It has been a challenging summer, but we are on track!

It has been a challenging summer, but we are on track!

The heat has been a challenge with operating the Alpha Electros this summer, but we have come up with some creative solutions that have allowed us to continue accruing hours toward our goal of 100 hours on one aircraft to support our petition for exemption with the FAA. We currently have over 70 hours across all four aircraft and over 50 hours on N197AM that was chosen to be the plane for the endurance testing for the petition.

The heat issues began to show themselves when ambient temperatures in Fresno started to get above 90 degrees F. Our initial concern was the battery temperature, but we also found a limiting factor was the temperature of the power controller, as Pipistrel refers to it. It is the device than converts the electric power from the batteries and provides it to the electric motor. It is liquid cooled using a small radiator mounted just below the motor. The same radiator provides cooling for the motor, but the temperature limits for operation of the motor are higher than the power controller. We found it was possible to have the power controller overheat quickly doing touch and goes on days when ambient temperature was over 90 degrees F. The solution was to use less power on take-off and for climbing during cruise operations. We found early on that it is possible to take-off at 40 kW vs. 65+kW at full gross weight and still climb at about 500 ft. per minute. We also learned the planes would climb slowly at 23 kW during cruise vs. 40 kW. By running less amperage through the power controller, the temperatures stayed lower, even on high ambient temperature days. We have tested this procedure over many days at 100+ degrees F and it works, so it has become our standard operating procedure on high ambient temperature days.

Another issue that arose during these hot days was the battery temperatures would exceed 40 C when charged in the hot hangar. Once the batteries were hot, they took over-night to cool back down and that limited the number of flights you could get to about 1-2 per day per aircraft. Clearly that was not going to work. The solution was to air condition the batteries during charging. I was able to find a small 6,100 btu rated spot air conditioner designed for cooling computer servers on Amazon for about $500. I had some clear Lexan windows cut to fit the openings in the battery compartments with a hole for a flange to attach dryer ducting and then used a “plastic tee” to split the air flow from the A/C unit to cool both batteries packs at the same time. The A/C unit puts out about cooled air at about 17 C that then circulates around the battery packs during charging. If the charging is done right after a flight, the automatic cooling fans on each pack turn on to draw the cooled air in even faster. The end result is we are able to cool the battery packs during charging so they are less than ambient temperature by the time the charging cycle is complete. This allows for another flight immediately after charging. We are now about to get about 4 flights per day per aircraft. Below is a photo of the A/C unit in action:

The A/C system is not optimized and we are going to work on building better adapter fittings for the battery compartment openings to have better air seals, but it works for now and we will refine it this winter when we won’t need the cooling.

Finally, we have been steadily trying to get more time aloft with the planes as we continue our testing and validation work. This past week due to some collaboration with other pilots interested in our work, we were able to get 1 hour of flight time on a charge and still land over 20% State of Charge. The procedure involves using the 40 kW take-off procedure, but when leveling off in cruise, we are trimming the planes for best L/D speed of 64 kts and setting the power for 14 kW with a single pilot. We have flown the aircraft for over 59 nm in this mode and achieved an impressive 3.62 nm/kWh fuel economy. When you convert that to statue miles per kWh to compare with an electric car, it equals 4.16 miles per kWh which is more than my Chevy Volt!

That is all for now, but if you would like to come and see the aircraft in operation, we will be doing some flight demonstrations at Fresno Chandler Executive Airport on September 29, 2018 as part of the 2018 “Remember When Fly-in and Car Show” sponsored by the Central Valley Aviation Association. Gates open at 9 am for the public and pilots are invited to bring their aircraft for display. Display aircraft should plan to arrive by 8:30 am at the latest. Event ends at 4 pm.

It’s been a while!


Sorry for taking so long to update everyone on our project; it has been an amazing several months since we took delivery of our four Alpha Electros and started flying them!

Here are some of the highlights:

  • We have accumulated about 40 hours of flight time across all four aircraft to date. They are a dream to fly with little to no vibration, nearly silent operation from the ground perspective, smooth power application, and very response handling.
  • We have two airports set up with chargers currently; Fresno Chandler Executive (KFCH) and Reedley Municipal (O32). Flight operating limitations from the FAA restrict us from doing traffic pattern work at Chandler, so we use Reedley for that.  There is currently an aircraft based at Reedley and three at Chandler and we are routinely flying back and forth between the two airports.
  • Mendota recently got a charger circuit set up and we plan to have a charger placed there by early July so we can start doing flight operations to Mendota.

Everyone asks me about how long you can stay up on a charge, which is a very reasonable question.  The answer is about 40 minutes and still land with over 20% State of Charge (SOC) remaining in the batteries.  The 20% SOC level is what Pipistrel recommends as a minimum for landing.  Below 20% SOC, the SOC bar on the EPSI570 (see photo below) turns red and you need to land and recharge the aircraft.

Our Alpha Electros have arrived!

Our Alpha Electros have arrived!! On the morning of March 13, 2018 at about 8:40 am, two 40 foot shipping container trucks rolled through the gate at Fresno Chandler Executive Airport with our four (4) Pipistrel Alpha Electros, four chargers, and a Pipistrel simulator destined for a customer in L.A. It took a crew of five to six about 2 hours to remove the aircraft and chargers from the trucks. We had to use a flatbed tow truck to back up to the containers so that we could roll the planes and chargers out. One plane had a flat tire and damaged main gear wheels due to loosening of the bolts that held the plane wheels to a steel bracket that was screwed to the container floor. One other plane had similar wheel damage from the same cause. It took about 10 minutes per plane to install the wings and horizontal stabilizers; the way Pipistrel designed the planes makes installation of the wings an easy process.
Michael Coates, the U.S. distributor for Pipistrel, and Sabi Apai, the Pipistrel dealer for California were on hand to help guide the process and were a great help! The planes had been at sea in the containers for 3 months and yet, the batteries were still at from 43% to 53% State of Charge when we inspected them. All aircraft were charged to the recommended 60-65% rest SOC the next day.
New wheel assemblies are being shipped from the factory tomorrow to replace the ones damaged in transport. The aircraft are scheduled for their airworthiness inspections on Wednesday, March 21. They are insured and registered, so once the airworthiness inspections are complete, we will make plans for the first flights. A brief taxi test was done on 3/18/18 to get the photo below in front of the historic Terminal Building at KFCH. Stay tuned for more updates in the coming days…


Largest concentration of Alpha Electro aircraft in the world (for now)!


Assembly crew

Our Alpha Electros are on their way to the U.S.!


Our Alpha Electros are on their way to the U.S.!  Just before Christmas all four of our Alpha Electros were completed and test flown at the factory.  They were then loaded in two containers and shipped to the U.S.  Below are some photos of two of the planes at the factory going through flight testing before they were loaded in the shipping containers.

Michael Coates, the U.S. distributor for Pipistrel, had requested the aircraft be shipped direct to California, but the shipper had other ideas.  Instead of coming from Italy west across the Atlantic and through the Panama Canal to California, the ship is going east through the Suez Canal, across the Indian Ocean to Port Kalang, Malaysia, then to Hong Kong, and finally to California.  The current estimate is the planes will arrive on the West Coast around the end of February and be delivered to Fresno around March 4.  Our planes are taking a world tour before coming to Fresno, but at least they are on their way!  Stay tuned for more updates…

Our Alpha Electros are late, but in production!!


Our Alpha Electros are late, but in production!!  When we ordered our Alpha Electros, the factory estimated they would be completed by the end of August and the first of September respectively and that we should receive them by mid-November.  However, that has not been the case.  We have been in contact with the factory through Michael Coates, their U.S. distributor, and the latest updates are that the aircraft are currently being completed at the factory, will be undergoing flight testing, and will be shipped for arrival around the first of January to mid-January.  Recently, Sabi Apai, the California dealer for Pipistrel, was at the factory for some training and sent these photos of our planes under construction.

The delays have not been an issue for the overall project since there are many moving pieces that need to be completed, such as installing the electrical circuits at the respective airports and getting new hangars at the City of Mendota.  Currently, we have installed charger circuits at Reedley Municipal Airport and Fresno Chandler Executive Airport.  Mendota has acquired a Port-a-Hangar and is working on getting an adjustment to their Airport Layout Plan to facilitate its installation and adding the charger circuit.  A second Port-a-Hangar will be acquired by January.

We have also been working with top level FAA staff in Washington D.C., Kansas City, and Seattle to get the initial airworthiness certification and collaborate on data collection to help advance electric propulsion in aviation within the U.S.  These talks are on-going, but the FAA staff we have been working with have been very helpful and very interested to be working with us on this project.  More updates on this front as they develop.

Once we have a more definite delivery date for the aircraft, we will let everyone know.  Stay tuned; we are getting closer to receiving aircraft.

Alpha Electros arrive at Oshkosh!


The two Alpha Electros ordered by the Tomorrow’s Aeronautical Museum (TAM) in Compton, CA have arrived at Oshkosh for AirVenture 2017!!  One will be on display at the Pipistrel Aircraft booth and the other located at GAMA pavilion.  Representatives from TAM will be at the Pipistrel booth to answer questions about their program and to talk about the coordination and collaboration they are doing with the Sustainable Aviation Project.  Both projects have similar goals to provide flight training with the Alpha Electros and showcase the value of electric propulsion aircraft in the U.S.  If you are going to Oshkosh, look up Thomas Paddon and Robin Petgrave from TAM while you are there and ask them about their program.  Also, more information can be found here:

The Sustainable Aviation Project is working to get the charger installation and hangar contracts out to bid concurrent with making the second progress payment for the four (4) Alpha Electros coming for our program.  We are still estimating delivery in October or early November.

Airplanes on order!

They are ordered!!  On May 24, the City of Reedley wired their deposits to Pipistrel for the last two Alpha Electros and sets of chargers for the project.  The City of Mendota had ordered their two aircraft and chargers the previous week, so now all four aircraft and chargers are ordered.  We have received serial numbers and completion dates from the Pipistrel factory with the Mendota aircraft scheduled to be completed at the factory in August and the Reedley aircraft to be completed in September of this year.  Pipistrel is saying the shipping will require an added 4-6 weeks, so we are expecting the aircraft to start arriving in Fresno by early October.


Today (April 12) we crossed a major milestone for our project!  The Fresno County Transportation Authority Board approved the $1,071,348 grant agreement with the City of Mendota and City of Reedley that authorizes the purchase of the four (4) Pipistrel Alpha Electro trainers, chargers for each aircraft, two new hangars for Mendota, and $90,000 in training assistance grant funds for youth from disadvantaged communities in Fresno County.  Each city must now approve the agreement, but that is just procedural at this point.  We should be ordering aircraft by the end of April or the first week of May.  Will update everyone once the orders are placed and we get an estimated delivery.  Stay tuned..

Grant reviews and electric chargers

We have had some new developments over the last few weeks that I want to share with everyone following our project.

  1. The draft cooperative grant agreement was sent to the City of Reedley and City of Mendota for review by Fresno County Transportation Authority on Friday of last week. Both City Managers are currently reviewing the document and our goal is to have the agreement signed and approved to release the funding by April 12 or shortly thereafter.
  2. We are meeting next week with staff from Mazzei Flying Service and Reedley College to go over the options for the aircraft and charger locations prior to finalizing the order for the aircraft after the grant agreement is signed on April 12. The charger locations are very important since each charger will be customized by Pipistrel to operate on the available voltage and amperage capacity at each hangar location on the respective airports.  Once the chargers are set up at the factory, they can’t be changed in the field to operate off different voltage, so we must get this right the first time.  Three of the four airports have 240 volt, 3- phase power available, and one has 240 volt single phase.  We have started to explore the possibility of using off-grid solar powered electric vehicle charging stations like this unit made by Envision Solar of San Diego called an EV ARC to provide power for the Alpha Electros as we expand the network of chargers across the Valley in the future (Phase II).

The solar panel tracks the sun and battery storage provides sufficient power to charge vehicles at night or during stormy weather.  The ARCs are portable (using a special truck and trailer arrangement seen in the background) and require no permitting or site preparation for installation.  An upgraded version of the ARC could be an ideal solution for adding electric aircraft charging infrastructure at small airports all over the region.  So far, Envision Solar has been supportive of the idea and we are exploring how these chargers could support both electric aircraft, cars, and even trucks from the same unit.  A zero-emission, zero-carbon solution for multiple modes of transportation at airports!   How cool would that be!!

Thanks for following our progress!  More updates as they come along so stay tuned.


First Blog Entry!

Welcome to the Sustainable Aviation Project Blog site.  My goal with these posts is to keep interested parties up to date on developments as the project progresses.  I am new to blogging, so please bear with me as I post updates.

Project Status:

We have $1,071,000 in funding approved to purchase the four (4) Pipistrel Alpha Electro trainers and chargers to support their operation at the four airports in Fresno County.  We are now working to get the grant agreement developed and signed by our partner cities of Reedley and Mendota.  Our target date for the grant agreement approval is the April 12 meeting for the granting agency, Fresno County Transportation Authority.  Following the agreement approval, we should be able to order the aircraft and chargers by mid-April.  Pipistrel is saying it will take about 6 months from date of order to receive the aircraft and equipment.  This will mean that the planes and equipment should arrive in mid-October 2017, if we can process the order as planned.  This is not a bad time of year in the San Joaquin Valley since the weather is still rather dry and temperatures are cooling off from summer.


Working with Pipistrel, we have determined that we can deploy three (3) 20 kW chargers that need 208/240 volt, 3-phase electricity and one (1) 10 kW charger that needs 208/240 volt single phase electricity to build our network of chargers for the aircraft operations at the four airports.  One 20 kW charger is planned to be located at Reedley Municipal (O32), Fresno Yosemite International (FAT), and Fresno Chandler Executive (FCH).  Mendota Municipal (M90) will get the 10 kW charger.  The chargers are not fully weatherproof, so they must be located inside hangars. This is a photo of a charger at the Pipistrel factory in Slovenia and you can see it is not in a weatherproof enclosure.

City of Mendota will get two new hangars as part of the project and our plan is to install the single charger in one of the hangars and provide a plug to the charger in each hangar.  This will require some wiring between the hangars, but since only one aircraft is being charged at a time, should not create any issue with charger capacity.  Here is a photo of the new hangar design.

This design matches the current hangar structure on the field as seen in this photo.

Cost of Operation on Electricity:

This is the # 1 question I get asked about the project and the quick answer is that we don’t know for sure since nobody in the U.S. has operated these aircraft yet.  However, we have come up with some estimates and here is what we think it will cost.

As context for people outside of California, our electricity costs here are some of the highest in the U.S., so costs for “fuel” in other areas could be much lower.  Of course, our 100LL costs are some of the highest in the country, so we think it will balance out.  In fact, the flight school that will be using the Alpha Electros is currently paying about $6.50 per gallon for avgas in their Piper Tomahawk trainers.

We are estimating the electricity “fuel” cost per hour at about $5 based on replacing 14 kWh of electricity for a 1 hour flight lesson at an average cost of $.35 per kWh.  The planes will have 21 kWh capacity battery packs which yields 90 minutes of total flight time per charge and 14 kWh represents about 66% of that capacity for a 1 hour training mission.  The $.35 per kWh is based on a Pacific Gas and Electric Company A-6 rate schedule (see this link for details )for commercial property customers.  The A-6 rate offers time-of-use electric costs that range from a maximum of $.55 per kWh for peak demand summer use from Noon to 6 pm weekdays to off-peak costs of $.18 per kWh from 9:30 pm to 8:30 am on weekdays and all day on Saturday and Sunday.  Partial peak costs are $.25 per kWh weekdays from 8:30 am to Noon and 6 pm to 9:30 pm.  The calculation is as follows:

The aircraft will fly 4 hours per day and operate 6 days per week.  Each aircraft will be fully charged overnight using off-peak electricity at $.18 per kWh for the first hour of flight @ $2.52.  Hour 2 will be charged using partial peak electricity at $.25 per kWh @ $3.50.  Hour 3 will be charged using peak electricity at $.55 per kWh @ $7.70.  Hour 4 will be charged at peak electricity at $.55 per kWh @ $7.70.  This results in a weekday average cost of electricity for 56 kWh per day of $5.35 per hour.  Weekend flights on Saturday will be a flat $2.52 per hour using the off-peak electricity.  Total weekly cost of electricity is estimated to be $117.18 for 24 hours of flight time which yields an average cost of $4.88 per hour.  This estimate is for summer operations.

During the winter, there is no peak demand costs, only partial and off-peak.  In this case the average should be about $.19 per kWh for the 56 kWh used each day or $2.66 per hour.

Of course, all this is an estimate at this point, but we will be equipping each charger with a data logger device and track the usage each day.

That is it for now.  Thanks for your interest in the project.  More posts as the project progresses.