<< >> NASA ASRS Report 394040, February 1998

Pilot of an atx cargo twin descended below assigned altitude during descent to destination airport and recognized his mistake and returned immediately to assigned. However, his mistake caused less than standard separation with another aircraft and ATC intervention to confirm his altitude.

Attributes
ACN	394040
Time
Date	199802
Day	Wed
Local Time Of Day	0601 To 1200
Place
Locale Reference	airport : mdt
State Reference	PA
Altitude	msl bound lower : 3400 msl bound upper : 4000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : mdt
Operator	common carrier : air taxi
Make Model Name	Commercial Fixed Wing
Operating Under FAR Part	Part 135
Flight Phase	cruise other
Flight Plan	IFR
Aircraft 2
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	other : unknown
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	other other : other pilot : instrument pilot : commercial pilot : cfi pilot : atp
Experience	flight time last 90 days : 130 flight time total : 3400 flight time type : 750
ASRS Report	394040
Person 2
Function	flight crew : single pilot
Events
Anomaly	altitude deviation : overshoot conflict : airborne less severe non adherence : clearance
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Miss Distance	horizontal : 2000 vertical : 1200
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

Cruising at 5000 ft en route from bwi to mdt, I was instructed to descend to 3000 ft. This was amended a few mins later for me to stop my descent at 4000 ft. Both of these instructions were read back and understood. I descended through 4000 ft to 3400 ft, at which point I realized my error and initiated an immediate sharp correction back to 4000 ft. While I was correcting (3700 ft) approach initiated corrective action for another aircraft in my vicinity. By the time ATC asked my altitude, I was back at 4000 ft and I then saw the other aircraft cross at my 12 O'clock low position. Human factors: fatigue -- this was the third leg of an overnight flight with hard WX and approachs. Distrs -- single pilot crew, no autoplt, preparing for approach, no altitude alert. Change of instructions from 3000 ft to 4000 ft as descent altitude.

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Original NASA ASRS Text

Title: PLT OF AN ATX CARGO TWIN DSNDED BELOW ASSIGNED ALT DURING DSCNT TO DEST ARPT AND RECOGNIZED HIS MISTAKE AND RETURNED IMMEDIATELY TO ASSIGNED. HOWEVER, HIS MISTAKE CAUSED LTSS WITH ANOTHER ACFT AND ATC INTERVENTION TO CONFIRM HIS ALT.

Narrative: CRUISING AT 5000 FT ENRTE FROM BWI TO MDT, I WAS INSTRUCTED TO DSND TO 3000 FT. THIS WAS AMENDED A FEW MINS LATER FOR ME TO STOP MY DSCNT AT 4000 FT. BOTH OF THESE INSTRUCTIONS WERE READ BACK AND UNDERSTOOD. I DSNDED THROUGH 4000 FT TO 3400 FT, AT WHICH POINT I REALIZED MY ERROR AND INITIATED AN IMMEDIATE SHARP CORRECTION BACK TO 4000 FT. WHILE I WAS CORRECTING (3700 FT) APCH INITIATED CORRECTIVE ACTION FOR ANOTHER ACFT IN MY VICINITY. BY THE TIME ATC ASKED MY ALT, I WAS BACK AT 4000 FT AND I THEN SAW THE OTHER ACFT CROSS AT MY 12 O'CLOCK LOW POS. HUMAN FACTORS: FATIGUE -- THIS WAS THE THIRD LEG OF AN OVERNIGHT FLT WITH HARD WX AND APCHS. DISTRS -- SINGLE PLT CREW, NO AUTOPLT, PREPARING FOR APCH, NO ALT ALERT. CHANGE OF INSTRUCTIONS FROM 3000 FT TO 4000 FT AS DSCNT ALT.

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.