Posted: 5/7/2015 7:01:38 PM EDT
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serious question. does the turbine spin an alternator or generator of sorts? Posted Via AR15.Com Mobile |
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Everything you ever wanted to know on the subject.
https://www.youtube.com/user/AgentJayZ/videos |
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Not a 100% sure but I believe there are separate generators powered by hydraulics. At least I seem to remember something like that from hanging around the F-15 maintainers. It depends. (TM) At a basic level the N2 turns an accessory gearbox. Off of the gearbox hang a bunch of things like the starter (in bigger planes it's air powered), the hydraulic pump, and the generator. For redundancy my jet has three generators for the main buss when any one can handle the load. There's also a small generator that is run off the hydraulic system to provide emergency power to the co-pilot's instruments that's separate from the main AC buss. The real magic is how you keep a stead 400hz power output when the engine RPM is constantly changing. Lessor magic is getting all of those AC generators in phase. |
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Jet engine , Lycoming T53, as installed on a UH-1 Huey has a starter generator. On our Navy model Huey we have an alternator mounted on the transmission. There is an additional inverter to provide AC power. The Huey uses both Ac and DC. the Army versions had two generators and two inverters.
Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. The A-4 Skyhawk J-52 setup is similar to the F-4. |
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There no one answer as different engines across different applications do it differently.
Example: AH-64 Apaches have 2 generators mounted to the main gearbox (transmission) that is spun by one/both engines or the APU (smaller turbine used for engine starting). Boeing 787s have engine starter generators mounted to the APU and both engines. At first they act as an engine starter and then act as a generator after engine start. Eurocopter AS-350s (as well as similar single engined Eurocopter helos) employ a single starter generator mounted directly to the engine. There's no one answer and these are just a few ways turbines make electrical power at various levels. |
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Some exhaust heat is sometimes diverted to keep the wings deiced. Quoted:
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Yes, and supply heat. Knowledgeable people will post. Some exhaust heat is sometimes diverted to keep the wings deiced. It's not exhaust air, it's air bled off one or more stages of the compressor, before the combustion happens. It's damn warm air, even without the fire. On my ride, the generator is driven by an accessory gear box, via a constant speed drive. Think of it like an automatic transmission of sorts. Allows the generator to develop a constant power over a wide RPM range. Most large civil airplanes are mostly AC powered. 115V 400HZ. |
| The F/A-18's I used to work on had an AMAD, like a transmision, that the generators, hydraulic pumps etc mounted on and were turned all together by the turbine. You could de-couple them with a simple pull of a handle and then use just the APU/generator/hydraulics. The Gulfstream G650's I build now, use a 40kva generator on each engine and APU. It also has a 15kva RAT (Ram Air Turbine) that is deployed with the pull of a handle on the copilots side of the center pedestal. It hangs out in the wind like a dogs head out a car window and generates power from the air flowing over the fuselage. |
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Most comon engines have an accessory drive section. I spins along with the turbine, then branched off of the accessory drive section is auxilary power items, such as hydraulic motors, oil pumps, and electric generators. The generators are essentially standard magnetic based generators, that spin and create an electromagnetic field. the power is sent to the aircraft. Most engines have atleast one generator, so in the event of an engine fire you can choose to take power off of another unnaffected engine.
Source: im a C-5 Crew chief. |
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Quoted: Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. Why does the F-4 need 120 volts? Probably a stupid question. |
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Why does the F-4 need 120 volts? Probably a stupid question. Quoted:
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Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. Why does the F-4 need 120 volts? Probably a stupid question. The 120 V is AC and the 28 V is DC Aircraft Battery and emergency features are generally off 28vdc while the standard aircraft power is provided by the AC power. On C-5Ms it uses 115VAC |
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Quoted: The 120 V is AC and the 28 V is DC Aircraft Battery and emergency features are generally off 28vdc while the standard aircraft power is provided by the AC power. On C-5Ms it uses 115VAC Quoted: Quoted: Quoted: Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. Why does the F-4 need 120 volts? Probably a stupid question. The 120 V is AC and the 28 V is DC Aircraft Battery and emergency features are generally off 28vdc while the standard aircraft power is provided by the AC power. On C-5Ms it uses 115VAC I still have no clue. What is considered "standard aircraft power"? I assume the electronics and lights are operating on 28vdc but what is the 120 vac powering? |
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I still have no clue. What is considered "standard aircraft power"? I assume the electronics and lights are operating on 28vdc but what is the 120 vac powering? Quoted:
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Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. Why does the F-4 need 120 volts? Probably a stupid question. The 120 V is AC and the 28 V is DC Aircraft Battery and emergency features are generally off 28vdc while the standard aircraft power is provided by the AC power. On C-5Ms it uses 115VAC I still have no clue. What is considered "standard aircraft power"? I assume the electronics and lights are operating on 28vdc but what is the 120 vac powering? Standard aircraft power is Everything generally. So a mix of stuff you need and dont need. lighting, some instruments, some flight controls and stuff. Its harder to narrow down what is 115VAC, easier to say what is DC power. Emergency power would say for example worst case scenario you loose standard power for a moment, lets say a generator is being stupid. You would have 28volts DC operating emergency items, such as avionics, and engine fire T-handles. also emergency gear extension. Also aircraft batteries store DC power, so lets say the aircraft lost ALL POWER which would be totally a butt pucker situation, the battery on aircraft would be able to supply emergency power for a short period of time, id say about 20 minutes. Im not sure if that is too much technical lingo, i hope that explains it. |
| AC power goes to E-inverters and Transformer Rectifier Units that feed Power Distribution Boxes. These PDB's, have circuit breakers for both AC and DC. These main AC/DC feeders feed other circuit breaker panels in the aircraft that control things like Cabin Power, 60hz power (for outlets in the cabin), entertainment equipment Galley Power etc. |
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Also i know a few guys here are trying to learn about this, every aircraft is different.
So between aircraft and helicopter manufacturers they make stuff differently. Between Boing, Lockheed, Grumman etc. There is no standard, just what works. So alot of guys here are saying different stuff, and theyre all right, even though the information seems like it is conflicting. If that makes sense. |
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Standard aircraft power is Everything generally. So a mix of stuff you need and dont need. lighting, some instruments, some flight controls and stuff. Its harder to narrow down what is 115VAC, easier to say what is DC power. Emergency power would say for example worst case scenario you loose standard power for a moment, lets say a generator is being stupid. You would have 28volts DC operating emergency items, such as avionics, and engine fire T-handles. also emergency gear extension. Also aircraft batteries store DC power, so lets say the aircraft lost ALL POWER which would be totally a butt pucker situation, the battery on aircraft would be able to supply emergency power for a short period of time, id say about 20 minutes. Im not sure if that is too much technical lingo, i hope that explains it. Quoted:
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Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. Why does the F-4 need 120 volts? Probably a stupid question. The 120 V is AC and the 28 V is DC Aircraft Battery and emergency features are generally off 28vdc while the standard aircraft power is provided by the AC power. On C-5Ms it uses 115VAC I still have no clue. What is considered "standard aircraft power"? I assume the electronics and lights are operating on 28vdc but what is the 120 vac powering? Standard aircraft power is Everything generally. So a mix of stuff you need and dont need. lighting, some instruments, some flight controls and stuff. Its harder to narrow down what is 115VAC, easier to say what is DC power. Emergency power would say for example worst case scenario you loose standard power for a moment, lets say a generator is being stupid. You would have 28volts DC operating emergency items, such as avionics, and engine fire T-handles. also emergency gear extension. Also aircraft batteries store DC power, so lets say the aircraft lost ALL POWER which would be totally a butt pucker situation, the battery on aircraft would be able to supply emergency power for a short period of time, id say about 20 minutes. Im not sure if that is too much technical lingo, i hope that explains it. Emergency gear extension is done with pressure stored in an accumulator just for this purpose. It's often a manual valve that requires no power to actuate. The accumulator can be pressurized by running the APU or engines. On the F/A-18 we could manually pump the accumulator on the ground with a handle in the RH Main wheel well, like pumping a jack. |
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What is considered "standard aircraft power"? I assume the electronics and lights are operating on 28vdc but what is the 120 vac powering? There are different sensors and equipment that are ran off AC. Back-up and splitting systems is another way to allow for different sources of power, in case of a partial failure. 28vdc may be a standard for power, but you have inverters and converters changing that power into what is needed. It isn't like a car where everything is a single power type. |
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Quoted: Standard aircraft power is Everything generally. So a mix of stuff you need and dont need. lighting, some instruments, some flight controls and stuff. Its harder to narrow down what is 115VAC, easier to say what is DC power. Emergency power would say for example worst case scenario you loose standard power for a moment, lets say a generator is being stupid. You would have 28volts DC operating emergency items, such as avionics, and engine fire T-handles. also emergency gear extension. Also aircraft batteries store DC power, so lets say the aircraft lost ALL POWER which would be totally a butt pucker situation, the battery on aircraft would be able to supply emergency power for a short period of time, id say about 20 minutes. Im not sure if that is too much technical lingo, i hope that explains it. Quoted: Quoted: Quoted: Quoted: Quoted: Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. Why does the F-4 need 120 volts? Probably a stupid question. The 120 V is AC and the 28 V is DC Aircraft Battery and emergency features are generally off 28vdc while the standard aircraft power is provided by the AC power. On C-5Ms it uses 115VAC I still have no clue. What is considered "standard aircraft power"? I assume the electronics and lights are operating on 28vdc but what is the 120 vac powering? Standard aircraft power is Everything generally. So a mix of stuff you need and dont need. lighting, some instruments, some flight controls and stuff. Its harder to narrow down what is 115VAC, easier to say what is DC power. Emergency power would say for example worst case scenario you loose standard power for a moment, lets say a generator is being stupid. You would have 28volts DC operating emergency items, such as avionics, and engine fire T-handles. also emergency gear extension. Also aircraft batteries store DC power, so lets say the aircraft lost ALL POWER which would be totally a butt pucker situation, the battery on aircraft would be able to supply emergency power for a short period of time, id say about 20 minutes. Im not sure if that is too much technical lingo, i hope that explains it. Thanks, I think I got it now. I was looking at it completely backwards. I assumed that all aircraft systems would be low voltage (24-28). |
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Jet liners have something called an APU for power which I believe is like a mini jet engine. APU's are one source of power. They also supply pneumatic bleed air pressure to run things such as engine air starters or air-conditioning pacs when the aircraft is on the ground. |
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Quoted: There are different sensors and equipment that are ran off AC. Back-up and splitting systems is another way to allow for different sources of power, in case of a partial failure. 28vdc may be a standard for power, but you have inverters and converters changing that power into what is needed. It isn't like a car where everything is a single power type. Quoted: Quoted: What is considered "standard aircraft power"? I assume the electronics and lights are operating on 28vdc but what is the 120 vac powering? There are different sensors and equipment that are ran off AC. Back-up and splitting systems is another way to allow for different sources of power, in case of a partial failure. 28vdc may be a standard for power, but you have inverters and converters changing that power into what is needed. It isn't like a car where everything is a single power type. That is where my problem was, I just assumed aircraft were operating like cars. |
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A quick and dirty summary: Engine turns the PTO, PTO turns the AMAD, AMAD turns the CSD, CSD turns the generator. PMG sends voltage to the GCU, ,GCU sends PMG voltage to GEN Exciter Field (and regulates excitation to control generator voltage output), GCU monitors monitors generator for volts, freqs, phase, and for faults, if no faults exist GCU energized GLC (and/or BTC in the case of parallel buss operation) and bam, you have power on the buses. <Former Aircraft Electrical and Environmental Systems Instructor. |
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Why does the F-4 need 120 volts? Probably a stupid question. Quoted:
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Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. Why does the F-4 need 120 volts? Probably a stupid question. Radars use 400Hz 120v to power the transmitters, which on a Phantom were 1 million watt units. Takes a lot of current, but at 120 volts it takes a lot less current than at 400 Hz / 28 volts. |
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A quick and dirty summary: Engine turns the PTO, PTO turns the AMAD, AMAD turns the CSD, CSD turns the generator. PMG sends voltage to the GCU, ,GCU sends PMG voltage to GEN Exciter Field (and regulates excitation to control generator voltage output), GCU monitors monitors generator for volts, freqs, phase, and for faults, if no faults exist GCU energized GLC (and/or BTC in the case of parallel buss operation) and bam, you have power on the buses. <Former Aircraft Electrical and Environmental Systems Instructor. Pointy head. |
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Quoted: Radars use 400Hz 120v to power the transmitters, which on a Phantom were 1 million watt units. Takes a lot of current, but at 120 volts it takes a lot less current than at 400 Hz / 28 volts. Quoted: Quoted: Quoted: Our F-4 Phantom has a constant speed drive mounted on the front of the J79 engine with a 30 KVA generator mounted on the front. One of these on both engines. They are putting out 120 volt 400 cycle 3 phase. We have rectifiers to convert some of that to 28 VDC. Why does the F-4 need 120 volts? Probably a stupid question. Radars use 400Hz 120v to power the transmitters, which on a Phantom were 1 million watt units. Takes a lot of current, but at 120 volts it takes a lot less current than at 400 Hz / 28 volts. Damn, didn't think about the radar system. |
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Pointy head. Quoted:
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A quick and dirty summary: Engine turns the PTO, PTO turns the AMAD, AMAD turns the CSD, CSD turns the generator. PMG sends voltage to the GCU, ,GCU sends PMG voltage to GEN Exciter Field (and regulates excitation to control generator voltage output), GCU monitors monitors generator for volts, freqs, phase, and for faults, if no faults exist GCU energized GLC (and/or BTC in the case of parallel buss operation) and bam, you have power on the buses. <Former Aircraft Electrical and Environmental Systems Instructor. Pointy head. Incorrect. Pointy heads are avionics. I was a spark chaser. 
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