Confusion regarding crossing clearance. Missed by 30 miles.

Attributes
ACN	129902
Time
Date	198911
Day	Thu
Local Time Of Day	1801 To 2400
Place
Locale Reference	atc facility : fak
State Reference	VA
Altitude	msl bound lower : 27000 msl bound upper : 33000
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Flight Phase	cruise other
Route In Use	enroute airway : j51
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 210 flight time total : 14000 flight time type : 4000
ASRS Report	129902
Person 2
Affiliation	company : air carrier
Function	flight crew : first officer
Qualification	pilot : instrument pilot : commercial
Events
Anomaly	altitude deviation : undershoot non adherence : clearance other anomaly other
Independent Detector	other controllera
Resolutory Action	controller : issued new clearance
Consequence	Other
Supplementary
Primary Problem	Ambiguous
Air Traffic Incident	other

Narrative:

At 82 DME, ZDC asked us for our DME from fak. When we stated 82, he asked us what our clearance was. We replied, 'to cross 50 south of fak at FL270.' he then informed us that our instructions were to cross 80 south of fak at FL270. After a rapid descent, we reached FL270 at 74 DME. In reviewing with the copilot, we still felt the original clearance was 50 mi, and I had written this figure on my clipboard for use as a reference at the time it was received. ATC said that we (first officer) had been given and read back 80 mi. A F/a was in the cockpit reporting a minor cabin discrepancy when the clearance was received. It is becoming increasingly more obvious that communications can be a very fragile thing, both inside the cockpit and with ATC. This is especially true when operating as a 2-M crew over 5-6 segments daily in high-density traffic with 2 cockpit crew members, plus ATC controller following the progress of a flight. This should not have happened, but it did.

Original NASA ASRS Text

Title: CONFUSION REGARDING CROSSING CLRNC. MISSED BY 30 MILES.

Narrative: AT 82 DME, ZDC ASKED US FOR OUR DME FROM FAK. WHEN WE STATED 82, HE ASKED US WHAT OUR CLRNC WAS. WE REPLIED, 'TO CROSS 50 S OF FAK AT FL270.' HE THEN INFORMED US THAT OUR INSTRUCTIONS WERE TO CROSS 80 S OF FAK AT FL270. AFTER A RAPID DSCNT, WE REACHED FL270 AT 74 DME. IN REVIEWING WITH THE COPLT, WE STILL FELT THE ORIGINAL CLRNC WAS 50 MI, AND I HAD WRITTEN THIS FIGURE ON MY CLIPBOARD FOR USE AS A REF AT THE TIME IT WAS RECEIVED. ATC SAID THAT WE (F/O) HAD BEEN GIVEN AND READ BACK 80 MI. A F/A WAS IN THE COCKPIT RPTING A MINOR CABIN DISCREPANCY WHEN THE CLRNC WAS RECEIVED. IT IS BECOMING INCREASINGLY MORE OBVIOUS THAT COMS CAN BE A VERY FRAGILE THING, BOTH INSIDE THE COCKPIT AND WITH ATC. THIS IS ESPECIALLY TRUE WHEN OPERATING AS A 2-M CREW OVER 5-6 SEGMENTS DAILY IN HIGH-DENSITY TFC WITH 2 COCKPIT CREW MEMBERS, PLUS ATC CTLR FOLLOWING THE PROGRESS OF A FLT. THIS SHOULD NOT HAVE HAPPENED, BUT IT DID.

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.