ET phone home?

[Boac]

At it again - from Av Herald - Addis Ababa in the rain (my emphasis), a 738:

"Position data transmitted by the aircraft's transponder suggest the aircraft touched down at 155 knots over ground about 6920 feet past the displaced runway threshold (landing distance available 11297 feet, thus 4377 feet remaining), crossed the displaced threshold 25L about 3250 feet later, veered right and came to a stop beyond the right runway edge about 3720 feet past the touch down position, about 10,630 feet past the displaced runway threshold 07R and about 670 feet short of the runway end."

Optimists all? I'll spare Reddo the METAR

[TheGreenGoblin]

I had to look up the report to find out how it all turned out. As one of the commentators there said.

By Forrest Green on Tuesday, Aug 27th 2019 15:01Z

That is not just floating merrily along, 1.3 flipping miles.

That is equivalent to over flying every wire on a carrier, and

pulling power as you cross the front round down on the angle

deck...........That bullet they did dodge.....

"There were no injuries, the aircraft sustained minor if any damage."

http://avherald.com/h?article=4cc0fcf7

[barkingmad]

I refer the right honourable gentlemen to thread “Boating 737” posting # 36 et al.......

Erewego again.

[Boac]

Barking - (a link to that post would have been helpful!!) - this thread is more about where one plants the metal, not how fast one does it. +20kts in the right place would have been 'ok'. Over a mile down the runway, it wasn't.

[barkingmad]

And the lethal combination of "where" and "how fast" is not relevant?

To widen the discussion I will propose that the half steady headwind added to gust factor plus aiming at (and missing) a set of markings 300m/1000ft from the landing threshold plus current handling skills will ensure more excursions particularly overruns into unpaved areas with inevitable tragic results.

I don't recall the 300m/1000ft aiming point featuring at all in normal medium size airliners' operations until the 747, DC10, Tristar and any other long body 'frames arrived on the scene. Then in order they did not wipe their U/C off at the grass-concrete lip their aiming point was shuffled further down the runway and somehow everyone else who wasn't a 'heavy' followed suit.

Perhaps too many glasses of electric soup in various bars has distorted my memory so I anticipate being corrected on this score......

[Boac]

And the lethal combination of "where" and "how fast" is not relevant?

- in the context of this thread, no, in my opinion. The runway would, I think, have coped with a 'fast' touchdown in the right place.

I have no way of knowing what a 'sensible' approach speed at that time and place would have been, but I do know that not going round when you have eaten up 2/3 of a wet runway is relevant.

I don't recall the 300m/1000ft aiming point featuring at all in normal medium size airliners' operations until the 747, DC10, Tristar and any other long body 'frames arrived on the scene.

- way before my time.... I know no other way now.

I 'grew up' planting high-performance metal ON THE NUMBERS at the right speed and had to make the transition to '300m' during the brain operation.

[barkingmad]

Tha actual position of this aircraft will be clarified if the DFDR results are publicised.

Observing SSR returns on ATC radar is not the best way of determining the position with any precision as they tend to jump and skitter around the display and the refresh rate also has an influence.

Certainly if they were 1nm down the strip still doing 155kts then one has to exclaim WTF!!

Returning to my fetish with excess bernoullis if there was a surface wind of 40kts at a sea level airport with no orographics upwind to cause turbulence (hence gust factor) then why does my wing need +20kts to avoid killing me?

A gale of that strength is not going to suddenly drop and leave me lacking kinetic energy and hence losing airflow.

boac, we both were trained by the same excellent flying school and I was also expected to plant my metal on the numbers-a great system at the time.

I do NOT recall all runways in civilian use being extended by 300m/1000ft when those touchdown markings were introduced so the unfortunate airline crews have literally been squeezed 'twixt piano keys and the overrun as a result of markings and procedures introduced for vastly different aircraft types.

[Boac]

I do NOT recall all runways in civilian use being extended by 300m/1000ft when those touchdown markings were introduced so the unfortunate airline crews have literally been squeezed 'twixt piano keys and the overrun as a result of markings and procedures introduced for vastly different aircraft types.

- I don't think airliners of any size pre "747, DC10, Tristar and any other long body 'frames arrived on the scene." ever landed 'on the numbers' or they would have dragged their arses through the undershoot! Crossing the threshold in a 747/DC10 at 50' would almost certainly result in a touchdown at 300m or thereabouts. Have you done the '3 degree GP with a flare' sums? There was never an effective 'loss' of 300m.

Back to your basic knowledge of met - what happens to the wind as you near the surface? Would you advocate Vref in a 40kt wind? I think you would be on your own What would you advocate? You have to think groundspeed as well, 'cos that is what stopping is all about - not airspeed. You do not need the same RDR for a landing 40kts slower than another!

[barkingmad]

boat wrote “I don't think airliners of any size pre "747, DC10, Tristar and any other long body 'frames arrived on the scene." ever landed 'on the numbers' or they would have dragged their arses through the undershoot!”

We did in Dan-Air in the BAe146-300 series at Berne regularly-captains only landings.

No marks in the grass but one did end up with NLG on the grass at the far end......

Answer to the met question is backs and decreases with altitude but over the last 1000’ of approach by how much is that?

[Boac]

Was that official company policy for Berne? I don't think you would pass a line check on a 737 that way!

Good answer, but don't forget one normally selects Vref at or above 100'. The aim is, as always, to reduce approach speed as you get lower as per FTM.

[barkingmad]

Berne LDA would not allow any airliner to piss away300m/1000ft of paved surface at its 1980s length.

The navvies and concrete mixers might have been in action since then.

And YES, it was SOP for the type and the company, plant as early as possible and stop it.

Maybe NG operators might like that in preference to overruns but l doubt it.

IIRC Mr Boeing rigged his types Vrefs and therefore approach speeds to keep the ‘frames’ approach category at 1 lower than where they should have been.

Hence their Vref always seemed for actual handling & training to have that magic +5kts tagged onto them rather than crossing the landing threshold at Vref.

Gusty conditions certainly add suitable factoring for the ASI needles/tapes oscillations but the steady smooth HW increase I have never understood. Maybe I’d better get back to CFS and get the 4 colours of magiboard markers out and go through it “Bloggs On” with a suitable A1 god?

[Boac]

I'm sorry, BM, I do not understand this bit:

"IIRC Mr Boeing rigged his types Vrefs and therefore approach speeds to keep the ‘frames’ approach category at 1 lower than where they should have been.

Hence their Vref always seemed for actual handling & training to have that magic +5kts tagged onto them rather than crossing the landing threshold at Vref."

The Boeing FTM, on which 737 pilots are normally trained, suggests that landing at Vref-5 is ideal (crossing the threshold at Vref+5 (plus wind corrections)) but Vref-10 is in danger of a tail strike.

I cannot understand your problem of adding half the wind speed to Vref - as I said, it is GS not IAS that matters in stopping. The problem is occurring because Captains are not strict enough (or do not set the example) of flying the correct target speeds, and touching down long is not discouraged by many. As for

"Maybe NG operators might like that in preference to overruns but l doubt it."

- no they would not, since performance calculations for LDR are based on the 300m touchdown as you know and if a runway does not allow that touchdown point for the weight you do not plan to go there!

Back to topic - the thread is about landing 2/3 of the way down a wet runway, not flying too fast.

Out of interest, what was the problem at Berne? We used to take 734's (heavier and faster) into Jersey on just over 1700m. - and touched down in the 'right' place

[barkingmad]

“Rigged approach speeds”-a frequent comment by those more experienced than me from BA through XL through Ashtrays-r-us and into JetAirFly.

Berne ashphalt in those days was 1310metres-happy now?

Any time when in the rhs that I got near Vref in a Boeing over the paved surface the the voice of the lhs occupant as they called “SPEED” increased markedly in both volume and pitch! This also happened on the Classic 747 whilst I was in BA.

Steady headwind conditions present the wing with relative airflow sufficient to keep the heap aloft. Why then do I want to iINCREASE my approach speed and risk extended landing distance required when there is no need? The wing does not know/care what the G/S is and IIRC from basic training tweaking the G/S upwards in strong steady headwinds doesn’t affect its lift.

Elsewhere I have seen that the NG wing is a different wing from the “Classic” & earlier variants and therefore might have required different and higher approach category resulting from the aerodynamics changes but Boeing were desperate to keep it in the older category. I agree this will be difficult to both refute or confirm but that is what I absorbed over nearly 10 years on the type. Also the longer body length increased the tailstrike risk which also pressured crews into keeping “a bit more IAS for mum & the kids”. Therefore it is possible the NG -800 and especially the -900 series could be seen as a stretch too far (vide the MAX!) but a TRUE Vref for the revised wing would have pushed up the approach category to the next value.

In conclusion, of course in gusty turbulent conditions IAS additive is necessary and wise. The perceived reluctance of Boeing pilots to nail the speed AT Vref AT the landing threshold with minimal extra energy, possible transient tailwind conditions onto a wet runway aiming for the 300m point in what is accepted as a “slippery beast” with current handling skills having started with Vref+20kts WILL result in fatal overruns.

How many of the type have run out of Bernoulli’s and wiped the MLG off on the grass to concrete interface compared with sometimes fatal overruns? And the THY at AMS and the SFO seawall accidents don’t qualify as stats for comparison.

Are there any other current NG and/or former 73- drivers on this forum who have experience to comment?

[Boac]

BM - I cannot comment on why the LHS may have shouted at you for your speeds as I was not there to watch you! I can only assure you that I would not have commented on a stable Vref landing by my co-pilot but 'shouted at' if too fast on a limiting runway OR 'debriefed' (rolled up copy of the Times) if not limiting.

Regarding

Elsewhere I have seen that the NG wing is a different wing from the “Classic” & earlier variants and therefore might have required different and higher approach category resulting from the aerodynamics changes but Boeing were desperate to keep it in the older category. I agree this will be difficult to both refute or confirm but that is what I absorbed over nearly 10 years on the type. Also the longer body length increased the tailstrike risk which also pressured crews into keeping “a bit more IAS for mum & the kids”. Therefore it is possible the NG -800 and especially the -900 series could be seen as a stretch too far (vide the MAX!) but a TRUE Vref for the revised wing would have pushed up the approach category to the next value.

I suspect you have been a victim of 'old wives' tales' (owt). The QRH Vref for the -700 at a given weight was at least 10kts SLOWER than that for the Classic ('better' wing). The QRH Vref for any particular weight in a -800 is approximately 5-7 kts HIGHER than the same weight in -700 (same wing) - and I understood this was purely due to the risk of tailstrike in the -800. You are welcome to scans of these if you wish although you probably still have your -700 perf somewhere?

I experienced the 'owt', many times, including one quite 'amazing' Icelandic co-pilot who assured me that he had been told by 'a Captain' that the PLOG div fuel did not include go-round and climb fuel which needed to be added to the PLOG figure! This particular chap must have flown with quite a few 'old wives' since his many other 'quotes' were amazing - and he was never 'happy' with our agreed fuel uplifts !

[barkingmad]

OLD WIVES TALE??

FLIGHT MANUAL EXTRACTS:

737-800 max landing weight of 65,317 kgs, Vref is 141kts with max 40 landing flap, normal ops used F30 so Vref was 149kts.

From Flight Manual 737-800 the following:
Category D Threshold Speed is 141-165kts.

Then a cryptic “Note: Boeing has obtained Category C certification for all B737-800’s”. WHY?

There is further highlighting in the NG Differences course notes regarding pitch attitudes v tailstrikes, the figures for which I don’t currently have access but will have soon.

So it wasn’t a booze-fuelled impression of any spouses stories but these figures I’ve found having exhumed various publications from the loft!

So maybe the 737-800 and descendants was a stretch too far with the added complications of long-body GS paths and long-body touchdown points coupled with excessive Vref additions = overruns & accidents?

[Boac]

I never knew how it was kept as Cat C**, but out of interest, to reinforce my points about the Classic/NG, at 65t the Classic was 154kts at F30. Also Cat C.............. More chance of an over-run in a Classic? 4 kts faster than an 800.

737-700 at 65T is 141kts Flap 30. The extra '8' knots, as I said, for tail-strike avoidance.

** The old ICAO categories were Cat C Vref 115-160, so I guess that decided it? I think the 800 at MLW would still be Cat D, though.

[barkingmad]

“I never knew how it was kept as Cat C...”

“Boeing has obtained.....”.

So what were they up to?

I will dig out the tailstrike pitch attitudes when next access to the manuals and quote as best I can from the -800 details.

[Boac]

See update to post #16.

[barkingmad]

XLs -800 manual quotes CatC as 121-140 thereafter Cat D.

Next weekend I will trawl the Classic to NG -800 differences course and attempt to clarify.

I do recall the -800 was subjected to airflow modifications designed to inprove both takeoff & landing performances and was given the ‘SP’ tag as a result.

[Boac]

I think you will find the 'Cat C' you quote is PANS-OPS, but I reckon the 737 was 'certified' under ICAO (115-160). It is going to depend on whether the approach chart shows ICAO or PANS-OPS (or, of course, TERPS) minima for circling. Just glad I do not have to wrestle with this still!

The 'PANS OPS' categories arrived, I think, after you and I quit, but appear to be the same as TERPS.

These two pages may help?
Circling: https://www.skybrary.aero/index.php/Cir ... d_US_TERPS
Approach Categories: https://www.skybrary.aero/index.php/App ... gorisation

It is a case of checking the plate, as I said. The Australian Astraeus TC (I mentioned elsewhere) tried to persuade me, on an ETOPS LIne Check to Newfoundland, that I could circle under ICAO.................. - I passed the check