Pilot of small transport making rapid descent overshot assigned altitude.

Attributes
ACN	110049
Time
Date	198904
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : k76
State Reference	KS
Altitude	msl bound lower : 6500 msl bound upper : 15000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zkc
Operator	common carrier : air taxi
Make Model Name	Small Transport
Flight Phase	cruise other descent other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : single pilot
Qualification	pilot : commercial
Experience	flight time last 90 days : 90 flight time total : 12400
ASRS Report	110049
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other controllera other flight crewa
Resolutory Action	aircraft : equipment problem dissipated flight crew : returned to intended course or assigned course other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation other

Narrative:

Approximately 50 NM southwest of weiss airport, ZKC (ozark sector) told me to leave 15000 ft for 7000, 'immediately and expedite,' which is used by ATC to indicate an imminent hazardous situation. I started an immediate flight idle descent (emergency descent procedures). Due to the line of thunderstorms a few mi to my south parallel to my flight course, the turbulent air prevented me from maintaining a high airspeed for maximum descent. I put the gear down and was able to maintain approximately 4500 FPM descent. I started my level off 200 ft before reaching 7000 ft on my left altimeter and raised the landing gear. ATC asked my altitude. I indicated 6500 ft on the left altimeter. ATC said they indicated 6000 ft. I looked at my right altimeter. It indicated 6900 ft. I maintained level attitude at 6900 ft and my left altimeter raised backup to 6900 ft. Then I climbed to 7000 ft MSL. ATC did not take into account altimeter error plus that type of descent may not given an accurate indication on mode C for that aircraft type.

Original NASA ASRS Text

Title: PLT OF SMT MAKING RAPID DESCENT OVERSHOT ASSIGNED ALT.

Narrative: APPROX 50 NM SW OF WEISS ARPT, ZKC (OZARK SECTOR) TOLD ME TO LEAVE 15000 FT FOR 7000, 'IMMEDIATELY AND EXPEDITE,' WHICH IS USED BY ATC TO INDICATE AN IMMINENT HAZARDOUS SIT. I STARTED AN IMMEDIATE FLT IDLE DSCNT (EMER DSCNT PROCS). DUE TO THE LINE OF TSTMS A FEW MI TO MY S PARALLEL TO MY FLT COURSE, THE TURBULENT AIR PREVENTED ME FROM MAINTAINING A HIGH AIRSPD FOR MAX DSCNT. I PUT THE GEAR DOWN AND WAS ABLE TO MAINTAIN APPROX 4500 FPM DSCNT. I STARTED MY LEVEL OFF 200 FT BEFORE REACHING 7000 FT ON MY L ALTIMETER AND RAISED THE LNDG GEAR. ATC ASKED MY ALT. I INDICATED 6500 FT ON THE LEFT ALTIMETER. ATC SAID THEY INDICATED 6000 FT. I LOOKED AT MY R ALTIMETER. IT INDICATED 6900 FT. I MAINTAINED LEVEL ATTITUDE AT 6900 FT AND MY LEFT ALTIMETER RAISED BACKUP TO 6900 FT. THEN I CLBED TO 7000 FT MSL. ATC DID NOT TAKE INTO ACCOUNT ALTIMETER ERROR PLUS THAT TYPE OF DSCNT MAY NOT GIVEN AN ACCURATE INDICATION ON MODE C FOR THAT ACFT TYPE.

Data retrieved from NASA's ASRS site as of August 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.