Use of Navigation Lights during the day

6 Answers

1. 
   

   
   

   Kris Kortokrax on Nov 23, 2014

   91.209 tells you when you must use the position lights (Nav lights). There is no regulation giving a time when you must not use the lights.

   The AIM, in paragraph 4-3-23, discusses use of lights. It mentions “Operation Lights On”, which suggests turning on the landing light when within 10 miles of an airport (even during the day). It also mentions turning on Nav lights prior to taxi.

   If a CFI (or anyone else for that matter) tells anything, always ask for a reference so you can look it up and verify it for yourself. Otherwise, it is just an opinion.

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2. 
   

   
   

   Sans on Nov 23, 2014

   I agree with Kris,

   “….There is no regulation giving a time when you must NOT use the lights”.

   “..If anyone tells anything you doubt, always ask for a reference…” or post it in this very informative website.

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3. Best Answer
   
   

   
   

   John D Collins on Nov 23, 2014

   I would not use the Nav lights during the day. The regulations don’t require their installation or use during the day time. Anticollision lights are a different matter as they are required to be on at all times except “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”.

   There are several studies, by the FAA, the military, and the Australian Aviation Authority that clearly show that lights, including landing lights and anticollision lights are not effective during the day to aid with a pilot’s duty to visually see and avoid other aircraft. This has not affected the regulations or the AIM which ignore these studies. The next time you are at the airport during a VFR CAVU day, conduct the following experiment. Watch the aircraft on the landing approach. Note when you first spot the aircraft if you see any lights on. Next note when you can make out that lights of any kind are on. Draw your own conclusion. You still need to keep your anticollision lights on, regardless of the fact they don’t work, because it is required by regulation. However, the other lights are up to you.

   A few observations on lights during the day. During WWII, the navy experimented with reducing the visibility of aircraft as they approached submarines by placing lights along the leading edge of the aircraft to hide them. Google Yahudi project stealth.

   The eye uses the rods to detect motion. As little as a single rod can detect the contrast between the bright sky and an aircraft. By lighting up the aircraft, this reduces the contrast against the bright sky and delays visual acquisition of the aircraft.

   Here is a study conducted by Australia if you are interested. https://dl.dropboxusercontent.com/u/58910037/limit_see_avoid.pdf

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4. 
   

   
   

   Kris Kortokrax on Nov 23, 2014

   Interesting reading John,

   The Yahudi (Yehudi) project required concentrating lights along the leading edges directed towards the observer to get the required effect.

   I don’t see anything suggesting that turning on strobes or position lights might in any way hinder the ability to discern an aircraft.

   The only real drawback I can imagine would be if I were conducting takeoffs and landings with the lights lit. The jarring during landing (at least my landings) might cause the filaments to fail prematurely. However with the advent of LED lights, that should not be a problem.

   I’ll continue to light myself up as much as I can, especially when flying something with a small profile like a Robinson R-22.

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5. 
   

   
   

   John D Collins on Nov 24, 2014

   When I operated a flight school using primarily C152 and C172 trainers, following the FAA guidance, pilots would have the landing lights on all the time during the day. Landing lights would rarely go 20 hours and represented a major reason for maintenance and operating costs. IIRC, the lights were about $25 each and took at least a half hour of labor to get replaced. They weren’t always checked on preflight during the day, but at night, the flight had to be cancelled if they were inop. So leaving the lights on would cause several cancelled flights over the period of 100 hours and if the lights were replaced 4 times during that period, would represent an operating costs of a few hundred dollars. This had to be reflected in the rental rates. The high cost is what got me interested in the subject and standing outside watching the aircraft in the pattern, I could never determine if the lights were on until the aircraft was on very short final. Of course this applies only to daytime and when the sky was clear. Towards dusk or on a cloudy overcast day, the lights were clearly visible.

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6. 
   

   
   

   Gary S. on Jan 26, 2015

   Navigation or anti-collision lights may go unseen at night over a big city with a lot of ground light-clutter. But…I feel better with them on and hopefully I’ll be with Approach or Departure as well.

   For those looking for recommended guidance as to using your aircraft exterior lights, here it is:

   Rotating Beacon(s) ON:
   Before engine/powerplant start

   Position Lights ON:
   After engine/powerplant start, and before taxi

   Taxi Light (if equipped)
   ON: when taxiing day or night
   OFF: When stopped, and when signaling other taxiing acft you are yielding to them

   Strobe Lights (if equipped)
   ON: during day
   OFF: during night taxi if blinding other aircraft

   All the above lights (except landing light) “ON” before taxiing onto runway for departure or before receiving “Line Up And Wait”

   Landing Light ON:
   When “Cleared For Takeoff” or upon beginning takeoff roll
   When below 10,000 ft
   When within 10 miles of destination
   In conditions of reduced visibility unless it reduces pilot’s vision
   In areas where birds may be present…waterway’s, landfills, etc.

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