<< >> NASA ASRS Report 587546, July 2003

Altitude excursion during a single pilot operation in a B737, first officer being advised by ATC of incorrect climb clearance, 100 NM west of lbb, NM.

Attributes
ACN	587546
Time
Date	200307
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : lbb.vortac
State Reference	NM
Altitude	msl bound lower : 35000 msl bound upper : 36500
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zab.artcc
Operator	common carrier : air carrier
Make Model Name	B737-700
Operating Under FAR Part	Part 121
Flight Phase	cruise : enroute altitude change cruise : level
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Experience	flight time last 90 days : 215 flight time total : 4600 flight time type : 1635
ASRS Report	587546
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Experience	flight time last 90 days : 139 flight time total : 18000 flight time type : 14000
ASRS Report	587547
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance other anomaly other
Independent Detector	atc equipment other atc equipment : mode c other controllera
Resolutory Action	controller : issued advisory flight crew : became reoriented flight crew : returned to assigned altitude
Consequence	Other
Supplementary
Problem Areas	Environmental Factor ATC Human Performance Flight Crew Human Performance
Primary Problem	Ambiguous

Narrative:

In cruise flight at FL350, it was actually the captain's leg, but I was in full control since the captain had to excuse himself. Seconds after he left the cockpit, center called assigning FL370 as our new altitude. I acknowledged the call and began a climb. Passing through approximately FL365, center called asking what our altitude was. I responded adding that we had been cleared to FL370. The controller said that there must have been a mistake and cleared us back to FL350. I complied, and the aircraft was reestablished in cruise back at FL350 by the time the captain returned from the toilet. Contributing factors: at the time center made the clearance call, I was still fussing with my oxygen mask. It was on as required, but I was preoccupied with trying to get it adjusted since it was interfering with my boom ear piece. Unrealized at the time, center was also working a similar sounding flight number. Center may have given the altitude clearance using the wrong flight number. On the other hand, though I obviously did not think so at the time, it's entirely possible that I responded to a clearance meant for the other flight number. In hindsight, I should have questioned the wrong-way altitude. According to our flight plan, I knew we needed to climb to FL390, but we hadn't made the request yet.

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Original NASA ASRS Text

Title: ALT EXCURSION DURING A SINGLE PLT OP IN A B737, FO BEING ADVISED BY ATC OF INCORRECT CLB CLRNC, 100 NM W OF LBB, NM.

Narrative: IN CRUISE FLT AT FL350, IT WAS ACTUALLY THE CAPT'S LEG, BUT I WAS IN FULL CTL SINCE THE CAPT HAD TO EXCUSE HIMSELF. SECONDS AFTER HE LEFT THE COCKPIT, CTR CALLED ASSIGNING FL370 AS OUR NEW ALT. I ACKNOWLEDGED THE CALL AND BEGAN A CLB. PASSING THROUGH APPROX FL365, CTR CALLED ASKING WHAT OUR ALT WAS. I RESPONDED ADDING THAT WE HAD BEEN CLRED TO FL370. THE CTLR SAID THAT THERE MUST HAVE BEEN A MISTAKE AND CLRED US BACK TO FL350. I COMPLIED, AND THE ACFT WAS REESTABLISHED IN CRUISE BACK AT FL350 BY THE TIME THE CAPT RETURNED FROM THE TOILET. CONTRIBUTING FACTORS: AT THE TIME CTR MADE THE CLRNC CALL, I WAS STILL FUSSING WITH MY OXYGEN MASK. IT WAS ON AS REQUIRED, BUT I WAS PREOCCUPIED WITH TRYING TO GET IT ADJUSTED SINCE IT WAS INTERFERING WITH MY BOOM EAR PIECE. UNREALIZED AT THE TIME, CTR WAS ALSO WORKING A SIMILAR SOUNDING FLT NUMBER. CTR MAY HAVE GIVEN THE ALT CLRNC USING THE WRONG FLT NUMBER. ON THE OTHER HAND, THOUGH I OBVIOUSLY DID NOT THINK SO AT THE TIME, IT'S ENTIRELY POSSIBLE THAT I RESPONDED TO A CLRNC MEANT FOR THE OTHER FLT NUMBER. IN HINDSIGHT, I SHOULD HAVE QUESTIONED THE WRONG-WAY ALT. ACCORDING TO OUR FLT PLAN, I KNEW WE NEEDED TO CLB TO FL390, BUT WE HADN'T MADE THE REQUEST YET.

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.