An MD80 pilot comments that because the FMC uses 25-30 degree bank angles at altitude; he selects heading for course changes and in this case subsequently got off track when he failed to rearm navigation.

Home

Browse by month

Random

Latest

About

Contact

Attributes
ACN	705462
Time
Date	200608
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : lit.vortac
State Reference	AR
Altitude	msl single value : 36000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zfw.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : level
Route In Use	enroute : direct enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
ASRS Report	705462
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Events
Anomaly	aircraft equipment problem : less severe non adherence : clearance other spatial deviation
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended or assigned course
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance

Narrative:

We were given a vector for traffic and then reclred direct to lit. I started a turn using heading select and reselected lit on the FMS. However; I failed to rearm navigation and thus continued toward lit in heading select. As we neared lit; I noticed we were off course somewhat and entered a heading correction. Shortly thereafter; center cleared us direct to the next point beyond lit. No conflicts resulted. This happens for 2 reasons: 1) the angle of bank used by the system is too great in cruise -- 25-30 degrees. Therefore; you must use heading select first and then remember to arm navigation as you approach direct. 2) in my mind at least; the selection of the point on the FMS control panel seems to satisfy my brain. It is easy to forget to rearm the navigation. Of course; a more careful xchk wouldn't hurt either. I would strongly recommend reducing angle of bank used in cruise by the system for such turns. I have heard this was in the works for yrs. I hear many other pilots say they have made the same mistake.

Original NASA ASRS Text

Title: AN MD80 PLT COMMENTS THAT BECAUSE THE FMC USES 25-30 DEG BANK ANGLES AT ALT; HE SELECTS HDG FOR COURSE CHANGES AND IN THIS CASE SUBSEQUENTLY GOT OFF TRACK WHEN HE FAILED TO REARM NAV.

Narrative: WE WERE GIVEN A VECTOR FOR TFC AND THEN RECLRED DIRECT TO LIT. I STARTED A TURN USING HDG SELECT AND RESELECTED LIT ON THE FMS. HOWEVER; I FAILED TO REARM NAV AND THUS CONTINUED TOWARD LIT IN HDG SELECT. AS WE NEARED LIT; I NOTICED WE WERE OFF COURSE SOMEWHAT AND ENTERED A HDG CORRECTION. SHORTLY THEREAFTER; CTR CLRED US DIRECT TO THE NEXT POINT BEYOND LIT. NO CONFLICTS RESULTED. THIS HAPPENS FOR 2 REASONS: 1) THE ANGLE OF BANK USED BY THE SYS IS TOO GREAT IN CRUISE -- 25-30 DEGS. THEREFORE; YOU MUST USE HDG SELECT FIRST AND THEN REMEMBER TO ARM NAV AS YOU APCH DIRECT. 2) IN MY MIND AT LEAST; THE SELECTION OF THE POINT ON THE FMS CTL PANEL SEEMS TO SATISFY MY BRAIN. IT IS EASY TO FORGET TO REARM THE NAV. OF COURSE; A MORE CAREFUL XCHK WOULDN'T HURT EITHER. I WOULD STRONGLY RECOMMEND REDUCING ANGLE OF BANK USED IN CRUISE BY THE SYS FOR SUCH TURNS. I HAVE HEARD THIS WAS IN THE WORKS FOR YRS. I HEAR MANY OTHER PLTS SAY THEY HAVE MADE THE SAME MISTAKE.

Data retrieved from NASA's ASRS site as of January 2009 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.