If I were to replace my left nav light with a SkyBeacon ADS-B + strobe, could I remove the rotating beacon at the top of the tail?
As required equipment for night flight, that’s technically feasible to do as this can serve as an anti collision light, provided the aircraft still has position lights and landing lights. However, if you’re flying a certified aircraft, unless you have an STC to deactivate the beacon, you cannot as it’s listed in the minimum equipment list for the aircraft. You’d be opening a can of worms to do so and there really seems to be no significant advantage in doing so.
The uAvionix SkyBeacon replaces the left nav (and strobe, if present) light; the optional companion uAvionix SkyLight replaces the right nav (and strobe, if present) light. Together, they would provide 360° strobe and thus qualify as an anti-collision light system, making a rotating beacon technically unnecessary.
However, even if removing the beacon is legal, first consider whether it's a good idea. Without a beacon, you would have to run the strobes continuously, i.e. during the day and even on the ground, not just in the air at night. Running strobes on the ground is a distraction or even blinding to other pilots and therefore not consistent with safety. While that may be an acceptable (to the FAA, at least) compromise for planes that never had a beacon, to avoid grounding much of the GA fleet until they pay to have one installed, IMHO it is not reasonable to deliberately remove a beacon to take advantage of that loophole.
TL;DR: Keep the beacon.
91.205 parts (b) and (c), excerpted below, require a position light. I believe it is a position light and it is needed. Call the FSDO office in your area and confirm. If they say Strobes, which pilots often turn off on the ground while taxiing to avoid blinding others, while the beacon light is on all the time as a reminder that an engine is running, can replace the beacon, than go for it. Get it in writing to satisfy the A/P that will sign off the removal in your aircraft maintenance logs.
91.205 Powered civil aircraft with standard category U.S. airworthiness certificates: Instrument and equipment requirements. (a) General. Except as provided in paragraphs (c)(3) and (e) of this section, no person may operate a powered civil aircraft with a standard category U.S. airworthiness certificate in any operation described in paragraphs (b) through (f) of this section unless that aircraft contains the instruments and equipment specified in those paragraphs (or FAA-approved equivalents) for that type of operation, and those instruments and items of equipment are in operable condition.
(b) Visual-flight rules (day). For VFR flight during the day, the following instruments and equipment are required:
(1) Airspeed indicator.
(3) Magnetic direction indicator.
(4) Tachometer for each engine.
(5) Oil pressure gauge for each engine using pressure system.
(6) Temperature gauge for each liquid-cooled engine.
(7) Oil temperature gauge for each air-cooled engine.
(8) Manifold pressure gauge for each altitude engine.
(9) Fuel gauge indicating the quantity of fuel in each tank.
(10) Landing gear position indicator, if the aircraft has a retractable landing gear.
(11) For small civil airplanes certificated after March 11, 1996, in accordance with part 23 of this chapter, an approved aviation red or aviation white anticollision light system. In the event of failure of any light of the anticollision light system, operation of the aircraft may continue to a location where repairs or replacement can be made.
: : :
(c) Visual flight rules (night). For VFR flight at night, the following instruments and equipment are required:
(1) Instruments and equipment specified in paragraph (b) of this section.
(2) Approved position lights.
(3) An approved aviation red or aviation white anticollision light system on all U.S.-registered civil aircraft. Anticollision light systems initially installed after August 11, 1971, on aircraft for which a type certificate was issued or applied for before August 11, 1971, must at least meet the anticollision light standards of part 23, 25, 27, or 29 of this chapter, as applicable, that were in effect on August 10, 1971, except that the color may be either aviation red or aviation white. In the event of failure of any light of the anticollision light system, operations with the aircraft may be continued to a stop where repairs or replacement can be made.
(4) If the aircraft is operated for hire, one electric landing light.
(5) An adequate source of electrical energy for all installed electrical and radio equipment.
(6) One spare set of fuses, or three spare fuses of each kind required, that are accessible to the pilot in flight.