AH-11 Dragonfly
by XLjedi
uploaded 2019-07-16
(updated 2023-03-12)
stock+DLC aircraft
#Coaxial #Compound #Helicopter #Jet #Helo

1.12.5 Updated Craft File

• Rotor blade pitch remapped for (1.8.0)
• Rotor blade pitch inverted for clockwise rotation (1.9.0)
• Landing lights automated with G key (1.9.1)
• Rotor now remains locked until engine staged to ON (1.10.0)
• Slight tweak to baseline aileron trim +/-2% for slight roll at speed (1.10.1)
• Max speed seems to have improved by 5 up to 110 m/s (1.10.1)
• Flight Tested and 1.12.5 Approved!

  • Type: SPH
  • Class: aircraft
  • Part Count: 51
  • Pure Stock
  • KSP: 1.12.5

Get the 256x160 flag!

Mk 5 Update

• The 1.9 upgrade introduced new blade controls - and I don’t bother with them
• I did not adjust the craft to take advantage of the new cyclic control features of 1.9
• Along with the new cyclic control feature, it looks like the lift vectors for clockwise are no longer inverted. So the 1.8 version of the craft had the upper and lower blades counteracting each other. To make it fly again, I just inverted the blade pitch control on the KAL-1000 to remap the lower blade.
• The craft seems to fly the same as it did before now, although I may tinker with this one again to see how the cyclic controls work. For now, it flies the same as it did before.
• I have tested versions of this craft to fly with cyclic and no reaction wheels. So far, I don’t much care for it.


While reaching for an almost lost candybar behind a snack machine, Bill makes an important discovery of long lost technical blueprints for some pretty nifty parts! Meanwhile, UT Corporate executives realize they don’t have a helicopter!

A stock aircraft called AH-11 Dragonfly. Built with 51 of the finest parts, its root part is Mark1Cockpit.

Built in the SPH in KSP version 1.12.5.

Mk 4 Update

• The 1.8 upgrade introduced new mapping for rotor blade pitch
• The function of Authority Limiter was changed and Deploy Angle was added for pitch control
• In 1.7.3 the range of motion was -150 to +150 and the new range is -22.5 to +22.5 or exactly 15% of the prior values
• The ECM (KAL-1000) was reprogrammed to use Deploy Angle and changing the values to be 15% of the previous values
• Any noticeable change to flight characteristics are now related to the changes in the flight/physics model
• I recommend trying this one with Caps Lock On/Off to see which you prefer

Mk 3 Update

• Relatively minor updates, but I liked em enough to keep them as my standard setup
• Added 2 forward spotlights for assistance while skimming the ground at night
• Installed a QBE probe core (hidden of course) attached to the crew cabin and made it the root part. This fixed the nav ball incorrectly reporting a 20 degree dive during level flight (due to the sloped cockpit). Now you just need to be careful to not takeoff without a kerbal on board! Now I can set the helo course to follow or fly to a target!
• Lastly, I find that I like more torque when I come in to land. So, I modified the torque curve to maintain more of that low end power on the low side of the throttle for hovers and landing. You’ll understand when you see the shape of the curve in the KAL.
• Adding the QBE probe core, and the 2 spotlights raised the part count up to 51
• I’m really enjoying the flexibility of the KAL-1000 letting me edit the Power/RPM curves to dial-in the flight characteristics!

Mk 2 Update

• Redesigned coaxial motor setup for more power. Available engine torque and RPMs have doubled!
• Unwanted yaw/roll has been engineered out of the airframe/engine design
• Aileron Trim Tabs are now neutral or zeroed out as the default position (due to the previous bullet)
• Completely remapped Engine Control Module (KAL-1000) Power Curves
• The throttle now includes blended power curves for: Torque, RPM, Collective Blade Pitch, and Jet Thrust
• Greatly improved vertical lift and much smoother and finer control during hover and landing
• Slightly improved range by increasing the liquid fuel capacity to 386 and decreasing oxidizer to 44
• Simplified startup sequence. Eliminated an unneeded engine engage/disengage step and deleted the key assignment.
• No change to part count!

The blueprint below has been updated for the changes to the key assignments and startup/shutdown sequence. However, you may have to refresh your browser to see the changes.

Flight Testing (video is temporarily down)

• This is actually a one hour tutorial on 1.7.3 advanced propeller/rotor design
• Includes a full explanation of how I used the KAL-1000 as an advanced Engine Control Module
• As well as a few other tips, tricks, and flight test observations that you might find interesting

The video is temporarily down and I will be posting a new and improved version; hopefully this weekend. I really need to correct a number of (OK, somewhat embarrassing) early misconceptions and explain all of the improvements I made to the craft. I realize now that some of the stuff I said was just flat-out wrong or even backwards! LOL …but after further evaluation and flight testing, I now know better!

Design Notes

• The most notable design feature of this craft is the mapping/blending of multiple power curves to the throttle with the KAL-1000 Robotics Controller used as an ECM (Engine Control Module). Power curves have been carefully developed so your throttle is able to effortlessly control both vertical lift and horizontal thrust during every aspect of flight. The ECM includes a blending of power curves for: Torque, RPM, Collective, and Jet Thrust. The combination of these blended curves results in a craft that can transition from vertical to horizontal flight mode simply by throttle position. The craft ascends and hovers in the 30-50% throttle range, and achieves max vertical lift in the 70-80% band. From 80% to 100% the throttle transitions to jet thrust and settles into a hover for high-speed horizontal flight and behaves more like a jet plane.

• For my flight control preferences, I do find that I need to blend RPM and Torque into the throttle for the best and smoothest performance across a full range of altitudes and vertical/horizontal modes of flight. I intend to use an ECM for all of my rotor and propeller driven craft going forward, and you really should take a look at how I’ve programmed the ECM for application in your own propeller and rotorcraft designs. The KAL-1000 is just awesome!

• The coaxial motor setup required that I attach each engine independently to the fuselage. If you take a look at how the top electric motor was attached with a hexagonal structure part, you’ll see what I mean. Additionally, I found that I needed to use the advanced tweakable features to auto-strut and set the top engine part up for rigid attachment. This is so the upper engine would not appear to magically separate and float above the lower engine when it generates vertical lift.

• You might notice that I added a small docking port as a cap for the top rotor engine. This was not merely a cosmetic preference, although it does look pretty good up there, and I may even slide it up slightly for situations where I might find a need to have that actually used to dock to the roof of a hangar in an aircraft carrier design. The actual real design purpose is to set the diameter of the upper engine rotor attachment area equivalent to the rotor attach area for the bottom engine. You’ll notice when comparing the upper and lower rotor diameters… they are now equal. So they produce equivalent thrust/torque and are able to accurately counteract yaw in the airframe/engine/rotor design.

• By setting the torque, RPMs, and engine size (power or force expressed in kN) as close to equivalent as possible, I am able to achieve the benefits of the counter-rotating coaxial design and we don’t see any unwanted yaw in one direction or another.

• You should beware of the advice of some who suggest you should always limit your engine size/power based on the minimum required to achieve some desired target RPM output. Rather, you should flight test your design to see if you have enough power to maintain your desired RPMs during all aspects of flight. For instance, you will see RPM drop during high-speed flight as your blades have to fight harder against the wind.

• Rotor RPMs have a significant impact on roll control at speed. The rotor is acting like a stabilizing gyro, and the higher the RPMs, the more difficult it will be to make a banked turn at speed. You’ll notice in my ECM mapping, as I increase jet thrust, I also decrease rotor RPM. So I can fly the craft like an airplane and I get much better roll control because I’m not fighting so much of the rotor gyro effect. At lower speeds, the higher RPMs make for a more stable and controllable hover for the same reasons.

• Try taking off and slowly increasing your throttle from the 30-50% this should be a hover for various low level altitudes. Then increase throttle more rapidly from 50-80% to see your max vertical climb capability. While your throttle is in the 70-80% range for max vertical ascent, punch the throttle to 100%. Watch how the blade pitch adjusts automatically down to 15 authority and settles you into a hover for that altitude while the jet thrust kicks in. Now your rotor is configured as a wing for forward flight. Cue the Airwoof soundtrack!

Thanks for downloading! Go try it out… and if you like the design, your up-votes do make me happy and are a great way to encourage posting another design. ;-D

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