' Surdex Geospatial Systems Integration, LLC 203 Airport Drive, Hangar 6 Westminster, MD 21157 tel 800-847-6459 fax 410-391-1767 www.surdexsgsi.com

August 12, 2011



### Ms. BrendaD. Courtney Manager, Aircraft and AirportRules Division Federal Aviation Administration 800 IndependenceAve., S.W. Washington, DC 20591

DearMs. Courtney, Chuck King Director ofMaintenance

chuckk@surdexgsi.com

In response to your June 30, 2011 letter for a request for additional information, Docket#FAA2011-0534 and your extensionfor ourresponse to August 18, 2011, please accept this letter as an addendum to Surdex Geospatial Systems Integration's (SGSI) original request dated May 10, 2011 for exemption as defined by 14 CFR 125.3(a), from 14 CFR 125.226(b)(2) for three ATR42-320 aircraft.
In your request for information letter, you indicated we must send the following information to meet the requirements of 14 CFRPart 11.81:
1. The reasons granting the request would be in the public interest: that is, how it would benefit the public as a whole. 2. Any more information, views, orarguments to support the request.
SGSIbelieves it is in thepublic's interest to grant the exemption for the following reasons:
1. Thethree aircraft have been safely operated since 1991 without the additional parameters. Adding these parameters through an extensive aircraft modification program will not enhancepublic safety. SGSI operates the aircraft t o conduct geological survey services with a crew ofsix company employees. SGSI does not carry passengers or cargo. 2. Parameters (a) .12, 13, and 14 do not enhance aircraft safety, airworthiness, orhandling qualities since they record flight control inputs for data collection only. Primary flight controls are mechanical and their position is continually monitored and recorded. 3. The aircraft OEM does not support upgrading the Flight Data Acquisition Unit (FDAU) to add the additional parameters since itis no longer in production. SGSI has not found any possible solution to upgrading the FDAU before February 2012.Surdex Geospatial Systems Integration, LLC 203 Airport Drive, Hangar 6 Westminster, MD 21157 tei80D-847-6459 fax 410-391-1767 www.surdexsgsi.com

Chuck l<ing Director ofMaintenance

chuckk@surdexgsi.com In the event ourrequest for an exemption is denied, SGSI would respectfully request a temporary extension to the LODA expiration ofFebruary 2012 to February 2013 in orderto modify all three aircraft to meet the required FORparameters and allow SGSI adequate time to plan for upgrading the FDAU and FDR via STC or OEM development ofa service bulletin. SGSI's business plan would consist ofapproximately 12 months ofengineering development and approximately 6 months for modifications.
In closing, this request is not intended to disregard the Federal Aviation Regulation, but to continue to operate with an equivalent level ofsafety. Thecurrent FDR system records 39 parameters, but does not record required flight control inputs. However the system records the required flight control surfacepositions. Since the flight control systems are mechanical and there are no hydraulic orelectronic controls, it would impossible for the surface and control to be in different positions other than a break in the control circuit. We feel this allows for an equivalent level ofsafety. In addition, it is noted that our operationprovides aerial survey services and only carries crewmembers, neverpassengers. Please contact me ifyou have any questions.

Sincerely,

Chuck King Director ofMaintenance