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Q & A: Replacing an old starter contractor, and proper antenna installation for a 406 MHz ELT

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Q: Hi Steve,

I think I should replace the starter contactor on my 1978 Cherokee Six 300. As far as I can tell, the contactor is working fine, but it looks like it’s almost 40 years old. I haven’t found an entry in the aircraft maintenance records that indicate it’s ever been changed. 

I am a firm believer in paying it forward on maintenance. I fly my Six into mountain strips all over the Western United States and would hate to have to figure out how to get my engine started if the contactor ever fails out in the bush.

What’s your opinion?

—Contactor Charlie


A: Dear Charlie,

I am in the same boat. As far as I can tell from logbook research and general appearance, the starter contactor on my Comanche is also the original unit. That makes it 55 years old. 

Like yours, mine also seems to be working fine. But as an A&P who has cut apart a few contactors to inspect the internal components, I know that arcing and time will reduce the current-carrying capacity. 

I know of two approaches to replacing an older contactor. 

Piper Service Letter (SL) 1093A, published on May 8, 2015, provides information on starter contactor replacement parts and installation procedures for Piper-supplied contactors. SL 1093A is applicable for PA-18 through PA-46 aircraft, supersedes SL 1093 and expands the serial numbers affected. (“Aircraft that have previously complied with SL 1093 are in compliance with SL 1093A,” according to the publication. —Ed.) Piper Engineering Order (EO) 88371, Revision E is part of  SL 1093A. 

These documents supply a list of replacement part numbers for starter contactors that are identical to the original configuration, and descriptions of (and differences between) the original and newer replacement contactors. In addition, they provide instructions on how to install the original grounded-case style of contactors and how to install the newer insulated-case style of contactors. 

Grounded-case contactors are easy to identify: there’s only one small lug and two large lugs. 

Insulated-case contactors have two small and two large lugs. In addition, insulated-case contactors have a black plastic insulator on each mounting tab. 

One thing that may confuse installers and owners is the fact that the contactor—part number 487-149—installed on my Comanche, and the contactor on your Cherokee Six—part number 487-169—are specified as six volt intermittent contactors. 

Since my Comanche and your Cherokee Six have 12 VDC electrical systems, this flummoxed me. I wrote to Piper, and within hours, Piper wrote back to say that six volt contactors are used in the starter circuit to insure that the contactor stays closed—thereby energizing the starter—even when battery voltage drops below the level where a 12 volt contactor would stay closed. 

The part number for new starter contactors from Piper for your Cherokee Six is 602-847 (99130-003). Internet prices range from $120 to $160; I did find one in original Piper packaging on eBay for $79.

Changing a grounded case contactor is a simple remove-and-replace job. 

Changing from a grounded case to an insulated case contactor requires the installation of a jumper wire from one of the small lugs to one of the mounting bolts or screws that secures the contactor to the firewall. The Piper part number of the jumper wire is 84580-044; cost is around $20.

The second approach you can take to replace your old contactor is a replacement solution from Sky-Tec in Granbury, Tex. 

Sky-Tec offers a complete line of 12 and 24 volt FAA-PMA approved original configuration grounded-case starter contactors. 

Replacement contactors for 12 volt systems—part number STS-S12—sell for $69, while 24 volt contactors—part number STS-S24—sell for $79. 

Sky-Tec contactors are sold by most aviation supply houses. The Instructions for Continued Airworthiness (ICA) for the Sky-Tec contactors require replacement after 30 years of service. 

Remember to always hold the nut nearest the body of each contactor with a wrench to prevent turning while applying torque to the terminal securing nuts.


Happy flying.

Q: Hi Steve,

I’m getting ready to install a 406 MHz ELT. I like the ELT 345 from Artex. (PFA supporter Emergency Beacon Corp. manufactures the EBC 406ap and EBC 406af for use in GA aircraft as well. —Ed.) 

One the guys at the airport is telling me that I have to keep my 121.5 MHz antenna from my existing ELT and install a new antenna that’s included with the Artex ELT. He says it’s because the 406 ELT sends out signals on both 121.5 MHz and 406 MHz. 

That doesn’t sound right. Will you check this for me?


—Antenna Art


A: Dear Art,

Your airport guy is wrong on this one; only one antenna is needed. 

During the installation of a 406 MHz ELT, most installers remove the 121.5 MHz antenna. After making sure the mounting location meets the installation requirements of the 406 MHz antenna (or after reinforcing it so it will comply), use the same hole to install the 406 MHz antenna. 

According to the data plate of the ACR Artex ELT 345, an activated unit will send out a five watt 406 MHz signal for 24 hours and a 100 milliwatt (mW) 121.5 MHz signal for 48 hours. The 121.5 signal is homed in on by low altitude search and rescue aircraft. The 100 mW signal is strong enough for close-by searchers to detect. 

This antenna, while not ideally tuned for the 121.5 MHz signal, is sufficient for the purpose intended. I installed a 406 MHz ELT in my Comanche and am glad I did. 


Happy flying.

 

Know your FAR/AIM and check with your mechanic before starting any work.

Steve Ells has been an A&P/IA for 43 years and is a commercial pilot with instrument and multi-engine ratings. Ells also loves utility and bush-style airplanes and operations. Ells is the owner of Ells Aviation (EllsAviation.com) and the proud owner of a 1960 Piper Comanche. He lives in Templeton, Calif. with his wife Audrey. Send questions and comments to


RESOURCES >>>>>

Piper Maintenance Alert Service Letter 1093A

PiperFlyer.org/SL1093A

 

FAA-PMA grounded-case starter contactors Sky-Tec Partners Ltd.

skytecair.com

 

Artex ELT 345 ACR Electronics, Inc.

acrartex.com


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