The U.S. aircraft register, updated daily
Special conditions

Special Conditions: Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F Airplanes; High Intensity Radiated Fields (HIRF)

Special conditions are rules the FAA writes for one design when the standard certification rules do not cover something new about it. These were published March 2, 2003 for Royal Air. System: instruments and avionics.

What it applies to

Applicant
Royal Air
Makes
Learjet
Models
—
Published
March 2, 2003
Effective
February 20, 2003
The FAA's document
On the FAA's site

The FAA's summary their words, unchanged

These special conditions are issued for Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes modified by Royal Air, Inc. These airplanes, as modified, will have novel and unusual design features when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. The modification incorporates the installation of the Innovative Solutions & Support (IS&S) Air Data Display Units (ADDU) and Air Data Sensor. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for the protection of these systems from the effects of high-intensity-radiated fields (HIRF). These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards.

Source: FAA special conditions (final) from the Dynamic Regulatory System; the Federal Register carries the same notices.