Wake turbulence - flight crew is vectored at an altitude to intercept the GS from below while follow...

Attributes
ACN	298831
Time
Date	199503
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : atl
State Reference	GA
Altitude	msl bound lower : 5000 msl bound upper : 5000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : atl tower : ord
Operator	common carrier : air carrier
Make Model Name	ATR 72
Operating Under FAR Part	Part 121
Navigation In Use	Other
Flight Phase	descent : approach
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 150 flight time total : 4000 flight time type : 800
ASRS Report	298831
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	inflight encounter other other anomaly other
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

While on approach to hartsfield (atlanta) we were given descent to 5000 ft. A B-727 was in front of us at 6000 ft. He was on final, we were on base. The controller told us about him. We responded that we had him in sight. We were cleared to follow him visually. My company procedures dictate that I use a localizer and GS when available. We were both (captain and I) expecting the wake since ATC for no apparent reason left this 727 1000 ft above us. The autoplt was flying. As we began descent down the GS we encountered the wake. We felt a bump followed by an uncommanded 20 degree roll to the right. The aircraft autoplt was disengaged by the captain and we quickly left the wake. The rest of the flight was uneventful. There was no reason the 727 should not have given a descent. I am aware of my aircraft's recent problems and must say ice had nothing whatsoever to do with it. There wasn't a cloud in the sky. We were told what we were following, but were never cautioned specifically about a wake. Callback conversation with reporter revealed the following: the reporter said that initially the crew lost control of the aircraft. They were on autoplt and the aircraft started rolling and the autoplt disconnected. Both pilots grabbed the control wheel, but the aircraft continued to roll in spite of full opposite (left) aileron. The roll stopped at about 20 degrees of right bank. The flight crew climbed slightly and rolled the wings level to recover. Afterwards the captain stayed 1 DOT high on the GS and they had no further encounters. The traffic pattern design at atl seems to be the primary factor in this and a previously reported wake encounter according to the reporter. The approach controllers put aircraft at several different altitudes in the pattern going to the same runway. The arrival sector seems to be the determinate for the altitude selected. The reporter suggests that once terrain considerations are satisfied that the controllers should either put all aircraft at the same level or put the heavy aircraft below the lighter aircraft when possible.

Original NASA ASRS Text

Title: WAKE TURB - FLC IS VECTORED AT AN ALT TO INTERCEPT THE GS FROM BELOW WHILE FOLLOWING A HEAVIER ACFT 3 MI AHEAD. THEY TEMPORARILY LOSE CTL OF THEIR ACFT WHEN THEY ENCOUNTER THE WAKE.

Narrative: WHILE ON APCH TO HARTSFIELD (ATLANTA) WE WERE GIVEN DSCNT TO 5000 FT. A B-727 WAS IN FRONT OF US AT 6000 FT. HE WAS ON FINAL, WE WERE ON BASE. THE CTLR TOLD US ABOUT HIM. WE RESPONDED THAT WE HAD HIM IN SIGHT. WE WERE CLRED TO FOLLOW HIM VISUALLY. MY COMPANY PROCS DICTATE THAT I USE A LOC AND GS WHEN AVAILABLE. WE WERE BOTH (CAPT AND I) EXPECTING THE WAKE SINCE ATC FOR NO APPARENT REASON LEFT THIS 727 1000 FT ABOVE US. THE AUTOPLT WAS FLYING. AS WE BEGAN DSCNT DOWN THE GS WE ENCOUNTERED THE WAKE. WE FELT A BUMP FOLLOWED BY AN UNCOMMANDED 20 DEG ROLL TO THE R. THE ACFT AUTOPLT WAS DISENGAGED BY THE CAPT AND WE QUICKLY LEFT THE WAKE. THE REST OF THE FLT WAS UNEVENTFUL. THERE WAS NO REASON THE 727 SHOULD NOT HAVE GIVEN A DSCNT. I AM AWARE OF MY ACFT'S RECENT PROBS AND MUST SAY ICE HAD NOTHING WHATSOEVER TO DO WITH IT. THERE WASN'T A CLOUD IN THE SKY. WE WERE TOLD WHAT WE WERE FOLLOWING, BUT WERE NEVER CAUTIONED SPECIFICALLY ABOUT A WAKE. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTR SAID THAT INITIALLY THE CREW LOST CTL OF THE ACFT. THEY WERE ON AUTOPLT AND THE ACFT STARTED ROLLING AND THE AUTOPLT DISCONNECTED. BOTH PLTS GRABBED THE CTL WHEEL, BUT THE ACFT CONTINUED TO ROLL IN SPITE OF FULL OPPOSITE (L) AILERON. THE ROLL STOPPED AT ABOUT 20 DEGS OF R BANK. THE FLC CLBED SLIGHTLY AND ROLLED THE WINGS LEVEL TO RECOVER. AFTERWARDS THE CAPT STAYED 1 DOT HIGH ON THE GS AND THEY HAD NO FURTHER ENCOUNTERS. THE TFC PATTERN DESIGN AT ATL SEEMS TO BE THE PRIMARY FACTOR IN THIS AND A PREVIOUSLY RPTED WAKE ENCOUNTER ACCORDING TO THE RPTR. THE APCH CTLRS PUT ACFT AT SEVERAL DIFFERENT ALTS IN THE PATTERN GOING TO THE SAME RWY. THE ARR SECTOR SEEMS TO BE THE DETERMINATE FOR THE ALT SELECTED. THE RPTR SUGGESTS THAT ONCE TERRAIN CONSIDERATIONS ARE SATISFIED THAT THE CTLRS SHOULD EITHER PUT ALL ACFT AT THE SAME LEVEL OR PUT THE HVY ACFT BELOW THE LIGHTER ACFT WHEN POSSIBLE.

Data retrieved from NASA's ASRS site as of July 2007 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.

Wake turbulence - flight crew is vectored at an altitude to intercept the GS from below while following a heavier aircraft 3 mi ahead. They temporarily lose control of their aircraft when they encounter the wake.