F100 - Overshot Runway at Newman Airport (9/1/2020)

[Saintly]

For those who may have had family/friends on this flight, this was on Twitter a short time ago "Newman Airport this morning, looks like the plane failed to stop, this is at the end of the runway"

Aircraft is an F100, aircraft registration is VH-NHY, flight number is QF2650 (NWK2650). Flight was Perth to Newman.


Reference: https://t.co/Am3v8tKgip

[Chronic Snoozer]

https://cimg7.ibsrv.net/gimg/pprune.org-vbulletin/765x316/3c9b968d_d022_460a_a11f_9c874aa02014_a0f7097a3f36fc82edf3655 e0ae4a0ffc59fc8f4.jpeg

[YPJT]

That closure will really screw around what is usually a big crew change day for the mines

[Alice Kiwican]

Would have been interesting going into Newman I’d have thought considering the weather over the last 24 hours.

[Hoofharted]

Annnnd here they come - the experts are swarming.

[Transition Layer]

Posted without comment...wouldn’t want to be called an expert :bored:
https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1216x523/d98d8596_d284_4dc0_9624_2127b6f04ce6_ff58df6c2f2058ae8c18a56 f837cb4430a84cec5.jpeg

[WhyGen]

Somebody said to me once that the ABC rarely reports on anything that might paint Qantas in a bad light, and that they jump at opportunities to report on pretty pictures etc taken from a Qantas flight. I dismissed them as being paranoid.
Given that at the time of writing this, a potential aircraft accident wasn’t worthy of an article from the ABC, I wonder if perhaps they were right.

[geeup]

The photo didn’t look to bad but I’m no expert :)

[hillbillybob]

Somebody said to me once that the ABC rarely reports on anything that might paint Qantas in a bad light, and that they jump at opportunities to report on pretty pictures etc taken from a Qantas flight. I dismissed them as being paranoid.
Given that at the time of writing this, a potential aircraft accident wasn’t worthy of an article from the ABC, I wonder if perhaps they were right.

given this (https://www.facebook.com/watch/?v=2586341351579474) was hours ago...

[Chronic Snoozer]

Somebody said to me once that the ABC rarely reports on anything that might paint Qantas in a bad light, and that they jump at opportunities to report on pretty pictures etc taken from a Qantas flight. I dismissed them as being paranoid.
Given that at the time of writing this, a potential aircraft accident wasn’t worthy of an article from the ABC, I wonder if perhaps they were right.

You might be on to something. Compare it to the coverage of this incident https://thewest.com.au/news/perth/cobham-aviation-plane-crashes-into-light-tower-at-perth-airport-ng-b881276619z

Still nothing in The West at the moment. It would be extraordinary if an airline could suppress a story such as this.

[Global Aviator]

Where did the photo on here go???

[Chronic Snoozer]

https://www.airlineratings.com/news/qantaslink-flight-overuns-newman-airport-heavy-rain/

https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/626x541/screenshot_174_a31e72ea70cfbf554c893d5036a654ed8b536616.png
This one?

I guess GT is in the clear regarding his CL membership.

[FGD135]

Tyres don’t have infinite grip. We’re used to having all the grip available to retard the aircraft, but when a strong crosswind prevails during the rollout, a good amount of the grip is being used just to prevent the aircraft from drifting sideways.

So, there is reduced grip available to retard the aircraft. Wet runways, as we know, further reduce the grip.

[spleener]

Maybe a number of reasons- queue the usual suspects: Press on; Land long; Speed above the bug, Weather; Runway surface; Braking/ Reverser technique [OMG they're stowed!]; Mechanical failure or,,,, GT spilling his machiatto in the Captain's Lounge.
Guess we'll find out.
Good Luck to the Crew, could have been better, but could have been worse.

[Alice Kiwican]

Braking/ Reverser technique [OMG they're stowed!]; Mechanical failure or,,,,

Interesting that it looks like the crew put everything away after they came to a stop and then shut down. Everything looks nice and orderly.

But I’m no expert

[YendorB]

Wait. We ARE all experts here .... Well at least that's what the passengers believe/expect when they book their tickets
​

[The Bullwinkle]

Braking/ Reverser technique [OMG they're stowed!]; Mechanical failure or,,,,

Interesting that it looks like the crew put everything away after they came to a stop and then shut down. Everything looks nice and orderly.

But I’m no expert
Why is that interesting?

[Blueskymine]

I just feel really bad for the crew. It would have been a sleepless night last night with all sorts of demons present.

I would say get in touch with your EAP as soon as possible, or via the union services which is when your fees become the best investment in your career.

We are all human and fallible. But it breaks my heart to see the roo off the end of a runway.

But for the grace.

[bazza stub]

Interesting that it looks like the crew put everything away after they came to a stop and then shut down. Everything looks nice and orderly.

But I’m no expert

They could have popped the slides and disembarked onto a wing full of spoilers and turning engines I guess.

[Ex FSO GRIFFO]

So, any damage to the aircraft ?
Tyres, U/C legs ?
Crew, Pax ?

Cheers

[Duck Pilot]

From the photos it looks as though they have stopped in the RESA which shouldn’t be a problem.

The RESA is designed for situations exactly like this. If the aerodrome is Part 139 Certified, which I’m sure it is I expect that there has been no damage to the aircraft and all that would be required is for the aircraft to be towed back to the apron and maybe have a LAME do an inspection on the aircraft to release it back into service.

Given the weather conditions, the crew done a good job in the challenging conditions. Lessons to be learnt, certainly yes however it’s very unfair to only make judgment on the flight crew as their decision making would certainly have been influenced by commercial pressures.

Good outcome given the WX conditions in my opinion.

Someone mentioned talk to your union if the pilots are members, I second that!

[JoeTripodi]

Not sure how parking a jet in the dirt off the end of a runway after a failed landing can be classed as a good outcome

[wishiwasupthere]

https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/465x316/6e66f24a_1900_4cf3_a0f6_86d4294a4d3f_c0ff4ffdb42f573fe3ec128 f4c6bba4f1a9cdad5.jpeg


Not sure how parking a jet in the dirt off the end of a runway after a failed landing can be classed as a good outcome]

Could’ve been worse!:}

[Duck Pilot]

Doesn’t appear to be damaged.

More than likely why the crew didn’t elect to use the slides as it was probably only a very slow overrun into the RESA.

Pretty obvious that most commentators throwing their two bobs worth into here have absolutely no idea what a RESA is.

[Rated De]

A shame for Fort Fumble and its team of "angels" that the tail has the prominent brand emblazoned on it.

[airdualbleedfault]

I'm with you Joe Tripodi, the RESA is for emergency use not routine poor landings. Newman is about 200m longer than the full factored LDR for a F25 wet runway landing in the Dutch oven, whilst I don't know all the extenuating circumstances, parking a jet in the mud is most definitely not a good result and I'm pretty sure most of the inhabitants of BS Castle would agree :rolleyes:

[ifylofd]

From the photos it looks as though they have stopped in the RESA which shouldn’t be a problem.

The RESA is designed for situations exactly like this. If the aerodrome is Part 139 Certified, which I’m sure it is I expect that there has been no damage to the aircraft and all that would be required is for the aircraft to be towed back to the apron and maybe have a LAME do an inspection on the aircraft to release it back into service.

Given the weather conditions, the crew done a good job in the challenging conditions. Lessons to be learnt, certainly yes however it’s very unfair to only make judgment on the flight crew as their decision making would certainly have been influenced by commercial pressures.

Good outcome given the WX conditions in my opinion.

Someone mentioned talk to your union if the pilots are members, I second that!

Yes duck, we can be comforted by the fact that 'given the weather conditions'...... hang on, should an approach even have been commenced?
Out west they use the RESA all the time matey, RPT Cat A jet transport aircraft are always nudging into that area, no problemo. And we can be almost guaranteed that the Qantas group exert massive amounts of commercial pressure on their crews - can't we?
Maybe we should just await the formal investigation, I'm sure they will confirm that use of the RESA is perfectly OK for this type of operation.
Cheerio.

[Duck Pilot]

Never instigated that the RESA should be considered under any circumstances, however whatever occurred with regards to this incident obviously probably indicates that the RESA done it’s job.

To state that the RESA is used regularly indicates that some people are stirring the pot (particularly on this forum), or some pilot’s have absolutely no idea what the RESA is and what it’s purpose is.

Should it ever be used under normal circumstances, NO! However it was with a good outcome. Do RPT pilots ever plan on using the RFFS at every aerodrome they fly into everyday? Don’t think so! Same scenario.

[machtuk]

The biggest inconvenience is the muddy boots the pax ended up with! -)

[Capt Fathom]

The biggest inconvenience is the muddy boots the pax ended up with! -)

A normal day up there in the wet!

[Alice Kiwican]

The biggest inconvenience is the muddy boots the pax ended up with! -)

Looks like they didn’t have far to walk off the aircraft and straight onto the buses!

[knackered IV]

It's interesting because they still had the presence of mind to complete the required actions after what would have been a rather unsettling experience. A good quality to have for a pilot.

[geeup]

Did they leave the crew in Newman?

Assume the airport is still closed

[The Banjo]

Is the runway grooved? Not clear from the supplied data.
If it is grooved, what is the maintenance schedule to clean the grooving? When was maintenance last conducted? Are there drainage issues during heavy rain? Was it therefore contaminated (>3mm water)? Is so, is it documented?

[Car RAMROD]

No it’s not grooved.

[Alice Kiwican]

Did they leave the crew in Newman?

Assume the airport is still closed

Not sure about the crew but the airport re-opened yesterday or possibly Thursday night once they removed the aircraft from the runway. I am reliably informed it is parked safe and sound on the apron

[VH-MLE]

I know I'm stating the obvious, but it would have been an extremely challenging approach and landing for any pilot (in any aircraft) to say the least - 30+ kts of gusting crosswind (& associated turbulence & IAS fluctuations), together with low cloud & low vis. It doesn't get any more difficult than that except perhaps in the same conditions at night...

My thoughts are with the crew well & truly...

VH-MLE

[Bend alot]

A normal day up there in the wet!


In the wet????NEWMAN CLIMATE SUMMARYThe Newman lies on 546m above sea level Newman's climate is a desert one. There is virtually no rainfall all year long in Newman.

[Xeptu]

In the Wet !!!!! That's about the only unusual thing in Newman. The brakes aren't fantastic in the F100 before you start when she's heavy, combined with idle thrust reverse and the possibility of standing water on the runway, I can only empathise with that sinking feeling you get when you know and in this case, still a bit quick when the runway end arrives. No damage done, good on you for all the right things you did once you knew. Don't worry about those slagging off, as we say they are those that have and those that will.

[Rated De]

This post in no critique of the individuals involved, rather more of a post about mine procurement.

Qantas have spent a lot of time and energy to convince the traveling public that contractors and subsidiary aircraft and crew are interchangeable. (Again this is not directed at crew)
At least one big industrialist refuses the subsidiary "interchange" and insists on Qantas registered and Qantas crew operated aircraft: Mines are dangerous places, risk mitigation is a prime focus.

From sources in the industry, there may well be a review of Qantas "light" services being operated into mine sites that have been sold as Qantas to the companies concerned.

[Transition Layer]

Don't worry about those slagging off, as we say they are those that have and those that will.

Really? I wasn’t aware exiting the end of the runway onto the dirt was that common :hmm:

[Lead Balloon]

How do you know that they “slid” off the end of the runway?

[Transition Layer]

How do you know that they “slid” off the end of the runway?
Fair point. Post amended. It’s still not a common occurrence whichever way you want to describe it.

[krismiler]

Fokker build pretty solid aircraft, with the position of the rescue worker it’s difficult to observe any nose gear damage, however the aircraft appears to be in a normal attitude.

No doubt being in QF colours and transporting mine staff, the investigation will be very thorough. Expect restrictions on weather conditions, crew retraining and possible increased minimum experience requirements IF this was a factor.

[Capt Fathom]

Whilst Qantas want everyone to think that boarding a plane with a kangaroo on the tail is flying with Qantas..... Well I have news for you.

Perth to Newman is not the same as Sydney to Melbourne, or Brisbane to Mackay or Melbourne to Hobart The whole operation is a con. Buyer beware.

[KRviator]

Whilst Qantas want everyone to think that boarding a plane with a kangaroo on the tail is flying with Qantas..... Well I have news for you.

Perth to Newman is not the same as Sydney to Melbourne, or Brisbane to Mackay or Melbourne to Hobart The whole operation is a con. Buyer beware.So does that mean GT won't count this incident against Qantas' "Worlds Best Airline" rating? We wouldn't want him to lose his CL membership...:ouch:

[aussieflyboy]

Interesting that flights to Broome were all cancelled when the system passed nearby however with a near identical forecast no flights to any of the mine sites or Newman were cancelled.

Shows the pressure and influence that the Mines have on the airlines (not just QF).

[The Bullwinkle]

It's interesting because they still had the presence of mind to complete the required actions after what would have been a rather unsettling experience. A good quality to have for a pilot.

The implication from the original poster was that there was something unusual about the aircraft’s configuration!
As far as I can see, they’ve followed their SOP’s after the incident and there’s actually nothing interesting here at all.

[Car RAMROD]

Interesting that flights to Broome were all cancelled when the system passed nearby however with a near identical forecast no flights to any of the mine sites or Newman were cancelled.

Shows the pressure and influence that the Mines have on the airlines (not just QF).


Or there are procedures for avoiding “cyclones” (ie up near Broome), where the region might be in yellow or red alerts; but not for “ex cyclones” and their associated weather as there aren’t yellow or red alerts for ex cyclones.

Mines don’t put on too much pressure, not in my experience anyway. Especially if you pull the safety card. Been there done that, they didn’t (and wouldn’t) complain.

[Arthur D]

This post in no critique of the individuals involved, rather more of a post about mine procurement.

Qantas have spent a lot of time and energy to convince the traveling public that contractors and subsidiary aircraft and crew are interchangeable. (Again this is not directed at crew)
At least one big industrialist refuses the subsidiary "interchange" and insists on Qantas registered and Qantas crew operated aircraft: Mines are dangerous places, risk mitigation is a prime focus.

From sources in the industry, there may well be a review of Qantas "light" services being operated into mine sites that have been sold as Qantas to the companies concerned.

No indictment of the crews involved.... but thanks to your little ‘indiscretion’ earlier this week, the real pilots will take it from here thanks......

Love to know your source Rated? Or were you just wishfully stroking your epaulets and salivating at the thought of another stripe courtesy of Link, aka ‘light’s’ stuff up? I suspect the correct spelling is sauce and it refers to the mess you made.

All for one and one for one eh....

[YendorB]

Whilst Qantas want everyone to think that boarding a plane with a kangaroo on the tail is flying with Qantas..... Well I have news for you.

Perth to Newman is not the same as Sydney to Melbourne, or Brisbane to Mackay or Melbourne to Hobart The whole operation is a con. Buyer beware.

What are you implying? That just because someone got through a HR interview with Main line that they are immediately a better pilot? That the training is better? Standards higher? Maintenance?
Getting paid more and flying around with your nose in the air doesn't mean S#it.
There are going to be weak links in every chain. Human mistakes will happen, minor and major, Mainline and subsidiary.
​​​​

[FGD135]

The brakes aren't fantastic in the F100 before you start when she's heavy, combined with idle thrust reverse and the possibility of standing water on the runway ...Why only idle reverse? Is the F100 incapable of more than idle?

Inappropriate use of reverse thrust was a factor in the QF1 overrun at Bangkok in 1999.

[knackered IV]

It's not uncommon to see everything left hanging out after an incident like this. Sure, as you say they're supposed to put it all away, but the original poster's touch of sarcasm may have been lost on you.

[ifylofd]

A snippet of wisdom from the West Australian that the Airline Ratings guru has penned.
Wow.
Was it 'well within QLink limits'? Interesting. Can anyone clarify from the Q group?
Was the approach commenced within required AIP limits?
Was it inside aircraft manufacturer recommended limits? (Fokker drivers?)

GT is drinking as usual from the Q coolaid - and clearly still cannot contribute a concise, unbiased, objective honest piece of so called journalism to save himself. What a joke.
Would this plane spotting ex baggage handler even have the slightest clue as to what 'the weather was bad at time of landing' even means? What does it mean? A disgrace that news publications (print) and tv networks succumb to and use such trash sources to report to the masses.

Clearly the ATSB have no use here, as GT is on the job as usual.
(info gleaned so far is Flap 25 landing, approach speed 160 knots)


It is understood that while the weather at the time of landing was bad it was well within QantasLink limits.

[-41]

Why only idle reverse? Is the F100 incapable of more than idle?

Inappropriate use of reverse thrust was a factor in the QF1 overrun at Bangkok in 1999.

Structural stress on the tail ?

You can use max reverse - if stopping solution / reject requires, with a restricted zone 57-75%N1 you can’t spend more than two seconds in without a fan inspection, so the Fokkers are normally idle reverse.

[Monopole]

Structural stress on the tail ?

You can use max reverse - if stopping solution / reject requires, with a restricted zone 57-75%N1 you can’t spend more than two seconds in without a fan inspection, so the Fokkers are normally idle reverse.

You can’t be in that range of 57 to 75% for two seconds but full reverse would normally pass through that range.. Max reverse does not require a fan blade inspection. The AoM calls for engineering to be notified and that is all.

In any case, if I saw the end of the runway coming up I’d be pulling that reverse lever off the hinges..

[krismiler]

The safety standards mines apply are very high and demanding. Regular audits are carried out on air service providers and contracts terminated when expectations aren’t met.

I remember a case where a Bandit hit a kangaroo on landing, this resulted in the strip being fenced and an inspection having to be carried out prior to any aircraft arriving, with the patrol vehicle remaining at the airport on standby whilst the flight turned around.

[CurtainTwitcher]

Newman is about 200m longer than the full factored LDR for a F25 wet runway landing in the Dutch oven, whilst I don't know all the extenuating circumstances, parking a jet in the mud is most definitely not a good result and I'm pretty sure most of the inhabitants of BS Castle would agree :rolleyes:

Interesting, the relatively slender margin of the "black and white" wet landing distance assessment. As the FAA have now discovered, black and white factoring isn't so clear cut and won't protect you. Highly relevant is the FAA SAFO 19003 Subject: Turbojet Braking Performance on Wet Runways (https://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2019/SAFO19003.pdf).

In a nutshell, the FAA are saying you need to add 30 to 40% factoring, not 15%. We haven't even begun to scratch the surface of even moderate rainfall on ungrooved runways, should be considered contaminated for braking action. Heavy rainfall is defined as >50+ mm in the last 24 hours by the World Meteorological Organisation (http://severeweather.wmo.int/raindoc.html).

I do also note that the BOM rainfall figures for Newman on the 9th Jan indicated 70+ mm of rainfall between midnight and 0900 and 140+ mm in the previous 24 hour period. The ATSB incident status page (https://www.atsb.gov.au/publications/investigation_reports/2020/aair/ao-2020-002/) indicates the incident occurred at 0723 WAST, the BOM observations are posted below with the rainfall since 0900 in the far right column.

Unfortunately, all too predictable over-runs in similar circumstances on short wet ungrooved runways will continue to occur until the operators start taking the SAFO recommendations into account and increase factoring during arrival periods of moderate to heavy rainfall.






https://cimg6.ibsrv.net/gimg/pprune.org-vbulletin/1482x800/screen_shot_2020_01_12__efbe68783c3bf330d8cf5bb41554a3691347 3f71.png

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/1408x242/screen_shot_2020_01_12_2_38f3bddf6826b113331aae2998812f196ef 4c36d.png


BOM Mount Newman observations 09-Jan-2020, rainfall since 0900 far right Column

https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/1506x624/screen_shot_2020_01_12_at_4_00_14_am_69d66baae64f07288def5ec 850b37b3e407e4c7b.png

[Alpine Flyer]

You can’t be in that range of 57 to 75% for two seconds but full reverse would normally pass through that range.. Max reverse does not require a fan blade inspection. The AoM calls for engineering to be notified and that is all.

In any case, if I saw the end of the runway coming up I’d be pulling that reverse lever off the hinges..

Apart from the N1 restriction more than idle is not used because it does not add that much the stopping effort. We only had to use it in case of contaminated runways.
As for stowing the reversers, pulling both reversers is the backup for liftdumper activation on the Fokker, and you certainly don't want those barn doors sticking out when evacuating.

If it's almost never wet there, I'd assume a bit of rain after a long dry spell would result in extra slippery conditions.

[Rated De]

Unfortunately, all too predictable over-runs in similar circumstances on short wet ungrooved runways will continue to occur until the operators start taking the SAFO recommendations into account and increase factoring during arrival periods of moderate to heavy rainfall.



All too much an impact on the commercial viability.

[ifylofd]

Apart from the N1 restriction more than idle is not used because it does not add that much the stopping effort. We only had to use it in case of contaminated runways.
As for stowing the reversers, pulling both reversers is the backup for liftdumper activation on the Fokker, and you certainly don't want those barn doors sticking out when evacuating.

If it's almost never wet there, I'd assume a bit of rain after a long dry spell would result in extra slippery conditions.

Alot of built up rubber deposits on that runway, and no grooving as has been noted.
The question will need to be asked of the airport operator and whether they have maintained the runway surface (rubber removal) IAW international recommendations WRT aircraft movement rates etc.

[Buttscratcher]

CurtainTwitcher, the Wet factor we use in Australia is 1.92%
So, with reference to that, WTF is your point?

[Blueskymine]

CurtainTwitcher, the Wet factor we use in Australia is 1.92%
So, with reference to that, WTF is your point?

Yes for dispatch.

In flight we use 15% which is what autobrake, flap and reverse thrust usage is based on.

[FGD135]

If there was any aquaplaning, it must have been minimal and not to all tyres simultaneously. If there had been significant aquaplaning, the strong crosswind would have caused major problems with directional control. It appears there were no such problems with directional control.

[Buttscratcher]

Yes for dispatch.

In flight we use 15% which is what autobrake, flap and reverse thrust usage is based on.

indeed, and thanks for pointing that out, but airdualbleedfault wrote
Newman is about 200m longer than the full factored LDR for a F25 wet runway landing.

So one would assume 'Full Factor' to be Dispatch at 1.92%

[FGD135]

In flight we use 15% which is what autobrake, flap and reverse thrust usage is based on.
But does the degree of autobrake and reverse thrust vary, or are the same values always used?

And if the landing performance required satisfied the despatcher, was he assuming the same values for reverse thrust and autobrake as were actually used?

[exfocx]

I think some crew here are confused about 1.67, 1.92 and the 15% buffer for wet runways, or so it appears by my interpretation of comments made. I don't believe pre dep or inflt has anything to do with the above figures. 1.92 is based on the ACTUAL dry rwy ldg distance, giving you your REQUIRED wet rwy ldg distance.

If you go to your landing distance tables for what ever LDG WT, Temp, El etc figures you'd like (dry rwy) and then divide that number by 1.67 you should have the actual ldg distance acquired via the manufacturers flt testing. Multiply that actual ldg distance by 1.92 and you get your required wet rwy ldg distance. If you multiply your required dry ldg distance (fully factored 1.67) by 15% you will get the same distance. I've done this for my type.

Again, 1.92 is the factor used for the actual dry rwy ldg distance (not factored), the 15% is the buffer on the required dry rwy distance (factored) that gives you your required wet rwy ldg distance. It's the same!

[Blueskymine]

But does the degree of autobrake and reverse thrust vary, or are the same values always used?

And if the landing performance required satisfied the despatcher, was he assuming the same values for reverse thrust and autobrake as were actually used?

No idea, I don’t work for network. I fly something a little larger.

Obviously though a crew isn’t going to land if the performance figures indicate it won’t work. On the airbus we used flysmart for every landing. On the Boeing the OPT. That is what autobrake and reverse thrust usage is based upon. Along with the preferred exit.

What do network use?

[CurtainTwitcher]

11.2 When determining the maximum weight for landing of a jet-engined aeroplane of maximum take-off weight greater than 5 700 kg for the purpose of subparagraph 5.1 (a), the landing distance required is 1.67 times the distance required to bring the aeroplane to a stop on a dry runway or, if actual landing distance data is supplied by the aircraft’s type certificate holder, 1.15 times the actual landing distance.
Civil Aviation Order 20.7.1B - Aeroplane weight & performance limitations - Aeroplanes above 5 700kg - All operations (turbine & piston-engined) (02/12/2004) (https://www.legislation.gov.au/Details/F2014C01352/Html/Text#)
So one would assume 'Full Factor' to be Dispatch at 1.92%

You are assuming the the operator does not use actual landing distance data, and thus would require the 1.92 times dry distance factoring for dispatch. I am basing my comments on assumption the operator would be using the actual wet landing distance data and thus only requires a 1.15 factor.

The SAFO and my comments apply to the 1.15 actual landing distance case. My point is that on a smooth runway (not grooved and not PFC) the 1.15 factor for actual landing distance data has proved to be inadequate for even moderate rainfall intensity. Thus, for a smooth runway consider the possibility that the runway friction performance will be similar to a contaminated one, even in moderate rain according to the SAFO.

It is difficult to pin down the exact definition of moderate and heavy rain, moderate rainfall is in the range of 0.5mm (lower bound) to between 4.0 & 7.6mm (upper bound) per hour, dependant upon who is defining it. The Newman reported rainfall was 3.6mm of rain between 0700 and 0730, thus a rainfall intensity of around 7.2mm per hour, at the upper band of the least conservative moderate range. Combined with the previous 120mm in the previous 21+ hours there is a high probability that drainage from the runway would be poorer than a single intense shower, and thus braking action is likely to be significantly worse than the wet actual landing distance certification data assumes.

Of course if the operator is not using actual landing distance data, my arguments are invalidated.

There isn't any need to be rude, we are all here to learn and avoiding becoming the subject of an accident report ourselves. Crews are still being caught out on wet runways, caution is warranted and a good knowledge of the issues and limitations of the landing distance calculations is essential, particularly when the runway is short. There have been many previous near misses and accidents recently with wet runway excursions / near misses. Off the top of my head, Jacksonville 738 accident (https://ntsb.gov/investigations/Pages/DCA19FA143.aspx) (the crew ignored multiple heavy rainfall reports at the field), SWA at Burbank (twice) and the Virgin Christchurch reduced braking effectiveness (https://www.atsb.gov.au/media/5774950/ao-2015-046-final.pdf) (excellent report covering reduced friction with just a small portion of the runway contaminated in light rain causing a very close call for the crew).

A close read of SAFO 19003 (https://www.faa.gov/other_visit/aviation_industry/airline_operators/airline_safety/safo/all_safos/media/2019/SAFO19003.pdf), pondering it's implications, and then considering the last 10 minute rainfall on the AWIS or TTF will help keep you out of the mud.

[The Banjo]

Some company manuals suggest that if landing on an ungrooved runway in heavy rain it be treated as contaminated with poor braking. ie don't land until the weather passes. Wonder if Network has that info in the books.

[YendorB]

None of the landing distance calculations are valid if the crew elected to land outside the touch down zone instead of going around.....
Speculation

[Monopole]

None of the landing distance calculations are valid if the crew elected to land outside the touch down zone instead of going around.....
Speculation

Or landing with a configuration that doesn’t put all the aces up your sleeve.

[The name is Porter]

I've got a few mates flying the F100, it would make it a whole lot easier if PPRUNE had a register of who fly's what and when something like this happens, each person on the F100 PPRUNE register could post a reply saying:

It wasn't me.

[73qanda]

CurtainTwitcher is pushing good gen.
If you’re currently flying jets I reckon you read his post #48 again. Read the SAFO. Think about what it means practically at the ports you go to. When would you tell ATC you want to hold while the weather goes through? Under what circumstances will you pull the pin and divert?
After that, go through all the company documentation referencing the SAFO and how it will impact your decision making .......the company highlighted it and ensured all pilots understood the gravity of the SAFO yeah? Your Training Department must have bombarded you with emails and powerpoints about how the safety factors you use every day are inadequate under some circumstances yeah? Surely......No?

[Stationair8]

According to Flightaware, the aircraft was flown back to Perth today.

[Buttscratcher]

Righteo, so, given all of this knowledge, I'm assuming that you blokes (Curtain & 73 ) would have not departed Perth, or Diverted to an applicable Alternate?
Fair call, but what's your cut-off criteria for RF then?
Perhaps you have some applicable weather procedure or criteria to derive your Contaminated RWY no-go from the METAR alone?
I'm not trying to be recalcitrant, but if you have a workable method of ascertaining Contamination levels and braking action at uncontrolled Airports, please share.

[VH-MLE]

Sorry “Rated de” but your earlier post appears to imply that there’s Qantas pilots & everyone else. I’m not sure if that was your intent but that’s certainly how it came across to me...

[CurtainTwitcher]

Righteo, so, given all of this knowledge, I'm assuming that you blokes (Curtain & 73 ) would have not departed Perth, or Diverted to an applicable Alternate?
Fair call, but what's your cut-off criteria for RF then?
Perhaps you have some applicable weather procedure or criteria to derive your Contaminated RWY no-go from the METAR alone?
I'm not trying to be recalcitrant, but if you have a workable method of ascertaining Contamination levels and braking action at uncontrolled Airports, please share.

I look at the METAR last 10 minute rainfall and rainfall since 0900 to give me a ballpark idea of the rain system. if you use 4.0mm per hour as the upper limit of moderate, just divide that by 6 (6 ten minute period per hour) is 0.7mm, If I am going somewhere short and ungrooved/non-PFC, I plug in RCAM Runway Condition Code 2 in the OPT.

If it is grooved/PFC I uses 7.6mm per hour, this equates to 1.2mm in the last 10 minutes before I plug in code 2. I then assess LDA vs required. If I can't do it, I hold then divert. I have diverted from a very short runway in the Whitsunday's (despite the CAVOK forecast, subsequent METAR showed 15mm of rainfall had occurred during the hour that covered our arrival period, tower reported visibility was between 900 and 1900m vis). At non-tower ports, you use the AWIS last 10 minute figure that is literally updated instantaneously, and is more useful that the slightly stale METAR.

Runway excursions globally are the #1 cause of accidents according to ICAO (https://www.icao.int/safety/iStars/Pages/Accident-Statistics.aspx). We are extremely fortunate in Oz, good weather, good runways so we don't think about it much. It rarely comes into play, but when it does, it's nice to be able to have in your back pocket, a plan of how to think about it. How many over-runs does it take to wreck a career? Honestly, you would be lucky to have to divert once every five or 10 years, but that diversion may CYA.

Extremely easy to justify to a manager why you couldn't land, as documented in the arrival period METAR rainfall. I would be extremely surprised if every RPT ops manual didn't have a statement along the lines of "don't land in heavy rain" so you are bulletproof, and your pax & crew are safe.

To me, the Virgin Christchurch reduced braking effectiveness report (https://www.atsb.gov.au/media/5774950/ao-2015-046-final.pdf) gives you an idea of a real world scenario where the crew had limited time to make a choice of runways with incomplete information late in the flight with runway changes and how it can spin out of control pretty quickly and you find the end of the runway coming up very quickly. They stopped 5m before the end of the runway. Kudos to the crew for reporting it, this is a classic case study.

The captain assisted the FO with manual braking. Both crew reported that they could feel
the rudder/brake pedals ‘pulsing’, which indicated the antiskid system was operating. The crew
elected to keep reverse thrust deployed to assist with braking.

The FO reported that he was focusing on the red runway end lights and noticed the aircraft drift
slightly right, which he then corrected to bring the aircraft back onto the centreline. The captain
reported that, when reverse thrust was stowed near the runway end, there was enough surface
water on the runway to create a wall of spray. The FO reported that the aircraft came ‘slowly
sliding’ to a stop about 5 m from the runway end lights. The aircraft was then taxied to the
terminal.

It's not the first time I've heard of the "wall of spray" from the reverse thrust after the aircraft is stopped very close to end of the runway, the one told to me was Perth RWY24. Quite a few very close calls over the years that don't get talked about or reported,

If you look at Europe or the US, they are dealing with this frequently and have a much better understanding of the issues. EASA has an extensive report A STUDY OF RUNWAY EXCURSIONS FROM A EUROPEAN PERSPECTIVE (https://www.skybrary.aero/bookshelf/books/2069.pdf).

Airbus are now offering an A320 FMS upgrade mods to enable a real time braking performance: Braking Action Computation Function’ (BACF)” (https://www.navblue.aero/product/bacf/) derived as an objective figure to report, rather than a Pilot assessment. That shows that for a lot of the world, this is actually a big deal.

It's the silent sleeper issue, just waiting to catch the unlucky and unwary.

[73qanda]

Righteo, so, given all of this knowledge, I'm assuming that you blokes (Curtain & 73 ) would have not departed Perth, or Diverted to an applicable Alternate?
I have no idea what I would have done in the Newman situation because I don’t know anything about it. For all I know it wasn’t even raining when they touched down and a technical failure reduced braking effectiveness. All I’m saying is that the information Curtain posted is very important, potentially life saving information and if you are charged with the responsibility of keeping the flight safe then it is worth your time to read it and think about how you will apply it in a practical sense.
My experience is that I have always departed when dispatch criteria have been met but always plan the fuel to hold or divert if heavy rain is possible. I’ve held several times until the rain has eased at major ports but have yet to divert due heavy rain. My interpretation of all the info available only matters on my flights though. What is important to you and your passengers is your interpretation of it. If it was not subjective your OPT could decide ‘land’ or ‘don’t land’, but it is subjective and the decision is a human one.
Fair call, but what's your cut-off criteria for RF then?
I’m fortunate in that I’m comfortable with what my company has decided regarding RF.
Perhaps you have some applicable weather procedure or criteria to derive your Contaminated RWY no-go from the METAR alone? No I don’t, ( you could develop one if you wanted). I use a combination of info from the metar, atis, and conversations with the Tower Controller and my own knowledge of the runway to be used.
I'm not trying to be recalcitrant, but if you have a workable method of ascertaining Contamination levels and braking action at uncontrolled Airports, please share. Sorry but I just have my own personal assessment based on my own experience. What I am hoping comes from Curtains post is that pilots add a layer of conservatism on top of what their iPad says when there is significant water around. The FAA has suggested we do, but even they can’t give more specific guidance than that. If you wanted to you could set your own factors. Ie,” if there is heavy rain at the field I will add a 30% Safety margin instead of a 15% Safety margin. If that can’t be met I will hold or divert. “
Thats not what I do but it could be a starting point for the first year or two of command if you thought it was sensible.

[ScepticalOptomist]

I look at the METAR last 10 minute rainfall and rainfall since 0900 to give me a ballpark idea of the rain system. if you use 4.0mm per hour as the upper limit of moderate, just divide that by 6 (6 ten minute period per hour) is 0.7mm, If I am going somewhere short and ungrooved/non-PFC, I plug in RCAM Runway Condition Code 2 in the OPT.

If it is grooved/PFC I uses 7.6mm per hour, this equates to 1.2mm in the last 10 minutes before I plug in code 2. I then assess LDA vs required. If I can't do it, I hold then divert. I have diverted from a very short runway in the Whitsunday's (despite the CAVOK forecast, subsequent METAR showed 15mm of rainfall had occurred during the hour that covered our arrival period, tower reported visibility was between 900 and 1900m vis). At non-tower ports, you use the AWIS last 10 minute figure that is literally updated instantaneously, and is more useful that the slightly stale METAR.


Thanks for sharing - very useful.

[neville_nobody]

The problem in Australia is numerous RPT aerodromes are CTAFs so there is no way of getting any sort of runway condition statement.

[Buttscratcher]

Very useful insights, fellas.
I like where you are coming from with the assessments, though I don't know what your company calls Runway Condition Code 2.
Boeing and 'Bus have 6 RWY condition surface options from which to choose inflight.
Once the RWY condition goes from Wet to Contaminated (above 3mm of standing water), operations are prohibited in most companies in Oz, as far as I remember.
So, it would be useful to apply the RF in a fashion similar to Curtain's procedure to figure out a Contaminated cutoff value.
The other percentages you are suggesting, though, isn't so flash.
Once a RWY has been assessed as Contaminated, then it's game over.

[George Glass]

Regional flying in Western Australian is the Wild West. No RFF. Few grooved runways. Metars not TTFs. GNSS approach if your lucky. Landing weight limited most of the time and limited alternates. Very limited ground support.Throw in a cyclone and Bingo! Some of the most challenging flying I’ve done in 20,000 hours. Stay safe out there people!

[73qanda]

Once the RWY condition goes from Wet to Contaminated (above 3mm of standing water), operations are prohibited.
My opinion is that it is important to be aware of what is good ‘classroom knowledge’ and what is good ‘operational knowledge’. ( and I imagine you are, I’ll just put this out there in case it helps someone or adds value to the conversation).It’s certainly handy to know that above 3mm of standing water is considered contaminated when you’re being tested in the classroom, but it is next to useless on an eight mile final when Tower says “ABC new ATIS Foxtrot issued, only change visibility 2500 meters in rain, wind 270 five knots cleared to land”. The Tower controller doesn’t know if there is more than 3mm of standing water on the runway and neither do RFS or the bird man. So at this point the decision is completely human. No book or computer can tell you ‘land’ or ‘don’t land’ because the inputs to the equation are unknown. If you are 60T onto a 3000m runway you can probably safely decide to continue. If you are 66T onto an 1800m runway the decision is a very important one. How each pilot decides to build in a conservative element is up to them to figure out and apply. Curtain has given his example which I’m sure would work very well for many. My way of deciding is a bit different ( it involves excess landing distance available) but it works for me in the heat of the approach which is what matters to me. If you develop a method that works for you and allows for a conservative decision when you are under pressure then you can refine it over the years. ( I’m going to play with CT’s method as a kind of two-step approach and see how that goes).
Once a RWY has been assessed as Contaminated, then it's game over. Unless there is snow on the runway, who is going to assess it as contaminated in this part of the world? Like I said before, nobody knows if there is more than 3mm of standing water on the runway and I’ve never heard ATC declare that the runway is now contaminated. You’ll get visibility and precipitation type and if you’re very lucky they’ll tell you that the rain is heavy ( in which case I’d just hold til it went through).
Anyway, I’ve learnt something so thanks for that.
If any Tower controllers read this can they report back observed precipitation rates and corresponding visibility’s? I understand that there will be variables such as humidity etc that will bring varying results but it would still be helpful to get a few examples.
Cheers

[George Glass]

73qanda, there is no tower. That’s the point. In this part of the world you’re on your own.

[George Glass]

I had the honour (????) of operating into YGIA and YSOL early on in their existence with an FO with no GA experience. Had a lot of trouble convincing him that a B737 was just an overgrown C402. It really was that basic. Don’t know how it got past the regulators...............
He said it was like landing on the moon ! LOL

[Global Aviator]

No idea, I don’t work for network. I fly something a little larger.

Obviously though a crew isn’t going to land if the performance figures indicate it won’t work. On the airbus we used flysmart for every landing. On the Boeing the OPT. That is what autobrake and reverse thrust usage is based upon. Along with the preferred exit.

What do network use?

What happens if someone puts the wrong figures in??? Flysmart or OPT I suspect like anything cowpoo in means cowpoo out...

[wishiwasupthere]

What happens if someone puts the wrong figures in??? Flysmart or OPT I suspect like anything cowpoo in means cowpoo out...

It should be picked up when you cross check the results.

[Awol57]

As a tower controller, we won't say anything about contamination. We will use damp, wet, water patches and flooded.

If there is a heavy shower approaching I will often say something but to be honest you can usually see it as well as, if not better than, us (particularly passing showers).

[topend3]

The problem in Australia is numerous RPT aerodromes are CTAFs so there is no way of getting any sort of runway condition statement.

Nothing to stop the airlines setting up a process with the aerodrome operator though.

[topend3]

73qanda, there is no tower. That’s the point. In this part of the world you’re on your own. The ARO would have done a serviceability inspection prior to this aircraft arriving. Be surprised if this isn't looked at by the ATSB re runway surface condition reporting.

[73qanda]

73qanda, there is no tower. That’s the point. In this part of the world you’re on your own.
Yeah sorry George, I understand what you’re saying. I got caught up in a generic kind of discussion that wasn’t specific to the Newman incident ( in my mind at least).
I’m sure it’s it’s own kind of interesting west of Adelaide. I just hope that we manage to e extract and promulgate all the learnings from this one.

[WINJA]

They could have popped the slides and disembarked onto a wing full of spoilers and turning engines I guess.
Nearly right, though the Fokker evacuation calls for flaps full down if evacuation required.
They just tidied her up...

[WINJA]

I guess we all assume the 'stable approach' criteria was met?

[MickG0105]

From today's The Australian:

The risky business of landing on wet runways
By BYRON BAILEY

Last week in Perth Airport, as I waited to board a Qantas flight, I heard a passenger address announcement that Newman Airport was closed and that passengers should contact their company to make arrangements to travel the next day. Cyclone Blake had passed through the Newman area previously and I assumed that was the cause.

Later, I saw on television the picture of a QantasLink aircraft, due to a slight overrun on landing, sitting off the end of the sealed Newman runway with its nose gear apparently bogged in the non-sealed surface. It was raining heavily.

Heavy rain presents a visibility problem when landing at around 200km/h and it also presents a braking action problem when landing, due to surface water on the runway.

A wet runway is defined as water up to a depth of 8mm. Over that it is defined as contaminated and manufacturers cannot guarantee adequate stopping performance.

The problem is hydroplaning (or aquaplaning) where — above a critical speed — the wheel is lifted off the surface and rides on the film of water, causing the plane to skid. The general formula for working out hydroplaning speed is nine times the square root of the tyre pressure. However, the Federal Aviation Administration recently reworked the formula due to some overruns. The dynamic (aircraft taking off) wheel-rotating hydroplaning speed was lowered slightly, but in the static hydroplaning landing case of stationary wheels the FAA reduced the formula for hydroplaning onset speed to about 7.5 times the square root of the tyre pressure.

This means for a typical jet with a tyre pressure of around 200psi and a landing speed of around 130 knots the pilots should, after a firm landing to break through the surface water to ensure tyre contact and wheel spin up, use lift dump and thrust reversers as soon as possible and then, when below the hydroplaning onset speed of around 100 knots, apply one firm brake application and let the aircraft’s brake antiskid system do its job.

Car drivers as well need to be aware that in heavy rain with tyre pressures of around 35psi, in the interests of safety, speed should be reduced, especially with under-inflated tyres.

Also, once hydroplaning starts and the wheels lock up, the skidding due to hydroplaning can continue down to a much lower speed.

Byron Bailey is a former RAAF fighter jet pilot and flew B777s as an airline captain.
My bolding.

[Global Aviator]

”Later, I saw on television the picture of a QantasLink aircraft, due to a slight overrun on landing, sitting off the end of the sealed Newman runway with its nose gear apparently bogged in the non-sealed surface. It was raining heavily.”

Hang on a minute... Even an armchair expert could see that there was not a lot of broken surface from the very first pic... However the aircraft rolled into the hard over run area does not sound anywhere near as dramatic.

[Chronic Snoozer]

It's a sad day when ex-military aircrew journalists can't get their reporting right or let errors slip through the editor. "Apparently bogged"?? In the only picture I've seen, the one earlier in the thread, the nose gear is obscured by a firie standing in the foreground. It is 'apparently' raining however.

[MickG0105]

In the only picture I've seen, the one earlier in the thread, the nose gear is obscured by a firie standing in the foreground.
That picture appears to be a still taken from a short video posted to social media by ABC Perth. Between 0:14 - 0:17 sec you get a pretty good look at the nose gear. It doesn't appear to have broken the surface of the RESA.

[Noeyedear]

The following is from the Aircraft Operating Manual for a similar weight and configuration aircraft from a different manufacturer. I've added the bolding for emphasis. One of the previous posters indicated that as ATC, they simply report the presence of standing water.



I offer this purely to ask, was similar guidance in the F100 manuals, if not, why not; and, why hadn't CASA picked up on it, or the Company SMS?



The pilot's can only do what they're trained to do.





Without measured runway water depths, on runways with standing water, use the following information to determine the possibility of hydroplaning:


Rain reported as light - Dynamic hydroplaning unlikely, but viscous and reverted hydroplaning possible.

Rain reported as moderate - All types of hydroplaning are possible. Smooth tires will likely hydroplane.

Rain reported as heavy - Hydroplaning will occur.

[Arctaurus]

A wet runway is defined as water up to a depth of 8mm

I thought a wet runway was water to a depth of 3 mm ???

Mick is right - BB redefining global standards

[itsnotthatbloodyhard]

This means for a typical jet with a tyre pressure of around 200psi and a landing speed of around 130 knots the pilots should, after a firm landing to break through the surface water to ensure tyre contact and wheel spin up, use lift dump and thrust reversers as soon as possible and then, when below the hydroplaning onset speed of around 100 knots, apply one firm brake application and let the aircraft’s brake antiskid system do its job.

I guess we shouldn’t be using autobrakes on wet runways, then. :confused:

[CurtainTwitcher]

The full report has just been published: Runway overrun involving Fokker 100, VH-NHY Newman Airport, Western Australia, on 9 January 2020 (https://www.atsb.gov.au/media/5780094/ao-2020-002-final.pdf).

CASA have published a new instrument: New performance (https://www.casa.gov.au/sites/default/files/caap-235-05-new-performance-provisions-cao-2071b-cao-2074.pdf)provisions for CAO 20.7.1B and CAO 20.7.4 (https://www.casa.gov.au/sites/default/files/caap-235-05-new-performance-provisions-cao-2071b-cao-2074.pdf)October 2020. Lots of quiet maneuvering behind the scenes to retrospectively cover butts. Those who should have know were asleep at the wheel here, both CASA and operators. The FAA have banging on about it for years. If I could figure it out, why couldn't the regulator and the various Flight Tech departments?

Fortunately this was a non-fatal outcome and CASA had the good sense to realise things needed to change.

[Capn Bloggs]

Curtain Twitcher, that's not a new instrument, it's only a CAAP. Essentially, nothings changed except that there is now a para on "very wet" landings.

IMO the fundamental flaw in all of this was the LDR change from +67% of demonstrated/actual to +15% just because you're now airborne (11.2 and it's Note). A bit like the old 45min FR for planning verses 30min FR after you get going. Illogical.

15% was always going to cause grief, and will continue to do so until somebody steps up and says the current rules are "an ass" and slaps some additional buffers on. Personally, if I don't have full preflight factors (1.67 or 1.92), even when airborne, I'm not doing it unless I'm in dire straits.

[Lead Balloon]

Capn Bloggs is correct. Neither CAO 20.7.1B nor CAO 20.7.4 has changed since 2014. The heading of the CAAP is, therefore, now misleading: "New performance provisions for CAO 20.7.1B and CAO 20.7.4"

The CAAP states that the most recent changes to it were in October 2020. The CAAP states:This [2020] revision has been issued to incorporate advice regarding the legislative safety factors used with actual landing distance performance data from the
latest FAA guidance material.The "legislative safety factors" are what they are and haven't changed, and no amount of "advice" will change them.

[morno]

Curtain Twitcher, that's not a new instrument, it's only a CAAP. Essentially, nothings changed except that there is now a para on "very wet" landings.

IMO the fundamental flaw in all of this was the LDR change from +67% of demonstrated/actual to +15% just because you're now airborne (11.2 and it's Note). A bit like the old 45min FR for planning verses 30min FR after you get going. Illogical.

15% was always going to cause grief, and will continue to do so until somebody steps up and says the current rules are "an ass" and slaps some additional buffers on. Personally, if I don't have full preflight factors (1.67 or 1.92), even when airborne, I'm not doing it unless I'm in dire straits.

Are you telling me, that you need 1.67 times that of a buffer already placed upon flight testing, to land your aeroplane? :confused:

Maybe in the days of pencil and ruler performance calculations, but we’re dealing with EFB’s where you can do things like selecting how wet the runway is if your company has been smart enough to make those an option. The calculations coming out now should be very accurate. Why you’d need to place a 67 or 92% buffer on that is beyond me!

[Roj approved]

Are you telling me, that you need 1.67 times that of a buffer already placed upon flight testing, to land your aeroplane? :confused:

In this case they needed slightly more😂😂😂

🎩 🧥 🚪

[kitchen bench]

Are you telling me, that you need 1.67 times that of a buffer already placed upon flight testing, to land your aeroplane? :confused:!

Maybe you can fly like a test pilot but not all of us are that good. That's why there are margins.

[morno]

Maybe you can fly like a test pilot but not all of us are that good. That's why there are margins.

I understand why there are margins buddy, and 15% is a pretty good margin. But seriously, if you can’t land in 167% of the distance that they worked out in flight testing, maybe it’s time to go back to flight school. :rolleyes:

[Capn Bloggs]

Are you telling me, that you need 1.67 times that of a buffer already placed upon flight testing, to land your aeroplane?
No. 1.67 times the ACTUAL LANDING DISTANCE.

I understand why there are margins buddy, and 15% is a pretty good margin.
In your opinion.

Just out of interest, what value is the buffer you talk about?

[kitchen bench]

I understand why there are margins buddy,

I'm not your buddy nor do I think I'd be worthy of being so from your exalted position - even if it be self appointed. Perchance I was worthy, I wouldn't want to be.

[neville_nobody]

I understand why there are margins buddy, and 15% is a pretty good margin. But seriously, if you can’t land in 167% of the distance that they worked out in flight testing, maybe it’s time to go back to flight school.

Those figures are off the Maximum Braking performance of the aircraft which you couldn't realistically use every sector as you would scare the pax and burn through parts. We're talking a carrier landing followed by standing on the brakes to a complete stop.

The real margin on 'normal' landing performance is much less than that as noone ever lands at maximum braking. Hence the 15% figure.

[Buttscratcher]

http://www.quickmeme.com/img/7e/7ea9100cd5ba8ab38c45f04ff2b13aff275518ab66f8ea7a3377bb9a9413 d9c8.jpg

[morno]

Those figures are off the Maximum Braking performance of the aircraft which you couldn't realistically use every sector as you would scare the pax and burn through parts. We're talking a carrier landing followed by standing on the brakes to a complete stop.

The real margin on 'normal' landing performance is much less than that as noone ever lands at maximum braking. Hence the 15% figure.

Ok, I’m not familiar with the workings of Fokkers performance calculations, but let’s use Airbus as an example, I’m very familiar with that.

Airbus has flysmart. In flysmart, you can select the surface condition, the auto brake settings, whether reverse is being used, lots of very specific information.

It punches out a calculation, and then it shows you the margin on top of it.

Why, when there is such specific information in the calculations, would I need to then throw on 67% more distance? You’re either in the touchdown zone or you’re not. And if you’re not, you go around.

It makes me worried to think people think you can’t land in the distance specified in the manuals :hmm:

We’d never land in a lot of places if we needed such massive margins each time.

[Buttscratcher]

Thanks morno.....finally some sense prevails!

[Rhodes13]

Morno the 67% only applies at the pre flight planning stage. Once airborne you only add 15% to the operational landing distance (Actual landing distance plus 7 seconds of air distance) as a safety buffer.

[Capt Fathom]

Ok, I’m not familiar with the workings of Fokkers performance calculations

Now we are getting somewhere!

[morno]

Morno the 67% only applies at the pre flight planning stage. Once airborne you only add 15% to the operational landing distance (Actual landing distance plus 7 seconds of air distance) as a safety buffer.

Aware of this. But a previous post was critical of the fact that it’s only 15% in the air, and that they still factored 67%. And 7 seconds of air distance, I didn’t know that, interesting!

Fathom, I was never talking about performance for the Fokker, I was talking about performance in general.

[Lead Balloon]

Isn't the key difference the bit I've underlined?11.2 When determining the maximum weight for landing of a jet-engined aeroplane of maximum take-off weight greater than 5 700 kg for the purpose of subparagraph 5.1 (a), the landing distance required is 1.67 times the distance required to bring the aeroplane to a stop on a dry runway or, if actual landing distance data is supplied by the aircraft’s type certificate holder, 1.15 times the actual landing distance.

[neville_nobody]

Why, when there is such specific information in the calculations, would I need to then throw on 67% more distance? You’re either in the touchdown zone or you’re not. And if you’re not, you go around.

You're confusing pre dispatch with post dispatch. Post dispatch you are using whatever approved system you have available which may even have the 15% factor built in them.

The pre dispatch 1.67 figures are off the maximum braking performance of the aircraft. You couldn't factor 67% on a normal everyday landing performance you'd need 3500m+ everywhere you went.

[Buttscratcher]

I think he knows that Nev.

Your post way back was just confusing...........like, freaking us all out, man.

[morno]

You're confusing pre dispatch with post dispatch. Post dispatch you are using whatever approved system you have available which may even have the 15% factor built in them.

The pre dispatch 1.67 figures are off the maximum braking performance of the aircraft. You couldn't factor 67% on a normal everyday landing performance you'd need 3500m+ everywhere you went.

Read the posts by Bloggs and Kitchen

[morno]

Curtain Twitcher, that's not a new instrument, it's only a CAAP. Essentially, nothings changed except that there is now a para on "very wet" landings.

IMO the fundamental flaw in all of this was the LDR change from +67% of demonstrated/actual to +15% just because you're now airborne (11.2 and it's Note). A bit like the old 45min FR for planning verses 30min FR after you get going. Illogical.

15% was always going to cause grief, and will continue to do so until somebody steps up and says the current rules are "an ass" and slaps some additional buffers on. Personally, if I don't have full preflight factors (1.67 or 1.92), even when airborne, I'm not doing it unless I'm in dire straits.

Referred Post

[Buttscratcher]

......yeah, and that messed with my fragile mind too, but I figured Bloggs may have just been drinking a lot before posting.

[neville_nobody]

There appears to be confusion about definitions. Have a look at Hamilton Island and tell me how anyone in an airliner can dispatch there with a 1.67 factor and what sort of performance is needed to make the factoring work.

[Lead Balloon]

The factor could be 1.92 for the 'dispatch' maximum weight!

I can't work out why s 11.1(b) of CAO 20.7.1B makes specific provision for the wet destination runway scenario for the 'dispatch' maximum weight but s 11.2 does not for the 'in air' calculation. If you know, before you take off, that the destination runway is or may be wet, the maximum take off weight has to be calculated on the basis that the landing distance required will be 1.92 times the distance required to land in the dry and, apparently, that requirement applies irrespective of whatever landing distance data has been supplied by the holder of the type certificate for the aircraft. However, once the actual destination conditions are known the factor changes to 1.67 or, in the case of an aircraft whose type certificate holder has supplied actual distance data, 1.15. Whattha?

If the actual conditions on arrival turn out to be wet as forecast, what magic changes the risk from one requiring a 1.92 factor to 1.67 or 1.15 factor in the same aircraft?

[Capn Bloggs]

The irony, Morno, is that your Flysmart (should) give you a 167% landing distance calculation for dispatch. :rolleyes:

[Capn Bloggs]

......yeah, and that messed with my fragile mind too, but I figured Bloggs may have just been drinking a lot before posting.
All I'm saying is that routinely landing with only 15% over the actual landing distance required ie 50ft over the fence to a max-effort full stop, is going to eventually end in grief.

[morno]

The irony, Morno, is that your Flysmart (should) give you a 167% landing distance calculation for dispatch. :rolleyes:

It does mate. And for dispatch that’s fine, but I’m sure as **** not going to use 167% while I’m in the air like you said you would.

[morno]

All I'm saying is that routinely landing with only 15% over the actual landing distance required ie 50ft over the fence to a max-effort full stop, is going to eventually end in grief.

In what aircraft? Are you saying every aircraft’s landing performance is predicated on max braking effort? Because you’re very wrong.

[StudentInDebt]

All I'm saying is that routinely landing with only 15% over the actual landing distance required ie 50ft over the fence to a max-effort full stop, is going to eventually end in grief.If you only have those landing distance figures available then you shouldn’t be using 15%. TALPA arc guidance for aircraft where no inflight landing performance is available suggests using factors of 1.67 to 3.4/5.1 depending on runway contamination and reverse thrust availability.
If a manufacturer has provided inflight landing distance figures, these are not just based on 50ft/max effort so 15% is considered an acceptable buffer.

[Capn Bloggs]

And for dispatch that’s fine, but I’m sure as **** not going to use 167% while I’m in the air like you said you would.
And of course, unless you shorten your flight time, you'll always have close to a 67 % buffer when you land anyway...

Are you saying every aircraft’s landing performance is predicated on max braking effort? Because you’re very wrong.
What is it based on then?

If a manufacturer has provided inflight landing distance figures, these are not just based on 50ft/max effort so 15% is considered an acceptable buffer.
Please explain "not just based on". What are they based on then?

[compressor stall]

50% of headwind for starters.

[Capn Bloggs]

50% of headwind for starters.
If they're based on 50% HW, then when you get there and there's no HW, you're worse off. :confused:

[Capn Bloggs]

A request:

Run Flysmart in the pre-dispatch scenario to say Hamilton Island and advise the landing weight allowed.

Then run Flysmart in the in-flight scenario and advise the weight allowed.

[StudentInDebt]

What is it based on then?


Please explain "not just based on". What are they based on then?You’d have to look that up for your aircraft type, if the information is provided, as it varies depending on the assumptions the manufacturer makes.

[Capn Bloggs]

You’d have to look that up for your aircraft type, if the information is provided, as it varies depending on the assumptions the manufacturer makes.
What is it for your type? You don't have to state what type you're on.

Landing is pretty standard: threshold at 50ft at VRef, 7 seconds to touch down then max braking with full reverse to a stop. What other things will make "15% an acceptable buffer" [your words]?

[StudentInDebt]

What is it for your type? You don't have to state what type you're on.

Landing is pretty standard: threshold at 50ft at VRef, 7 seconds to touch down then max braking with full reverse to a stop. What other things will make "15% an acceptable buffer" [your words]?50ft, 7 seconds, landing conditions as entered, braking according to chosen method (autobrake/manual-max braking/reverse), reported braking action taken into account. 15% on top of that figure. As the PIC you are free to use whatever figure you like as a buffer if you feel it is appropriate, just as you can opt to use a higher landing minima than say 200ft/550M.

[Capn Bloggs]

Given the thread is about an aeroplane that ran off the end in the wet, your choosing of the desired braking "method" to increase the buffer is irrelevant. Obviously, we're talking about a max-braking landing with only 15% buffer.

[StudentInDebt]

Given the thread is about an aeroplane that ran off the end in the wet, your choosing of the desired braking "method" to increase the buffer is irrelevant. Obviously, we're talking about a max-braking landing with only 15% buffer.We are not obviously talking about a max effort stop with a 15% margin because the crew concerned didn’t carry out any landing distance calculations. This whole line of conversation has come about because you stated that you don’t feel that 15% is an adequate margin on assessed landing performance and prefer to rely on 67/92%.
IFLD figures are there to provide guidance on the actual level of performance available given the conditions and take account of runway condition. So the braking method chosen is not irrelevant, one could calculate the distance required with autobrake 2/low and find that even on a contaminated runway there is sufficient LDA with the 15% margin applied.

[Capn Bloggs]

I am attempting to understand what you people understand about the 15% and why it seems OK on a routine basis, that is all.

[BuzzBox]

I am attempting to understand what you people understand about the 15% and why it seems OK on a routine basis, that is all.

The dispatch case is based on the certified landing data, which is predicated on maximum manual braking. It's a planning requirement that is very conservative and is not normally representative of actual landing performance. You previously said: "unless you shorten your flight time, you'll always have close to a 67% buffer when you land anyway...". You won't, unless you're in the habit of using maximum manual braking on every landing. Pilots normally use less braking force (either auto brake or manual), which invalidates the dispatch calculation. The pilot does not know how much margin is available on the runway length.

For the in-flight case, the regulations allow the use of a 15% buffer if actual landing distance data is available. Both Airbus and Boeing provide advisory data that includes information for a variety of brake settings. The pilot can input the actual brake setting, environmental conditions and aircraft configuration, and calculate an accurate landing distance, to which the 15% buffer is applied. The pilot then knows exactly how much margin is available, assuming the landing occurs within the normal touchdown zone.

The following might be of interest:
https://ifalpa.org/media/2030/12adobl03-certified-vs-advisory-data-on-boeing-aircraft.pdf

[morno]

What is it for your type? You don't have to state what type you're on.

Landing is pretty standard: threshold at 50ft at VRef, 7 seconds to touch down then max braking with full reverse to a stop. What other things will make "15% an acceptable buffer" [your words]?

That's not the assumption that is being made with Airbus, Flysmart or not. The bog standard charts in the QRH have braking choices as being Low, Medium, Max Manual, and then you add or subtract for reversers (been a while, I think it’s subtract, so it assumes you don’t have them until you do).

Flysmart in the dispatch mode, does not take into account reverse or brake mode.

Flysmart in the inflight mode, let’s you choose these.

So when I have data that has a very specific set of circumstances in it to spit out a calculation, based upon the exact situation on the ground and using the exact braking options, why can’t I use 15%? 67% would be a huge overkill.

If I as a captain refused to land on a runway that was plenty long enough for the conditions at the time allowing for a 15% buffer, all because I said I wanted a 67% buffer, then they’d probably take me offline and ask me into the sim so I can prove that I can actually land the aircraft safely.

[Lead Balloon]

So if you're obliged to apply 1.67 - or in the worst case scenario, 1.92 - as the destination landing distance factor when calculating the take off weight calculation at 'dispatch', how does it make any difference when you get into the air and you find out that, for example, the destination conditions are as forecast? Do you magically increase weight mid flight?

[404 Titan]

Capn Bloggs & Lead Balloon

CAO 20-7-1B is very clear. Prior to dispatch, for a dry Runway 1.67 x LDR Dry or for a wet Runway 1.92 x LDR dry/Flight Manual or Ops Manual data for a wet runway shall be used. Once inflight 1.67 x LDR Dry or if actual landing distance data is supplied under its type certificate, 1.15 x Actual LD. Regarding Airbus and Boeing, actual LD is supplied under their Type Certificate. I can’t speak for Boeing but Airbus SOP is to use FlySmart calculations for Medium-Poor braking (contaminated) if the destination is forecasting weather conditions that would result in contaminated runway condition, otherwise 1.67 or 1.92. Also once in flight and the weather report indicates a wet runway, calculation should be based on Medium-Poor braking (Contaminated) if using reverse idle. It might surprise you but FlySmart landing calculations with 15% factoring and Medium-Poor braking is worse than 1.67 and 1.92 factoring on a dry runway.



The figures below are based on sea level, ISA conditions, zero wind at Max LW. 1.67 & 1.92 are based on max manual braking on a dry runway and the FlySmart figures are based on sea level, ISA conditions, zero wind at Max LW and Medium-Poor braking x 1.15.



A320-200: 1.67 = 6148, 1.92 = 7068, FlySmart = 7870

A321-200: 1.67 = 6318, 1.92 = 7293, FlySmart = 8024

A330-300: 1.67 = 7165, 1.92 = 8237, FlySmart = 8911

A350-900: 1.67 = 7831, 1.92 = 9003, FlySmart = 9427

A350-1000: 1.67 = 8023, 1.92 = 9224, FlySmart = 10727

[Lead Balloon]

Thanks 404T.

So you're sitting in your A3XY-Z at Brisbane, planning a flight to Hamilton Island (about 5,800' available) where the forecast and every other piece of information says it's raining heavily with a variable 5kt wind. You work out your takeoff weight based on the landing distance required in this circumstances.

What changes after you take off? Serious question, because I'm not 'getting it'.

I agree with you: The rule is pretty clear for the maximum 'dispatch' weight calculation. What I don't understand is how you 'change' anything after you take off. If it turns out the actual weather at your destination is 'better' than forecast, you can't add weight (unless, I suppose, you can somehow burn less fuel getting there than planned). If the weather is 'worse' than forecast, what then?

[Lookleft]

LB its like looking at a weather forecast. Pre-flight if the forecast indicates that you have to carry fuel to hold for 60 minutes or carry an alternate then the regs say carry it. Once you get airborne the weather changes so now you dont have to carry the fuel but it is on board anyway. Another example is ETOPS. Before take-off there are a whole bunch of rules that govern how much fuel you take and what level of equipment must be serviceable. When you are airborne basically you do what you have to do to complete the flight safely. So with the pre-flight LDR calcs you will work out if you can take the payload based on the forecast weather. Those calcs have different assumptions built into them. Once you get airborne (there is that phrase again) you work out if you can actually land at your destination based on the actual conditions and actual landing weight with different assumptions built into the calcs. So if you worked out pre-flight that you were limited then you might have reduced your fuel (tankering possibly) or payload. Inflight you are no longer interested in what might have been you are only interested in what is actually possible with your actual weight.

Hope this clears up your confusion.

[404 Titan]

Lead Balloon

If the “Heavy Rain” means that the runway is contaminated, ie >3mm of standing water on >25% of the runway, FlySmart would be used prior to dispatch with forecast conditions and Medium-Poor braking, medium auto brake idle reverse x 1.15.

If “Heavy Rain” means the runway is wet, 1.92 x LDR dry would be used.

In both cases a landing performance would be calculated inflight using FlySmart with actual conditions, the actual landing weight, medium-poor braking if using idle reverse, medium auto brake x 1.15. If too short, recalculate with full reverse. If still too short recalculate with manual braking. Finally if still to short divert to your alternate. Where I fly we always carry an alternate but in the Australian context, an alternate probably should have been planned for based on the info you’ve provided.

I had a flight a few years ago into Perth with an A350-900. Forecast for Perth was a Tempo TS and rain with wind straight down RWY21 at 30kts. We don’t use 06/24 unless operationally required due to the shorter LDA. Also we normally plan Perth as an Island Reserve (2 hours holding Fuel) due to limited available alternates but on this night Dispatch planned Adelaide as an alternate due to WX. During the flight WX forecasts for Perth started to deteriorate with heavy rain, TS and winds straight across RWY 03/21 at up to 50kts. ATC had closed this RWY but in addition it was above the max Xwind for the A350. Rwy 24 was the only choice but with Medium-Poor braking and idle reverse, the Rwy was too short. I recalculated with full reverse and the numbers worked, just. I recalculated again with manual braking which gave me more fat. Based on the numbers we were going to have to exit Rwy 24 at the end via V but in the end was able to exit via A.

The point I’m making is that if on the day, the numbers don’t work make sure you have a plan B, preferably an alternate.

[Lead Balloon]

Thanks Lookleft.

I'm not confused about the difference between planning a flight and doing a flight. I have some exposure to and experience of the difference between forecast weather conditions and 'on paper' representations as to the conditions of a destination aerodrome, on the one hand, and dealing with reality on the other.

I'm confused about what and how you change things after you've taken off, having taken off at a weight calculated by reference to the conditions forecast before take off.

If you in fact "worked out pre-flight that you were limited [and you] reduced your fuel (tankering possibly) or payload", how do you increase fuel on board or passengers on board or cargo on board after take off, when you find out that the weather conditions at your destination are, in fact, 'better' than the ones you planned on? I can envisage you going a more direct route and landing with more fuel than planned, and therefore at a higher landing weight than planned. Any other way of landing heavier than planned, in accordance with the rules?

And what do you do after take off when you find out that the weather conditions at your destination are, in fact, 'worse' than the ones you'd planned on? I can envisage you flying around for 'a while' to burn fuel to reduce landing weight. Any other options?

(PS: Thanks, too, to 404T. Digesting your post now.)

[neville_nobody]

I'm confused about what and how you change things after you've taken off, having taken off at a weight calculated by reference to the calculations before take off.

You calculate your landing distance in the actual conditions and multiply by 1.15. You then divert or hold if you can't make it. I believe all this came out of the Southwest accident in Midway which was a very short runway with a change of runway condition from dispatch.

[404 Titan]

neville_nobody

And Air France into Toronto in the A340, though there was more to that accident than just LDR. The LDR was if memory serves me right, OK for the conditions. It was the persisting with an unstable approach and landing have way down 24L (9000 ft LDA) and delaying full reverse that caused them to go off the end. No amount of LDR calculations would have prevented that accident but it is the reason we are do thing the way we are now on the Airbus.

[Lead Balloon]

Then I think we've circled back to Capn Bloggs's point.

[morno]

Sounds like your company needs to configure Flysmart to be more user friendly 404-titan.

In my last company you didn’t have to do all that nonsense for wet runways etc., you just selected either dry or the amount of water on the runway (ability to choose either a wet or a contaminated runway basically).

[morno]

Thanks Lookleft.

I'm not confused about the difference between planning a flight and doing a flight. I have some exposure to and experience of the difference between forecast weather conditions and 'on paper' representations as to the conditions of a destination aerodrome, on the one hand, and dealing with reality on the other.

I'm confused about what and how you change things after you've taken off, having taken off at a weight calculated by reference to the conditions forecast before take off.

If you in fact "worked out pre-flight that you were limited [and you] reduced your fuel (tankering possibly) or payload", how do you increase fuel on board or passengers on board or cargo on board after take off, when you find out that the weather conditions at your destination are, in fact, 'better' than the ones you planned on? I can envisage you going a more direct route and landing with more fuel than planned, and therefore at a higher landing weight than planned. Any other way of landing heavier than planned, in accordance with the rules?

And what do you do after take off when you find out that the weather conditions at your destination are, in fact, 'worse' than the ones you'd planned on? I can envisage you flying around for 'a while' to burn fuel to reduce landing weight. Any other options?

(PS: Thanks, too, to 404T. Digesting your post now.)

The way I understand it is that the 1.67 and 1.92 is merely a simple worst case factor that should cover you, based upon the planned weather forecast and landing weight.

Once you are airborne though, you obviously need to check based upon the exact conditions etc.

Unlike 404, I’ve never had Flysmart throw me up a greater LDR than the preflight 1.67/1.92, it’s generally just a bit less. But it’s not often that I’ve been that limited to the point of not being able to land at MLW either, normally been well in excess. Perhaps it’s in how they’ve got him figuring it out, because Flysmart is very customisable for the customer, case in point with the ability to select the level of contamination on the runway.

At the end of the day, this is very Australian, arguing over the semantics of this bull**** in this day and age of EFB’s. The rest of the world probably couldn’t give 2 ****s about how it’s worked out etc., they just punch it into the EFB, let it work it’s magic, and carry on with the rest of the day. When we do it day in and day out, I’d rather just show up at work and if it’s within the regs, who cares.

[Lead Balloon]

Good point!

[404 Titan]

Morno

It's stock standard Airbus. Been like this for a number of years though it's changed a little with FlySmart on the iPad EFB and the built in EFB on the A350 OIS. Prior to iPads etc, we'd use ACARS that had numbers from 6 for Dry to 1 for Ice (Poor). The new system is extremely easy and if you're not sure of the braking action there is a very easy table in the QRH. Everything is now standard Airbus. Lawyers have put an end to airlines doing there own thing and for this particular thing I agree. Before it was a dogs breakfast to the point a in-flight landing performance wasn't even required most of the time.

[Bankstown]

Another interesting regulatory anomaly would be if the same F100 was operating to Newman that day in the charter category, which occurs, it would only need to apply the 1.67 pre-dispatch factoring regardless of the wet runway.
I understand the new regs will fix that?

[morno]

Morno

It's stock standard Airbus. Been like this for a number of years though it's changed a little with FlySmart on the iPad EFB and the built in EFB on the A350 OIS. Prior to iPads etc, we'd use ACARS that had numbers from 6 for Dry to 1 for Ice (Poor). The new system is extremely easy and if you're not sure of the braking action there is a very easy table in the QRH. Everything is now standard Airbus. Lawyers have put an end to airlines doing there own thing and for this particular thing I agree. Before it was a dogs breakfast to the point a in-flight landing performance wasn't even required most of the time.

Ah yes, I know the chart you’re talking about.

I can’t say I was involved in setting up Flysmart in my company, so I’m not 100% sure how they did it. But I do know that it was different between 2 companies I’ve worked for, and apparently it’s just a matter of selecting certain things in the background before the end users (us) see it.

[BuzzBox]

Then I think we've circled back to Capn Bloggs's point.

Perhaps try thinking about it like this:

The purpose of the dispatch calculation is to help determine the maximum weight for take-off, which must be the lesser of:
a. the take-off performance limited weight, and
b. the landing performance limited weight plus the weight of fuel/oil consumed in-flight.

The landing distance limited weight derived during that process is based on a bunch of regulatory factors and forecast conditions that are not particularly relevant for the actual landing. What's relevant are the actual conditions, weight, braking method, configuration, etc. The pilot uses that information to calculate the actual landing distance and factors it by 15% to determine the required landing distance. He or she can then compare the required distance with the distance available, to determine how much margin is available for the landing.

The following is an Airbus discussion of in-flight landing distance assessment:
https://safetyfirst.airbus.com/app/themes/mh_newsdesk/documents/archives/operational-landing-distances.pdf

[404 Titan]

Morno

Unlike 404, I’ve never had Flysmart throw me up a greater LDR than the preflight 1.67/1.92

It's not so much that FlySmart throughs it up. It's more that we ask it as it's and SOP requirement if we want to use idle reverse on a wet runway. Asking it to calculate a landing performane for Medium-Poor braking is the same as calculating a landing performance for a contaminated runway with more than 3mm of water or slush up to 13mm. In this calculation with the 1.15, it's more than the 1.67 and 1.92 dispatch calculation. Calculations for Dry and Good will be less than the pre Dispatch calculations.

[The Banjo]

If it is pxssing rain with a strong crosswind on a tapered runway (banking the water on one side of the runway) with no grooving then the runway may well be contaminated with poor braking. ALL of the pre-mentioned factors go out the window and you either hold or divert. A reputable ops manual might state that landing on a contaminated runway shall not be attempted unless a greater emergency exists...

[morno]

Morno



It's not so much that FlySmart throughs it up. It's more that we ask it as it's and SOP requirement if we want to use idle reverse on a wet runway. Asking it to calculate a landing performane for Medium-Poor braking is the same as calculating a landing performance for a contaminated runway with more than 3mm of water or slush up to 13mm. In this calculation with the 1.15, it's more than the 1.67 and 1.92 dispatch calculation. Calculations for Dry and Good will be less than the pre Dispatch calculations.

Gotcha, makes sense now.

[Lookleft]

This is from the link that Buzz Box provided:

Summary
The goal of this Briefing Leaflet is enhance your understanding of the landing performance data and to appreciate the role that speed
brakes and thrust reversers play in deceleration especially when landing.
As a review:
Certified data is factored, used for dispatch purposes and does not use reverse thrust.
Advisory data is non-factored (FAA), used enroute and has always been based on the use of reverse thrust.
Speed brakes increase drag and decrease lift allowing your brakes to be considerably more effective.
Reverse thrust provides significant deceleration when landing on a critical runway; short, slippery with the braking action
reported POOR.

The bolding is mine. Can I suggest you download the document, have a good read then let us know if you still are confused.