<< >> NASA ASRS Report 579359, April 2003

MD80 experienced multiple TCASII RA's in quick succession while operating in mixed IFR VFR class east airspace.

Attributes
ACN	579359
Time
Date	200304
Day	Wed
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : acy.vortac
State Reference	NJ
Altitude	msl bound lower : 16400 msl bound upper : 17000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc.artcc tower : den.tower
Operator	common carrier : air carrier
Make Model Name	MD-88
Operating Under FAR Part	Part 121
Flight Phase	cruise : level
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : pct.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	cruise : level
Flight Plan	VFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 160 flight time total : 15250 flight time type : 4300
ASRS Report	579359
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne critical non adherence : required legal separation
Independent Detector	aircraft equipment : tcas other flight crewa
Resolutory Action	flight crew : took evasive action
Supplementary
Problem Areas	ATC Human Performance Airspace Structure Flight Crew Human Performance
Primary Problem	Airspace Structure

Narrative:

We were at 17000 ft, level flight cruise on ZDC, south of acy VOR. Previous to this, we noticed a target at 500 ft below us, our 11-10 O'clock position, that went to a TA. I asked center about it. They said 'oh yes, there is VFR traffic.' we continued. The traffic seemed to be maneuvering because of the variation from 600-400 ft below with a vector. Then it went to an RA 'monitor vertical speed,' then 'descend.' the first officer flew it on the autoplt to descend. We were a little confused about a descent when the target had an up vector, but we complied. Our descent took us down to 16400 ft MSL. While in the descent, we got an RA 'climb,' then 'monitor vertical speed' on another target at our 12-11 O'clock position. It showed 800 ft below at the time of the RA. Notified center of our deviation to which they said 'roger, how low did you have to go?' we said 16400 ft. In the future, I'll request an altitude higher than FL180 to avoid VFR traffic.

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Original NASA ASRS Text

Title: MD80 EXPERIENCED MULTIPLE TCASII RA'S IN QUICK SUCCESSION WHILE OPERATING IN MIXED IFR VFR CLASS E AIRSPACE.

Narrative: WE WERE AT 17000 FT, LEVEL FLT CRUISE ON ZDC, S OF ACY VOR. PREVIOUS TO THIS, WE NOTICED A TARGET AT 500 FT BELOW US, OUR 11-10 O'CLOCK POS, THAT WENT TO A TA. I ASKED CTR ABOUT IT. THEY SAID 'OH YES, THERE IS VFR TFC.' WE CONTINUED. THE TFC SEEMED TO BE MANEUVERING BECAUSE OF THE VARIATION FROM 600-400 FT BELOW WITH A VECTOR. THEN IT WENT TO AN RA 'MONITOR VERT SPD,' THEN 'DSND.' THE FO FLEW IT ON THE AUTOPLT TO DSND. WE WERE A LITTLE CONFUSED ABOUT A DSCNT WHEN THE TARGET HAD AN UP VECTOR, BUT WE COMPLIED. OUR DSCNT TOOK US DOWN TO 16400 FT MSL. WHILE IN THE DSCNT, WE GOT AN RA 'CLB,' THEN 'MONITOR VERT SPD' ON ANOTHER TARGET AT OUR 12-11 O'CLOCK POS. IT SHOWED 800 FT BELOW AT THE TIME OF THE RA. NOTIFIED CTR OF OUR DEV TO WHICH THEY SAID 'ROGER, HOW LOW DID YOU HAVE TO GO?' WE SAID 16400 FT. IN THE FUTURE, I'LL REQUEST AN ALT HIGHER THAN FL180 TO AVOID VFR TFC.

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.