Touchdown Zone and long landings for jet airliners question

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bigjuicyspider
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Touchdown Zone and long landings for jet airliners question

Post by bigjuicyspider »

More than 50% of my time in FSX is spent flying the big 'ole jet airliners. With American airports my visual aim point is always on the big blocks, 1000 feet down the runway. In a plane like the pmdg 737, when on G/S and Vref+5, a flare (more like the gentlest of tugs on the yoke) and retarding the throttles starting at about 20 feet, all by the book apparently, typically give me a main gear touchdown somewhere between 1500 and 2000 feet from the threshold and a VS of under 100 fpm with consistency.

My question: Is 1500 to 2000 feet down, although still within the touchdown zone, considered sloppy for a plane like the 737? Even if the runway is long and dry and clear, is this acceptable, or should I allow the plane to bang in a little harder and sooner in order to most accurately replicate the best practices of the real world? I actually find it visually difficult to flare any less in a plane like this.

(The question, although pertaining to simulated commercial jets is really also applicable to other types. One of the problems I have is that I alternate regularly between A2A aircraft like the B377 and the B-17, and then go back to the pmdg jets...So I'm frequently either slamming into the pavement with the A2A aircraft, with the Copilot typically groaning like he has suffered a spinal injury, and me muttering "get over it you p****!" or else I'm over-flaring and glassing it on late in the Jets!!! )
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goughie
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Touchdown Zone and long landings for jet airliners question

Post by goughie »

I also split my stick time between a wide variety of aeroplanes. The only way to switch between the big iron and say, the P51 is to read the pilots notes , get the numbers in your head and fly accurately. Works for me. If I try to rush it I can get it really wrong. Fly the pattern until you get it right! Good luck!

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Jack Sparrow
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Re: Touchdown Zone and long landings for jet airliners quest

Post by Jack Sparrow »

bigjuicyspider wrote:
My question: Is 1500 to 2000 feet down, although still within the touchdown zone, considered sloppy for a plane like the 737? Even if the runway is long and dry and clear, is this acceptable, or should I allow the plane to bang in a little harder and sooner in order to most accurately replicate the best practices of the real world? I actually find it visually difficult to flare any less in a plane like this.
Interesting question to which I don't know the answer. What I can do is give you a criteria (not necessarily best practice :) ) used by a 727 jock while I was in the jumpseat. His intention was to thump it in short so that he could use the first exit off the runway to reduce taxi time to the terminal.

He succeeded but the landing & braking was so severe as to cause a couple of overhead lockers to burst open, showering passengers with the contents. :roll:

joediamond
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Touchdown Zone and long landings for jet airliners question

Post by joediamond »

Touching down at the 1500' beyond the threshold is quite normal. The glide slope would put you on the fixed distance markers (1000' beyond threshold) if you didn't flare. A normal landing flare will put you about 500' further down.

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CAPFlyer
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Re: Touchdown Zone and long landings for jet airliners quest

Post by CAPFlyer »

Well, there are several markings on the runways. The big solid bars are called the "Aim Point Markers" and are exactly for that.

Here's a picture of 33L at Boston Logan circa 1999. It's not the greatest for looking at tire marks, but if you notice, the majority of them are at and beyond the Aim Point markers. When flying the ILS, this is where you'll end up. When flying a visual approach, many pilots fly in a tad low and aim to touchdown at the markers, so their aimpoint would be the markers just before the TDZ markers.

Image

The other markings denote the "Touchdown Zone". You are supposed to land somewhere within those markings depending on what category of airplane you are. III for the "Heavies", Aimpoint for the "Larges", II for the "Mediums", and I for the "Light/Small" aircraft. Does it ever get done? From my observations, not really. Then again, unless you actually go and read ICAO Annex 14, it might as well be Greek for most of us. :)
Image

joediamond
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Re: Touchdown Zone and long landings for jet airliners quest

Post by joediamond »

CAPFlyer wrote: Image

The other markings denote the "Touchdown Zone". You are supposed to land somewhere within those markings depending on what category of airplane you are. III for the "Heavies", Aimpoint for the "Larges", II for the "Mediums", and I for the "Light/Small" aircraft. Does it ever get done? From my observations, not really. Then again, unless you actually go and read ICAO Annex 14, it might as well be Greek for most of us. :)
Please state your source because, for the lack of a nicer way to put it, this is flat out wrong. The number of hash marks simply indicates the distance from the threshold. "III" at 500', the fixed distance markers at 1000', "II" at 1500-2000 and "I" at2500-3000. It's a visual reference to alert the pilot to how much distance is remaining in the touchdown zone.

Heavy aircraft actually use an aim point farther from the threshold than smaller aircraft to compensate for the pilots higher line-of-sight. That is why three bar VASI systems exist. Using the 500 foot point as your aim point in a heavy will put your main gear in that EMAS bed.

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CAPFlyer
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Re: Touchdown Zone and long landings for jet airliners quest

Post by CAPFlyer »

According to ICAO Annex 14, the hash marks are the "normal" touchdown zones for the various aircraft. The VASI and ILS is to keep all aircraft on a constant approach path. If you follow it exactly, the larger aircraft will progressively land shorter as the mains are further behind the VASI and ILS glideslope. Again, it's something buried in the annals of the complex "standards" that the ICAO puts out and I'd not known about it until I was made aware of it by an acquaintance who just recently completed her master's course in airport operations, which included a comprehensive review of Annex 14. Being that she's also a high-hour pilot with a lot of experience flying various Citations and spending many years flying night freight, it was a surprise to her too. I chalk it up to the difference between the FAA and the ICAO, it wouldn't be the first time.
Image

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bigjuicyspider
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Re: Touchdown Zone and long landings for jet airliners quest

Post by bigjuicyspider »

Thank you gentlemen for your answers. This info will help me tighten my landing techniques up a bit for a variety of aircraft. I was concerned that I was landing a bit long by real-world criteria, but it looks like I'm not doing so bad...I think I'll start setting it down just a little bit tighter and harder for an aircraft like the 737, but not by much.

Also, some of you guys probably already have a variation of this, but I have found this little P. Dowson Lua script floating around the web that seems to be quite useful in gauging touchdown performance, in addition to the feedback of Ezdok and Accu-Feel. In the absence of real seat-of-the-pants feedback to judge the firmness of my landings, it helps me resist the temptation of looking at the VSI when I should be looking at the far end of the runway instead. All it does is pop up a little display window in the left hand corner 20 seconds after you land that tells you what your final vertical speed was. I put a 20 second sleep delay in there so that it doesn't cause a micro-stutter the moment you land and to make the display window less intrusive. If you have payware FSUIPC, just copy and paste it, save it as ipcReady.lua and put it in your FSX Modules folder.

Code: Select all


function onground(off, val)

--Orig by P.Dowson, modified for sleep delay and window position to left upper corner

   if val ~= 0 then

-- if on ground flag just set, get VS, convert it and display it
     
      ipc.sleep(20000)
      landvs = -math.floor( (ipc.readSD(0x030C) * 60 * 3.2804 / 256) + 0.5)
      ipc.setdisplay(0,0, 200,200)
      ipc.display("Touchdown fpm = \n       " .. landvs, 10)
   end
end 

-- set to call above routine whenever "on ground" flag changes

event.offset(0x0366, "UW", "onground")
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pjc747
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Re: Touchdown Zone and long landings for jet airliners quest

Post by pjc747 »

Well one thing you need to remember is that when flying the airliners, you want to get landed on the runway in the target area, so you can safely come to a complete stop. However, since you are simulating airline operations, you need to consider that a smooth, silky landing is better than landing as soon as possible. Its not like you're a Navy pilot and you have to capture within a 100ft zone, preferably wires 2 or 3, or else need to go around or even worse, have a fatality. So you don't want to float down to the halfway marker trying to have a cushiony landing, but you also don't want to drop it onto the runway ASAP.

greasysidedown
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Re: Touchdown Zone and long landings for jet airliners quest

Post by greasysidedown »

You should be at stabilised at Vapp, on GS or VASI/PAPI and fully configured to land at 1000' AGL and Vref at 50'. Touchdown should be in the first third of the runway. I agree that is a some what imprecise statement and gives the pilot more room to play with at some airports than others.

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seaniam81
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Re: Touchdown Zone and long landings for jet airliners quest

Post by seaniam81 »

greasysidedown wrote:You should be at stabilised at Vapp, on GS or VASI/PAPI and fully configured to land at 1000' AGL and Vref at 50'. Touchdown should be in the first third of the runway. I agree that is a some what imprecise statement and gives the pilot more room to play with at some airports than others.
Please remember that not all VASI and PAPI are in sync with the GS! You might be on ILS GS but the VASI/PAPI might say your high or low of the GS.
Also please remember that not all VASI/PAPI's are built the same! They are designed and installed on runways for a specific wheel to eye height. That means if a VASI/PAPI system that was designed and installed for say a B1900, and was flown by say a 747 it would crash the 747 short of the runway.

Swedenhausen
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Re: Touchdown Zone and long landings for jet airliners quest

Post by Swedenhausen »

bigjuicyspider wrote:More than 50% of my time in FSX is spent flying the big 'ole jet airliners. With American airports my visual aim point is always on the big blocks, 1000 feet down the runway. In a plane like the pmdg 737, when on G/S and Vref+5, a flare (more like the gentlest of tugs on the yoke) and retarding the throttles starting at about 20 feet, all by the book apparently, typically give me a main gear touchdown somewhere between 1500 and 2000 feet from the threshold and a VS of under 100 fpm with consistency.

My question: Is 1500 to 2000 feet down, although still within the touchdown zone, considered sloppy for a plane like the 737? Even if the runway is long and dry and clear, is this acceptable, or should I allow the plane to bang in a little harder and sooner in order to most accurately replicate the best practices of the real world? I actually find it visually difficult to flare any less in a plane like this.. (snip)
I'm a real life 757 Captain and you are describing exactly the technique for landing a Boeing with wing mounted engines... Regardless of the above bickering about the TDZ markings.. all we do in the real world is aim for the big blocked aiming points("Captain's bars" - as they look like the O-3 insignia from my Marine days). All you need to do is be on the runway before that last stripe goes under you, and you'll have it made.

Normally performance software includes a flareout in the landing distance computation, especially if operating with low vis (less than 4000ft rvr/1200m rvr)

It's interesting to hear about the meanings of the different stripes, but I've never really heard anyone actually aiming for anything other than the aiming markers.. What I do know is you can still stop if landing beyond the touchdown zone (most likely) but I would advise a go-around especially if you are on a line check or in a recurrent sim checkride!
ImageImage

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