737 NG landing lights

[Groundpounder]

I was flying on a SW 737-700, and noticed that when they extended those giant retractable landing lights from under the fueslage that there was quite an increase in wind noise. Are there speed restrictions on them, and what made Boeing go with a system like that?

 

[Stifler's Mom]

DELETED

 

[Ty Webb]

I was on a SW 737-700, and noticed that when they extended those giant retractable landing lights from under the fueslage that there was quite an increase in wind noise. Are there speed restrictions on them, and what made Boeing go with a system like that?

SWA uses those to decelerate from a high-speed taxi . . . cuts down on brake wear and it is not as noticeable from the tower as going into reverse.

Heh-heh. Couldn't resist.

Seriously, I don't extend them until cleared to land, and I doubt you'd notice the increase in sound over the gear and flaps hanging out already. Don't know what SWA's policy is, but it is the speedbrake on the NG that is really noticeable.

 

[Jim Smyth]

I think Boeing located them there for ease of changing out the bulb. Dont need a ladder and can safely stand on the ground.

 

[Groundpounder]

No, it was the lights making the noise. I was seated where I could see them reflected off the nacelle, and heard an increase in wind noise, and looked out and saw them rotating down. It wasn't really loud, and I'm sure the average pax wouldn't notice, but I'm a Super Nerd.

 

[Stby One]

We extend them when cleared for take off and retract when passing 10000 feet. I dont think there is any speed restriction, however many pilots keep them retracted above 250kt. We extend them again when cleared to land.

 

[aa73]

We extend them when cleared for take off and retract when passing 10000 feet. I dont think there is any speed restriction, however many pilots keep them retracted above 250kt. We extend them again when cleared to land.

Some airlines don't even use them at all.... because of slighlty higher fuel consumption, vibration and drag. Since they already have the inboard landing lights, the retractable ones are just for increased visibility.

AA's policy (as on the MD80, which has the wing retractable lights) leaves it up to Captain's discretion. Some use 'em, some don't.

73

 

[aa73]

Airbus 320s have the same landing lights.... whenever I'd ride on USAir, I always knew when we passed 10,000 on the descent because those things coming out were louder and vibrated more than some flap extensions!

73

 

[TriStar_drvr]

There is no speed restriction for the retractable landing lights. Above 300 knots or so, you will notice some vibration. I have them on below 10,000' because I want to be seen and believe you can never have too many lights on.

By the way, in the sim, in an idle power descent at 280 KIAS, extending those lights increased the rate of descent by 70 fpm.

 

[aa73]

There is no speed restriction for the retractable landing lights. Above 300 knots or so, you will notice some vibration. I have them on below 10,000' because I want to be seen and believe you can never have too many lights on.

By the way, in the sim, in an idle power descent at 280 KIAS, extending those lights increased the rate of descent by 70 fpm.

Can't argue with safety! You are doing the right thing.

Every airline flight dep't has a slightly different operating procedure. UAL and DAL, I've noticed, are quite dilligent in "Lights On." In other words, you will almost always see a DAL or UAL aircraft with EVERY light on, day or night, below 10.

AA is more of a "Captain's discretion" airline, especially on the 80.... I'd say about less than half of our captains use those wing landing lights during the day, and maybe about 75% use them at night. (There are still a few who only use the nose landing light at night, which basically means that until the gear comes out, they are totally dark.)

Lights On is a good program that should be standardized at every airline.

73

 

[TR4A]

SWA policy is retractable lights are extended when flaps are extended and are optional.

 

[venr122]

Is it true that they retract automatically during a V1 cut? (At least on the MD-80's i heard this)

 

[DCitrus9]

They auto retract on the 717 with an engine failure.
There is no speed restriction, but they start to make noise and rumble a bit above 200 knots.

 

[flx757]

Is it true that they retract automatically during a V1 cut? (At least on the MD-80's i heard this)

On the MD-80, the landing lights are on the same circuitry as the Second Segment Climb switch that looks for a 70psid between 13th stage augmentation valves when there is less than 1.3 cabin differential pressure, which equates to about 2500 feet. This is what the system uses to determine an engine failure (the 70 psi diff of the 13th stage bleeds) at low altitude (less than 1.3 cabin diff press), and will shut down both packs unless the Air Conditioning Shutoff Swith is in OVRD.

The landing lights auto retract system uses this same circuitry, and there is a weight penalty that must be applied to the max takeoff, climb and landing climb limit for each light that might be MEL'd in the exteded position.

(And Jeff, if you're out there...this time you might need to cut ME a break from the spankings, since I am home with no books to fall back on... )

 

[FL717]

On the MD-80, the landing lights are on the same circuitry as the Second Segment Climb switch that looks for a 70psid between 13th stage augmentation valves when there is less than 1.3 cabin differential pressure, which equates to about 2500 feet. This is what the system uses to determine an engine failure (the 70 psi diff of the 13th stage bleeds) at low altitude (less than 1.3 cabin diff press), and will shut down both packs unless the Air Conditioning Shutoff Swith is in OVRD.

Remind me to NEVER, EVER take an oral or a checkride after YOU Flx757!

I am really feelin' dumb right now. I knew about the auto retract system and even the MEL'd penalty...... but I always thought it was a cable pully system activated by hamsters in a spinning wheel.

That's my story and I'm sticking to it...