i live near IAD and have recently seen a few planes in the approach pattern with their landing lights (it looks like in the nose gear - they are too close together to be on the wings) in an alternating flashing pattern - like the lights on a school zone sign or school bus.

What is the significance of this? Its not all planes and since its at night I havent been able to determine the actual plane type or airline.

thanks

I believe WN use this functionality on their 737s.

It's exactly that - a school bus stop sign. The aircraft on short final is warning people to slow down and let it thru.

I've noticed the flashing landing lights on a lot of corporate jets, and I have also wondered about the significance. I don't know whether it's a discretionary design aspect or if it's meant to comply with a safety regulation unique to smaller jets. I'd seek a manufacturer or the NBAA for an answer.

Corporate aircraft and WN's 737s have the feature. The lights in the leading edge of the wing roots alternately flash.

I believe this feature was intended to be an 'anti-bird' item.....an attention-getter for birds if you will, that would cause them to ske-daddle out of the way.

Don't know that to be a fact, but was told that about seven years ago when I first saw it on the WN aircraft landing at MDW.

DRW

It's to make the airplane more noticeable, so serves an anti-collision function. A flashing light is noticed quicker than a steady light, especially when peripheral vision is involved. A side benefit is longer bulb life.

Jim

According to message on pprune, posted 8 years ago, 737s can be retrofitted with flashing landing lights, they are intended to scare birds. The theory was that birds are attracted to steady lights, so flashing them makes them less attractive.

Twenty years ago when PI was testing the system on a 727, the supplier of the mod touted it's anti-collision and bulb life benefits. It appears that research since then has shown possible bird strike benefits.

"The greatest benefit of the Pulselite system is found on commercial aircraft.In the air everyday, in all weather and conditions visibility is key to safety. Airlines that pulse their lights exhibit a lower occurrence of near miss events."

Jim

I don't understand how this could result in longer bulb life. Doesn't frequent power cycling have a negative impact on bulb life. Maybe I'm wrong and it's just one of those counter-intutive things. Or maybe the frequency of the power cycling is high enough so as to prevent the bulb from heating too much.

after seeing the reference to another message board. a simple google search turned up a lot of info - I just prefer to use the experts here.

It turns out it is for better visibility to others when on approach. When on "short approach" what I guess is what we non-pilots in the back call "final approach" the lights go solid.

Interestingly, on short approach the flashing lights are used to indicate to ground crew some problem and/or distress signal.


TEXD you surmised correctly; Longer bulb life is achieved for two reasons - one the filament doesnt get as hot and as for long as steady on thereby increasing life, and two, it doesnt have the stress of suddenly going from off to on (the bulbs are not turned all the way off in the flashing sequence).

CO related - I found a post from 1997 where the writer says he has a pilot friend for CO that has one 737 with the feature and that as far as he new, CO was the only mainline carrier to use the feature.

Last night on 1153 coming into DCA, we came out under some cloud cover and had what felt like a very steep angle of descent. It seemed like we were still very high given how close we were to the airport As we were in line with the Washington monument, we pulled back up and then circled back around. I don't know if we were close enough to landing to call this a go around or whatever the term of art is, but it was cool nonetheless. From the announcment the pilot made after we pulled back up, it sounded like ATC had cleared us to land but from a position where it wasn't feasible to do so. Second time around we landed fine, although I still think ATC made it harder for the pilot than it needed to be. My question is really just whether or not there are specific things in DCA that make it marginally more difficult to land there.

Yes, we would consider that a go-around. Anytime you abandon your approach profile or procedure, it is a go-around maneuver for us.

We have certain criteria that we've got to make during differing phases of the approach. That protects us from screaming in at the speed of heat, throwing the gear down, and leaving the engines at idle the entire approach (Not safe!!). We are required to be 'stabilized' on our approach by 1,000 feet above the touchdown zone (which we refer to as touchdown down elevation or TDZE). 'Stabilized' as we define it means having the aircraft in the landing configuration, making progress towards our final approach speed, and the engines at an approach power setting. Our final gate is at 500' above TDZE.

If we are not stabilized by those gates, we should perform a go-around and come back and try it again. Any pilot can call the go-around if he feels the criteria are not met. Generally what will happen to prevent that though will be an ID on your configuration/speed prior to that point and one of us will state 'You better start slowing it up', 'Get some gear out', etc. I'm willing to bet your pilots were left high by approach and decided it was going to be marginal getting that aircraft onto that gate in the proper configuration, so they executed the maneuver when it became apparent that continuing the approach would be fruitless.

There are many reasons for getting in that situation.....approach leaving you high and fast, tower asking you to maintain a higher speed to the final approach fix, getting dumped out of the weather on an abnormal vector and realizing 'I can't get there from here', etc.

Anyhow, better to go-around and do it again, than land fast, long and then go dribbling off the other end of the runway.

DRW

Don't know if this was already asked in this thread or not, but how much of a problem can strong surface winds be whilst landing?

Besides being a bit uncomfortable on the way down, is there anything dangerous about landing in windy conditions? And what types of aircraft are better suited to handle these conditions (if there's a difference at all)?

Thanks.

I was contemplating the best way to answer this question, and I kept getting hung up on the words 'problem' and 'dangerous'. I think the best way to answer a question on winds, would be to address strong crosswinds, which I would describe as 'challenging'.

Wind direction obviously impacts the work level on landing. Picture yourself trying to push a feather through a room and down onto a table......with a bit of wind, that task becomes a bit more challenging.

With a headwind, our relative speed over the ground is reduced, and our landing rollout will likewise be reduced.

With a tailwind, our speed over the ground is increased and our landing distance increased. We've got to analyze our landing weight (heavy/light?), runway condition (wet/dry/snow/ice?), runway length (construction?), and any other factors which will impact our ability to stop (reverser inop, etc.).

A strong crosswind (with gusts) is probably the most challenging. The aircraft is 'crabbed' into the wind to maintain a track down the extended centerline of the runway. The crab is maintained until just prior to touchdown, and the aircraft is aligned by the pilot with the runway centerline. This is accomplished by what what we call a 'wing down, top rudder' maneuver. As the aircraft is flared we lower the 'upwind' wing, and apply opposite rudder. If done correctly, this will bring the nose around to the centerline and keep the wings relatively level. The big challenge on all of that is touching down at the exact moment that both of the mains are perfectly aligned with the runway. If you are off at all....wheels not level, or not tracking down the centerline......you'll all feel it in the back. Picture yourself trying to pull into your garage with your nose not quite pointed where you want it, and your tires not pointed in that direction either.

On touchdown, we'll use the rudder to get over to that centerline, raise the control stick into the wind (which raises the aileron/spoiler and kills lift on that side - - keeping that wing from wanting to fly) and open the reversers.

Sounds rather busy, but after you do it one or two (hundred) times it becomes almost second nature. Still more of a challenge though than a 'calm' wind day.

Different planes have different characteristics.....

An interesting video to watch is the one on YouTube that shows the 777 crosswind landing flight testing. Type 'Crosswind landing testing' into the search and it should take you there.

DRW

Try this:

http://www.youtube.com/watch?v=itOj33YvLNo