 |
37000 Feet | Browse and search NASA's Aviation Safety Reporting System |
|
A seeming loss of separation between 2 jet aircraft in class a airspace with aircraft X having too high an altitude readout on their mode C 50 mi east of vhp, in.
| Attributes | |
| ACN | 575530 |
| Time | |
| Date | 200303 |
| Day | Tue |
| Local Time Of Day | 1201 To 1800 |
| Place | |
| Locale Reference | airport : ind.airport |
| State Reference | IN |
| Altitude | msl bound lower : 33000 msl bound upper : 33700 |
| Environment | |
| Flight Conditions | IMC |
| Light | Daylight |
| Aircraft 1 | |
| Controlling Facilities | artcc : zid.artcc |
| Operator | common carrier : charter |
| Make Model Name | Learjet 25 |
| Operating Under FAR Part | Part 135 |
| Navigation In Use | other |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Aircraft 2 | |
| Controlling Facilities | artcc : zid.artcc |
| Make Model Name | Commercial Fixed Wing |
| Flight Phase | cruise : level |
| Flight Plan | IFR |
| Person 1 | |
| Affiliation | company : charter |
| Function | flight crew : first officer |
| Qualification | pilot : atp |
| Experience | flight time last 90 days : 174 flight time total : 3826 flight time type : 526 |
| ASRS Report | 575530 |
| Person 2 | |
| Affiliation | company : charter |
| Function | flight crew : captain oversight : pic |
| Events | |
| Anomaly | aircraft equipment problem : less severe altitude deviation : overshoot conflict : airborne less severe non adherence : clearance non adherence : required legal separation other anomaly other |
| Independent Detector | atc equipment other atc equipment : radar mode c other controllera |
| Resolutory Action | controller : issued new clearance flight crew : returned to assigned altitude flight crew : took precautionary avoidance action |
| Miss Distance | vertical : 1850 |
| Supplementary | |
| Problem Areas | Navigational Facility Aircraft Flight Crew Human Performance |
| Primary Problem | Aircraft |
| Air Traffic Incident | Pilot Deviation |
Narrative:
ATC reported to us an aircraft at FL350 and queried our altitude. I responded (first officer) 'aircraft X level at FL330.' (altimeter actually read FL331.5 under autoplt control.) ATC responded we were reporting FL337 and climbing. I responded 'roger, descending' and we descended to FL328 (manually) in an effort to increase the distance between the aircraft. Based on the reported altitude and the position of the higher aircraft, it would appear separation between the 2 aircraft was lost. However, according to our altimeter (set at 29.92 inches), proper separation was always maintained. The same crew flew the aircraft for an additional 5 hours during the duty day with no further altitude reporting discrepancies. Unable to explain the discrepancy in altitude reporting between our transponder (set for mode a and C operation) and altimeter, or even to rule out an external event which may have caused the disconnect between actual and reported altitude. I have experienced similar events during my aviation career, but never in such proximity to another aircraft.
Original NASA ASRS Text
Title: A SEEMING LOSS OF SEPARATION BTWN 2 JET ACFT IN CLASS A AIRSPACE WITH ACFT X HAVING TOO HIGH AN ALT READOUT ON THEIR MODE C 50 MI E OF VHP, IN.
Narrative: ATC RPTED TO US AN ACFT AT FL350 AND QUERIED OUR ALT. I RESPONDED (FO) 'ACFT X LEVEL AT FL330.' (ALTIMETER ACTUALLY READ FL331.5 UNDER AUTOPLT CTL.) ATC RESPONDED WE WERE RPTING FL337 AND CLBING. I RESPONDED 'ROGER, DSNDING' AND WE DSNDED TO FL328 (MANUALLY) IN AN EFFORT TO INCREASE THE DISTANCE BTWN THE ACFT. BASED ON THE RPTED ALT AND THE POS OF THE HIGHER ACFT, IT WOULD APPEAR SEPARATION BTWN THE 2 ACFT WAS LOST. HOWEVER, ACCORDING TO OUR ALTIMETER (SET AT 29.92 INCHES), PROPER SEPARATION WAS ALWAYS MAINTAINED. THE SAME CREW FLEW THE ACFT FOR AN ADDITIONAL 5 HRS DURING THE DUTY DAY WITH NO FURTHER ALT RPTING DISCREPANCIES. UNABLE TO EXPLAIN THE DISCREPANCY IN ALT RPTING BTWN OUR XPONDER (SET FOR MODE A AND C OP) AND ALTIMETER, OR EVEN TO RULE OUT AN EXTERNAL EVENT WHICH MAY HAVE CAUSED THE DISCONNECT BTWN ACTUAL AND RPTED ALT. I HAVE EXPERIENCED SIMILAR EVENTS DURING MY AVIATION CAREER, BUT NEVER IN SUCH PROX TO ANOTHER ACFT.
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.