SA551EA-D
Installation of autopilot go-around unit. Held by American Airlines INC, which holds 377 approved modifications in all. Last revised August 11, 1969. System: flight controls.
What it applies to
- Kind of product
- Aircraft
- Design holder
- The Boeing Company; The Boeing Company; The Boeing Company
- Models
- 707-100B Long Body, 707-100B Short Body, 720B Series
- Type certificates
- 4A21, 4A21, 4A28
- On this site
- Boeing 707 9 registered
- 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 20, 2026.