Parsing the Regs

The previous post discussed the "inop" status of the beacon that sits atop N631S's vertical stabilizer. In summary, (a) as of Friday morning it was not working at all; (b) the maintenance folks were on the case; and (c) I believed it to be a "no-go" item that would need to be fixed if I wanted to make my weekly trip from Connecticut to the DC area by airplane rather than AmTrak.

Well, perhaps not so much.

Midday Friday I went over to Three Wing Flying Services and talked with Tony and Jared. Tony had the bad news: "We found a short, and your lamp is shot...and we don't have a 14 volt lamp in stock." Jared offered the good news: "You've got strobes, right? As long as you have strobes, you don't need the beacon."

Really? I needed to think about this a bit. This was one of those times when it would be necessary to see what the regulations said, and to consider what the regulations mean!

The applicable regulation is found in Title 14 CFR Part 91 Subpart C (Equipment, Instrument, and Certificate Requirements) Section 91.209 (Aircraft lights), which says in relevant part:

No person may:...(b) Operate an aircraft that is equipped with an anticollision light system, unless it has lighted anticollision lights. ...

N631S is in fact "equipped with an anticollision light system", so that part of 91.209 is applicable. In normal circumstances, that system is comprised of the red flashing beacon atop the vertical stabilizer and the white wingtip strobes. If the beacon is "inop" but the strobes are working just fine, then the aircraft complies with the requirement that it "ha(ve) anticollision lights" when being operated. So far, so good.

Here's an excerpt from an on-line forum called TheCFI.com that shows at least one other person using the same logic to arrive at the same conclusion:

Beacon/Rotating Beacon vs Anti-Collision Lights
by jdkiger » Tue Aug 19, 2008 10:02 am

A recent discussion at my flight school resulted in very different opinions in understanding of what is required. Not quite addressed in past questions on this forum. Our situation is: Aircraft has wing tip strobes/anti-collision lights in addition to a vertical stabilizer mounted aviation red/white strobe (individual power supplies). With the strobe out on the vertical stabillizer inop, placarded as such. Required log book entries documented. Is the aircraft airworthy? Many suggest that since the wing tip strobe/anti-collision lights are operating the aircraft meets the requirements to be airworthy. How about it?

jdkiger

by midlifeflyer » Mon Aug 25, 2008 7:50 am

This is pure guesswork on my part since I've never seen anything from the FAA on it...

91.209(b) says "an" anticollision light system (so do the applicable provisions of 91.205). If the aircraft has two different ones that each comply with TSO C96a (and whatever other requirements there might be), one should be sufficient for compliance with 91.209(b).

That is, of course, assuming that the other requirements of 91.213 regarding flight with inoperative equipment are met.

Like I said, pure guesswork.

Finally, I recall that the previous airplane in my life, N82953, a 1981 Piper Archer II, came from the factory with wingtip strobes and no rotating beacon. And it was just fine in that configuration. So in the end, I concluded that N631S was indeed airworthy with the beacon placarded "inop" (as required by 91.213) and the strobes fulfilling the requirement of Section 91.209 for operating anticollision lights. I could make my flight to DC without transgressing the bounds of the regulations.

Three Wing is ordering the parts needed to restore N631S's beacon to operating status, which work will be done during the coming week.

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