REPLY TO ATTENTION OF SFAE-AV 

### DEPARTMENT OF THE ARMY PROGRAM EXECUTIVE OFFICE, AVIATION 5667WOOD ROAD REDSTONE ARSENAL AL 35898-5000



### 2 9 SEP 2014_
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 RotaryWing Aircraft
1. This petition requests an exemption from a provision of 14 CFR Part 91.227 forthe U.S

.Army Rotary aircraftfleet. This petition follows the requirements for inclusion in such documents set forth 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. Army 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 transmitthe information within 3-seconds. Furthermore, comparing the results from the HH-60L and expanding it across the U.S. Army fleet of rotary wing (RW) aircraft which will be in service post January2020, ourassessment is that planned Automatic Dependent Surveillance
- Broadcast (ADS-B) Out modification efforts for many other aircraft 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 only way 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 RW are slow movers, under 200 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.SFAE-AV SUBJECT: Petition for Exemption From The Total Latency Provision of 14 CFR (Code of Federal Regulation) Part 91.227 ForThe U.S. Army RotaryWing Aircraft

c. Our Independent Government Cost Estimate (IGCE) to integrate ADS-8 Out, which we have programmed fundsfor, would meet 3-second latencyfor our aircraft's current architecture and avionics. However, to meetthe 2-second limit may involve extensive aircraft modifications, while not providing an appreciable safety benefit. Our delta IGCE to meet 2-second latencywould cost an additional $32.8M, which we have not programmed funds for. 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 up to an estimated $32.8M in integrations funds forthe U.S. Government and American taxpayer. Peran FAA analysis for slow moving aircraft, the FAA agreed 3-second latency does not pose an appreciable safety issue, sothe additional expense to meet 2-second latency is not justifiable. b. Lack of Funding. ArmyAviation has programmed funding to integrate ADS-8 Out intoArmy platform's current architecture and avionics. However, we have not programmed funding forthe additional $32.8M funding that would be required in upgrading processors, adding wiring harnesses and/or modification ofthe bus architectures in orderto decrease the latencyfrom 3-seconds to 2-seconds. With budgets under scrutiny and declining, obtaining additional funds to meet2-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 RWfleet have top speeds below 200 knots. Commercial airliners and fixed wing military aircraftfly at much faster speeds, usually at speeds exceeding 400 knots, butthey have the capability offlying even faster. It is understandable that fast moving aircraft must meetthe 2-second latency requirement; however, a slow moving RWthat 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 leniency without sacrificing safety. Atour request, the FAA analyzed the impact of having 3-second latencyfor slow moving aircraft and compared itto fast movers in relation to today's safety margins provided by radars.

2SFAE-AV SUBJECT: Petition for Exemption From The Total Latency Provision of 14 CFR (Code of Federal Regulation) Part 91.227 ForThe U.S. Army Rotary Wing Aircraft
b. The FAA's analysis determined there is no appreciable safety impact of relaxing the 2-second total latencyto 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 RWaircraftwill complywith the uncompensated 0.6-second latency requirement, which can be donewith current architecture and avionics. 5. A summary FAA can publish in the Federal Register is notapplicable forthis exemption. 6. Additional information, views orarguments available to supportArmy's request:
a. In most U.S. Army aircraft, both the aircraft position source(s) and the transponder are connected and communicate via a Mii-Std-1553 bus. The updated transponderwill supportAOS-8 Outvia both 1553 and ARINC-429 ports. Utilizing the current architecture and avionics peraircraft, AOS-8 Out compliance to a 3-second latency limit could be accomplished bysoftware upgrade to the avionics boxes. Army Aviation has programmed funding forAOS-8 Out integration forthe following platforms: UH-60NL, UH-60M, AH-640/E, OH-580/F, CH-47F, MH-60M, MH-47G, and NMH-6. Ourfunding will allow us to meetthe 0
.6-second uncompensated latency and total 3- second latency limit. b. IftheArmy RW have to meetthe 2-second latency limit, Army aviation will have to explore otherengineering options such as upgrading processors, or putting the Global Positionng System (GPS) and Common Transponder (CXP) on the same bus, or directly connecting the GPS and CXP via ARINC-429 ports. The architectural modificationsfor 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, aswell as installed and formally tested. Consequently, the additional expense to modify all RWArmy platforms to meetthe 2-second latency requirement is estimated to cost an additional $32.8M more than whatwas previously planned or budgeted for. Ifthere was a safety concern, this additional expense would be necessary; however, for slow moving RW aircraftthe FAA has already agreed that 3- second latency does not pose an appreciable safety issue, sothis additional expense is notjustifiable

. c. IfArmy RW aircraft are allowed to meetAOS-8 Out compliance to a 3-second total latency limit, thevast majorityofourfleet can be compliant bythe 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

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 Rotary Wing Aircraft modifications, there is a high likelihood that many U.S. Army aircraft may not make the January 2020 ADS-B Out equipage mandate. 7. Army will wantto exercise the privileges ofthe exemption outside the United States because the U.S. Army has requirements to fly outside the United States. 8. Points of contact: a. PM Aviation Mission Equipment, JeffWatteau, APM Surveillance, COMM (256) 876-3358, DSN 746-3358, or e-mail jeffrey.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.**0-t. ~dw** **·** ()..,

..ROBERT 

### L.

# ~RION V Brigadier General, USA Program Executive Officer, Aviation
CF: Commander, U
.S. Army Aeronautical Service Agency; 9325 Gunston Road, Bldg 1466, Suite N319; Fort Belvoir, VA 22060-5582

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