Shorts encounters severe downdraft at level off. Altitude deviation.

Attributes
ACN	317208
Time
Date	199510
Day	Sun
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : gum
State Reference	GU
Altitude	msl bound lower : 2400 msl bound upper : 2800
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zua
Operator	common carrier : air carrier
Make Model Name	Shorts SD-360
Operating Under FAR Part	Part 135
Flight Phase	descent other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : cfi pilot : atp
Experience	flight time last 90 days : 200 flight time total : 5290 flight time type : 800
ASRS Report	317208
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : excursion from assigned altitude inflight encounter : weather
Independent Detector	other flight crewa
Resolutory Action	flight crew : returned to intended course or assigned course
Consequence	Other
Supplementary
Primary Problem	Weather
Air Traffic Incident	other

Narrative:

Flight saipan to rota. Guam center issued pilot's discretion to 2800 ft. We departed 4000 ft for 2800 ft. There was broken to overcast layer with ceilings at 3000 ft in vicinity of destination (rota). Cloud types were cumulus type of various size and development. Upon reaching our altitude of 2800 ft, we encountered turbulence. We were IMC at the time. Soon thereafter we encountered a strong downdraft resulting in altitude deviation of 350-400 ft below our assigned altitude. Simultaneously I called for maximum power and pitch increase to correct altitude loss. Within 3 seconds we had returned to our assigned altitude of 2800 ft.

Original NASA ASRS Text

Title: SHORTS ENCOUNTERS SEVERE DOWNDRAFT AT LEVEL OFF. ALTDEV.

Narrative: FLT SAIPAN TO ROTA. GUAM CTR ISSUED PLT'S DISCRETION TO 2800 FT. WE DEPARTED 4000 FT FOR 2800 FT. THERE WAS BROKEN TO OVCST LAYER WITH CEILINGS AT 3000 FT IN VICINITY OF DEST (ROTA). CLOUD TYPES WERE CUMULUS TYPE OF VARIOUS SIZE AND DEVELOPMENT. UPON REACHING OUR ALT OF 2800 FT, WE ENCOUNTERED TURB. WE WERE IMC AT THE TIME. SOON THEREAFTER WE ENCOUNTERED A STRONG DOWNDRAFT RESULTING IN ALTDEV OF 350-400 FT BELOW OUR ASSIGNED ALT. SIMULTANEOUSLY I CALLED FOR MAX PWR AND PITCH INCREASE TO CORRECT ALT LOSS. WITHIN 3 SECONDS WE HAD RETURNED TO OUR ASSIGNED ALT OF 2800 FT.

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.