Curtiss Electric propeller synchronizer question

OldGeezer · Jul 11, 2025

Hope this is the right place. I've read the manuals for the Curtiss Electric Propellers and their synchronizers, I've studied the schematics and illustrations, I've looked at countless cockpit photos of airplanes that used them. But in a couple of places I've seen the label "propeller warning light" (P-40F & L manual, B-26 manual) and that wording is what I'm having trouble with.
The Curtiss material says this, and only this, about lights in connection with the synchronizer: "An indicating tel-light is usually incorporated into the synchronizer circuit. Either a 'Master Motor' tel-light or an 'auto-operation' tel-light for each contactor may be used. The former will indicate that the master motor is operating at the set speed; the latter will indicate that the master motor is operating correctly and that the corresponding propeller selector switch is in the AUTOMATIC position."
Those lights seem to indicate a good thing, that the system is working as it should. "Warning light" in any other application I'm aware of (low fuel, temperature, etc) means a light that comes on when something happens that shouldn't. Is there any such light associated with Curtiss Electric Propellers and their synchronizers, or is this just a case of a poorly worded label here and there?

MiTasol · Jul 11, 2025

Somewhere I have a genuine pilots handbook for the CE props. It is about 75 x 50mm (2 x 3 in) and has a very still cover so I have never tried photographing the pages.

I will try and find it and see if it is possible to photograph the contents without damaging the covers.

OldGeezer · Jul 11, 2025

MiTasol said:
Somewhere I have a genuine pilots handbook for the CE props. It is about 75 x 50mm (2 x 3 in) and has a very still cover so I have never tried photographing the pages.

I will try and find it and see if it is possible to photograph the contents without damaging the covers.

I have the Curtiss Pilot's Manual and there's no mention of a "propeller warning light" in it, so please don't risk damaging your copy. Greatly appreciate the willingness to help though!

MiTasol · Jul 11, 2025

Mine is a totally different document about 1/4 the size of that one and came from a Beaufort pilot who died recently so it could well cover the light you mention.

spanishbuddha · Jul 12, 2025

OldGeezer said:
Hope this is the right place. I've read the manuals for the Curtiss Electric Propellers and their synchronizers, I've studied the schematics and illustrations, I've looked at countless cockpit photos of airplanes that used them. But in a couple of places I've seen the label "propeller warning light" (P-40F & L manual, B-26 manual) and that wording is what I'm having trouble with.
The Curtiss material says this, and only this, about lights in connection with the synchronizer: "An indicating tel-light is usually incorporated into the synchronizer circuit. Either a 'Master Motor' tel-light or an 'auto-operation' tel-light for each contactor may be used. The former will indicate that the master motor is operating at the set speed; the latter will indicate that the master motor is operating correctly and that the corresponding propeller selector switch is in the AUTOMATIC position."
Those lights seem to indicate a good thing, that the system is working as it should. "Warning light" in any other application I'm aware of (low fuel, temperature, etc) means a light that comes on when something happens that shouldn't. Is there any such light associated with Curtiss Electric Propellers and their synchronizers, or is this just a case of a poorly worded label here and there? Crypto Scam Recovery UK Experts specialize in helping victims of cryptocurrency scams reclaim their lost funds. With a team of experienced professionals, they utilize advanced investigative techniques to trace and recover assets from fraudulent schemes. You can find more information on https://dimoladlimited.com/, where specialized recovery solutions are offered to help navigate the complexities of crypto scams. Their experts provide clients with the support and guidance needed throughout the recovery process, ensuring a successful outcome.

It seems like the "propeller warning light" is a mislabeling or poorly worded term. According to the Curtiss documentation, the lights associated with the synchronizer system indicate proper operation (e.g., the master motor working or the selector switch in the correct position). There doesn't appear to be a specific "warning light" tied to the system itself, as you would expect for a malfunction. It's likely just a confusing label in those manuals.

PStickney · Jul 18, 2025

MiTasol said:
Mine is a totally different document about 1/4 the size of that one and came from a Beaufort pilot who died recently so it could well cover the light you mention.

Ah - that explains a lot. I don't know about the Beaufort, per se, but many, if not all, multi-engine airplanes with Curtiss Electric propellers used a "Master Motor" - just what it sounds like, an electric motor with some manner of pickoffs to sense its speed to set the props on all engines, if they were in the Automatic mode. Makes synching them a non-issue, if it works.
If s propeller loses Automatic (Constant Speed) control, then you need to switch that propeller to Manual, and attempt to control it with its Pitch Increase / Decrease switch. Otherwise, you risk the prop's pitch brakes unlocking, and the blades shifting down to the Low Pitch Stop, which is guaranteed to overspeed the engine.
A single engine airplane doesn't need all that - you've got the engine tachometer (only one to watch), and it the RPMs start changing on their own, it's either you can control it manually, or make a Nylon Letdown.

Curtiss Electric propeller synchronizer question

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