Flight crew of a fokker 100, FK10, descended below assigned altitude during an ILS approach resulting in approach controller issuing a low altitude alert. Flight crew had descended outside the OM to 1200 ft below assigned altitude and 400 ft below the OM. Flight crew claimed that the last ATC instructions were too long and complex causing them to mistake the altitude to which assigned.

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Attributes
ACN	402850
Time
Date	199805
Day	Fri
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : cle
State Reference	OH
Altitude	msl bound lower : 2000 msl bound upper : 2400
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : cle
Operator	common carrier : air carrier
Make Model Name	Fokker 100
Operating Under FAR Part	Part 121
Navigation In Use	Other Other
Flight Phase	descent : approach
Route In Use	arrival other enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : flight engineer pilot : atp
Experience	flight time last 90 days : 164 flight time total : 11000 flight time type : 1100
ASRS Report	402850
Person 2
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Events
Anomaly	altitude deviation : overshoot non adherence : clearance other anomaly other
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	other other
Consequence	faa : reviewed incident with flight crew
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

We had been cleared for approach to runway 23L in cle and both of us had heard the controller give an altitude of 2000 ft, which we read back. Then we both verified the new altitude visually and aurally as per company procedure. However, this clearance included about 3 other separate commands. It was a mouthful to read back. Just prior to foord, controller said low altitude alert, what is your altitude? We said, 2000 ft. The controller said he had cleared us to 3200 ft, I think. He was excited and hard to understand. We visually had the runway and a nice view of the city of cleveland below us. Safety of the flight was not compromised. We landed without incident and talked with controller supervisor. Many times controllers give so many commands in one sentence, it is easy for errors to occur -- both from the controller's side and the pilot's side. This was not even a busy controller or a busy situation.

Original NASA ASRS Text

Title: FLC OF A FOKKER 100, FK10, DSNDED BELOW ASSIGNED ALT DURING AN ILS APCH RESULTING IN APCH CTLR ISSUING A LOW ALT ALERT. FLC HAD DSNDED OUTSIDE THE OM TO 1200 FT BELOW ASSIGNED ALT AND 400 FT BELOW THE OM. FLC CLAIMED THAT THE LAST ATC INSTRUCTIONS WERE TOO LONG AND COMPLEX CAUSING THEM TO MISTAKE THE ALT TO WHICH ASSIGNED.

Narrative: WE HAD BEEN CLRED FOR APCH TO RWY 23L IN CLE AND BOTH OF US HAD HEARD THE CTLR GIVE AN ALT OF 2000 FT, WHICH WE READ BACK. THEN WE BOTH VERIFIED THE NEW ALT VISUALLY AND AURALLY AS PER COMPANY PROC. HOWEVER, THIS CLRNC INCLUDED ABOUT 3 OTHER SEPARATE COMMANDS. IT WAS A MOUTHFUL TO READ BACK. JUST PRIOR TO FOORD, CTLR SAID LOW ALT ALERT, WHAT IS YOUR ALT? WE SAID, 2000 FT. THE CTLR SAID HE HAD CLRED US TO 3200 FT, I THINK. HE WAS EXCITED AND HARD TO UNDERSTAND. WE VISUALLY HAD THE RWY AND A NICE VIEW OF THE CITY OF CLEVELAND BELOW US. SAFETY OF THE FLT WAS NOT COMPROMISED. WE LANDED WITHOUT INCIDENT AND TALKED WITH CTLR SUPVR. MANY TIMES CTLRS GIVE SO MANY COMMANDS IN ONE SENTENCE, IT IS EASY FOR ERRORS TO OCCUR -- BOTH FROM THE CTLR'S SIDE AND THE PLT'S SIDE. THIS WAS NOT EVEN A BUSY CTLR OR A BUSY SIT.

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.