A pilot read back a clearance to cross 50 northwest of apa at 15;000 ft but the the crew leveled at ...

Narrative:

During the initial descent we were given a crossing restriction of 'cross 50 NM northwest of apa at 15;000.' I read back the clearance and continued the descent. As we were completing the descent nearing denver approach's airspace we realized that we were descending to 15;000 and longs peak was straight ahead of us approximately 20 NM. Our local knowledge of the mountains we knew this mountain to be over 14;000 ft tall. The captain leveled off our descent at 16;000 ft MSL. The captain asked me to confirm our altitude with ATC. We made an attempt to confirm but due to frequency congestion we received no response. A few transmissions later by ATC we were told to climb and maintain 17;000. We complied and had already started a slow climb. During this entire event we had terrain in sight and no immediate action was required to avoid the terrain. Upon landing the captain called denver center and spoke with the center and he advised us that the controller cleared the aircraft to 'cross 50 NM northwest of apa at 17;000.' I read back the 'cross 50 northwest at 15;000.' however the controller did not catch our incorrect read back of the altitude assignment.it would seem the captain's attention to local flight patterns caught the problem before ATC notified us. Secondly; if we were able to confirm our altitude clearance as we had tried before the deviation we could have leveled off at the correct altitude. The frequency congestion delayed our ability to clarify the clearance with ATC.

Original NASA ASRS Text

Title: A pilot read back a clearance to cross 50 northwest of APA at 15;000 FT but the the crew leveled at 16;000 FT because of high terrain knowledge and was then notified by ATC that the descent clearance was to 17;000 FT.

Narrative: During the initial descent we were given a crossing restriction of 'cross 50 NM northwest of APA at 15;000.' I read back the clearance and continued the descent. As we were completing the descent nearing Denver Approach's airspace we realized that we were descending to 15;000 and Longs Peak was straight ahead of us approximately 20 NM. Our local knowledge of the mountains we knew this mountain to be over 14;000 FT tall. The Captain leveled off our descent at 16;000 FT MSL. The Captain asked me to confirm our altitude with ATC. We made an attempt to confirm but due to frequency congestion we received no response. A few transmissions later by ATC we were told to climb and maintain 17;000. We complied and had already started a slow climb. During this entire event we had terrain in sight and no immediate action was required to avoid the terrain. Upon landing the Captain called Denver Center and spoke with the Center and he advised us that the Controller cleared the aircraft to 'cross 50 NM northwest of APA at 17;000.' I read back the 'cross 50 northwest at 15;000.' However the Controller did not catch our incorrect read back of the altitude assignment.It would seem the Captain's attention to local flight patterns caught the problem before ATC notified us. Secondly; if we were able to confirm our altitude clearance as we had tried before the deviation we could have leveled off at the correct altitude. The frequency congestion delayed our ability to clarify the clearance with ATC.

Data retrieved from NASA's ASRS site as of July 2013 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.

Attributes
ACN	1037202
Time
Date	201209
Local Time Of Day	1801-2400
Place
Locale Reference	APA.Airport
State Reference	CO
Environment
Flight Conditions	VMC
Light	Dusk
Aircraft 1
Make Model Name	Light Transport Low Wing 2 Turbojet Eng
Operating Under FAR Part	Part 135
Flight Phase	Descent
Flight Plan	IFR
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Last 90 Days 50 Flight Crew Total 5000 Flight Crew Type 40
Events
Anomaly	ATC Issue All Types Deviation - Altitude Overshoot Deviation - Procedural Published Material / Policy Inflight Event / Encounter CFTT / CFIT

A pilot read back a clearance to cross 50 northwest of apa at 15;000 ft but the the crew leveled at 16;000 ft because of high terrain knowledge and was then notified by ATC that the descent clearance was to 17;000 ft.