ACFT CLEARED FOR THE RIVER VISUAL APCH AT LGA ARE HELD AT 3000' UNTIL NORTH OF CENTRAL PARK; TOO HIGH FOR A STABILIZED APCH.

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SEE ATTACHED FOR DESCRIPTION; AS YOU MAY SEE BTWN THE LINES; WE WERE PWR OFF FOR MOST OF THE LAST 1000'. THE CHARTED APCH CALLS FOR MAINTAINING 2000' FOR AS LONG AS POSSIBLE. THE PATH DEPICTED SHOWS FOLLOWING THE RIVER TO N OF CENTRAL PARK AND THEN TURNING FINAL. NOTE THAT THE ABOVE ALT RESTRICTION IS RECOMMENDED AND THE POINT TO TURN FINAL IS ALSO RECOMMENDED. THIS GIVES THE PLT THE LATITUDE HE NEEDS TO DEAL WITH WITH CONDITIONS AT HAND. CONDITIONS THAT WOULD DICTATE OTHER THAN FOLLOWING THE RECOMMENDED PROFILE INCLUDE UNUSUAL ACFT CONDITIONS; OVERRIDING SOUTHERLY WINDS; OVERRIDING NORTHWESTERLY WINDS; AND THE NEED TO COMPLY WITH OTHER ATC RESTRICTIONS SUCH AS MAINTAINING A GIVEN AIRSPD. THIS IS NOT A BAD APCH. HOWEVER; I HAVE BEEN GIVEN THIS APCH WITH THE FOLLOWING CLRNC FROM APCH CTL. MAINTAIN 3000' UNTIL N OF CENTRAL PARK. THIS EFFECTIVELY REMOVES MY DISCRETION AND LOCKS ME INTO THE FOLLOWING: FROM A POINT 6.3 NM FROM THE RWY I HAVE TO LOSE 2940'. THIS IS IMPOSSIBLE TO DO FOLLOWING ACR PROCS THAT CALL FOR ACHIEVING LNDG CONFIGN AFTER TURNING FINAL AND 3000' IS MAINTAINED UNTIL N OF CENTRAL PARK YOU THEN HAVE TO BEGIN AN IMMEDIATE DSCNT AT MINIMUM APCH SPD (15 DEG BANK MAX). THIS WOULD AVERAGE 1100 FPM TO T/D AT AN APCH SPD OF 135 KTS. OF COURSE IF THERE ARE ANY OVERRIDING WINDS OR IF THE APCH SPD IS HIGHER THE RATE OF DSCNT WILL BE HIGHER. THIS VERT PATH TO RWY 13 BEGINS ABOUT 1500' ABOVE THE GS FOR THAT RWY. TO SAY THAT THIS SITUATION MAY RESULT IN AN UNSTABILIZED APCH IS A GROSS UNDERSTATEMENT OF FACT. IT IS POSSIBLE TO BE STABILIZED FOR THE LAST 1000' FROM THIS APCH; BUT IT REQUIRES EVERYTHING TO BE PERFECT. THAT INCLUDES PLT TECHNIQUE; AN ABSENCE OF AIRSPD CTLS FROM ATC; WINDS THAT DO NOT INTERFERE WITH THE PROFILE AND MOST CERTAINLY ADVANCED KNOWLEDGE THAT THE SITUATION IS SO DEMANDING. TO ARRIVE AT THE GS AT 1000' MSL; IT TAKES ABOUT 1400 FPM FROM CENTRAL PARK TO THE GS. AN ACR IN THE LNDG CONFIGN WITH PWR OFF DESCENDS AT A MAX OF APPROX 1800 FPM. THEREFORE; THERE IS NO CATCHING UP TO CORRECT ANY PROBS THAT BECOME EVIDENT. THE ONLY SOLUTION IS TO GO AROUND OR CONTINUE AN UNSTABILIZED APCH. SINCE THESE APCHS ARE ONLY USED IN GOOD WX MANY PLTS MAY ELECT TO CONTINUE THE APCH AND HOPE ALL ENDS WELL. ONE OF THE BASIC TENANTS OF SAFE FLYING IS THAT A STABILIZED APCH GIVES THE PLT THE NECESSARY EDGE TO DEAL WITH THE UNEXPECTED. FLYING THIS APCH TAKES THE SAFETY MARGINS TO UNACCEPTABLE LEVELS. THIS APCH MAY BE OK FOR OLDER ACFT DUE TO THEIR ABILITY TO MAKE HIGH RATES OF DSCNT DOWN TO THE GS; BUT FOR THE EFFICIENT WINGS ON THE NEWER ACFT IT IS UNACCEPTABLE. I HOPE YOUR OFFICE CAN GET THE LGA ATC TO STOP ISSUING THIS APCH WITH THE ABOVE DESCRIBED RESTRICTIONS. I AM CERTAINLY AWARE THAT I CAN REFUSE THE APCH AND WILL IN THE FUTURE; BUT WE SHOULD DO WHAT WE CAN TO HELP THE UNINITIATED. THE ATTACHED PROFILE SHOWS HOW IT CAN BE DONE UNDER IDEAL CONDITIONS (INCLUDING CALM WINDS). A) ARRIVE IN LNDG CONFIGN AND ON REF SPD. BEGIN IMMEDIATE DSCNT OF 1400 FPM. B) FROM A TO B IS 8 SECS. AT B BEGIN THE 15 DEG BANK. C) FROM B TO C IS 30 SECS. ROLL OUT ON LOC. D) ARRIVE ON GS. C TO D IS 45 SECS. IF YOU GOT THIS FAR OK THE REST IS A PIECE OF CAKE. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING: THE RPTR'S COMPLAINT WAS PRESENTED TO A MEETING WITH THE PORT OF AUTHORITY AND SOME FAA REPS. THEY SAID THEIR REASON FOR THE 3000' RESTRICTION WAS TO PROVIDE SEP FROM VFR TFC. RPTR REITERATED THAT IT WOULD BE FOOLISH TO EXPECT ALL APCHS LIKE THIS TO RESULT IN STABILIZED APCHS AND THE RESULT COULD BE DANGEROUS.