An instructor and student pilot aboard a C172 were unable to maintain altitude in downdrafts and tur...

Narrative:

My instructor and I were over the north rim of the grand canyon mountain range at 11;500 MSL when we encountered moderate turbulence and a strong downdraft. Our ground speed was down to about 20 KTS; and the rate of descent was over 1;000 FPM; we were unable to maintain altitude and got below the assigned altitude by at least 1;500 ft. We advised ATC of the problem; but the quality of the radio reception was deteriorating; and we could not hear whether we were given an amended clearance for a lower altitude. We reversed the course; flew out of that area; climbed back to the initial altitude of 11;500 ft and contacted ATC. We requested to return back to pga and received clearance from denver center. Prior to that flight we checked the weather; and the winds were calm at the surface and about 30 KTS at 12;000 ft MSL; VFR; no significant weather. We were not familiar with the wind patterns over mountain ranges. This event could have been prevented by obtaining knowledge of mountain flying and the potential dangers that can be encountered. The second time we deviated from ATC instructions was on the way back to pga. We were both nervous after having encountered an uncontrolled descent into terrain a few minutes ago. We were cleared for a visual approach to page airport. I didn't know that 'cleared to land' didn't mean that we could switch the frequencies. I switched us to CTAF. My instructor did not notice my mistake either. After we landed; we called FSS and were told that denver center were 'looking for us'. Both deviations could've been prevented by better flight planning and CRM.

Original NASA ASRS Text

Title: An instructor and student pilot aboard a C172 were unable to maintain altitude in downdrafts and turbulence over the North Rim of the Grand Canyon. Had to reverse course to regain flight path control and return to their IFR altitude.

Narrative: My instructor and I were over the North Rim of the Grand Canyon mountain range at 11;500 MSL when we encountered moderate turbulence and a strong downdraft. Our ground speed was down to about 20 KTS; and the rate of descent was over 1;000 FPM; we were unable to maintain altitude and got below the assigned altitude by at least 1;500 FT. We advised ATC of the problem; but the quality of the radio reception was deteriorating; and we could not hear whether we were given an amended clearance for a lower altitude. We reversed the course; flew out of that area; climbed back to the initial altitude of 11;500 FT and contacted ATC. We requested to return back to PGA and received clearance from Denver Center. Prior to that flight we checked the weather; and the winds were calm at the surface and about 30 KTS at 12;000 FT MSL; VFR; no significant weather. We were not familiar with the wind patterns over mountain ranges. This event could have been prevented by obtaining knowledge of mountain flying and the potential dangers that can be encountered. The second time we deviated from ATC instructions was on the way back to PGA. We were both nervous after having encountered an uncontrolled descent into terrain a few minutes ago. We were cleared for a visual approach to Page airport. I didn't know that 'cleared to land' didn't mean that we could switch the frequencies. I switched us to CTAF. My instructor did not notice my mistake either. After we landed; we called FSS and were told that Denver Center were 'looking for us'. Both deviations could've been prevented by better flight planning and CRM.

Data retrieved from NASA's ASRS site as of April 2012 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.

Attributes
ACN	862263
Time
Date	200911
Local Time Of Day	1201-1800
Place
Locale Reference	GCN.VORTAC
State Reference	AZ
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Trainee
Qualification	Flight Crew Private
Experience	Flight Crew Last 90 Days 60 Flight Crew Total 120 Flight Crew Type 120
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter CFTT / CFIT Inflight Event / Encounter Weather / Turbulence Inflight Event / Encounter Loss Of Aircraft Control

An instructor and student pilot aboard a C172 were unable to maintain altitude in downdrafts and turbulence over the north rim of the grand canyon. Had to reverse course to regain flight path control and return to their IFR altitude.