Narrative:

After a touch-and-go landing on runway 24 at allentown, PA, we received radar vectors for a right turn and we were then cleared direct to 'blown' intersection at 3000 ft and cleared for the VOR-a approach at allentown. As we approached 'blown,' the GPWS gave repeated 'terrain, terrain, whoop, whoop, pull up' warnings. Since we were in day VMC flight conditions and could clearly see that we were not in danger of a ground collision, we did not pull up. After repeated warnings, we selected the GPWS override to silence the aural warning. However, the 'pull up' annunciator continued to flash during the entire holding pattern course reversal, VOR approach, circling maneuver, and landing. It stopped upon touchdown. Review of the new york sectional chart shows that there is a ridge line, perpendicular to our flight path, located near 'blown' intersection exactly where we began receiving the warning. The united states geological survey, kunkletown quadrangle map, shows that the ridge line has an elevation change from 900 ft to 1500 ft in approximately 2/5 of a statute mile. At a ground speed of 200 KTS this would have produced a radar altitude closure rate of approximately 5700 FPM. Review of the flight manual supplement for our ground proximity/windshear warning system shows that mode would have activated when the radar altimeter showed a terrain closure rate of approximately 5000 FPM. The warning would have continued until the aircraft gained 300 ft of pressure altitude, which in our case never happened. This same type of incident has occurred while flying the localizer/DME back course runway 8 approach at martinsburg, wv, and while being vectored at roanoke, va. It is rumored that there have been complaints about the localizer runway 27 approach at san diego, ca, and complaints from airlines concerning the ashville, nc, area. I wonder how many other locations there are where this will occur? Had we been operating in IFR conditions, the flight manual supplement would have required us to, 'execute a positive pull up, apply engine power and ascend at the best climb angle until the warning ceases.' had we done that, we would have created a collision hazard for any air traffic that may have been above us. There is a note in the flight manual supplement that states, 'when operations, at specific locations, must be conducted in close proximity to terrain, the GPWS/ground spoiler flap override switch may be set to 'on' to desensitize the terrain closure rate warning mode.' is this to imply that we should operate with the override on whenever we fly an approach or take a radar vector at an area where we have not accomplished a detailed analysis? This system and also the system installed in another type aircraft have generated these warnings. The GPWS appears to be functioning exactly as designed. The IFR approach procedures must meet required terrain clearance requirements. It appears that there is no requirement for the design of the GPWS to correlate with the design of IFR approach procedures and the associated terrain. An informal inquiry to an FAA flight inspection unit revealed that aircraft that they use to check approach procedures are not equipped with GPWS. To be required to execute an abrupt pull up while flying a published procedure does not enhance safety. On the other hand, the record will show that there have been a number of accidents that occurred because flcs elected to ignore the GPWS and consequently collided with the ground. The design criteria for the GPWS and the terminal instruments procedures should be correlated to prevent these false warnings.

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Original NASA ASRS Text

Title: GOV PLT ON TRAINING FLT IN AN MDT JET ACFT EXPERIENCED A GPWS WARNING DURING HOLDING AT AN APCH INTXN IN VFR CONDITIONS.

Narrative: AFTER A TOUCH-AND-GO LNDG ON RWY 24 AT ALLENTOWN, PA, WE RECEIVED RADAR VECTORS FOR A R TURN AND WE WERE THEN CLRED DIRECT TO 'BLOWN' INTXN AT 3000 FT AND CLRED FOR THE VOR-A APCH AT ALLENTOWN. AS WE APCHED 'BLOWN,' THE GPWS GAVE REPEATED 'TERRAIN, TERRAIN, WHOOP, WHOOP, PULL UP' WARNINGS. SINCE WE WERE IN DAY VMC FLT CONDITIONS AND COULD CLRLY SEE THAT WE WERE NOT IN DANGER OF A GND COLLISION, WE DID NOT PULL UP. AFTER REPEATED WARNINGS, WE SELECTED THE GPWS OVERRIDE TO SILENCE THE AURAL WARNING. HOWEVER, THE 'PULL UP' ANNUNCIATOR CONTINUED TO FLASH DURING THE ENTIRE HOLDING PATTERN COURSE REVERSAL, VOR APCH, CIRCLING MANEUVER, AND LNDG. IT STOPPED UPON TOUCHDOWN. REVIEW OF THE NEW YORK SECTIONAL CHART SHOWS THAT THERE IS A RIDGE LINE, PERPENDICULAR TO OUR FLT PATH, LOCATED NEAR 'BLOWN' INTXN EXACTLY WHERE WE BEGAN RECEIVING THE WARNING. THE UNITED STATES GEOLOGICAL SURVEY, KUNKLETOWN QUADRANGLE MAP, SHOWS THAT THE RIDGE LINE HAS AN ELEVATION CHANGE FROM 900 FT TO 1500 FT IN APPROX 2/5 OF A STATUTE MILE. AT A GND SPD OF 200 KTS THIS WOULD HAVE PRODUCED A RADAR ALT CLOSURE RATE OF APPROX 5700 FPM. REVIEW OF THE FLT MANUAL SUPPLEMENT FOR OUR GND PROX/WINDSHEAR WARNING SYS SHOWS THAT MODE WOULD HAVE ACTIVATED WHEN THE RADAR ALTIMETER SHOWED A TERRAIN CLOSURE RATE OF APPROX 5000 FPM. THE WARNING WOULD HAVE CONTINUED UNTIL THE ACFT GAINED 300 FT OF PRESSURE ALT, WHICH IN OUR CASE NEVER HAPPENED. THIS SAME TYPE OF INCIDENT HAS OCCURRED WHILE FLYING THE LOC/DME BACK COURSE RWY 8 APCH AT MARTINSBURG, WV, AND WHILE BEING VECTORED AT ROANOKE, VA. IT IS RUMORED THAT THERE HAVE BEEN COMPLAINTS ABOUT THE LOC RWY 27 APCH AT SAN DIEGO, CA, AND COMPLAINTS FROM AIRLINES CONCERNING THE ASHVILLE, NC, AREA. I WONDER HOW MANY OTHER LOCATIONS THERE ARE WHERE THIS WILL OCCUR? HAD WE BEEN OPERATING IN IFR CONDITIONS, THE FLT MANUAL SUPPLEMENT WOULD HAVE REQUIRED US TO, 'EXECUTE A POSITIVE PULL UP, APPLY ENG PWR AND ASCEND AT THE BEST CLB ANGLE UNTIL THE WARNING CEASES.' HAD WE DONE THAT, WE WOULD HAVE CREATED A COLLISION HAZARD FOR ANY AIR TFC THAT MAY HAVE BEEN ABOVE US. THERE IS A NOTE IN THE FLT MANUAL SUPPLEMENT THAT STATES, 'WHEN OPS, AT SPECIFIC LOCATIONS, MUST BE CONDUCTED IN CLOSE PROX TO TERRAIN, THE GPWS/GND SPOILER FLAP OVERRIDE SWITCH MAY BE SET TO 'ON' TO DESENSITIZE THE TERRAIN CLOSURE RATE WARNING MODE.' IS THIS TO IMPLY THAT WE SHOULD OPERATE WITH THE OVERRIDE ON WHENEVER WE FLY AN APCH OR TAKE A RADAR VECTOR AT AN AREA WHERE WE HAVE NOT ACCOMPLISHED A DETAILED ANALYSIS? THIS SYS AND ALSO THE SYS INSTALLED IN ANOTHER TYPE ACFT HAVE GENERATED THESE WARNINGS. THE GPWS APPEARS TO BE FUNCTIONING EXACTLY AS DESIGNED. THE IFR APCH PROCS MUST MEET REQUIRED TERRAIN CLRNC REQUIREMENTS. IT APPEARS THAT THERE IS NO REQUIREMENT FOR THE DESIGN OF THE GPWS TO CORRELATE WITH THE DESIGN OF IFR APCH PROCS AND THE ASSOCIATED TERRAIN. AN INFORMAL INQUIRY TO AN FAA FLT INSPECTION UNIT REVEALED THAT ACFT THAT THEY USE TO CHK APCH PROCS ARE NOT EQUIPPED WITH GPWS. TO BE REQUIRED TO EXECUTE AN ABRUPT PULL UP WHILE FLYING A PUBLISHED PROC DOES NOT ENHANCE SAFETY. ON THE OTHER HAND, THE RECORD WILL SHOW THAT THERE HAVE BEEN A NUMBER OF ACCIDENTS THAT OCCURRED BECAUSE FLCS ELECTED TO IGNORE THE GPWS AND CONSEQUENTLY COLLIDED WITH THE GND. THE DESIGN CRITERIA FOR THE GPWS AND THE TERMINAL INSTS PROCS SHOULD BE CORRELATED TO PREVENT THESE FALSE WARNINGS.

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.