A DC9-50 ON A SHORT 'CHANNEL VISUAL' APCH ENCOUNTERS A ROLLING TENDENCY FROM THE PRECEDING B737 AHEAD. RPTR WAS CONCERNED THAT HE MAY HAVE EXCEEDED THE 30 DEG BANK ANGLE DURING THE WAKE TURB ENCOUNTER.
Synopsis
A DC9-50 ON A SHORT 'CHANNEL VISUAL' APCH ENCOUNTERS A ROLLING TENDENCY FROM THE PRECEDING B737 AHEAD. RPTR WAS CONCERNED THAT HE MAY HAVE EXCEEDED THE 30 DEG BANK ANGLE DURING THE WAKE TURB ENCOUNTER.
Narrative
OUR NORMAL VISUAL APCH CLRNC TO RWY 8L AT HNL WHEN ARRIVING FROM THE E IS CALLED THE 'CHANNEL VISUAL' WHICH INVOLVES FLYING A BASE LEG GND TRACK ALONG THE PEAR HARBOR SHIP CHANNEL TO A POINT WHERE A BASE TO FINAL TURN CAN BE MADE TO ALIGN WITH THE RWY. THE BASE LEG TRACK IS LESS THAN 350 DEGS WHICH REQUIRES A BASE TO FINAL TURN OF MORE THAN 90 DEGS. NORMALLY THIS IS NOT A PROB SINCE TYPICAL SURFACE WINDS PROVIDE QUARTERING HEADWINDS OF 12- 20 KTS OR MORE; RESULTING IN A RELATIVELY SLOW GND SPD SO THAT ANGLES OF BANK OF 15-20 DEGS ARE USUALLY ADEQUATE TO FLY THIS PATTERN. ON THE DAY IN QUESTION; WINDS WERE RPTED CALM. THIS CONDITION NECESSITATED FLYING THE APCH AT MAX PERMITTED ANGLES OF BANK (30 DEGS) RELATIVELY CLOSE TO THE GND AND AT HIGHER THAN NORMAL GND SPDS. HNL TWR ASKED THAT WE MAKE A CLOSE APCH BEHIND ANOTHER LNDG ACFT TO FACILITATE OTHER LNDGS AND DEPS. DUE TO CALM WINDS AND MINIMUM SEPARATION WE ENCOUNTERED DISTURBED AIR FROM THE PRECEDING ACFT ON THE BASE TO FINAL TURN UNDER 1000 FT AGL WHICH ROLLED OUR ACFT FIRST ONE DIRECTION AND THEN THE OTHER. I DID NOT OBSERVE A BANK ANGLE OF GREATER THAN 30 DEGS DURING THIS ENCOUNTER THOUGH THE ACFT MAY HAVE EXCEEDED THIS LIMIT MOMENTARILY. THE ENCOUNTER LASTED ONLY A SECOND OR TWO AND WAS EASILY CORRECTED FOR BY THE PF. HOWEVER; THE CORRECTION RESULTED IN A ROLLOUT TO FINAL WHICH WAS SLIGHTLY OVERSHOT NECESSITATING A FURTHER CORRECTION TO REALIGN WITH THE RWY. IN THE LNDG FLARE WE ENCOUNTERED MORE DISTURBED AIR FROM THE PRECEDING ACFT RESULTING IN SOME WING ROCKING WHICH WAS EASILY COUNTERED. THE SUBSEQUENT LNDG AND ROLLOUT WAS VERY SMOOTH. AS WE WERE DEPLANING; I OVERHEARD ONE PAX REMARK TO FLT ATTENDANT THAT HE WAS FRIGHTENED BY THE LNDG. I CAN APPRECIATE THAT THE LOW ALT COMBINED WITH SLIGHTLY HIGHER THAN NORMAL BANK ANGLES AND GND SPDS; ESPECIALLY WHEN VIEWED FROM THE PAX CABIN COULD HAVE LEFT THE IMPRESSION OF A SCARY APCH AND LNDG. HOWEVER; AT NO TIME DID WE INTEND TO OPERATE THE ACFT OUTSIDE OF ESTABLISHED PARAMETERS AND ANY INADVERTENT DEVS WERE IMMEDIATELY AND SAFELY CORRECTED. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE CAPT SAID THAT HE WAS JUST AS MUCH CONCERNED WITH THE PAX'S RESPONSE AS HE WAS WITH THE POSSIBILITY THAT HE HAD EXCEEDED THE 30 DEG BANK OF TURN DURING THE WAKE ENCOUNTER. THERE WASN'T ANY PROB WITH RECOVERING CTL OF THE ACFT. THE INITIAL ROLL SEEMED TO EXACERBATE THE DEGS OF BANK AS THE ACFT ROLLED INTO THE DOWN SIDE WING. THE CAPT THOUGHT THAT THE ENCOUNTER OCCURRED BECAUSE HIS ACFT FLEW THE SAME PATH THAT THE B737 FLEW AND THE LIGHT WINDS; 4 KTS FROM 075 DEGS TO CALM; DID NOT ALLOW THE WAKE VORTEX TO DISSIPATE. HE HAD BEEN ASKED TO EXPEDITE HIS APCH; TURNING A SHORTER FINAL THAN NORMALLY FLOWN. HNL ATC LIKES TO USE THIS VISUAL FOR 'MOVING TFC' AND USES IT UP TO XA00 AT NIGHT FOR NOISE ABATEMENT PURPOSES. CAPT SAID THAT HE WOULD NOT ACCEPT AN EXPEDITED APCH FROM ATC WITH LIGHT WINDS AND JUST A 3 MI SEPARATION.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.