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wxman11
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SQ Navigation Lights Off

Fri Feb 20, 2015 7:41 am

Hi folks,

Just curious and perhaps I already know the answer to this but lately I've been noticing here at SFO that the SQ flight has been taxiing without the navigation lights on as seen in the photo. Has anyone seen this and why is SQ doing that?

brgds

 
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Starlionblue
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RE: SQ Navigation Lights Off

Fri Feb 20, 2015 8:21 am

Quoting wxman11 (Thread starter):
Just curious and perhaps I already know the answer to this but lately I've been noticing here at SFO that the SQ flight has been taxiing without the navigation lights on as seen in the photo. Has anyone seen this and why is SQ doing that?

I only know for general aviation but in the small stuff only the beacon is required. If the beacon is inop, or the plane does not have a beacon, the strobes can be used instead. Navigation lights are only required at night.

No idea if the rules are different for the big iron.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
mmo
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RE: SQ Navigation Lights Off

Fri Feb 20, 2015 9:28 am

Quoting wxman11 (Thread starter):
why is SQ doing that?

SQ's SOPs are written so the nav lights are off during the day. They are the only carrier I've ever worked for that adopted that policy, but it's their toys and they can do what they want. The justification is there are less light bulb changes due to the lower operating time.
If we weren't all crazy we'd all go insane!
 
AIRWALK
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RE: SQ Navigation Lights Off

Fri Feb 20, 2015 10:24 am

There are no requirements per ICAO that require nav lights to be on during daytime ops. It is at the PIC or airlines discretion.
I'm sure this thread will take off soon
 
KELPkid
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RE: SQ Navigation Lights Off

Fri Feb 20, 2015 9:38 pm

Quoting AIRWALK (Reply 3):
There are no requirements per ICAO that require nav lights to be on during daytime ops. It is at the PIC or airlines discretion.

There didn't used to be any daytime lighting requirements in the USA when I first started flying, but I believe the anticollision beacon is required at all times now (if the aircraft is so equipped).

Here's the relevant reg:
§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.

Basically, you get to turn the strobes off in the clouds to keep from getting flash blinded or mesmerized. It is also considered bad practice to have strobes on on the ground (until you take the runway) because they can flash blind other flight crews who might be taxiing with you  

The only reason I can think of to turn the nav lights off in the daytime is to preserve the bulbs. However, with LED lighting on newer aircraft, this now appears to be irrelevant.

I'm wondering if the nav light switch and the anticollision switch are tied into each other in a modern airliner (e.g. turning on nav lights also turns on the beacon). That would seem to make sense to me  
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barney captain
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RE: SQ Navigation Lights Off

Fri Feb 20, 2015 11:42 pm

Quoting mmo (Reply 2):
SQ's SOPs are written so the nav lights are off during the day. They are the only carrier I've ever worked for that adopted that policy, but it's their toys and they can do what they want. The justification is there are less light bulb changes due to the lower operating time.

WN did the same thing for many years. We would turn them on to check them for the pre-flight in the AM then off. And again for the PM crew pre-flight in the afternoon, then off. Then again when it got dark. Then the light bulb went off   The additional cycles on the bulbs were actually causing them to fail sooner. When do bulbs usually fail? When you turn them on. Leaving them on seemed more logical.

Interesting side note, we still turn the NAV lights off when we park the a/c for the night. I see most operators of the 737 leave them on. We were told that the clear lens were overheating during the night - but I find it odd that no other carriers seem to have this issue.
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glen
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RE: SQ Navigation Lights Off

Sat Feb 21, 2015 11:13 am

Quoting KELPkid (Reply 4):
I'm wondering if the nav light switch and the anticollision switch are tied into each other in a modern airliner (e.g. turning on nav lights also turns on the beacon). That would seem to make sense to me

No, they are not. And it wouldn't make sense either. We - and I assume most operators - want to have the NAV-lights ON not only for ground operation (movement) but also while other processes are going on around the aircraft (i.e. loading, fueling etc.) for better visibility.
The beacon on the other side is to signalise ground operation of the aircraft (moving, running engines).
So you don't want to have these lights tied together.
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wxman11
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RE: SQ Navigation Lights Off

Sun Feb 22, 2015 5:41 am

Am I to presume that the nav-lights are off during cruise in daytime? Next time, I'm going to see once SQ is airborne to verify if nav-lights are off or on. Perhaps its only for ground movement. Its just the first time I seen that. I haven't seen other carriers, foreign or domestic, do that.
 
mmo
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RE: SQ Navigation Lights Off

Sun Feb 22, 2015 8:13 am

Quoting wxman11 (Reply 7):
Am I to presume that the nav-lights are off during cruise in daytime?

As I wrote previously, SQ's SOPs are written so the nav lights are off during the day. There is no legal requirement to have them on. In theory, you should not be on. However, there are pilots who elect to turn them on. But the "book" answer is they will be off.
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Tristarsteve
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RE: SQ Navigation Lights Off

Sun Feb 22, 2015 11:28 am

Quoting wxman11 (Reply 7):
I haven't seen other carriers, foreign or domestic, do that.

Well BA has no rule that I know of, but in daylight about half the aircraft have the lights off.
When I leave the aircraft at night I always turn the nav lights off, and there is no requirement for the crew to check them in the morning (it is part of the daily check for maint), so usually they leave here with them off.
 
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DocLightning
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RE: SQ Navigation Lights Off

Sun Feb 22, 2015 5:51 pm

Quoting KELPkid (Reply 4):
The only reason I can think of to turn the nav lights off in the daytime is to preserve the bulbs. However, with LED lighting on newer aircraft, this now appears to be irrelevant.

Granted, LEDs age with time in operation (they can be turned on and off rapidly with no penalty to the LED itself, although you might wear out the circuitry if it isn't designed for it).

But the cost of replacing LED bulbs is trivial with respect to an even small risk taken that a crew might forget to turn on their nav lights at dusk and thus lead to an accident.
-Doc Lightning-

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skyhawkmatthew
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RE: SQ Navigation Lights Off

Sun Feb 22, 2015 9:56 pm

During the day the nav lights aren't bright enough to make a difference to visibility anyway.

Common SOP is that they must be on in low visibility and at night; at other times it's at the crew's discretion.
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mmo
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RE: SQ Navigation Lights Off

Sun Feb 22, 2015 9:56 pm

Quoting DocLightning (Reply 10):
But the cost of replacing LED bulbs is trivial with respect to an even small risk taken that a crew might forget to turn on their nav lights at dusk and thus lead to an accident

But, the beacon(s) and strobes will be on so there would be a minimum, if any, risk of a collision.
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KELPkid
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RE: SQ Navigation Lights Off

Tue Feb 24, 2015 1:39 am

Quoting skyhawkmatthew (Reply 11):
During the day the nav lights aren't bright enough to make a difference to visibility anyway.

That's not their purpose. It is to help an aircraft at the same altitude determine the direction of travel of another aircraft.

Quoting barney captain (Reply 5):

WN did the same thing for many years. We would turn them on to check them for the pre-flight in the AM then off. And again for the PM crew pre-flight in the afternoon, then off. Then again when it got dark. Then the light bulb went off The additional cycles on the bulbs were actually causing them to fail sooner. When do bulbs usually fail? When you turn them on. Leaving them on seemed more logical.

Don't airliners usually have dual bulbs for most required exterior lights? Some L-1011 operators even went a step further and equipped their aircraft with dual rotating beacons (one above the fuselage, one below on the belly...)
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skyhawkmatthew
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RE: SQ Navigation Lights Off

Tue Feb 24, 2015 3:19 am

Quoting KELPkid (Reply 13):
That's not their purpose. It is to help an aircraft at the same altitude determine the direction of travel of another aircraft.

I'm aware of that – but in broad daylight you won't be able to discern the nav lights until you are more than close enough to simply see which way it is pointing.
Qantas - The Spirit of Australia.
 
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DocLightning
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RE: SQ Navigation Lights Off

Sun Mar 01, 2015 11:08 pm

Quoting barney captain (Reply 5):
When do bulbs usually fail? When you turn them on. Leaving them on seemed more logical.

For incandescents and gas vapor lamps, that is absolutely true. They age more with on/off cycling than they do with time in operation.

For LEDs of the sort used on the 787, they age more with time in operation than they do with on/off cycling. In fact, some household LEDs cycle on/off at 20-30Hz for whatever reason.
-Doc Lightning-

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musang
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RE: SQ Navigation Lights Off

Mon Mar 02, 2015 8:31 am

Quoting KELPkid (Reply 4):
I'm wondering if the nav light switch and the anticollision switch are tied into each other in a modern airliner (e.g. turning on nav lights also turns on the beacon)

Not in any machine I've ever been in.

Quoting barney captain (Reply 5):
we still turn the NAV lights off when we park the a/c for the night. I see most operators of the 737 leave them on.

My preference is to leave them on for self defense against careless catering trucks!

Quoting KELPkid (Reply 13):
Don't airliners usually have dual bulbs for most required exterior lights? Some L-1011 operators even went a step further and equipped their aircraft with dual rotating beacons (one above the fuselage, one below on the belly...)

As far as I'm aware dual bulbs is an optional extra on Boeings. We once had a few 737s with the feature. I believe it was standard on the TriStar, not an option. Purpose was despatch reliability.

I agree that nav lights are pointless during the day. If you've noticed that they're not on, you've already seen the aircraft! I believe that although airlines' SOPs may not require them in daylight, the UK CAA recommends (not mandates) that they be on all the time. Many pilots switch them on all the time for this reason, and also so thay don't forget to switch them on when it gets dark.

Regards - musang
 
KELPkid
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RE: SQ Navigation Lights Off

Mon Mar 02, 2015 9:22 pm

Quoting DocLightning (Reply 15):
For LEDs of the sort used on the 787, they age more with time in operation than they do with on/off cycling. In fact, some household LEDs cycle on/off at 20-30Hz for whatever reason.

Poor rectifier design/cheaper to manufacture  (in these designs, the LED is used as the bridge diode in the rectifier)

Higher quality LED household lighting usually has a miniature solid state power supply that converts household current into the proper voltage that the LEDs need.
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