Gulfstream G100 crew improperly descended from 4000 ft toward 2000 ft for approach to teb.

Attributes
ACN	599093
Time
Date	200311
Day	Thu
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : stw.vor
State Reference	NJ
Altitude	msl bound lower : 2000 msl bound upper : 4000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : n90.tracon
Operator	general aviation : corporate
Make Model Name	Gulfstream 100 [G100] (IAI 1125 Astra)
Operating Under FAR Part	Part 91
Navigation In Use	ils localizer & glide slope : 6
Flight Phase	descent : approach
Route In Use	approach : instrument precision arrival : on vectors
Flight Plan	IFR
Aircraft 2
Controlling Facilities	tracon : n90.tracon
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Flight Phase	descent : approach
Flight Plan	IFR
Person 1
Affiliation	company : corporate
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 50 flight time total : 2600 flight time type : 500
ASRS Report	599093
Person 2
Affiliation	company : corporate
Function	flight crew : first officer
Events
Anomaly	altitude deviation : excursion from assigned altitude non adherence : published procedure non adherence : far other anomaly other
Independent Detector	other flight crewa other flight crewb
Resolutory Action	controller : issued new clearance flight crew : returned to assigned altitude none taken : detected after the fact other
Supplementary
Problem Areas	Flight Crew Human Performance ATC Human Performance
Primary Problem	ATC Human Performance
Air Traffic Incident	other

Narrative:

While en route from abe (lehigh valley international) to teb (teterboro, nj). Just after passing the stw (stillwater) VOR on vectors at assigned altitude of 4000 ft for the ILS runway 6 at teterboro, the PNF received instructions from the approach controller to fly heading 130 degrees. Shortly after we received instructions from the controller to descend and maintain 2000 ft, PNF acknowledged, leaving 4000 ft for 2000 ft with our call sign and we began descending to 2000 ft. After hearing another aircraft on the same frequency with a very similar call sign the PNF asked the controller to confirm our assigned altitude. His response was 4000 ft. We advised the controller we were assigned 2000 ft. At this time we were instructed to climb and maintain 3000 ft. We received standard vectors to the ILS runway 6, landed runway 6 at teb without further incident. This event took place in VMC and no other aircraft were involved. The controller was very busy handling several aircraft, another aircraft on the frequency with the same last 2 registration letters, were all factors leading to miscoms between the controller and the pilots. In the past, and, usually when another aircraft with similar north numbers are on the same frequency the controller will say, 'please be advised another aircraft with a similar north number is on the frequency please listen up.' I believe this is good practice and all controllers and pilots should be reminded to do so. This will greatly help avoid miscoms between pilots and controllers.

Original NASA ASRS Text

Title: GULFSTREAM G100 CREW IMPROPERLY DSNDED FROM 4000 FT TOWARD 2000 FT FOR APCH TO TEB.

Narrative: WHILE ENRTE FROM ABE (LEHIGH VALLEY INTL) TO TEB (TETERBORO, NJ). JUST AFTER PASSING THE STW (STILLWATER) VOR ON VECTORS AT ASSIGNED ALT OF 4000 FT FOR THE ILS RWY 6 AT TETERBORO, THE PNF RECEIVED INSTRUCTIONS FROM THE APCH CTLR TO FLY HEADING 130 DEGS. SHORTLY AFTER WE RECEIVED INSTRUCTIONS FROM THE CTLR TO DSND AND MAINTAIN 2000 FT, PNF ACKNOWLEDGED, LEAVING 4000 FT FOR 2000 FT WITH OUR CALL SIGN AND WE BEGAN DSNDING TO 2000 FT. AFTER HEARING ANOTHER ACFT ON THE SAME FREQ WITH A VERY SIMILAR CALL SIGN THE PNF ASKED THE CTLR TO CONFIRM OUR ASSIGNED ALT. HIS RESPONSE WAS 4000 FT. WE ADVISED THE CTLR WE WERE ASSIGNED 2000 FT. AT THIS TIME WE WERE INSTRUCTED TO CLB AND MAINTAIN 3000 FT. WE RECEIVED STANDARD VECTORS TO THE ILS RWY 6, LANDED RWY 6 AT TEB WITHOUT FURTHER INCIDENT. THIS EVENT TOOK PLACE IN VMC AND NO OTHER ACFT WERE INVOLVED. THE CTLR WAS VERY BUSY HANDLING SEVERAL ACFT, ANOTHER ACFT ON THE FREQ WITH THE SAME LAST 2 REGISTRATION LETTERS, WERE ALL FACTORS LEADING TO MISCOMS BTWN THE CTLR AND THE PLTS. IN THE PAST, AND, USUALLY WHEN ANOTHER ACFT WITH SIMILAR N NUMBERS ARE ON THE SAME FREQ THE CTLR WILL SAY, 'PLEASE BE ADVISED ANOTHER ACFT WITH A SIMILAR N NUMBER IS ON THE FREQ PLEASE LISTEN UP.' I BELIEVE THIS IS GOOD PRACTICE AND ALL CTLRS AND PLTS SHOULD BE REMINDED TO DO SO. THIS WILL GREATLY HELP AVOID MISCOMS BTWN PLTS AND CTLRS.

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.