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Air taxi cargo aircraft on approach has GS needle stick in centered position. Altitude deviation results.
| Attributes | |
| ACN | 345101 |
| Time | |
| Date | 199608 |
| Day | Wed |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : jfk |
| State Reference | NY |
| Altitude | msl bound lower : 1000 msl bound upper : 1500 |
| Environment | |
| Flight Conditions | Marginal |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | tracon : jfk |
| Operator | common carrier : air taxi |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 135 |
| Flight Phase | descent : approach |
| Route In Use | enroute : on vectors |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | other : unknown |
| Flight Phase | descent : approach |
| Person 1 | |
| Affiliation | company : air taxi |
| Function | flight crew : captain oversight : pic |
| Qualification | pilot : atp pilot : cfi pilot : instrument |
| Experience | flight time last 90 days : 160 flight time total : 6700 flight time type : 600 |
| ASRS Report | 345101 |
| Person 2 | |
| Affiliation | company : air taxi |
| Function | flight crew : first officer |
| Qualification | pilot : commercial pilot : instrument |
| Events | |
| Anomaly | aircraft equipment problem : critical altitude deviation : excursion from assigned altitude other anomaly other |
| Independent Detector | other flight crewa |
| Resolutory Action | flight crew : returned to intended course or assigned course other |
| Consequence | Other |
| Miss Distance | horizontal : 0 vertical : 500 |
| Supplementary | |
| Primary Problem | Aircraft |
| Air Traffic Incident | other |
Narrative:
On aug/xa/96, I was approaching jfk on radar vectors, after getting established on the ILS for runway 31R, I was cleared for the approach. I had only been on the localizer for maybe 15 seconds before I got GS indication. GS needle moved from the bottom towards the 'diamond,' (that indicates on the GS) and stopped on the 'diamond.' assuming I was on the GS I started my descent towards DH. Intercept altitude was 1500 ft and I was coming up on 1000 ft when jfk tower gave me an altitude alert and advised me to climb back to 1500 ft. From this point everything worked normally, landing uneventfully at jfk. Upon returning home on aug/xb/96, the PIC's GS was acting up again, this time we used the sic's HSI and everything was normal. When avionics checked the GS they found the GS needle physically sticking on the 'diamond' which symbol is a plastic piece protruding the GS 'scale,' (not painted marks). This was leaving no GS warning flags to indicate a problem, just a 'picture perfect' ILS with a not so perfect position outcome! This problem has in newer aircraft been corrected by a comparable warning system, but in the aging fleet of charter aircraft, this is normally not installed. All this ended well thanks to jfk tower vigilance and not too bad WX. Had we been in no radar environment or WX down to minimums, I can only imagine the potential outcome. Callback conversation with reporter revealed the following information: reporter states the aircraft was a merlin iv, metropolitan. The unit was removed and sent to the manufacturer for repair. As reporter states the newer instruments do not have the protruding mark but instead have a painted insignia. The aircraft was grounded and a lender unit installed while the removed instrument was sent to the manufacturer. The unit is a collins HSI #105. Universal parts number is 7876385-002. Serial #591. Reporter feels strongly that the aviation community should know about this problem.
Original NASA ASRS Text
Title: AIR TAXI CARGO ACFT ON APCH HAS GS NEEDLE STICK IN CTRED POS. ALTDEV RESULTS.
Narrative: ON AUG/XA/96, I WAS APCHING JFK ON RADAR VECTORS, AFTER GETTING ESTABLISHED ON THE ILS FOR RWY 31R, I WAS CLRED FOR THE APCH. I HAD ONLY BEEN ON THE LOC FOR MAYBE 15 SECONDS BEFORE I GOT GS INDICATION. GS NEEDLE MOVED FROM THE BOTTOM TOWARDS THE 'DIAMOND,' (THAT INDICATES ON THE GS) AND STOPPED ON THE 'DIAMOND.' ASSUMING I WAS ON THE GS I STARTED MY DSCNT TOWARDS DH. INTERCEPT ALT WAS 1500 FT AND I WAS COMING UP ON 1000 FT WHEN JFK TWR GAVE ME AN ALT ALERT AND ADVISED ME TO CLB BACK TO 1500 FT. FROM THIS POINT EVERYTHING WORKED NORMALLY, LNDG UNEVENTFULLY AT JFK. UPON RETURNING HOME ON AUG/XB/96, THE PIC'S GS WAS ACTING UP AGAIN, THIS TIME WE USED THE SIC'S HSI AND EVERYTHING WAS NORMAL. WHEN AVIONICS CHKED THE GS THEY FOUND THE GS NEEDLE PHYSICALLY STICKING ON THE 'DIAMOND' WHICH SYMBOL IS A PLASTIC PIECE PROTRUDING THE GS 'SCALE,' (NOT PAINTED MARKS). THIS WAS LEAVING NO GS WARNING FLAGS TO INDICATE A PROB, JUST A 'PICTURE PERFECT' ILS WITH A NOT SO PERFECT POS OUTCOME! THIS PROB HAS IN NEWER ACFT BEEN CORRECTED BY A COMPARABLE WARNING SYS, BUT IN THE AGING FLEET OF CHARTER ACFT, THIS IS NORMALLY NOT INSTALLED. ALL THIS ENDED WELL THANKS TO JFK TWR VIGILANCE AND NOT TOO BAD WX. HAD WE BEEN IN NO RADAR ENVIRONMENT OR WX DOWN TO MINIMUMS, I CAN ONLY IMAGINE THE POTENTIAL OUTCOME. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATES THE ACFT WAS A MERLIN IV, METRO. THE UNIT WAS REMOVED AND SENT TO THE MANUFACTURER FOR REPAIR. AS RPTR STATES THE NEWER INSTS DO NOT HAVE THE PROTRUDING MARK BUT INSTEAD HAVE A PAINTED INSIGNIA. THE ACFT WAS GNDED AND A LENDER UNIT INSTALLED WHILE THE REMOVED INST WAS SENT TO THE MANUFACTURER. THE UNIT IS A COLLINS HSI #105. UNIVERSAL PARTS NUMBER IS 7876385-002. SERIAL #591. RPTR FEELS STRONGLY THAT THE AVIATION COMMUNITY SHOULD KNOW ABOUT THIS PROB.
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.