121.5 ELT batteries and replacing C-172 stall horn

2 Replies

121.5 ELT batteries and replacing C-172 stall horn

Posted by Roger Lucheta on Feb 28, 2019 6:54 am

I have two questions:
1) With respect to the recent FCC ruling banning repair, sale, and/or installation of 121.5 MHz ELTs, is the production and sale of replacement batteries still permitted?
2) I have determined that the stall horn, itself, in our Cessna 172N is defective.  How do you replace it?  It is in a blind box where you can barely touch it.  The tygon tubing is surely fused on, and I can see no way to get at it, other than having my IA cut a new inspection hole to get at it.
Thanks
  • Bookmark

Re: 121.5 ELT batteries and replacing C-172 stall horn

Posted by Ronald Levy on Feb 28, 2019 9:05 am

Regarding 121.5 ELt's, I think you are misinformed.  Use of existing installed 121.5 ELT's to meet the FAA ELT rule is not affected, nor is repair or supply of batteries.  See https://www.aopa.org/news-and-media/all-news/2018/december/18/new-1215-mhz-elts-to-be-prohibited for details.

As for replacing the stall warning device in your Cessna 172, this should be addressed in the maintenance manual for your aircraft, which your mechanic should have.  It's certainly not a preventive maintenance task you are allowed to do yourself without the supervision and approval of a licensed mechanic.  I suggest you discuss this with your mechanic.

Re: 121.5 ELT batteries and replacing C-172 stall horn

Posted by Christopher Gordon on Mar 4, 2019 1:11 pm

Regarding the stall horn, as Ron said the service manual for the 172N should provide the details you need to troubleshoot the stall warning horn, Google search should lead you to a PDF version you can use for reference.  The Illustrated Parts Catalog with part numbers is available for download at https://ww2.txtav.com/TechnicalPublications/ but as Ron said this repair should involve your A&P or at least their supervision.  If you have the pneumatic stall warning system on your 172N I believe the horn and reed should be accessible in the wing root by removing the plastic trim on the door post inside the cabin.