<< >> NASA ASRS Report 318070, October 1995

Evasive action descent. Air carrier in holding receives an RA when a higher aircraft descends to the altitude 1000 ft above them at a high rate of descent.

Attributes
ACN	318070
Time
Date	199510
Day	Wed
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : eau
State Reference	WI
Altitude	msl bound lower : 25800 msl bound upper : 26000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Controlling Facilities	artcc : zmp
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Flight Phase	other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : instrument pilot : flight engineer pilot : atp pilot : cfi pilot : commercial
Experience	flight time last 90 days : 60 flight time total : 16000 flight time type : 2000
ASRS Report	318070
Person 2
Affiliation	company : air carrier
Function	flight crew : second officer
Qualification	pilot : atp pilot : flight engineer
Experience	flight time last 90 days : 200 flight time total : 6500 flight time type : 200
ASRS Report	318234
Events
Anomaly	altitude deviation : excursion from assigned altitude other anomaly other
Independent Detector	aircraft equipment other aircraft equipment : unspecified other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course flight crew : took evasive action other
Consequence	Other
Miss Distance	vertical : 1200
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	other

Narrative:

Holding at eau VOR on 123 degree radial at FL260. While level at FL260 and turning inbound to intercept the holding radial, we received a 'descend now' TCASII RA. Intruding aircraft was spotted during evasive maneuvering. Descent was initiated to 200 ft below assigned FL260. TCASII then issued a 'monitor descent' warning. A return to assigned altitude was accomplished and ATC advised of both TCASII RA and descent below assigned flight level. Without question this RA occurrence was a result of the aircraft 1000 ft above us, also in holding. He was assigned a descent to FL270. We had spotted him and noted his high descent rate. Accordingly, the TCASII RA was issued and we complied. During the maneuver, we visually spotted the 'intruder' aircraft and as noted by TCASII his altitude never penetrated our 1000 ft separation. However, his apparent high rates of descent coupled with our close proximity triggered the TCASII RA -- another example of a 'bump' on TCASII. I can't stress the importance of limiting rates of descent to no more than 1000 FPM while in holding in close proximity to other aircraft.

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Original NASA ASRS Text

Title: EVASIVE ACTION DSCNT. ACR IN HOLDING RECEIVES AN RA WHEN A HIGHER ACFT DSNDS TO THE ALT 1000 FT ABOVE THEM AT A HIGH RATE OF DSCNT.

Narrative: HOLDING AT EAU VOR ON 123 DEG RADIAL AT FL260. WHILE LEVEL AT FL260 AND TURNING INBOUND TO INTERCEPT THE HOLDING RADIAL, WE RECEIVED A 'DSND NOW' TCASII RA. INTRUDING ACFT WAS SPOTTED DURING EVASIVE MANEUVERING. DSCNT WAS INITIATED TO 200 FT BELOW ASSIGNED FL260. TCASII THEN ISSUED A 'MONITOR DSCNT' WARNING. A RETURN TO ASSIGNED ALT WAS ACCOMPLISHED AND ATC ADVISED OF BOTH TCASII RA AND DSCNT BELOW ASSIGNED FLT LEVEL. WITHOUT QUESTION THIS RA OCCURRENCE WAS A RESULT OF THE ACFT 1000 FT ABOVE US, ALSO IN HOLDING. HE WAS ASSIGNED A DSCNT TO FL270. WE HAD SPOTTED HIM AND NOTED HIS HIGH DSCNT RATE. ACCORDINGLY, THE TCASII RA WAS ISSUED AND WE COMPLIED. DURING THE MANEUVER, WE VISUALLY SPOTTED THE 'INTRUDER' ACFT AND AS NOTED BY TCASII HIS ALT NEVER PENETRATED OUR 1000 FT SEPARATION. HOWEVER, HIS APPARENT HIGH RATES OF DSCNT COUPLED WITH OUR CLOSE PROX TRIGGERED THE TCASII RA -- ANOTHER EXAMPLE OF A 'BUMP' ON TCASII. I CAN'T STRESS THE IMPORTANCE OF LIMITING RATES OF DSCNT TO NO MORE THAN 1000 FPM WHILE IN HOLDING IN CLOSE PROX TO OTHER ACFT.

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.