Descent Rates & Minimum Deployment Altitudes: Why EASA's Means of Compliance 2512-Example #2 for Drone Parachute Recovery System Testing is Unsafe.

On July 6th, 2023, the Means of Compliance 2512 (MOC 2512) for M2 Mitigation, Medium Robustness was published. EASA - European Union Aviation Safety Agency published the MoC 2512 after an industry consultation period in 2022 and in-person meetings earlier in 2023.

MoC 2512 includes information on how to calculate the critical area (the size of the ground crash area when a drone experiences a loss of control event) and "an initial set of example ways to apply the general MoC" to reduce lethality with drone parachutes.

This article is a deep dive into the baseline requirements of parachute testing (a Type 2); therefore, perspectives/input on the methods of calculating the critical area and/or the use of a combination of methods, referenced as Type 3 in the MoC, have not been discussed.

For those unaware, EASA explains that Type 2 is used to reduce the ground risk:

"In order to obtain a ground risk reduction (GRr) of approximately 90% by means of a reduction of lethality only, the following applies:

? “Lethality” is defined as the probability of causing a fatal injury (fatality) by the UA upon impacting a person, having applied M2

? If lethality ≤ 0.1 (i.e. 10%) then 1 point less of GRC can be claimed"

Furthermore, EASA explains that "any M2 mitigation should specify the supporting evidence provided to support each of the three fundamental claims:

1. The mitigation means reduce the effect of ground impact

2. The mitigation means works with sufficient reliability in the event of a loss of control

3. The mitigation means does not increase risk

Applicants need to declare that they achieve all three claims. However, the applicant needs to support these declarations with evidence, which is documentation of appropriate testing, analysis, simulation, inspection, design review or operational experience."

What is the Difference Between Example #1 and Example #2?

In the examples for compliance, example #1 utilizes the ASTM International F38 committee F3322 parachute recovery system testing. This test requires 45 mid-air parachute activities under 5 failure scenarios.

These five failure scenarios validate a system's performance in Hover, Full Forward and when the drone were to lose Full Power and a Critical Number of Motors (e.g., for a quadcopter, 1 motor). As well, it requires Shock Load testing to validate that the system has a sufficient safety factor as no one wants to find out their parachute lines are not strong enough for the opening shock as that would be...shocking.

In example #2, EASA has offered companies an opportunity to fly in riskier missions with insufficient validation data. As you can see below, example #2 only requires 2 mid-air activations: "Compliance to 2.2.2 is achieved by compiling a test report showing that the mitigation means achieves the necessary performance target with the following: a) At least two representative flight tests should provide the evidence of the descent rate and minimum deployable altitude. The minimum deployable altitude should be tested at maximum take-off mass configuration." (Page 16)

Why is Example #1 safe whereas Example #2 is not?

The reason why the safe approach is Example #1, using ASTM F3322, is based on data.

Imagine that, a data-driven product decision for a regulatory requirement.

The brass tack is that 2 mid-air activations do not provide sufficient data to determine your descent rate or minimum deployable altitude. I would argue 2 mid-air activations would be reckless and negligent.

These statements are based on 6 of AVSS's ASTM F3322 testing campaigns, which includes 270 parachute test data points that were observed under a Third Party Testing Agency, a key requirement for ASTM F3322.

By reviewing the data in the following charts, you will see that (1) the average descent rate does not converge within 10% of the mean descent rate until approximately 30 tests. (2) Moreover, you will see that the minimum deployable altitude (MDA) does not converge until approximately 21 MDA tests. Note, MDA is determined by Automatic Triggering System (ATS) tests and that, of the 45 tests, 32 are related to the MDA whereas all 45 tests are used for the average descent rate.

"Speak as you might to a young child. Or a golden retriever."

If a company only completes two mid-air activations, they may declare that their parachute system works at 25 meters whereas it actually requires 50 meters. Imagine what happens to your business when, you as a professional operator of the DJI Dock 2, think you are safe at flying over the industrial site at 25 meters and you have a failure.

As well, what happens when the lawyers find out that the drone under parachute has exceeded the regulatory thresholds of transfer of energy because you designed it to the edge of acceptable kinetic energy targets?

If you'd like to learn more about what it takes for proper testing, please feel free to reach out.