Air carrier medium large transport failed to follow clearance causing potential conflict.

Attributes
ACN	88742
Time
Date	198806
Day	Thu
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : mrb
State Reference	WV
Altitude	msl bound lower : 9000 msl bound upper : 11000
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Controlling Facilities	tracon : iad
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport
Flight Phase	descent other
Route In Use	enroute airway : zdc enroute airway : iad
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 120 flight time total : 14000 flight time type : 2000
ASRS Report	88742
Person 2
Function	flight crew : first officer
Qualification	pilot : commercial pilot : instrument
Events
Anomaly	altitude deviation : undershoot conflict : airborne less severe non adherence : clearance
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Flight Crew Human Performance
Air Traffic Incident	Pilot Deviation

Narrative:

At center had cleared medium large transport to cross mumsy intersection at 9000' since this is still 80 miles from our destination we requested a higher altitude to maintain airspeed above 250 KTS. Center said to make that request with dallas approach. We switched frequencys and requested 11000' in two separate xmissions. The approach controller answered our first transmission (signing on frequency) but, to the request for 11000 we heard only a click. About 30-60 seconds later we reported leaving 10000' for 9000 to which approach replied 'climb to 11000' traffic at 10000'' we immediately added power and returned to 11000'. If ATC is going to approve or change something they need to key their microphone, talk or transmit and then release the microphone button. They need to talk while the button is depressed and have the microphone button depressed long enough to complete their transmission. Since we did not get an approval for the altitude change we never acknowledged any transmission. If ATC doesn't get an acknowledgement they need to confirm that the aircraft crew got it.

Original NASA ASRS Text

Title: ACR MLG FAILED TO FOLLOW CLRNC CAUSING POTENTIAL CONFLICT.

Narrative: AT CENTER HAD CLRED MLG TO CROSS MUMSY INTERSECTION AT 9000' SINCE THIS IS STILL 80 MILES FROM OUR DEST WE REQUESTED A HIGHER ALT TO MAINTAIN AIRSPEED ABOVE 250 KTS. CENTER SAID TO MAKE THAT REQUEST WITH DALLAS APCH. WE SWITCHED FREQS AND REQUESTED 11000' IN TWO SEPARATE XMISSIONS. THE APCH CTLR ANSWERED OUR FIRST XMISSION (SIGNING ON FREQ) BUT, TO THE REQUEST FOR 11000 WE HEARD ONLY A CLICK. ABOUT 30-60 SECONDS LATER WE REPORTED LEAVING 10000' FOR 9000 TO WHICH APCH REPLIED 'CLIMB TO 11000' TFC AT 10000'' WE IMMEDIATELY ADDED POWER AND RETURNED TO 11000'. IF ATC IS GOING TO APPROVE OR CHANGE SOMETHING THEY NEED TO KEY THEIR MICROPHONE, TALK OR XMIT AND THEN RELEASE THE MICROPHONE BUTTON. THEY NEED TO TALK WHILE THE BUTTON IS DEPRESSED AND HAVE THE MIC BUTTON DEPRESSED LONG ENOUGH TO COMPLETE THEIR XMISSION. SINCE WE DID NOT GET AN APPROVAL FOR THE ALT CHANGE WE NEVER ACKNOWLEDGED ANY XMISSION. IF ATC DOESN'T GET AN ACKNOWLEDGEMENT THEY NEED TO CONFIRM THAT THE ACFT CREW GOT IT.

Data retrieved from NASA's ASRS site as of August 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.