<< >> NASA ASRS Report 306006, May 1995

Altitude deviation altitude excursion as small aircraft encounters strong updrafts in proximity of designated mountainous terrain.

Attributes
ACN	306006
Time
Date	199505
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	atc facility : zob
State Reference	OH
Altitude	msl bound lower : 6000 msl bound upper : 6500
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zob
Make Model Name	Any Unknown or Unlisted Aircraft Manufacturer
Operating Under FAR Part	Part 91
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : private pilot : instrument
Experience	flight time last 90 days : 51 flight time total : 665
ASRS Report	306006
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude conflict : airborne less severe inflight encounter : weather non adherence : clearance non adherence : required legal separation other anomaly
Independent Detector	other controllera other flight crewa
Resolutory Action	flight crew : regained aircraft control flight crew : returned to intended course or assigned course
Consequence	faa : investigated faa : reviewed incident with flight crew
Miss Distance	horizontal : 500
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

WX related incident. After leveloff at an assigned altitude of 6000 ft MSL, my aircraft was carried 500 ft above my assigned altitude by a strong updraft, while crossing the alleghanney mountains, causing a loss of separation with another aircraft. At 6200 ft I felt g-forces and observed an uncommanded climb. I throttled back to 20 inches of manifold pressure and pitched 5 degrees down but the climb continued to 6500 ft at a rapid rate. I then pitched down 10 degrees which arrested the climb and brought my aircraft back to the assigned altitude. I was in solid IMC at this time. I was later informed by ATC that my altitude incursion had caused them to lose separation with another aircraft. I believe this incident could have been prevented had I been paying more attention to altitude control and the effects of mountain wave WX conditions on my aircraft.

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Original NASA ASRS Text

Title: ALTDEV ALT EXCURSION AS SMA ENCOUNTERS STRONG UPDRAFTS IN PROX OF DESIGNATED MOUNTAINOUS TERRAIN.

Narrative: WX RELATED INCIDENT. AFTER LEVELOFF AT AN ASSIGNED ALT OF 6000 FT MSL, MY ACFT WAS CARRIED 500 FT ABOVE MY ASSIGNED ALT BY A STRONG UPDRAFT, WHILE XING THE ALLEGHANNEY MOUNTAINS, CAUSING A LOSS OF SEPARATION WITH ANOTHER ACFT. AT 6200 FT I FELT G-FORCES AND OBSERVED AN UNCOMMANDED CLB. I THROTTLED BACK TO 20 INCHES OF MANIFOLD PRESSURE AND PITCHED 5 DEGS DOWN BUT THE CLB CONTINUED TO 6500 FT AT A RAPID RATE. I THEN PITCHED DOWN 10 DEGS WHICH ARRESTED THE CLB AND BROUGHT MY ACFT BACK TO THE ASSIGNED ALT. I WAS IN SOLID IMC AT THIS TIME. I WAS LATER INFORMED BY ATC THAT MY ALT INCURSION HAD CAUSED THEM TO LOSE SEPARATION WITH ANOTHER ACFT. I BELIEVE THIS INCIDENT COULD HAVE BEEN PREVENTED HAD I BEEN PAYING MORE ATTN TO ALT CTL AND THE EFFECTS OF MOUNTAIN WAVE WX CONDITIONS ON MY 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.