# Technical Standard Order (TSO)-C68a, Airborne Automatic Dead Reckoning Computer Equipment Utilizing Aircraft Heading and Doppler Ground Speed and Drift Angle Data (for Air Carrier Aircraft)
**AGENCY:**
Federal Aviation Administration (FAA), DOT.
**ACTION:**
Notice of intent to cancel Technical Standard Order (TSO)-C68a, Airborne automatic dead reckoning computer equipment utilizing aircraft heading and Doppler ground speed and drift angle data (for air carrier aircraft).
**SUMMARY:**
This notice announces the FAA's intent to cancel TSO-C68a, Airborne automatic dead reckoning computer equipment utilizing aircraft heading and Doppler ground speed and drift angle data. The effect of the cancelled TSO-68a will result in no new TSO-C68a design or production approvals.
**DATES:**
Comments must be received on or before July 23, 2012.
**FOR FURTHER INFORMATION CONTACT:**
Mr. Albert Sayadian, AIR-130, Federal Aviation Administration, 470 L'Enfant Plaza, Suite 4102, Washington, DC 20024. Telephone (202) 385-4652, fax (202) 385-4651, email to: *[email protected].*
**SUPPLEMENTARY INFORMATION:**
**Comments Invited**
You are invited to comment on the cancellation of the TSO-C68a by submitting written data, views, or arguments to the above address. Comments received may be examined, both before and after the closing date at the above address, weekdays except Federal holidays, between 8:30 a.m. and 4:30 p.m. The Director, Aircraft Certification Service, will consider all comments received on or before the closing date.
**Background**
Doppler radar is a semiautomatic self-contained dead reckoning navigation system (radar sensor plus computer) which is not continuously dependent on information derived from ground based or external aids. The system employs radar signals to detect and measure ground speed and drift angle, using the aircraft compass system as its directional reference. Doppler is less accurate than Inertial Navigation System (INS), however, and the use of an external reference is required for periodic updates if acceptable position accuracy is to be achieved on long range flights. Use of INS and Global Positioning System (GPS) has rendered TSO-C68a systems obsolete. The FAA has no record of any applications for TSO-C68a since it was published in 1983. Given the obsolescence of the equipment and the lack of industry interest in TSO-C68a product designs, we propose cancelling TSO-C68a.
Issued in Washington, DC, on June 18, 2012.
Susan J.M. Cabler,
Assistant Manager, Aircraft Engineering Division, Aircraft Certification Service.