A BE33 pilot, cruising at 14000 ft 30 NM east of ALS, encountered a mountain wave downdraft, requiri...

Attributes
ACN	536579
Time
Date	200201
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	navaid : als.vor
State Reference	CO
Altitude	msl bound lower : 13000 msl bound upper : 14000
Environment
Flight Conditions	Mixed
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zdv.artcc
Operator	general aviation : personal
Make Model Name	Bonanza 33
Operating Under FAR Part	Part 91
Navigation In Use	other other vortac
Route In Use	enroute airway : v210.airway
Flight Plan	IFR
Person 1
Affiliation	other
Function	flight crew : single pilot
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 45 flight time total : 1388 flight time type : 657
ASRS Report	536579
Person 2
Affiliation	government : faa
Function	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter other non adherence : far non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	controller : issued alert flight crew : returned to assigned altitude flight crew : exited adverse environment
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Weather Flight Crew Human Performance Environmental Factor
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

I was on an IFR flight plan cruising on V210 to alamosa at 14000 ft. I was in and out of IMC. Ride was smooth. About 15 NM east of bloke intersection, I encountered significant headwind and descending mountain wave. I pitched up to maintain altitude (MEA is 14000 ft) and applied full power. As my airspeed decreased to just above stall (the stall warning horn sounded), I needed to pitch down slightly and was unable to maintain altitude. I noted a GPS ground speed of 9 KTS. I called to inform ZDV. The controller reminded me of the MEA. I descended to not lower than 13000 ft before I was out of the wave and able to climb and maintain 14000 ft. I did maintain occasional sight of and reference to terrain. I entered visual conditions, canceled IFR and proceeded to alamosa, co. I have flown this route numerous times and have never encountered such a mountain wave. In the future, I will fly this route at not less than 16000 ft MSL when in IMC. I considered a 180 degree turn to leave the downdraft but with my airspeed so close to a stall, I felt it was not wise. I should have turned around at the first sign of downdraft instead of assuming it would be only short-lived. I know the principle of flying fast through downdrafts but high terrain necessitated my efforts to maintain altitude.

Original NASA ASRS Text

Title: A BE33 PLT, CRUISING AT 14000 FT 30 NM E OF ALS, ENCOUNTERED A MOUNTAIN WAVE DOWNDRAFT, REQUIRING HIM TO DSND IN ORDER TO REGAIN ACFT SPD CTL.

Narrative: I WAS ON AN IFR FLT PLAN CRUISING ON V210 TO ALAMOSA AT 14000 FT. I WAS IN AND OUT OF IMC. RIDE WAS SMOOTH. ABOUT 15 NM E OF BLOKE INTXN, I ENCOUNTERED SIGNIFICANT HEADWIND AND DSNDING MOUNTAIN WAVE. I PITCHED UP TO MAINTAIN ALT (MEA IS 14000 FT) AND APPLIED FULL PWR. AS MY AIRSPD DECREASED TO JUST ABOVE STALL (THE STALL WARNING HORN SOUNDED), I NEEDED TO PITCH DOWN SLIGHTLY AND WAS UNABLE TO MAINTAIN ALT. I NOTED A GPS GND SPD OF 9 KTS. I CALLED TO INFORM ZDV. THE CTLR REMINDED ME OF THE MEA. I DSNDED TO NOT LOWER THAN 13000 FT BEFORE I WAS OUT OF THE WAVE AND ABLE TO CLB AND MAINTAIN 14000 FT. I DID MAINTAIN OCCASIONAL SIGHT OF AND REF TO TERRAIN. I ENTERED VISUAL CONDITIONS, CANCELED IFR AND PROCEEDED TO ALAMOSA, CO. I HAVE FLOWN THIS RTE NUMEROUS TIMES AND HAVE NEVER ENCOUNTERED SUCH A MOUNTAIN WAVE. IN THE FUTURE, I WILL FLY THIS RTE AT NOT LESS THAN 16000 FT MSL WHEN IN IMC. I CONSIDERED A 180 DEG TURN TO LEAVE THE DOWNDRAFT BUT WITH MY AIRSPD SO CLOSE TO A STALL, I FELT IT WAS NOT WISE. I SHOULD HAVE TURNED AROUND AT THE FIRST SIGN OF DOWNDRAFT INSTEAD OF ASSUMING IT WOULD BE ONLY SHORT-LIVED. I KNOW THE PRINCIPLE OF FLYING FAST THROUGH DOWNDRAFTS BUT HIGH TERRAIN NECESSITATED MY EFFORTS TO MAINTAIN ALT.

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.

A BE33 pilot, cruising at 14000 ft 30 NM east of ALS, encountered a mountain wave downdraft, requiring him to descend in order to regain aircraft speed control.