Date: 201501
Local time of day: 1201-1800
Location: ANC.Airport, AK
Flight conditions: VMC
Weather elements / visibility: 10
Light: Daylight
Aircraft: Learjet 31
Operator: Air Taxi
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Final Approach
Airspace: Class C ANC
ATC / advisory: Tower ANC
Reporter organization: Air Taxi
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Instrument
Anomaly: Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Wake Vortex Encounter
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Executed Go Around / Missed Approach; Flight Crew Regained Aircraft Control; Flight Crew Took Evasive Action
Contributing factors: Airport; Environment - Non Weather Related; Procedure
Primary problem: Procedure

Narrative: We were descending while being vectored on a right downwind for runway 7R.  Approach control pointed out traffic; a 777 on final for 7L; which I reported in sight.  As we passed the 777; approach control turned us to a heading of 040 and cleared us for a visual approach to 7R with instructions not to overtake the 777 and to plan to land long.  We intercepted final just west of Fire Island; approximately 6 NM from the threshold of 7R.  We were level with the 777 at that point. We had the 7R ILS tuned for backup guidance; so I instructed the first officer to stay at least one dot high on the ILS glideslope.  I checked the wind vector on the HSI; which showed a 19 knot wind from the right; and the last time I looked at the glideslope pointer; it was showing almost full deflection high.  When we were fully configured for landing and slowed to final approach speed; the 777 was faster and was moving away.  As I watched the 777 moving away from us; I became aware of how far the parallel runways are staggered.  The threshold for 7L is well beyond the threshold for 7R; and I became concerned that we might not be staying high enough to avoid the wake turbulence.  I considered that it might be a good idea to tune the ILS for 7L to ensure we were remaining above that glideslope; and checked the wind vector again; which was now showing a 9 knot wind from the left.  It was very shortly after that that we encountered the wake turbulence.  It rolled us first rapidly to the left.  Although I'm sure the first officer reacted; I immediately took the controls; applying full right aileron and maximum thrust.  The roll to the left stopped and was followed by a rapid roll back to the right; which continued well beyond 90 degrees despite full left aileron deflection.  The roll stopped and we returned to wings level; climbing.  I retracted the flaps to 20 degrees and reported to the tower that we were going around.  They instructed us to climb to 2500 and turn right to 200 and asked the reason for our go-around.  I continued cleaning up our configuration; retracting the landing gear and flaps; then asked the first officer how he was feeling.  He said he could take the controls; so I returned control to him; then signaled to our passengers that the situation was under control.  We were sent back to approach control; who gave us a turn to downwind and a descent; then cleared us for a visual approach.  We landed without further incident.As I reviewed this incident later and looked at the airport diagram for the Anchorage airport; I came to the conclusion that it is not possible to follow a heavy aircraft in this situation with anything less than standard radar separation.  Because of the way the runways are staggered; effectively applying normal visual wake turbulence avoidance procedures produces a highly abnormal and potentially hazardous situation even if the wake turbulence is successfully avoided.Runway 7R is 12;400 feet long.  The threshold for runway 7L; just estimating from the airport diagram; is roughly 6;000 feet beyond the threshold for 7R.  If the heavy aircraft lands 1000 feet beyond the threshold for 7L; and we plan to land 1;000 feet beyond that; it leaves something slightly more than 4;000 feet of runway on which to stop.  While that is well within the capability of the Lear 31; landing on the last third of a runway is not something we would ever plan to do in any normal circumstance; and is well beyond what anyone would normally consider a long landing; as we were instructed by ATC to plan for.In future similar situations where normal visual wake turbulence avoidance is not practical; I think it would be advisable to request standard radar separation before accepting a visual approach in order to ensure there is sufficient time for the wake turbulence to dissipate.  It seems to me that ATC should really be aware of this situation as well in order to avoid placing lighter aircraft in a position where following a heavy aircraft is practically not possible.




Synopsis: LJ31 Captain reported encountering wake turbulence while on approach to ANC Runway 7R. Reporter was in trail of a B777 landing on 7L; which resulted in an uncommanded roll 'well beyond 90 degrees'. Reporter recommended ATC be more aware of the wake possibilities when using this runway configuration.