GA-small transport altitude deviate excursion from clearance altitude.

Attributes
ACN	138988
Time
Date	199003
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : lhs
State Reference	CA
Altitude	msl bound lower : 16400 msl bound upper : 17000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zla tower : sle
Operator	general aviation : personal
Make Model Name	Small Transport, Low Wing, 2 Turboprop Eng
Flight Phase	cruise other descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument pilot : commercial
Experience	flight time last 90 days : 150 flight time total : 7500 flight time type : 450
ASRS Report	138988
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	other other : other
Experience	flight time last 90 days : 19 flight time total : 712 flight time type : 9
ASRS Report	139407
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While descend from fl 210 to 17000', lax center reclred descent to 13000'. Copilot was at controls. As we were descending thru 17300' lax center told us to level at 17000' due to traffic 'one to two O'clock, 10 mi at 16000''. We leveled at 18000' and approximately 30 seconds later, lax center advised 'I'll need you to expedite your descent to 13000' as soon as you are clear of traffic'. At this time, I reported the traffic in sight, however received no response from lax center. I reported traffic insight again and that we were clear of traffic. Lax center called back and told us to turn left to 140 degree for vectors around traffic. I was keeping watch on the traffic to the right side of our path as the copilot initiated the left turn to 140 degree. I estimate approximately 20 seconds had elapsed since the turn had been given when I looked back in at the instruments and found that the copilot had also begun an expedited descent. I took the controls as we were passing 16400' and returned the aircraft to 17000'. The copilot and I had a lengthy discussion during which I found out that the copilot thought center wanted us to expedite descent to 13000' as soon as we were clear of traffic, and since he knew we were clear, that is what he was doing. I explained to him that he could not climb or descend under IFR control until specifically cleared to do so by center. Further that what center had been doing was to advise us of expected future requirements. To my knowledge, no 'close calls' were encountered. In defense of lax center, they were quite busy with the 'sunday evening rush hour traffic' returning to the la area. Though I understood the unspoken 'expect' clearance, my copilot does not have the experience or the background to have known that the 'expect' was unspoken. The controllers in the system do an excellent job, but as a human make mistakes too. Their mistake was the absence of the word expect, mine was not being more vigilant. But overall, I think both pilots and controllers make an excellent team.

Original NASA ASRS Text

Title: GA-SMT ALT DEVIATE EXCURSION FROM CLRNC ALT.

Narrative: WHILE DSND FROM FL 210 TO 17000', LAX CENTER RECLRED DSCNT TO 13000'. COPLT WAS AT CONTROLS. AS WE WERE DSNDING THRU 17300' LAX CENTER TOLD US TO LEVEL AT 17000' DUE TO TFC 'ONE TO TWO O'CLOCK, 10 MI AT 16000''. WE LEVELED AT 18000' AND APPROX 30 SECS LATER, LAX CENTER ADVISED 'I'LL NEED YOU TO EXPEDITE YOUR DSCNT TO 13000' AS SOON AS YOU ARE CLR OF TFC'. AT THIS TIME, I RPTED THE TFC IN SIGHT, HOWEVER RECEIVED NO RESPONSE FROM LAX CENTER. I RPTED TFC INSIGHT AGAIN AND THAT WE WERE CLR OF TFC. LAX CENTER CALLED BACK AND TOLD US TO TURN L TO 140 DEG FOR VECTORS AROUND TFC. I WAS KEEPING WATCH ON THE TFC TO THE R SIDE OF OUR PATH AS THE COPLT INITIATED THE L TURN TO 140 DEG. I ESTIMATE APPROX 20 SECS HAD ELAPSED SINCE THE TURN HAD BEEN GIVEN WHEN I LOOKED BACK IN AT THE INSTRUMENTS AND FOUND THAT THE COPLT HAD ALSO BEGUN AN EXPEDITED DSCNT. I TOOK THE CONTROLS AS WE WERE PASSING 16400' AND RETURNED THE ACFT TO 17000'. THE COPLT AND I HAD A LENGTHY DISCUSSION DURING WHICH I FOUND OUT THAT THE COPLT THOUGHT CENTER WANTED US TO EXPEDITE DSCNT TO 13000' AS SOON AS WE WERE CLR OF TFC, AND SINCE HE KNEW WE WERE CLR, THAT IS WHAT HE WAS DOING. I EXPLAINED TO HIM THAT HE COULD NOT CLB OR DSND UNDER IFR CTL UNTIL SPECIFICALLY CLRED TO DO SO BY CENTER. FURTHER THAT WHAT CENTER HAD BEEN DOING WAS TO ADVISE US OF EXPECTED FUTURE REQUIREMENTS. TO MY KNOWLEDGE, NO 'CLOSE CALLS' WERE ENCOUNTERED. IN DEFENSE OF LAX CENTER, THEY WERE QUITE BUSY WITH THE 'SUNDAY EVENING RUSH HR TFC' RETURNING TO THE LA AREA. THOUGH I UNDERSTOOD THE UNSPOKEN 'EXPECT' CLRNC, MY COPLT DOES NOT HAVE THE EXPERIENCE OR THE BACKGROUND TO HAVE KNOWN THAT THE 'EXPECT' WAS UNSPOKEN. THE CTLRS IN THE SYS DO AN EXCELLENT JOB, BUT AS A HUMAN MAKE MISTAKES TOO. THEIR MISTAKE WAS THE ABSENCE OF THE WORD EXPECT, MINE WAS NOT BEING MORE VIGILANT. BUT OVERALL, I THINK BOTH PLTS AND CTLRS MAKE AN EXCELLENT TEAM.

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.