Air carrier X possible less than standard separation behind B757. Possible system error.

Attributes
ACN	271402
Time
Date	199405
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : pit
State Reference	PA
Altitude	msl bound lower : 3000 msl bound upper : 3000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : pit
Operator	common carrier : air carrier
Make Model Name	Light Transport, Low Wing, 2 Turboprop Eng
Flight Phase	descent : approach landing : missed approach
Flight Plan	IFR
Aircraft 2
Operator	common carrier : air carrier
Make Model Name	Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 270 flight time total : 8100 flight time type : 1300
ASRS Report	271402
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	conflict : airborne less severe other anomaly other
Independent Detector	other flight crewa
Resolutory Action	other
Consequence	Other
Miss Distance	horizontal : 17000
Supplementary
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

As air carrier X I was vectored to less than 3 mi behind a B757 at the final approach fix and told to slow 30 KTS. I elected to go missed approach rather than risk a vortices encounter in IMC. This was caused by pittsburg's approach not providing proper separation. Pittsburgh approach repeatedly assigns airspds clears you for the approach several mi from the FAF and sends you to the tower. When you talk to tower you do not have proper separation to continue the approach and land. In this case, I was still in IMC and chose to go missed approach. Rather than destabilize the approach and possibly still encounter vortices.

Original NASA ASRS Text

Title: ACR X POSSIBLE LTSS BEHIND B757. POSSIBLE SYS ERROR.

Narrative: AS ACR X I WAS VECTORED TO LESS THAN 3 MI BEHIND A B757 AT THE FINAL APCH FIX AND TOLD TO SLOW 30 KTS. I ELECTED TO GO MISSED APCH RATHER THAN RISK A VORTICES ENCOUNTER IN IMC. THIS WAS CAUSED BY PITTSBURG'S APCH NOT PROVIDING PROPER SEPARATION. PITTSBURGH APCH REPEATEDLY ASSIGNS AIRSPDS CLRS YOU FOR THE APCH SEVERAL MI FROM THE FAF AND SENDS YOU TO THE TWR. WHEN YOU TALK TO TWR YOU DO NOT HAVE PROPER SEPARATION TO CONTINUE THE APCH AND LAND. IN THIS CASE, I WAS STILL IN IMC AND CHOSE TO GO MISSED APCH. RATHER THAN DESTABILIZE THE APCH AND POSSIBLY STILL ENCOUNTER VORTICES.

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.