Altitude excursion east of pmm, mi.

Attributes
ACN	488158
Time
Date	200010
Day	Tue
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : pmm.vortac
State Reference	MI
Altitude	msl bound lower : 21750 msl bound upper : 22000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zau.artcc
Operator	common carrier : air carrier
Make Model Name	B727 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other vortac
Flight Phase	descent : intermediate altitude
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 14700 flight time type : 2400
ASRS Report	488158
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : atp
Experience	flight time last 90 days : 150 flight time total : 3200 flight time type : 1000
ASRS Report	488160
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to assigned altitude
Supplementary
Problem Areas	Flight Crew Human Performance Aircraft
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Awareness of altitude 'engage' for altitude 'hold' on B727. Leveled off at FL220, (22000 ft). Was during initial descent portion of flight, going into ord. After leveling off at FL220, I engaged autoplt, with altitude hold. Normally I check to verify altitude hold is, in fact holding. Subsequent to engaging, I looked down immediately to check approach charts, airport diagrams, etc. Approximately 15-30 seconds after leveloff, I looked up again and saw altitude of 21750 ft, and descending. I immediately clicked off the autoplt, added power, and climbed immediately to assigned altitude, FL220. No conflicts, no ATC query. Just, to state, if you 'set a switch,' verify appropriate engagement or action in place. I looked down too quickly. To verify is the utmost, especially altitude hold. Descent was subtle, and no one noticed it in the cockpit. Supplemental information from acn 488160: we have no sops regarding autoplt engagement procedures unlike the glass cockpits, so the PNF might not be in the autoplt engagement mode loop. With only a switch position being the indication for altitude hold, which is on the center console, it is a very easy one to miss. I am surprised there are not any 'autoplt engaged' and 'altitude hold' annunciator lights on the instrument panel. New sops and or these lights would probably help eliminate this type of problem.

Original NASA ASRS Text

Title: ALT EXCURSION E OF PMM, MI.

Narrative: AWARENESS OF ALT 'ENGAGE' FOR ALT 'HOLD' ON B727. LEVELED OFF AT FL220, (22000 FT). WAS DURING INITIAL DSCNT PORTION OF FLT, GOING INTO ORD. AFTER LEVELING OFF AT FL220, I ENGAGED AUTOPLT, WITH ALT HOLD. NORMALLY I CHK TO VERIFY ALT HOLD IS, IN FACT HOLDING. SUBSEQUENT TO ENGAGING, I LOOKED DOWN IMMEDIATELY TO CHK APCH CHARTS, ARPT DIAGRAMS, ETC. APPROX 15-30 SECONDS AFTER LEVELOFF, I LOOKED UP AGAIN AND SAW ALT OF 21750 FT, AND DSNDING. I IMMEDIATELY CLICKED OFF THE AUTOPLT, ADDED PWR, AND CLBED IMMEDIATELY TO ASSIGNED ALT, FL220. NO CONFLICTS, NO ATC QUERY. JUST, TO STATE, IF YOU 'SET A SWITCH,' VERIFY APPROPRIATE ENGAGEMENT OR ACTION IN PLACE. I LOOKED DOWN TOO QUICKLY. TO VERIFY IS THE UTMOST, ESPECIALLY ALT HOLD. DSCNT WAS SUBTLE, AND NO ONE NOTICED IT IN THE COCKPIT. SUPPLEMENTAL INFO FROM ACN 488160: WE HAVE NO SOPS REGARDING AUTOPLT ENGAGEMENT PROCS UNLIKE THE GLASS COCKPITS, SO THE PNF MIGHT NOT BE IN THE AUTOPLT ENGAGEMENT MODE LOOP. WITH ONLY A SWITCH POS BEING THE INDICATION FOR ALT HOLD, WHICH IS ON THE CTR CONSOLE, IT IS A VERY EASY ONE TO MISS. I AM SURPRISED THERE ARE NOT ANY 'AUTOPLT ENGAGED' AND 'ALT HOLD' ANNUNCIATOR LIGHTS ON THE INST PANEL. NEW SOPS AND OR THESE LIGHTS WOULD PROBABLY HELP ELIMINATE THIS TYPE OF PROB.

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.