Air carrier VHF radio equipment problem.

Attributes
ACN	183497
Time
Date	199107
Day	Tue
Local Time Of Day	0601 To 1200
Place
Locale Reference	atc facility : hou
State Reference	TX
Altitude	msl bound lower : 19000 msl bound upper : 19000
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Controlling Facilities	artcc : zhu
Operator	common carrier : air carrier
Make Model Name	Medium Large Transport, Low Wing, 2 Turbojet Eng
Navigation In Use	Other Other
Flight Phase	cruise other
Flight Plan	IFR
Person 1
Affiliation	company : air carrier
Function	flight crew : captain oversight : pic
Qualification	pilot : atp
Experience	flight time last 90 days : 200 flight time total : 20000 flight time type : 1400
ASRS Report	183497
Events
Anomaly	aircraft equipment problem : less severe
Independent Detector	other flight crewa
Resolutory Action	none taken : unable
Consequence	Other
Supplementary
Primary Problem	Aircraft
Air Traffic Incident	other

Narrative:

The VHF radios on medium large transport operated by air carrier will emit a very loud squeal in the headset when the radios are tuned to certain frequencys. For example, when flying from btr to jan, houston center will assign a frequency of 126.0. When you tune the radio to that frequency, a very loud squeal will be heard in your headset except when you or another aircraft transmit on that frequency. The only way to eliminate the squeal is to ask for a different frequency (if one is available) or remove your headset and turn the volume very low which may result in a missed radio call. (The other alternative of leaving the volume up while subjecting your hearing to possible damage from the squeal.) the problem is caused by improper shielding of some electrical cables for the symbol generators. The pilots report these problems in the maintenance logbook, but company has not allocated the resources to correct the problem.

Original NASA ASRS Text

Title: ACR VHF RADIO EQUIP PROBLEM.

Narrative: THE VHF RADIOS ON MLG OPERATED BY ACR WILL EMIT A VERY LOUD SQUEAL IN THE HEADSET WHEN THE RADIOS ARE TUNED TO CERTAIN FREQS. FOR EXAMPLE, WHEN FLYING FROM BTR TO JAN, HOUSTON CENTER WILL ASSIGN A FREQ OF 126.0. WHEN YOU TUNE THE RADIO TO THAT FREQ, A VERY LOUD SQUEAL WILL BE HEARD IN YOUR HEADSET EXCEPT WHEN YOU OR ANOTHER ACFT XMIT ON THAT FREQ. THE ONLY WAY TO ELIMINATE THE SQUEAL IS TO ASK FOR A DIFFERENT FREQ (IF ONE IS AVAILABLE) OR REMOVE YOUR HEADSET AND TURN THE VOLUME VERY LOW WHICH MAY RESULT IN A MISSED RADIO CALL. (THE OTHER ALTERNATIVE OF LEAVING THE VOLUME UP WHILE SUBJECTING YOUR HEARING TO POSSIBLE DAMAGE FROM THE SQUEAL.) THE PROBLEM IS CAUSED BY IMPROPER SHIELDING OF SOME ELECTRICAL CABLES FOR THE SYMBOL GENERATORS. THE PLTS RPT THESE PROBLEMS IN THE MAINT LOGBOOK, BUT COMPANY HAS NOT ALLOCATED THE RESOURCES TO CORRECT THE PROBLEM.

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