Im a training A&P ask away

originally posted by: CaptNemo2012

originally posted by: 5GenNext

originally posted by: EasyPleaseMe
a reply to: CaptNemo2012
Why are DC systems predominately 28V? I've never had a satisfactory answer to this question...

Aircraft batteries generally are 28v. So as a backup systems rely on 28v.

Yes this is my understanding as well. Most aircraft use 28 volt batteries. So naturally they will have a 28 volt system. Aircraft alternators and generators produce 400 hertz at 28 volts because of the extreme electrical loads that are running the craft.

Yes but batteries can be made to roughly any voltage. I'm pretty sure 28VDC was chosen before the batteries existed. The reason I ask is because the looms could be made lighter by using a higher DC voltage.

It might be like cars, where 12V was chosen at some point in time and standard components are made to operate at this voltage, even though it is horribly inefficient. But in most aircraft fewer standard components are used so there is opportunity for change.

Also, aren't generators 150VAC 400Hz?

a reply to: EasyPleaseMe

28v is about the charging voltage for a 12 cell lead-acid battery.

If you stuck with 12v, the cables and motor windings would be too big. 56v isn't intrinsically safe. So 28 is a decent compromise.

p.s. don't fall for the " can you go get me a bucket of prop wash!" or " I need 10 yards of flight line" tricks!!

Do me a favour and don't bend the pins, I hated bent pins, always the pins. Oh and if the 3rd fuel computer you try in the same position is U/S it's probably not the computer, stop sending them back for repair!

a reply to: Zaphod58

Whats your favourite colour, green or blue?

a reply to: CaptNemo2012

Congratualtions, I was 37 when I took up the trade here in Australia. Avionics is not dead. In fact if you look the mechanical and electrical streams are combining all around the world, just look at the latest generation of aircraft for proof. I'm happy to answer any questions you may have just as the other engineers on here are.

LEE.

a reply to: TheCrowMan

I have tried 3 EEC's in a row and in every case it turned out to be the EEC, not the harness or something else. Had it with EMCD's and a whole host of other things. Usually caused by your supply chain people not doing their job and reading the unserviceable label correctly and putting the part back in stock!

LEE.

originally posted by: EasyPleaseMe


Also, aren't generators 150VAC 400Hz?

You mean 115VAC 400Hz?
It also apparently makes the size of the generators smaller and lighter and therefore useable in an aerospace application.

a reply to: thebozeian

Power supply parts are a lot smaller too.

a reply to: Zaphod58

28mph assuming it's the european swallow.

lol

I'm in A&P school as well, just finished up basic electricity. Keep those grades up, are u taking your comp tests? There is an app you can download called "quizlet" and it has most of the questions for the FAA tests. Good luck bro

How come I can't get no Tang 'round here?

Been bashing tin for many years on old aircraft..Even when your having a crap day its still fun..