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Engine & Propeller Issues List

Applicable to Domestic Certification Projects. Some or all of these items may be applicable to International Validations, refer to the applicable bilateral agreement and associated lists.

Engine Controls

Safety Impact of the Susceptibility to Atmospheric Neutrons

You may need an issue paper to establish a means of compliance with § 33.28 when the Electronic Engine Control (EEC) system for the Model engine could be susceptible to atmospheric neutrons. Atmospheric neutrons could change the state of the EEC system's digital memory or other digital circuitry. Memory or logic upsets that are not detected and corrected or mitigated could result in a malfunction of the system.

Use of Model-Based Development (MBD) Methods and Tools

You may need an issue paper to establish a means of compliance with § 33.28 if you and/or your airborne system developers propose to use Model-Based Development (MBD) methods and tools to develop software executing in airborne systems and equipment using DO-178B as guidance. Because DO-178B did not address the unique characteristics of MBD, there is the potential for misapplication of the existing guidance that could result in increased program risk and potential program delays. This IP would require you to demonstrate to the certification authorities that the appropriate software assurance has been achieved using MBD methods and tools.

Use of Multi-Core Processors

You may need an issue paper to establish a means of compliance if you and/or your airborne system developers propose to use one or more multi-core processors (MCP) in the airborne equipment for the aircraft. The existing software and Airborne Electronic Hardware (AEH) guidance was developed before MCPs were used in civil aircraft, so the existing guidance material does not specifically cover the use of MCPs or the planning, development or verification of software hosted on MCPs. MCPs are very complex and have architectural features that can cause anomalous behavior in safety-critical aircraft functions.

Overspeed Protection System

De-Activation of Overspeed Protection System

You may need an issue paper to establish a means of compliance with §33.27(c) & (e) when the overspeed protection system is de-activated in an OEI condition for any reason other than common mode effects. Common mode threat is defined as an engine shutdown due to activation of an overspeed protection system or portion of such system after another engine has been shut down by the loss of load overspeed protection system activation.

Icing

Fuel System Icing Threats

You may need an issue paper to establish a means of compliance with § 33.67 to address the threat to the engine from ice that may build up in the aircraft fuel system and release into the engine fuel inlet. This issue paper would require certification testing under § 33.67(b)(4)(ii) to include demonstration that ice released from the airplane system or entrained in the airplane fuel supply will not collect on the face of the fuel/oil heat exchange (FOHE), or any other part of the fuel system, and cause a restriction in fuel flow. Potential sources of ice include entrained ice crystals and chunks of solid ice that may be suddenly released due to factors such as changes in temperature, fuel flow or vibration.

Inlet Probe Icing

You may need an issue paper to establish a means of compliance with § 33.68 to address the threat from ice adversely affecting engine inlet probe signals or engine damage from probe ice buildup and release into the engine. The issue paper would require you to show that your engine and its components, including the inlet probes, are capable of performing their intended function in the declared flight envelope. The flight envelope evaluation should account for changing atmospheric conditions, such as icing, including ice crystal icing conditions. Testing the inlet probes in an ice crystal environment in accordance with Appendix D to part 33, Amendment 33-34 could be required. In addition, the engine control system § 33.28 system safety assessment should include consideration for inlet probe corruption from ice crystal contamination.

Operation in Heavy Snow Icing Threat

You may need an issue paper to establish a means of compliance with § 33.68 to address the threat to the engine when it is operated in atmospheric snow concentrations greater than 0.9 g/m3. This issue paper would require evaluation of the effect of operation in snow at concentrations up to the maximum you expect the engine to encounter in service, to show the engine will operate without adverse effect during taxi and takeoff. The results of the analysis would need to be incorporated into the installation manual for use by the airplane manufacturer in setting operational limits under 14 CFR 25.1093(b)(1). If you declare an engine operating limit for operating in heavy snow, that limit should be included in the § 33.5 operating manual. Such a limit, if declared, should not require specific equipment (on-board or on-airport) for the flight crew to make the determination of whether the limit has been exceeded.

Additive Manufacturing

Life Limited Parts

You need an issue paper to establish a means of compliance with § 33.70 to address the fatigue and damage tolerance requirements of Additive Manufacturing life limited parts. You may need an issue paper to establish a means of compliance with §33.15 to address the effects of the AM influencing part material manufacturing process to the design requirements (engineering intent).

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This page was originally published at: https://www.faa.gov/aircraft/air_cert/design_approvals/engine_prop/issues_list/