# Advanced Air Mobility: Opportunities and Challenges Deploying eVTOLs for Air Ambulance Service
## 3 Methodological Overview
### Methodological Assumptions  
For this analysis, the authors introduced gasoline hybrid electric (referred to as 'hybrid') and eVTOL aircraft into the air ambulance marketplace. Based on a literature review and information obtained from the study advisory group, the authors assumed an average cruise speed of 402 km per hour (kph)/250 miles per hour (mph) for hybrid aircraft, 241 kph/150 mph for eVTOLs, and 160 kph/100 mph for conventional helicopters. The air ambulance flight profile consists of three primary mission phases (shown in Figure 2). This includes: Response (A-F), Transport (H-M), and Return to Service (N-R). The authors assumed that each of these sub-missions are flown with similar profiles (i.e.,  
Figure 1: Air ambulance concept of operations and temporal phases (times shown in minutes). Source: Data from [27]. Taxi, Hover Climb, Climb, Cruise, Descend, Hover Descend, and Taxi). While on-scene, it was assumed that the air ambulance is operating in a taxi configuration (e.g., idle on the ground). However, it is important to note that this methodology does not account for minor operational variations such as an eVTOL landing while on scene versus hovering in place to load a patient using a litter (rescue basket). These types of operational decisions are influenced by a number of unique circumstances such as weather, clearance to land, patient condition, risk to aircrew, and other factors. Total flight time represents the sum of response, transport, and return time. After completing the patient transport to the hospital, the air ambulance returns to its base (N-R) and is prepared to return to service (R-Q). For helicopters, return to service preparation time includes the time to refuel, whereas for eVTOLs, this period refers to the time required to recharge batteries for the next mission. The authors assumed that for hybrid aircraft, take-off landing is flown on electric (battery) power while remaining phases of flight are flown using a gas turbine engine. For this analysis it was assumed that eVTOL and hybrid aircraft transport one patient between an incident scene and the hospital. It was assumed that each aircraft would fly an average cruise altitude between 500 to 5000 feet above ground level. Per FAA duty hour requirements, a single emergency eVTOL and hybrid was required to have four full time pilots, four full time flight nurses, and four full time paramedics with CAMTS accreditation. Key operational assumptions used in this analysis are shown in Table 3. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Parameter** & **Sub Parameter** & **Minimum** & **Maximum** & **Data Source** \\ \hline \multirow{7}{*}{\
\begin{tabular}{c} Aircraft \\ Assumptions \\ \end{tabular} } & Cruise Speed (for eVTOL) 1  & 125 mph & 175 mph & [21] \\ \cline{2-5}  & Cruise Speed (for Hybrid) 2  & 200 mph & 300 mph & [28] \\ \cline{2-5}  & Equivalent Number of Seats 2  & 5 & 8 & [29] \\ \cline{2-5}  & Reserve (mins) & 20 & 30 & [30] \\ \cline{2-5}  & Range (miles) & 50 + Reserve & 200 + Reserve & [28] \\ \cline{2-5}  & Battery Capacity (kWh) & 100 kWh & 150 kWh & [31] \\ \cline{2-5}  & Annual number of Transports 3  & 300 & 400 & [5] \\ \hline \multirow{7}{*}{
\begin{tabular}{c} Crew/Payroll \\ Assumptions \\ \end{tabular} } & Pilot Salary (USD per year) & 60,000 & 100,000 & \\ \cline{2-5}  & Paramedic (USD per year) & 50,000 & 75,000 & \\ \cline{1-1} \cline{2-5}  & EMT (USD per year) & 60,000 & 90,000 & \\ \cline{1-1} \cline{2-5}  & Mechanic Salary (USD per year) 4  & 50,000 & 90,000 & \\ \hline \hline \end{tabular}  
* Cruise Speed is used to calculate Trip Speed, which is a parametric function of average distance, Landing and Take-off Speed and Cruise Speed. 2 Based on helicopter market to accommodate one patient. 3 Standard unit for Air ambulance utilization. 4 Air ambulances generally have one full-time mechanic on-site.  
\end{table} 
Table 3: Key operational assumptions. Figure 2: Flight profile for the air ambulance use case.