[STEVE]

STEVE on November 19, 2018 at 8:11 am #18852

Hi Herman;
I’m not sure of the exact meaning of your question. Are you asking what the voltage values should be on the two posts of the alternator with the master switch on and the engine off??
If that’s the question, the voltage on the large terminal should be just slightly less than the voltage at the battery (+) terminal. This value will be from 11.5 to 12.4 volts.
The value on the small (field) terminal should be approximately 1 volt lower than the voltage on the large terminal.
That may not answer the question you asked.
If you’re asking what indication will a pilot see that tells him the alternator is working, the answer is the ammeter (which more correctly is a loadmeter) will tell you if the alternator is working.
Your ammeter is an instrument that tells the pilot how many amps, also called the electrical load the alternator is supplying to keep the electrical system voltage maintained at the desired value. You can see how this works by turning on a circuit that draws a large load (many amps) while watching the ammeter. The needle will show an increase in the load. When the alternator is operating, there will always be a displacement of the ammeter needle.
If the ammeter needle is at zero, this indicates the alternator is not working.
I hope this answers your question.
Happy Flying
Steve

[Herman Bongco]

Herman Bongco on November 18, 2018 at 2:51 pm #18851

The Piper PA-28 Cherokee is a light aircraft and classified for Personal use, Flight training and air taxi. The aircraft was first produced in 1960 and came just 5 years after the Cessna 172 (Another long running aircraft). The subject of this blog is the Piper Cherokee Service Manual.

https://www.mikeg.net/library/files/pa28-service.pdf

As a former Fighter Jet mechanic, ive always been quite intrigued on the servicing of various aircraft models and following all preventative maintenance services. See the attached piper manual below:

On page 69, is the starting point of Torque wrenches and Torque specifications. There are a handful of pages on Torque specifications. When I was in the military, I don’t recall having to torque so many bolts. Probably because parts would be swapped out so often. One of my favorite activities is cleaning the Engine. There is nothing better than having and maintaining a clean sparkling engine. Solvent and Degreaser is recommended. However, there is a CAUTION message about NOT spraying solvent on the alternator, starter, air intake and alternate air inlets. Most of the CAUTION warnings are common sense to me, but the warning below caught my attention:
Do not attempt any flight without an indication of Alternator output. The specification did not provide a required alternator reading. Does anybody know the required alternator reading on the PA-28? More details next time. Comments? Feedback?

Attachments:

• piper-sport-cruiser-model02.jpg