As this was broached in the "working the flight plan in reverse" thread, reading about the 3105 "donut" and reading about the earlier repairs to the radios (
http://tighar.org/wiki/Failure_to_communicate#The_fuse_may_have_blown_again) I thought I'd ask this:
Was the dynamotor fused? If so, has anyone thought to set up a working WE13C transmitter into an appropriate antenna, monitor the current draw on the filament and the plate supplies and then key the mic while changing frequencies, say from from 3105 to 6210? Yes, I am a radio engineer and the thought makes me cringe, too. Would there be a momentary overload as the oscillator and tuning/tank circuits are switched while the plates are energized, enough to exceed the rating of a fuse in the dynamotor circuit? If it was fused, consider the following scenario:
AE indicates she will be switching frequencies from 3105 to 6210 and perhaps either keys the mic by mistake while changing frequencies or continues to hold it down inadvertently after uttering her famous last words. The system overloads, the fuse pops, the transmitter can't transmit. Due to the poor radio communications they've already had with the Itasca, they may have continued "sending" not knowing that they are now no longer being heard. As was mentioned in the other thread, observing an ammeter in either the charging circuit or the via optional RF/final amplifier stage metering if it was so equipped, would be secondary to the fuel gauges. Cockpit noise level and vibration would make it impossible to feel or hear if the dynamotor is running when the mic is keyed. Then as we believe, by luck, skill and a little perspiration, our intrepid duo make it to and land on the reef at Gardner both heaving a huge sigh of relief. Now all they have to do is call for help.....
Since running on only the right-hand engine just enough to charge the batteries would be less noisy, it could be easier to notice the dyanamotor isn't running when the mic is keyed. Or perhaps a post-landing once-over of the radio components prior to calling for help reveals a burned-out fuse. Maybe the missing receive antenna is noticed at this time as well! Either a spare fuse if they had one or scrap of heavy wire would take care of the need and the transmitter is back in operation. Signals are sent, Betty and others take notes, Pan Am says "look here"......but in this scenario it is too bad neither AE or FN receive the electrician-of-the-year award....
Thoughts? Cheers? Jeers? It would be nearly impossible to find "smoking gun" evidence but the basis of this scenario could be tested.
LTM,
Friend