Shergood Flight System

1 Core Features

• Independent cyclic, collective, throttle and anti-torque controls
• Force/torque based physics model
• Realism features can be enabled or disabled to adjust level of difficulty.
• Helicopter weight changes as fuel is burned.
• Main rotor torque (pedals must be used to compensate)
• Independent engine and rotor RPM
• True power-off autorotations
• Ground effect increases lift near surfaces (land, water, or prim)
• Translational lift increases lift with forward airspeed
• Translating tendency results in a "left skid low" look during hover.
• Vortex ring state danger exists when helicopter is mishandled
• Refueling system with fuel quantity control
• Working electrical system with rechargeable battery.
• Weight dependent performance (fuel and passengers)
• Paint kit system for user customizable painting
• Unique N-number and serial number assigned to each aircraft
• HOBBS meter tracks total time on aircraft
• Dust/water effects when hovering near a surface
• Animated hand and foot movements track moving cockpit controls
• Collision detection/crash system alerts on crashes
• Fully functioning dual controls
• Access control system: owner only, guest or registered pilots

2 Helicopter Flight Characteristics

2.1 TORQUE

In single main rotor helicopters, torque is produced by the main rotor whenever the helicopter is under power. In most aircraft, the main rotor turns counter-clockwise when viewed from above, resulting in the body of the helicopter having a tenancy to turn clockwise (to the right) the more power you use. As a result, the pilot must apply right pedal to compensate. This is particularly evident when pulling collective to lift into a hover which requires the most amount of power. Conversely, right pedal must be applied when reducing power/collective. A few aircraft (e.g., Russian and French) have main rotors that turn clockwise when viewed from above. In these aircraft, the effect is reversed and left pedal is needed to compensate as collective is increased.

In aircraft with tandem rotors such as the Chinook, or in aircraft with coaxial rotors such as the Hiller UH-4, the rotors are counter-rotating and thus torque is canceled.

2.2 GROUND EFFECT

Proximity to the ground (land, water, or over a prim) reduces the amount of power needed to hover. The effect increased the closer your are to the surface, and diminishes as you increase height over the surface. Hovering near a surface is referred to as an IGE (In Ground Effect) hover, and hovering away from a surface is referred to as an OGE (Out of Ground Effect) hover. A helicopter can maintain an IGE hover at higher weights and altitudes than it can an OGE hover. At some loadings and altitudes, you may not be able to maintain an OGE hover at all.

2.3 TRANSLATIONAL LIFT

When a helicopter is in a hover or at a low speed, airflow through the disk is at a right angle to the rotor plane, and the rotors must provide all induced airflow through the rotors. As airspeed is increased, some of the induced flow through the rotors begins to be provided by the forward speed of the helicopter. The net result of this is increased lift at no additional cost in power. The largest increase occurs at around 10 to 20 mph and is referred to as ETL (Effective Translational Lift). As an helicopter passes through ETL, it requires significantly less power to maintain altitude, and more power is available for climbs. This is also the reason that less power is required in cruise flight than for hovering. It is also part of the reason that a normal takeoff involves a short ground run to accelerate past ETL before climbing out.

2.4 TRANSLATING TENDENCY

The primary purpose of tail rotor is to counteract torque from the main rotors. However, a side effect of this is a slight sidewards force that would push the helicopter to the right if left uncorrected. This is referred to as "translating tendency". To compensate for this, the controls on the helicopter have been rigged so that there is a slight left tilt of the main rotor when the cyclic controls are centered. This left force from the main rotor balances the right force from the tail rotor. A side effect of this is that the left skid will hang slightly lower then the right one in a hover.

2.5 VORTEX RING STATE

Vortex ring state, sometimes called "settling with power", is a dangerous condition that can occur when a helicopter is descending into its own downwash. Essentially a vortex ring system engulfs the rotors and they fail to produce lift. Once in vortex ring state, increases in power in an attempt to slow the descent will only make the condition worse, thus actually increasing the descent rate. If the condition is allowed to develop too far, or you are too close to the ground, it may be impossible to recover. You are at danger for vortex ring state when all three of the the following conditions hold:

1. Descent rate greater than 300 feet/minute
2. Airspeed less than 30 mph
3. More than 50% power

If you have alerts turned on, your helicopter will alert you when you are in vortex ring state. To recover from vortex ring state, you should lower the collective and apply forward cyclic to regain airspeed. However, the best practice is to avoid it in the first place.

3 Basic Helicopter Flight Maneuvers

3.1 PICKUP TO HOVER

Picking up to a hover is performed by slowly raising the collective until the helicopter becomes light on the skids. Pedal should be applied to stop any rotation, and cyclic should be applied to stop any lateral or forward/back motion. Considerable left pedal may be required in the pick-up to counteract torque from the main rotor.

3.2 HOVERING

There are two types of hovering. In Ground Effect (IGE) hovering occurs in ground effect within a few meters of a surface (land, water, or a flat prim) and Out of Ground Effect (OGE) hovering occurs at altitude away from any surface. While hovering in general requires more power (collective) than other phases of flight, OGE hovering requires significantly more power than IGE hovering, and may be impossible depending on how heavily loaded the helicopter is. Cyclic inputs in a hover should be small and controlled taking into account delay between input and the reaction of the helicopter. Use collective to control hight. It is important to learn to anticipate the reaction of the helicopter in response to an input. Over-controlling is a common problem for the beginning helicopter pilot. Forward hover taxi is performed by a very slight forward positioning of the cyclic. In general all hover taxiing should be performed with no more than a dot-width of movement from the center on the cyclic control display.

3.3 SET DOWN FROM HOVER

Setting down from a hover essentially the reverse of a pickup. Slowly lower collective letting helicopter settle. As collective is lowed, right pedal may be necessary due to the reduction in torque.

3.4 NORMAL TAKEOFFS

Normal takeoffs should begin in a hover with an adequate obstacle free area ahead of the helicopter. From a hover, apply forward cyclic and allow helicopter to accelerate forward in ground effect. At about 30 mph, the helicopter will achieve ETL (Effective Translational Lift) allowing the helicopter to climb (see Section 8 for details on ETL). Some brief aft cyclic at 40 mph may be necessary. Control airspeed with forward cyclic to maintain a best climb airspeed of about 50 mph. Applying too much forward cyclic will reduce climb performance. Raise collective to increase rate of climb, but do not exceed the maximum manifold pressure of 39 inches (red line).

3.5 MAX PERFORMANCE TAKEOFFS

If takeoff is from a confined area, the max performance takeoff procedure can be used. Begin with helicopter on the ground and collective full down. Raise collective until manifold pressure is at 39 inches (red line) while applying slight forward cyclic to begin forward movement. When clear of the obstacle apply additional forward cyclic. Once ETL is reached at about 30 mph, continue climb as normal.

3.6 CRUISE

In cruise flight, use collective to control altitude, forward/back cyclic to control airspeed, and left/right cyclic for turns. Use the inclinometer (black ball) in the HUD or on console to help in coordinating turns. When using the inclinometer, pedal should be applied on the side to which the ball moves. Think "step on the ball". The VSI (Vertical Speed Indicator) can be used as a reference to help maintain a constant altitude. As with any helicopter, aggressive and abrupt control inputs should be avoided.

3.7 TURNS

Turns should be made primarily with the cyclic, using the inclinometer to maintain coordination with the pedals as described above. In very steep turns, it may be necessary to increase collective slightly in the turn.

3.8 NORMAL LANDINGS

Begin a normal landing by reducing air speed to bout 50 mph and lowering the collective to maintain an approximately 500 foot per minute descent. Choose a target spot for your landing, keeping that spot at approximately the same place on the window. As you approach your touchdown spot, slowly decrease airspeed with back cyclic, and descent rate with up collective. Maintain above 30 mph until just before touchdown to avoid vortex ring state. As you transition to a hover, you will need additional up collective and left pedal to compensate for the torque.

3.9 STEEP APPROACHES

A steep approach can be used when landing is to a confined area. Follow the same procedure as for a normal landing, but slow to 30 mph and maintain that speed through the descent.

3.10 AIR TAXI

An air taxi is used to move quickly from one point to another on an airport. Begin an air taxi like a normal takeoff, but lower collective slightly to maintain a height of 10 to 20 meters over the airport while pitching with cyclic for approximately 50 mph. To exit an air taxi and land, apply back cyclic, down collective and ride pedal as necessary. Then make a normal landing to hover.