Flying Bell 407

From Fly! II simulator's documentation by Terminal Reality Inc.
It might be interesting to read how to fly a helicopter. Just ignore all those "Press Ctrl-PgDn" etc.

1. Rotary-Wing Aerodynamics | 2. Cockpit Tour | 3. Let's Fly ! | 4. Getting Back Down


3. LET'S FLY !


It's very difficult to fly the Bell 407 without some form of tail rotor control (either a "twist" yaw axis on your joystick, or (much better) separate pedals. If you don't have either of these, the default keys for tail rotor control are [ins] and [delete] for left and right, respectively. If your keyboard is laid out with these keys above and below each other, rather than left and right, you may want to reconfigure them using the Options-->Keys and buttons~>Helicopter keys menus.

In its default configuration, Fly! II assigns the collective pitch lever to the throttle on your joystick (or a separate throttle if you're using one). In an actual helicopter, you add power by pulling up on the collective. Therefore, for maximum realism, you may want to use the Options~>Setup Axes... menu to "swap" the throttle's direction of motion, so that full forward is idle and fully back is maximum power.


Bell's startup checklist "flow" goes from a brief visit to the collective, up to the electrical switches in the ceiling, then down to the panel. Tap [Ctrl+down arrow] to see the collective. Check that you can move the twist-grip throttle all the way from OFF through FLY and back to OFF. (Keyboard shortcuts: [Ctrl+pg dn] for OFF, [Ctrl+pg up] for FLY. While you have the collective in view, check that the landing lights switch is OFF, so that full battery power will be available to the starter.

Now tap [Ctrl+up arrow] twice to move to the overhead panel. All switches should be OFF except HYD (hydraulic control boost) and the anti-collision light. Check that the rotor brake is released (handle up against the ceiling) and all circuit breakers are in. Now turn the BATT switch ON.

Tap [Ctrl+down arrow] to return to the main instrument panel, where all sorts of things should be happening. You should hear the low rotor RPM warning horn (cancel it if you like by pushing the horn mute button below the RPM warning light, which will be on). Within 3 seconds, a number of engine and FADEC caution lights will illuminate, and you'll hear the (different) engine out warning tone for a moment. A few seconds later, you'll hear it again, and the ENG OUT caution light will come on. Mute the horn once again.

If you haven't wasted any time getting down to this panel, you may also see the engine instruments sweep to the tops of their displays, then back down, while illuminating all segments in their LCD readouts, as part of their power-up self test. During this test, the Nr indicator (rotor needle in the dual tach) will go to 107%, and the Np (powerplant needle) will go to 100%. If you want to run this test later (with the engine running), just hold the LCD TEST button.

Now it's time to start the engine, which is much easier with FADEC than in past helicopters. In those, you had to hold a starter button, then manually twist the throttle open until the engine fires up, then carefully modulate it to keep the RPM accelerating while avoiding overtemperatures. In fact, that's still the way you'd start the 407 if you had a FADEC autostart failure. (If the FADEC fails altogether before takeoff, rather than just in its start mode, it's a no-fly "fuhgeddaboutit".

With FADEC, it's a lot easier. Make sure the collective is all the way down, and move the cyclic until the CYCLIC CENTERING caution light extinguishes. Go briefly to the overhead panel and turn on the two boost pump switches at the lower left of the circuit breaker panel; return to the main panel, check that the red-guarded fuel valve switch at the lower right is on, then verify that fuel pressure is showing (leftmost row of instruments, second one down, left display). As long as you're over on that side, verify that the FADEC is in AUTO mode, and press-to-test the rudder stop—it should go to the ENGAGED mode as long as you're holding the button.

Here we go, and the order is just the opposite from a manual start. First, rotate the throttle twist grip to IDLE. Then, momentarily move the starter switch on the collective head to the START position. (You have to do this within 60 seconds of moving the throttle to idle, or the system "times out." If it does, just roll the throttle to OFF, then back to IDLE, to reset the timer.)

From here on, the start cycle is automatic. Monitor the engine instruments as the engine spools up. If it goes over the first triangular red mark beyond the redline, or if the main rotor hasn't started to turn by the time you get to 25% Ng RPM, abort the start by rolling the throttle back to OFF.

In a normal start, however, things will spool up very nicely without further attention. At 50% Ng, the starter will disengage, and the START light will go out; at 60%, the ignition is no longer needed, and the AUTO RELIGHT light will go out. The engine should settle down at 63% Ng. Now you can go back to the overhead panel and turn on the flight instrument switches and the avionics master switch.

Since we don't have control feel in Fly! II, we can't really check what the helicopter feels like with the hydraulic control boost switched off, but we can still do the preliminary check and, later, verify that it still responds to the controls. Turn the HYD switch off and verify that the HYDRAULIC SYSTEM caution light illuminates; then turn it back on and verify that the light extinguishes. More important is the FADEC manual mode check: push the FADEC switch on the panel, verify that the MANUAL mode light illuminates, then make a slight adjustment to the throttle twist grip (use the mouse) and verify that the engine follows you. Return the throttle to idle and re-engage the automatic FADEC mode.

Almost ready to fly! Roll the throttle up to its FLY detent and wait for both Np and Nr to stabilize at 100%. Turn the HYD switch off and make some gentle control inputs on all three controls to verify that there's no uncommanded movement, and that you have control. (In Fly! II, you can see the edge of the rotor disk move in the forward view as you do this.) Turn the HYD switch back on.


The first thing we're going to do is simply lift off to a normal hover (with the skids 4 to 6 feet off the ground.) Look straight ahead out the windshield (not at the ground right in front of you) and slowly start raising the collective. You'll see the torque begin to increase.

Before the helicopter even begins to lift off, it'll get light on its skids, and it may begin to turn to the right. Gently feed in left pedal until it stops trying to turn; then, as you gradually continue to add collective, add left pedal at the same rate. When you've reached sufficient power, the helicopter will lift off. Immediately "freeze" the collective; the helicopter will probably rise to just about the right hover height pretty much by itself.


Why does it do this? Because when it's hovering near the ground (called in ground effect), the helicopter in effect "stuffs" a cushion of air between itself and the surface; this effect is perceptible up to about half the rotor span above the ground. It would take much more power to hover out of ground effect, which is why helicopter performance charts include both "hover in ground effect" (HIGE) and "hover out of ground effect" (HOGE) listings. You'll notice that for a given temperature and gross weight, the helicopter can HIGE at much higher altitudes than it can HOGE (or, for the same altitude, it can HIGE on a much warmer day than it can HOGE). On this particular liftoff, by time you've pulled in enough collective to lift off, you probably have enough to hover a couple of feet off the ground, so the helicopter can seek its own balance between available power and the effect of the ground cushion.

If you've set the various helicopter effects to "realistic" in the Options~>Realism-->Helicopter... menu, you'll probably also notice that you're drifting to the right, and that it takes a little left cyclic pressure to stay over one spot.

This is an effect of the antitorque rotor. Remember, as the rotor turns to the left (from your cockpit viewpoint), the whole helicopter is trying to turn to the right; that's why you added left pedal as you pulled collective. The tail rotor is pushing the tail to the right to counteract this—but in doing that, it tends to push the whole helicopter to the right as well. Watch an American helicopter in the hover, and you'll notice that its roll attitude is very slightly left-skid-down. In the 407 this effect is quite small, since the rotor mast is installed with a slight built-in left tilt, but it's still perceptible.

Try to be as gentle as possible on the controls—a helicopter (particularly one with hydraulic control boost like the 407) is flown with pressures, not movements. In the real helicopter, you should hardly see the cyclic move at all. In fact, if you watch a good, smooth helicopter pilot at work, it doesn't look as he or she is flying at all, but rather very slowly and gently playing some sort of exotic musical instrument.

For the moment, just try to stay at least near, if over, one particular spot. A stable hover is probably the most difficult thing to learn at first; it can be taught to some extent, but then it has to be practiced. The trick is to make, and then remove, very small, smooth corrections; about half a second before you realize that you need them! (A good exercise is the old trick of trying to balance a broom vertically above your hand.) It is also helpful, as mentioned above, not to look at the ground right in front of the helicopter, but rather out toward the horizon.

It can be frustrating, but also very gratifying. It's very common for the final leap to competence to come very suddenly—you'll spend hours thrashing around, with sweat pouring down your face (and remember, you can't let go of the controls to wipe your eyes!)—then, from one moment to the next, "the nickel will drop" and the helicopter will suddenly become stable.


Once you have the helicopter reined into a stable hover, try a couple of pedal turns: apply a small amount of pedal in the desired direction to slowly turn the helicopter. You may notice that a left pedal turn makes the helicopter sink just a bit, while a right one may make it rise. This is because a left turn requires more blade pitch from the tail rotor, and hence more power, which it takes away from the main rotor; a right one requires less. With practice, you'll make the almost infinitesimal collective correction without even thinking about it.

In fact, not thinking is the key to successful hovering (and, to a lesser extent, helicopter flying altogether). Not that I'm suggesting that you "dumb down." It's just that will all the controls affecting not only the helicopter, but each other, and all the sensory cues coming in at once, no one can think fast enough to handle it all. You need to practice until you make and remove the myriad control corrections on a subconscious level—sort of like rubbing your belly and patting your head, writ large. It may be that the reason it's easier to hover while looking at the horizon is that you get your visual cues from peripheral vision, which is processed subconsciously, rather than staring directly at a target and thinking about it.


Now let's try moving slowly around the immediate area—and by that, I mean not much more than walking speed. Why do I emphasize slowness?

Because we still want to make this a hovering maneuver, which means we don't want to "fall off' the invisible ground cushion. Move a bit too fast, and the downwash of air through the rotor can't replenish the cushion fast enough. Move faster yet, and we'll start encountering translational lift before we're quite ready.

To start moving, apply very gentle pressure to the cyclic in the desired direction; as soon as the helicopter starts to move, take out at least half of what you just put in. To slow down, use gentle cyclic pressure opposite the direction of movement.

Moving forward is easy. Moving sideways is a bit less so; because it has "tailfeathers," the helicopter will want to point its nose in the direction it's moving, so you'll need just a bit of opposite pedal. Moving backward is hardest, because the tailfeathers want to spin the helicopter around; you'll need to pay close attention, using either pedal as necessary. Real-world helicopter students spend hours hovering along taxiway lines and airport markings for practice.


Let's end this segment by setting the helicopter back on the ground. Get back to a stationary hover (or as close to one as you can manage), pick an object out ahead to look at, and begin slowly lowering the collective. Remember, as you reduce power, you'll have to apply right pedal to keep the helicopter pointed in the same direction. If you're moving over the ground at all, make sure it's forward: the helicopter can actually "run on" to its skids quite nicely, but is likely to fall over if there's any sideways component.

This is a great way to demonstrate the ground cushion, too. If you start from, say, a 6-foot hover, then make only a tiny collective reduction, the helicopter will just settle a couple of feet, then stop descending—you've gotten down to where the ground cushion is thicker. It'll actually take a very slow, but continuous, downward motion of the collective to land the helicopter—the feeling is almost that you're pushing it onto the ground. Once the skids touch, smoothly lower the collective all the way to the bottom.


It may seem paradoxical to introduce an autorotation this early in your learning process, but there are some good reasons. One, of course, is that the helicopter doesn't know or care how much or little experience you have; it may choose to shut down, for its own reasons, anytime. Another is that a hovering autorotation is pretty easy, at least compared to some others you'll encounter.

A final one goes back to my own training, these many years ago. In those days, my instructor had found a loophole in the FAA regs stating that a student pilot could fly a helicopter alone, even before any official endorsement for solo, as long as the aircraft was "tethered to the ground." The local FAA office's interpretation of "tether" was any physical connection, no matter how flimsy, between the helicopter and the ground, so once I'd mastered (or, more accurately, managed) a halfway decent hover and could perform "safe, if not elegant" hovering autorotations, my little piston-powered helicopter was equipped with an old Dodge brake drum, tied to one skid by a 10-foot length of parachute cord. "As long as you don't pick up that brake drum, you're legal," I was told, "now get out there and practice." I spent hours practicing hover maneuvers and chugging along the taxiways of our big old WWII training field in the midwest; by the time my instructors decided it was time to continue my training, that brake drum was worn down to a thin, gleaming crescent. It's still a great way to practice.

Let's try a couple. This is a good time to enlist the help of a friend, since you'll "run out of hands" otherwise. Lift off into a normal hover, and when everything is stable, have your friend cut the engine, either by turning off the fuel valve or by hitting [Ctrl+pg dn].

Two things will happen: the helicopter will settle, and it'll yaw—fairly hard—to the left. Why the yaw? Because the tail rotor is still trying to compensate for all the torque that's suddenly not there anymore. Smoothly apply right pedal to stop the rotation and simultaneously smoothly raise the collective to cushion the touchdown.


Obviously, as soon as the engine quit, the main rotor started to slow down (although you were probably too busy to watch the tach). How fast it slows down depends on a number of factors, but a significant one is how much energy is stored in the rotor system as inertia.

A high-inertia rotor system is one that's quite heavy, often with long blades—in fact, in some helicopters, additional weight in the form of chunks of depleted uranium is added to the blade tips. High-inertia rotors tend to maintain their speed longer after an engine failure. The 407's predecessor, the LongRanger, had a fairly high-inertia rotor; in a hovering autorotation from a skid height of a couple of feet, if you just chopped the throttle, kept the helicopter straight with the pedals, and did nothing at all with the collective, it would sit down pretty firmly...but not hard enough to break anything. The JetRanger's big brother, the Huey, had an even higher-inertia rotor system. I've seen experienced military pilots do a complete autorotation from a couple of thousand feet in the air, set the helicopter down gently, then pick it up again and do a pedal turn, before those big blades finally ran out of oomph.

The downsides of high-inertia rotor systems is that they're less responsive in the air, and they're heavy—weight that might otherwise go to payload.

Low-inertia rotor systems, on the other hand, are light, responsive, and efficient. They offer crisp handling and excellent control—but require a bit more proficiency on the part of their pilots. Specifically, they'll "lose turns" faster after an engine failure (although, as we'll see shortly, they can also regain them faster). The 407's four-blade composite rotor is classed as a low-inertia system.


With the beginnings of a handle on the hover, let's finally get the 407 up into the air and going somewhere. Lift off into a normal hover as before, and turn the helicopter in the direction in which you want to depart.

Now, apply gentle cyclic pressure to start moving in that direction. As you get to about 15 knots, you'll feel the helicopter settle a bit—you've "flown off the ground cushion." Depending on your hover height when you started, you may need to add a little collective; don't forget to coordinate with the pedals.

At around 20 to 25 knots, you'll feel something different. The helicopter will feel like it wants to climb (it does!), and it'll also feel as if it wants to roll to the left (it does!).

You've entered translational lift, the condition in which the rotor blades are affected not only by their rotation, but by the forward speed of the helicopter as a whole. As we discussed earlier, the forward-going (or advancing) blades are exposed to a higher airspeed than the aft-going (or retreating) blades. The faster you fly, the more right cyclic pressure it'll take.

In forward flight, you'll find the helicopter much more stable than in the hover; in fact, it behaves more like an airplane. Use left and right cyclic pressure to roll in and out of banked turns, just like an airplane; use forward and aft pressure to control your speed. To climb or descend, adjust the collective (and, of course, the pedals). As in an airplane, for a given power setting you can fly level at one particular airspeed, descend at a higher one, or climb at a lower one, so once again the cyclic and collective have to be used interactively.

1. Rotary-Wing Aerodynamics | 2. Cockpit Tour | 3. Let's Fly ! | 4. Getting Back Down

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