Operational deviation dscnded below assigned altitude.

Attributes
ACN	293130
Time
Date	199501
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : hvq
State Reference	WV
Altitude	msl bound lower : 15000 msl bound upper : 15000
Environment
Flight Conditions	VMC
Light	Dawn
Aircraft 1
Controlling Facilities	artcc : zid
Operator	general aviation : corporate
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 90 flight time total : 8600 flight time type : 3400
ASRS Report	293130
Person 2
Affiliation	Other
Function	flight crew : first officer
Qualification	pilot : atp
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : clearance
Independent Detector	other other : unspecified atc other other : unspecified cockpit
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We had been flying since XA00 am on return leg to south carolina from michigan, assigned 15000 ft. Center asked to say altitude. We noticed we were about 1000 ft low, immediately (20 seconds) climbed back to proper altitude. Nothing more was said by ATC concerning deviation. There were no traffic conflict. Both pilots had been up (awake) for about 24 hours (combined flight time at about 16000 hours). What happened is, we think: got an altimeter change disconnected altitude-hold to correct altitude. Forgot to reengage altitude hold, this started what we feel was a very slow (100 FPM) rate of descent. We can't understand why we didn't notice (except for lack of sleep) and why did it take ATC so long to say something. Flying under far 91 there are no duty hours restrs covered since don't apply when your company wants manufactured goods delivered to customers, so why can't the FAA make up duty hours rules that applies to far 91 also, keeping in mind that corporate pilot might have other duties besides flying. Bosses don't like to hear that the pilots are tired, when there is no restr on duty hours.

Original NASA ASRS Text

Title: OPDEV DSCNDED BELOW ASSIGNED ALT.

Narrative: WE HAD BEEN FLYING SINCE XA00 AM ON RETURN LEG TO SOUTH CAROLINA FROM MICHIGAN, ASSIGNED 15000 FT. CTR ASKED TO SAY ALT. WE NOTICED WE WERE ABOUT 1000 FT LOW, IMMEDIATELY (20 SECONDS) CLBED BACK TO PROPER ALT. NOTHING MORE WAS SAID BY ATC CONCERNING DEV. THERE WERE NO TFC CONFLICT. BOTH PLTS HAD BEEN UP (AWAKE) FOR ABOUT 24 HRS (COMBINED FLT TIME AT ABOUT 16000 HRS). WHAT HAPPENED IS, WE THINK: GOT AN ALTIMETER CHANGE DISCONNECTED ALT-HOLD TO CORRECT ALT. FORGOT TO REENGAGE ALT HOLD, THIS STARTED WHAT WE FEEL WAS A VERY SLOW (100 FPM) RATE OF DSCNT. WE CAN'T UNDERSTAND WHY WE DIDN'T NOTICE (EXCEPT FOR LACK OF SLEEP) AND WHY DID IT TAKE ATC SO LONG TO SAY SOMETHING. FLYING UNDER FAR 91 THERE ARE NO DUTY HRS RESTRS COVERED SINCE DON'T APPLY WHEN YOUR COMPANY WANTS MANUFACTURED GOODS DELIVERED TO CUSTOMERS, SO WHY CAN'T THE FAA MAKE UP DUTY HRS RULES THAT APPLIES TO FAR 91 ALSO, KEEPING IN MIND THAT CORPORATE PLT MIGHT HAVE OTHER DUTIES BESIDES FLYING. BOSSES DON'T LIKE TO HEAR THAT THE PLTS ARE TIRED, WHEN THERE IS NO RESTR ON DUTY HRS.

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.