Generator too small to carry load

Generator too small to carry load

<HTML>It seems that my charging problems have been figured out with my generator.  The generator in my plane is evidently only a 20amp unit and it can't keep up with the load I am asking of it.

In looking back over the last year I have added a number of things to my plane which are drawing more energy:

1. I have installed Nu-Lite instrument lights on each intsrument.
2. I have the cigarette lighter hooked up so I can run my portable GPS.
3. I now fly wil my stobes and position lights on at all times.
4. I've added a new ICOM COM radio.
5. I've added a panel mounted intercom.
6. I've added a Davtron M800 clock.

The question at this point is do I installed a heaftier generator or do an alternator conversion.  I've read some past threads about this and it appears people are fairly split on what the do.

I am looking at the Skytronics installation of a JASCO alternator.  It almost seems that if I remove the generator and put in this alternator I can gain 20lbs back in usefull load.  That may not sound like much, but I routinely fly at gross weight.  Wish I could get an STC to reaise that a few hundred pounds smile

Any comments would be more than welcomed.</HTML>

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Re: Generator too small to carry load

<HTML>Dave:

Before you decide which method to use, you need to know exactly what your aircrafts current electrical loads are.  Your aircraft was type certificated and should have a electrical loads anaylsis for the equipment in your aircraft at time of production. 

Every time you or your mechanic add electrical equipment to your aircraft, a electrical load anaylsis is required to be performed per FAR 23.1351.  In addition, AC 43.13-2A, chapter 2, par 27d, states this requiement.  In order to know what generator or alternator to install, you need to know the current electrical load of your aircraft.

Sal</HTML>

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Re: Generator too small to carry load

<HTML>I had my mechanic check today, I have a 20amp Generator and I am pulling 21.5 amps......</HTML>

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Re: Generator too small to carry load

<HTML>Definitely time for a 60 amp alternator then.  It should pay for itself in about 10 years by saving you from replacing batteries alone.

Mark</HTML>

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Re: Generator too small to carry load

<HTML>Dave, my 2 cents on this. Last summer my 25 amp generator went kaput, had it rebuilt by auto shop, they turned it into a 35 amp generator when they replaced the interior windings. Re-installed by major shop in my area, they adjusted the same regulator, new main 35 amp fuse, all the wiring was large enough to handle another 10 amps, signed off by mechanic and it works fine. I looked at the alternator conversion, parts and labor and I was looking at well over a grand. And I wonder if you put in a 60 amp alternator are you going to end up replacing allot of wiring to handle that increase in power ? I dont know enough about electrical work to answer that. Tim Bailey</HTML>

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Re: Generator too small to carry load

<HTML>Dave,

You made an earlier posting regarding your battery not holding a charge.  If you're pulling more amps than your generator is putting out, your're simple draining your battery every time you fly.  The longer the flight the lower the battery is going to be.   Constant discharging and recharging can dramaticly decrease the life of a battery (deep cycle marine batteries are designed for discharging and recharging, starting batteries aren't).  The battery's main purpose is to start the engine.  This puts little drain on the battery.  The generator (or alt) will recharge it in short order and the generator should provide all necessary electricity to run your equipment.
It looks like your equipment might be killing your batteries and over stressing your generator....I'm guessing a higher output Gen/Alt would be in order...

Michael</HTML>

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Re: Generator too small to carry load

<HTML>Michael; your exactly right.  Thats also hat we figured killed my two year old battery....

Tim; I would really like to go the Alternator route but I am contemplating the cost.  The alternator conversion kit is $880, instalation will run about four hours @ $55 per hour for a total of $1100.  Looking at getting my generator up to 35 amps will cost around $700 in parts, for $180 more I can have the benefits of the alternator..  Tough call, not sure which way I am going to go.</HTML>

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Re: Generator too small to carry load

<HTML>Dave,
I went the Jayco alternator conversion route.  Worked out great.  Had an ammeter installed as well to replace the generator light.  Got my info from Stan Cooper, another member.  If he's listening, maybe he can chime in since his advise was right on.  Good luck.  Fred.</HTML>

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Re: Generator too small to carry load

<HTML>Dave,

  Spend the extra money for the ALT.  It's also safer, since you can control the field from the cockpit.  On the generator, if the 8 gauge wire from the gen to the bus bar frays and grounds to the frame, or a wire near the bus bar shorts it, there's nothing you can do with a generator.  With the alternator, you simply turn off the field.

  Plus if you idle for a while (like at San Jose waiting for a clearance), the generator won't be able to keep the battery charged for takeoff.  And with this constant variation in voltage, batteries won't last as long either.

  Another advantage is switching out the voltage regulator.  The Zeftronics models have built in overvoltage protection, and have a green/red diagnostic light on the regulator.  If you have an intermittent short or problem later, it's easier to diagnose.

  Generators on piston planes are antique technology. 

Sometimes original = bad.

Mark</HTML>

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Re: Generator too small to carry load

<HTML>Fred; did you mean Jayco or Jasco?  I could not find anything with Jayco.</HTML>

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Re: Generator too small to carry load

<HTML>Very good points by Sal, Fred and Mark.

I can't speak for anyone else, but I'd like to share my logic for spending the extra $$ to swap out the generator for the Jasco (Skytronics) alternator.

First off, AC 43.13-1B CHG 1, 11-35 (a) states:

"Output Rating.  The generator or alternator output ratings and limits prescribed by the manufacturer must be chacked against the electrical loads that can be imposed on the affected generator or alternator by installed equipment. When electrical load calculations show that the total continuous electrical load can exceed 80 percent output load limits of the generator or alternator, and where special placards or monitoring devices are not installed, the electrical load must be reduced or the generating capacity of the charging system must be increased. (This is strictly a 'rule of thumb' method and should not be confused with an electrical load analysis, which is a complete and accurate analysis of the composite aircraft power sources and all electrical loads).  When a storage battery is part of the electrical power system, the battery will be continuously charged in flight."

When I added up all of my loads, it looked like this:

PMA 6000 Audio Panel . . . . . . . . . . . . 1.00 Amperes
KLX 135A GPS/Com (Max current – transmit). . 6.30 Amperes
KY 97A Transceiver (Receive) . . . . . . . . 1.10 Amperes
AT50A Transponder. . . . . . . . . . . . . . 1.60 Amperes
ACK30 Encoder. . . . . . . . . . . . . . . . 0.30 Amperes
NAV 121 VOR Receiver . . . . . . . . . . . . 0.87 Amperes
ATD-200 Traffic Detector . . . . . . . . . . 0.20 Amperes
Horizon P-1000 Tachometer. . . . . . . . . . 0.20 Amperes
EI VA-1A-50 Volt/Ammeter . . . . . . . . . . 0.10 Amperes
Dome Light (GE 1816 Bulb). . . . . . . . . . 0.33 Amperes
Map Light (GE 58 Bulb) . . . . . . . . . . . 0.58 Amperes
Fuel Quantity Indicators (L and R Tanks) . . 0.36 Amperes
Instrument Lights (GE 94 Bulb) . . . . . . . 1.10 Amperes
Compass Light. . . . . . . . . . . . . . . . 0.08 Amperes
Landing Lights (Taxi and Landing). . . . . .15.60 Amperes
Strobe . . . . . . . . . . . . . . . . . . . 1.70 Amperes
Navigation Lights. . . . . . . . . . . . . . 5.60 Amperes
Stall Warning Horn . . . . . . . . . . . . . 0.25 Amperes
Turn & Bank Indicator (post inrush). . . . . 0.20 Amperes
Troll FN-200 Avionics Fan (post inrush). . . 1.00 Amperes

Total . . . . . . . . . . . . . . . . . . . 38.47 Amperes

80 percent of 50 Amperes (Jasco alternator capacity) is 40 Amperes, and 38.47 comes pretty close to that.  Granted, these aren't all "continuous loads", but it's conceivable that I'd want all of my lights, radios, etc., on at the same time at night.
Also, I might want to plug a GPS 295 into the cigar lighter, which would add to the load.  Anyway, the choice for me just in terms of load was pretty clear.

Finally, alternators provide a full charge at a much lower engine RPM than a DC generator.  The Jasco can provide full output at about 1200 RPM, while the DC generator needs to be at close to cruise speed to produce its rated output.

During a long, low power descent at night with landing lights, nav lights, instrument lights, etc., all on, with a generator you're discharging the battery.  With an alternator, you're still charging the battery.

For me, spending the extra bucks to upgrade to late 20th century technology was a no-brainer.  Others may have a different viwepoint, and I respect that.

My $.02

Stan</HTML>

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Re: Generator too small to carry load

<HTML>Michael, ...your words are good and (mostly) correct.  A battery's purpose is NOT for starting.  It's for storing an emergency supply of electricity in case of the complete failure of all generated electricity in flight.  That's why it's important to have 1) a healthy battery that's not too old and 2) a healthy electrical system to keep it charged.

Mark,...if you want to disconnect a misbehaving generator the method is readily available...Simply pull the fuse or Circuit breaker.

Stan,...It sounds like you're on the right track.  Did you include the power consumption of pitot heat? (if you have it.)  Generators are heavy, reliable, and not susceptible to transient voltage damage.  If your battery is discharged, a generator is capable of self-excitation and recharging it.  An alternator is lighter, produces power at lower engine speeds, is expensive to buy and repair and is more susceptible to damage and cannot self-excite to produce current if your battery is dead.  (You'll have to "jump" start or charge your battery first before the alternator will produce current,....a consideration if you're at some lonely deserted airfield when your battery dies.   Hint: Turn your strobes/beacon on and never turn them off.  It's pretty hard to walk away without noticing all that flashing activity when you leave your Master switch on.  "Hey, mister!  Your lights are flashing!"   "Yeah..I was just checkin' 'em to make sure they all work and wanted to view them from a distance." (grin))  Leaving them on, also gives everyone nearby a warning you're about to start up, when you first activate your Master switch.)</HTML>

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Re: Generator too small to carry load

<HTML>Great synopsis, George.

Nope, I don't have a heated pitot.  I DO keep my strobe switched on all the time for exactly the reason you point out.  It's hard to walk away from an airplane that's screaming at you, "Hey, Dummy, you left my Master Switch on"..  :-)</HTML>

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Re: Generator too small to carry load

<HTML>  If the 8 gauge wire from generator to the 60 amp breaker is directly shorted to the bus bar or the airframe, the breaker is not in the circuit.  Pulling it has no effect whatsoever.  If you have a generator, this means all of the amps the generator puts out will go through the short, and there is nothing in flight you can do about it (except stopping the engine).  It may create a nice fire.

  If you have an alternator, you break the field switch, and the alternator stops.

  Alternators cannot self-excite if the battery is dead.  If this is the case and you are at some deserted airfield, you can start your engine by hand propping.  This is illegal and dangerous.  Suggestions that you do this are unwise and illegal.  The aircraft was not designed for hand prop, and if you lose a hand, your insurance company will laugh at you, you'll pay the medical bill out of pocket, and you'll never play piano again.

  If you get a "jump" start, the starter will work either way, and indifferent to alternator or generator, the battery will charge in flight eventually if the amp draw is less than the amp generation.

"is expensive to buy and repair and is more susceptible to transient voltage damage"...hmmm...I don't know about this.  I can't speak on the expense vs. benefit, and I don't know anything about transient voltage damage.

  Ask how many people got an "alternator to generator conversion".  I think you will find the number is 0.  Does anyone know any modern airplane manufacturer who provides a generator with a new, non-turbine, aircraft? 

  Get an alternator...

Mark</HTML>

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Re: Generator too small to carry load

<HTML>Sorry Dave, I meant Jasco.  Fred</HTML>

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Re: Generator too small to carry load

<HTML>Leaving your strobes on all the time??  As a professional pilot I find strobes on during ground operations to be one of the most inconsiderate things a pilot can do.
Stobes are for in flight use only.</HTML>

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Re: Generator too small to carry load

<HTML>Hi Jon,

I guess I should have been a little more explicit.  The anticollision lighting on my airplane is a single red/white strobe on top of the vertical stabilizer which replaced the original rotating beacon.  That is the strobe I leave on all of the time.

I don't have wingtip strobes, but if I did, I wouldn't have turn them on during ground operations in consideration for other pilots.

That said, FAR 91.209(b) states that no person may operate an aircraft that is equipped with an anticollision light system, unless it has lighted anticollision lights unless the pilot-in-command determines that, because of operating conditions, it would be in the interest of safety to turn the lights off.

I believe several NTSB accident reports have suggested that having anticollision lights on during ground operations would probably have prevented taxiway collisions.</HTML>

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Re: Generator too small to carry load

<HTML>Stan, thanks for clearing that up.  Just one of my pet peaves to see wingtip strobes operating on the ground.  Anti-collision lights should definetly be on for all operations.</HTML>

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Re: Generator too small to carry load

<HTML>  I've found strobes on aircraft on the ground have sometimes looked in flight like REIL, and been confusing. 

  "I believe several NTSB accident reports have suggested that having anticollision lights on during ground operations would probably have prevented taxiway collisions."
  - unfortunately the NTSB hasn't considered how many runway overruns or landing accidents would have been prevented if ground aircraft had anticollision lights OFF during ground operations.
 
  "Anti-collision lights should definetly be on for all operations" 
  I personally turn off all anticollision lights while in clouds, and while stopped in the runup area.  I don't just find them distracting for other pilots, but these lights also distract me.  On the other hand, I work at an airport with few night taxi operations...</HTML>

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Re: Generator too small to carry load

<HTML>Hi Mark,

Dave Kalwishky started a new thread on this subject, and I posted paragraph 7 of AC 120-74, which addresses the use of exterior aircraft lights to make aircraft more conspicuous during taxi operations.</HTML>

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Re: Generator too small to carry load

<HTML>Mark..
You said "you can start your engine by hand propping. This is illegal and dangerous."

Do you mean it's against the law to hand prop?
Hand propping certinaly IS dangerous, and loosing merely a hand would be a minor mishap,considering there is sooooo much more you could loose.  I wouldn't recommend anyone handpropping anything without proper instruction and then only as an ablsolute last resort...but "illegal"?

Or did you mean one is not supposed to fly with a dead battery?

Michael</HTML>

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Re: Generator too small to carry load

<HTML>  Hand propping a plane which has an engine driven electrical system and was designed for starting by use of a starter is illegal.  You are not following the manufacturer's recommended procedures for starting if you hand prop such a plane.  Many manuals actually specifically say NOT to hand prop.

  Of course this may only be true here at the San Jose FSDO.  Our examiner here ran a taildragger flight school and specifically asked the FSDO about hand propping planes with the A65-12 engine.  This engine has an electric starter.  Both the FSDO and his commercial insurer told him he was out of luck if there was an incident and someone was hurt.  They told him this was not a recommended or approved procedure.  His name is Paul King, and he is the examiner here at WVI.  Call him if you'd like more info, he is very personable.

  Airplanes with electric starters were not designed or intended to be hand propped.  Planes which are designed for hand prop often have impulse couplings, retarded timing, and the nose is up in such a way that it is natural to pull down and step away.  Without these design improvements, I'm not comfortable doing this.

  I won't tell you not to do this.  It's up to you what happens in some back strip.

  If anyone has any contradictory info, I'd love to hear it.  I've never seen a plane manual for a Cessna which suggests hand propping as an alernative to electric start.  Granted, a guy like George with umpteen hand props can assuredly do such a thing with NO problems whatsoever, but a guy like me could get very hurt.

Mark
.02</HTML>

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Re: Generator too small to carry load

<HTML>The hand proping topic is interesting.  When I learned to fly, it was in an Aeronca Champ.  We HAD to prop it, no electrical system on board...  I guess I have never given much though that there are many many people that have not hand proped or have no desire too..  Interesting.....</HTML>

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Re: Generator too small to carry load

<HTML>Hand Proping - I might as well throw some chunks into this one.... What about the starter bendix that has it's gears meshed with the ring gear.. Fun to hand prop an 0-540 with that going on - plus 3 blade.  I think I will pass. Don't need to fly that bad - especially with a dead battery. I will fix the problem before I take it into the air. Just one of safety boundries.....I don't cross'em..  jack</HTML>

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Re: Generator too small to carry load

<HTML>Ok, I was referring to smaller planes, such as champs, cubs, luscombs and so forth.  I have proped my 172 once, that was enough...

Smaller planes/engines I do not mind.  Anything bigger than my 172 and no way...</HTML>

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