B-737 flight crew has altitude deviation on STAR descent.

Attributes
ACN	295615
Time
Date	199501
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : iah
State Reference	TX
Altitude	msl bound lower : 8500 msl bound upper : 10000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu
Operator	common carrier : air carrier
Make Model Name	B737-300
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent other
Route In Use	arrival other arrival star : star enroute airway : iah
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : instrument
Experience	flight time last 90 days : 130 flight time total : 13000 flight time type : 130
ASRS Report	295615
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 250 flight time total : 8500 flight time type : 700
ASRS Report	295265
Events
Anomaly	aircraft equipment problem : less severe altitude deviation : overshoot altitude deviation : crossing restriction not met non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : became reoriented flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

I have just been checked out on the B737-300-500 series aircraft and have just over 130 hours in type. During my flight from dfw-iah, I was given a coast 2 STAR. Since it was my leg, I programmed the FMC with my first officer rechking everything since he has over 7 yrs experience in this aircraft. We both agreed the FMC was programmed properly. The aircraft started its descent for the STAR and was within parameters for crossing hoagi intersection at 10000 ft at 250 KTS. Then at 1000 ft above its crossing altitude, I noticed the aircraft went from a 2800 FPM to a 4500 FPM descent. I then judged that the aircraft was going to bust its assigned altitude of 10000 ft and we were still 10 mi from hoagi intersection. I tried at this point to activate the MCP, but both the first officer's and my MCP went to master arm mode when only mine should have. Because of this situation the autoplt would not respond properly. I then disconnected the autoplt and hand flew the aircraft. In this short period of time we had busted our altitude by 1500 ft. I immediately climbed back to 10000 ft and at the same time iah approach control was instructing us to climb to 10000 ft. After reaching 10000 ft I reconnected the autoplt and reprogrammed the FMC. The FMC started to function properly so I reengaged it. Also the MCP panel went to the master arm only to my side which is the proper function it should have had. Result of the above: I do not trust the automatic function on the B-737 for I have learned this has happened to other crews. I've been told it's not supposed to happen but it does and no one knows why. Supplemental information from acn 295265: contributing factor: I had been on other radio getting ATIS and calling company just prior to this event. Therefore, as I encountered this situation, I had been out of 'the loop' for several mins and uncertain of our clearance or any changes thereto.

Original NASA ASRS Text

Title: B-737 FLC HAS ALTDEV ON STAR DSCNT.

Narrative: I HAVE JUST BEEN CHKED OUT ON THE B737-300-500 SERIES ACFT AND HAVE JUST OVER 130 HRS IN TYPE. DURING MY FLT FROM DFW-IAH, I WAS GIVEN A COAST 2 STAR. SINCE IT WAS MY LEG, I PROGRAMMED THE FMC WITH MY FO RECHKING EVERYTHING SINCE HE HAS OVER 7 YRS EXPERIENCE IN THIS ACFT. WE BOTH AGREED THE FMC WAS PROGRAMMED PROPERLY. THE ACFT STARTED ITS DSCNT FOR THE STAR AND WAS WITHIN PARAMETERS FOR XING HOAGI INTXN AT 10000 FT AT 250 KTS. THEN AT 1000 FT ABOVE ITS XING ALT, I NOTICED THE ACFT WENT FROM A 2800 FPM TO A 4500 FPM DSCNT. I THEN JUDGED THAT THE ACFT WAS GOING TO BUST ITS ASSIGNED ALT OF 10000 FT AND WE WERE STILL 10 MI FROM HOAGI INTXN. I TRIED AT THIS POINT TO ACTIVATE THE MCP, BUT BOTH THE FO'S AND MY MCP WENT TO MASTER ARM MODE WHEN ONLY MINE SHOULD HAVE. BECAUSE OF THIS SIT THE AUTOPLT WOULD NOT RESPOND PROPERLY. I THEN DISCONNECTED THE AUTOPLT AND HAND FLEW THE ACFT. IN THIS SHORT PERIOD OF TIME WE HAD BUSTED OUR ALT BY 1500 FT. I IMMEDIATELY CLBED BACK TO 10000 FT AND AT THE SAME TIME IAH APCH CTL WAS INSTRUCTING US TO CLB TO 10000 FT. AFTER REACHING 10000 FT I RECONNECTED THE AUTOPLT AND REPROGRAMMED THE FMC. THE FMC STARTED TO FUNCTION PROPERLY SO I REENGAGED IT. ALSO THE MCP PANEL WENT TO THE MASTER ARM ONLY TO MY SIDE WHICH IS THE PROPER FUNCTION IT SHOULD HAVE HAD. RESULT OF THE ABOVE: I DO NOT TRUST THE AUTO FUNCTION ON THE B-737 FOR I HAVE LEARNED THIS HAS HAPPENED TO OTHER CREWS. I'VE BEEN TOLD IT'S NOT SUPPOSED TO HAPPEN BUT IT DOES AND NO ONE KNOWS WHY. SUPPLEMENTAL INFO FROM ACN 295265: CONTRIBUTING FACTOR: I HAD BEEN ON OTHER RADIO GETTING ATIS AND CALLING COMPANY JUST PRIOR TO THIS EVENT. THEREFORE, AS I ENCOUNTERED THIS SIT, I HAD BEEN OUT OF 'THE LOOP' FOR SEVERAL MINS AND UNCERTAIN OF OUR CLRNC OR ANY CHANGES THERETO.

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.