An air carrier first officer reported losing visual contact with the airport and with traffic they w...

Narrative:

Reported weather at iad was 039 ovc; 008 sct; 003 few; calm winds. We briefed visual to iad 1R backed up by ILS. After being turned onto approximately an 8 mile final at 2000' we were advised that we were less than five miles in trail of a B777 and needed to slow immediately to approach speed. Upon reaching glide slope we had visual on the field and decided to reduce automation in order to fly a dot high for wake turbulence avoidance. We also offset slightly to the right. We encountered unexpected unreported IMC conditions. I attempted to put aircraft back on GS and localizer. We noticed we had gone full scale on the localizer to the right. We were preparing for a go around when we broke out visually. Seeing that we were on PAPI glidepath and could correct to final we continued in VMC on glidepath and touched down in the TDZ. We trusted the ATIS weather report at night; we put too high a concern toward wake turbulence vs. Automation/flight guidance. We weren't 'go around' minded. Our hesitation about going around was unwarranted and needs to be done immediately. We should have asked for spacing from heavy rather than do it yourself avoidance at night in weather that can't be visually confirmed.

Original NASA ASRS Text

Title: An air carrier First Officer reported losing visual contact with the airport and with traffic they were following when they encountered unexpected IMC.

Narrative: Reported weather at IAD was 039 OVC; 008 SCT; 003 FEW; calm winds. We briefed visual to IAD 1R backed up by ILS. After being turned onto approximately an 8 mile final at 2000' we were advised that we were less than five miles in trail of a B777 and needed to slow immediately to approach speed. Upon reaching glide slope we had visual on the field and decided to reduce automation in order to fly a dot high for wake turbulence avoidance. We also offset slightly to the right. We encountered unexpected unreported IMC conditions. I attempted to put aircraft back on GS and LOC. We noticed we had gone full scale on the localizer to the right. We were preparing for a go around when we broke out visually. Seeing that we were on PAPI glidepath and could correct to final we continued in VMC on glidepath and touched down in the TDZ. We trusted the ATIS weather report at night; we put too high a concern toward wake turbulence vs. automation/flight guidance. We weren't 'go around' minded. Our hesitation about going around was unwarranted and needs to be done immediately. We should have asked for spacing from heavy rather than do it yourself avoidance at night in weather that can't be visually confirmed.

Data retrieved from NASA's ASRS site as of April 2012 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	882094
Time
Date	201003
Local Time Of Day	0601-1200
Place
Locale Reference	IAD.Airport
State Reference	DC
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Person 1
Function	First Officer Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Procedural Published Material / Policy Deviation - Track / Heading All Types Inflight Event / Encounter Weather / Turbulence

An air carrier first officer reported losing visual contact with the airport and with traffic they were following when they encountered unexpected IMC.