelerate again before our climb was killed. I began wondering what other people did for a living. We finally topped the canyon wall ten minutes later, the load clearing the rim with 200 feet to spare. This would be our altitude for the next 13 miles of rolling terrain.
The other pilot and I settled back in our seats for the trip. This sling would be slooow. Bicycles would be passing us. We slowly ticked off the miles. We were plenty low and slow enough to see in detail the stuff in peoples back yards. Folks in the boondocks save everything.
Other than dodging the occasional car—you never fly over people or things with a load beneath you—the rest of the trip was relatively uneventful, if nerve racking. I gladly set the wreck down at the destination airstrip and made it back to Grangeville with our minimum fuel reserve still on board. Plan B had worked. Total bill to the customer—$9000 for 2.5 hours of flying. But, hey, the engine in the wreck was worth ten times that.
The customer was happy.