FAA Orders New FADEC Software on GE CF34-8C and CF34-8E Engines After Corroded Actuators Trigger In-Flight Alerts

The FAA has ordered operators of GE CF34-8C and CF34-8E engines to replace older versions of the engine control software, after corroded compressor parts set off “Engine Degraded” alerts in flight. Airworthiness directive 2026-21-11 was published in the Federal Register on October 22, 2026, and takes effect on November 27.

The FAA estimates the rule covers 3,364 engines on US-registered airplanes. GE Aerospace says the CF34-8C powers the CRJ series of regional jets and the CF34-8E powers the Embraer E170 and E175.

Why a corrosion problem led to a software fix

According to the directive, the FAA was told of three separate events on airplanes with CF34-8C5 engines in which the crew alerting system showed an “Engine Degraded” message during flight. An investigation by GE found the engines had flown only infrequently in the two years before and had been stored close to a saltwater coastline.

Corrosion between the high-pressure compressor case and the vane bushings had stuck the variable geometry (VG) lever arms. That raised the load on the VG actuators and slowed their response, so the vane position the computer commanded and its actual position drifted too far apart, and the alert fired.

The bigger worry was the computer’s reaction. GE and the FAA determined that some versions of the engine’s full authority digital electronic control (FADEC) software can answer that alert by pulling the engine back to idle and locking the throttle until the engine is shut down and restarted.

Left in place, the FAA says, that behavior could lead to the failure of one or more engines, loss of thrust control and reduced control of the airplane. The directive does not give the dates of the three events or name the operators.

Variable geometry vanes are the adjustable inlet guide vanes and stator vanes in the compressor. The engine control turns them as engine speed changes to keep air flowing smoothly through the compressor, so a vane that lags behind its command is a sign the control loop is not working as designed.

What operators must do, and by when

The rule splits the fleet in two. On Group 1, the CF34-8C1, -8C5, -8C5A1, -8C5A2 and -8C5B1, any software at version 6.50 or earlier has to be replaced with version 6.60 or a later approved release.

On Group 2, the CF34-8E2, -8E2A1, -8E5, -8E5A1, -8E5A2, -8E5A2HA, -8E6 and -8E6A1, version 5.60 or earlier must give way to version 5.70 or later. Both groups have 12 months from the effective date, which puts the deadline at November 27, 2027.

The rule applies only to engines fitted with the FADEC part numbers it lists, so an engine already running the newer software is compliant. The FAA puts the swap at eight work-hours and $660 in parts, or $1,340 per engine.

About 70 engines need more than a reload. Their FADEC software also needs a memory upgrade, from a three-sector to a seven-sector configuration, which the FAA prices at $49,680 each in addition to the software swap.

Across the US fleet the agency estimates a total of about $7.99 million. It expects no extra downtime, because the work can be done during regularly scheduled maintenance.

What changed since the proposal

The FAA first proposed the rule on November 18, 2025, when it counted 3,040 affected US engines. The final rule is adopted as proposed apart from minor edits, a new small-business analysis and that engine count, which rose to 3,364.

Three groups commented. The Air Line Pilots Association supported the rule, and the Citizens Rulemaking Alliance raised procedural and cost questions that led to no changes.

Horizon Air asked the FAA to reference GE Service Bulletin 73-0044, dated July 4, 2025, which carries instructions for the software update. The FAA declined, saying the bulletin is not required to comply.

The FAA’s small-business analysis shows who carries most of the bill. It counts 3,270 of the affected engines at 10 scheduled passenger airlines, which it does not name.

The second fix for the same corrosion

This is not the first time corroded VG hardware on these engines has drawn a directive. In AD 2022-08-06, effective April 29, 2022, the FAA required a torque check on the VG actuating linkage of CF34-8C and CF34-8E engines and, depending on the result, new compressor vane bushings.

That rule traced the problem to an August 11, 2021, in-flight shutdown and diversion of a CRJ1000 that had been parked outdoors within 10 miles (16 km) of a saltwater coastline. It also cited “Engine Degraded” messages on two CRJ900 regional jets in September and October 2021.

GE concluded then that engines stored outdoors for 250 days or more risk heavy corrosion, and that the risk rises near salt water. The 2022 rule fixed the hardware; the new one changes how the software responds when stiff vanes set off the alert.

The new directive lists no earlier AD as affected, so it neither revises nor replaces another rule. It follows the FAA’s October order for new PW4000 pressure sensors, another fix aimed at what an engine’s control computer does with bad inputs.