Enroute controller described an icing event that prohibited a PA28 from holding altitude and enterin...

Narrative:

A PA28 [was] traveling westbound on a vector to avoid high minimum IFR altitudes (mia's). He was level at FL140 when the MSAW started to flash. I told sme we had a faulty MSAW alert. When I finished my traffic scan I noticed that he was at FL135; the mia is FL138. I told him he was low and gave him the area's altimeter. He said he was picking up moderate icing and could not hold altitude and said he needed to turn around. I recommended a right 360 and issued the low altitude alert phraseology. He asked for a vector and I recommended a turn to the west which I misspoke then recommended an easterly heading. He wanted a vector to a nearby airport and I gave that to him when he cleared the high mia. He then proceeded to the airport and landed. Nothing could prevent the situation; but I should have declared an emergency to better help him out.

Original NASA ASRS Text

Title: Enroute Controller described an icing event that prohibited a PA28 from holding altitude and entering a below MIA situation. The reporter noted he should have declared an emergency for the aircraft in this situation.

Narrative: A PA28 [was] traveling westbound on a vector to avoid high minimum IFR altitudes (MIA's). He was level at FL140 when the MSAW started to flash. I told SME we had a faulty MSAW alert. When I finished my traffic scan I noticed that he was at FL135; the MIA is FL138. I told him he was low and gave him the area's altimeter. He said he was picking up moderate icing and could not hold altitude and said he needed to turn around. I recommended a right 360 and issued the low altitude alert phraseology. He asked for a vector and I recommended a turn to the west which I misspoke then recommended an easterly heading. He wanted a vector to a nearby airport and I gave that to him when he cleared the high MIA. He then proceeded to the airport and landed. Nothing could prevent the situation; but I should have declared an emergency to better help him out.

Data retrieved from NASA's ASRS site as of July 2013 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1033692
Time
Date	201208
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Aircraft 1
Make Model Name	PA-28 Cherokee/Archer/Dakota/Pillan/Warrior
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	ATC Issue All Types Inflight Event / Encounter Weather / Turbulence

Enroute controller described an icing event that prohibited a PA28 from holding altitude and entering a below mia situation. The reporter noted he should have declared an emergency for the aircraft in this situation.