ComanchePilot
WHAT'S NEW
Our Mission
Development
Tribe Info
Classifieds
Tech Articles
Minutes
Advertisers
Links
NEWS FLASH
Member Info
BuiltByNOF

Comanche Idea Factory

WARNING LIGHT FOR GENERATOR INOPERATIVE

By

Omri Talmon

 

We all fear the partial or total loss of electric power in our aircraft. In many instances, such a situation starts with the failure of a generator or a voltage regulator. Deprived of fresh supply of electricity we then depend on what we have in the battery. This may be sufficient for a safe landing in the nearest airport. However, an early detection of the problem is essential.

The only electrical supervision instrument installed in many aircraft is the ammeter. Those originally supplied with the aircraft are not considered as trusty instruments of great precision. At any rate, a slow discharge is not always so easily detected. Some owners have added voltmeters but these instruments do not show the problem until quite late in the game. In a twin, both may not indicate the failure of one generator, as the second is sufficient to maintain the voltage and the current (originally, the Twin Comanches were delivered with one generator as standard, the second being offered as an option at extra cost).  Thus, the pilot may continue to fly for quite a time, and several flights, without knowing that one of his/her generators is inoperative.

In order to overcome these deficiencies I have installed, about twenty years ago, two warning lights, one for each generator. These lights will instantaneously go ON when the generator/voltage regulator system will not produce a voltage high enough to charge the battery. I used press to test lamps, and the wiring and installation is very simple and straightforward. Attached are the schematic and a photo of the panel showing the lamps. Appropriate in-line fuses for short circuit protection should be added as a function of the chosen components (omitted from the schematic for simplicity).

These lamps will go ON when the master switch is turned ON, and stay that way until the respective generator starts to feed the buss bar.

A fringe benefit: If before leaving the aircraft you notice the lamps are ON (how is it possible not to notice them?) it means you forgot to turn off the master switch.  This makes these lights a master switch warning system as well.

GenInop

Excerpt from Fig. 11-61 (Generator System), Piper Twin Comanche Service Manual (12/29/72). The additional wiring for the generator failure warning light is shown in bold lines. Only the left side is shown.  The right side is identical. Please note the voltage regulator terminals may differ from the schematic.

New-Panel2
The panel with the warning lights seen at the upper right corner.

Site Meter