FA22 crew had a loss of cabin pressurization. They also had an altitude overshoot on descent.

Attributes
ACN	437119
Time
Date	199905
Day	Sun
Local Time Of Day	1801 To 2400
Place
Locale Reference	airport : bil.airport
State Reference	MT
Altitude	msl single value : 20700
Environment
Flight Conditions	IMC
Light	Dusk
Aircraft 1
Controlling Facilities	artcc : zlc.artcc tower : yip.tower
Operator	common carrier : air carrier
Make Model Name	SA-227 AC Metro III
Operating Under FAR Part	Part 121
Flight Phase	climbout : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp pilot : multi engine
Experience	flight time last 90 days : 150 flight time total : 2100 flight time type : 625
ASRS Report	437119
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : multi engine pilot : instrument pilot : commercial
Events
Anomaly	aircraft equipment problem : critical altitude deviation : overshoot non adherence : clearance
Independent Detector	other flight crewa other flight crewb other other : 3
Resolutory Action	flight crew : declared emergency flight crew : diverted to another airport flight crew : returned to original clearance flight crew : landed in emergency condition
Consequence	other
Supplementary
Problem Areas	Aircraft Flight Crew Human Performance
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation

Narrative:

I was the captain and the PNF in an SA227 for air carrier out of billings, mt. We were en route to wolf point, mt, cleared to FL210, still climbing at about 60 mi northeast of the billings VOR when the cabin altitude annunciator light came on climbing through FL207. I then requested 10000 ft direct billings for the ILS with ZLC. The first officer initiated a rapid descent. I covered the action items for cabin altitude light via the checklist. During the descent, I was busy with ATC, checklist, and passenger, when I noticed the first officer descended down to 9300 ft. I advised the first officer of his altitude and he corrected immediately, climbing back to 10000 ft, but ATC did query us on our altitude. By that time we were going through 9500 ft for 10000 ft. About 40 mi northeast of billings, ATC handed us off to billings approach. We initiated the ILS to runway 28R and landed without further incident.

Original NASA ASRS Text

Title: FA22 CREW HAD A LOSS OF CABIN PRESSURIZATION. THEY ALSO HAD AN ALT OVERSHOOT ON DSCNT.

Narrative: I WAS THE CAPT AND THE PNF IN AN SA227 FOR ACR OUT OF BILLINGS, MT. WE WERE ENRTE TO WOLF POINT, MT, CLRED TO FL210, STILL CLBING AT ABOUT 60 MI NE OF THE BILLINGS VOR WHEN THE CABIN ALT ANNUNCIATOR LIGHT CAME ON CLBING THROUGH FL207. I THEN REQUESTED 10000 FT DIRECT BILLINGS FOR THE ILS WITH ZLC. THE FO INITIATED A RAPID DSCNT. I COVERED THE ACTION ITEMS FOR CABIN ALT LIGHT VIA THE CHKLIST. DURING THE DSCNT, I WAS BUSY WITH ATC, CHKLIST, AND PAX, WHEN I NOTICED THE FO DSNDED DOWN TO 9300 FT. I ADVISED THE FO OF HIS ALT AND HE CORRECTED IMMEDIATELY, CLBING BACK TO 10000 FT, BUT ATC DID QUERY US ON OUR ALT. BY THAT TIME WE WERE GOING THROUGH 9500 FT FOR 10000 FT. ABOUT 40 MI NE OF BILLINGS, ATC HANDED US OFF TO BILLINGS APCH. WE INITIATED THE ILS TO RWY 28R AND LANDED WITHOUT FURTHER INCIDENT.

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.