WX factors cause MD80 speed loss requiring immediate descent as they simultaneously advise ZTL.

Attributes
ACN	547048
Time
Date	200205
Day	Mon
Local Time Of Day	1201 To 1800
Place
Locale Reference	navaid : vxv.vortac
State Reference	TN
Altitude	msl bound lower : 31000 msl bound upper : 35000
Environment
Flight Conditions	IMC
Weather Elements	Ice Thunderstorm Turbulence
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : ztl.artcc
Operator	common carrier : air carrier
Make Model Name	MD-80 Series (DC-9-80) Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Navigation In Use	other
Flight Phase	cruise : enroute altitude change
Flight Plan	IFR
Person 1
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Experience	controller limited radar : 20 controller military : 0 controller non radar : 20 controller radar : 20 controller supervisory : 0.25 controller time certified in position1 : 20
ASRS Report	547048
Person 2
Affiliation	government : faa
Function	controller : radar
Qualification	controller : radar
Events
Anomaly	airspace violation : entry altitude deviation : excursion from assigned altitude inflight encounter : weather inflight encounter : turbulence inflight encounter other other anomaly other anomaly maintenance problem : improper maintenance
Independent Detector	other flight crewa
Resolutory Action	controller : issued alert controller : provided flight assist flight crew : took evasive action flight crew : regained aircraft control flight crew : exited adverse environment other
Consequence	faa : reviewed incident with flight crew
Supplementary
Problem Areas	Environmental Factor Flight Crew Human Performance Weather ATC Human Performance
Primary Problem	Weather

Narrative:

Aircraft was in level flight at FL350, with some deviations off course due to WX. At XA35 the pilot unexpectedly announced 'air carrier X, we need to change altitude right now.' since I did not control the airspace below FL350, I was unable to provide a descent clearance right away. The pilot initiated a descent and I advised the pilot that I was declaring an emergency and to please fill me in on the situation when circumstances permitted. During this time, coordination with the sector below me was being performed and it was determined that no aircraft were in confliction. Subsequent discussion with the pilot indicated that, due to turbulence, the aircraft was unexpectedly unable to maintain altitude. After descending to about FL330, the pilot indicated that he could then climb back to FL350. I offered the pilot a climb back to FL350 or descent down to FL310. The pilot asked for and received clearance to FL310. Because I was sitting immediately adjacent to the controller with airspace below me, I was able to coordinate the un-cleared descent quickly enough to avoid cascading problems with other aircraft. Supplemental information from acn 547375: aircraft was in cruise flight at FL350 with airfoil and engine anti-ice on. Flight was in IMC deviating to the east of thunderstorms. Aircraft speed increased initially from .76 to .78 mach, then deteriorated to .69 mach. Performance did not increase so we immediately descended to lower altitude to regain speed and aircraft control. There was no time to request and receive clearance for the altitude change. I believe we must have flown into relatively warm, moist air blowing off the top of a storm to our left, causing marked deterioration in aircraft performance.

Original NASA ASRS Text

Title: WX FACTORS CAUSE MD80 SPD LOSS REQUIRING IMMEDIATE DSCNT AS THEY SIMULTANEOUSLY ADVISE ZTL.

Narrative: ACFT WAS IN LEVEL FLT AT FL350, WITH SOME DEVS OFF COURSE DUE TO WX. AT XA35 THE PLT UNEXPECTEDLY ANNOUNCED 'ACR X, WE NEED TO CHANGE ALT RIGHT NOW.' SINCE I DID NOT CTL THE AIRSPACE BELOW FL350, I WAS UNABLE TO PROVIDE A DSCNT CLRNC RIGHT AWAY. THE PLT INITIATED A DSCNT AND I ADVISED THE PLT THAT I WAS DECLARING AN EMER AND TO PLEASE FILL ME IN ON THE SIT WHEN CIRCUMSTANCES PERMITTED. DURING THIS TIME, COORD WITH THE SECTOR BELOW ME WAS BEING PERFORMED AND IT WAS DETERMINED THAT NO ACFT WERE IN CONFLICTION. SUBSEQUENT DISCUSSION WITH THE PLT INDICATED THAT, DUE TO TURB, THE ACFT WAS UNEXPECTEDLY UNABLE TO MAINTAIN ALT. AFTER DSNDING TO ABOUT FL330, THE PLT INDICATED THAT HE COULD THEN CLB BACK TO FL350. I OFFERED THE PLT A CLB BACK TO FL350 OR DSCNT DOWN TO FL310. THE PLT ASKED FOR AND RECEIVED CLRNC TO FL310. BECAUSE I WAS SITTING IMMEDIATELY ADJACENT TO THE CTLR WITH AIRSPACE BELOW ME, I WAS ABLE TO COORDINATE THE UN-CLRED DSCNT QUICKLY ENOUGH TO AVOID CASCADING PROBS WITH OTHER ACFT. SUPPLEMENTAL INFO FROM ACN 547375: ACFT WAS IN CRUISE FLT AT FL350 WITH AIRFOIL AND ENG ANTI-ICE ON. FLT WAS IN IMC DEVIATING TO THE E OF TSTMS. ACFT SPD INCREASED INITIALLY FROM .76 TO .78 MACH, THEN DETERIORATED TO .69 MACH. PERFORMANCE DID NOT INCREASE SO WE IMMEDIATELY DSNDED TO LOWER ALT TO REGAIN SPD AND ACFT CTL. THERE WAS NO TIME TO REQUEST AND RECEIVE CLRNC FOR THE ALT CHANGE. I BELIEVE WE MUST HAVE FLOWN INTO RELATIVELY WARM, MOIST AIR BLOWING OFF THE TOP OF A STORM TO OUR L, CAUSING MARKED DETERIORATION IN ACFT PERFORMANCE.

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.