CRJ-700 flight crew reported executing a go-around at ORD when the autopilot had difficulty tracking the localizer; either because of autopilot issues or wake turbulence.
Synopsis
CRJ-700 flight crew reported executing a go-around at ORD when the autopilot had difficulty tracking the localizer; either because of autopilot issues or wake turbulence.
Narrative
We were on the Espo Arrval; and on the downwind leg we heard a heavy being vectored on to the 10C ILS PRM approach. When we turned base we asked if we were going to be following the heavy; and was told we were not. After another transmission from Approach to another aircraft he came back and said that we would be following a heavy. We were given a slightly late (it seemed) vector on to final to intercept. We went through final a little bit as we had a tailwind. I asked approach if we could slow a little more because of following the heavy with a quartering tailwind but was told he knew about the wind and wanted the speed.As we were trying to capture the localizer the autopilot struggled with capturing it and began to bank excessively in both directions to capture it. At this point we began to hand fly and decided to discontinue the approach as it was in the best interest of safety to not continue as we were not stable and I did not foresee us being able to continue in a safe and stabilized manner. We were told to track the localizer outbound and the plane struggled with that in autopilot as well. Before we began to once again go to hand flying we were given a heading.We were given vectors to ILS PRM 10R for another attempt. When we were vectored on the approach the autopilot did struggle to capture the approach; but shortly after being vectored on we lost the localizer on both sides. At this point we were vectored off and we let ATC or approach; I don't remember who we were talking to; know that we lost the localizer. We were given the GPS to Runway 9L. We flew that approach and continued without any further problems.The primary cause of this was automation problems with the localizer/autopilot; however the autopilot only struggled in Green Needles with the Localizer; and in no other modes. A possible contributing factor was wake encounter with preceding heavy with quartering tailwind. I do not know for certain this was the case; as there was no violent upset; however while we had problems capturing both localizers; the autopilot only banked excessively when we followed the heavy; almost as if we were in wake.Maintenance required for the navigation radios would be a primary fix as this seemed to be a problem with the systems. However; as wake turbulence was a possible or plausible contributing factor; I think it would be important to mention that is seems that lack of concern of wake turbulence and the associated hazards is becoming a common issue I have noticed. In addition to this it seems that there is a lack of understanding on the part of FAA Facilities how wind and altitude will affect wake. Better understanding as well as better cooperation and coordination with air crews on the part of controllers would lead to a safer working environment.
Second reporter narrative
On an ILS PRM approach into ORD Runway 10C; we executed a missed approach. When on crosswind; we assumed we were following a heavy; so we asked ATC. The initial response was that we were not; then eventually yes. After that; we got vectored onto the localizer; and immediately started our turn to intercept the localizer; but the vector was too late due to high winds and we went through the localizer. As we were turning back in to intercept the localizer; the autopilot could not pick up and intercept the localizer. At this time we were following a heavy; and had a quartering tailwind. The plane made very large heading changes to try and intercept the localizer; but it could not do it. We then executed a missed approach. After we got vectored around to Runway 10R ILS; the aircraft still did a very poor job of intercepting the localizer; then quickly lost the localizer completely. We had a localizer failure. We got vectored back around for an RNAV and had no trouble with it.Mechanical; and possible wake. On approach number one the aircraft could not capture the localizer; and on approach number 2 after it did a poor job of capturing; it lost the localizer completely resulting in a missed approach.Avoid close proximity to a heavy with a quartering tailwind.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.