A C172 flight instructor reported loss of power when carburetor heat apparently was unable to cope w...

Narrative:

During a training flight; while in communication with [a military airfield]; I experienced a partial engine failure (power dropped from 2;000 RPM to 1;800 RPM upon application of full power). Attempts were made to apply carburetor heat; change tanks; and check magnetos with no change in engine status. I immediately diverted approximately 3 miles west to the nearest airport; which was [the military airfield]; declared an emergency so we could gain access to the military base; and landed without incident. Upon inspection it was determined the aircraft experienced carburetor ice apparently beyond the ability of the carburetor heat to eliminate. After paperwork at the facility to substantiate the need to land at the military base; a local aircraft mechanic inspected the aircraft and we decided to depart and return to our local mechanic. The flight continued without incident and inspections are being made to determine carburetor ice was the most likely reason for the engine anomaly before the aircraft is returned to the flight line at the flight school.

Original NASA ASRS Text

Title: A C172 Flight Instructor reported loss of power when carburetor heat apparently was unable to cope with the icing conditions. Aircraft diverted to a nearby military airfield.

Narrative: During a training flight; while in communication with [a military airfield]; I experienced a partial engine failure (power dropped from 2;000 RPM to 1;800 RPM upon application of full power). Attempts were made to apply carburetor heat; change tanks; and check magnetos with no change in engine status. I immediately diverted approximately 3 miles west to the nearest airport; which was [the military airfield]; declared an emergency so we could gain access to the military base; and landed without incident. Upon inspection it was determined the aircraft experienced carburetor ice apparently beyond the ability of the carburetor heat to eliminate. After paperwork at the facility to substantiate the need to land at the military base; a local Aircraft Mechanic inspected the aircraft and we decided to depart and return to our local Mechanic. The flight continued without incident and inspections are being made to determine carburetor ice was the most likely reason for the engine anomaly before the aircraft is returned to the flight line at the flight school.

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	1052291
Time
Date	201211
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Skyhawk 172/Cutlass 172
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Route In Use	Direct
Flight Plan	None
Component
Aircraft Component	Ice/Rain Protection System
Person 1
Function	Instructor Pilot Flying
Qualification	Flight Crew Commercial Flight Crew Flight Instructor Flight Crew Multiengine Flight Crew Instrument
Experience	Flight Crew Last 90 Days 94 Flight Crew Total 1430 Flight Crew Type 1073
Events
Anomaly	Aircraft Equipment Problem Critical

A C172 flight instructor reported loss of power when carburetor heat apparently was unable to cope with the icing conditions. Aircraft diverted to a nearby military airfield.