Air Traffic Controllers reported an aircraft encountered inflight icing and descended towards terrain. ATC vectored pilot to airport for safe landing.
Synopsis
Air Traffic Controllers reported an aircraft encountered inflight icing and descended towards terrain. ATC vectored pilot to airport for safe landing.
Narrative
I was working the low altitude sectors when Aircraft X departed from ZZZ. the aircraft was climbing to 060 but requested to stay at 040. I issued 040 to the aircraft. I noticed the aircraft was having a difficult time staying on course. I questioned the pilot about this and offered assistance. The pilot asked for 060 for chop so I climbed him to 060. After a few moments I noticed the pilot was dropping below his assigned altitude and was still unable to stay on course. Again; I questioned and offered assistance. The pilot asked for 040 to get out of icing. I issued 040 and informed him of nearby airports if he needed to divert. Aircraft X was still in icing conditions at 040 so I issued 027 which is the MVA to try and find an altitude without icing. The pilot then asked about the airport I offered and decided to divert. At this point I was treating Aircraft X as an emergency aircraft. I cleared Aircraft X direct ZZZ1; but he requested a vector. I gave a vector direct to the airport. I noticed Aircraft X was deciding below the MVA. I let him know the MVA altitude for the area and where I observe him and issued to maintain 027. The pilot stated that he was trying to climb back up. At this point I decided it would be a better service to the pilot to hand him to ZZZ approach since they have better coverage to the ground and possibly know where the obstructions are below the MVA. Aircraft X was still below the MVA and descending. I issued that safety alert and told him to let me know when he is ready for a frequency change. He asked for the frequency; and I switched him to ZZZ approach. During all of this the X side was coordinating with ZZZ approach; and I was advising the CIC of everything that was happening. I never declared an emergency for the aircraft but treated it as such. We let ZZZ approach know so that they can [request priority handling] for the pilot. We continued to watch the aircraft until we lost radar. I took the lat/long and gave to the CIC.
Second reporter narrative
Aircraft X was an IFR departure from ZZZ going to ZZZ2. The aircraft departed off and climbed to 040. The pilot was weaving left and right of course by 40 degrees each side. The radar controller kept asking the pilot if everything was okay and if they needed assistance. The pilot responded that he was okay and that he was correcting. He then said that there was turbulence at 040 and requested to climb to 060. He was continuing to weave and then reported that there was icing at 060 and wanted to descend. The radar controller issued a descent to 040 and we at the d side began searching for weather reports in the surrounding area. The pilot then continued to descend and went below the minimum altitude. At this time the radar controller suggested ZZZ1 airport to the pilot since we found that the bases were at 028 in that area. The aircraft was given a vector towards ZZZ1 and was handed off to ZZZ [Approach]. I took over from training my trainee and coordinated with ZZZ [Approach] that the aircraft had not been issued a Low altitude alert at the time and needed to be issued one. The Radar controller heard me say this and attempted to broadcast to the pilot the Low altitude alert phraseology. The pilot was marked off frequency but was still on our frequency so he heard our low altitude alert and said he could not climb back up because he was unable to maintain altitude. The plane was now around 017 and below the 027 minimum altitude. The radar controller ended up switching him to Approach soon after and he made it safely to ZZZ1.We sat down right before this and in our briefing; we were unaware that there was icing conditions present in the ZZZ area. I guess we could be more proactive and tell the pilots of forecasted icing conditions in the area if there are any.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.