<< >> NASA ASRS Report 1488926, October 2017

A pilot and center controller reported a communication problem with an altitude clearance and descended below the minimum IFR altitude.

Attributes
ACN	1488926
Time
Date	201710
Local Time Of Day	1801-2400
Place
Locale Reference	JAC.Airport
State Reference	WY
Aircraft 1
Make Model Name	Light Transport
Operating Under FAR Part	Part 135
Flight Phase	Descent
Route In Use	Direct
Flight Plan	IFR
Person 1
Function	Enroute
Qualification	Air Traffic Control Developmental
Person 2
Function	Single Pilot Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 50 Flight Crew Total 32000 Flight Crew Type 250
Events
Anomaly	ATC Issue All Types Inflight Event / Encounter CFTT / CFIT

Narrative:

I was the radar controller of the combined sectors. Aircraft X was on a heading at 16;000 feet. I issued a descent to 14;000 feet; the minimum IFR altitude (mia) in his area at the time was 13;700 feet. I thought the read back was correct; however after listening to it; it was very unclear. I noticed the pilot start to descend through 14;000 feet; to 13;700 feet where I asked; 'say altitude'. The pilot came back saying his altitude was 13;500 feet at the time; and descending to 11;000 feet. I issued a low altitude alert and a climb above the mia.I recommend new radios; or a new radio system.

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Original NASA ASRS Text

Title: A pilot and Center Controller reported a communication problem with an altitude clearance and descended below the minimum IFR altitude.

Narrative: I was the Radar Controller of the combined sectors. Aircraft X was on a heading at 16;000 feet. I issued a descent to 14;000 feet; the Minimum IFR Altitude (MIA) in his area at the time was 13;700 feet. I thought the read back was correct; however after listening to it; it was very unclear. I noticed the pilot start to descend through 14;000 feet; to 13;700 feet where I asked; 'say altitude'. The pilot came back saying his altitude was 13;500 feet at the time; and descending to 11;000 feet. I issued a low altitude alert and a climb above the MIA.I recommend new radios; or a new radio system.

Data retrieved from NASA's ASRS site 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.