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If the undershoot is flat you can duck under to get extra distance. Not everyone's cup of tea, but if you're close to the margain... |
Originally Posted by vilas
(Post 10333658)
The very fact that you feel that the approch requires something which is not done is a message that you shouldn't be landing there. Short runway, limit tail wind which could easily go over the limit, heavy rain can make the braking action poorer than imagined and control of flight path difficult these are too many variables which can prevent a successful outcome. Not a safe decision to continue the landing.
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Originally Posted by Meester proach
(Post 10333330)
So if the performance data was OK, and you diverted where does that leave you ? What could make a difference is local knowledge - does this runway feel like it actually meets the performance normally or not from past experience ? |
Originally Posted by CHfour
(Post 10333476)
"Not everyone's cup of tea" Really? If you try that one over on my side of the pond you'll find yourself in the Chief Pilot's office and there won't be any "cup of tea" (or any biscuits for that matter).
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Originally Posted by Check Airman
(Post 10333961)
For exercising airmanship? In limiting conditions, many ppl will go 3 red on the PAPI at LGA or DCA for example (where your final approach is over water) to get a few extra feet of runway.
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That's where airmenship comes into play. Long body/heavy perhaps not, narrow body perhaps yes.
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Originally Posted by Meester proach
(Post 10333330)
So if the performance data was OK, and you diverted where does that leave you ? What could make a difference is local knowledge - does this runway feel like it actually meets the performance normally or not from past experience ? |
Originally Posted by aterpster
(Post 10333980)
At LGA if I did that in the 1011, I'd be risking leaving the main gear with the end of the pier.
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The very fact that you feel that the approch requires something which is not done is a message that you shouldn't be landing there. Short runway, limit tail wind which could easily go over the limit, heavy rain can make the braking action poorer than imagined and control of flight path difficult these are too many variables which can prevent a successful outcome. Not a safe decision to continue the landing. |
172, ‘valid landing performance’, no such thing before the landing, only judgement of the unknowns: wet or flooded, what about all the conditions in between. Who measures / reports the conditions; the same with wind, at least +/- 2, so allow +/- 5. There are few absolutes in flying other than the position where you stop; assumption kill, so concentrate on minimising all other variables, speed, touchdown, bakes, etc … . |
There is no short landing technique on a jet this size. Arriving on a decreased angle (3 red) carries higher pitch, more thrust, flatter sink and in general results in a longer touchdown and a higher speed at wheel spin-up. After that, exactly the same sort of people who use the A word to cover gaps in competency or understanding, will immediately claim: see how tight this was? Lucky my skygod decision to go 3 reds, it saved us. Yeah.
Aiming closer to the threshold, steepening the angle in the last stages is more consistent with the intention. Why not, if you know how not to try too hard. Still, reducing geometrical margins on purpose, creating ad-hoc flying techniques, is not the road to a happy retirement. Land it consistently, as much identical as your everyday approach. Consistency brings predictable results. The touchdown is usually decided between 150 and 50 feet above the ground. If a runway below 2000 m requires a different skill-set, then the one you have on the longer runways is not a correct one. (Placement of PAPI at 400 or 450 m beyond the THR, as opposed to 291 m where the G/S geometric intercept is, WILL create a wrong skill set for those who follow PAPI through to the landing). The above is a comment to the discussion here, not the incident itself. We will see what the investigation reveals, however, "no landings beyond TDZ markings" is a sound principle. I am curious to see if it did not work in BUR? One last note: the (lack of) friction over THR markers at the far end, when wet/snowed, is what makes this man uneasy. The last 60 m you might critically need, and as if they did not exist. I suppose everyone had a NW skid during line up once, for no apparent reason. |
Originally Posted by Check Airman
(Post 10333961)
For exercising airmanship? In limiting conditions, many ppl will go 3 red on the PAPI at LGA or DCA for example (where your final approach is over water) to get a few extra feet of runway.
Originally Posted by aterpster
(Post 10333980)
At LGA if I did that in the 1011, I'd be risking leaving the main gear with the end of the pier.
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Originally Posted by Airbubba
(Post 10334268)
I've seen folks who brief that they want to drop a dot low on the glideslope on short final in widebodies 'since the weather is good'. Is this in the book anywhere? I get the impression that this 'technique' was taught in some Air Force communities (possibly the C-141) years ago. |
Originally Posted by Check Airman
(Post 10334300)
Not in any book that I've seen, but when landing on a short, wet runway as described above, most of the people I fly with decide against leaving the first thousand feet of the runway behind.
The expression used was ‘duck under’ (the glide path) on short final. The concept, and the expression were remarkably unpopular with the FAA due to the quite sensible requirement for a stabilsed approach. Ducking under was replaced with the more politically correct term of ‘adjusting the aim point’. Midway, Key West and Burbank are relevant examples. |
This boils down to how much runway should be behind the touchdown point. When I were a lad, many moons ago, there were no piano keys and we were taught to aim for the numbers. The piano keys were introduced to reduce the incidence of landing short of the paved surface, thus "wasting" part of the runway. All modern aids such as ILS and PAPI are calibrated for the piano keys so the actual landing distance available is less than the runway length which can become an issue for shorter runways in poor weather conditions.
Should we aim shorter for the numbers in these cases ? - I will leave that can of worms for others to chew, the risks have not changed. Aiming for a firm contact, avoiding greasers, is probably a better idea getting good weight on the wheels ASAP to improve braking. |
. If a runway below 2000 m requires a different skill-set, than the one you have on the longer runways is not a correct one. |
Originally Posted by The Ancient Geek
(Post 10334412)
This boils down to how much runway should be behind the touchdown point. When I were a lad, many moons ago, there were no piano keys and we were taught to aim for the numbers. The piano keys were introduced to reduce the incidence of landing short of the paved surface, thus "wasting" part of the runway. All modern aids such as ILS and PAPI are calibrated for the piano keys so the actual landing distance available is less than the runway length which can become an issue for shorter runways in poor weather conditions.
Should we aim shorter for the numbers in these cases ? - I will leave that can of worms for others to chew, the risks have not changed. Aiming for a firm contact, avoiding greasers, is probably a better idea getting good weight on the wheels ASAP to improve braking. |
Originally Posted by West Coast
(Post 10334094)
That's where airmenship comes into play. Long body/heavy perhaps not, narrow body perhaps yes.
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Originally Posted by Ancient Geek
All modern aids such as ILS and PAPI are calibrated for the
Originally Posted by Flight Detent
Arriving on a decreased angle (3 red) carries higher pitch, more thrust, flatter sink and in general results in a longer touchdown and a higher speed at wheel spin-up.
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No aircraft manufacturer or Company SOP suggests duck under technique nor does certified landing performance expects a pilot to do that. So there is simply no justification narrow body, wide body, turbo prop all included. If there is a runway which requires that then that type of aircraft should not be operating there. It is not proper to suggest unsafe alternate techniques to increase landing run for the present SWA case. If the touchdown was at proper distance then it will prove that the landing should not have been affected with so many limiting variable environmental and RW lenth factors.
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No aircraft manufacturer or Company SOP suggests duck under technique nor does certified landing performance expects a pilot to do that. So there is simply no justification narrow body, wide body, turbo prop all included. If there is a runway which requires that then that type of aircraft should not be operating there. It is not proper to suggest unsafe alternate techniques to increase landing run for the present SWA case. If the touchdown was at proper distance then it will prove that the landing should not have been affected with so many limiting variable environmental and RW lenth factors Do you ever operate on contaminated? Slush, dry snow, sanded, snow on ice... a combination of them all? The calculations show we are legal, but we all know the braking action is a best guess. My experience with 737 is the brakes are doing a great job. We often stop much shorter than the app tells us. But 1800 m in a 737-800 with contamination and a river at the far end is not the place to be "academic". |
For the sake of a good discussion, a question for those who are categorically against touching down a bit early- If on a bad wx day, your company builds a flightplan with the absolute legal minimum fuel, do you always accept fuel shown on the flightplan?
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Oh come on, you can do better than that C/A. :}
Different game: On your A/C type for an ILS approach, when everything is perfectly aligned, the RA auto-calls "50" when the pilot seat is over the THR markings (piano keys) - TRUE or FALSE? (it's not an open book question). Close your eyes and say it .... ? Yet to give you an answer, I am sure everyone does a bit more pushing on the short runways and tries to tweak it closer to the tarmac edge. The point made is the correct normal technique will suffice: 291 m aim-point, 450 m (-50/+25) touch-down point, Vref to Vref -5. The best a pilot can do to be safe and effective on short runways is to practice on the longer ones to get that skill perfected. https://i.postimg.cc/XXjhTKGP/TDZ-area.jpg (clickable image) This is where I earned my first stripes - LDA 3400ish. The rubber marks paint a picture where many of the pilots are in true need of a different technique for the shorter runways. No denying that. Maybe we can see a picture from your side of the world. |
If you land the aircraft in the way the Boeing, training manual specifies you will attain the required landing performance every time. No need to have a separate short field or long runway technique. Do it the same every time and the performance requirements will be met. Now, there is room for error and the wiggle room the performance calculations give you is less on wet runways and almost nothing on contaminated. You’ve also got to make 100% certain the auto speed brake deploys, the auto brakes activate, and the reversers which may normally only be brought to idle are used straight away, at maximum reverse. If you land long and/or one of the autobrake, speedbrake or reversers are not activated, an overrun may well be on the cards. Read through the NTSB reports on the AA 757 overrun, at Vale, the SWA, Midway overrun and the Eastern, La Guardia 737 overrun to see how a short runway and a braking system failure or late selection can cause trouble fast. |
If you land the aircraft in the way the Boeing, training manual specifies you will attain the required landing performance every time. No need to have a separate short field or long runway technique. |
I suppose you are right 172 driver. The biggest problem with contaminated runways is that when you are in dynamic situation i.e it’s starting to snow or raining heavily it can be hard to know when the runway is contaminated and what the braking actions are. It’s not not like there is someone measuring the contaminant depth or checking the braking action every few seconds. Pilot, reports are not reliable either. Maybe the SWA pilots, thought that the braking action was better than it truly was. I don’t know much about performance as a subject, other that it is kind of vague. |
The biggest problem with contaminated runways is that when you are in dynamic situation i.e it’s starting to snow or raining heavily it can be hard to know when the runway is contaminated and what the braking actions are |
Originally Posted by FlightDetent
(Post 10334736)
Oh come on, you can do better than that C/A. :}
Different game: On your A/C type for an ILS approach, when everything is perfectly aligned, the RA auto-calls "50" when the pilot seat is over the THR markings (piano keys) - TRUE or FALSE? (it's not an open book question). Close your eyes and say it .... ? Yet to give you an answer, I am sure everyone does a bit more pushing on the short runways and tries to tweak it closer to the tarmac edge. The point made is the correct normal technique will suffice: 291 m aim-point, 450 m (-50/+25) touch-down point, Vref to Vref -5. The best a pilot can do to be safe and effective on short runways is to practice on the longer ones to get that skill perfected. https://i.postimg.cc/XXjhTKGP/TDZ-area.jpg (clickable image) This is where I earned my first stripes - LDA 3400ish. The rubber marks paint a picture where many of the pilots are in true need of a different technique for the shorter runways. No denying that. Maybe we can see a picture from your side of the world. As you can see here, many folks going into LGA prefer to add a buffer to the landing distance available. Couldn't find a similar picture for DCA. |
In response to to 172
A cautious duck under as you describe it (= closer choice of the aiming point for purists) is surely not a sin. 172 we are in agreement it is part of the duty even, to make sure all the odds are in our favour. My aeroplane on the G/S has 30 ft RA margin over the THR, leaving - 10' for me not being accurate - 10' for a gust or shear - 10' before the making news. Geometrically, G/S intersects 291 meters deep. To keep at least 20' screen, aiming for the 200 m point is the shortest sensible option. The extra 90 meters is not a negligible distance, sure. Still, it is a straw-man. Only the touchdown point and speed count. Both are defined by the speed vector at 50' more or less, bit by individual flare technique and largely by correct thrust reduction for the landing. If we point the A/C steadily to the correct point (not short) between 150-50 feet AGL, cross the THR on the G/S and retard the thrust to idle by 15', the proper touchdown distance is always assured. Mr. Newton and mother Earth will take care of that. One way to mess things up is to fiddle with thrust through a non-standard flare, having decided at 70' to do something creative. Not aiming short(er) never caused an overrun. |
Without any real intention, just a few pictures.
- the red dot is 3° intersect, i.e. instrument aiming point - the blue line is the PAPI reference - the green field is 400-475 meters from THR (There are some unusual things about Burbank) Burbank 8 https://i.postimg.cc/901gt54R/BUR-tdz.jpg Regan 19 https://i.postimg.cc/022B5Q3p/DCA-tdz.png LaGuardia 22 https://i.postimg.cc/Y96s0mMx/LGA-tdz22.jpg Kingston 19 https://i.postimg.cc/h40YqxCD/MBJ-tdz.png Toronto 24L https://i.postimg.cc/rmXHq9Xm/YYZ-tdz.jpg Sweet Home 24 https://i.postimg.cc/j2Rk7djY/TDZ-area.jpg |
Let's not kid ourselves, shorter runways require different flying. Aim point and touchdown take a higher priority vs trying to land smoother. The touchdown zone where the landing is required is 1/3 of the landing distance or the first 3000'. With a 5802' runway the requirement to be on the ground is 1930'. How many regular landings go around if they're not down by the 2000' mark? None. Shorten the runway to 5100' and the go-around requirement reduces to 1700'. How many normal runway landings go-around if they're not on the runway by 1700' from the threshold? Answer: none.
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Shorter runways require correct flying, whereas the long runways don't, absolutely.
Full points on the priorities, not so much about the touchdown zone. Although we say the touch-down zone is the first 1/3 or 3000 ft (shorter of), it is not how the aeroplane should be landed. Touching down at 3000 ft (1000 meters ffs!) on a 9000 runway is NOT ok. To keep the performance data valid the ILS receiver passes the THR at 50', going for 955 ft (291m) intersect point against the pavement. The normal touchdown ensues around 450 m (1500 ft), anything beyond 600 m is not correctly done. Irrespective of runway length. Sure, we've all done it multiple times and nothing was compromised but it is not playing by the rules. Somewhere in Germany - pure ICAO Annex 14 standard for runways 1500-2399 m. Four distance markers. LDA 2180 m of which 1/3 is 730. 5x markers would be appropriate to show the 1/3rd "touchdown" zone. https://i.postimg.cc/ZKYZpJ9c/PAD-tdz.png |
Back on the topic of the SWA over-run itself.
Red point = nominal 3° slope intersect with pavement (assuming 50' at THR) Green field = expected landing area as per FCOM and AFM/performance assumptions Blue area = conventional understanding of touchdown zone (1/3rd of the runway here) Magenta line = actual position of the PAPI Note: according to ICAO Annex 14 there should only be 4 distance markers for this runway length. https://i.postimg.cc/05m52n6q/Burbank-distances.png The crew should fight nails and teeth to use this in their defence. The PAPI will take you 600 feet beyond the proper aiming point, and the last two distance markers on the pavement are nothing but a deathtrap. Comments? |
On the the charts it notes that VGSI and ILS are not coincident.
VGSI at 3 degrees has 72' TCH ILS at 3 degrees has 60' TCH. That extra 12 feet puts you quite a ways down the runway.....228 feet to be exact. Note: FAA does not use ICAO standards. https://cimg9.ibsrv.net/gimg/pprune....0d76e2292a.jpg https://cimg7.ibsrv.net/gimg/pprune....aebff801f4.jpg |
Originally Posted by FlightDetent
(Post 10335076)
Back on the topic of the SWA over-run itself.
Red point = glide-slope intersect with pavement Green field = expected landing zone as per FCOM and AFM/performance assumptions Blue area = conventional understanding of touchdown zone (1/3rd of the runway here) Magenta line = actual position of the PAPI Note: according to ICAO Annex 14 there should only be 4 distance markers for this runway length. https://i.postimg.cc/05m52n6q/Burbank-distances.png The crew should fight nails and teeth to use this in their defence. The PAPI will take you 600 feet beyond the proper aiming point, and the distance markers on the pavement are nothing but a deathtrap. Comments? I think it is safe to say you have never landed 60 tons of 737-800 on a 1800 m snow covered runway with BA Medium. When you have done this exercise, please return with your fancy theories and tell us you don’t want as much runway ahead of you as possible when you touch down. ONE focus only, get the wheels on the ground as early as possible, very little flare, spoliers, reverse and brakes. STOP. Breathe. |
Originally Posted by Underfire
That extra 12 feet puts you quite a ways down the runway.....
A recent report on a over-run near miss in Christchurch shows what effect just a little bit of ponding can do to the braking action: Reduced braking effectiveness during landing involving Boeing 737-800, VH-VOP at Christchurch Airport, New Zealand on 11 May 2015 *3 degrees is 5% = 20 x factor |
In design, we begin with a 3 degree GS with a 50 TCH. Usually, due to obstacles in the approach, the TCH is raised up. This is not encouraged because of the issues with the lights, markings, and runway length. Some procedures keep the 50 ' TCH and use a higher glideslope..this helps with some of the issues.
Looking at the chart, the ILS and RNAV TCH are both 60. The VGSI is set at 3 degrees with 72 TCH, so if you follow that, you are really long... This airport is funny, looking at the missed, it requires 340/nm climb rate, tough to do in the heat...the reason? The controlling obstacle in the missed is the folded wings monument to aviation! https://cimg3.ibsrv.net/gimg/pprune....a312184f63.jpg Look at SFO, especially after the accident, multiple TCH |
Having a senior moment here gents. On Jepp charts, is the TCH based on the GS or PAPI?
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Glideslope
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at BUR both the GS and PAPI use a 3 degree GPA....
The TCH places the GPA height at the Threshold. |
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