Wake turbulence -- on approach.

Attributes
ACN	300833
Time
Date	199503
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : sfo
State Reference	CA
Altitude	msl bound lower : 4000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : oak
Operator	common carrier : air carrier
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	DC-10 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	descent : approach
Route In Use	approach : visual
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : flight engineer pilot : instrument
Experience	flight time last 90 days : 60 flight time total : 2500 flight time type : 60
ASRS Report	300833
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 : regained aircraft control
Consequence	Other
Supplementary
Air Traffic Incident	other

Narrative:

On the quiet bridge visual to runway 28R into sfo following a DC10 we were restr to 170 KTS behind the DC10. Precautions taken: I flew the GS 1 DOT and 1/2 high which exceeds all altitudes for crossing restrs and would have provided adequate protection. At 4000 ft we encountered wake with about a 20-25 degrees roll to the right. It was obvious that the other aircraft was too high for profile. My captain concurred that my precautions were more than adequate and that we were within the limits specified for airspeed by our controller. The main factor was that the preceding aircraft was too high and needed to conform to the profile. Callback conversation with reporter revealed the following: the reporter states that he did all of the recommended procedures to avoid the wake encounter. However, the preceding dc-10 also was high on the GS. The 4 mi separation was not enough in his opinion and the widebody transport should have been on the GS. The result of the encounter was a controllable roll of 20/25 degrees to the right. The reporter continued the approach.

Original NASA ASRS Text

Title: WAKE TURB -- ON APCH.

Narrative: ON THE QUIET BRIDGE VISUAL TO RWY 28R INTO SFO FOLLOWING A DC10 WE WERE RESTR TO 170 KTS BEHIND THE DC10. PRECAUTIONS TAKEN: I FLEW THE GS 1 DOT AND 1/2 HIGH WHICH EXCEEDS ALL ALTS FOR XING RESTRS AND WOULD HAVE PROVIDED ADEQUATE PROTECTION. AT 4000 FT WE ENCOUNTERED WAKE WITH ABOUT A 20-25 DEGS ROLL TO THE R. IT WAS OBVIOUS THAT THE OTHER ACFT WAS TOO HIGH FOR PROFILE. MY CAPT CONCURRED THAT MY PRECAUTIONS WERE MORE THAN ADEQUATE AND THAT WE WERE WITHIN THE LIMITS SPECIFIED FOR AIRSPD BY OUR CTLR. THE MAIN FACTOR WAS THAT THE PRECEDING ACFT WAS TOO HIGH AND NEEDED TO CONFORM TO THE PROFILE. CALLBACK CONVERSATION WITH REPORTER REVEALED THE FOLLOWING: THE RPTR STATES THAT HE DID ALL OF THE RECOMMENDED PROCS TO AVOID THE WAKE ENCOUNTER. HOWEVER, THE PRECEDING DC-10 ALSO WAS HIGH ON THE GS. THE 4 MI SEPARATION WAS NOT ENOUGH IN HIS OPINION AND THE WDB SHOULD HAVE BEEN ON THE GS. THE RESULT OF THE ENCOUNTER WAS A CONTROLLABLE ROLL OF 20/25 DEGS TO THE R. THE RPTR CONTINUED THE APCH.

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.