Landing B757 possible wake turbulence encounter from departing B757.

Attributes
ACN	284580
Time
Date	199409
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : dca
State Reference	DC
Altitude	agl bound lower : 0 agl bound upper : 0
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : dca tower : ckb
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	landing other
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : takeoff
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 17000 flight time type : 800
ASRS Report	284580
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	other anomaly other
Independent Detector	other flight crewa
Resolutory Action	none taken : anomaly accepted
Consequence	Other
Miss Distance	horizontal : 15000
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

Air carrier X on a final approach to runway 36 at kdca, approximately a 2 1/2 mi final approach, the tower cleared a B-757 for takeoff. While this, in itself is not unusual, the possibility of encountering the 'wake' from the departing B-757, should be considered by ATC. As we 'crossed the fence,' I believe that we encountered 'wake' requiring a substantial power application to correct. Although the aircraft landing was a normal, uneventful one, it may have resulted in a hard landing in another set of circumstances. I recommended that ATC, not clear a B-757 'heavy' aircraft, for takeoff, when aircraft are within a 4 mi final.

Original NASA ASRS Text

Title: LNDG B757 POSSIBLE WAKE TURB ENCOUNTER FROM DEPARTING B757.

Narrative: ACR X ON A FINAL APCH TO RWY 36 AT KDCA, APPROX A 2 1/2 MI FINAL APCH, THE TWR CLRED A B-757 FOR TKOF. WHILE THIS, IN ITSELF IS NOT UNUSUAL, THE POSSIBILITY OF ENCOUNTERING THE 'WAKE' FROM THE DEPARTING B-757, SHOULD BE CONSIDERED BY ATC. AS WE 'CROSSED THE FENCE,' I BELIEVE THAT WE ENCOUNTERED 'WAKE' REQUIRING A SUBSTANTIAL PWR APPLICATION TO CORRECT. ALTHOUGH THE ACFT LNDG WAS A NORMAL, UNEVENTFUL ONE, IT MAY HAVE RESULTED IN A HARD LNDG IN ANOTHER SET OF CIRCUMSTANCES. I RECOMMENDED THAT ATC, NOT CLR A B-757 'HEAVY' ACFT, FOR TKOF, WHEN ACFT ARE WITHIN A 4 MI FINAL.

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.