DC3 cargo flight encounters descending air mass resulting in loss of altitude.

Attributes
ACN	332185
Time
Date	199603
Day	Fri
Local Time Of Day	0001 To 0600
Place
Locale Reference	atc facility : lou
State Reference	KY
Altitude	msl bound lower : 11500 msl bound upper : 12000
Environment
Flight Conditions	Mixed
Light	Night
Aircraft 1
Controlling Facilities	artcc : zid
Operator	common carrier : air taxi
Make Model Name	DC-3/Dakota/Skytrain
Operating Under FAR Part	Part 135
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air taxi
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 250 flight time total : 3000 flight time type : 800
ASRS Report	332185
Person 2
Affiliation	company : air taxi
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Experience	flight time last 90 days : 150 flight time total : 1400 flight time type : 1000
ASRS Report	332379
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather non adherence : clearance other anomaly
Independent Detector	other flight crewa
Resolutory Action	flight crew : exited adverse environment flight crew : declared emergency other other
Consequence	Other
Miss Distance	horizontal : 15000 vertical : 500
Supplementary
Primary Problem	Weather
Air Traffic Incident	Pilot Deviation

Narrative:

During cruise flight at 12000 ft, due to what I can only guess as a descending area of air, the aircraft began to lose airspeed while trying to maintain altitude. After a few mins of this, the aircraft had slowed from about 115 KTS to about 90 KTS and descended to about 11800 ft. In hopes of soon flying out of the descending air, no power was added above the 50 percent cruise which was already set. The whole time, we were flying in and out of a scattered layer of clouds. Then we flew through a cloud which had in it moderate turbulence or windshear, we began to lose more airspeed which was corrected for by lowering the nose, which, in turn, sacrificed another 200-300 ft of altitude. By now, ATC started to inquire about our altitude (11500 ft) and warned us of another aircraft that was below us at 11000 ft and at our 2-3 O'clock position, and I think, 3 mi. At about this time, we exited the cloud. The controller then asked if we needed to declare an emergency. To this I responded that yes, we are declaring an emergency. We then added maximum power and within 1 min had climbed back up to 12000 ft. After normal cruise airspeed was recovered, we set normal cruise power and told the controller that the problem was solved and we are rescinding the emergency. About 20 mi further along, after we had time to regroup and figure out what had happened, we issued a PIREP for turbulence. The flight was continued to our destination without further incident.

Original NASA ASRS Text

Title: DC3 CARGO FLT ENCOUNTERS DSNDING AIR MASS RESULTING IN LOSS OF ALT.

Narrative: DURING CRUISE FLT AT 12000 FT, DUE TO WHAT I CAN ONLY GUESS AS A DSNDING AREA OF AIR, THE ACFT BEGAN TO LOSE AIRSPD WHILE TRYING TO MAINTAIN ALT. AFTER A FEW MINS OF THIS, THE ACFT HAD SLOWED FROM ABOUT 115 KTS TO ABOUT 90 KTS AND DSNDED TO ABOUT 11800 FT. IN HOPES OF SOON FLYING OUT OF THE DSNDING AIR, NO PWR WAS ADDED ABOVE THE 50 PERCENT CRUISE WHICH WAS ALREADY SET. THE WHOLE TIME, WE WERE FLYING IN AND OUT OF A SCATTERED LAYER OF CLOUDS. THEN WE FLEW THROUGH A CLOUD WHICH HAD IN IT MODERATE TURB OR WINDSHEAR, WE BEGAN TO LOSE MORE AIRSPD WHICH WAS CORRECTED FOR BY LOWERING THE NOSE, WHICH, IN TURN, SACRIFICED ANOTHER 200-300 FT OF ALT. BY NOW, ATC STARTED TO INQUIRE ABOUT OUR ALT (11500 FT) AND WARNED US OF ANOTHER ACFT THAT WAS BELOW US AT 11000 FT AND AT OUR 2-3 O'CLOCK POS, AND I THINK, 3 MI. AT ABOUT THIS TIME, WE EXITED THE CLOUD. THE CTLR THEN ASKED IF WE NEEDED TO DECLARE AN EMER. TO THIS I RESPONDED THAT YES, WE ARE DECLARING AN EMER. WE THEN ADDED MAX PWR AND WITHIN 1 MIN HAD CLBED BACK UP TO 12000 FT. AFTER NORMAL CRUISE AIRSPD WAS RECOVERED, WE SET NORMAL CRUISE PWR AND TOLD THE CTLR THAT THE PROB WAS SOLVED AND WE ARE RESCINDING THE EMER. ABOUT 20 MI FURTHER ALONG, AFTER WE HAD TIME TO REGROUP AND FIGURE OUT WHAT HAD HAPPENED, WE ISSUED A PIREP FOR TURB. THE FLT WAS CONTINUED TO OUR DEST WITHOUT FURTHER INCIDENT.

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.