Why don't jets have alternators?

Cloud Surfer

Cloud Surfer

All Roads lead to Trantor
Any reason why this is? Everything turbine that I have ever flown has had generators and not alternators unlike small propeller-driven piston airplanes. The reason that I ask is that this could be a question in an upcoming interview. Thanks in advance!
 
In the CJ4, The generators are primary except for the windshield heat . Windshield heat power is provided by alternators which also act as backup should the gens go offline.
 
The Citation 3 (CE-650) has both also.


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Apparently this topic is broader and obviously more complex than I had anticipated! :biggrin:
Once more I am humbled in my quest of understanding aircraft systems.
 
Come to that, the Caravan has a backup alternator too. But I always figured most twins just had the start/gen as the second engine provides the redundancy.
 
But in all those cases of having an alternator, it seems it is meant to act as a backup. Perhaps in addition to having the advantage of being combined into a starter/gen unit, the high RPMs at which turboprop/jets operate makes generators more efficient as a primary source?

Also, I'm not too familiar with what airline turboprops/jets/fans possess, so I'm glossing over them it until some of our airline members would like to add something in regards, although I do recall that the CRJ uses generator units and APUs for electrical production and respectively starting.

BTW can a turbine starter motor be combined with an alternator?
 
Typically once you get into airline stuff you start running into AC gens and RATs and CSDs and VSCF and nonsense like that.
 
amprecon said:
Dassault Falcon 2000's have PMA's (Permanent Magnet Alternators), ask me how I know......
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Which is pretty much the definition of a generator.

Roger Roger said:
Typically once you get into airline stuff you start running into AC gens and RATs and CSDs and VSCF and nonsense like that.
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Well technically there's no such thing as a DC gen(or alternator). Unless you count a battery, or an AC Gen with a commutator or rectifier. Since it's impossible to spin something and have anything but AC as a result. Well.. within the confines of things used in automotive and aircraft.
 
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Lear 45 has a starter/gen on each side. It also has an alternator each engine. The only thing the alt's power is windshield heat. That's it. Can't use them for any thing else.
 
z987k said:
Which is pretty much the definition of a generator.


Well technically there's no such thing as a DC gen(or alternator). Unless you count a battery, or an AC Gen with a commutator or rectifier. Since it's impossible to spin something and have anything but AC as a result. Well.. within the confines of things used in automotive and aircraft.
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Ummm... A gen puts out DC without any rectification. And since no alternator I've ever dealt with doesn't have an internal rectifier, for all intents and purposes an alternator spits out DC. It's semantics.
 
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