SuseJ772
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Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 6:06 am

Is this a problem? It seems to happen quite "frequently." Does it compromise the structural integrity of the airport or the plane? Also, it seems more often than not, it is a 747 landing short. Do 747 pilots into SXM purposely land short due to a shorter runway?


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KELPkid
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 6:13 am

Quite illegal...a touchdown before the threshhold!

You might be able to get away with this in a light plane (even though it would be very poor practice), but in a 744, you might stand in danger of cracking the pavement, if not picking up sunbathers with your wake, or hitting the fence (the pavement might not be properly re-enforced in the overrun area).

Anyone know if there's a VASI at SXM? Wonder if it was out of service on this day?
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n8076u
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 6:21 am

I wonder if a beachgoer could have reached up and touched a tire?  Wink

By landing as early as possible, especially at an airport like SXM, where the runway isn't all that long, you maximize how much room you will have to stop or to go-around, especially if there are obstacles that have to be cleared at the other end, like a mountain, like at this particular airport. That area should be paved the same as the rest of the runway, so no problems strucurally, as far as the airport or aircraft are concerned. Landing "on the numbers" there means at least a couple hundred feet of lost "cushion".

Chris
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SlamClick
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 6:23 am

Sorry, my Jepps are buried and I can't tell you for sure but I think I recall a VASI or PAPI there.

I'm not sure that he did touch down short of the actual runway but it is clearly short of the aiming markers. If this was a US-flagged airliner the FAA might be using these photographs to start an investigation.

Check out his wake in the second photo! Holy crap! It is blowing sand and spray all over.

I believe he'd just had a little sinker and he motored over Maho Beach nose-high and at something just under go-around thrust trying to arrest it.
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SuseJ772
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 6:31 am

Quoting SlamClick (Reply 3):
I believe he'd just had a little sinker and he motored over Maho Beach nose-high and at something just under go-around thrust trying to arrest it.

That would be so awesome to see. How common is that in your landings
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SlamClick
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 8:52 am

Quoting SuseJ772 (Reply 4):
How common is that in your landings

Common enough. The whole point is to catch them more or less instaneously. A little thrust now is better than "radar-power" later.

Quoting N8076U (Reply 2):
By landing as early as possible, especially at an airport like SXM, where the runway isn't all that long, you maximize how much room you will have to stop or to go-around

If an electronic or visual glideslope is available you MAY NOT descend below it. This landing is NOT good flying, it is bad flying. It is not safer, it is more dangerous. He is about ten feet from killing some people. He should have been about fifty feet at the fence.

If you actually need the extra thousand feet of concrete you should not be operating into this airport with that equipment at all and to do so would be deemed bad judgement by the FAA or other regulating bodies.

There is this myth about SXM that you need to drop it on the first brick of the runway. It is just not so. There are many airports just as unforgiving as SXM around the world, they are just not quite so photogenic.
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bri2k1
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 9:10 am

Quoting SlamClick (Reply 5):
If an electronic or visual glideslope is available you MAY NOT descend below it

I won't dig out the FARs, but I thought the actual regulation was that you may not descend below it until it is necessary to make a safe landing.

The displaced threshold (with the white arrows) may be used for taxi and takeoff but not landing. The area with yellow chevrons is just a blastpad/overrun and may not be used for any normal operation. Still,
the target touchdown zone is usually not right at the threshold.

In the first photo, I don't think the wheels are down. There could be ground effect, so maybe he just nails the threshold, which would be legal. The second one looks like at least a few wheels are on terra firma before the threshold which is not legal, at least not under the FARs.

Quoting SlamClick (Reply 5):

If you actually need the extra thousand feet of concrete you should not be operating into this airport with that equipment at all and to do so would be deemed bad judgement by the FAA or other regulating bodies.

Amen.
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vikkyvik
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 10:07 am

Quoting SlamClick (Reply 3):
Check out his wake in the second photo! Holy crap! It is blowing sand and spray all over.

Seriously! Would you say that's jetwash, vortices, or other?

Quoting N8076U (Reply 2):
That area should be paved the same as the rest of the runway, so no problems strucurally, as far as the airport or aircraft are concerned.

I don't believe overruns/blastpads have to be able to take the weight of an airplane landing. I could be wrong though.

Quoting Bri2k1 (Reply 6):
Still, the target touchdown zone is usually not right at the threshold.

In the case of SXM, it's 1000' down the runway:


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There's your PAPI, also (on both sides of the runway - is one angled?)

Quoting SlamClick (Reply 5):
There is this myth about SXM that you need to drop it on the first brick of the runway. It is just not so. There are many airports just as unforgiving as SXM around the world, they are just not quite so photogenic.

If I remember correctly, SXM's runway is on the order of 7900' long. For comparison, runway 9/27 at BOS is 7000' long, and it sees 747 landings with no problem:


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Starlionblue
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 10:14 am

Quoting Vikkyvik (Reply 7):
If I remember correctly, SXM's runway is on the order of 7900' long. For comparison, runway 9/27 at BOS is 7000' long, and it sees 747 landings with no problem:

I won't pretend to know the intricacies, but would the hills beyond the far end of the SXM runway artificially restrict landing length? Considering go around options and such.
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vikkyvik
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 11:08 am

Quoting Starlionblue (Reply 8):
I won't pretend to know the intricacies, but would the hills beyond the far end of the SXM runway artificially restrict landing length? Considering go around options and such.

You may have a point - I also won't pretend to know the intricacies. However, I would think that airplanes would be required to be able to climb out in the case of a go-around and maintain obstacle clearance. I would also guess that a go-around could potentially be initiated as far down the runway as the last touchdown marker (~3000').

On your typical go-around, you'll already have considerable speed. From what I've heard, airplanes are capable of pretty damn powerful climbs in go-around scenarios (considering that you'll be at a landing weight in general).

As usual, please correct any incorrect assumptions I may have made.

~Vik
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n8076u
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 11:15 am

Okay, I stand corrected then, on all counts.  white 

Quoting Bri2k1 (Reply 6):
In the first photo, I don't think the wheels are down. There could be ground effect, so maybe he just nails the threshold, which would be legal. The second one looks like at least a few wheels are on terra firma before the threshold which is not legal, at least not under the FARs.

I agree, the aircraft in the first photo isn't on the ground yet and is higher than it seems, as the angle from which it was photographed is deceiving, as is a lack of well-defined shadows from the gear. The second may just be tickling the ground with the left side. The one in the first photo may have actually touched the ground farther down than the one in the second photo.

Quoting Vikkyvik (Reply 7):
I don't believe overruns/blastpads have to be able to take the weight of an airplane landing.

Actually, I think you're right. I mistook the yellow chevron area for the displaced threshold, rather than an overrun area. No, I'm not a pilot.  Wink

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SlamClick
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 11:15 am

Quoting Bri2k1 (Reply 6):
you may not descend below it until it is necessary to make a safe landing.

In no case do you dive for the concrete. The whole idea is a stabilized angle of descent all the way to touchdown. The 'standard' is about 3 degrees or one foot down in twenty feet forward. So if the aiming markers are a thousand feet down the runway you cross the near end of it at fifty feet.

Now look at the picture:

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Note the Precision Approach Path Indicator (PAPI) on both sides of the runway. There is a row of four white lights on each side pretty much abeam the far end of the aiming markers. Those guide your eyeball height until about the time you start the landing flare. This should put your wheels on the ground within the aiming markers which are the big wide rectangles of white paint on either side of the centerline markings. That gives you roughly six thousand nine hundred feet to brake to a stop.

You don't want to squander runway here, but as has been suggested, there are worse runways around. Burbank, maybe LaGuardia and Midway are, in my opinion, more critical than this one.

Quoting Starlionblue (Reply 8):
I won't pretend to know the intricacies, but would the hills beyond the far end of the SXM runway artificially restrict landing length? Considering go around options and such.

They do indeed become a factor, more on takeoff (at takeoff weights) than for go-around (at lighter landing weights)

The telephoto used in this shot forshortens the distance quite a bit, but the mountains do sit across the east end like a row of shark teeth. On takeoff (missed approach too IIRC) you make a turn to the right, south, through a gap just beyond the right side frameline. It looks dramatic in a large airplane and the turn does indeed degrade climb performance, but once headed for the mile-wide gap you are headed out to sea and don't need to climb until you approach the next island in the Antilles. (St. Kitts is the next one I remember)

I flew 757, maybe 767 in here, plus Airbus. It was memorable but mostly for scenery and not for any drama regarding the airport and its procedures and challenges.
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bri2k1
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 11:28 am

Quoting SlamClick (Reply 11):
In no case do you dive for the concrete.

That's true, of course. How do you think the cockpit height of the 747 contributes to this approach being low? I suppose a seasoned 747 pilot could just plan to fly the approach a little higher than indicated, but it's possible that his/her eyes are right on the glideslope in those photos, isn't it? I've only flown a 747 simulator at UA in DEN, not the real deal...but I was told that at rotation, the pilot is 30+ feet higher than the passengers in the last row when the main gear leave the runway.
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SlamClick
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RE: Is This A Problem (SXM Landing Situation)

Fri Jul 21, 2006 11:50 pm

Quoting Bri2k1 (Reply 12):
That's true, of course. How do you think the cockpit height of the 747 contributes to this approach being low?

The system is positioned specifically for airliners. Smaller planes end up landing longer than they might want if they follow it all the way down. I flew the 767 in there and can guarantee you that I was not this low.
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davestanKSAN
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RE: Is This A Problem (SXM Landing Situation)

Sat Jul 22, 2006 7:44 am

Interesting topic. Thanks for all your insight SlamClick and everyone. Does anyone know the max weight allowance for the overrun area vs. the displaced threshold at SXM? Thanks in advance...

Cheers,
Dave
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3DPlanes
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RE: Is This A Problem (SXM Landing Situation)

Sat Jul 22, 2006 7:53 am

Quoting N8076U (Reply 10):
the aircraft in the first photo isn't on the ground yet and is higher than it seems

Everybody is talking as though these are different landings. From the date on the photos, and the guy crouching by the fence, I'd wager they're the same landing - maybe a few milliseconds apart...

Also, I seem to recall reading somewhere (here?) about an Air France (?) plane landing so low the main gear took out fence and drug a section of it down the runway. Could be an urban legend, though.

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bri2k1
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RE: Is This A Problem (SXM Landing Situation)

Sat Jul 22, 2006 7:59 am

Quoting DavestanKSAN (Reply 14):
Does anyone know the max weight allowance for the overrun area vs. the displaced threshold at SXM?

I don't have the numbers for max runway weights at SXM. However, as I mentioned above, any displaced threshold is intended to be used for the design runway weights (accounting for the per-axle limitations) for taxi and takeoff but not landing, and the blast pad/overrun area is not intended to be used by aircraft.
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davestanKSAN
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RE: Is This A Problem (SXM Landing Situation)

Sat Jul 22, 2006 8:15 am

Quoting Bri2k1 (Reply 16):
I don't have the numbers for max runway weights at SXM. However, as I mentioned above, any displaced threshold is intended to be used for the design runway weights (accounting for the per-axle limitations) for taxi and takeoff but not landing, and the blast pad/overrun area is not intended to be used by aircraft.

Ahh Thanks! I wasn't sure if the displaced threshold was used for the design runway weights for landing. Appreciate the information  

Cheers,
Dave

[Edited 2006-07-22 01:17:01]
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flymatt2bermud
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RE: Is This A Problem (SXM Landing Situation)

Sat Jul 22, 2006 8:23 am

Quoting Vikkyvik (Reply 9):
please correct any incorrect assumptions I may have made.

The runway at SXM does not 'artificially' restrict the landing field length available. However, consider these 744's must have fuel reserves to the next suitable runway plus. So they aren't coming in at minimum fuel. SXM is one of those places that is visually intimidating. As is stated above the missed approach and departure procedures require an immediate right hand turn to avoid the terrain at the end of the runway. Some local air carriers with the turboprops regularly make a left hand turn out, again as previously mentioned, the visual perception is much closer than it looks.

Other than a fence incident a while back you really don't hear of many situations like that happening there.
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