Ground School Exam Questions & Question Banks
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I'll try! I have to say electrics is a pretty slippery subject.
Isn't it simply that with a generator, the more current you pass through the field coil, the more voltage is generated by the armature. Therefore, as you switch appliances on in series, then there will be a greater resistance, but also current load is being drawn into the circuit, into the field coils and thust self exciting the series wound system to match the current demands; the armature responds to the increased current in the field coil and produces more voltage. Therefore I and R will increase hence the reason why V increases in accordance with the Ohms law you referenced (V=IR).
Do you mean a compound generator. A mixture of fat series wound coils and thin shunt coils to provide a means to produce a constant voltage regardless of the load (to a degree I imagine).
can you tell me then how it happens or what happens or what it means when MORE CURRENT IS DRAWN?
So why not simply make the field coils less tight in order to even out the problem and not loose magnetic field strength?
More bang for your buck
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the field coils are in series with the loads (i.e the appliances) but they are not in series they are in parallel so the overall resistance decreases each time u switch some thing on (least i think that is what it means
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Hi GG and HWD
Thanks a lot for helping me on this. What I ment in the last paragraph is this. For a shunt generator, so with the field coil in parallel with the loads, when more systems are switched on, the resistance drops throughout the circuit. As a result, the current from what I understand, as other paths it can travel which offer less resistance than the tightly wound field coil. This means that the strength of the magnetic field created by the field coil drops and therefore the current or voltage induced in the armature is lessened. ( its voltage or emf, until something draws it in which case it becomes cureent is that right?) This seems to be a problem, hence why they make compound generators, but why simply not make the resistance of a parallel field coil LESS, and with that you would not get the voltage loss..............or is it that the whole purpose of the high resistance field coil ( many/thin, tightly wound) is to even out any fluctuations in the output from the armature, thereby making it a more constant and stable voltage output system?
Anyhow, I really appreciate you taking the time, as you said HWD, this is a slippery subject, and bar the little bit of electrics I did for PPL, this is all new and very hard to grasp, I turn each new page on the subject with dread!!! ...and I still have AC current and generators to get through, so I best have the basics straight before I move on.
Thanks
Thanks a lot for helping me on this. What I ment in the last paragraph is this. For a shunt generator, so with the field coil in parallel with the loads, when more systems are switched on, the resistance drops throughout the circuit. As a result, the current from what I understand, as other paths it can travel which offer less resistance than the tightly wound field coil. This means that the strength of the magnetic field created by the field coil drops and therefore the current or voltage induced in the armature is lessened. ( its voltage or emf, until something draws it in which case it becomes cureent is that right?) This seems to be a problem, hence why they make compound generators, but why simply not make the resistance of a parallel field coil LESS, and with that you would not get the voltage loss..............or is it that the whole purpose of the high resistance field coil ( many/thin, tightly wound) is to even out any fluctuations in the output from the armature, thereby making it a more constant and stable voltage output system?
Anyhow, I really appreciate you taking the time, as you said HWD, this is a slippery subject, and bar the little bit of electrics I did for PPL, this is all new and very hard to grasp, I turn each new page on the subject with dread!!! ...and I still have AC current and generators to get through, so I best have the basics straight before I move on.
Thanks
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Powdermonkey,
Argghh, my noggin hurts! And I'm winging it by joining the dots here! I think the point is that the wire needs to be thin to maintain the voltage but reduce the current to prevent the 'overspeed' problem of the fat series wound. But as you say the resistance is higher, so it is placed in parallel.
Resistance for parallel resistors is
1/rtot = 1/r1+ 1/r2 + 1/r3 etc.
So the total resistance is always less than any single resistor.
This maybe a question for the Tech Log forum?
Argghh, my noggin hurts! And I'm winging it by joining the dots here! I think the point is that the wire needs to be thin to maintain the voltage but reduce the current to prevent the 'overspeed' problem of the fat series wound. But as you say the resistance is higher, so it is placed in parallel.
Resistance for parallel resistors is
1/rtot = 1/r1+ 1/r2 + 1/r3 etc.
So the total resistance is always less than any single resistor.
This maybe a question for the Tech Log forum?
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Hi HWD & GG
You guys are up early for a Sunday morning, this is truly above and beyond the call of duty, thank you.
HWD, does your nogging hurt due to a good night last night?........If not, then I'm not surprised if you are answering questions like this at this time of the morning!!
Anyway, I think I have got it. I am fallling into the same trap as during my first module and trying to understand everything in depth, which makes for a very slow and painfull study day.
I'll type up my notes on what I 've got so far and MOVE ON to AC generators. I think I 'm in for a fun Sunday!
Thanks for the link Green Granite, I think I understand. Best to go and answer some questions on the subject to make sure I've got it........although I'd rather go for a quick spin above...weather's not bad today...nice and calm, good vis....hmmmmmmmm, shame not to take the oppurtunity
Thanks again, hope you guys get to go flying or do something more enjoyable than answering these sort of questions!!
You guys are up early for a Sunday morning, this is truly above and beyond the call of duty, thank you.
HWD, does your nogging hurt due to a good night last night?........If not, then I'm not surprised if you are answering questions like this at this time of the morning!!
Anyway, I think I have got it. I am fallling into the same trap as during my first module and trying to understand everything in depth, which makes for a very slow and painfull study day.
I'll type up my notes on what I 've got so far and MOVE ON to AC generators. I think I 'm in for a fun Sunday!
Thanks for the link Green Granite, I think I understand. Best to go and answer some questions on the subject to make sure I've got it........although I'd rather go for a quick spin above...weather's not bad today...nice and calm, good vis....hmmmmmmmm, shame not to take the oppurtunity
Thanks again, hope you guys get to go flying or do something more enjoyable than answering these sort of questions!!
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The EMF or PD in a circuit can be considered to be the electrical pressure that is available to make the current flow. It is measured in Volts. The current in a circuit is the flow of electrons. It is a measure of how many electrons pass a given point per second. Current is measured in Amps.
Electrical power (in Watts) in a DC system is equal to the EMF (in volts) multiplied by the current (in Amps). For any given combination of RPM and field strength a generator will produce a certain amount of power. In theory this could be in the form of a large number of volts multiplied by a small number of amps, a small number of volts multiplied by a large number of amps, or any other combination of volts and amps, provided the product of the multiplication is the same for each combination.
If we connect lots of loads in series then the resistance of the circuit will increase. This will decrease the current. But if the generator RPM and field strength are unchanged then the power output will be the same, so the voltage must increase. We do not really want this because the loads will have been designed to operate most efficiently at a fixed voltage. We would also have a problem in that switching off one load would switch off all of the other loads that are in series with it. So we do not usually connect loads in series.
If however we connect lots of loads in parallel each additional load will decrease the circuit resistance and increase the current. If generator RPM and field strength are unchanged then the power output will be unchanged. So the increase in current will cause the voltage to decrease. Once again this is unsatisfactory because the loads require a constant voltage.
What we really need is a generator in which field strength increases as we apply more loads in parallel. This will gradually increase the power output so that as more loads are added in parallel, the voltage remains constant but the current increases. Each load will then receive a constant voltage and current, provided we do not demand more than the generator can provide.
For any given number of turns in the generator field coil, the field strength depends upon the current going through it. So as we add more loads in parallel we need to increase the current through the field coil, so that the power output gradually increases to meet the increasing demand. This increasing power output will enable the generator to maintain constant voltage while gradually increasing the current to feed each additional load that is switched on.
SERIES WOUND GENERATORS
In a series wound generator the field coil is in series with the armature so the entire generator output goes through the field coil. This means that if the current in the circuit increases then the field strength will also increase. The loads are in series with the field coil but in parallel with each other. So switching on more loads will reduce the overall circuit resistance and increase the current in the circuit.
This sounds OK, but it makes it impossible for us to have direct control of the field current. If for example the RPM increases (because we open the throttle to take-off) the field strength and the voltage and current in the circuit will all increase. In extreme cases this will damage the loads or circuit wiring.
PARALLEL WOUND GENERATORS
In a parallel wound generator the armature, the field coil and the loads are all in parallel with each other. Once again this means that switching on more loads reduces circuit resistance and increases circuit current. But because the field coil is in parallel with the armature only part of the generator output goes through the field coil. And because the field coil is in parallel with the loads we can have direct control of the field current. We do this be adding a variable resistor in series with the field coil. This variable resistor is controlled by the voltage regulator.
If RPM increases the generator voltage will start to increase. The voltage regulator will sense this increase and will respond by increasing the resistance of the variable resistor. This will decrease the current through the field coil, which will reduce the field strength so that the voltage remains constant.
If more loads are added in parallel, this will decrease the circuit resistance and increase the current. With no initial change in power output, the voltage in the circuit will decrease. The voltage regulator will sense this decrease and will respond by decreasing the resistance of the variable resistor. This will increase the current through the field coil, thereby increasing field strength and power output. This increased power output will allow the generator to supply the increased current to feed the added loads while maintaining constant voltage.
Electrical power (in Watts) in a DC system is equal to the EMF (in volts) multiplied by the current (in Amps). For any given combination of RPM and field strength a generator will produce a certain amount of power. In theory this could be in the form of a large number of volts multiplied by a small number of amps, a small number of volts multiplied by a large number of amps, or any other combination of volts and amps, provided the product of the multiplication is the same for each combination.
If we connect lots of loads in series then the resistance of the circuit will increase. This will decrease the current. But if the generator RPM and field strength are unchanged then the power output will be the same, so the voltage must increase. We do not really want this because the loads will have been designed to operate most efficiently at a fixed voltage. We would also have a problem in that switching off one load would switch off all of the other loads that are in series with it. So we do not usually connect loads in series.
If however we connect lots of loads in parallel each additional load will decrease the circuit resistance and increase the current. If generator RPM and field strength are unchanged then the power output will be unchanged. So the increase in current will cause the voltage to decrease. Once again this is unsatisfactory because the loads require a constant voltage.
What we really need is a generator in which field strength increases as we apply more loads in parallel. This will gradually increase the power output so that as more loads are added in parallel, the voltage remains constant but the current increases. Each load will then receive a constant voltage and current, provided we do not demand more than the generator can provide.
For any given number of turns in the generator field coil, the field strength depends upon the current going through it. So as we add more loads in parallel we need to increase the current through the field coil, so that the power output gradually increases to meet the increasing demand. This increasing power output will enable the generator to maintain constant voltage while gradually increasing the current to feed each additional load that is switched on.
SERIES WOUND GENERATORS
In a series wound generator the field coil is in series with the armature so the entire generator output goes through the field coil. This means that if the current in the circuit increases then the field strength will also increase. The loads are in series with the field coil but in parallel with each other. So switching on more loads will reduce the overall circuit resistance and increase the current in the circuit.
This sounds OK, but it makes it impossible for us to have direct control of the field current. If for example the RPM increases (because we open the throttle to take-off) the field strength and the voltage and current in the circuit will all increase. In extreme cases this will damage the loads or circuit wiring.
PARALLEL WOUND GENERATORS
In a parallel wound generator the armature, the field coil and the loads are all in parallel with each other. Once again this means that switching on more loads reduces circuit resistance and increases circuit current. But because the field coil is in parallel with the armature only part of the generator output goes through the field coil. And because the field coil is in parallel with the loads we can have direct control of the field current. We do this be adding a variable resistor in series with the field coil. This variable resistor is controlled by the voltage regulator.
If RPM increases the generator voltage will start to increase. The voltage regulator will sense this increase and will respond by increasing the resistance of the variable resistor. This will decrease the current through the field coil, which will reduce the field strength so that the voltage remains constant.
If more loads are added in parallel, this will decrease the circuit resistance and increase the current. With no initial change in power output, the voltage in the circuit will decrease. The voltage regulator will sense this decrease and will respond by decreasing the resistance of the variable resistor. This will increase the current through the field coil, thereby increasing field strength and power output. This increased power output will allow the generator to supply the increased current to feed the added loads while maintaining constant voltage.
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BRILLIANT Keith, thanks a lot, I didn't understand initially the Power part of the generator, ie P = A x V. I was missing that part so things were a little confusing. This explains a lot, so thank you very much. AGK notes are terrible and skip a lot of the bits in between, so I was filling in myself, and not doing a good job of it.
Well, back to it
Well, back to it
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You guys are up early for a Sunday morning, this is truly above and beyond the call of duty, thank you.
HWD, does your nogging hurt due to a good night last night?
HWD, does your nogging hurt due to a good night last night?
As it happened the Seneca is U/S and I ran out of time for a bimble at Popham. What a glorious day for it all to go so horribly wrong 
Last edited by High Wing Drifter; 4th Dec 2005 at 20:32.
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HWD,
Simple series wound brain?? At least you have power going to yours! Shame you missed yout flight. It started to rain 5mins after I put up my post this morning....so much for my forecasting ability. In my defence, the big dirty grey cloud was on the other side of the house, sun was shining on my side of things.
Flight planning ALWAYS begins with PPrune!! In fact, study day begins with PPrune, so does working day and any other day that you don't wish to start just immediately!
Well I start new job humping luggage tomorow at EIDW to pay the bills until next April when these b**** exams will be finished!
So I had best get some kip!
Thanks again everybody
Simple series wound brain?? At least you have power going to yours! Shame you missed yout flight. It started to rain 5mins after I put up my post this morning....so much for my forecasting ability. In my defence, the big dirty grey cloud was on the other side of the house, sun was shining on my side of things.
Flight planning ALWAYS begins with PPrune!! In fact, study day begins with PPrune, so does working day and any other day that you don't wish to start just immediately!
Well I start new job humping luggage tomorow at EIDW to pay the bills until next April when these b**** exams will be finished!
So I had best get some kip!
Thanks again everybody
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Engine Failure question
The effects of an engine failure in a MEP are well understood, but I am struggling to get a decent answer for a jet.
Suppose B737 in cruise without A/P A/T engage loses the right engine is the sequence:
Pitch down then roll / yaw right
or
Yaw / Roll right andthen pitch down.
I seem to recall the first event is a pitch down motion.
Some help would be reet grand.
Thanks
woof
Suppose B737 in cruise without A/P A/T engage loses the right engine is the sequence:
Pitch down then roll / yaw right
or
Yaw / Roll right andthen pitch down.
I seem to recall the first event is a pitch down motion.
Some help would be reet grand.
Thanks
woof
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During cruise the power setting will be low so the pitch/power couple will be less pronounced. The first indication of engine failure will be the yaw to the right accompanied with roll. The secondary effect of this will be nose down pitch.
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hand solo
I'm actually doing engine failures every day at the moment finishing off my 737-800 type rating. The key to remember is just look at the yaw indication on the pfd or the slip indicator on the 200, If yawing to the right means right engine failure so turn the ailerons to the good engine IE ( the left ) one in this case to prevent roll and then step on the good engine rudder peddle to lift the control column back to neutral. If done like this smoothly and quickly enough once trimmed out on the rudder you hardly even notice you have lost an engine.. flighttime.
I'm actually doing engine failures every day at the moment finishing off my 737-800 type rating. The key to remember is just look at the yaw indication on the pfd or the slip indicator on the 200, If yawing to the right means right engine failure so turn the ailerons to the good engine IE ( the left ) one in this case to prevent roll and then step on the good engine rudder peddle to lift the control column back to neutral. If done like this smoothly and quickly enough once trimmed out on the rudder you hardly even notice you have lost an engine.. flighttime.
Props are for boats!
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Question Bank Perf A
Hi Guys,
Anyone have any training aids ie. CD ROM interactive disks or and internet access data on this subject. I have the CAP 385 extract and tables and a PPSC question and answer book. Just seeing if there is anything else out there free;y available. Where I work at the moment its hard to purchase avaition study material.
Any takes much appreciated
Sheep
Anyone have any training aids ie. CD ROM interactive disks or and internet access data on this subject. I have the CAP 385 extract and tables and a PPSC question and answer book. Just seeing if there is anything else out there free;y available. Where I work at the moment its hard to purchase avaition study material.
Any takes much appreciated
Sheep
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Why?
Are you upgrading your licence having not done Performance A under the old UK National system?
If so forget CAP385. My understanding is you now do the same Performance exam a everybody else doing ATPL(A). You need CAP 698. This is for three aircraft a Single Engine Piston, A Multi engine Piston and a Medium Range Jet Transport. Might find them similar to Beech Bonanza, Piper Seneca and B737-400.
That is the exam you'll be doing, not the old Performance A.
P.M if you need some help.
W1
Are you upgrading your licence having not done Performance A under the old UK National system?
If so forget CAP385. My understanding is you now do the same Performance exam a everybody else doing ATPL(A). You need CAP 698. This is for three aircraft a Single Engine Piston, A Multi engine Piston and a Medium Range Jet Transport. Might find them similar to Beech Bonanza, Piper Seneca and B737-400.
That is the exam you'll be doing, not the old Performance A.
P.M if you need some help.
W1
Props are for boats!
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Unfortunately the Country I am about to convert my licence to still uses this syllabus. I understand it is defunct, but does anyone have any left over material?
Sheep
Sheep
Props are for boats!
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Well no unfortunately in Singapore they still use CAP385, I Know its older and yes even the copy I have was 1st printed in 1976. I was just enquiring if anyone had any extra info out there?
Sheep
Sheep
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Bristol QBank and AGK
Hi all,
Doing AGK at end of month and am doing Bristol and Italian Qbanks.
Both are relatively low on questions compared to the Abacus Qbank.
Bristol for instance has only 760 questions available.
My question is, has anyone done ok on exams recently using Bristol...did you find it accurate and up to date for AGK?
Thanks for any feedback
PM
Doing AGK at end of month and am doing Bristol and Italian Qbanks.
Both are relatively low on questions compared to the Abacus Qbank.
Bristol for instance has only 760 questions available.
My question is, has anyone done ok on exams recently using Bristol...did you find it accurate and up to date for AGK?
Thanks for any feedback
PM
PPRuNe Supporter
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Re: Bristol QBank and AGK
I did AGK in December using BGS database as well as Bristol brush up, got 96%. Quite a few questions word for word. I found it a fairly good representation of an exam.
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Re: Bristol QBank and AGK
Took AGK as well, and am sure you will be ok with the Bristol online bank (try and score above 90% online before taking the exams). I have Gen Nav and Flight Planning next week, can anyone tell me if I would be ok with the bristol online (am scoring over 90%, bashing it at least 4 times a day). Thanks
Regards
DMan
Regards
DMan