Single engine Flight Instructors reported entering icing conditions that exceeded the airplane's capability. Flight crew returned to the departure airport and landed safely.
Synopsis
Single engine Flight Instructors reported entering icing conditions that exceeded the airplane's capability. Flight crew returned to the departure airport and landed safely.
Narrative
We reviewed the weather on foreflight and website the morning of the flight. We thought that we could get above the overcast cloud layer and pick up minimal icing. Unfortunately that wasn't what happened. We started picking up light to moderate rime icing as soon as we entered IMC. We continued on; thinking that we would get above the clouds between 2000 and 2500 feet indicated. That is what we saw while retrieving a weather briefing. The freezing level was supposed to be at 7;000 feet if my memory is accurate and I believe that the CFII that I was flying with filed for 4;000 ft. We were aware of the Icing AIRMET; but foolishly thought we would be okay above the clouds (out of visible moisture) and under the forecasted freezing level.At 2500 feet we still did not have the cloud tops in sight and began to worry. I am not sure exactly when; but the CFII did ask ATC to confirm where the tops were supposed to be. we continued to climb and tried to get through the cloud layer. At about 3;800 feet indicated we lost a significant amount of power due to induction icing and experienced a rough running engine. We had turned on Carb Heat directly before entering the overcast layer; which may have contributed to us making it back to ZZZ.We requested priority handling I believe right before the rough running engine issue. It was decided that we had to get back to ZZZ and could not make it to ZZZ1 where ceilings were slightly better. right after this decision was made; our airspeed indicator dropped to a zero indication and remained there. Our VSI was bouncing up and down and we were uncertain if we could trust it. An ADS-B receiver was linked to our IPAD and the pilot in the right seat did their best to corroborate our vertical trends through that means. We flew by reference to the Altimeter; GPS ground speed; and Heading. We attempted to fly an RNAV approach; but realized that we needed to just fly vectors to the field. The controls felt mushy and the plane was becoming difficult to control.Due to the significant loss of engine power; increase in weight and decrease in lift from the extensive clear icing it did become impossible to continue any attempt to climb or even hold altitude. We were told to maintain three thousand feet; but closer to the airport it became apparent that we had to attempt to descend out of IMC. About 6 miles to the airport we gained faint visual of the ground while at 2;100 feet. We descended down to 1600 feet and remained there to stay out of clouds and visible moisture.5 miles away from ZZZ we lost comms with ATC but did continue to make calls. We were able to gain and retain visual of the airport 5 miles away. During this flight I was the pilot flying the other pilot was taking care of Comms; relaying vectors; and navigation system programming.
Second reporter narrative
A friend and I went flying to build some time in Aircraft X. We are both commercial pilots and instructors with similar hours flown; and we went out to try to build some hours in a plane that we both have experience in. On Day 0; we were diverted from our intended destination; due to accumulating light rime ice on the wings of the aircraft. The plane we were flying was not certified for FIKI (Flight Into Known Icing); so we both determined that if any icing occurred that we would land immediately. That night; we got a standard weather brief. The briefer did not recommend attempting to fly back to ZZZ2 until the morning; so we waited.The next day; the brief we obtained via Foreflight mentioned an AIRMET zulu that noted a freezing level at 7000 feet. We filed IFR for 4000 feet to stay under the freezing level and noted a PIREP that said the cloud tops were at 2600 feet. This would have given us a short amount of time to climb in IMC and make it up to our cruising altitude.Soon after takeoff; about 15 miles away; we started noticing that the clouds were much thicker than reported; and we were not breaking out at our top of climb altitude of 4000 feet. We started to accumulate mixed ice on the temperature probe; as well as the leading edges of the wings. When we noticed that the airspeed indication was incorrect; we rightly assumed that we were experiencing instrument icing as well. Shortly after the pitot static issues; we requested priority handling; as the clear ice on the flight surfaces was multiplying quickly. After requesting; we decided to turn back around to a close and familiar airfield; vectoring ourselves onto the RNAV XX approach (due to limitations of ATC. We were below MVA) to ensure obstacle clearance and landing accuracy. During the approach; we started to experience engine roughness. We had turned on pitot heat; defrosters; and carb heat; but we were certain that induction icing may start to become an issue. We notified the controller of all issues within a timely fashion and executed a safe landing on the ground at ZZZ. There was more than an inch of ice on multiple flight surfaces of the plane. Luckily; we were both instrument rated and trained to handle this in a way without ego or hazardous attitudes. We worked well together and got down safely.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.