TIGHAR
Amelia Earhart Search Forum => Radio Reflections => Topic started by: Randy W Kerr on December 25, 2010, 12:14:00 PM
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I have been wandering around the site looking for any information on expected battery life for the Electra. My reason is that everywhere it seems assumed that AE made a wheels down landing on Niku. This practice runs contrary to everything I have been taught about off-field landings on unsure surfaces. ( I hold a Commercial certificate) The dangers of tucking your nose under and flipping your plane landing on soft sand or a rough reef top would lead me to choose a wheels up landing. But every thread that mentions it suggests that the radios needed the #2 engine running to charge the battery. Anyone have figures on battery life??
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I don't know the answer to your question in terms of battery life, but it's probably irrelevant - drop the Electra into salt water and it's going to short out the electrical system - including the batteries and the radio.
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Ding ding..the light just went on. Even if they landed at low tide they would have flooded soon after.
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The portion of the reef where the available evidence suggests that the landing was made is smooth enough ride a bicycle, let alone land an Electra with big fat tires.
At low tide the reef is dry. At high tide the water is not high enough to reach either of the batteries or any of the radio components.
Nearly all of the credible post-loss radio signals occur at times when the water level on the reef was low enough to run an engine.
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"The portion of the reef where the available evidence suggests that the landing was made is smooth enough ride a bicycle," I understood that from other sources, but having seen a lot of other reefs where that was not the case it occurred to me that not knowing the conditions wheels up might have been a thought. Even with a low pass it can be hard to see the conditions clearly. I speak as one who got to watch from the right seat as a nearly pristine Beech 18 was turned to scrap under similar circumstances. Excuse me if I ask a few uninformed questions as I try to educate myself on the fascinating story.
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"The portion of the reef where the available evidence suggests that the landing was made is smooth enough ride a bicycle," I understood that from other sources, but having seen a lot of other reefs where that was not the case it occurred to me that not knowing the conditions wheels up might have been a thought. Even with a low pass it can be hard to see the conditions clearly. I speak as one who got to watch from the right seat as a nearly pristine Beech 18 was turned to scrap under similar circumstances. Excuse me if I ask a few uninformed questions as I try to educate myself on the fascinating story.
See "Landing on the Reef?" (http://tighar.org/wiki/Landing_on_the_Reef%3F) for some details about the reef and the Electra undercarriage.
"Post-loss Radio Messages--Overview, Battery Life." (http://tighar.org/wiki/Post-loss_Radio_Messages--Overview#Battery_Life)
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A couple things to keep in mind when considering how Earhart may have viewed her options upon arriving over Gardner:
- In 1937, intentional wheels-up landings in retractable gear aircraft were pretty much unknown and there was no such thing as "a standard ditching procedure" for the Model 10.
- From a crew survival standpoint, landing a land plane in the water is almost never preferable to even a crash-landing on land.
- Earhart's professional and financial future was tied up in that uninsured airplane. A water landing would mean the loss of the certain aircraft.
- At low tide, from the air, Nikumaroro looks like it is surrounded by an empty parking lot.
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Keep in mind AE also knew what the craft would look like with a wheels up landing i.e. the first leg.
Ted Campbell
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A couple things to keep in mind when considering how Earhart may have viewed her options upon arriving over Gardner:
- In 1937, intentional wheels-up landings in retractable gear aircraft were pretty much unknown and there was no such thing as "a standard ditching procedure" for the Model 10.
- From a crew survival standpoint, landing a land plane in the water is almost never preferable to even a crash-landing on land.
- Earhart's professional and financial future was tied up in that uninsured airplane. A water landing would mean the loss of the certain aircraft.
- At low tide, from the air, Nikumaroro looks like it is surrounded by an empty parking lot.
Understood...I was not advocating that a water landing was a good option, unless drilled and in a craft conducive to a quick exit water landings are a last resort...I was suggesting rather that bellying in on unknown terrain is usually the safest choice..the plane was going to be lost in any event...but hooking a wheel and flipping upside down could have been instantly fatal..not that the eventual outcome was different. It is obviously a moot point in any event given the reality that a belly-landed aircraft would have rendered transmissions for the length of time they are believed to have occurred impossible.
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Hello folks
I have just read this thread and refered to the battery life details which state.
"Both batteries were rated at 85 ampere-hours. If both were at full charge on arrival at Niku -- a reasonable assumption -- there would have been enough charge for about 90 minutes of transmission time. The total transmission time required for all of the credible post-loss signals is 451 minutes."
So, we have two 85 amp hour batteries total 170 A/hr, say we can take them down to about half capacity before they are of less use * ( if they are lead acid type ).
That gives us 85A/hrs in total.
The question I need to ask is, what is the current consumption of the radio on transmission? Or, what is its output power in watts and the battery voltage?
If we know this we can work it out more exactly. Does anyone have this information?
Regards
Antonia
* you would think though that they would continue to use the radio until it would no longer work at all ( if they had access to it, dependent on weather/sea conditions ) meaning batteries very dead
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The question I need to ask is, what is the current consumption of the radio on transmission? Or, what is its output power in watts and the battery voltage?
"Radio equipment on NR16020" (http://tighar.org/wiki/Radio_equipment_on_NR16020)
"A Technical Analysis of the Western Electric Radio Communications Equipment Installed on Board Lockheed Electra NR16020" (http://tighar.org/Projects/Earhart/Research/ResearchPapers/ElectraRadios/ElectraRadios.htm#)
"WE-13C Transmitter Harmonic Power Output" (http://tighar.org/Projects/Earhart/Research/ResearchPapers/Brandenburg/WE-13.htm)
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The question I need to ask is, what is the current consumption of the radio on transmission? Or, what is its output power in watts and the battery voltage?
"Radio equipment on NR16020" (http://tighar.org/wiki/Radio_equipment_on_NR16020)
"A Technical Analysis of the Western Electric Radio Communications Equipment Installed on Board Lockheed Electra NR16020" (http://tighar.org/Projects/Earhart/Research/ResearchPapers/ElectraRadios/ElectraRadios.htm#)
"WE-13C Transmitter Harmonic Power Output" (http://tighar.org/Projects/Earhart/Research/ResearchPapers/Brandenburg/WE-13.htm)
My thanks, it has not failed to amaze me, the amount of work you folks have done on this.
Kind reagrds
Antonia
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The question I need to ask is, what is the current consumption of the radio on transmission? Or, what is its output power in watts and the battery voltage?
"Radio equipment on NR16020" (http://tighar.org/wiki/Radio_equipment_on_NR16020)
"A Technical Analysis of the Western Electric Radio Communications Equipment Installed on Board Lockheed Electra NR16020" (http://tighar.org/Projects/Earhart/Research/ResearchPapers/ElectraRadios/ElectraRadios.htm#)
"WE-13C Transmitter Harmonic Power Output" (http://tighar.org/Projects/Earhart/Research/ResearchPapers/Brandenburg/WE-13.htm)
My thanks, it has not failed to amaze me, the amount of work you folks have done on this.
You're welcome. If you'd like to pull together some of the information from the sources--with links at the ready for each item--I'd be happy to pop your findings into "Radio equipment on NR16020" (http://tighar.org/wiki/Radio_equipment_on_NR16020). No harm in summarizing and consolidating things ...
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Antonia,
The relationship between battery performance and the radio electrical load is very complex, and will be detailed in a forthcoming research paper. Meanwhile, here's a brief overview of key points that bear on your question:
The batteries were Exide 6-FHM-13-1, 12-volt, lead-acid type, with 85 AH capacity.
Each battery could be switched onto or off the main electrical bus. We assume both batteries were fully charged on arrival at Niku, and that Earhart kept one on the bus, with the other off-bus as a safety standby.
The generator was an Eclipse type E-5, rated to provide 15 volts DC, mounted on the starboard (right) engine. A crucial question for our analysis was whether the E-5 would deliver 15 volts when the engine was idling at 900 RPM. Paul Mantz, Earhart's technical advisor, said in 1937 that the Pratt & Whitney Wasp S3H1 engine -- the type used on the Electra -- burned 6 gallons per hour at 900 RPM. TIGHAR verified the engine and generator performance in 2009, in an experiment using an S3H1 engine and an E-5 generator. This result established that 900 RPM was the lowest speed Earhart could use for battery charging, and that she would burn 6 gph while doing so.
The time required to recharge the battery after a transmission period, and the associated engine fuel burn, are important considerations in the post-loss signals.
Ideally, we would have the Electra battery charging specifications, but we have been unable to find that information. We could not use a modern 85 AH battery as a proxy because we could not be sure that the the internal resistance and charging efficiency of the 1937 battery were the same as in a modern battery. Therefore, it was necessary to derive the battery's performance parameters from first principles, using published empirical research data for aircraft lead-acid batteries of the period.
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 transmitter high-voltage power supply was a dynamotor that drew 65 amps at 12 volts, and thus could function at virtually full output even with the battery approaching zero charge. Hence, the combined available "end game" battery charge -- after all engine fuel was exhausted -- was 170 AH, if both batteries were fully charged at fuel exhaustion.
The credible post-loss signals occurred in clusters, or blocks. We assume that Earhart kept the engine running to operate the generator continuously during each block, rather than start and stop the engine for each transmission. We have developed a computer model that does the time line bookkeeping, giving the battery state of charge (SOC) -- and fuel remaining -- after each credible signal, and after a user-specified recharging period following each signal block. After we have identified all the credible post-loss signals, we'll plug them in to the model and see how battery charge and fuel cosnumption behaved over time.
Of course, the amount of fuel Earhart had on arrival at Niku depends on when she landed. We don't know exactly when that was , but we know the latest possible arrival time, which was constrained by tide depth on the reef. The maximum safe water depth for landing the Elctra was 6 inches (0.15 meter). Signal propagaton analysis for the last Earhart signal heard by the Coast Guard cutter Itasca on July 2, 1937, gives us a bound on Earhart's distance from Niku then, and thus her earliest possiible arrival time. These two limits bound the uncertainty of fuel remaing on arrival, and factor into our analysis.
The tide level also constrained when Earhart could run the engine for battery charging. The required propeller tip clearance was 24 inches (0.6 meter), so engine operation was impossible when the water level exceeded that limit.
Now, let's take a brief look at the dynamics of the electrical load and battery recharge.
The generator output current was regulator-limited to 50 amps.
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).
The transmitter drew 65 amps when transmitting, raisng the total current load to 68 amps.
With the transmitter in standby, the generator could supply the 8 amp ambient load and have current to spare for charging the battery. But when the transmitter was keyed, the generator could supply only 50 of the required 68 amps. The battery would supply the remaining 18 amps, losing 18 ampere-minutes (0.3 AH) of charge for each minute of transmission time. About 13 minutes of charging time was needed to restore charge for each minute of transmission time, if the starting battery SOC was near the top of the exponential charging curve. At lower starting SOC, where the curve is steeper, the recharge time was on the order of 2 minutes for each minute of transmission.
Earhart's only way to monitor battery SOC was to watch the generator current output on the ammeter. The current would decrease toward the 8-amp ambient load as the battery approached full charge. But it could take a long time to get those last few ampere-hours into the battery if she wanted to recharge to 100%, and Earhart would have to be careful not to spend her precious fuel too lavishly. We don't know what strategy she used, but we can experimentally investigate the range of options and their effects using the computer model mentioned above.
I hope this helps. Let me know if you have other questions.
Bob
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I have been wandering around the site looking for any information on expected battery life for the Electra. My reason is that everywhere it seems assumed that AE made a wheels down landing on Niku. This practice runs contrary to everything I have been taught about off-field landings on unsure surfaces. ( I hold a Commercial certificate) The dangers of tucking your nose under and flipping your plane landing on soft sand or a rough reef top would lead me to choose a wheels up landing. But every thread that mentions it suggests that the radios needed the #2 engine running to charge the battery. Anyone have figures on battery life??
As a pilot myself, I have concluded that Amelia was deficient in two areas: 1. She was not a great pilot. 2. She thought she was a great pilot. A very dangerous combination usually resulting in death by crash at some point. She would have thought she could do anything in an airplane.
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As a pilot myself, I have concluded that Amelia was deficient in two areas: 1. She was not a great pilot. 2. She thought she was a great pilot. A very dangerous combination usually resulting in death by crash at some point. She would have thought she could do anything in an airplane.
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This is what would have run through my mind on arriving at Niku flying the Lockheed.
A low level flyover to assess the landing zone near the Norwich City – flat, easy access to the up beach parking area (near the trees) and near an easily identifiable landmark i.e. the ship.
If I could get the plane on the ground in tact – landing gear down – and out of the danger of the water surrounding the island there just might be a chance to contact rescue, get refueled and fly out of the mess I’ve found myself in.
I would have landed with the ocean to my left trying to keep the ship as close as I can to my rollout (thus enhancing my visibility from either the sea or air).
I am afraid that as AE rolled out she caught the left gear in a hole under the waterline, the plane took a hard left turn either twisting off the left gear or damaging it to the point of no return. The spin was so violent that FE was thrown into the side wall with subsequent head injury.
The plane is now pointed into the surf and unable to be moved. The right engine is still above the water line when the tide is in and is able to run when the tide is out. When the tide is out we can still get into the plane to run it and transmit the radio. It’s only a matter of time before the plane heads into the ocean. Each time I run it for the radio it inches further toward the sea – the brakes are fading because I am losing hydraulic fluid out of the damaged left gear. Finally, no control on forward motion when I run up the engine and there-she-goes.
Ted Campbell
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As a pilot myself, I have concluded that Amelia was deficient in two areas: 1. She was not a great pilot. 2. She thought she was a great pilot. A very dangerous combination usually resulting in death by crash at some point. She would have thought she could do anything in an airplane.
Judgment is always better in hindsight. When I was learning to fly, I had the advantage of learning from many, many prior aircraft accidents. In fact, that's what a good pilot does: read up on aircraft accidents and learn from them. But Amelia was a pioneer. She really didn't have much history to go on. Plus a lot less was known back then about instrument flying and the instruments themselves were a lot more complicated.
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Ric and Gang...
Hey fellas!!! Over the course of the past twenty years I've had the opportunity to work for the best battery manufacturing plant in the world!!! One of the things I do know is that salt water is not good for any battery. However, I'm sure that as Ric has mentioned that distress signals could have been made before the plane was taken and pulled over the reefs edge!!! Anyway, for alot of our overseas markets we have to concentrate on making sure the posts are greased thoroughly to keep them from corroding and to make sure that acid levels are at their finest. We also primarily concentrate on DI water usage!!! Getting back with the salt water, the battery or batteries don't necessarily have to sit in salt water to get ruined. Just the air itself from the ocean can have a significant effect on performance and the life of the battery. Afterall, she did fly over much of the ocean, and probably took on alot of salty air from the ocean. As for the battery life...It depends on the care of the battery...What shape it was in before her last port of call...Did her and Fred check this...Were there any cracks or leaks coming from the battery!!!! In most good cases as I have learned over the years...A good battery can last for hours....Anywhere from 4-6 hours without charging!!!! But, it depends on the total integrity of the battery...Such as the plates, terminals, acid levels, clean posts, and container integrity. Anyway, as in most cases when we run our batteries down in our cars..We have to usually charge them or jump start them with another battery source and then drive the car for quite some time to recharge the system...Such would be the case if her battery was down...But, if it wasn't///Good question Ric....How many batteries does the Electra have in it...and how many batteries can you get by with running it at half to full capacity? Also, if there is more than one battery...how many batteries does it take to just operate the radio alone??? Has your staff looked into this? Anyway, this is totally exciting and very resourceful in a way!!!! You also have to remember that whatever fluid she might have had in those batteries is all she can run with, unless she had extra acid laying in the plane...which I highly doubt...and if she did add salt water...then she definately would be sitting for awhile!!! Anyway, need to run a series of tests on running an Electra with just a small portion of batteries to the normal usage and how many batteries can you run the radio off of!!!!
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Bob Brandenburg has done extensive work on battery life aboard the Electra and, with the cooperation and assistance of Covington Aircraft Engines in Okmulgee, OK, I ran tests using a Pratt & Whitney R-1340 engine connected to an Eclipse generator just like the one on Earhart's Electra. We were able to confirm Paul Mantz' comment in 1937 that Earhart should have been able to charge her batteries by running the starboard engine at 900 RPM burning 6 gallons of fuel per hour. We'll have a full report on the battery research and its impact on the post-loss radio signals question.
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Bob Brandenburg's analysis is humbling - excellent. The cluster / block nature of the transmissions supports what a pilot would do, IMO.
As others have pointed out, no, AE was not a 'great' pilot - and while she no doubt suffered from some degree of believing she was a great pilot, she would have had some firm working knowledge of generator / battery capability by the time of a Gardner arrival, as would have FN most likely. Even a rudementary grasp would have been sharpened as one realized the cause and effect of diminishing batteries and relatively slow restoration rates, and even dim memories of things told and warned-of in an earlier time would likely have come to the fore in AE's mind as she struggled to transmit from the Electra.
A reef landing would not have been terribly hard after the pilot dragged the 'field' a time or two to understand what was there. It is often the psychological barriers that create the worst hazards and when we 'have the picture' a landing is easier. AE may not have been a great pilot, but she managed to get the Electra airborne out of Lae with a huge load of fuel - she would have been far lighter and easier to handle by the time of reaching that reef.
I share the belief that the airplane eventually went off the reef - but have no idea that it was by her own power. I don't know of the Electra having a complex hydraulic braking system that would compromise both sides if a gear were damaged or torn away - in 1937 it may have just been a larger version of the simple master-slave system on each side that we see on lighter planes today, each independent of the other. Does anyone out there know the details on that? Can be found out if it becomes an important point I guess.
If the right gear remained intact and the right engine thereby supported clear of the reef, the right brake should have been sufficient to hold at reasonable thrust for recharging the batteries. If not, some form of chocking the wheel would have come into play if it were me struggling with the beast (maybe that's how FN's head injury occurred... ; ) - that's just bad, sorry).
The main point seems to be however that it was likely that AE got the chance to make those transmissions, however imperfectly the whole flight had been handled, and the pattern we can identify from the evidence supports the power curve Bob Brandenburg so ably discerned from what we can know of the Electra's systems and what was reported.
AE had a reasonable chance to do what is believed was done; at some point the airplane was lost - brakes and chocks are no match for much of a storm that could have come and gone, washing that shoreline with violent surf for a few hours.
Tangled wreckage at the teeth of the surf may have been what Emily S. and others reported knowing about - perhaps it was the rusting gear of the Electra, just barely jutting above the surf at very low tides where it came to rest for some years before finally sliding off to the deep during some big storm.
LTM -
My Piper products, and most civil aircraft I have ever flown, have independent braking systems for left and right side. In fact I blew a wheel cylinder on landing one day in a good cross wind on a relatively short field. Got a bit hairy trying to stop, and keep the plane on the runway, with only one side breaking! Turning during taxiing was a bit interesting too. So, she should have been able to hold the airplane with right engine running and only right brakes. I would think.
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Each time I run it for the radio it inches further toward the sea – the brakes are fading because I am losing hydraulic fluid out of the damaged left gear. Finally, no control on forward motion when I run up the engine and there-she-goes.
I would not imagine the accident that way, for I cannot imagine that AE would have left the plane inch toward the sea every time she ran the engine without having tried to stop it with whatever she could find to be put in front of the wheels.
I would imagine instead that for all but the last of her emission days, everything runs OK, the Electra remains stable. On the fourth or fifth day however (sorry, I did not take the time to check that in the post-loss radio-call journal), may be because the high tide is everyday a bit higher (isn't it ?), maybe because she runs the engine everyday a little faster to compensate for the decreased efficiency of battery charging due to the salt water spray that progressively shortens out the electrical circuit, maybe because the brakes have been weakened by their stay in water, maybe because of all causes together ... Suddenly the plane leaps forward and turns left to the open sea before she can stop the engine. Accidents of that sort may happen so suddenly that even professionals get trapped (Airbus broke an A340 that way in Toulouse only three years ago!)
It may be at this very time that Noonan gets hurt. I cannot easily imagine that a landing so successful that it left the plane able to operate one engine would hurt anybody who had his or her belt fastened. In contradistinction they probably did not have their seat belts fastened just for making radio calls ...
It may be on this day that Betty hears what is actually AE’s last call. Doesn’t the info stand somewhere on the forum that there was no engine noise in the background? Anyway Betty hears AE crying. That does not seem consistent with the attitude of an aviation pioneer, but would be the reaction of anybody who has just made his or her plane fall from the coral platform where it had safely stood since its so successful landing. The catastrophe has just happened! Now the plane maybe hanging on the coral edge just by one wheel, with only a few hours of emission left depending on the charge of the batteries, if it does not slip completely into water before that time. And the rising tide (which should not be a problem if the plane was still on the coral plateau) makes things worse: Betty says she hears AE ‘having trouble getting water so high the plane was slipping’.
Finally the coral edge acts as a saw that separates the plane in two parts, one that remains on coral, progressively torn to pieces that will give the few aluminum artifacts found ashore and eventually the ‘wheel of fortune’, and the other that sinks down the coral cliff, where we all hope to find it in a not too far future.
Christophe (who, as a glider pilot, will not blame anybody for the way (s)he runs his or her engines)
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Seems more likely to me that the transmissions stopped because they just exhausted the little fuel left. And a storm, or high winds, resulting in high tides just swept the Electra off the reef. It could have moved it a little bit towards the reef everyday...no doubt. Then one day a rough tide....gone.
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The radio could have consumed batteries fast without the engine running. The radios back then were tube type, and it appeared from the schematics, one of them used a Dynamotor power supply to turn 12V into 1050V. The combination of the tube filaments (a 282A is a 10V tube at 3.0 Amps each and one of her radios uses 4 of them, plus 2 6L6s at 0.9A at 6.3V). This doesn't count the amperage of the Dynamotor or the current required to turn 12V into 1050V, which is a multiple of 87.5. So even if the plate current of the entire radio was 200ma (which it could be more or less), this would draw 17.5 amps at 12V not including the dynamotor or filaments at 100% transformer efficiency, which most are less than that. If you add the filaments and 200ma B+ together, you get over 30 amps of consumption!
http://www.nj7p.org/Tube4.php?tube=282A
http://www.nj7p.org/Tube4.php?tube=6L6
http://tighar.org/Projects/Earhart/Archives/Research/ResearchPapers/ElectraRadios/Schematic2.html\
I would be willing to think that this radio would flatten the batteries quickly.
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From what i remember, the radio drew 60-something amps when transmitting. I am also pretty certain this is more that the generators max output, which in practice means that you would drain the batteries even with the engine(s) running. I've heard a couple of stories from the 50s and 60s about people waiting in their cars for some time with the engine idling, headlights, (tube)radio and ventilation blower on, and when they stepped on the brakes to put it in gear, the brake lights made the battery voltage drop to the point where the engine died. The old DC generators, at least in cars, were nowhere near as efficient as the alternators we know today, and it would take a long time just to regenerate the power used to start an engine. The aircraft engines obviously had magneto ignition that would keep them running without any battery power, but they still has to be started. I'm not claiming to be an expert, but my guess is that even if the gas tanks were full when they landed, they would run out of power after a few hours transmission time anyway if they started and stopped the engines each time.