Expert: D. Norkus - 6/1/2010

Question
QUESTION: I have a question about when it is required to have the aircraft anti-collision lights on.

According to FAR 91.209 "Aircraft Lights":

No person may:
(a) During the period from sunset to sunrise (or, in Alaska, during the period a prominent unlighted object cannot be seen from a distance of 3 statute miles or the sun is more than 6 degrees below the horizon)—

(1) Operate an aircraft unless it has lighted position lights;

(2) Park or move an aircraft in, or in dangerous proximity to, a night flight operations area of an airport unless the aircraft—

(i) Is clearly illuminated;

(ii) Has lighted position lights; or

(iii) is in an area that is marked by obstruction lights;

(3) Anchor an aircraft unless the aircraft—

(i) Has lighted anchor lights; or

(ii) Is in an area where anchor lights are not required on vessels; or

(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.


Section 91.209(a)(1) clearly requires use of navigation position lights at night.

Does 91.209(b) require use of the anti-collision lights at all times, day or night? If so, does this mean beacon and strobes (assuming the aircraft has strobes) or is one of those sufficient?

ANSWER: Steve

It does not. Since not all aircraft are equipped with white flashing strobe, but have red beacons the latter only is sufficient under 91.209(b) for "anti-collision" lighting. However, even if the aircraft is equipped with strobes, you don't have to use them during daylight hours (but do at night).  We do not operate flashing white strobes while taxiing except when entering or crossing runways, but as a cost saving measure my airline was asking the pilots to NOT use the strobes during daylight hours so they wouldn't have to replace them as fast. 91.209(b) gives the flexability to use only the nav and red beacon during daylight hours.

Hope that helps,
Dottie

---------- FOLLOW-UP ----------

QUESTION: Thanks!

I thought the FARs only required nav lights at night.

Do you use them duing the day because of company policy or because of the FARs?

ANSWER: Our nav lights are on any time there is power to the aircraft (even while at the gate) but F.A.R.s only require during civil twilight.

---------- FOLLOW-UP ----------

QUESTION: Thanks for clarifying the nav light issue.

Going back to anti-collision lights, do you know if a general aviation aircraft operating under part 91 is allowed to use stobes in lieu of the rotating beacon to satisfy FAR 91.209(b) when the aircraft is equipped with both?

Answer
Sec. 23.1401 - Anticollision light system.
(a) General. The airplane must have an anticollision light system that:
(1) Consists of one or more approved anticollision lights located so that their light will not impair the flight crewmembers' vision or detract from the conspicuity of the position lights...
(d) Color. Each anticollision light must be either aviation red or aviation white and must meet the applicable requirements of §23.1397.....

"The anticollision light should be turned on prior to engine start, even during daytime operations. At night, the position (navigation) lights should also be on." -from The FAA Airplane Flying Handbook

By strict interpretation of FAA texts, per F.A.R. 23.1401 strobes meet the definition of 'anticollision lighting' and thus per The Airplane Flying Handbook, should be turned on. However, since the red beacon is also an "anticollision light" per the 23.1401 definition it must also be turned on.

Therefore, no- you cannot use strobes alone in place of the red beacon.

However, as an example these definitions vary a bit from the F.A.R. 23.1401 definition and are what many pilots operate by-

Anti-Collision Beacon lights: Two beacon lights are fitted to aircraft near the center of the fuselage. One is located on top of the fuselage and the other on the bottom. These lights are colored reddish orange and rotate to produce a flashing effect. The beacons are turned on just before the engines are started and they remain active until the last engine is shut down. The beacons help to serve as a safety warning to ground personnel that the engines are operational.

Strobe Lights: High-intensity strobe lights that flash a white-colored light are located on each wingtip. Most smaller planes are only equipped with one of these strobes near the leading edge just behind the red or green navigation light. Larger airliners may be equipped with an additional strobe at the trailing edge as well. These flashing lights are very bright and intended to attract attention during flight. They are sometimes also used on the runway and during taxi to make the plane more conspicuous.

from http://www.aerospaceweb.org/question/electronics/q0263.shtml

The last statement regarding using strobes during taxi "to make the plane more conspicuous" is one that most pilots I know would never do, even though it is supported by 23.1401. At the airline level, we certainly do not run strobes while on taxiways and even hold off turning them on at night until lined up on the runway as they could impact the night vision of the crew holding short behind us on the taxiway.

Regards,
Dottie