A PA28 pilot descends near terrain when he misinterprets his clearance. The alert approach controlle...

Attributes
ACN	384696
Time
Date	199711
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : baf
State Reference	MA
Altitude	msl bound lower : 2000 msl bound upper : 3000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : bdl
Operator	general aviation : personal
Make Model Name	PA-28 Cherokee/Archer II/Dakota/Pillan/Warrior
Operating Under FAR Part	Part 91
Flight Phase	descent other other
Route In Use	enroute : on vectors
Flight Plan	IFR
Person 1
Affiliation	Other
Function	flight crew : single pilot
Qualification	pilot : cfi pilot : instrument pilot : commercial
Experience	flight time last 90 days : 55 flight time total : 940 flight time type : 150
ASRS Report	384696
Person 2
Affiliation	government : faa
Function	controller : approach
Qualification	controller : radar
Events
Anomaly	altitude deviation : excursion from assigned altitude altitude deviation : overshoot inflight encounter : weather non adherence : clearance non adherence : far other spatial deviation
Independent Detector	atc equipment other atc equipment : unspecified other controllera
Resolutory Action	other other
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

While IMC halfway towards the destination (total flight of 120 mi) I encountered severe turbulence. It was difficult to maintain altitude and attitude. At some point the aircraft descended approximately 700 ft from the assigned altitude. ATC informed me of the assigned altitude and I replied that it was difficult to maintain altitude due to turbulence. I then asked to land at a nearby airport instead of the planned destination. I had also asked about what the ATC radar was painting and was informed that there was level 3 precipitation in the area, and that a heading of 090 degrees would get the aircraft out of it. I turned towards that heading, then was given a different heading towards the airport for the approach. I was cleared first down to 4000 ft. Then was cleared down to 2000 ft. I heard 'descend to 2000 ft,' and read back to the controller, 'descend to 2000 ft.' soon after reaching 2000 ft the controller called and said, 'climb immediately, climb immediately. Altitude alert, climb to 2500 ft.' due to the turbulence and downdrafts it was difficult to climb and the controller repeated a similar warning before I was up to 2500 ft. I believe the controller was mistaken when he issued the clearance to descend to 2000 ft. I am sure that I read back 2000 ft. I don't know what terrain was in the area, however I know that there is some terrain in that general area that is near this altitude. I believe that the turbulence due to the severe WX, combined with the controller miscom led to this potentially dangerous situation.

Original NASA ASRS Text

Title: A PA28 PLT DSNDS NEAR TERRAIN WHEN HE MISINTERPRETS HIS CLRNC. THE ALERT APCH CTLR SAVES HIM FROM TERRAIN IN THE AREA. REF ACN 384695.

Narrative: WHILE IMC HALFWAY TOWARDS THE DEST (TOTAL FLT OF 120 MI) I ENCOUNTERED SEVERE TURB. IT WAS DIFFICULT TO MAINTAIN ALT AND ATTITUDE. AT SOME POINT THE ACFT DSNDED APPROX 700 FT FROM THE ASSIGNED ALT. ATC INFORMED ME OF THE ASSIGNED ALT AND I REPLIED THAT IT WAS DIFFICULT TO MAINTAIN ALT DUE TO TURB. I THEN ASKED TO LAND AT A NEARBY ARPT INSTEAD OF THE PLANNED DEST. I HAD ALSO ASKED ABOUT WHAT THE ATC RADAR WAS PAINTING AND WAS INFORMED THAT THERE WAS LEVEL 3 PRECIPITATION IN THE AREA, AND THAT A HDG OF 090 DEGS WOULD GET THE ACFT OUT OF IT. I TURNED TOWARDS THAT HEADING, THEN WAS GIVEN A DIFFERENT HEADING TOWARDS THE ARPT FOR THE APCH. I WAS CLRED FIRST DOWN TO 4000 FT. THEN WAS CLRED DOWN TO 2000 FT. I HEARD 'DSND TO 2000 FT,' AND READ BACK TO THE CTLR, 'DSND TO 2000 FT.' SOON AFTER REACHING 2000 FT THE CTLR CALLED AND SAID, 'CLB IMMEDIATELY, CLB IMMEDIATELY. ALT ALERT, CLB TO 2500 FT.' DUE TO THE TURB AND DOWNDRAFTS IT WAS DIFFICULT TO CLB AND THE CTLR REPEATED A SIMILAR WARNING BEFORE I WAS UP TO 2500 FT. I BELIEVE THE CTLR WAS MISTAKEN WHEN HE ISSUED THE CLRNC TO DSND TO 2000 FT. I AM SURE THAT I READ BACK 2000 FT. I DON'T KNOW WHAT TERRAIN WAS IN THE AREA, HOWEVER I KNOW THAT THERE IS SOME TERRAIN IN THAT GENERAL AREA THAT IS NEAR THIS ALT. I BELIEVE THAT THE TURB DUE TO THE SEVERE WX, COMBINED WITH THE CTLR MISCOM LED TO THIS POTENTIALLY DANGEROUS SIT.

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 PA28 pilot descends near terrain when he misinterprets his clearance. The alert approach controller saves him from terrain in the area. Reference acn 384695.