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Author Topic: FAQ: Fuel Consumption  (Read 39827 times)

Martin X. Moleski, SJ

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Re: Fuel Consumption
« Reply #30 on: July 15, 2011, 06:42:01 PM »

It's with great trepidation that I make another comment to the same writeup. In the sentence before the one under discussion, Bob wrote "Aircraft lead-acid battery cells of the period had a specific gravity range of 1300 at full charge to 1110 at fully discharged, with corresponding voltage range of 12.86 volts to 11.81 volts." The specific gravities should be 1.300 and 1.100, not 1300 and 1100.

Corrected.  I kept the last digit of the discharged state (1110 became 1.11), just in case the measurement is that accurate.  Specific gravity is new by me. 
LTM,

           Marty
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Martin X. Moleski, SJ

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Re: Fuel Consumption
« Reply #31 on: July 15, 2011, 06:53:49 PM »

But in deference to putting a finer point on the whole equation, the transmitter standby circuitry (including relays, tube warming, etc.) was powered by 12 volts directly from the batteries; when the transmitter was activated, it was powered by 1050 volts from the dynamotor, which was first powered by 12 volts from the batteries.

OK.  I've modified the table in the article to include this description.  Rather than trying to work it into the quotation from Bob's original research paper, I've just let it stand alone at the end of the table as a summary of the situation.
LTM,

           Marty
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Chuck Varney

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Re: Fuel Consumption
« Reply #32 on: July 15, 2011, 08:36:33 PM »

But in deference to putting a finer point on the whole equation, the transmitter standby circuitry (including relays, tube warming, etc.) was powered by 12 volts directly from the batteries; when the transmitter was activated, it was powered by 1050 volts from the dynamotor, which was first powered by 12 volts from the batteries.

OK.  I've modified the table in the article to include this description.  Rather than trying to work it into the quotation from Bob's original research paper, I've just let it stand alone at the end of the table as a summary of the situation.

Marty,

Unfortunately, that change to the table prompts two further comments:

1) Change the attribution for the first part from Bob Brandenburg to Mike Everette.

2) Delete the Jeffrey Neville entry. The transmitter was not powered by 1050 volts, per se. The transmitter received 1050 volts (at pins 13 and 16) from the dynamotor when it was activated for transmitting. This voltage was applied to the plates of the three tubes comprising the 1st and 2nd RF amplifiers. It was dropped across series resistors R10.1 and R10.2 to 380 V and applied to the plates of the oscillator and audio amplifier tubes (one each). That's all that 1050 volts was used for.

The transmitter received 12 volts from the battery for the tube filaments (pins 3 and 4 for +12 V and pins 1 and 2 for -12 V, or ground)--regardless of whether the transmitter was in standby (in which case it drew ~ 6 A), or in transmit (for which the average draw was 10.6 A). The transmitter received 12 volts from the battery on pin 5 for relays S4, S5, and S6, and for the oscillator crystal heaters if they were employed. Again, for both standby and transmit.

Chuck
« Last Edit: July 16, 2011, 04:15:56 PM by Chuck Varney »
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Martin X. Moleski, SJ

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Re: Fuel Consumption
« Reply #33 on: July 15, 2011, 09:30:29 PM »

1) Change the attribution for the first part from Bob Brandenburg to Mike Everette.

OK.

Quote

2) Delete the Jeffrey Neville entry. The transmitter was not powered by 1050 volts, per se. The transmitter received 1050 volts (at pins 13 and 16) from the dynamotor when it was activated for transmitting. This voltage was applied to the plates of the three tubes comprising the 1st and 2nd RF amplifiers. It was dropped across series resistors R10.1 and R10.2 to 380 V and applied to the plates of the oscillator and audio amplifier tubes (one each). That's all that 1050 volts was used for.

The transmitter received 12 volts from the battery for the tube filaments (pins 3 and 4 for +12 V and pins 1 and 2 for -12 V, or ground)--regardless of whether the transmitter was in Standby (in which case it drew ~ 6 A), or in Transmit (for which the average draw was 10.6 A). The transmitter received 12 volts from the battery on pin 5 for the oscillator crystal heaters, if they were employed. Again, for both Standby and Transmit. The control voltage applied at pin 7 for the relay coils was likely to have been 12 volts from the battery as well, but I have nothing that explicitly states that. In any case, that too would be supplied in both Standby and Transmit modes.

I've added your new wrinkle to the table in the article.

Quote
The more times I read Bob's battery epistle, the more things I find wrong. In this sentence he added 1, 6, and 2 and came up with 8:

"We assume an ambient current load of 8 amps during each signal block: radio receiver on (1 amp), transmitter in standby (6 amps for vacuum tube filaments), and the cockpit instrument lights (2 amps)."

We'll have to wait for Bob to tell us which number is in error (8, 6, or 2).

Let the one among us who has never made a miscalculation throw the first stone.  :-\
LTM,

           Marty
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Chuck Varney

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Re: Fuel Consumption
« Reply #34 on: July 16, 2011, 02:58:08 AM »


Let the one among us who has never made a miscalculation throw the first stone.  :-\

I agree, Marty. I logged in to delete that final comment as unduly picky, but, alas,  too late.

Chuck
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Martin X. Moleski, SJ

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Re: Fuel Consumption
« Reply #35 on: July 16, 2011, 06:14:09 AM »

... I logged in to delete that final comment as unduly picky, but, alas,  too late.

It's OK.  There are cases where "two heads are better than one."  I think this is one of them.   :)
LTM,

           Marty
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Chuck Varney

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Re: Fuel Consumption
« Reply #36 on: July 16, 2011, 08:32:55 AM »

For that reason, again, I suggest Mr. Varney or any others who wish to correct or challenge contact Bob directly with any critique - that would preserve authorship where deserved and be far more productive. 

You mean something like this, perhaps?
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Martin X. Moleski, SJ

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Re: Fuel Consumption
« Reply #37 on: July 16, 2011, 09:58:39 AM »

Marty, please just delete the entry you attributed to me - it is not in error but obviously it is not going to be easily understood as I'd intended.  It only adds obfuscation to the points already well made by Brandenburg and Everette. 

OK.

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I also disagree with adding the tedium of transmitting circuitry to this topic on 'fuel consumption', but so be it if others believe it contributes here.

Well, I'm interested in having a relatively accurate description on the wiki of how things were designed to work in the aircraft.  Thread drift happens.  "Fuel consumption" is not only about the fuel consumed en route but also about fuel available to power the transmitter for the post-loss messages; the power requirement for the transmission is linked to the fuel available to recharge the batteries and/or contribute to transmission time.

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I'll also note again that the more important point of this topic really seems to be whether AE and FN could have had the fuel to make it to Howland area, thence Niku, thence able to support a number of transmissions from that place.  The rational answer seems to be "YES"; the aggregate message from Messrs. Brandenburg and Everette, despite minor errors, seems to support that reliably.

Agreed.  It seems to me that the post-loss radio receptions can't be ruled beyond the bounds of possibility on the basis of the power consumption of the radio system.
LTM,

           Marty
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h.a.c. van asten

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Re: Fuel Consumption
« Reply #38 on: September 12, 2011, 04:26:36 AM »

Fuel expenditure was not excessively high , if you would like to see the concerning computation (updated from 1996) , communicate an email address to hac.vanasten@gmail.com for a transcription (from dutch) of the final results .
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Richard C Cooke

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Re: Fuel Consumption
« Reply #39 on: November 16, 2011, 07:47:42 PM »

To go back to the question of knowing how much fuel they were using.

Each time they had to switch tanks they would have know how long it had taken to use whatever was in it, so they had several checks of how much fuel they had left, and how fast they were using it.

Richard Cooke
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JNev

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Re: Fuel Consumption
« Reply #40 on: November 17, 2011, 11:24:29 AM »

To go back to the question of knowing how much fuel they were using.

Each time they had to switch tanks they would have know how long it had taken to use whatever was in it, so they had several checks of how much fuel they had left, and how fast they were using it.

Richard Cooke

Good point.

Unfortunately this topic got beaten into the weeds over how much fuel may have been used for the transmission attempts and I believe we lost the more important big picture.  How many ounces were burned making "juice" for the radios is incidental compared to how many gallons may have been left to get NR16020 to Gardner, and thence to run all the iron needed (engine + generator) to run the radio after missing Howland.

But I think the abundant evidence on this site affirms the spirit of your observation - fuel management was accounted for in the 'plan' and it is reasonable to believe AE had a rational grip on that aspect of flight management given the information and tools she had in-hand.  Switching tanks by a schedule would indicate some notion of how much was consumed per tank before moving to the next, etc.

LTM -
- Jeff Neville

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Martin X. Moleski, SJ

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Re: Fuel Consumption
« Reply #41 on: November 19, 2011, 08:02:06 AM »

N.B.: My apologies to the original author, Irvine John Donald.  I had intended to Quote his post, but Modified it instead. My bad.  :P  

... Her radio message said they were running north and south.

Her last transmission also indicated that she was switching to her "daytime frequency."

You (and many others) seem not to understand the problems with AE's antennas along with the generic difficulty any day of the week of radio propagation.

Your assumption is that changing frequencies would have made no difference with propagation and reception of her transmissions.

I believe that that assumption is unwarranted.  The Coast Guard tried to get her to stay on 3105 kcs because they were receiving those transmissions without difficulty.  They knew from experience that some frequencies propagate less well than others.

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Why wouldn't she have been talking the whole time? 

I imagine that she was talking the whole time, more or less.

I also imagine that there was something about her antennas and that time of day that kept her transmissions from being heard.

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The radio operators said they thought her voice sounded more anxious on some of the last transmissions.

People see what they want to see and hear what they want to hear.  AE had been advised in Lae to "pitch her voice higher" when transmitting in order to improve the intelligibility of her transmissions.  It is conceivable that she was acting on this advice.
LTM,

           Marty
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« Last Edit: November 19, 2011, 08:04:29 AM by Martin X. Moleski, SJ »
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Irvine John Donald

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Re: Fuel Consumption
« Reply #42 on: November 19, 2011, 07:12:10 PM »

Thanks Marty

All good points. Switching frequencies and antenna issues means she could have been talking the whole time and nobody receiving.  I think I can live with that explanation.

When transmitting the post loss messages she was back on 3105 kcs and was heard so it very likely was the frequency  and antenna issue.

Okay so now we believe she had the fuel to get to Gardiner and run her engine to transmit. Credible sources heard her. Now why wasn't Gardiner identified in the radio messages?  Perhaps time for a new thread.
Respectfully Submitted;

Irv
 
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