REPLY TO ATTENTION OF SFAE-AV DEPARTMENT OF THE ARMY PROGRAM EXECUTIVE OFFICE, AVIATION 5667 WOOD ROAD REDSTONE ARSENAL AL 35898-5000

2 9 SEP l\114
MEMORANDUM FOR Federal Aviation Administration, Office of Rulemaking, Airmen and Airspace Rules Division (FAA, Keira Jones), 800 Independence Ave SW, Washington, DC 20591 SUBJECT: Petition For Exemption From The Total Latency Provision of 14 CFR (Code of Federal Regulation) Part 91.227 ForThe U.S. Army Unmanned Aircraft
1. This petition requests an exemption from a provision of 14 CFR Part 91.227 forthe U.S. Army Unmanned aircraft fleet. This petition follows the requirements for inclusion in such documents setforth in the order presented in 14 CFR Part 11.81:
a. The requested exemption is for 14 CFR 91.227 (e)(1)

. b. The extent of relief is from the allowed 2 seconds total latency increasing to 3 seconds total latency. 2. The U.S. AirArmy requests an exemption from compliance with the 14 CFR 91.227 (e)(1) because:
a. Tests conducted on our HH-60L aircraft revealed that,with its current architecture and avionics, it would exceed the CFR's overall 2-second total latency requirement, but will be able to transmit the information within 3-seconds. Furthermore, comparing the results from the HH-60L and expanding it across the U.S. Armyfleet of Unmanned Aerial Systems (UAS) which will be in service post January 2020, our assessment is that planned Automated Dependent Surveillance-Broadcast (ADS-B) Out modification efforts for many otheraircraft may not achieve the 2-second limit, butwould achieve a 3-second latency. b. Ifthe 2-second latency is not achieved with current architectures, the onlyway to meetthe current 2-second requirement would be through aircraft modifications such as upgrading processors, adding wiring harnesses and/or modification ofthe bus architectures. Since the U.S. Army fleet of UAS are slow movers, under200 knots, an FAA study offast moving versus slow moving aircraft has shown there are no appreciable safety issues for slow movers who meet 3-second latency.
c. Our Independent Government Cost Estimate (IGCE) to integrate ADS-B Out, which we have programmed funds for, would meet 3-second latencyfor ouraircraft'sSFAE-AV SUBJECT: Petition For Exemption From The Total Latency Provision of 14 CFR (Code of Federal Regulation) Part 91.227 ForThe U.S. Army Unmanned Aircraft
current architecture and avionics. However,to meetthe 2-second limit may involve extensive aircraft modifications, while not providing an appreciable safety benefit. 3. Granting this request would be in the public interestand benefit the public as a whole: a. Save Taxpayer Money. A relaxation ofthe requirementfrom 2 to 3 seconds will meetthe safety needs ofthe FAA, while saving integrations funds forthe U.S. Government and American taxpayer. Per an FAA analysisfor slow moving aircraft, the FAA agreed 3-second latency does not pose an appreciable safety issue, so the additional expense to meet2-second latency is notjustifiable. b. Lack of Funding. ArmyAviation has programmed funding to integrate ADS-8 Out into Army platform's current architecture and avionics. However, we have not programmed funding that would be required in upgrading processors, adding wiring harnesses and/or modification ofthe bus architectures in orderto decrease the latency from 3-seconds to 2-seconds. With budgets under scrutiny and declining, obtaining additional funds to meet 2-second latencywould be difficult. 4. Granting the exemption would not adversely affect safety, 3 seconds oftotal latency would provide a level ofsafety at least equal to that provided by the rule from which Army seeks the exemption: a. The U
.S. Army UASfleet have top speeds below 200 knots. Commercial airliners and fixed wing military aircraftfly at much faster speeds, usually at speeds exceeding 400 knots, but they have the capability offlying even faster

. It is understandable that fast moving aircraft must meetthe 2-second latency requirement; however, a slow moving UAS that meets 3-second latency poses no safety threat. Since the latency requirement applies to a broad speed range;the DoD has assessed there is room for some leniencywithout sacrificing safety. At our request, the FAA analyzed the impact ofhaving 3-second latency for slow moving aircraft and compared it to fast movers in relation to today's safety margins provided by radars. b. The FAA's analysis determined there is no appreciable safety impact of relaxing the 2-second total latency to 3-seconds for slow moving aircraft. For uncompensated latency, the findings reinforced that 0.6-second uncompensated latency is critical to maintaining safety margins
. The U.S. Army UAS aircraft will complywith the uncompensated 0.6-second latency requirement,which can be done with current architecture and avionics.

2SFAE-AV SUBJECT: Petition For Exemption From The Total Latency Provision of 14 CFR (Code of Federal Regulation) Part 91.227 For U.S. Army Unmanned Aircraft 5. A summary FAA can publish in the Federal Register is not applicable forthis exemption. 6. Additional information, views orarguments available to supportArmy's request:
a. In most U.S. Army UAS, both the aircraft position source(s) and the transponder are connected and communicate via a Mii-Std-1553 bus. The updated transponder will supportADS-B Outvia both 1553 and ARINC-429 ports. Utilizing the current architecture and avionics per aircraft, ADS-B Out compliance to a 3-second latency limit could be accomplished by software upgrade to the avionics boxes. Army Aviation has programmed funding forADS-BOut integration for the following platforms: RQ-7 and MQ-1C. Ourfunding will allow us to meetthe 0.6-second uncompensated latency and total 3-second latency limit. b. Ifthe Army UAS have to meetthe 2-second latency limit, Army aviation will have to explore other engineering options such as upgrading processors, or putting the Global Positioning System (GPS) and Common Transponder (CXP) on the same bus, or directly connecting the GPS and CXP via ARINC-429 ports. The architectural modifications for any ofthese options are more extensive than were originally planned or budgeted for. Additionally, some ofthese options could require installation A-kits to be developed, as well as installed and formally tested. Consequently, the additional expense to modify all UAS Army platforms to meetthe 2-second latency requirement is more than whatwas previously planned or budgeted for. Ifthere was a safety concern, this additional expense would be necessary; however, for slow moving UAS aircraft the FAA has already agreed that 3-second latency does not pose an appreciable safety issue, so this additional expense is notjustifiable.
c. IfArmy UAS aircraft are allowed to meetADS-B Out compliance to a 3-second total latency limit, the vast majority ofourfleet can be compliant by the January 2020 mandate. In contrast, ifwe have to meetthe 2-second .total latency limit, because ofthe development and integration of installation kits and more extensive aircraft modifications, there is a high likelihood that many U.S

.Army aircraft may not make the January 2020ADS-B Out equipage mandate. 7. Army will want to exercise the privileges ofthe exemption outside the United States because the U. S. Army has requirements to fly outside the United States.

3SFAE-AV SUBJECT: Petition for Exemption From The Total Latency Provision of 14 CFR (Code of Federal Regulation) Part 91.227 ForThe U.S

.Army Unmanned Aircraft
8. Points ofcontact: a. PM Aviation Mission Equipment, JeffWatteau, APM Surveillance, COMM (256) 876-3358, DSN 746-3358, ore-mailjeffrey.a.watteau.civ@mail.mil. b. DoD NextGen Lead Service Office, COL Philip Basso, COMM (202) 404-7129, or e-mail philip.basso@pentagon.af.mil.

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# M~ION Brigadier General, USA Program Executive Officer, Aviation
CF: Commander, U.S

.ArmyAeronautical Service Agency; 9325 Gunston Road, Bldg 1466, Suite N319; Fort Belvoir, VA22060-5582

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