A flight crew failed to comply with a SID turn radius restr, when departing chicago midway. The FMS,...

Attributes
ACN	300192
Time
Date	199503
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mdw
State Reference	IL
Altitude	msl bound lower : 2500 msl bound upper : 2500
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : ord
Operator	common carrier : air carrier
Make Model Name	B757 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	climbout : initial
Route In Use	departure other departure sid : sid
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : cfi pilot : commercial
Experience	flight time last 90 days : 150 flight time total : 12500 flight time type : 300
ASRS Report	300192
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe non adherence : published procedure non adherence : clearance other anomaly other other anomaly other other spatial deviation
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : overcame equipment problem none taken : anomaly accepted other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Clearance was mdw 4 departure, with an ATC assigned heading of 260 degree, left turn on departure from runway 04R. WX was approximately 3000 ft overcast, winds (tower) were 100 degree, gusting to 25 KTS on arrival 2 hours prior, INS winds (on approach) were 40 KTS at 1000 ft AGL, however, turbulence was light, at that time. Departure proceeded normally until FMS went to altitude capture mode at approximately 2500 ft MSL. First officer was at controls and first officer's flight director lessened the bank angle from 30 degree to 10 degree. I noticed the shallowing of the turn and compared my flight director, which indicated a standard left turn command. At this time, ord ATC sternly called for an increase in bank. Turbulence was moderate and the radar indicated level 3 returns, we were, also, in very heavy rain and workload was high, to keep aircraft under control. The autoplt was disconnected and first officer disregarded command bars and increased bank angle. The autothrottles started surging due to the wide airspeed variations, and we had to disconnect. ATC apparently had traffic and was yelling at us (remember the 4 mi radius restr) but we could not safely increase bank angle beyond 30 degrees due to the turbulence. We stated this to ATC, but he told us (correctly) that we had to inform before departure if restr couldn't be made, etc, we were given a climb to 4000 ft, and I selected VNAV for climb, however altitude hold remained engaged also, and neither mode would de-select. First officer's flight director was commanding a shallow bank and descent, while mine was giving correct indications. We selected the center flight director on first officer's side and problem was corrected. The airspace problem was a combination of an equipment failure and winds, turbulence, a narrow turn radius and problem resolution time (recognition), all at the most inopportune time. First officer, in my opinion, performed the correct action of disengaging the autoflt and ignoring an erroneous command bar.

Original NASA ASRS Text

Title: A FLC FAILED TO COMPLY WITH A SID TURN RADIUS RESTR, WHEN DEPARTING CHICAGO MIDWAY. THE FMS, AND IT'S ASSOCIATED FLT DIRECTOR COMMANDS, WERE ILLOGICAL.

Narrative: CLRNC WAS MDW 4 DEP, WITH AN ATC ASSIGNED HDG OF 260 DEG, L TURN ON DEP FROM RWY 04R. WX WAS APPROX 3000 FT OVCST, WINDS (TWR) WERE 100 DEG, GUSTING TO 25 KTS ON ARR 2 HRS PRIOR, INS WINDS (ON APCH) WERE 40 KTS AT 1000 FT AGL, HOWEVER, TURB WAS LIGHT, AT THAT TIME. DEP PROCEEDED NORMALLY UNTIL FMS WENT TO ALT CAPTURE MODE AT APPROX 2500 FT MSL. FO WAS AT CTLS AND FO'S FLT DIRECTOR LESSENED THE BANK ANGLE FROM 30 DEG TO 10 DEG. I NOTICED THE SHALLOWING OF THE TURN AND COMPARED MY FLT DIRECTOR, WHICH INDICATED A STANDARD L TURN COMMAND. AT THIS TIME, ORD ATC STERNLY CALLED FOR AN INCREASE IN BANK. TURB WAS MODERATE AND THE RADAR INDICATED LEVEL 3 RETURNS, WE WERE, ALSO, IN VERY HVY RAIN AND WORKLOAD WAS HIGH, TO KEEP ACFT UNDER CTL. THE AUTOPLT WAS DISCONNECTED AND FO DISREGARDED COMMAND BARS AND INCREASED BANK ANGLE. THE AUTOTHROTTLES STARTED SURGING DUE TO THE WIDE AIRSPD VARIATIONS, AND WE HAD TO DISCONNECT. ATC APPARENTLY HAD TFC AND WAS YELLING AT US (REMEMBER THE 4 MI RADIUS RESTR) BUT WE COULD NOT SAFELY INCREASE BANK ANGLE BEYOND 30 DEGS DUE TO THE TURB. WE STATED THIS TO ATC, BUT HE TOLD US (CORRECTLY) THAT WE HAD TO INFORM BEFORE DEP IF RESTR COULDN'T BE MADE, ETC, WE WERE GIVEN A CLB TO 4000 FT, AND I SELECTED VNAV FOR CLB, HOWEVER ALT HOLD REMAINED ENGAGED ALSO, AND NEITHER MODE WOULD DE-SELECT. FO'S FLT DIRECTOR WAS COMMANDING A SHALLOW BANK AND DSCNT, WHILE MINE WAS GIVING CORRECT INDICATIONS. WE SELECTED THE CTR FLT DIRECTOR ON FO'S SIDE AND PROB WAS CORRECTED. THE AIRSPACE PROB WAS A COMBINATION OF AN EQUIP FAILURE AND WINDS, TURB, A NARROW TURN RADIUS AND PROB RESOLUTION TIME (RECOGNITION), ALL AT THE MOST INOPPORTUNE TIME. FO, IN MY OPINION, PERFORMED THE CORRECT ACTION OF DISENGAGING THE AUTOFLT AND IGNORING AN ERRONEOUS COMMAND BAR.

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.

A flight crew failed to comply with a SID turn radius restr, when departing chicago midway. The FMS, and it's associated flight director commands, were illogical.