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AH64 APACHE
29th Dec 2005, 22:19
Heard there was an a/c off the runway in CPH tonight (29/12) in poor vis and heavy drifting snow. Lots of cancelled flights and unreliable braking action on r/w.

Is this correct?

M609
29th Dec 2005, 22:46
The Snowtam indicates less then perfect conditions......


SWEK0166 EKCH 12292152
(SNOWTAM 0166
A) EKCH
B) 12291939
C) 04L
F) 975/975/975
G) 6/6/6
H) 28-9/25-9/30-9 SFH
N) 975
B) 12292148
C) 04R
F) 975/975/975
G) 5/5/5
H) 25-9/26-9/22-9 SFH
N) 975
B) 12291902
C) 12
F) 975/975/975
G) 8/8/8
H) 24-9/23-9/25-9 SFH
N) 975
R) 975
T) ALL RWYS COVERED 100 PERCENT.
ALL TWYS AND APRON B/A POOR.
CHEMICALS HAS BEEN SPREAD OUT.
SNOW AND ICE ON SHOULDERS RWY 04L, 04R AND 12.


Frozen ruts or ridges, ice and wet snow on all the runways is not good. The fact that they put "unreliable" behind all the frition numbers says a lot too........ :ugh:

TheOddOne
30th Dec 2005, 00:59
The fact that they put "unreliable" behind all the frition numbers says a lot too........

In the UK, that's ALL that we're legally able to say, now. We mustn't even quote the numbers at all. This is partly because there is still no International agreement on
a) what all the different readings mean that different machines come up with on the same surface, or even the different readings you get on the same surface with the SAME machine on consecutive runs
b) the lack of correlation between a friction reading taken at 40MPH using a machine you can lift with one hand and the braking action of an a/c doing 100kt+ and massing 50tonnes or more.

This lack of progress has been going on for years and the UK CAA have finally said 'OK. you lot, until it's sorted out, no promulgation of friction readings to ATC or pilots'.

We're working for this winter on a 'back to black' principle and won't re-open following closure for snow removal until we're 'WET, WET' WET' or better.

It probably makes the publishing of a SNOWTAM irrelevant.

Cheers,
The Odd One

6000PIC
30th Dec 2005, 01:54
This sounds to me like a bunch of idiot bureaucrats ( ICAO , CAA , you pick the agency ..) who , for lack of coming to an agreement , are putting the travelling public , and flight crews at risk.
Where are the journalists ?
What are the conflicting opinions ?
Get off your asses and come to a decision.
How simple is it to come up with a worldwide standard for runway braking coefficient ?
.... an easy to understand system and not the BS snowtam report or runway braking reports that we recieve now.
This I believe is a crack in the system that could result in a disaster.
What a load of bollocks.

Techman
30th Dec 2005, 06:10
Funny how those who actually have to deal with these conditions regularly have a more pragmatic approach.

green granite
30th Dec 2005, 08:21
b) the lack of correlation between a friction reading taken at 40MPH using a machine you can lift with one hand and the braking action of an a/c doing 100kt+ and massing 50tonnes or more.

I find that odd, back in the late 60's or early 70's (can't remember exactly) I did a long series of trials @ Waddington & Scampton doing just that with all RAF aircraft. The aircraft ran through a 2000ft long test section on the runway, full braking used on a dry runway we would then flood the runway & repeat. I wasn't involved with the analasys work so I don't know what the outcome was :confused:

Spenda
30th Dec 2005, 10:19
Anyone know which runway the aircraft was off last night? We were waiting in the queue last night and aircraft were being offered a departure runway of 12 with the surface wind 130@22 or departure on 22R with the wind 250@06. With all the blowing snow around our stand the wind looked a lot more like 130@22 than it diid 250@06. A number of voices on the radio commented on how different the two winds were at the same airport.

M609
30th Dec 2005, 13:16
Well, there are some nations which have to take winter condition reporting serious.

We:

1. Allways report the numbers, and what they are measured with (SFH, SKH etc)
2. It's regulated in the norwegian BSL (equal to your CNO I think) on what, and on how much contamination the different friction devices can be used on. (Don't have the table at hand, but as an example, I think it's prohibited to use the GRT or TAP on wet snow.)
3. It's regulated in what increments each type of contamination is measured, the increment for dry snow is 8mm, slush 3mm etc)

On all the 'proper' airfields we use the SFH or SKH, and if the measurement is fresh, and not 4 hours old, condtions are monstly better then measured in pretty much all conditions. I belive that all incidents with runway excursions due to slippery surfaces in Norway the last 10 years have been due to

1. Late reporting, last snowtam not reflecting the actual condtions. (The watch commander of the field maint. unit not doing his job)
2. Airline SOP not up to scratch, crew landing/departing in conditions well outside aircraft capabilities.
3. Aircrew unfamiliar with operating on contamination, this is allso VERY true when it comes to TWYs and aprons.
(The concept of not trying to make a 90 degree runway exit at the same speed as in the summer etc......)

leander
30th Dec 2005, 14:15
M609 ( and all other diligent ATCOs )

Days / weeks spent operating multiple sectors around Europe in winter are a nightmare without your accurate reports.

Thank you :ok:

Miserlou
30th Dec 2005, 19:56
I can find nothing about this on any of the Danish radio or news papers' websites.
Even the mother-in-law hasn't called to ask if I was at work so it can't be true! She knows everthing.

tribo
1st Jan 2006, 21:46
I find that odd, back in the late 60's or early 70's (can't remember exactly) I did a long series of trials @ Waddington & Scampton doing just that with all RAF aircraft. The aircraft ran through a 2000ft long test section on the runway, full braking used on a dry runway we would then flood the runway & repeat. I wasn't involved with the analasys work so I don't know what the outcome was :confused:

Green granite - Did you take part in some of these tests?

Early UK Research

ICAO Study Group on Snow, Slush, Ice and water on Aerodromes.
Memorandum No. 16
10 November 1970
Attachment B, Presented at Langley in November 1968 and published in the NASA report SP-5073.

Correlation between Runway Coefficient of Friction Values Produced by Different Types of Instruments and the Prediction of Aircraft Stopping Distances.

1. Introduction

The 5th Air Navigation Conference recommendation 5/32 states inter alia that ICAO invite interested States to co-operate in the further development of practical methods, suitable for international standardization, for calibrating coefficient of friction measurement devices and wet coefficient of friction of runway surfaces. In the UK research has been going on for a number of years to determine the possibility of predicting aircraft stopping distances using vehicular device and also to investigate the correlation between various devices. As the most hazardous conditions for a landing aircraft would occur when there was sufficient water or slush to cause aquaplaning or with surface ice, it was decided at the outset that a particular effort should be made to authenticate the prediction method in these situations. As trials with full scale aircraft under these extreme conditions with three different types of aircraft and three ground vehicles using different principles for measuring friction.

2. Trials between a Swift Aircraft and Road Research Laboratory Trailer

The first set of trials was conducted with a Swift fighter aircraft weighing approximately 18,000 lb and the Road Research Laboratory light friction trailer. The aircraft was instrumented to measure drag and vertical load as well as velocity from which the friction speed relationship curves were obtained at up to 140 knots for a number of runway surfaces, These curves were compared with those from the Road Research trailer at speeds up to 161 kph (100 mph= on the same surfaces. It was hoped that the ratio of friction coefficients at the same speeds might be a constant or at least that the change with speed might follow the same pattern from one type of surface to another. However, neither of these hopes was realised and it was concluded that there was no correlation between the actual friction values produced by an aircraft and the Road Research Laboratory Trailer.

3. Trials between a Hunter Aircraft and Heavy Load Friction Vehicle

The next series of trials in this study occurred some years later when the opportunity arose to compare the performance of a Hunter aircraft weighing about 17,000 lb and a Heavy Load Friction Vehicle which was fitted with a Hunter wheel, brake, tyre and braking system. The same tyre pressures, wheel loads, wetness conditions and surfaces were used. It was thought that under such closely comparable test conditions there should not only be correlation, but the actual figures themselves should be the same. This was however not the case and it led to the inevitable conclusion that correlation between friction values of aircraft and ground vehicles was most unlikely.

4. Trials between the Ministry of Technology Runway Friction Meter and a Convair 990 and F4 Aircraft

At the invitation of the NASA, the UK Ministry of technology conducted a joint Friction Correlation Programme at Wallops Station, Virginia, during 1968. Nasa had used a Convair 990 and F4 aircraft to determine the speed friction relationship of nine runway surfaces with widely differing friction coefficients. The programme was to compare these aircraft values with those from the Heavy Load Friction Vehicle, Road Research Trailer and a newly developed runway friction meter called the Mu-Meter. Once again the friction values did not correlate with the aircraft nor in fact with each other.

Wing Commander Fowler
1st Jan 2006, 21:51
Oh Joy - so all the data used to determine whether it's safe to land is cr*p then? :eek:

Empty Cruise
1st Jan 2006, 22:36
Yes - but remember, they have been so for several years! That means that we have safely operated with these figures for decades - but suddenly, we cannot have them any more :rolleyes: - so finally, the lawyers have managed to get around to airport ops as well...

Now, that leaves us as pilots in a tight spot. If the runway is contaminated, but no B/A of F/C figures are forthcoming - I cannot legally land the aircraft. Ergo - if snow or other contaminant is forecast @ a UK airport, I should therefore treat that airport as below planning minima, and carry fuel to the farthest of 2 destination alternates. So if all the UK is affected by e.g. snow - I'm better off filing SVG or BGO as alternate - since they will give me the info I legally need to land the aircraft!

This is utter BALOX (yep, I miss CPH!) to me - and believe me, the Norwegians, Swedes, Finns & Danes have a lot of experience keeping their airports operating, even in snowy conditions. And somehow, despite risking similar lawsuits as UK airports, they manage to know when to give the figures (i.e. the airport carries the can) and when to report them unreliable (i.e. the PIC carries the can).

Honestly - if you cannot give us the info we need - why bother? Perhaps the airlines should start filing compensation lawsuits when unnecessary diversions occur due to this practise. If an SFH comes up with unambigous figures - yet they are still reported by ATC as "unreliable" - my feeling is that the airline stands a good chance of winning such a lawsuit. Perhaps FlyingLawyer has an answer for this one? :)

Best regards fm
Empty

tribo
1st Jan 2006, 23:11
Oh Joy - so all the data used to determine whether it's safe to land is cr*p then? :eek:

Green granite, Wing Commander Fowler and others

The rest of the (1970) document reads:

5. Other Prediction Methods

As a result of the failure to correlate with the system described above, two other methods were investigated. It had been suggested that the ratio of the wet to dry stopping distance of a locked wheel vehicle and of an aircraft might be the same on the same surface when the former was using plain tyres. As the Mu-Meter was a trailer it could not measure its stopping distances, but it was possible to obtain a relationship curve between the value it read on a number of surfaces at 64 k.p.h. (40 m.p.h.) and the calculated stopping distance from 113 k.p.h. (70 m.p.h.) as defined by its speed friction curve. The wet over dry ratio was then only a matter of reading off the appropriate values from the curve.

Results from Wallops Station on the Convair 990 and F4 indicated this method had considerable promise and in fact a 1:1 relationship between Mu-Meter and aircraft was achieved on a number of the surfaces so it was decided to continue this verification by further trials in the United Kingdom with a Hunter and Beverly aircraft. It soon became apparent however that these two aircraft gave different values for the wet to dry stopping distance ratio on the same surface, in fact it varied from 1 to 1.7 and therefore a system using wet to dry ratios for the prediction of stopping distance could be in error by as much as 70%, and as this was considered unacceptable the method was discarded.

Having discarded the wet to dry ratio method it was decided to determine the aircraft stopping distances on a number of surfaces with as wide a friction range as possible and to plot these against the values given by the Mu-Meter at 64k.p.h (40 m.p.h.) obtained as close to the time of the aircraft friction run as possible. In fact a technique was developed ehere the friction meter made a run immediately before and after the aircraft and the value used was a mean of the two. This method was successful and can produce individual curves for each aircraft provided sufficient points are obtained. The possibility of predicting aquaplaning for individual aircraft types and undercarriage configurations is under investigation. By making use of snow and ice covered runways it was possible to determine the Hunter correlation curve down to very low values under natural conditions. (attached figure).

6. Discussion

With the advantage of hinsight it is perhaps not surprising that the friction values of aircraft and vehicular devices do not agree. An aircraft tyre operates at far higher pressures and loads than vehicles; the aircraft uses an automatic braking system which in itself has varying degrees of efficiency depending on its design and there are differences in wheel layout, but it is perhaps surprising that the values do not agree even when a vehicle and aircraft tyre wheel brake have identical physical parameters, except for suspension.

Bearing in mind there are a number of different ways in which friction can be measured e.g. slipping wheel, locked wheel, yawed wheel with different vertical loads, tyre pressures and test speeds it is again not surprising that each equipment can give different values under the same test conditions. These are then physical facts which must be accepted, the problem is what to do about it and therefore appears to be only one sensible solution, and that is that everybody should use the same equipment.

It is suggested that a runway friction meter should be portable, rugged, accurate, able to operate at low temperatures, relatively cheap and incapable of being influenced by the operator. It is also suggested that it should be capable of providing a pictorial representation of the friction along the complete length of the runway not only for reasons given in the note to paragraph 2.8.6 in part II of Annex 14, but also to increase its usefulness by showing the extent and variation in friction caused by rubber deposits, runway damage due to jet blast etc, In addition the same equipment could be used to classify runways in their friction order if necessary by an outside agency and if airfield operators have their own equipment, they could make their own periodic check.

7. Conclusions

Correlation between aircraft and vehicular friction values at the same speed is improbable and if it does occur then it is fortuitous.

It is unlikely there is any correlation between friction coefficient values produced by equipments using different and sometime the same principles.

The only way of establishing a standard system for providing information on the presence of contaminants on runway surfaces and their effect on braking action is for all airport operators to use the same design of equipment.

References:R.W. Sugg. Tests to Determine the Usefulness of Vehicular Instrumentation to Predict Aircraft Stopping Distances S and T Memo 9/64. Ministry of Technology.

Road Research Laboratory. Tests with Heavy Load Skidding Machine to Determine Braking Force Coefficients between an aircrafdt tyre and various wet surfaces. S and T memo 8/63 and 10/64. Ministry of Technology.

TheOddOne
1st Jan 2006, 23:41
Ergo - if snow or other contaminant is forecast @ a UK airport, I should therefore treat that airport as below planning minima, and carry fuel to the farthest of 2 destination alternates. So if all the UK is affected by e.g. snow - I'm better off filing SVG or BGO as alternate - since they will give me the info I legally need to land the aircraft!

Best regards fm
Empty

...if I give you the runway as WET, WET, WET, then you can rest assured that the friction that we've measured at least meets that minimum standard, even though I cannot legally give you the actual data (it might well be up to a mu of .7 or so by then). Sounds like a good idea to file for an alternate with no forecast contamination. I suppose that in the departure case you can at least wait until conditions are right.

The early ICAO work has recently been comprehensively repeated using A320 and other aircraft and all the popular makes of trailer and in-vehicle friction measuring devices. Disappointingly and depressingly, there STILL ain't no correlation between braking action and friction measurement and the range of devices are STILL out of whack with each other. How can you possibly stipulate which device to adopt as a standard when they are all different from each other and NONE of them relate to any aircraft?

Cheers,
TheOddOne

green granite
2nd Jan 2006, 09:46
Tribo et al

No they pre-dated the trials that I was involed in.
I believe that the Hunter trials were done @ Cranfield where they had ponds formed on the runway using rubber strips and could flood these (they left a strip free for the nose wheel so that the pilot could steer the a/c) upto aquaplaning depth. Told that the sight of a hunter aquaplaning is very spectacular.

The trials I refered to, I think, sort of came out of those early trials, Cranfield was the trials authority, the company I worked for supplied the engineering & kinetheodolite staff (me), they took about 4 months to do, mainly because of needing dry calm conditions. Maxeret serviceability was interesting as we had lots of burst tyres on the larger a/c & the brakes seize solid on a Victor @ Scampton half way down the runway (we wer'nt very popular as it shut the airfield while they jacked the aircraft up and removed the brakes so they could tow it away)

Short Approach?
2nd Jan 2006, 09:46
Hello there.

Firstly I can guarantee you, there was no A/C off the tarmac at any point on the 29th or 30th for that matter.

Secondly, our friction tester guys have been instructed to add "unreliable" to the numbers as soon as "wet snow" is on the surface.

Odd thing was, even though the numbers at one point was 15 14 13 or something like that. The landing pilots all reported medium to good breaking action. (Of course the Finnish guys reported it to be very good :-) ) And most of the A/C's in the holdings took thoose reports over the numbers, and landed.

Is that also the procedure where you guys collect your $?

alf5071h
2nd Jan 2006, 10:41
Oh Joy - so all the data used to determine whether it's safe to land is cr*p then? :eek:
The most surprising aspect might be that so many pilots do not know this, or do not understand the risks that are currently accepted.

More recent research is here with links to the report TP 14273 Falcon 20 aircraft braking performance on wet concrete runway surfaces. (www.tc.gc.ca/tdc/projects/air/e/8262.htm)
“On a smooth, wet concrete runway surface close to the minimum maintenance standard, … the current operational dispatch factor of 1.92 for turbojet aircraft landing on wet runways at destination or alternate airports would have to be increased to a value of 2.2 to 2.4 in order to achieve the same level of safety as that which is currently accepted for dry runway operations”.

I interpret the reported data as indicating that where with current calculations an aircraft should stop, using max braking, with 40% of the runway remaining. In reality on some runways, this safety the margin is significantly less. Then add to this the actual braking level used in wet conditions, the variability of runway surfaces and maintenance condition, rubber deposits, cross wind, water damming, long and/or fast landings, etc. Then we start to consider contamination … !

“For landings on wet runways, the excess distance between the landing field length, calculated using the current method, and the actual landing distance was considerably less than the excess distance on dry runways.

TheOddOne See the values of friction test measurements for wet runways in the report (table 2); note for a ‘tanker’ (a more realistic) wet runway, all values of mu are well below 0.7, then compare these with the actual, even lower values as experienced by aircraft (figures 10 & subsequent).

Short Approach? If data is “unreliable” then why broadcast it. The figures may only serve to bias the crew’s judgment.

Humans are the weakest link in winter operations, the pilots the last link. If due to lack of information or poor understanding, our judgment can be so flawed then there should only be one option in the decision making process; don’t consider landing.
We might seek to blame others or equipment for the hazards of winter operations, but do we (pilots) really consider the risks involved with landings on contaminated runways.
There are few if any hard limits, like a low vis approach ban. Perhaps the runways should be closed until cleared, or why not consider undersurface heating like sports grounds. I am sure that those operators who have suffered cost and disruption due to accidents would be prepared to pay a small premium to support these initiatives.

Also see thread Good - Fair - Poor – Nil ( http://pprune.org/forums/showthread.php?t=201987)

”Attempts to land on heavily contaminated runways involve considerable risk and should be avoided whenever possible. If the destination aerodrome is subject to such conditions, departure should be delayed until conditions improve or an alternate used.
Operations from contaminated runways, by all classes of aeroplane, should be avoided whenever possible” (UKCAA AIC 61-99)

Flight Safety Foundation. Managing threats and errors during approach and landing. (www.flightsafety.org/ppt/managing_threat.ppt)

Short Approach?
2nd Jan 2006, 11:41
Short Approach? If data is “unreliable” then why broadcast it. The figures may only serve to bias the crew’s judgment.

You´re exactly right. We are currently haveing the same debate.

Is there any alterrnative? Is there a friction tester that can operate reliably in wet snow?

TheOddOne
2nd Jan 2006, 12:18
Is there a friction tester that can operate reliably in wet snow?



None that we have seen. If you know of a manufacturer claiming this facility, please let us know soonest!

The Odd One

green granite
2nd Jan 2006, 14:07
Cranfield appears still to be involved
http://www.cranfieldaerospace.com/expertise/aircraft.htm

alf5071h
2nd Jan 2006, 15:18
Short Approach? I cannot see any practical alternative other than temporarily closing the runway as above. With more accurate measurements and improved landing performance calculations we might only show / proove that the runway is not long enough; thus closing it until the contamination is cleared is both practical and safe.

Meanwhile perhaps all AFM data should be marked:
”Operation on runways contaminated with water, slush, snow, ice or other contaminants implies uncertainties with regard to runway friction and contaminant drag and therefore to the achievable performance … since the actual conditions may not completely match the assumptions on which the performance information is based. Where possible, every effort should be made to ensure that the runway surface is cleared of any significant contamination.
… it is not possible to produce performance data that will precisely correlate with each specific operation on a contaminated surface".

Also all runway condition / friction reports should be prefixed with the following warning:
… there is not, at present, a common friction index for all ground friction measuring devices. Therefore it is not practicable at the present time to determine aeroplane performance on the basis of an internationally accepted friction index measured by ground friction devices.
The text above is taken from EASA / JAA NPA 14 2004 (www.easa.eu.int/doc/Rulemaking/NPA/NPA_14_2004.pdf) (thanks Tribo). The NPA also comments, “Notwithstanding this lack of a common index, the applicant may optionally choose to present takeoff and landing performance data as a function of a wheel braking coefficient constant with ground speed. The responsibility for relating this data to a friction index measured by a ground friction device will fall on the operator and the Operating Authority.”

Operators again have to take responsibility for safety, yet where are all of the assumptions and guidelines to be published, and what practical help will be provided for the pilots preparing for the approach and landing.

OVERTALK
2nd Jan 2006, 16:03
http://www.pprune.org/forums/showthread.php?t=201568&page=13

Belgique's post on this SWA thread (above) addresses the very significant effect that progressive backstick can have upon increasing the wheel-braking coefficient and minimising anti-skid wheel release (for spin-up on contaminated runways).

From what I've read on this thread, no-one seems to have trialled this or factored it into the stopping trial. That seems to be quite an oversight IMHO.

Despite what the nay-sayers have said on that SWA thread (with some really crazy logic such as holding the stick forward to stop the nose rising and to achieve most effective braking), it has always been an effective braking augmentation technique. Used properly it would have probably stopped 50% of airplanes going off the end.

Once in reverse and with auto-braking applied, how could the nose possibly rise? Think of the distribution of weight BEFORE reverse or braking commences. Think spoiler effect. Then think of the strong nose-down pitching effect of both reverse and braking.

Then attempt to argue logically against backstick being an effective measure to increase the weight upon wheels. That would be an interesting argument to see and dissect.

Empty Cruise
2nd Jan 2006, 17:34
TheOddOne,

Sorry, my bad! Obviously, I trust you guys to give us the correct runway state - and will of course happily accept a WETx3 runway. In that case no need to get the FC, since WET is a well-defined case performance-wise.

But I still find it hard to accept that ATC will not give me an FC for a contaminated runway. It just cannot be right that a crew must accept to act as guniea-pigs for everybody else in the stack (as ShortApproach? described it). My point is - yes, there is no way to scientifically link a measured FC with that experienced by an aircraft. But at the same time - when you pass us an FC, it leaves us FC in an unambigous position legally speaking. The manufacturer has supplied data that determines the aircrafts' stop cabability as a function of FC. If we recieve an unambigous FC from you guys, based on an unambigous reading by e.g. an SFT - then there is no doubt, an overrun (or other incident) can only be tributed to 1) Flight crew not following established procedures 2) Wrong interpretation of data (e.g. misreading tables) 3) Wrong transmission of data from ATC to A/C 4) Manufacturers performance data are incorrect 5) Systematic errors in the measuring equipment 6) Operator has applied the data in the wrong manner.

I therefore feel that the responsibility for determining the relationship between the FC (as measured by a given piece of test equipment) and the stop cabability of the A/C lies with the manufacturer (and the operator who applies the data) - end of story. They make the thing, they test it, they supply the data, we operate it.

There will of course still be cases, e.g. wet snow or wildly varying results from multiple runs - where the FC must be reported as "unreliable", and in those cases we must make up our minds if we want to divert or act as/wait for a guniea-pig. But withholding information from flightcrew - for what appears as legal concerns - I find less than impressive. If all scandi airports adopted that blanket policy, that corner of Europe would shut down for 4-6 months a year!

I wonder if an FODCOM has been issued to describe this new UK ATC policy? This forum was the first I heard of it (yep, I know, that's kind of sad - need to get out more :O ) - it seems very harsh that just because an airport gives e.g. 1019 3000 -SN BKN007 - that airport could theoretically not be able to keep the runway to WET x 3 status, deposits might still exist - and therefore, I must consider it below planning minima! :mad: only because ATC is not allowed to pass the FC... :rolleyes:

Then again - prolly a 'very British thing' to do :D
Empty

TheOddOne
2nd Jan 2006, 17:50
Empty,

I spent many years both as an operative at Heathrow and a manager at LGW giving out readings down to 0.25 when we used a MuMeter and these were used by crews. In one case, back in the early eighties, a BA Tristar landed in the early hours at LHR in such conditions, turning off the runway was asked for braking action assessment by ATC, said
'Don't know, you said it was slippery, so we didn't use the brakes, just reverse!'
That's the luxury of a 4,000M runway, of course.
We were all familiar with the icy tables and what crews could and wouldn't accept.

What we really need is some serious back pressure from industry to say that we CAN operate safely in reduced braking action and limited contamination conditions, we need to work out what those conditions are, get on with it so that we can get on with our operation.

We're lucky at LGW where 'back to black' and 'Wet Wet Wet' are usually achievable. I hope this Winter doesn't prove me wrong!

Cheers,
The Odd One

Empty Cruise
2nd Jan 2006, 18:05
TheOddOne,

Yep - 4000 m. is always welcome under such conditions :ok: Up further north such luxury is hard to come by, so number-crunching suddenly becomes a good way to avoid appearing before the magistrates'...

You are right - we need ICAO & IATA in on this one, and get some guidelines laid down. But even if that process started today, it would be 5-7 years before the paperwork would be in place. In the meantime, we need to get by with all the info we go - in order to operate safely. So - would very much like to know where I can find info about the new policy (about not passing FCs) - because I really would like our FSO to get on the case & start asking NATS some questions. If you - or anybody else - could help in this regard, I'd appreciate it very much ;)

Brgds fm
Empty

tribo
2nd Jan 2006, 18:06
TheOddOne,

I wonder if an FODCOM has been issued to describe this new UK ATC policy?

FODCOM 2/98
FODCOM 17/2001
FODCOM 23/2003

ATSIN Number 37 Issued 11 November 2003

AIC 61/1999

UK AIP AD 1.2.2

Empty Cruise
2nd Jan 2006, 18:16
Thanks, tribo! Only started flying with a UK operator in 2005, so have missed those ones - will look them up :ok:

Empty

alf5071h
2nd Jan 2006, 19:11
OVERTALK Having been involved with a few military and civilian aircraft trials relating to aerodynamic (nose up/back stick) landings, the answer to your proposition remains as given in the other threads; it is to follow the manufacturers procedures.
Do pilots really think that they have discovered something new in aerodynamic breaking which manufacturers have not considered? If there were better techniques, then we would all be using them in our over competitive industry. The core of many manufacturers’ advice is to concentrate on the important and most effective means of stopping the aircraft, particularly by using maximum braking with all wheels firmly on the ground. Just because the aircraft is on the ground does not mean that the controls are ineffective and will not change the load distribution, you can lift the nose in many aircraft types even against brakes and reverse. The HS 125 for example can be steered on the runway with aileron even though full lift dump is deployed.

Some naval aircraft, which for obvious reasons may not have had the best brakes, were allowed to use aerodynamic braking for land based operations. However, there were many pilots who misjudged the runway length such that when the nose was lowered / effective braking applied, insufficient runway remained. These pilots would have been better placed to use full brake, even with the risks of brake fade or overheating, which would have required a tow off the runway; that situation would have been better than a tow out of the mud.

Similarly, my limited trials experience in landing on snow confirmed that the ‘keep it simple / back to basics’ advice for stopping was the most effective. Get the aircraft on the ground, right place, and right speed, lower the nose, and use max brake. The aircraft would stop ‘when it was going to stop’. The ground roll landing distances were measured very accurately in the fresh snow.
For trials reasons the conditions were at the limit or in excess of any runway condition approved commercial operations; be assured that neither I nor anyone else has need of any more experience of sliding uncontrollable down the runway hoping that it was long enough. Furthermore, if the cross wind had exceeded 5 kts I doubt that the aircraft would have remained on the runway, as both rudder and steering were ineffective.

Empty Cruise Re your comment “… since WET is a well-defined case performance-wise.”
I think that if you study the DoT Canada reference, you will find that wet is not as well defined as might be thought and in some cases has similar risks to operations on a contaminated runway, and that is before you think of aquaplaning or wet/flooded conditions.

tribo
2nd Jan 2006, 19:19
TheOddOne,

I therefore feel that the responsibility for determining the relationship between the FC (as measured by a given piece of test equipment) and the stop cabability of the A/C lies with the manufacturer (and the operator who applies the data) - end of story. They make the thing, they test it, they supply the data, we operate it.



Boeing "feel": (From 2003 Boeing Performance and Flight Operations Engineer Conference, Seattle, washington USA)

Question:
Does Boeing hava a position on how to relate runway friction chart information to reported braking action?

Response:
There are many different runway friction vehicles, which have not been calibrated to a standard measurement system nor the airplane. At this point Boeing does not correlate runway friction measurements to pilot reported braking actions or airplane braking coefficient.

Question:
Then how does (is) flight operations (to) determine what to use?

Response:
The slippery runway (landing and takeoff) data provided by Boeing is a function of airplane braking coefficient. Airplane braking coefficient is the percentage of the airplane's weight on the wheels (W-L) which is converted into an effective stopping force. For example, for a reported airplane braking coefficient of 0.20, an airplane with a (W-L) of 100,000 lbs would create 20,000 lbs of stopping force.

Boeing provides slippery runway data based on an airplane braking coefficient of 0.05 to 0.2 (Poor to Good reported braking action). Please review the following guidance for relating commonly used terms of reporting runway condition to airplane braking coefficient:

Followed by a table with headings:


Airplane Braking Coefficient
Pilot Reported Braking Action
Runway Description


And content:


0.4
Approximates dry runway
Friction limited certification values



0.2
Good
Wet Runway, Jar certification for compact snow



0.1
Medium/Fair
Ice, Compacted Snow



0.05
Poor/Nil
Wet Ice, Slush, Melting Compacted Snow, Standing Water


On a runway covered with wet ice, slush, melting compacted snow, or standing water the possibility of hydroplasning exists, which can result in nil braking capability. For that reason we recommend that the flight crew use the operational landing distance for POOR Braking Action in such conditions to determine the acceptability of landing on such a runway.

Airbus "feel"
Getting to grips with cold weather operations

http://www.wingfiles.com/

CORRELATION BETWEEN REPORTED MY AND BRAKING PERFORMANCEPlease bear in mind:


Airports release a friction coefficient derived from a measuring vehicle. This friction coefficient is termed as "reported MY".
The actual friction coefficient termed as the "Effective MY" is the result of the interaction tire/runway and depends on the tire pressure, tire wear, aircraft speed, aircraft weight and anti-skid system efficiency.
To date, there is no way to establish a clear correlation between the "reported MY" and the "effective MY". There is even a poor correlation between the "reported MY" of the different measuring vehicles.

It is the very difficult to link the published performance on a contaminated runway to a "reported MY" only.



The presence of fluid contaminants (water, slush and loose snow) on the runway surface reduces the friction coefficient, may lead to aquaplaning (also called hydroplaning) and creates an additional drag.
This additional drag is due to the precipitation of the contaminant onto the landing gear and the airframe, and to the displacement of the fluid from the path of the tire. Consequently, braking and accelerating performance are affected. The impact on the accelerating forces leads to a limitation in depth of the contaminant for takeoff.

Hard contaminants (Compacted snow and ice) only affect the braking performance of the aircraft by a reduction of the friction coefficient.



Airbus Industrie publishes the takeoff and landing performance according to the type of the contaminant, and to the depth of fluid contaminants.


EASA "feel":
From NPA 14/2004 Operations on contaminated runways
http://www.easa.eu.int/doc/Rulemaking/NPA/NPA_14_2004.pdf

7.3.3
Use of Ground Friction Measurement Devices

Ideally it would be preferable to relate aeroplane braking performance to a friction index measured by a ground friction device that would be reported as part of a Surface Condition Report. However, there is not, at present, a common friction index for all ground friction measuring devices. Hence it is not practicable at the present time to determine aeroplane performance on the basis of an internationally accepted friction index measured by ground friction devices. Notwithstanding this lack of a common index, the applicant may optionally choose to present take-off and landing performance data as a function of an aeroplane braking coefficient or wheel braking coefficient constant with ground speed. The responsibility for relating this data to a friction index measured by a ground friction device will fall on the operator and the operating authority.

Empty Cruise
2nd Jan 2006, 20:03
Alf & Tribo,

Thanks, v. good info.

When you sit in the aircraft - with the OM part C in hand - this manual has been promulgated by our operator and approved by the CAA.

Therefore, as long as I follow that manual - and once & again add a bit extra "common sense"-margin - I am legally speaking "off the hook". I know that there might be a protracted legal battle should something still go wrong - but the crew will come out clean.

I know that - even with the FC available - there will be cases where, even though the data available indicates that a landing is feasible, we will decide against trying. But that is a safety matter - before we get to that bridge, we need to sort out the matter of legality.

So - any thoughts on the legality aspect as seen from ATCO and FD crews' side? If we have the approved Part C and get a "reliable" FC from ATC - are we legal or not? That is quite an important question - and if the answer is not clear, we can tear out every 3rd page in the perf.manual :{

Thanks for the good input - Empty

Cough
2nd Jan 2006, 21:55
Overtalk.

The technique you describe has been responsible for a runway overrun.

Backstick lead to a positive angle of attack, which reduced the pressure on the mainwheels due to lift from the wing and in turn the braking effectiveness was reduced.

Follow the Flying manual advice!

tribo
2nd Jan 2006, 23:20
So - any thoughts on the legality aspect as seen from ATCO and FD crews' side? If we have the approved Part C and get a "reliable" FC from ATC - are we legal or not? That is quite an important question - and if the answer is not clear, we can tear out every 3rd page in the perf.manual :{



I am not a lawyer and will not comment on the legality. But please bear in mind that the Surface Condition Report are produced by the people on the ground. Not the ATC, who like you are up and above the ground.

The person on the ground are the one who "feel the stuff" and evaluate the condition at the movement area and the output from the (friction) measuring devices and report it to the ATC according to, by the State, regulated/approved format for further transmitting to the end user (operator/pilot).

(These formats do, unfortunately, vary from State to State)

The person on the ground take the desicion when to close the runway or any other part of the movement area for maintenance, preparation, etc and when to open for traffic by issuing a Surface Condition Report

alf5071h
3rd Jan 2006, 10:17
Empty Cruise “…are we legal or not?”
Just because the book states that something can be done, or that the Authority has approved the book, does not imply that operations on contaminated runways are lawyer proof or indeed sensible at ant time.

The Captain has the responsibility, a duty of care for the passengers, which is exercised through judgment and decisions. If there is an accident, most lawyers will walk all over the crew to get to the money – to the operator and the insurance. There is little that the crew can do to protect themselves except do what is right in the situation presented to them – but first make sure that the situation is understood. ‘What is right’ means avoiding accident prone circumstances and unnecessary risk, and by taking precautions to safeguard the aircraft and passengers.

When considering operations on contaminated runways, this means having knowledge of all advisory information, i.e. UK CAA AICs, FODCOMs, and JAR-OPS ACJs, etc, then with due judgment of this and all other information ‘in the book’, SNOWTAM, ATIS, the crew has to decide on the best (safest) course of action. There should be good guidance in the Ops Manual, if not then the best place to consider the decision is on the ground before any pressures of in-flight situations are encountered, as these are often associated with time/fuel and commercial issues that might bias judgment.
The crew need to understand the limitations of book data and runway condition reports, and the reduced safety margins these items provided; this should enable crews to determine a baseline standard for a safe operation. Then in-flight, the crew can apply judgment as to any detrimental effect of the actual circumstances such as cross wind, runway surface, concrete/tarmac, grooved/smooth, length available, landing weight as a % of max allowed (how close to the limit is this landing), and most important consider how each individual might have been biased in their judgment. Individuals need self discipline in their thinking, a need to cross check both information and understanding, and to question everything; these are central areas of airmanship. Then and only then have you the basis of a defense, legally or morally whichever applies.

The question to ask is not if the operation is legal, or if the crew will come out clean (which I doubt), it is whether each individual is satisfied with his or her performance. For advice of how to achieve that I refer to the following from Tony Hayes, CFI Brisbane Valley Leisure Aviation Centre.

”Airmanship is a personal attitude to flying, why we do it, how we do it. Airmanship must grow with training, experience, and personal exposure. It is not just about staying alive or not bending the airplane or yourself, it is about walking off the airfield knowing that you have both performed and crafted an activity. You have been totally aware of what you have done and why you enjoyed it, and at that point you owe nothing to anyone”.

Short Approach?
3rd Jan 2006, 13:24
The person on the ground take the desicion when to close the runway or any other part of the movement area for maintenance, preparation, etc and when to open for traffic by issuing a Surface Condition Report


Neither I (ATCO) or the ground guy whoo does the measuring will take steps to close a runway. He reports what he sees and measuers, I relay the report to the A/C´s, and then it´s ultimately their decision.

Someone is always willing to be the guiney... I guess it´s the same mechanism that will sometimes drive me to tweak the rules just to make the weels go round. Eventhough I can be certain to have my b**** chopped of, if something goes wrong. :yuk:

tribo
3rd Jan 2006, 15:48
Neither I (ATCO) or the ground guy whoo does the measuring will take steps to close a runway. He reports what he sees and measuers, I relay the report to the A/C´s, and then it´s ultimately their decision.


Ever heard about GASR?

http://www.airports.unina.it/

They have a Working Paper 061 Aspects related to winter mintenance of aerodromes, hereunder contamination measurement and reporting.

http://www.airports.unina.it/WP%20061%20.pdf

With four appendix:
http://www.airports.unina.it/WP%20061%20Appendix%201.pdf
http://www.airports.unina.it/WP%20061%20Appendix%202.pdf
http://www.airports.unina.it/WP%20061%20Appendix%203.pdf
http://www.airports.unina.it/WP%20061%20Appendix%204.pdf

There exist a draft GASR Working Paper, (not publihed) from where i quote:


Introduction

Winter operations are among the most challenging flight operations. During winter the weather is worse, with low cloud base, reduced visibility and heavy winds, and in addition the runways often are covered with snow and ice.

The GASR AGA WP061 – “Aspects related to winter maintenance of aerodromes, hereunder contamination measurement and reporting”- stated that predicting aircraft braking action based on friction measurement is more complicated and unreliable than earlier assumed. Further it was realised that the way of reporting runway status to aircrew varies among GASR states.

During the winter 1999/2000 Norway experienced a number of runway veer-offs/overruns on contaminated runways. Thereafter the CAA-Norway focused on winter operations and one result was the new requirements for runway status reporting. The revised reporting gives special attention to the great uncertainty related to the measurement of friction level and depth of deposits.

However it is of vital importance for safe winter operations that reporting of runway status can never be a substitute to the removal of deposits of slush, snow or ice. Aviation authorities should therefore require that the aerodrome operator establish exact criteria for winter maintenance of runways and other parts of the movement area and to deny operations on areas not meeting the established criteria. The requirements for a safety management system should further assure that if a risk analyses concludes that the runway conditions are not acceptable, then the runway should be kept closed until the conditions becomes acceptable.

In the Norwegian regulation BSL E 4-1 and 4-2 the Authorithy requires closing criterias to be established. (Norwegian text)

http://www.lovdata.no/cgi-wift/ldles?doc=/sf/sf/sf-20030627-0935.html

http://www.lovdata.no/cgi-wift/ldles?doc=/sf/sf/sf-20040427-0670.html

Empty Cruise
3rd Jan 2006, 17:14
alf5071h,

The question to ask is not if the operation is legal, or if the crew will come out clean (which I doubt), it is whether each individual is satisfied with his or her performance.

While I agree on the definition of airmanship, being denied part of the data (the FC) does not exactly help in exercising that airmanship. Wouldn't it be much safer - airmanship-wise - to give the crew the FC (where available) and then let them decide for themselves?

Secondly, even the best airmanship only covers up to a 99,9% CEP - we all need to know where we stand when the last 0,1% strikes. 100% CEP is only achievable if you leave the aircraft on the ground & go home :(

If I'm told that FC is unreliable - and no pilot reports exist - we're out of there, end of story. My concern is the pure legality of using the existing aeroplane data, as processed & promulgated by my operator, based on unambigous FC values transmitted by ATC. These conditions are encountered by pilots all over the world every year - and we're all able to operate safely under these conditions.

So - leaving the airmanship aside (I doubt anybody here wants to disagree with any of the above posts on the airmanship issue) - we return to the legality aspect of things. If the operators maintain that their data is only advisory & that the use of this data is responsibility of the operator, and we use the data as issued by our operator - where do we stand legally? :hmm:

Empty

OVERTALK
3rd Jan 2006, 17:47
ALF5071H said (Overtalk comments interspersed in blue)OVERTALK Having been involved with a few military and civilian aircraft trials relating to aerodynamic (nose up/back stick) landings, the answer to your proposition remains as given in the other threads; it is to follow the manufacturers procedures. Hasn't anything whatsoever to do with aerodynamic braking (note spelling of "braking"). In fact it's quite silly to attempt to equate aerodynamic braking with what's being suggested. What's being advocated is a progressive and tempered introduction of backstick once nosewheel is on, spoilers are deployed, reverse is selected and braking has commenced. Note that all three of those traditional retardation measures cause a strong nose down pitching moment. Trying to pretend otherwise is very "imaginative" - unless your a/c sports a tailwheel...... so the nose will NOT rise. Even without those three cumulative nose-down pitching moments, a normal CofG distribution will accord a nose-down moment.

Do pilots really think that they have discovered something new in aerodynamic breaking[sic] which manufacturers have not considered? If there were better techniques, then we would all be using them in our over competitive industry. The core of many manufacturers’ advice is to concentrate on the important and most effective means of stopping the aircraft, particularly by using maximum braking with all wheels firmly on the ground.The advocated technique is merely a means of very quickly getting maximum weight upon wheels (or as you say, all wheels firmly on the ground - aka traction). This minimizes the intervention of anti-skid, which makes braking less effective the more it has to cut in to maintain wheel rotation. Remember that it's stopping the wheel that blows the tyre. Two ways of NOT stopping the wheel = antiskid (decreases braking effectiveness) and utilizing UP elevator to push the maingear into the pavement. Just because the aircraft is on the ground does not mean that the controls are ineffective and will not change the load distribution, you can lift the nose in many aircraft types even against brakes and reverse. The HS 125 for example can be steered on the runway with aileron even though full lift dump is deployed.

Some naval aircraft, which for obvious reasons may not have had the best brakes, were allowed to use aerodynamic braking for land based operations. However, there were many pilots who misjudged the runway length such that when the nose was lowered / effective braking applied, insufficient runway remained. These pilots would have been better placed to use full brake, even with the risks of brake fade or overheating, which would have required a tow off the runway; that situation would have been better than a tow out of the mud. Some very muddy and irrelevant thinking here. Best to stick with aerodynamics rather than anecdotal bombast and bluster...

Similarly, my limited trials experience in landing on snow confirmed that the ‘keep it simple / back to basics’ advice for stopping was the most effective. Get the aircraft on the ground, right place, and right speed, lower the nose, and use max brake.Couldn't agree more. However most overruns are caused by pilots making human errors, perhaps due to illusion, perhaps fatigue, possibly indecision. The recommended "introduced backstick" technique may have made all the difference at Toronto and Midway. I reiterate that it is merely a very effective method of adding main-wheel traction on contaminated runways for increased braking effectiveness - and one that has been widely overlooked and apparently, is only being used by a competent few. When you are surrounded by variables and indeterminants such as unreliable and optimistic braking action reports, downdrafts, skittish tailwinds and mu-meter readings, it is always nice to have a big trick up your sleeve. Those that don't will always be the ones that make the headlines and have to go find another career. Blindly believing that the manufacturer knows all and tells all is for blind men. The aircraft would stop ‘when it was going to stop’. The ground roll landing distances were measured very accurately in the fresh snow.
For trials reasons the conditions were at the limit or in excess of any runway condition approved commercial operations; be assured that neither I nor anyone else has need of any more experience of sliding uncontrollable down the runway hoping that it was long enough. Furthermore, if the cross wind had exceeded 5 kts I doubt that the aircraft would have remained on the runway, as both rudder and steering were ineffective.

alf5071h
3rd Jan 2006, 21:08
Empty Cruise “… where do we stand legally?"
Not being legally qualified I cannot say, but having been on the correct side of the dock in the aftermath of an accident, I can only share my opinion as above.
Again, from my experience, lawyers only offer advice.

If all data is advisory the debate might be whether the pilot is the best person to make the judgment, and then probably not to make that judgment in the air.
Current contaminated runway operations involve a higher level of risk than that accepted in normal operations. The regulatory authorities appear to accept this, although there is evidence that not all of them understand the risks (see Tribo’s posts). The advice that would assist pilots in making their judgment in those situations that change the basic risk assumed by the authority and ops manual, appear to be weakly presented and poorly disseminated.
Some of the best advice that I have seen is in AIC 61-99 “Operations from contaminated runways, by all classes of aeroplane, should be avoided whenever possible”.
If your lawyer gave you that advice, what would your decision be?

“These conditions are encountered by pilots all over the world every year - and we're all able to operate safely under these conditions”.
This is a misnomer; accident statistics show that overruns now contribute a high proportion of hull losses or major damage (not fatalities) and are of growing concern to the industry (and insurers).
A safe operation is a relative term; you are safe until you have an accident. In addition, public perception (heightened awareness in the press) often determines ‘safety’.
Remember that members of the public form the jury.

alf5071h
4th Jan 2006, 16:20
OVERTALK the differences in our views might only be balanced with data provided by tests which you called for. My experiences were from tests, which provided data, but only applied to a few aircraft. Further, wider discussion could debate the applicability of your beliefs or my experiences to other aircraft types, but without facts, we would be speculating, albeit from informed positions.

A more responsible view within a thread relating to one of several recent accidents is to focus on the facts, what the manufacturer advises. It would be remiss of us to advise others to try unproven techniques during a critical event; it is far better, as I believe we agree, that crews are encourage to focus on the basics.
I would willingly discuss this topic further off line, or in the flight testing forum.

I also believe we would agree on the contribution of human error in overrun accidents, but I do not subscribe to your view of error.
Recent views of human factors prefers to avoid stating that humans make errors; we do not deliberately set out to make an error. Error is a description of behavior applied after the event; it is one possible explanation of the event.
Thus, as an alternative view, humans are exposed to error provoking situations and may be predisposed to erroneous mind set or judgment based on experiences or knowledge.
This thread has already identified significant opportunities for error; we should not contribute further to any erroneous mind set with inappropriate knowledge however well intentioned.

freddyfokker
4th Jan 2006, 20:31
I work for a large european operator.

In our manual in the absence of reliable breaking action we have a clear guide in which we can assume braking action.

eg: dry runway, wet runway with otherwise good conditions = good
moderate heavy rain on clear runway or ice, snow on sanded runway = medium
all other = poor.

So if the braking action is unreliable and any other contaminents are within the aircraft performance i can land.

Why should an airport close just because ther is no blacktop. As hapened recently. they would not let anyone operate.

So when it is a dark night and there is a tiny bit of ice or snow lets say 2mm calm winds and braking action we will assume is poor, I should be at least be able to excerice my judgement within the guidelines of my opeartor and the aircraft manufacturer to decide whether to land or not. WE can land on braking action poor, under strict limits.

It is , in my view, unacceptabale for an airport to then close until blacktop is reached. This has the potential of undermining the entire flight planning process.

If uk airports are going to adopt this closure of airports until the can guarentee braking action good then please issue a warning to all operators world wide that a non uk diversion must be planned in winter ops. As only then may you be allowed to land.

This must get sorted.

safetypee
4th Jan 2006, 21:13
It is, in my view, unacceptabale for an airport to then close until blacktop is reached. This has the potential of undermining the entire flight planning process.
It would be better for an airport to close rather than have someone off the end and shut the runway in that way. At least with contamination it might be cleared in an hour, but an aircraft in the mud, or worse still an accident site might take days to sort out.

Short Approach?
5th Jan 2006, 20:59
It would be better for an airport to close rather than have someone off the end and shut the runway in that way. At least with contamination it might be cleared in an hour, but an aircraft in the mud, or worse still an accident site might take days to sort out.

Complete rubbish!

We are taking initiative away from the person who is really in charge.


Ultimately it's a matter of declaring an emergency then, if you want to land in England during winter-contamination then. :confused:

Dash-7 lover
6th Jan 2006, 09:47
Having read the original post - any idea on the aircraft or owner???

Short Approach?
6th Jan 2006, 16:52
Having read the original post - any idea on the aircraft or owner???

There was no A/C of the tarmac that night, as you would have found reading a bit further on.

OVERTALK
8th Jan 2006, 03:18
See also this thread on the subject of stopping techniques that are very appropriate for contaminated runways:

http://www.pprune.org/forums/showthread.php?t=204897

.
OT