Technical Bulletin

2008 – Headset Battery Replacement

The batteries used in Micro System headsets must be replaced with the appropriate headband battery assembly.

Updated 30-09-08

Replacement Headset Batteries:

Micro System headsets are fitted with a rechargeable battery pack which forms part of the headset headband. The headband battery assembly is available as a spare part or can be replaced by the service and repair facility at Lynx Avionics.

Equipment Affected:

Micro System Headset

Improper Battery Replacement:

There has been some recent discussion on internet newsgroups concerning the replacement of the Micro System headband battery pack with individual rechargeable batteries (AA or AAA cells) fitted inside the headset ear-cups. Lynx Avionics has also received enquiries from customers asking for support in making this modification.

Health and Safety Implications:

Cylindrical AA or AAA rechargeable battery cells contain pressure during use which may be released under certain circumstances; in particular, cells which are subject to a short circuit or which are charged when faulty can burst open producing an explosive release of hot gas.

The headset ear-cups are designed to seal around the ears in order to attenuate background noise. Whilst the headset design incorporates vents which allow the air pressure in the ear-seals and the ear-cups to equalise with external pressure, this system is only designed to cope with the slow pressure changes encountered under normal flying conditions. Any sudden increase of pressure inside the headset ear-cup will apply pressure directly to the ear drum (Tympanic Membrane) which is likely to rupture. In addition, the high temperature gas is likely to cause additional serious tissue damage as it escapes into and through the ear canal. The risk that this problem could occur to a pilot during flight is unacceptable.

Attempts to modify Micro System headsets by untrained or unskilled personnel will only increase the likelihood of a such an occurrence.


Rechargeable batteries must not be fitted inside the ear-cups of Micro System headsets under any circumstances.

Additional Information:

Customers who have headsets with suspected battery faults should return the headsets to the service and repair facility at Lynx Avionics for testing.

Additional information or technical advice may be obtained directly from Lynx Avionics Ltd.