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An small transport flying in ZSE, wa, airspace encounters turbulence and finds it difficult to maintain altitude separation with another aircraft in a holding pattern.
| Attributes | |
| ACN | 388383 |
| Time | |
| Date | 199712 |
| Day | Tue |
| Local Time Of Day | 1801 To 2400 |
| Place | |
| Locale Reference | airport : pae |
| State Reference | WA |
| Altitude | msl bound lower : 3000 msl bound upper : 3600 |
| Environment | |
| Flight Conditions | Mixed |
| Light | Night |
| Aircraft 1 | |
| Controlling Facilities | artcc : zse tower : las |
| Operator | general aviation : instructional |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 91 |
| Flight Phase | descent : approach |
| Flight Plan | IFR |
| Aircraft 2 | |
| Make Model Name | Any Unknown or Unlisted Aircraft Manufacturer |
| Operating Under FAR Part | Part 91 |
| Flight Phase | other |
| Person 1 | |
| Affiliation | Other |
| Function | instruction : trainee |
| Qualification | pilot : commercial pilot : instrument |
| Experience | flight time total : 600 |
| ASRS Report | 388383 |
| Person 2 | |
| Affiliation | Other |
| Function | instruction : instructor |
| Qualification | pilot : cfi pilot : instrument |
| Events | |
| Anomaly | altitude deviation : excursion from assigned altitude conflict : airborne less severe inflight encounter : weather non adherence : clearance non adherence : required legal separation |
| Independent Detector | atc equipment other atc equipment : unspecified other controllera other flight crewa |
| Resolutory Action | other |
| Consequence | faa : reviewed incident with flight crew |
| Miss Distance | vertical : 400 |
| Supplementary | |
| Primary Problem | Flight Crew Human Performance |
| Air Traffic Incident | Pilot Deviation |
Narrative:
We were cleared for the ILS approach at paine field. WX was 2000 ft broken, 4000 ft broken, 7000 ft overcast. Winds out of the south at 20 KTS, gusting to 33 KTS. Winds aloft were as high as 40-55 KTS. We were cleared to 3000 ft and were told of an aircraft in a hold at nolla NDB at 4000 ft. We were IMC and had no visual contact. We were popping in and out of clouds and were experiencing moderate to severe turbulence with light mixed icing. Due to turbulence, our altitude was fluctuating +/-400 ft or so. We were trying to keep the aircraft in control more than anything. As we tracked the localizer inbound, we waited for a GS indication. There were no flags but the indications were unlikely (it showed us below GS when we should have been descending). We waited a bit to trust our intuitions, but with the altdevs due to turbulence and because of our not descending on GS when we should have (instrument error), the controller's alarm was set off (due to our proximity to the aircraft in the holding pattern) and we were asked to call center when we landed. We attempted the approach once more and then flew a visual approach in to boeing field (uneventful). GS was still indicating erroneously and without a flag. Frequencys idented properly. Upon calling center, we were told that our mode C was indicating us to be 600 ft off of our assigned altitude. Our indicated altitude (with correct altimeter setting) was off by a maximum of 400 ft in the worst turbulence, and the altitude fluctuations were rapid. It would have caused undue stress to chase them in such turbulence. We were always in control of the aircraft but we weren't accustomed to having so many adverse things come up at once.
Original NASA ASRS Text
Title: AN SMT FLYING IN ZSE, WA, AIRSPACE ENCOUNTERS TURB AND FINDS IT DIFFICULT TO MAINTAIN ALT SEPARATION WITH ANOTHER ACFT IN A HOLDING PATTERN.
Narrative: WE WERE CLRED FOR THE ILS APCH AT PAINE FIELD. WX WAS 2000 FT BROKEN, 4000 FT BROKEN, 7000 FT OVCST. WINDS OUT OF THE S AT 20 KTS, GUSTING TO 33 KTS. WINDS ALOFT WERE AS HIGH AS 40-55 KTS. WE WERE CLRED TO 3000 FT AND WERE TOLD OF AN ACFT IN A HOLD AT NOLLA NDB AT 4000 FT. WE WERE IMC AND HAD NO VISUAL CONTACT. WE WERE POPPING IN AND OUT OF CLOUDS AND WERE EXPERIENCING MODERATE TO SEVERE TURB WITH LIGHT MIXED ICING. DUE TO TURB, OUR ALT WAS FLUCTUATING +/-400 FT OR SO. WE WERE TRYING TO KEEP THE ACFT IN CTL MORE THAN ANYTHING. AS WE TRACKED THE LOC INBOUND, WE WAITED FOR A GS INDICATION. THERE WERE NO FLAGS BUT THE INDICATIONS WERE UNLIKELY (IT SHOWED US BELOW GS WHEN WE SHOULD HAVE BEEN DSNDING). WE WAITED A BIT TO TRUST OUR INTUITIONS, BUT WITH THE ALTDEVS DUE TO TURB AND BECAUSE OF OUR NOT DSNDING ON GS WHEN WE SHOULD HAVE (INST ERROR), THE CTLR'S ALARM WAS SET OFF (DUE TO OUR PROX TO THE ACFT IN THE HOLDING PATTERN) AND WE WERE ASKED TO CALL CTR WHEN WE LANDED. WE ATTEMPTED THE APCH ONCE MORE AND THEN FLEW A VISUAL APCH IN TO BOEING FIELD (UNEVENTFUL). GS WAS STILL INDICATING ERRONEOUSLY AND WITHOUT A FLAG. FREQS IDENTED PROPERLY. UPON CALLING CTR, WE WERE TOLD THAT OUR MODE C WAS INDICATING US TO BE 600 FT OFF OF OUR ASSIGNED ALT. OUR INDICATED ALT (WITH CORRECT ALTIMETER SETTING) WAS OFF BY A MAX OF 400 FT IN THE WORST TURB, AND THE ALT FLUCTUATIONS WERE RAPID. IT WOULD HAVE CAUSED UNDUE STRESS TO CHASE THEM IN SUCH TURB. WE WERE ALWAYS IN CTL OF THE ACFT BUT WE WEREN'T ACCUSTOMED TO HAVING SO MANY ADVERSE THINGS COME UP AT ONCE.
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.