MD88 crew has FMS map failure during dylin 2 arrival to ewr that causes altitude bust at dqo.

Attributes
ACN	727201
Time
Date	200702
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : dqo.vortac
State Reference	DE
Altitude	msl single value : 20000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdc.artcc
Operator	common carrier : air carrier
Make Model Name	MD-88
Operating Under FAR Part	Part 121
Flight Plan	IFR
Aircraft 2
Flight Phase	descent : approach
Route In Use	arrival star : dylin2
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : flight engineer pilot : multi engine pilot : instrument pilot : commercial pilot : atp
Experience	flight time last 90 days : 135 flight time total : 14000 flight time type : 1300
ASRS Report	727201
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp pilot : cfi pilot : flight engineer
Experience	flight time last 90 days : 180 flight time total : 6850 flight time type : 1760
ASRS Report	727209
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : crossing restriction not met altitude deviation : overshoot non adherence : clearance non adherence : published procedure
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft

Narrative:

Cleared to descend via DYLIN2 arrival out of FL270. Restr at dqo FL200. During descent FMS fail; map fail; VNAV fail; FMS perf init data dumped. No warning -- aircraft began rapid descent; pilots noted descent; tried to correct via autoplt; aircraft response too slow; pilot turned off autoplt approximately FL202; level FL193 about 10 NM southwest dqo. Pilot returned to FL200 -- notified ZDC. I have received no training to recover from this type of system failure. This happened very quickly! Callback conversation with reporter revealed the following information: normal procedure for MD88 crews is to turn on the electric hydraulic pump during the descent for landing. This pump has a high electrical power requirement; and normally causes the flight displays and the FMS to blank momentarily when it is turned on. When the pump was turned on this time; the blanking seemed to last longer than normal and the FMS did not recover.

Original NASA ASRS Text

Title: MD88 CREW HAS FMS MAP FAILURE DURING DYLIN 2 ARR TO EWR THAT CAUSES ALT BUST AT DQO.

Narrative: CLRED TO DSND VIA DYLIN2 ARR OUT OF FL270. RESTR AT DQO FL200. DURING DSCNT FMS FAIL; MAP FAIL; VNAV FAIL; FMS PERF INIT DATA DUMPED. NO WARNING -- ACFT BEGAN RAPID DSCNT; PLTS NOTED DSCNT; TRIED TO CORRECT VIA AUTOPLT; ACFT RESPONSE TOO SLOW; PLT TURNED OFF AUTOPLT APPROX FL202; LEVEL FL193 ABOUT 10 NM SW DQO. PLT RETURNED TO FL200 -- NOTIFIED ZDC. I HAVE RECEIVED NO TRAINING TO RECOVER FROM THIS TYPE OF SYS FAILURE. THIS HAPPENED VERY QUICKLY! CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: NORMAL PROC FOR MD88 CREWS IS TO TURN ON THE ELECTRIC HYD PUMP DURING THE DSCNT FOR LNDG. THIS PUMP HAS A HIGH ELECTRICAL PWR REQUIREMENT; AND NORMALLY CAUSES THE FLT DISPLAYS AND THE FMS TO BLANK MOMENTARILY WHEN IT IS TURNED ON. WHEN THE PUMP WAS TURNED ON THIS TIME; THE BLANKING SEEMED TO LAST LONGER THAN NORMAL AND THE FMS DID NOT RECOVER.

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.