ASRS 1613267

Reporter 1

On flight to ORD air traffic control advised First Officer and I of a heavy aircraft ahead and 1,000 ft above our assigned altitude. I reported aircraft in sight. As the other aircraft appeared closer and closer on TCAS I had the flight attendant sit down for possible wake turbulence. While on the MADII 4 Arrival somewhere after SOOLU ATC told us to descend [to] 7,000 ft. While slowing in order to descend we encountered a wake, losing about 100 ft than gaining 150 ft but no more than 200 feet. After the encounter I asked ATC for a heading to aid in reestablish on the arrival. He gave us a heading of 090 and we descended to 7,000 ft and complied with new assigned heading. At no point did the aircraft [TCAS] give any type of proximity caution / warning. Would like more distance between heavy aircraft.

Reporter 2

On [our] flight to ORD, on the MADII 4 Arrival, between SOOLU and KURKK we were instructed to descend from 10,000 to 7,000. While we were slowing to descend our aircraft encountered uncommanded pitch and attitude inputs that resulted in altitude changes of +/- 100/150 ft. We quickly realized that we had entered the wake turbulence from a Heavy Aircraft in close proximity. The Captain asked for a heading from ATC, while I maintained aircraft control. Once in the clear, I began the descent to 7000. We proceeded to fly the ILS to 27R. Upon landing we were told to give TRACON a call. We explained the situation, fortunately, no one was hurt. We were a little frazzled by the event. I feel as a crew, we could have done a better job of communicating with ATC.