| Bird Mass |
2.2 lb (1.0 kg)
* When considered multiple bird strike, the bird mass to be considered is 0.45 kg. |
2 lb (1.0 kg) |
When evaluated a single bird mass, the FAA requirement consider a bird mass 0.2 lb lighter than EASA requirement of even 14 CFR 27.631. Although it is not a big difference, it should be considered during the Certification Basis development.
Moreover, if multiple bird strike is evaluated, a different bird mass should be considered for EASA. The FAA, on the other hand, may not request multiple bird strike evaluation. |
| Aircraft Speed |
VH
* Specifically for windshield protection, panels should be capable of withstanding a bird impact without penetration for maximum speeds above 50 kt. |
VNE or VH
|
While EASA considers the maximum speed in level flight with maximum continuous power (VH), both 14 CFR 27.631 and 14 CFR 29.631 consider also the VNE. Whichever is the lesser should be considered.
In addition to this difference, there is another factor that should be evaluated: while EASA considers speeds above 50 kt for windshield evaluation, FAA requirement would consider the VNE or VH as well. |
| Altitudes |
Maximum operating altitude up to 8,000 ft
* When considered multiple bird strike, it is required the evaluation up to 4,000 ft. |
Maximum operating altitude up to 8,000 ft. |
There is no concern regarding the maximum operating altitude aspects since both requirements consider the same altitude operation for the evaluation when a single bird strike scenario is evaluated. However, if multiple bird strike is evaluated, it should be considered the maximum operating altitude up to 4000ft for EASA certification. The FAA, on the other hand, may not request multiple bird strike evaluation. |
| Multiple bird strike evaluation |
VTOL.2250(f) requests a multiple bird strike evaluation. |
Not considered in the evaluation. |
EASA requirement considers an evaluation of the effects of multiple bird strike in the most critical configurations, considering the potentially vulnerable redundant systems, structures and their effective exposed area. This is required for the structure and systems only. The evaluation is not required for the windshield.
Different from this EASA definition, according to the ARAC report, events of multiple bird impacts are rare in the data studied period (as also presented in Table 1) (FAA 2017b[FAA] Federal Aviation Administration (2017b) Rotorcraft bird strike working group recommendations to the Aviation Rulemaking Advisory Committee (ARAC). Washington, DC: FAA.).
A rotorcraft system may be vulnerable to multiple bird strike events, where the following systems can be affected, for example: air data sensors, antennas, lights, and various equipment. The ARAC group concluded from the studied data that separation, redundancy, or low criticality of these systems effectively minimizes that hazard, therefore the NWSD data did not indicate a significantly increased risk for multiple birds and thus implies an adequate level of protection is provided by 14 CFR 29.631, where any additional protection was requested by the ARAC (FAA 2017b[FAA] Federal Aviation Administration (2017b) Rotorcraft bird strike working group recommendations to the Aviation Rulemaking Advisory Committee (ARAC). Washington, DC: FAA.).
This is an aspect that presents potentially risks for certification when the same eVTOL project is considered to be certified in both FAA and EASA. |
| Bird Strike Requirement |
EASA presents a specific requirement that cover both windshield and systems/structure |
FAA Part 23 presents a requirement that would cover only the windshield |
The structure of the certification basis considering a bird strike requirement will present significant differences between EASA and FAA, since that EASA will cover the demonstration by the current regulation presented in the Special Condition VTOL, while, for FAA, the certification basis will be composed by Part 23, Part 27 or Part 29 requirements in addition to MOC or Special Condition IP, depending on the certification approach decided to be followed. |
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Source: Adapted from 
Source: Adapted from 
Source: Retrieved from
Source: Adapted from 
Source: Adapted from 
Source: Elaborated by the authors.
Source: Elaborated by the authors.