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[Tim Gard]

What conclusions can we draw about the fuel remaining in the 80 octane tank?

Is it possible to conclude that the after takeoff level was still present after arrival and shutdown at Gardiner?
Did Amelia switch to that tank as part of a potential go round procedure before arrival at Gardiner?
Did the reduced gross weight mitigate the need for using 80 octane under takeoff power?

My take is that as much 80 octane as possible was preserved post Lae departure because it was scarce and it would be needed to depart Howland.

If Amelia's expectation at touchdown Gardiner was that she would soon be refuelled and continue the flight from Gardiner, then either way she would need to preserve the 80 octane.

Tim, there was no 80 octane fuel on board the aircraft. Most of the fuel was 87 octane, later called 80/87 octane, with 100 octane reserved for takeoff. See here.

Many thanks. The post has been edited.

[Tim Mellon]

My first thought on measuring the available fuel, after the gauges of course, would be a dipstick.

Note that the fuselage tanks are filled through ports on the side of the fuselage, so the filler necks do not go straight down to the tanks.  How you gonna stick those tanks?

Perhaps they could have used the bamboo pole that was used to pass messages back and forth.

It appears that it might have been flexible enough to reach the bottom Starboard corner of each tank.

But an accurate reading would require the aircraft to be on level ground.

[Tim Gard]

My initial impression was that the statement was driven by an ammeter showing discharge for an extended period.

Bob Brandenburg refers to the presence of an ammeter and the interpretation of its readings.

I could imagine myself saying "Watch that battery" under the same pressure.

[C.W. Herndon]

Yes. I'm aware of that and commented so ...

"That means any transmission drained the battery (or batteries depending on what Amelia had on line at that instant)."

They kept one fully charged battery isolated during the transmissions to mitigate the risk of losing them both as per Bob Brandenburg's text at your link.

That means the concern was directed towards the online battery.

Sorry I missed that Tim. Thanks for the correction.

[Tim Gard]

Ric asks "How you gonna stick those tanks?"
I'll offer one possible answer: "you don't."  You pump all remaining fuel in those tanks up to the 118 gallon starboard "header tank" (my terminology) that has the sight-glass gage next to the cockpit door, which (I'm guessing) feeds the engines through the selector valve.  The cockpit had a manual fuel pump that could be selected to pump from any tank, as I recall.  I think it might be safe to assume it could pump to the tank that has the sight-glass.  Once the fuel level is below the bottom of the sight-glass, you've only got some fixed small quantity of fuel remaining, unless you discover a tank you hadn't previously tried pumping from, perhaps a forgotten tank partly full of 80 octane that you hadn't used since takeoff.
I don't recall confirming that the tank with the sight-glass was even a fuel tank, so this is supposition on my part.

Does the lowest photo down show the  visigauge?

Your description makes good sense. I think those rods are pull to activate. Much easier to pull than rotate and if they did rotate, lining them up is futile.

If the visigauge shows an adequate level - meaning the transmission fuel burn is not rapidly nearing bottom, then there is no imminent fuel shortage crisis.
If that be the case then you do need to preserve battery for a future start.


 

[John Ousterhout]

Yes, a "Visigauge" might have been the brand of sight glass, but a friend offered a correction to my "possible answer" - the hand pump in the cockpit (called a "stripper pump") could only pump to a selected wing tank, not to what I called the "header tank" in the fuselage.  The fuel system diagram shows the arrangement of valves, plumbing and tanks, but not the sight glass.
So, to modify my previous possible answer - one would use the stripper pump to pump all other tanks dry into a convenient wing tank, possibly one with a gauge.
It's worth noting that aircraft fuel gauges are not to be used to measure fuel quantity, but only to indicate the presence of fuel to the most approximate degree, if that.  I don't know how this might have been taught in Amelia's day, but in modern times it's drilled into flight students.  If a gauge reads "E", the tank might be half full, or empty.  If it reads "F", it might be half full, or full.  If Amelia reported running short of fuel, and was relying on a gauge, then she might have been running on fumes, or had a half tank left.
The sight glass might have been connected to an oil tank, but that's also conjecture on my part.  We just don't know.

[Tim Gard]

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.

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).

 

[Ric Gillespie]

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.

Answer:  No way to know but it would seem reasonable that she would change tanks as soon after takeoff as possible.

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.

I would not switch tanks until I had reached a safe altitude - at least a couple thousand feet.  Again, no way to know what she did.

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.

I don't think she had any choice.  The thing would barely fly at that weight.  The balls-to-the-wall anticipated fuel burn for the first hour of flight, according to British researcher Roy Nesbit (see attached excerpt from a 1993 TIGHAR report), was 100 gph.
 

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.

According to Nesbit's table, which agrees with the Kelly Johnson telegrams, Earhart wouldn't achieve 43 gph until 7 hours into the flight.

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.

Where does it say she did any of that?

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.

If your speculation is correct.

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.
 

It makes sense that she would be concerned about the state of the battery.

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)

In 1937, Paul Mantz told a newspaper reporter that Earhart could charge her batteries at 900 RPM burning 6 gph.  We confirmed that by experimentation in 2009 at Covington Aircraft Engines in Okmulgee, OK.  We put an R-1340 on a test stand connected to an Eclipse E-5 generator just like Earhart's and were able to get a positive charge of 14.25 volts (enough to trip the set point and allow the battery to charge) at 900 RPM burning 6 gph.

[Tim Gard]

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.

Where does it say she did any of that?

Having already covered vast expanses cossetting her 100 octane, AE has no motive to depart from that MO at Lae. Her Howland departure is as dependent on preserving the 100 octane as was the Lae departure itself. AE needs assurance of the remaining quantity of 100 octane before she can attempt the next takeoff. In doing so, the burn rate of the previous flight is also confirmed.
 
Also, running with a power setting so high that 100 octane is a must, creates a coffin corner. Once the 100 octane is gone, AE is left piloting an Electra that cannot fly on the remaining low octane fuel without destroying both engines. That implies an earlier power reduction to have been practical, necessary and advisable.

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)

In 1937, Paul Mantz told a newspaper reporter that Earhart could charge her batteries at 900 RPM burning 6 gph.  We confirmed that by experimentation in 2009 at Covington Aircraft Engines in Okmulgee, OK.  We put an R-1340 on a test stand connected to an Eclipse E-5 generator just like Earhart's and were able to get a positive charge of 14.25 volts (enough to trip the set point and allow the battery to charge) at 900 RPM burning 6 gph.

I recall the test conclusion being that AE used a "2 to 1".
Mantz' comment taken literally says the batteries could be charged at 900 RPM. It doesn't state 900 RPM to be capable of providing the generator's max current.

"Watch that battery" relates to the transmission duty cycle which becomes complex.

1. Transmitting with the engine at that RPM which also produces max current (1200 RPM), reduces the load on the batter(y/ies).
2. Transmitting with the engine at that RPM which also produces max current (1200 RPM), reduces the time to recharge the batter(y/ies) once the transmission cycle has completed.
3. The battery can be recharged at 900 RPM but the recharge will take longer because the current output is less.
4. The longer the recharge time, the greater the fuel burn.
5. Higher RPM means the battery load will be least and the recharge time will be least.
6. 900 RPM will impact the transmission quality due to voltage drop.

Integrating all that info is the ammeter, which tells the simple truth that the battery is or isn't being recharged or does not need charging (centred on 0).

[Ric Gillespie]

Having already covered vast expanses cossetting her 100 octane, AE has no motive to depart from that MO at Lae. Her Howland departure is as dependent on preserving the 100 octane as was the Lae departure itself. AE needs assurance of the remaining quantity of 100 octane before she can attempt the next takeoff. In doing so, the burn rate of the previous flight is also confirmed.

I agree that she would naturally want to conserve her 100 octane but I don't think it's possible to say exactly when she switched tanks.  What I see you doing that worries me is that you decide what seems logical and reasonable to you and then you state it as a fact.  If you do that you're building a house of cards.
 

Also, running with a power setting so high that 100 octane is a must, creates a coffin corner. Once the 100 octane is gone, AE is left piloting an Electra that cannot fly on the remaining low octane fuel without destroying both engines. That implies an earlier power reduction to have been practical, necessary and advisable.

Where do you get that?  As far as I know she can run those engines at full throttle and at max RPM on 87 octane without hurting them.

"Watch that battery" relates to the transmission duty cycle which becomes complex.

You just did it again.  Your statement is an opinion, not a fact.  If you don't make a clear distinction you lose track of what you actually know.

1. Transmitting with the engine at that RPM which also produces max current (1200 RPM), reduces the load on the batter(y/ies).
2. Transmitting with the engine at that RPM which also produces max current (1200 RPM), reduces the time to recharge the batter(y/ies) once the transmission cycle has completed.
3. The battery can be recharged at 900 RPM but the recharge will take longer because the current output is less.
4. The longer the recharge time, the greater the fuel burn.
5. Higher RPM means the battery load will be least and the recharge time will be least.
6. 900 RPM will impact the transmission quality due to voltage drop.

I'd like to see the numbers that support your statements. Our tests show that the generator charge does not max out at 1200 RPM.  There is no way to know what RPMs she used to charge the battery.  What we do know is that she could have used as little as 900 RPM.

Integrating all that info is the ammeter, which tells the simple truth that the battery is or isn't being recharged or does not need charging (centred on 0).

Yes, and I think all we can say about "Watch that battery" is that it might be a warning not to let the battery get run down to the point where they would not be able to start the engine.

[Tim Gard]

Where do you get that?  As far as I know she can run those engines at full throttle and at max RPM on 87 octane without hurting them.

That then obviates the need to carry, isolate and take off using 100 octane. Why she didn't  previously burn it while it was available then fully top up the 100 octane tank at Lae to give herself the best chance makes no sense. Her fuel carrying awareness was such that she chose to leave such items as a life raft behind, yet preserved a partially full tank of 100 octane defies rationale.
 

"Watch that battery" relates to the transmission duty cycle which becomes complex.

You just did it again.  Your statement is an opinion, not a fact.  If you don't make a clear distinction you lose track of what you actually know.

I see your point.

I've spent a long time pondering the variables. My electrical engineering background amplifies the importance and emphasis AE placed on the statement.

The ammeter is all she has to ascertain the battery condition, which relates to the next start which is also dependent on having the fuel to support same. For as long as the ammeter reads discharge the situation is in crisis. Because the ammeter integrates the voltage and current peaks to produce a reading, it also reports the rate of recharge.

Low RPM low transmission time = short recharge time, reduced fuel burn but ineffective communication.
Low RPM high transmission time = long recharge time, increased fuel burn but effective communication.
High RPM low transmission time = shortened recharge time, increased fuel burn but ineffective communication.
High RPM high transmission time = shortened recharge time, increased fuel burn but effective communication.

The ammeter's reading showing a more rapid rate of battery recharging is the stress yardstick.
The sooner it comes out of discharge the better.
The sooner it comes out of charge and falls back towards 0, even better still.
 

I'd like to see the numbers that support your statements. Our tests show that the generator charge does not max out at 1200 RPM. 

I agree completely.
The max current output is likely to occur even higher than 1200 RPM.

There is no way to know what RPMs she used to charge the battery.  What we do know is that she could have used as little as 900 RPM.

I agree.
Again it is not likely to be as low as 900 RPM. The lower the RPM figure the less efficient the battery recharge process due to the non-linear response of the batteries. That is the longer the engine will have to be run to recover. The higher the RPM the lower the recharge time giving the best return for the fuel burn. Again the ammeter tells the story.

At higher RPM the needle spends less time in heavy discharge.

Integrating all that info is the ammeter, which tells the simple truth that the battery is or isn't being recharged or does not need charging (centred on 0).

Yes, and I think all we can say about "Watch that battery" is that it might be a warning not to let the battery get run down to the point where they would not be able to start the engine.

My focus remains:

1. If they thought fuel exhaustion was imminent then "damn the torpedos, full steam ahead".
2. If they thought fuel exhaustion was not imminent due to some reassuring factor, then "watch that battery."

I'm building the case that the policy of preserving the 100 octane was still in practise on arrival at Gardiner Island and that provided the reassurance of an effective restart.

[Mark Samuels]

I recall the test conclusion being that AE used a "2 to 1".
Mantz' comment taken literally says the batteries could be charged at 900 RPM. It doesn't state 900 RPM to be capable of providing the generator's max current.

Mr. Gard, It is my understanding that max current is controlled by the voltage regulator which is normally 14.2 volts.  Any more than that you will eventually boil the batteries and ruin them.  Mantz I am sure determined that the generator on the Electra would put out 14.2 volts at 900 RPM.  Less than that would discharge the batteries and eventually stall the engine.  You could run that engine at 1800 RPM and you would still only by generating 14.2 volts to the battery.  So your premise that 1200 RPM would charge the batteries faster is false.  What affects the length of time the generator takes to charge the batteries is the load on them i.e. lights etc.  With no load, the time it takes  to completely recharge is the same at 900 RPM as it is at 1200 RPM given Mantz's testing.  We are not talking alternators here.  That is a whole different kettle of fish.

[Tim Gard]

Mr. Gard, It is my understanding that max current is controlled by the voltage regulator which is normally 14.2 volts. 

You're assuming that because the generator could make 14.2 volts at 900 RPM no load, that it could make the same voltage at full load at that RPM.

The answer is that it can't. Max current output will occur at 14.2 volts and when the the armature windings are passing through the field at that RPM which provides same. That figure does not occur at minimum RPM.

Any more than that you will eventually boil the batteries and ruin them.

Agree.
It is certainly the job of the voltage regulator to regulate the voltage and regulating the voltage down to that level prevents boiled batteries.

Mantz I am sure determined that the generator on the Electra would put out 14.2 volts at 900 RPM. 

Agree.

Less than that would discharge the batteries and eventually stall the engine. 

Agree that the batteries would become discharged.
Disagree that the engine would stall:
1. The engine used magnetos for spark ignition so completely independent of battery state.
2. When a generator drops below charge voltage, the cut out relay breaks the circuit between battery and generator. That prevents the battery from discharging into and through the generator which also takes the load off the engine. It's as if the generator isn't even there.

You could run that engine at 1800 RPM and you would still only by generating 14.2 volts to the battery. 

Agree, however the increased rate of armature windings passing the field increases the generator's ability to provide current.

So your premise that 1200 RPM would charge the batteries faster is false.

Even with an alternator you will see the battery recharge faster with an increase in RPM because the rotor is passing the field windings at a more rapid rate.
With a generator you will see the battery recharge faster with an increase in RPM because the armature windings are passing the field windings at a more rapid rate.

What affects the length of time the generator takes to charge the batteries is the load on them i.e. lights etc.  With no load, the time it takes  to completely recharge is the same at 900 RPM as it is at 1200 RPM.  We are not talking alternators here.  That is a whole different kettle of fish.

Increasing the load on a generator can decrease the rate of recharge of the battery if the generator's current limit for that RPM is exceeded.

[JNev]

Where do you get that?  As far as I know she can run those engines at full throttle and at max RPM on 87 octane without hurting them.

That then obviates the need to carry, isolate and take off using 100 octane. Why she didn't  previously burn it while it was available then fully top up the 100 octane tank at Lae to give herself the best chance makes no sense. Her fuel carrying awareness was such that she chose to leave such items as a life raft behind, yet preserved a partially full tank of 100 octane defies rationale.
 

"Watch that battery" relates to the transmission duty cycle which becomes complex.

You just did it again.  Your statement is an opinion, not a fact.  If you don't make a clear distinction you lose track of what you actually know.

I see your point.

I've spent a long time pondering the variables. My electrical engineering background amplifies the importance and emphasis AE placed on the statement.

The ammeter is all she has to ascertain the battery condition, which relates to the next start which is also dependent on having the fuel to support same. For as long as the ammeter reads discharge the situation is in crisis. Because the ammeter integrates the voltage and current peaks to produce a reading, it also reports the rate of recharge.

Low RPM low transmission time = short recharge time, reduced fuel burn but ineffective communication.
Low RPM high transmission time = long recharge time, increased fuel burn but effective communication.
High RPM low transmission time = shortened recharge time, increased fuel burn but ineffective communication.
High RPM high transmission time = shortened recharge time, increased fuel burn but effective communication.

The ammeter's reading showing a more rapid rate of battery recharging is the stress yardstick.
The sooner it comes out of discharge the better.
The sooner it comes out of charge and falls back towards 0, even better still.
 

I'd like to see the numbers that support your statements. Our tests show that the generator charge does not max out at 1200 RPM. 

I agree completely.
The max current output is likely to occur even higher than 1200 RPM.

There is no way to know what RPMs she used to charge the battery.  What we do know is that she could have used as little as 900 RPM.

I agree.
Again it is not likely to be as low as 900 RPM. The lower the RPM figure the less efficient the battery recharge process due to the non-linear response of the batteries. That is the longer the engine will have to be run to recover. The higher the RPM the lower the recharge time giving the best return for the fuel burn. Again the ammeter tells the story.

At higher RPM the needle spends less time in heavy discharge.

Integrating all that info is the ammeter, which tells the simple truth that the battery is or isn't being recharged or does not need charging (centred on 0).

Yes, and I think all we can say about "Watch that battery" is that it might be a warning not to let the battery get run down to the point where they would not be able to start the engine.

My focus remains:

1. If they thought fuel exhaustion was imminent then "damn the torpedos, full steam ahead".
2. If they thought fuel exhaustion was not imminent due to some reassuring factor, then "watch that battery."

I'm building the case that the policy of preserving the 100 octane was still in practise on arrival at Gardiner Island and that provided the reassurance of an effective restart.

Tim,

You seem to labor under some basic misconceptions about 100 octane fuel and perhaps as to how the DC generator on the Electra operated, as Mark Samuels has pointed out.

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

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?  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).  I don't recall all the limits on the engine off-hand, and perhaps there was a 1 or several minute limit at METO, but it matters not - the 100 octane could be burned quite happily, indefinitely.  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).

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.  That said, it WILL charge well down to at least around 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).

Perhaps I've not read all of your suppositions well, but note as well that the radio 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.

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.

[Mark Samuels]

Even with an alternator you will see the battery recharge faster with an increase in RPM because the rotor is passing the field windings at a more rapid rate.
With a generator you will see the battery recharge faster with an increase in RPM because the armature windings are passing the field windings at a more rapid rate.

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.