Date: 201408
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Weather elements / visibility: Icing
Aircraft: S-70/UH-60 Blackhawk/Seahawk/Pavehawk/Knighthawk
Operator: Military
Operating under: Part 91
Flight plan: IFR
Mission: Tactical
Flight phase: Cruise
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Second aircraft: S-70/UH-60 Blackhawk/Seahawk/Pavehawk/Knighthawk
Reporter organization: Government
Reporter function: Enroute
Reporter qualification: Air Traffic Control Fully Certified
Human factors: Communication Breakdown; Confusion; Situational Awareness
Anomaly: Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Detector: Person Air Traffic Control
When detected: Taxi
Result: Air Traffic Control Provided Assistance; Air Traffic Control Separated Traffic; Flight Crew Took Evasive Action
Contributing factors: Weather; Procedure; Human Factors; Aircraft
Primary problem: Weather

Narrative: I took the hand-offs on Aircraft X at FL160; and Aircraft Y at FL170. I could not communicate with them and was relaying through an Air Carrier. I should [have] been able to talk to them at those altitudes. At this point I had 1;000 FT and about 7 miles lateral separation. Both aircraft were deviating for weather to the South of their route. Lost Aircraft X in Radar and Aircraft Y informed me he was going back on course and going to rejoin the airway. I informed him Radar Contact was lost. I should [have] had good radar coverage on both of these aircraft. Aircraft X informed me he was heading 300 to rejoin the airway. Aircraft Y had a request to descend to FL160 was in light ice at FL170. I told him unable do to non-radar separation rules with his company; I offered him a climb which he did not take. I also told him the only way I could descend him is if it was an emergency. He said he would stay at FL170. I just got a [A-side] to help and got a PIREP for the icing. Shortly after Aircraft Y was in moderate icing and was unable to maintain altitude. I declared an Emergency for him and descended him to FL160. I informed Aircraft X that I was using less than standard non-radar separation. Aircraft X was radar identified and told to maintain FL160. Aircraft Y gave a DME report of 41 'West' of ZZZ but I did not correct him knowing he meant East of ZZZ. I then asked Sector X to spin Aircraft Z who was at FL160. I descended Aircraft X to FL150. I asked Aircraft Y if he was out of the icing. He was out of the icing and level at FL160. I told Aircraft Y speed was his discretion gave him the local altimeter and advised him that his company was at FL150. Aircraft Y reported on the airway but was still non-radar and got a 32 DME report 'West' of ZZZ but once again did not correct the pilot knowing he was East of ZZZ. I then issued Aircraft Y holding instructions at ZZZ as published with an EFC of XX00Z; maintain FL160. I noticed the adjacent Sector X climbing Aircraft Z to FL170 into the area of known icing. I called that sector. I asked Aircraft X his intention and he indicated he wanted the ILS to RWY 6 another aircraft I believe Aircraft Y took the call. I told Aircraft Y to expect to hold till his company was safe on the ground. Aircraft Z checked in at FL170. I informed him of the ice and about his company. He said 'I'll push south and descend to FL160.' I told him to maintain FL170 and asked him if he was requesting FL160. Then I gave him a descent clearance to FL160 and clearance to deviate south of course. I noticed Aircraft Y descending below his assigned altitude of FL160 to FL154 without a clearance. He informed me that he was in VFR conditions and would cancel IFR. I gave Aircraft X an approach clearance to maintain 150 till ZZZ cleared ILS RWY 6. He said he was descending to FL120. I corrected him and told him to maintain FL150 till ZZZ. However he still descended below his clearance down to FL146. He said I'm correcting. Aircraft X canceled IFR and I asked him to call the facility and issued him the number. I lost Aircraft Z in Radar and should [have] had him. When I asked him his radial and DME from ZZZ he said 60 DME on the 281 radial. Again [the position report] was incorrect; I knew that had to be the bearing to the VOR and he was probably on the ZZZ101R. I got a Radar hit on Aircraft Z at FL153 in a FL160 MEA. I told him to climb and maintain FL160 and gave him local altimeter. He told me he was unable to maintain FL160 at this time. I told him I was going to declare and Emergency for him. I told him my minimum IFR altitude is FL160. I issued a safety alert followed by a low altitude alert. He said he was established at FL155. Aircraft Z said I'm descending to FL150; were getting icing up here and I issued him FL150. Aircraft Y was in the clear. I gave Aircraft Y a clearance to FL140. He was below his assigned altitude at FL135; I gave him yet another low altitude alert.Better Radios [and] RadarCoverage. Better training for the pilots. No training missions with similar call signs; No training into known icing in mountains.




Synopsis: Center Controller reports of three helicopters that encountered icing while working them and two were declared emergencies to be able to descend.