Pilot allowed aircraft to descend below assigned altitude.

Attributes
ACN	82195
Time
Date	198802
Day	Fri
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : hvq
State Reference	WV
Altitude	msl bound lower : 28000 msl bound upper : 29000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute airway : j85
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 7400 flight time type : 150
ASRS Report	82195
Person 2
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	aircraft equipment problem : less severe 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 other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other

Narrative:

After rotation from cak and prior to gear up (first officer flying) in IMC conditions, both airspeed indicators ceased to operate. They both indicated 0 airspeed. I continued the IMC climb out by reference to attitude and power setting. The erroneous airspeed indications activated both the overspd and stall warnings. Very distracting at a critical time! Upon reaching VFR on top conditions, the captain decided to fly the remainder of the leg. He instructed me to disarm both of the above warning systems by pulling their circuit breaker's. I had to leave my seat to do so. Shortly after leveling at our assigned altitude of FL290, the captain instructed me to contact company radio, initiate a phone patch with another ground facility, obtain WX for airports as possible alternates (VFR conditions), consult the aircraft systems manual and run the appropriate emergency checklists. While involved with the above, the #2 gen went off line. At this point the autoplt was deactivated and the captain was hand flying the aircraft. I looked up from the above assigned duties to scan the instruments. We were slowly deviating from altitude. I called 'altitude' to the captain, which he acknowledged. However, the captain misinterpreted the altitude readout and descend rather than climbed to correct. ATC inquired what altitude we indicated and the captain replied, then corrected from FL280 to FL290.

Original NASA ASRS Text

Title: PLT ALLOWED ACFT TO DESCEND BELOW ASSIGNED ALT.

Narrative: AFTER ROTATION FROM CAK AND PRIOR TO GEAR UP (F/O FLYING) IN IMC CONDITIONS, BOTH AIRSPD INDICATORS CEASED TO OPERATE. THEY BOTH INDICATED 0 AIRSPD. I CONTINUED THE IMC CLBOUT BY REF TO ATTITUDE AND PWR SETTING. THE ERRONEOUS AIRSPD INDICATIONS ACTIVATED BOTH THE OVERSPD AND STALL WARNINGS. VERY DISTRACTING AT A CRITICAL TIME! UPON REACHING VFR ON TOP CONDITIONS, THE CAPT DECIDED TO FLY THE REMAINDER OF THE LEG. HE INSTRUCTED ME TO DISARM BOTH OF THE ABOVE WARNING SYSTEMS BY PULLING THEIR CB'S. I HAD TO LEAVE MY SEAT TO DO SO. SHORTLY AFTER LEVELING AT OUR ASSIGNED ALT OF FL290, THE CAPT INSTRUCTED ME TO CONTACT COMPANY RADIO, INITIATE A PHONE PATCH WITH ANOTHER GND FAC, OBTAIN WX FOR ARPTS AS POSSIBLE ALTERNATES (VFR CONDITIONS), CONSULT THE ACFT SYSTEMS MANUAL AND RUN THE APPROPRIATE EMER CHKLISTS. WHILE INVOLVED WITH THE ABOVE, THE #2 GEN WENT OFF LINE. AT THIS POINT THE AUTOPLT WAS DEACTIVATED AND THE CAPT WAS HAND FLYING THE ACFT. I LOOKED UP FROM THE ABOVE ASSIGNED DUTIES TO SCAN THE INSTRUMENTS. WE WERE SLOWLY DEVIATING FROM ALT. I CALLED 'ALT' TO THE CAPT, WHICH HE ACKNOWLEDGED. HOWEVER, THE CAPT MISINTERPRETED THE ALT READOUT AND DSND RATHER THAN CLBED TO CORRECT. ATC INQUIRED WHAT ALT WE INDICATED AND THE CAPT REPLIED, THEN CORRECTED FROM FL280 TO FL290.

Data retrieved from NASA's ASRS site as of August 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.