I just noticed that my right wingtip strobe is inoperative. Is the beacon sufficient to satisfy the anti-collision light requirement for night (or daytime) flight?
Since my Grumman was certificated in 1976, does this mean I don't need anti-collision lights for day VFR, even if installed? And if they are installed, but either rotating beacon, and/or a strobe light is inop?
As for the first question, if they're installed (required or not) and operable, you have to operate them even in Day VFR conditions unless per last sentence in the regulation that would compromise safety (like flying in a cloud, where the flashing could cause vertigo):
§91.209 Aircraft lights.
No person may:
(b) Operate an aircraft that is equipped with an anticollision light system, unless it has lighted anticollision lights. However, the anticollision lights need not be lighted when the pilot-in-command determines that, because of operating conditions, it would be in the interest of safety to turn the lights off.
However, anti-collision lights were not required for Day VFR operations when your Grumman was built in 1976. See the last paragraph on page 2 of the Chief Counsel letter cited above. The flashing beacon wasn't even part of the Standard equipment for Grummans that year (A-item in the equipment list, not R, S, or O). Therefore, if you have one anti-collision light out on your 1976 Grumman Tiger/Cheetah/Yankee, you can operate the aircraft from sunrise to sunset if you comply with 91.213(d) by deactivating and placarding that system -- including a maintenance record entry if "maintenance" was performed to deactivate it. Once that's done, your aircraft "is considered to be in a properly altered condition acceptable to the Administrator" and for operational purposes, it's as though it had no anti-collision lighting system at all.