Mods

• Aviation Lights
• Squad (stock)

77 Industries:

Stock Heavy Transport Helicopters

One manual for all four types.

Azi20 Selene

Azi21 Hyperion

Azi22 Eos

Azi23 Helios

I’ve redesigned the Asura engine, made it 50% shorter but a whole lot more powerful. So I wanted to build new helicopters to see what I’ve learned in the past 5 months. For the first time I’ve built functional transports. The names are from Greek gods.

Basic description:

Classic configuration with single three-bladed main rotor. Simple tail with vertical and horizontal stabilizers, three Juno jet engines for yaw control. The tail rotor rotates but does not deliver thrust. All types have Wheesley turbofans to give them a nice forward speed.
All four types have the same engine, rotor, backbone and tail. The maximum gross weight for all types is 110t.

Main engine:

MK3 CRG-25 housing with 50 Juno blowers, MK1 crew cabin turbine shaft with 8 turbine blades. bearings are a combination of 10x landing gear and 10x steel plates. Max allowed operating speed: 31 rad/s. Economy mode toggle through action group.

Main rotor:

Three blades, three segments per blade. Blade angle: 3.96 degrees.
Normal operating speed: 250 - 300 rpm.

Stability control:

Stock automatic pilot with selectable presets (docking ports on top of the cockpit).
Six 2.5m reaction wheels behind the cockpit except Eos: twelve 2.5m reaction wheels underneath the backbone. Two out of three Juno’s on the tail can be toggled through action groups. One upright Juno on the tail can be toggled for extra pitch control. Vertical and horizontal stabilizers can be deployed to trim forward flight.

Description per type:

Azi20 Selene:

Sleek, long and fast, this transport doesn’t have much space but delivers cargo in style.Twin turbofans give it a top speed of 85m/s. It’s the lightest of the four. Absolute ceiling: 8600m.

Length: 44.2m.

Width: 12.2m.

Height: 10.8m.

Rotor diameter 24.7m.

Mass (tanks full): 80.743t.

Mass (empty): 52.2t.

Max fuel amount: 28.5t.

Parts: 228.

Azi21 Hyperion:

This huge helicopter beats the legendary Mil Mi-26 in both cargo space and lifting capacity. It’s a lot slower though. Also its range is tiny compared with the real thing. Top speed is around 55m/s and that’s without draggy cargo.
The cargo bay has a usable volume of 567m3. That’s comparable with the main deck of a 747-400 freighter! The Halo has a mere 151m3.
This one has no cargo bay door. Reason: only adds mass and helluvalot of drag in stock aero.

Length: 44.3m.

Width: 7.7m.

Height: 10.2m.

Rotor diameter 24.7m.

Mass (tanks full): 82.9t.

Mass (empty): 54.4t.

Max fuel amount: 28.5t.

Parts: 279.

Azi22 Eos:

A flying crane like the classic Sikorsky and Mil Mi-10. It’s the lightest and the fastest

Length: 44.4m.

Width: 11.0m.

Height: 12.8m.

Rotor diameter 24.7m.

Mass (tanks full): 73.7t.

Mass (empty): 50.1t.

Max fuel amount: 23.6t.

Parts: 254.

Azi23 Helios:

This one is based on the Selene, it’s a hybrid helicopter/airplane. Choose what you like, take off and land as an airplane or helicopter. It’s not fast but has an excellent range. Instead of two it has six turbofans and a max of 36.4t fuel.

All except the Azi23 Helios have 28.5t of fuel. The Helios has 36.4t of fuel.

General flight instructions:

• Flying a helicopter in KSP is in some ways like flying a real helicopter, in other ways it’s different. We don’t have cyclic/collective in stock KSP. We’re also unable to build it reliably due to the limitations (part size, mass, lack of proper materials).

• Dissymmetry of Lift is most pronounced in KSP because of the lack of a cyclic and the fact the blades are fixed. In real life the blades have hinges to compensate. You’ll encounter DoL when flying forward, the faster the more you’ll get. To counter it the turbine shaft has some freeplay to rotate it’s axis. Also the blades are somewhat flexible. One of the things you’ll start to notice is a tendency to roll. You can try to counter it using counter roll-input but it’s actually best to yaw, especially at higher speeds.

• Retreating blade stall. The evil brother of DoL. Quote: Retreating blade stall is a hazardous flight condition in helicopters and other rotary wing aircraft, where the rotor blade with the smaller resultant relative wind exceeds the critical angle. Any stall is due to an excessive angle of attack. If this happens to you: pray.

• Whatever you do, remember massive control inputs are disliked by these giants. These are not airplanes, they’re not really suitable for aerobatics. Often you’ll feel you’re fighting with it but it’s because you’re doing the right things at the wrong moment or the wrong things at the right moment. Primary control is through a big number of reaction wheels. Secondary control is using the jet engines on the tail and the control surfaces. If possible it’s best to use the stock autopilot as often as possible and fly using trim.

• Center of Mass and PTE. It’s in front of the engine and with a reason: to counter the pitching up torque when flying forward. This means all of my helicopters have a natural tendency to fly forward. To counter this, you can toggle the Pitch Torque Equalizer, a Juno on the tail pointing up, the toggle is action group 8. Default is ON when starting the engines. You can switch it off before taking off and see what happens.
  This is actually one of the most important controls, always make sure you know if the PTE is off or on.

• Crabbing: as mentioned before we don’t have a cyclic which means the anti-torque has a side-effect: helicopters in KSP tend to crawl sideways while trying to hover or during normal flight. There are three Juno’s on the tail. One is always on, the other two can be toggled with action groups 3 and 4. Default is ON when starting the engines. Experiment. You’ll notice a change in behaviour with every change in speed. Another very important flight control, always remember which are on or off. It could save the lives of your kerbals.

• These birds are actually easier to fly than a real helicopter in most cases. Hovering, that’s a different question. Using a keyboard it’s easy to use too much control input. Besides that, response is slow and sluggish due to all the forces in play and the enormous mass, 2.5 times that of a normal helicopter of the same size.

Changing altitude is a real problem because of Squad’s decision to use absurd slow spooling for all jet engines. And since we don’t have a collective, you’d be fighting your helicopter all the way.

Hovering can be made a lot easier using the Turbine Brake System. Yeah let’s give it a fancy name for something as simple as that.

The bearings are made of landing gears. All friction settings default to off. To use the TBS, select an element of the bearing and set the friction setting to a higher value, somewhere between 2 and 5. After that just use the brake key to directly slow down the rotor. It’s best to have a direct numerical VSI on a HUD to see the effect.

Explanation of the stock autopilot:

The standard SAS function of maintain attitude doesn’t work well because of the engine vibrations. I’ve used SAS but with a simple trick. If you take a look at the top of the cockpit you’ll see five mini docking ports. Counting from the nose the first is rotated 2 degrees forward, the second is vertical, the third rotated 1 degree backward, the fourth 3 degrees and the fifth 5 degrees. To enable the autopilot simply choose a preset by selecting control from here and choose Radial Out. This does a much better job at flying. Remember: pitch and yaw controls are switched and roll control is reversed i.e. to roll to the left you’d use A but to yaw to the right you’d use Q. The compass is useless this way, the direction the nose is pointing is seen at the bottom of the navball.

Taking off:

1. Decouple the shaft(s).

2. Switch on SAS.

Built in the SPH in KSP version 1.0.5.