Altitude deviation on STAR descent.

Attributes
ACN	293420
Time
Date	199501
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : ard airport : lga
State Reference	PA
Altitude	msl bound lower : 15500 msl bound upper : 15500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	A320
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other arrival star : star enroute airway : zny
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 550 flight time total : 10500 flight time type : 3000
ASRS Report	293420
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : undershoot altitude deviation : crossing restriction not met non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	none taken : detected after the fact other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We had been given a crossing restr on the arrival into lga by ZNY. The restr was to cross somto intersection at 13000 ft. I (being the PNF) had gotten the local ATIS which stated lda 'a' runway 22. The captain was relatively new (6 months) on the airplane and was interested in the proper way to enter this rather rarely used type of approach into the mcdu computer. A 'trap' in the A-320 is that when an approach or runway is entered into the destination page, it knocks out vertical navigation constraints entered by the pilot. This is what happened. He had properly entered 13000 ft at somto intersection in the vertical navigation portion of the computer. When I entered the landing runway it knocked out the vertical navigation constraint at somto intersection. He was busy watching me 'build' the approach for runway 22. I didn't notice the constraint was no longer in vertical navigation (it will remain under certain circumstances). While we were both involved in this task, we passed somto intersection at about 15500 ft. A few mi past, ATC asked our altitude. As I stated our altitude (15100 ft) I realized we had missed our crossing restr. I immediately asked ATC if it was a problem, that we had had a computer glitch and had missed somto intersection at 13000 ft. He said it was no problem and to just continue to 13000 ft. I feel 2 factors contributed to this incident. One is obviously the software in the present mcdu computer on the A-320, to knock out the vertical crossing constraint at times. The other is that there was a time when both of us were too involved inside the cockpit and not managing the airplane. Callback conversation with reporter revealed the following information: the reporter flies the a- 320 domestically for one of the major united states acrs. She has not heard from the FAA on this incident and was appropriately contrite when caught missing the crossing. She enjoys all of the 'gee whiz' parts of the A-320, but is concerned about her flying skills. She managed to get her captain checked out during the month.

Original NASA ASRS Text

Title: ALTDEV ON STAR DSCNT.

Narrative: WE HAD BEEN GIVEN A XING RESTR ON THE ARR INTO LGA BY ZNY. THE RESTR WAS TO CROSS SOMTO INTXN AT 13000 FT. I (BEING THE PNF) HAD GOTTEN THE LCL ATIS WHICH STATED LDA 'A' RWY 22. THE CAPT WAS RELATIVELY NEW (6 MONTHS) ON THE AIRPLANE AND WAS INTERESTED IN THE PROPER WAY TO ENTER THIS RATHER RARELY USED TYPE OF APCH INTO THE MCDU COMPUTER. A 'TRAP' IN THE A-320 IS THAT WHEN AN APCH OR RWY IS ENTERED INTO THE DEST PAGE, IT KNOCKS OUT VERT NAV CONSTRAINTS ENTERED BY THE PLT. THIS IS WHAT HAPPENED. HE HAD PROPERLY ENTERED 13000 FT AT SOMTO INTXN IN THE VERT NAV PORTION OF THE COMPUTER. WHEN I ENTERED THE LNDG RWY IT KNOCKED OUT THE VERT NAV CONSTRAINT AT SOMTO INTXN. HE WAS BUSY WATCHING ME 'BUILD' THE APCH FOR RWY 22. I DIDN'T NOTICE THE CONSTRAINT WAS NO LONGER IN VERT NAV (IT WILL REMAIN UNDER CERTAIN CIRCUMSTANCES). WHILE WE WERE BOTH INVOLVED IN THIS TASK, WE PASSED SOMTO INTXN AT ABOUT 15500 FT. A FEW MI PAST, ATC ASKED OUR ALT. AS I STATED OUR ALT (15100 FT) I REALIZED WE HAD MISSED OUR XING RESTR. I IMMEDIATELY ASKED ATC IF IT WAS A PROB, THAT WE HAD HAD A COMPUTER GLITCH AND HAD MISSED SOMTO INTXN AT 13000 FT. HE SAID IT WAS NO PROB AND TO JUST CONTINUE TO 13000 FT. I FEEL 2 FACTORS CONTRIBUTED TO THIS INCIDENT. ONE IS OBVIOUSLY THE SOFTWARE IN THE PRESENT MCDU COMPUTER ON THE A-320, TO KNOCK OUT THE VERT XING CONSTRAINT AT TIMES. THE OTHER IS THAT THERE WAS A TIME WHEN BOTH OF US WERE TOO INVOLVED INSIDE THE COCKPIT AND NOT MANAGING THE AIRPLANE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR FLIES THE A- 320 DOMESTICALLY FOR ONE OF THE MAJOR UNITED STATES ACRS. SHE HAS NOT HEARD FROM THE FAA ON THIS INCIDENT AND WAS APPROPRIATELY CONTRITE WHEN CAUGHT MISSING THE XING. SHE ENJOYS ALL OF THE 'GEE WHIZ' PARTS OF THE A-320, BUT IS CONCERNED ABOUT HER FLYING SKILLS. SHE MANAGED TO GET HER CAPT CHKED OUT DURING THE MONTH.

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.