Day 1 Velis ground runs: How much time do I have to train during an e-plane flight?

Three UW aviation students joined WISA’s researcher Paul Parker and the WWFC team to put the Pipistrel Velis Electro through its first set of Canadian ground runs. The goal was to measure how much mission time or training time is available in the e-plane under different power settings. Before flying the aircraft in the air, these ground runs will give pilots a good indication of how much time they can plan to use.  

Paul conducted the first ground run solo and then was joined in the two seat e-plane with Gabriel, Kyra and Tyler. They had recently completed their CPL, commercial pilot license, as part of the University of Waterloo’s Aviation Program run in partnership with WWFC, Waterloo Wellington Flight Centre. Gabriel had extra knowledge as a member of the WWFC ground crew while Kyra and Tyler were members of the WWFC Safety Committee. They each experienced a ground run to collect data on charge/discharge cycles and better understand future flight mission times. 

The mission time was defined as the time taken to discharge the battery from 90% SOC to 30% SOC. SOC, or State of Charge, is a measure of how much energy is left in the battery. The experiment assumes that the first 10% of charge is used for take-off and climb to a suitable altitude, so mission time starts at the 90% mark. Similarly, 30% should be left in the battery when you land as a reserve, or for go-arounds, or unexpected needs. It also is best not to drain the battery too low as that could shorten its life. So that gives us 60% of the charge (90%-30%) for our useful mission. 

The plane was held stationary on the ground with chocks, parking brakes and attentive pilot/co-pilot. The largest use of electricity in an e-plane is the electric motor driving the propellor. However, avionics, flight computers and instruments, as well as radios and other equipment, also use electricity so these were turned on to simulate flight conditions. 

The standard cruise setting for the Velis Electro test e-plane is 25kW, so that was taken as a base measure and then comparisons were made with settings of +-5kW and +-10kW. The results are shown in the graph below. The standard 25kW setting gave 29 minutes of training time, or about half an hour. As expected, the higher the power setting, the shorter the time available. The highest power setting (35kW) had the shortest mission time (21 minutes) and the lower power setting (20kW) had the longest mission time (36 minutes).  

Note: we conducted a fifth ground run at 15kW to measure its mission time (47 minutes), but this is below the lowest recommended cruise power setting of 20kW and would cause the nose to be in a high position with forward vision obstructed. 

Of course, when you add take-off and climbing time to the mission time, actual flight time is longer. However, the flying time available remains much less than in conventional aircraft because avgas has a greater energy density than the LiPo batteries used.  

Current batteries offer the opportunity for short training flights using electricity from local low carbon electricity sources. Future batteries are expected to offer longer training sessions. The first message from these runs is: higher power settings will use the electricity in the batteries faster. As a result, it is no surprise to hear that some European flight schools use lower power settings to achieve longer flight times. 

Discharge patterns during the ground runs followed those expected from the POH, Pilot Operating Handbook.  All operating temperatures remained in the expected green ranges.  

Young pilots gained familiarity with new e-plane technology. Ready to learn more.  

One last thing, let’s wash the bugs off, so the e-plane is clean for the next day.