October 19, 2017
To: GRT Customers
As a result of the problems encountered by Navworx with regard to their GPS performance, I, Greg Toman, chief engineer and owner of GRT Avionics, contacted Ken Heusser of the FAA Aircraft Compliance Office (ACO) in Fort Worth, TX, in January of this year to inquire about any possible compliance issues with respect to the GPS requirements in FAR 14 CFR 91.227 for the Safe-Fly GPS being developed at that time.
In my conversation with Mr. Heusser regarding this issue, I was assured that the GPS source we had selected was approved by the FAA and met the requirements of 14 CFR 91.227 regarding the GPS performance. Mr. Heusser was immediately familiar with this device, and FAA approval is documented in the datasheet describing it. Mr. Heusser recommended that we retain a copy of this datasheet, and reference this part in our internal documentation, which we have done. He further indicated that no formal written approval was required.
Further to meeting the spirit of the FAR, we provided a mechanism to update the software in our processor that is used to transmit this GPS data in the event we introduced any software fault. This mechanism functions without the removal of the GPS when it is connected to a compatible GRT EFIS. To date, no software bugs have been found.
To conclude, I am confident our Safe-Fly GPS is suitable GPS source for any ADS-B output device described in the Safe-Fly GPS manual.
Gregory R. Toman
GRT Avionics, Inc.