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Tim Gard

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Re: Watch That Battery
« Reply #30 on: August 07, 2014, 05:28:22 PM »

Tim,

You seem to labor under some basic misconceptions about 100 octane fuel

Jeff,
If AE did specifically plan to depart Lae using 100 octane, then she needs to do just that.
In order for the carbs to be full of 100 octane before starting the takeoff roll one needs to have allowed sufficient time for that process to occur. Interconnecting fuel lines need time to be purged of the lower octane fuel.
Startup, taxi and particularly runup is a reasonable way of ensuring that.

and perhaps as to how the DC generator on the Electra operated, as Mark Samuels has pointed out.

Mark has considered the Electra's generator to be a perfect device, devoid of frequency response, internal resistance and RPM sensitivity. I'm sure it was quite efficient for its time, but perfect it was not.

100 octane would have had nothing to do with 'ease of starting'.

I don't remember saying that.
In order for the carbs to be full of 100 octane before starting the takeoff roll one needs to have allowed sufficient time for that process to occur. Interconnecting fuel lines need time to be purged of the lower octane fuel.
Startup, taxi and particularly runup is a reasonable way of ensuring that.

It was used for take-off at high power settings to offset detonation, that's the only reason the ship bothered to have a reserve of 100 octane.  At start or low power settings, it makes essentially no difference whatsoever to the engine or how it performs.

Agreed. I don't recall saying differently.

As to what I read earlier regarding your take on the take-off at Lae, I doubt seriously that Earhart switched tanks immediately, etc., etc. as accounting for her fairly dramatic run-off the end and drop toward the water, etc.  Why would any pilot taking off in a heavily loaded airplane choose that moment to swiitch tanks from 100 octane to 80? 

We share the same purport- that AE carried 100 octane of necessity.
So when did AE deselect 100 octane? Why not 1st power reduction if she had to reduce power anyway?

Earhart did some nutty things in her time - especially with radios, but I don't recall fuel mishandling - and that's prime-time for screwing that up royally.  There would be no harm in continuing on 100 octane for some time, especially while still under climb power (even with the power reduced). 

Are you now arguing against the need for 100 octane for the Howland departure, yet you just argued that it was necessary for Lae?

More likely she might have wanted to conserve a bit for take-off at Howland (seems like they had none, but I'm not clear on that at moment).

Then you *do* agree there was a need to switch tanks ASAP?

As to the electrical generation - Samuels is basically correct, although I would agree that voltage falls off on a DC brush type generator as RPM falls. 

Agreed.

That said, it WILL charge well down to at least around 900 RPM,

I haven't said it wouldn't charge. I am saying that at 900 RPM:
1. It will take a damn long time to charge.
2. It will not output full current.

The driving fact here is the need to provide current for the transmitter which is not possible at 900 RPM.

and I believe TIGHAR actually has test data showing lower RPMs than that on a live engine of the same type (which is important to determining how much fuel might have been available to charge the batteries, and in turn power the radios).

I've seen the video. Note my "2 to 1" quote.

Perhaps I've not read all of your suppositions well, but note as well that the batteries depended directly on battery state; one could not get enough current out of that puny generator to power the radio transmitter directly.  Transmissions had to be limited with an eye on battery state, then the battery charge replenished.

Which is exactly why low RPM won't cut it. AE was paranoid enough about the battery condition when the engine was running cruise power and she was trying to communicate with Itasca. How did she feel when the engine was running less than cruise power and she was attempting the same thing?

Your discourse is interesting, but to me also a bit convoluted, frankly (not to personally criticize, just to point out that it's confusing to the whole point, at least as I understand it).  It might be profitable to consider these points and read up on what Jacobsen and others have contributed here as to these things - and consider that the matter isn't so complex: fuel available on the ground (regardless of octane) would have been the stuff of transmissions, for as long as it - or the bird, lasted.  The engine could consume, if memory serves, as little as around 6 - 8 gallons an hour probably at a battery-charging low RPM.  But please don't take my word for that (I'm hip shooting the details from memory anyway), it can be looked up on this site.

After lengthy consideration some things have become obvious to me. I accept they may not be obvious to you.


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Tim Gard

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Re: Watch That Battery
« Reply #31 on: August 07, 2014, 05:42:38 PM »


That is a common misconception.  Have you ever tried to charge a dead battery with an alternator by driving around for a couple hours.  You will wake up in the morning with another dead battery. An alternator is designed to top off a battery, not fully charge it.  The alternator will put out the voltage to keep the ignition system running and the engine as long as you don't have your lights and heater on. Turn the key off and you'll be getting out the jumper cables again.

Many times and successfully too so I can't relate to your anecdote unless you are describing a flat battery that has sulphated because it was left fully discharged for an extended period. Such a battery will have shorted cells.

Such a battery *might* be recovered by the use of a specialised charger that charges and discharges in cycles to restore the plate material.
 
Otherwise I have successfully recovered heavily discharged batteries with alternators many times.

We are not discussing neglected and sulphated batteries here.
We are discussing the responsible management of 2 batteries that had only recently proven their good condition by repeatedly starting 2 big radial engines.


 
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Mark Samuels

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Re: Watch That Battery
« Reply #32 on: August 07, 2014, 06:14:51 PM »


Mark has considered the Electra's generator to be a perfect device, devoid of frequency response, internal resistance and RPM sensitivity. I'm sure it was quite efficient for its time, but perfect it was not.

Ah, never said that, I've had my troubles with generators in my day.


Quote
That said, it WILL charge well down to at least around 900 RPM,
I haven't said it wouldn't charge. I am saying that at 900 RPM:
1. It will take a damn long time to charge.
2. It will not output full current.

The driving fact here is the need to provide current for the transmitter which is not possible at 900 RPM.

Maybe what you fail to understand is that the generator on the Electra L10 E had an max output of 50 amps against a draw of 65 amps required by the transmitter not withstanding other things that might have required power.  The radios had to be shut down long enough for the generator to get the 85 amp hour batteries up to charge.  My understanding is they used the smaller battery for starting the engine and the larger one by the navigators desk for powering the radios.

http://tighar.org/smf/index.php/topic,252.msg2222.html#msg2222

« Last Edit: August 07, 2014, 06:31:21 PM by Mark Samuels »
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pilotart

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Re: Watch That Battery
« Reply #33 on: August 07, 2014, 07:17:46 PM »

... Have you ever tried to charge a dead battery with an alternator by driving around for a couple hours.  You will wake up in the morning with another dead battery. An alternator is designed to top off a battery, not fully charge it.  The alternator will put out the voltage to keep the ignition system running and the engine as long as you don't have your lights and heater on. Turn the key off and you'll be getting out the jumper cables again.
I have done that many times and as long as the battery and charging system was healthy, it worked just fine with no need for jumper on next start.

On the other hand, with a completely dead battery and no 14 volt charger or vehicle available to jump from, then trying to jump from a fully charged 12 Volt boat battery (twice the size of the cars battery) would not start it.  I just bought a pocket-size Cobra JumPak 400 Amp that is supposed to provide three 3 second jump starts from a full charge, if I ever leave my parking lights on again... :-[

One of the advantages of an aircraft (or auto) with an alternator over a generator is that an alternator will continue to charge at an idle RPM.

Best way for her to judge RPM needed would have been to watch the Ammeter while transmitting.  Generator could not put out enough for a positive reading at any RPM but she could find the minimum RPM for a minimum discharge reading and then lean the fuel mixture to the maximum for that RPM.  This would produce the most fuel efficient RPM for maximum battery charging, if she was doing a minimum of transmitting, her batteries could remain fully charged at a lower RPM and she could listen longer for less fuel.

One of the disadvantages is that an alternator will not self-excite and if the battery is completely dead, the alternator won't put out at all. 

Push starting won't work at all but I have jump-started many autos with alternators and the excite current from the jumper cable was enough to excite the alternator and it charged just fine.  Even providing enough charge in the battery (lights, heater and all) for subsequent starts after running a while, but battery should still be charged if possible as they last longer if fully charged.

Landed at Grand Cayman many years ago and after a few days, wanted to fly to Little Cayman.  Battery was completely dead (a reading light on a 'hot-buss' had been left on), so I had Cayman Airways use a Ground Power Cart to start the engines, flew to Little Cayman, shut down and battery was still completely dead.  The Battery switch activated a relay powered from the battery side, so even with Alternators producing plenty of current, there was nothing to close that battery relay to send current to the battery.  Only battery charger was a little 12 Volt at the Dive Shop, charged a 24 Volt battery over several days by contacting a plate in the middle and charging each half of the battery separately.

Turbine (Jet) engines do not use alternators (some single engine models have a backup alternator), they have Starter/Generators, Battery supplies 600 to 1800 amps (at 24 volts) to spin it up to 20% RPM and then after it is lit-off and passing 40% or so, the automatic controller transforms the starter into a generator that can produce many 100's of amps.

I agree that she would have wanted to allow enough ground running to assure that the carburetors were full of 100 octane before take-off, but engines would start just as easily on lower  octane.  It would be especially dangerous to attempt a take-off on a nearly empty (usually below 1/4 ) tank.

100 octane was necessary for that extra 100 Horsepower per-side (increased supercharger boosted compression) and if she lost one engine at anywhere near her take-off weight, she was already in the coffin corner no matter how much power was available from the other engine.  That Lockheed did not even have feathering props...
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JNev

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Re: Watch That Battery
« Reply #34 on: August 07, 2014, 09:24:51 PM »

Tim,

You seem to labor under some basic misconceptions about 100 octane fuel

Jeff,
If AE did specifically plan to depart Lae using 100 octane, then she needs to do just that.
In order for the carbs to be full of 100 octane before starting the takeoff roll one needs to have allowed sufficient time for that process to occur. Interconnecting fuel lines need time to be purged of the lower octane fuel.
Startup, taxi and particularly runup is a reasonable way of ensuring that.

and perhaps as to how the DC generator on the Electra operated, as Mark Samuels has pointed out.

Mark has considered the Electra's generator to be a perfect device, devoid of frequency response, internal resistance and RPM sensitivity. I'm sure it was quite efficient for its time, but perfect it was not.

100 octane would have had nothing to do with 'ease of starting'.

I don't remember saying that.
In order for the carbs to be full of 100 octane before starting the takeoff roll one needs to have allowed sufficient time for that process to occur. Interconnecting fuel lines need time to be purged of the lower octane fuel.
Startup, taxi and particularly runup is a reasonable way of ensuring that.

It was used for take-off at high power settings to offset detonation, that's the only reason the ship bothered to have a reserve of 100 octane.  At start or low power settings, it makes essentially no difference whatsoever to the engine or how it performs.

Agreed. I don't recall saying differently.

I see that now - I could have read your post more thoroughly I suppose.

As to what I read earlier regarding your take on the take-off at Lae, I doubt seriously that Earhart switched tanks immediately, etc., etc. as accounting for her fairly dramatic run-off the end and drop toward the water, etc.  Why would any pilot taking off in a heavily loaded airplane choose that moment to swiitch tanks from 100 octane to 80? 

We share the same purport- that AE carried 100 octane of necessity.
So when did AE deselect 100 octane? Why not 1st power reduction if she had to reduce power anyway?

Could have, but makes more sense to me to reduce power first (and I'll just about guarantee that she would not have immediately upon departing the end of the runway - that settling was a thing too close), thence switch tanks when all up and away with some margin.  There's no need to be that stingy - there was ample 100 octane for the Lae and Howland take-offs if reasonably managed.

Earhart did some nutty things in her time - especially with radios, but I don't recall fuel mishandling - and that's prime-time for screwing that up royally.  There would be no harm in continuing on 100 octane for some time, especially while still under climb power (even with the power reduced). 

Are you now arguing against the need for 100 octane for the Howland departure, yet you just argued that it was necessary for Lae?

I've said nor argued any such thing.  In fact, to repeat - there was ample 100 octane for both take-offs with reasonable management.  The dramatic cowboy power reduction and tank switching off the end of the cliff as you envision isn't necessary and no reasonable pilot that I know of would manage a take-off that way.

More likely she might have wanted to conserve a bit for take-off at Howland (seems like they had none, but I'm not clear on that at moment).

Then you *do* agree there was a need to switch tanks ASAP?

You argue for argument's sake.  No need to switch as you have described; I've already said what I think is reasonable.

How much 100 octane do you think she would have burned in 5 minutes at take-off and initial climb?  If the  bird was burning 100 gallons an hour it would be less than 10 gallons out of 100, so why would you want to switch tanks after just peeling your sphincter off the grass at Lae and nursing the bird low across the water for a few hundred yards?

As to the electrical generation - Samuels is basically correct, although I would agree that voltage falls off on a DC brush type generator as RPM falls. 

Agreed.

That said, it WILL charge well down to at least around 900 RPM,

I haven't said it wouldn't charge. I am saying that at 900 RPM:
1. It will take a damn long time to charge.
2. It will not output full current.

The driving fact here is the need to provide current for the transmitter which is not possible at 900 RPM.

It wasn't even possible to provide enough current for the transmitter even at full throttle, but only about half the 65 amps the radio drew when transmitting at a higher power setting.  Read what Bradenburg and others have offered on the details.

and I believe TIGHAR actually has test data showing lower RPMs than that on a live engine of the same type (which is important to determining how much fuel might have been available to charge the batteries, and in turn power the radios).

I've seen the video. Note my "2 to 1" quote.

Perhaps I've not read all of your suppositions well, but note as well that the batteries depended directly on battery state; one could not get enough current out of that puny generator to power the radio transmitter directly.  Transmissions had to be limited with an eye on battery state, then the battery charge replenished.

Quote
Which is exactly why low RPM won't cut it. AE was paranoid enough about the battery condition when the engine was running cruise power and she was trying to communicate with Itasca. How did she feel when the engine was running less than cruise power and she was attempting the same thing?

Where do you get the information on Earhart's 'paranoia'?  I'd overlooked that she suffered from that (although she might have benefitted had she realized how her own habits were out to get her).  There is a balance to fuel conservation and periodic transmitting (see linked material); there is no reason for a high power setting to make such transmissions.

Your discourse is interesting, but to me also a bit convoluted, frankly (not to personally criticize, just to point out that it's confusing to the whole point, at least as I understand it).  It might be profitable to consider these points and read up on what Jacobsen and others have contributed here as to these things - and consider that the matter isn't so complex: fuel available on the ground (regardless of octane) would have been the stuff of transmissions, for as long as it - or the bird, lasted.  The engine could consume, if memory serves, as little as around 6 - 8 gallons an hour probably at a battery-charging low RPM.  But please don't take my word for that (I'm hip shooting the details from memory anyway), it can be looked up on this site.

After lengthy consideration some things have become obvious to me. I accept they may not be obvious to you.

Obvious is in the eye of the beholder; many things are obvious to me.  I invite your scrutiny of the many words posted in this forum and related material herein on the topic; perhaps more will become obvious to you should you do so. 

It is obvious to me that supposing Earhart rashly switched tanks at the worst possible moment would have gained her nothing but risk, and that there is no reason to conjecture so far to test the hypothesis of a Niku landing; I fail to see the point of it, however obvious it may be to you, that's all.
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Tim Gard

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Re: Watch That Battery
« Reply #35 on: August 08, 2014, 03:58:18 AM »


Jeff,

I'm delighted that you don't argue for the sake of arguing, that you don't believe in saturating your posts with tons of quotes and that you are not one of those people who echoes the equivalent of expressing the finger like you say some drivers do.



 
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Tim Gard

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Re: Watch That Battery
« Reply #36 on: August 08, 2014, 04:06:40 AM »


Maybe what you fail to understand is that the generator on the Electra L10 E had an max output of 50 amps against a draw of 65 amps required by the transmitter not withstanding other things that might have required power.  The radios had to be shut down long enough for the generator to get the 85 amp hour batteries up to charge.  My understanding is they used the smaller battery for starting the engine and the larger one by the navigators desk for powering the radios.

The term I've used previously is "transmission duty cycle". 

I'll be ending the sport for you and Jeff in this thread now. 

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Tim Gard

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Re: Watch That Battery
« Reply #37 on: August 08, 2014, 04:10:38 AM »


Well said Art.

I agree with every word.


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« Last Edit: August 08, 2014, 05:20:21 AM by Tim Gard »
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JNev

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Re: Watch That Battery
« Reply #38 on: August 08, 2014, 06:38:25 AM »


Jeff,

I'm delighted that you don't argue for the sake of arguing, that you don't believe in saturating your posts with tons of quotes and that you are not one of those people who echoes the equivalent of expressing the finger like you say some drivers do.

I'm delighted that you are delighted, Tim.

I guess there's just something about clairvoyants who extrapolate bits and pieces of technical lore into 'the answer' that draws those things out in me.  I think it is pure fop.  The icing on the cake is all the over-parsing of 100 octane use - 'gas is gas' when it comes to cranking an engine and charging a battery.

One thing is for damn sure - if you are a pilot, you are one I'd never fly with given your cowboy view of take-off / climb power management: whatever her faults and propensity for losing her way, Earhart way outclassed the judgment you've expressed in that regard here.  So maybe it comes down to defending the lady in some way.

Have a nice day.
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JNev

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Re: Watch That Battery
« Reply #39 on: August 08, 2014, 06:51:55 AM »

I am reminded that there was ample 100 octane available at Howland according to the Black Cruise Report .
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JNev

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Re: Watch That Battery
« Reply #40 on: August 08, 2014, 07:38:17 AM »

In fairness to you, Tim, I'll more carefully comment on the particulars here that appear tortured to me -

I've given further thought to this and it forced me to address the following question.

How soon after the Lae departure did AE effect the tank change from 100 octane to the lower octane?

Answer: As soon as possible after becoming airborne.

Eyewitnesses reported the Electra dipping towards the ocean, then recovering. At first I thought that was the Electra coming out of ground effect, but now I think it was both 1st power reduction and 1st tank change.

My reasoning follows:

Since AE had only to clear sea level, it gave her the option of using an efficient and slow cruise climb of 50 - 100 ft/min, rather than a step climb that guaranteed burning 100 octane at maximum rate (60 US Gal per hour?). The reduced weight from the fuel burn aided in the climb performance.
 
AE had to first reduce power to select the lower octane fuel in order to avoid blowing holes in pistons through detonation/pre-ignition, as well as reduce power to conserve fuel and lean back to 43 US gal per hour.

Having dipped the tanks just before departure, having used a defined period for startup, taxi, takeoff and climbout, having selected away from the 100 octane tank, AE now knew how much fuel remained in that tank especially having performed the procedure on so many previous departures.

That means AE knew how much 100 octane remained upon arrival at Gardiner and also knew  preserving that fuel gave her a known running time for the starboard engine once she selected that tank.

Most respectfully, Tim -

Why the urgency to switch tanks so quickly at a very busy and potentially hazardous point in the flight?  It gains nothing.  A safer approach to your notion of a gentle cruise climb (which is itself something most of us would favor) would be to allow the craft to find a stabilized climb and gain safe altitude, throttling back when safe (and respecting any METO time limits).  There would be no urgency to switch tanks - 100 octane would be fine, and there was an ample supply awaiting NR16020 at Howland as delivered by the Itasca. 

How much 100 octane would be consumed by using this reasonable conservatism?  Assuming warm-up, taxi, take-off and the first 5 minutes of climb to gain some safety margin, all pulling from the 100 octane reserve, would use something on the order of perhaps 10 gallons at the outside (but don't take my word for it, dig into the real numbers and do the math).  That hardly makes a compelling point of reaching for fuel tank controls and making a switch on the sea deck just after sailing off the end of the grass runway at Lae: fly the airplane first, gain some comfort margin, then tidy up the long-term needs.  That's especially true for single pilot ops in an airplane like the Electra (Fred was in the back - the lady wanted to do it herself).

Your reasoning as to Earhart somehow wishing to preserve 100 octane so as to 'know what was left in tank' (if I follow your logic, in part) seems to be pure conjecture as we have nothing from Earhart suggesting such a concern.  Further, the presence of 100 octane vs. 80 octane at the end of the day means nothing because for battery charging: fuel is fuel (perhaps you didn't intend the distinction, but somehow I read it in the sum of your point).

This reasoning is why her focus was heavily on the state of the battery "Watch that battery" rather than transmitting for all they were worth pending an imminent and permanent stopping of the starboard engine due to fuel exhaustion.
 
Because I agree with Bill de Cleef's 1200 RPM minimum for charging, my estimate is that the 100 octane reserve provided for 4 hours running of the starboard engine at half cruise consumption (21.5 divided by 2 US gal / hour = 10.25 US gal / hour).

You are of course free to agree with anyone's  opinion on 'minimum for charging', but the fact is that generator and engine combination have been demonstrated as adequately charging for the purpose we're talking about at around 900 RPM, and with very low fuel consumption - around 8 GPH.

"Watch that battery" was a necessity: no matter how much engine power Earhart applied, the poor little Eclipse generator could only give about 1/2 of what the radio transmitter demanded.  The battery would necessarily deplete, even if Earhart were running the right engine at full boost / high power, 100 octane and all. 

'Standby' (receiving) was a bit different - the generator could provide for that and battery charging.  Yes, higher RPMs would charge marginally faster - but fuel consumption does not increase on a linear scale, but goes up exponentially when one bumps the shiny knobs forward.  Patience...

Doesn't some inner pilot instinct tell you 'conserve' when you have very limited fuel and a need to transmit as-can?  Watch "Island in the Sky" (written by Gann, portrayed by John Wayne and notable others) for a fair demonstration of the dilemma of transmitting on old sets and power demands: it left shitty choices.  Somehow my pilot instincts - which seem to agree with what we know about even Mantz's views, are that the least smelly choice would be, if one could start an engine, to use modest power, 'watch the battery' and periodically make 'burst' transmissions.

If Earhart actually did ever say "watch that battery", then I believe (my opinion) that she was well attuned to these things and carefully managing all that we've discussed.  Despite her other shortcomings - ground loops, off course arrival in Africa, radio nonsense, the lady managed to fly a respectfully demanding transport 3/4 of the way around the world without significant mishap - not bad.  That take-off at Lae was a piece of fine work by anyone's standard: I'd bet not one man watching that day would have eagerly traded places - it could have easily gone wrong and been turned into a smoking hole.  As you rightly pointed out elsewhere of late, tail-draggers aren't very forgiving to bad man-handling. 

Her keeping her cool and dropping into ground effect as she sailed off the end of the runway was an impressive move, whatever the reason - and none of us will ever know for sure how expected or not that maneuver was.  It might have been a momentarily desperate response to very marginal take-off performance that day (been there with south Georgia pines in the windshield), or it could have been one of those near-joyful acts of conservative energy conservation to gain the best energy state for safety that looks more dramatic than it really is.  She apparently handled it well - I don't recall any dramatic report of it from the flying community - just one of those one-off things that turned out well and wasn't too shocking under the circumstances of the day.

I bother to elaborate on all this for the sake of the lady's character and judgment - not out of chivalry, but of common sense: some of her basic stuff was pretty darn sound, and I have severe doubts (my judgment) that she would over-gun the engines in a fuel-limited situation for the sake of overly aggressive transmission times.
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Mark Samuels

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Re: Watch That Battery
« Reply #41 on: August 08, 2014, 08:41:20 AM »


Maybe what you fail to understand is that the generator on the Electra L10 E had an max output of 50 amps against a draw of 65 amps required by the transmitter not withstanding other things that might have required power.  The radios had to be shut down long enough for the generator to get the 85 amp hour batteries up to charge.  My understanding is they used the smaller battery for starting the engine and the larger one by the navigators desk for powering the radios.

The term I've used previously is "transmission duty cycle".

Ah yes, that pesky "transmission duty cycle".  Seems that Ms Earhart was well aware since she, on a number of occasions transmitted that she would listen at different periods on the hour.  Unfortunately as it were, she was transmitting and listening on the wrong frequency, I think.


I'll be ending the sport for you and Jeff in this thread now.

Thank you, its been fun but not 'real fun'. ;)

Hold the Heading Tim, we'll get there sooner or later. ;D
« Last Edit: August 08, 2014, 08:46:02 AM by Mark Samuels »
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