Introduction
The Federal Aviation Administration (FAA) has issued a notice of proposed rulemaking (NPRM) to adopt a new airworthiness directive (AD) for all General Atomics AeroTec Systems GmbH Model Dornier 228-100, 228-101, 228-200, 228-201, 228-202, and 228-212 airplanes. Published in the Federal Register on January 5, 2026, this proposal addresses reports of hydraulic pump motors becoming severely damaged by excessive heat, attributed to faulty carbon brushes. The AD would mandate replacing the affected motors with an improved design and prohibit future installations of the problematic part. This development underscores ongoing efforts to enhance aviation safety, potentially affecting 16 U.S.-registered aircraft and aligning with international regulatory actions to prevent uncontained fires that could lead to loss of control.
Background of the Issue
The NPRM stems from multiple reports of hydraulic pump motor failures on Dornier 228 airplanes, where excessive heat caused severe damage. Investigations identified the root cause as carbon brushes in motors with part number (P/N) 1259A, which degrade prematurely and generate heat buildup. As noted in the Federal Register entry, this condition, if unaddressed, could result in an uncontained fire, posing risks to passengers, crew, and aircraft control.
The European Union Aviation Safety Agency (EASA), the state of design authority for these aircraft, issued EASA AD 2025-0172 on August 4, 2025, mandating similar corrective actions. The FAA's proposal reflects its bilateral agreement with EASA, incorporating the mandatory continuing airworthiness information (MCAI) to ensure consistency in global aviation standards. General Atomics AeroTec Systems GmbH, the current type certificate holder (previously held by RUAG Aerospace Services GmbH), collaborated with the brush manufacturer to develop an improved motor, P/N A-752511A00B, featuring enhanced carbon brushes designed to withstand operational stresses better.
This issue highlights a broader pattern in aviation maintenance, where component wear in hydraulic systems can escalate into systemic failures. Hydraulic pumps are critical for functions like landing gear and flap operations, classified under Joint Aircraft System Component (JASC) Code 2913.
Key Players and Regulatory Framework
The FAA, under the Department of Transportation, leads this initiative as the U.S. civil aviation authority. Doug Rudolph, an FAA Aviation Safety Engineer, serves as the contact for further information, emphasizing the agency's technical oversight.
General Atomics AeroTec Systems GmbH, based in Germany, is the manufacturer responsible for the Dornier 228 series, a twin-turboprop aircraft used in regional transport and special missions. The company issued Service Bulletin Dornier 228 No. SB-228-360, Revision 0, dated May 28, 2025, providing guidance on the replacement process.
EASA's role as the technical agent for EU member states is pivotal, with its AD serving as the MCAI referenced in the NPRM. This collaboration exemplifies the FAA's reliance on international partners, as outlined in bilateral agreements, to address unsafe conditions in foreign-designed aircraft approved for U.S. operation.
The rulemaking process follows 14 CFR Part 39, which governs airworthiness directives. Authority derives from 49 U.S.C. sections, including 44701, empowering the FAA to prescribe safety regulations. The NPRM invites public comments until February 19, 2026, allowing stakeholders to influence the final rule.
Proposed Requirements and Compliance Details
The proposed AD requires replacing hydraulic pump motors with P/N 1259A within 200 hours time-in-service (for aircraft with a hydraulic system elapsed time indicator) or 600 landings (for those without), after the AD's effective date. The replacement must use the improved P/N A-752511A00B.
Additionally, the AD prohibits installing the affected P/N 1259A on any airplane post-effective date. Cost estimates from the FAA indicate $9,155 per aircraft, including three work-hours at $85 per hour and $8,900 in parts, totaling $146,480 for the 16 affected U.S. airplanes.
These measures directly target the unsafe condition, as described in the NPRM: "This AD was prompted by reports of several occurrences of hydraulic pump motors becoming severely damaged by excessive heat." The FAA's determination aligns with EASA's findings, emphasizing prevention of overheating that could lead to fire and loss of control.
Potential Implications and Perspectives
In the short term, operators face compliance costs and potential downtime for replacements, though the timeline allows for scheduled maintenance integration. Long-term benefits include enhanced safety and reduced risk of in-flight emergencies, potentially lowering insurance premiums and operational disruptions.
From a regulatory perspective, this AD reinforces the FAA's proactive stance on component failures, drawing on precedents like previous ADs for hydraulic systems in other aircraft models, such as those addressing pump failures in Boeing 737s (e.g., AD 2019-03-21). Industry groups may view it as necessary but burdensome for small fleets, while safety advocates praise the emphasis on preventive action.
Environmental and economic factors also play in, as the Dornier 228 often operates in remote areas, where failures could have amplified consequences. Different stakeholders, including operators and regulators, balance cost against safety, with no single viewpoint endorsed here.
Forward-Looking Conclusion
This NPRM represents a critical step in addressing a specific safety vulnerability in the Dornier 228 fleet, with potential for final adoption following public input. Future challenges may include monitoring the improved motor's performance and adapting to any emerging issues in hydraulic systems across aviation.
