Instructor pilot shuts off radios in traffic pattern to alleviate the problem of a stuck microphone.

Attributes
ACN	125645
Time
Date	198910
Day	Sun
Local Time Of Day	1201 To 1800
Place
Locale Reference	airport : mht
State Reference	NH
Altitude	agl bound lower : 0 agl bound upper : 1300
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	tower : mht
Operator	general aviation : instructional
Make Model Name	Small Aircraft, Low Wing, 1 Eng, Retractable Gear
Flight Phase	descent : approach landing other other
Route In Use	approach : visual
Flight Plan	None
Person 1
Affiliation	Other
Function	instruction : instructor oversight : pic
Qualification	pilot : cfi pilot : instrument pilot : commercial
Experience	flight time last 90 days : 50 flight time total : 5000
ASRS Report	125645
Person 2
Affiliation	Other
Function	flight crew : single pilot instruction : trainee
Qualification	pilot : student
Events
Anomaly	aircraft equipment problem : critical other anomaly other
Independent Detector	other flight crewa other other : unspecified atc
Resolutory Action	flight crew : regained aircraft control none taken : unable
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	Pilot Deviation other

Narrative:

We received clearance from mht tower and took off on a training flight. After approximately 1 hour we returned to mht airport. We contacted the tower with the ATIS information and received permission to enter a left downwind entry to runway 17. We then requested a left base entry, which was granted. We were asked to report a 2 mi left base. As we proceeded inbound, we noticed an aircraft passing in front of us. We attempted to contact the tower regarding this aircraft and in the meantime began to follow the aircraft, as it was obviously in the landing pattern. After several attempts to call the tower we concluded that our radio had failed. (We tried both radios and both microphone jacks.) we then shut off the radios as we were suspicious of a stuck microphone. (Just before this we heard the tower call us and requested us to identify if we could hear them, then we lost all contact.) we squawked 7600 and continued inbound. On final, we received a green light signal from the tower and landed. We talked to the tower by telephone later and explained the situation. They said that we had a stuck microphone on departure, yet they never mentioned this to us upon our initial calls when we returned for landing.

Original NASA ASRS Text

Title: INSTRUCTOR PLT SHUTS OFF RADIOS IN TRAFFIC PATTERN TO ALLEVIATE THE PROBLEM OF A STUCK MICROPHONE.

Narrative: WE RECEIVED CLRNC FROM MHT TWR AND TOOK OFF ON A TRAINING FLT. AFTER APPROX 1 HR WE RETURNED TO MHT ARPT. WE CONTACTED THE TWR WITH THE ATIS INFO AND RECEIVED PERMISSION TO ENTER A LEFT DOWNWIND ENTRY TO RWY 17. WE THEN REQUESTED A LEFT BASE ENTRY, WHICH WAS GRANTED. WE WERE ASKED TO REPORT A 2 MI LEFT BASE. AS WE PROCEEDED INBND, WE NOTICED AN ACFT PASSING IN FRONT OF US. WE ATTEMPTED TO CONTACT THE TWR REGARDING THIS ACFT AND IN THE MEANTIME BEGAN TO FOLLOW THE ACFT, AS IT WAS OBVIOUSLY IN THE LNDG PATTERN. AFTER SEVERAL ATTEMPTS TO CALL THE TWR WE CONCLUDED THAT OUR RADIO HAD FAILED. (WE TRIED BOTH RADIOS AND BOTH MICROPHONE JACKS.) WE THEN SHUT OFF THE RADIOS AS WE WERE SUSPICIOUS OF A STUCK MIC. (JUST BEFORE THIS WE HEARD THE TWR CALL US AND REQUESTED US TO IDENT IF WE COULD HEAR THEM, THEN WE LOST ALL CONTACT.) WE SQUAWKED 7600 AND CONTINUED INBND. ON FINAL, WE RECEIVED A GREEN LIGHT SIGNAL FROM THE TWR AND LANDED. WE TALKED TO THE TWR BY TELEPHONE LATER AND EXPLAINED THE SITUATION. THEY SAID THAT WE HAD A STUCK MIC ON DEP, YET THEY NEVER MENTIONED THIS TO US UPON OUR INITIAL CALLS WHEN WE RETURNED FOR LNDG.

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.