SE01537AT
Replace counterweights on Lycoming O-540-A1A5, -A1B5, -A1C5, -A1D5, and IO-540-C1B5 engines. Held by Whelen Aerospace Technologies, which holds 57 approved modifications in all. Last revised July 22, 2022. System: engine.
What it applies to
- Kind of product
- Engine
- Design holder
- Textron Lycoming AVCO Corporation; Textron Lycoming AVCO Corporation; Textron Lycoming AVCO Corporation; Textron Lycoming AVCO Corporation; Textron Lycoming AVCO Corporation
- Models
- IO-540-C1B5, O-540-A1D5, O-540-A1B5, O-540-A1A5, O-540-A1C5
- Type certificates
- 1E4, E-295, E-295, E-295, E-295
- The FAA's record
- On the FAA's site
What an approved modification is
A supplemental type certificate is the FAA's approval of a change to a certified design: a new engine or propeller, avionics, an autopilot, floats, a parachute, a larger fuel tank, an ice-protection kit. The company holding it may sell the kit and the paperwork to owners of the listed models; the modification then becomes part of that aircraft's record. The FAA's list says what was approved and for which models, not how many aircraft carry it.
Source: FAA supplemental type certificates (Dynamic Regulatory System). Register counts from the FAA register of October 5, 2026.