uwochris
Flightinfo's sexiest user
- Joined
- Dec 21, 2001
- Posts
- 381
Hey guys,
It is my understanding that the battery provides electrical power for starting and use of the equipment when the engines are not running. If the engines are running, then the alternator will carry all the load. In other words, the battery acts as a back-up in case of an alternator problem (except for starting).
Now some people (including a cfi) have told me that it is the opposite... the battery supplies all electrical power (even during normal flight), while the alternator is there simply to keep it charged. This does not seem consistent with what I have read in certain books and POHs, and I hope someone can clarify this issue. Also, seeing how the voltage of the battery is always a little less than the alternator would seem to disprove this theory. (?)
Another question... what is considered "acceptable" for the position of the needle on the ammeter? The C152 POH says 2 needle bar widths on the positive side- is this a "cessna thing," or does this rule apply to all a/c, including turbine powered a/c.
If my initial understanding is correct (i.e. the alternator supplies all electrical load once the engines are running, not the battery), it should make sense that the needle on the ammeter should be 0 (neither positive nor negative, since the battery does not need to be kept charged as the alternator is supplying all electical power). However, why then is it considered acceptable to see 2 needle bar widths on the plus side? I am guessing that anything above 2 needle widths is excessive and could cause damage due to high rates of charging, like overheating.
Thanks in advance for any comments,
Chris.
It is my understanding that the battery provides electrical power for starting and use of the equipment when the engines are not running. If the engines are running, then the alternator will carry all the load. In other words, the battery acts as a back-up in case of an alternator problem (except for starting).
Now some people (including a cfi) have told me that it is the opposite... the battery supplies all electrical power (even during normal flight), while the alternator is there simply to keep it charged. This does not seem consistent with what I have read in certain books and POHs, and I hope someone can clarify this issue. Also, seeing how the voltage of the battery is always a little less than the alternator would seem to disprove this theory. (?)
Another question... what is considered "acceptable" for the position of the needle on the ammeter? The C152 POH says 2 needle bar widths on the positive side- is this a "cessna thing," or does this rule apply to all a/c, including turbine powered a/c.
If my initial understanding is correct (i.e. the alternator supplies all electrical load once the engines are running, not the battery), it should make sense that the needle on the ammeter should be 0 (neither positive nor negative, since the battery does not need to be kept charged as the alternator is supplying all electical power). However, why then is it considered acceptable to see 2 needle bar widths on the plus side? I am guessing that anything above 2 needle widths is excessive and could cause damage due to high rates of charging, like overheating.
Thanks in advance for any comments,
Chris.