VSKYLABS 'Contraventus'

The VSKYLABS 'Contraventus' Prototype

A new VSKYLABS scientific project for X-Plane flight simulator

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For X-Plane 11 and X-Plane 10.51
Two aircraft files included
Current version is v001b

Explore the fascinating and challenging world of precision flight in an electric powered, experimental aircraft. It is a robust, highly equipped, electric powered prototype design which was inspired by the MIT 'Daedalus 88' (the human powered, record breaking aircraft) design.

Development notices:
  1. Current version: VSKYLABS Contra-Ventus XP11-v001b + XP10.51-v001b

// The 'Contraventus' User Manual //


The design concept of the VSKYLABS 'Contraventus' prototype is to experiment and research the practical use of electric power coupled with wind energy utilization for 24 hours battery cells charging capabilities. The 'Contraventus' is a concept demonstrator and educational tool for experiencing some of the fascinating aspects of aerodynamics and flight envelope limitations.

The idea of the 'Contraventus' operation is to drain (consume) the operating battery during an initial climb out to ~5,500 feet QNH, and then recharge it completely while performing an ultra shallow glide, utilizing airflow (forward motion of the aircraft and wind milling). In a series of climb outs and charging-descends, the 'Contraventus' can be flown and recharge during day and night time. Its superb design as an efficient sailplane makes these climb-outs to work like climbing steps for reaching its cruise altitude (the 'Contraventus' is not a pressurized aircraft therefore it is limited by the physiological aspects of a human pilot).

The 'Contraventus' cruise altitude is derived from its electric motor and propeller's maximum RPM. As the aircraft climbs to high altitudes, the actual 100% RPM could be achieved easily in a lower power setting (because the atmosphere is getting thinner), meaning that in a certain altitude, operating the motor at 100% will not generate sufficient thrust within its operation limitations, and the operational ceiling altitude will be reached.

The 'Contraventus' features automatic solar cells, mainly for research purposes (at the moment), as the project is focusing on utilizing the aircraft potential/wind energy for recharge.

This aircraft design was focused on simplicity in operation, so you can get it flying quite easily and start exploring the fascinating equations of potential, wind and power management, as well as flight planning and any other considerations of your own.

This aircraft will squeeze out the aviator skills of endurance flying, precision gliding, aircraft potential management, electric power management and weather flying.

Aircraft Power/Electrical System:

A Single 10hp electric brushless motor that is being operated by drawing current from a 300AH Battery. By definition, the 'Contraventus' concept is challenged by using a low battery capacity specifications.

A three blade high-pitch propeller is attached to the motor in a direct-drive mechanism. The electric motor differs from a conventional, reciprocating engine in several aspects. One interesting aspect is the fact that the electric motor is not an "air-breathing" engine, and does not need oxygen for its operation. In a reciprocating engine, the mixture of fuel/air should be managed. In the electric motor there is only a "throttle" (similar to a jet/turbo-prop engine), and cooling the motor in high altitudes is a challenge. While climbing with the 'Contraventus', you will notice that for a given throttle settings, the propeller's RPM will get higher as the altitude is getting higher. It was set with 650 RPM as the maximum RPM of the system. You will notice that in sea-level, in full throttle, you will get only ~80% RPM, and in approximately 10,000 feet QNH, a full-throttle setting will get you to 100% RPM, therefore you have reached the altitude limitation for the motor/propeller.

The electric motor is connected to a generator and acts as a 3 blade wind-powered charger for the battery. The charging times and efficiency are supposed only to be plausible, in terms of electrical engineering, and the system was simplified in order to make the flying experience and potential management task and understanding straight forward and educational. The generator system will charge the battery above 15% RPM. However, descend rate is also an important factor and it should be managed to allow a good RPM vs sink rate ratio.

Landing Gears

The 'Contraventus' has four fixed wheels mounted underneath the fuselage, with no steering. The aircraft is designed to be launched in calm weather. Take off is actually a "launch"; into the wind, full power, and the aircraft is airborne almost instantly. In real life, launching would be made with ground personnel assistance at the wing-tips.

You will notice that the 'Contraventus' is quite stiff - there are no complex suspension systems for the landing gears. It should not be taxied on unpaved terrain - only paved runways.

Aircraft Controls:

The cockpit features only one control-yoke, for controlling pitch and yaw. There are an electrically operated descent split-spoilers that are activated by a toggle switch in the cockpit (A-BRK). The spoilers are for use when descending for landing (rather than commencing a shallow charging-descent), and it allows the aircraft to develop higher sink-rate while maintaining within its Vne limitations. Also use for rapid-descent in case of emergency. 

The aircraft consists these control surfaces:
  1. All moving horizontal stabilizer (elevator).
  2. All moving vertical stabilizer (rudder).
  3. Split-spoilers (air-brakes).
Rapid-Descent Split-Spoilers
Use either Rudder or Aileron axis in your joystick to control the Rudder:
In X-Plane, for flight-simulation-pilot-convenience, the rudder is coupled with ailerons (roll) control so you can move the rudder by using your pedals or other method of rudder control in your joystick (twist or whatever) or, you can move the stick as if you are operating your ailerons to induce roll. The flight model will have your inputs (roll or yaw control from your joystick/pedals), and will use it to move the rudder of the aircraft. So, basically it is 100% rudder controlled aircraft, with dual input from your joystick. No setup is required in X-Plane joystick menu.

Cockpit Layout

The cockpit of the 'Contraventus' is straight forward and useful. It has an artificial horizon (on the smartphone screen) and a GPS with a moving map system, but it is not designed to fly IFR.

Cockpit click-zones:
  1. Switches (left, main, right panels).
  2. GPS fold-up holder: click to fold or unfold it.
  3. Smartphone screen: click to toggle recommended field of view setup.

Fold-up GPS system:
The fold-up GPS is located above and ahead of the pilot's head, and you can just click on it to fold or unfold it (when folded up, there is maximum forward visibility).


Aircraft / Mission Operations

In General:
As part of its design concept, the 'Contraventus' is designed with minimum specs at all aspects (with the minimum possible configuration in mind). There are no "extras" and every phase of the flight should be performed with precision, in order to succeed.

Winds and Weather:
One of the base-line considerations when flying the 'Contraventus' is wind strength and direction. This research aircraft is very limited in ground operations on windy conditions, and is a slow-flyer (~30 knots at powered-climb or charging-descent phases) Meaning that you will have to plan your flight route with a close look at the weather, in order to have a successful landing in a pre-defined landing spot. Special care would be taken when flying the aircraft to remote areas such as deserts or over sea. You might find yourself unable to get back to your planned landing spot because of bad wind considerations.

Preferred weather conditions should be:
  1. Launch: Calm winds (recommended below 5 knots).
  2. Flight: Calm to moderate wind layers in the operational flight altitudes.
  3. Flying through clouds is prohibited.
  4. Flying through rain is not recommended in the 'Contraventus' prototype 001 because of its electric motor type and configuration. Future models of the 'Contraventus' will have all-weather capabilities (with some limitations).
Ground Operations:
The 'Contraventus' is a "super-glider". Because of its enormous wingspan and its light weight, there are limitations regarding the ground operations and launch conditions; at ground level winds of over 5 knots is would be very tricky to hold it stable, and head-wind launches are recommended. In real life, these kind of research airplanes are brought to the takeoff position with external assistance such as ground personnel who are holding its wingtips upon launch. The 'Contraventus' is a research powered glider and it cannot be taxied, just like a conventional glider in X-Plane (and in life...). Luckily, a very short (but wide clean) launching area is needed to set it up safely into the air.

Getting Airborne:
keep in mind that you will have to launch the 'Contraventus' in calm weather. Launch is straight forward: Apply full power and within 3-4 seconds the 'Contraventus' will get to its flying speed. Gently pull the stick and once airborne and above 25 knots, let go of the stick and let the aircraft a few seconds to stabilize in a full-power-climb attitude. Remember that it will want to turn into the wind, so plan ahead and "keep flying the airplane". Once the airplane is stabled in a ~500 feet/min climb, you are good, having a successful launch.

If you insist, you can launch it in windy conditions: apply full power and let it to be "sucked-up" into the will need nerves of steel though...

Pitch-Trim management (not needed!):
No need for any trim setup (pitch trim), as the aircraft is designed with pitch-trim setting in mind. The aircraft is already trimmed (pitch trim) to all flight phases, including takeoff, powered-climb, charging-descent, long-range-cruise, rapid descent and landing.

The 'Contraventus' does not features trim gauges. If you had changed the pitch-trim during flight, and would like to set it back to its designed, normal settings, simply follow on of this simple procedures:

Set up a natural-pitch-trim during descent:
  1. Set the aircraft power to idle.
  2. Wait for the aircraft to stabilize in a glide.
  3. Gently adjust the pitch-trim so it will result in a 30 knots IAS glide.

Set up a natural-pitch-trim during powered-climb:
  1. Set the aircraft power to Maximum-Power.
  2. Wait for the aircraft to stabilize in the powered-climb.
  3. Gently adjust the pitch-trim so it will result in a 32 knots IAS glide.
Powered climb should be executed in 100% propeller RPM and ~32 knots IAS. Note that as you go higher, propeller's RPM will tend to go faster also, in a given power setting, because of the thinner air. You will have to monitor your RPM gauge and use the power within the 100% limitation (in the RPM gauge there is a red arc just after the 100% scale. You can operate the electric motor within this red arc during climbs).

The 'Contraventus' concept of operation is to perform Three to four climb-out and descent phases before reaching the cruising altitude, which is 8,000-10,000 feet QNH. Best rate of climb is achieved while flying in wing-level attitude (not in a turn), so try to maintain your flight path in straight lines. Best (initial) rate of climb is achieved when flying at ~32 knots (IAS). Rate of climb should be ~500 feet per minute.

Remember...the aircraft is already trimmed (pitch-trim).

Monitoring Airspeed and Heading:
In the Airspeed gauge you will notice an arc with four sections:
  1. White: 15-30 knots - Minimum operation speed.
  2. Green: 30-45 knots - Safe operation speed. 
  3. Orange: 45-55 knots - Maximum operation speed.
  4. Red: 55-60 knots - Vne zone.
The 'Contraventus' is designed and trimmed to fly hands-off (although it doesn't features an autopilot system...yet...), so during the powered climb, the aircraft will set itself up to the correct attitude, airspeed and climbing rate. In calm weather it will hardly require yaw correction, only small corrections to keep the wings level. Note that because of the large wingspan and its low airspeed, even a slight bank will cause the aircraft to turn, so keep an eye on the desired heading.

Power Management:
During the climb, the 'Contraventus' will drain the batteries out. Use the 'Battery Level' and 'Battery Charge' gauges to monitor your electrical power consumption. The 'Contraventus' is also equipped with active solar panels that helps to reduce the descent cycle times. During the initial climb-outs and charging-descents to cruise altitude, the solar panels contribution to charging the batteries is not significant because of the extensive power consumption.

The solar panels are an experimental feature in the 'Contraventus' prototype no.001, and it will have a greater role in future development. 

Switches and Instruments

Battery Level:
The 'Battery Level' gauge is set to deliver "Empty/Full" status, for easy readings (you will not have to handle Voltage nor Amps). The needle in this gauge will slowly move from Full to Empty as you are drawing power from the battery for the climbing phase, and will slowly show increase in capacity when recharging.

Battery Charge:
The 'Battery Charge' gauge is set as "Plus" or "Minus" areas. The needle will be in the "Plus" area during normal operation of the aircraft; at all times. If the needle is staying in the "Minus" area, then you have a charging problem. This indication might occur also during a very slow flight (below 20 knots), because of low-rotation speed of the propeller.

Once fully charged, the Battery Charge indicator will indicate "Minus", meaning that there is no charging. In this condition, the spinning propeller will produce the electricity that is needed to operate the low-consumption systems such as lights and avionics. 

Generator Charge Switch:
Make sure that the "Gen Charge" switch is set to "on" for the motor to be used as generator for charging the batteries while windmilling.

Bat Switch, R1 and R2 switches:
These are practically the "on/off" switches for the electric system. Set the R1 and R2 switches to "on" in order to feed the electric motor power bus for powered flight.

GPS (X-Plane 530 / Garmin 530):
One of the most important avionics in the 'Contraventus' is the portable (fold-up) GPS system. If you are seriously into flight planning and flight management, you will find all what you need in the X-Plane 530 GPS. Mastering the GPS is a challenging but a very rewarding task, and there are a few manuals around that can be found and used.

Here are links to a series of YouTube videos that demonstrates, step-by-step, how to use this GPS system. These videos are not related to VSKYLABS, I've only posted these links that I found useful):

How to use the Garmin 530 GPS in X Plane10 - Tutorial Part 1

Powered Climb Practical Aspects:
  1. The aircraft is designed and trimmed to saddle into a hands-off 100% powered climb (pitch aspect) of about  ~32 knots IAS (in calm weather). Keep in mind to plan your climbing route in straight lines and execute needed turns only, to obtain maximum rate of climb.
  2. In a powered climb-out, the aircraft will climb at full power, as the batteries will drain (in my test flights I was able to execute three climb cycles to cruise altitude with only one full-drainage of the battery, in only one of the cycles, so there is no deed to fully drain it in all of the powered climbs). No changes in pitch-trim are needed for the powered climb phases. The 'Contraventus' is already trimmed and ready to go.
  3. Climb performance is ~500 feet per minute at full power and ~32 knots IAS. Note that at sea level you will not get 100% RPM when using full-power. Its fine and it's as it should be; RPM will get higher as climbing altitude will get higher.
Charging-Descent Practical Aspects:
    1. The aircraft is designed and trimmed to saddle down into a hands-off glide (pitch aspect) of about  ~30 knots IAS (in calm weather). Keep in mind to plan your descent route in straight lines and execute needed turns only, to obtain a minimum descent rate.
    2. Once reaching the top-of-climb point (in each cycle), the 'Contraventus' should start the Charging-Descent phase.
    3. Charging-descent is done simply by setting the throttle to Idle (which is practically "off"), and letting the aircraft to saddle down in a stabilized, shallow glide. This is the flight condition in which the 'Contraventus' was designed for; sustained, shallow glide. No changes in pitch-trim are needed for the charging-descent phases. The 'Contraventus' is already trimmed and ready to go.
    4. Descent rate will be ~150 to 200 feet per minute at indicated airspeed of ~30 knots (these numbers will slightly increase as you will reach the cruising altitude of 8,000 - 10,000 feet QNH).
    5. As the aircraft will glide, you will notice that the 'Battery Level' gauge will slowly show the increase of capacity (as long as the 'Battery Charge' is indicating "Plus").
    6. In an unpowered glide, propeller windmilling RPM will vary in respect to the gliding altitude: lower RPM at lower altitudes. This might have a slightly effect on charging time at the higher altitudes, because the propeller will windmill faster in a few percents while cycling between 10,000 and 8,000 feet and cruise altitude. 
    7. During the powered-climbs and charging descents it is important to turn off unneeded lights. If turned on - the charging descent will not be optimal. Once at cruise altitude, external/internal lights can be turned on, if needed. 
    You can try out and experiment your own cycles, but here is a suggested flight profile to reach cruising altitude:
    1. Aircraft launch (profile for launching from sea-level)
    2. Initial powered climb-out at Maximum Power (85% RPM), 32 knots IAS to 4,500 feet QNH (25% remaining on the Battery Level indicator).
    3. Initial charging-descent at idle (windmilling RPM ~40%) / ~30 knots IAS to altitude of 2,500 feet QNH, or to 100% Battery Level.
    4. Second powered climb-out at Maximum Power (100%+RPM) / 32 knots IAS to 6,500 feet QNH (0-5% remaining on the Battery Level indicator).
    5. Second charging-descent at idle (windmilling RPM ~40%), ~30 knots IAS to altitude of 4,000 feet QNH, or to 100% Battery Level.
    6. Third powered climb-out at Maximum Power (100%+RPM) / 32 knots IAS to 8,000 feet QNH (25% remaining on the Battery Level indicator).
    7. Third charging-descent at idle (windmilling RPM ~40%), ~30 knots IAS to altitude of 6,000 feet QNH, or to 100% Battery Level.
    8. Final powered climb-out at Maximum Power (100%+RPM) / 32 knots IAS to 10,000 feet QNH (25% remaining on the Battery Level indicator).
    9. You have reached cruise altitude. Commence Climbing/Charging-descent cycles between 8,000 and 10,000 feet QNH. Battery Level in the first cruise-cycle will be around 50% - 90%, and slowly should be stabled and managed between 75% - 100% during the rest of the cycles.
    10. At cruise altitude, RPM can be set to 50% to obtain Long-Range cruise 
    Rapid-Descent Practical Aspects:
      1. Descending from 10,000 feet QNH might take quite some time, and when required because of an emergency...might not be practical. The Split-Spoilers were designed to allow a rapid descent, safe performance within the aircraft airspeed limitations.  
      2. If needed, a Rapid-Descent can be achieved by simple arming the Split-Spoilers of the 'Contraventus' (operating 'Speed-Brakes' in X-Plane). The spoilers will increase the trimmed rate of descent (32 knots IAS) to 500-600 feet per minute, and will allow you to get a safe, 45 knots IAS rapid descent with sink rate of approximately 1200 feet per minute.
      3. At 55 knots, close to the Vne, you will be able to descend at ~2300 feet per minute.
      4. To stop the rapid descent, simply set the spoilers switch to off. Keep in mind to set back the trim to prevent over speeding.