# Special Conditions: Boeing Model 707-353B (USAF C-137) Airplanes; High Intensity Radiated Fields (HIRF) Protection
> **Rule** · Final special conditions; request for comments. · Published 1999-07-21 · Effective 1999-07-13 · 64 FR 38999
## Document
- **Document number:** 99-18566
- **Category:** other
- **Type:** Rule
- **Action:** Final special conditions; request for comments.
- **Citation:** 64 FR 38999
- **Publication date:** 1999-07-21
- **Effective date:** 1999-07-13
- **FAA docket:** Docket No. NM159
## Abstract

These special conditions are issued for Boeing Model 707-353B (USAF C-137) airplanes. These airplanes will have novel and unusual design features when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. These design features include the installation of an inertial navigation system (INS) for which the current applicable airworthiness regulations do not contain adequate or appropriate safety standards with regard to protection of the system from the effects of high-intensity radiated fields. 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
- [Federal Register document](https://www.federalregister.gov/documents/1999/07/21/99-18566/special-conditions-boeing-model-707-353b-usaf-c-137-airplanes-high-intensity-radiated-fields-hirf)
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