Generator too small to carry load

Re: Generator too small to carry load

<HTML>I'll throw my flag into this one too.

A while back we discovered that Cessna installs their propellers in such a way that hand proping is a little more dangerous.

Most hand prop to start aircraft have the propeller installed so that the magneto fires with the prop blade around the 10 O'clock position(looking towards the tail).  This allows the starter to keep his center of balance back as he pulls the prop through.

Your run of the mill Cessna has the propeller installed such that the mags fire around the 7 O'clock position.  This means the starter really needs to bend over almost into the prop disc to achieve enough movement to snap the prop through.

Anyone who doesn't have the patience at an FBO to get a jump probably isn't in the correct frame of mind to be flying in the first place.

I whole heartedly recommend people learn to properly hand start an aircraft. 
It's better than trying to figure it out in the middle of nowhere.

Cheers,
RH</HTML>

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Re: Generator too small to carry load

<HTML>Patience at the FBO may not be the issue, you might land somewhere and a small unattended airport, get out for a leg strech, climb back into the plane and discover that your weak generator did not keep your battery charged smile

That did happen, and I'm glad I had the skill to prop my plane.  I was no where near home, I had a cell phone and could have called for help but that would have been a huge hassle.  Now, if I were in a bonanza or 182 or something bigger than my 172 then I would have used the phone and called for help smile</HTML>

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Re: Generator too small to carry load

<HTML>Without taking a position on whether or not one should hand prop a Cessna, I think the reason this thread took a turn toward handpropping is that George rightly pointed out that a generator equipped airplane with a dead battery can be handpropped to get it started, and the generator will begin charging the battery. 

An alternator equipped airplane, on the other hand, requires an excitation voltage for the alternator to begin charging the battery, and with a dead battery there's no excitation voltage.  So, even though the engine can be handpropped, the electrical system remains dead as a doornail.  No lights, no radios.  The only way to start an alternator equipped airplane AND get the alternator to charge the battery is to jump start it so there's enough excitation voltage to get the alternator charging the battery.</HTML>

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Re: Generator too small to carry load

<HTML>Not sure I understand what "excitation voltage" is.  With a dead battery and my plane equiped with an alternator are you says that once I hand prop it and it's running, even at high RPM I still won't have any electrical system working?</HTML>

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Re: Generator too small to carry load

<HTML>Dave,

Yes.  That's exactly what I'm saying, and that was George's point in his reply to my long post explaining my rationale for putting in an alternator.  He was pointing out that if you have a dead battery with an alternator, you either have to charge your battery or get a jump start to provide excitation to the alternator field.  If you don't, no matter how high you rev your engine after hand propping it to get it started, the alternator won't put out any current.  The reason is that if there isn't enough battery power to energize the battery contactor, there won't be any current to the alternator field, and the alternator can't restart.  Alternator field windings only require an amp or two of current, but if the battery is so dead that the contactor doesn't pull in, the field windings never get power.

The key is not to let your battery go dead, therefore George's advice to keep your beacon on all the time so you don't forget to turn off the master switch.</HTML>

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Re: Generator too small to carry load

<HTML>Mark wrote: "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). "

You are incorrect Mark.  Pulling the CB or fuse on either an alternator OR a generator does exactly the same thing.  It disables the regulator circuit on either unit, and either unit immediately stops producing current.  The failure mode you imagined above would apply equally to BOTH types of generators.  (An alternator is more accurately called an "alternating current generator", we've just adopted the slang term "alternator" for convenience.  The alternating current is rectified by diodes into Direct current prior to it's introduction onto the aircraft electrical buss.  A short on that "8 gauge wire" at the location you imagine with EITHER unit would cause a reverse current from the battery to the gen or alt and would "pop" that breaker and shut down the gen/alt.

Mark wrote: "Hand propping a plane which has an engine driven electrical system and was designed for starting by use of a starter is illegal...."

and also: "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."

  Again, Mark, you are incorrect.  It is not "illegal" to hand prop an airplane.  Hand propping airplanes is a time-honored (if not forgotten) method of starting airplanes.  There is nothing inherently illegal about it.  There may be some local ordinance at your airport against it, but it's likely not enforceable, as too many airplanes can only be started by hand-propping BY DESIGN.  As for impulse couplings, retarded timing, etc. etc.......ALL ELECTRIC START airplanes are also so equipped.  Whether or not an airplane is equipped with a self-starter or not.....has nothing to do with it's method of retarding ignition during start.  Virtually all reciprocating engined airplanes have some method of retarding the ignition during start.  (Virtually, but not all.  In actual fact,  many of the earlier airplanes that were DESIGNED to be HAND PROPPED had NO impulse couplings...NO retarded timing...at all, Mark.  Many Cubs, Taylorcrafts, Aeroncas, etc. were economy aircraft with simpler magnetos that had no provision for retarded start.  It's exactly the OPPOSITE of what you say, Mark.)

(This is NOT intended to encourage those of you not familiar, comfortable, or not properly instructed in the correct method of hand-propping an airplane to try this.  If you're intimidated by it, that's good.  Leave it alone, and call for a mechanic or a ground start machine.   There's no such thing as being overly-cautious in this regard.  I just want to correct the information.)

Mark wrote:  "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,..."

  That simply is unworthy of belief.  The main difference between the Continental A-series engines and the C-series engine is that the A's (such as the A-65's) were SPECIFICALLY NOT equipped with starters.  In fact, they can't be retrofitted either.   And the FSDO has no jurisdiction over whether or not someone wishes to hand-prop an aircraft.   While operating a Part 91 aircraft with a failed starter MAY be considered operation with inoperable equipment, ....that would be determined by whether or not there was a MEL for the aircraft addressing the issue.  (In any case, there are thousands of aircraft flying that do not have starters in them and they are started and fly quite legally every day by hand-propping.)   In the example I used above, a discharged battery could be re-charged with a generator system by hand-propping while an alternator equipped airplane could not.  Once the battery was re-charged by the generator, there would no longer exist a failed system to prevent legally flying the aircraft.
  On the other hand, an alternator equipped airplane, being unable to re-charge it's battery WOULD be ILLEGAL to fly without a MEL providing for that type failure.

   It matters not to me whether someone wishes to convert their airplane or no.  Each system has it's own advantages as well as disadvantages and I hoped to shed a little light on the subject.  There's no reason to introduce a lot of unrelated and incorrect information on the subject to bring others to your viewpoint just to persuade them to make the same choice as you did.</HTML>

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Re: Generator too small to carry load

<HTML>Jack, you asked, "What about the starter bendix that has it's gears meshed with the ring gear." 
That bendix only appears to be engaged with the ring gear.  In fact, it is DIS-engaged until the starter motor's spinning action propels it forward to engage the gear.

Roger, ...the propeller installation should have the #1 blade installed at the 1-2 O'clock position as viewed from the pilot's seat, in accordance with the Service Manual.  (A 3-blade prop would have it at the 6 o'clock position.)  In all cases this  places one of the blades at the correct position for propping, (although that may not be the reason for it.  The reason for it being that position places the blade at optimum advantage with regard to relative wind for power produced by the firing cylinder.  Remember the P-factor discussion in ground-school?)

The most difficult hand-propping situation is one on a "shower of sparks" (Bendix) magneto system, because the ignition is not retarded without the ignition switch in the start position.  (That's when the regular points are by-passed and the retard breaker-points are engaged.)  In such aircraft (Mooney's, most Beech's and twin Cessna's) the engine can "kick-back" pulling an unwary person back into the moving propeller.   Shower-of-Sparks (Bendix vibrator type) magneto systems are good candidates to refuse to hand-prop, no matter how much propping experience one has.

(As a side-story, I once saw an ex-Marine hand-prop a DC-3!!  I couldn't believe how he did it.  He walked the prop through about 4 turns and got the prop just where he wanted it, called to the cockpit "Contact!" and when the Captain switched the mags on, he took a running start with a bath-towel rolled up and padded onto his left shoulder and threw a football-style "block" against the lower prop blade.  His momentum carried him on through, and the engine, amid huge blue clouds of smoke belched and caught!  After the batteries were re-charged they started the other one normally and flew away.)</HTML>

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Re: Generator too small to carry load

<HTML> The worst hand propping senerio I tackled was a DeHavilland Beaver. One time was all it took to tell me "I'll NEVER do that again"  When that thing popped off - I thought I'd had it!  I think it was the size of those blades whizzing in front of my face that did it..</HTML>

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Re: Generator too small to carry load

<HTML>"Pulling the CB or fuse on either an alternator OR a generator does exactly the same thing."  Sure, but only if you have one...

My 172, before my alternator conversion, had NO pullable breakers, and NO split switch.

Hmmm...George, if I'd heard your advice and thought about this ahead of time, I may have just put in a pullable breaker instead of the whole conversion tongue     I'm a big fan of pullable breakers for everything...

A65-12.  "That simply is unworthy of belief."  My understanding was that the -12 meant electric starter on it and the -8 was without an electric starter.  I didn't consider the A vs. C as significant.  Again, if you are actually concerned about this, call Paul King, (831) 724-2759 here at Watsonville.  While you're at it, schedule your next check ride with him, and stop in SCFC for some coffee  <SHAMELESS PLUG>  tongue

As far as DC-3's, I'm REALLY glad I'm not the FO if hand/shoulder propping it is part of the job...hell, my little baby ace 74-42 prop looks menacing enough...and no, I don't have electric start (I may have to install one to make the first A65-12, after all, it's an experimental...)   tongue

Mark</HTML>

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Re: Generator too small to carry load

<HTML>Mr. Horn,
re:"your words are good and (mostly) correct. A battery's purpose is NOT for starting. "

Then.......ummmm...we don't need to turn the Master switch on, and somehow our engines will start ?  I'll try that tomorrow and let you know if it works. <G>

Maybe you're referring to a Sukhoi aircraft that uses compressed air for starting ?  Then the battery is for backup electrical  purposes, maybe ?

Best,
Dale</HTML>

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