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| ###  {#section .Paragraph}     |   |               |                  |
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| **Subject:** ANNOUNCEMENT OF   | * |               | **AC No:**       |
| AVAILABILITY- RTCA INC.,       | * |               | 150/5000-13A     |
| DOCUMENT RTCA-221              | D |               |                  |
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**1. PURPOSE.** This advisory circular (AC) announces the availability
of RTCA, Inc.,

Document RTCA/DO-221, Guidance and Recommended Requirements for Airport

Surface Movement Sensors, dated April 24, 1994.

**2. CANCELLATION.** AC 150/5000-13, Announcement of Availability-RTCA
Inc., Document RTCA-221, dated 09/07/94 is cancelled.

**3. PRINCIPAL CHANGES.** To update information.

**4. BACKGROUND.** Advisory Circular (AC) 120-57, Surface Movement
Guidance and

Control System (SMGCS), contains the requirements for U.S. airports
conducting operations in visibility conditions less than 1,200 feet
runway visual range (RVR).

Two essential components of such as system are stop bars and taxiway
lead-on lights at the entrance to an active low visibility runway. When
clearance to proceed is received by a pilot, the stop bar is turned off
by an air traffic controller and the taxi route to the runway is
indicated by green centerline lead-on lights. Automatic relighting of
the stop bar and extinguishing of lead-on lights is accomplished by the
use of surface movement sensors.

**5. APPLICATION.** RTCA/DO-221 provides recommended minimum performance
standards for airport surface movement sensors. These standards specify
both sensor and system characteristics that provide guidance to airport
systems designers, manufacturers, installers, and users of the
equipment. Sensors used for stop bar control are eligible for funding
under the Federal grant assistance program for airports. However,
sensors are not required to be qualified as detailed in AC 150/5345-53,
Airport Lighting Equipment Certification Program.

**6. PURPOSE.** Copies of RTCA/DO-221 may be purchased from RTCA, Inc.,

1828 L Street, N.W., Suite 805, Washington, DC 20036. For price and
ordering information call (202) 833-9339.

![](media/image1.jpeg){width="2.0277777777777777in"
height="0.9340277777777778in"}

Michael J. O'Donnell

Director of Airport Safety and Standards