Overweight Landing and Field Length

[Haroon]

Hello. I am looking for some feedback on the following scenario:

1) B737-300 Take off at 59000 Kg.

2) Flight has to be discontinued and a land back is required at the departure aerodrome. Reason for land back is Depressurization. However no emergency situation requiring to land ASAP. Everything (including passengers) under control.

3) Max landing weight is 52000 Kg.

4) Unfactored landing distance (for 59000 Kg) is around 5700 feet.

5) Factored (1.67) landing distance is 9500 feet.

6) Landing runway is 9000 feet.

7) Runway condition is Dry. Night time and a non-precission (VOR) approach is in progress. Weather and visibility is not an issue.

8) No contact with the company for any assistance regarding making a heavy or a normal landing.

9) Burning 7000 Kg of fuel to bring the landing weight to normal limit requires 2 hours holding as fuel jettison is not possible.

10) No overweight landing procedure in the checklist.

Considering the above mentioned scenario, what will you do? Choose one of the following options:

A) Make a heavy weight (7 tons above limit) landing, based on unfactored landing distance of 5700 feet. Considering that runway is 9000 feet and safety factor of 1.67 is only for dispatch (pre-flight planning) purpose. Intention is to save fuel and 2 hours holding time.

B) Hold for 2 hours and reduce the A/C weight to avoid complications of a heavy weight landing in addition to bringing the factored landing distance of 9500 feet (at heavyweight) to less than 9000 feet (at normal landing weigth) to cater for the field length of 9000 feet. This would be based on the fact that the A/C is not in a state of emergency and safety factor of 1.67 can still be applied to avoid unnecessary complications in order to save fuel cost and holding time. Intention is to enhance safety.

C) Some other better course of action - please mention.

Looking forward to atleast 5 or more opinions on this issue. Thankyou.

[Checkboard]

Boeing guide on overweight landings (I know you didn't mention type, but we are talking general principles here) basically says that anything technical enough to require a return will probably require more engineering time than the overweight landing inspection. The aircraft is designed to land at MTOW without a problem, and I am confident enough in my skills to land. Night and VOR approach doesn't affect anything.

I would land - 7000kg of fuel and 2 hours flying time is a lot of money.

[Haroon]

Thankyou Checkboard. Would you like to comment on using the safety factor of 1.67 i.e. it is required for a normal landing in routine but why not when you are making a heavy landing when it is needed more as compared to a normal landing.

[OPEN DES]

First of all it would be the unfactored ALD that you would apply since you're in flight. The 1.67 only applies to the planning-stage, as you pointed out.

The answer to your scenario is:
'It depends..........'

Why do you have to discontinue your flight to destination? Are you landing performance limited at current weight?
When on fire I would definitely land ASAP applying the overweight landing c/l or not (time permitting).
With just a relatively small failure it would perhaps be more sensible to burn off the fuel in the hold in a high drag config.
Inter-polate between the two examples above and you will have your answer.

[Checkboard]

I once took off from Perth (Western Australia) in a BAe 146, and had a cabin fan failure. This means absolutely nothing in terms of the QRH, or continuing the flight - however it does mean that, should a cabin smoke event occur, you couldn't clear the cabin of smoke.

Continued flight was fine, however the MEL wouldn't allow you to take off with the problem, and we were planned to a no-engineer port (as were most of our ports in Australia). So a "perfectly fine" aircraft (short of a cabin fire), but the company wanted us to return to Perth were we had engineering, and we were a couple of tons overweight.

The decision was made eventually to hold over the water (out of the way of arrivals) for 40 minutes with the gear down and airbrake open in order to burn off the fuel. Well the passengers became increasingly nervous about the vibration, despite several PA's from the Captain (I was an FO), including one in the cabin, and we nearly ended up with a riot - the passengers convinced themselves we couldn't land, and the vibration was the "real problem" - in effect, they thought we were lying to them! :ugh:

So that is a consideration as well! :suspect:

Would you like to comment on using the safety factor of 1.67 i.e. it is required for a normal landing in routine but why not when you are making a heavy landing when it is needed more as compared to a normal landing.The extra weight is taken into consideration in the landing calculations, the 1.67 factor is to allow for either floating (less likely when you are nervous about landing overweight) or "skidding", so the only time I would think it is "needed more" is with a slippery runway. The weight isn't a problem.

[safetypee]

Haroon one of the ‘five or more opinions’ on how to judge the landing distance required is to consider the factors in the certification and assumptions in preparing the normal, factored landing distance – knowledge and then application.

The 1.67 factor (1.92 if wet) provides a margin of safety to reduce the probability of an overrun by allowing for variability in normal landings.
The airspeed and altitude accuracy expected at the threshold are critical factors. In an emergency, a pilot might claim to fly with greater accuracy, and achieve the expected touchdown position. However, assuming that you are not well experienced in overweight landings, and with the stress of the unusual situation, then some allowance should be made for possible unfamiliarity with the aircraft at that weight. Possibly a slower pitch/power response or operating nearer the wing lift curve limits – wings bend more at high weight.
These points would suggest considering the touchdown at approx 1200ft beyond the threshold as a minimum (probably 500ft above the unfactored distance) and a further 500ft for not deploying spoilers / reverse, and not braking as quickly as the test landings demonstrated in obtaining the data. Then add another 500ft for possible +10ft, +5kts at the threshold (AC91-71), or should this be +10kts – does everyone land fast at night. Do not unduly pressure yourself, stay as close as you can to normal operations.

You did not specify if the unfactored distance was wet or dry, or included the airborne distance (Boeing data usually doesn’t include the 1000ft+ from threshold to touchdown) – know before you go.
So including air distance, you need 7200ft (5700+500+500+500), but without air distance at least 8200ft – check wet/dry. Then ask yourself why the dry (1.67) factored distance is 9500ft, and how many overruns have there been this year.

Consider the brakes; any factor less than 1.67 probably requires max brakes until you are absolutely sure of stopping; is there likely to be a brake energy limit. Also consider the runway surface, wet/dry, grooved or smooth, and how much overrun is there. Check runway slope and wind values if not in already the book factor – double check the wind, make allowance for any reporting errors.
You may not wish to, or have the capability for a go around (obstacles), thus plan a more conservative approach and provide additional margins.

After considering all of the above, consider again what the landing distance factor is for – a margin of safety; what further addition would you add for safety.

You state that there is an option to burn off fuel. Safety must always come first; take option (B), as any non-normal (overweight) landing will involve some risk. Even with a much longer runway why take the risk on commercial grounds – you still have to answer for the consequences if anything goes wrong.

If you have to land immediately then accept reduced margins of safety – greater risk, but always consider the operational consequences; consider what mitigating actions can you take. By doing this, you pre-prepare your answers; lawyers usually state “always do what is right – do what you can justify”.
Beware advice from other people, they may not understand the situation from your point of view, or the safety of the operation; don’t assume that others have the same understanding. Yes, consider all advice (use all resources), but you have to decide on the safest course of action.
Fuel cost and time do not always equate to safety, the pilots first priority is safety. If you think that an overweight landing has the same level of safety as a normal landing then be prepared to prove it.

Re the ‘factors only apply at dispatch’; many regulatory airworthiness authorities imply that the factor should still be used at destination after checking the actual conditions. Remember that in the event of an accident, the regulators may have to defend their position; if a factor is required at dispatch to reduce the probability of an overrun, then what has changed at the destination – are they going to accept a higher probability of an overrun. Whichever way the regulators call the game, the pilot holds the final accountability in the decision to land.

Landing performance of large transport aeroplanes. (www.nats-uk.ead-it.com/aip/current/aic/pink/EG_Circ_2006_P_014_en.pdf)

AC 91-71 Runway Overrun Prevention. (www.airweb.faa.gov/Regulatory_and_Guidance_Library/rgAdvisoryCircular.nsf/0/0052F2A2A00D91B28625738E0071E44C?OpenDocument&Highlight=ac%2091-79)

Managing Threats and Errors during Approach and Landing. ( www.skybrary.aero/bookshelf/content/bookDetails.php?bookId=874)

[Intruder]

You have to answer a few questions in your own mind in real time:

Is the situation critical -- does it endanger the airplane or those aboard?

Are the conditions such that you can make a successful landing, rollout, and stop?

Is the current inflight situation more dangerous than the IMMEDIATE risks of overweight landing?

Any 2 YES answers likely dictate an overweight landing. You will then have to evaluate whether the risk of the X hours burning fuel is less than the risk of the overweight landing.

Most of these will be subjective, except landing distance on a dry runway...

[Haroon]

Before continuing further I would like to present the summary of documents which Safetypee has provided, in reference to using the safety factor for landing performance.

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FAA Advisory Circular (AC No: 91-79 ) on Runway Overrun Protection.
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- The unfactored landing distances in the manufacturer-supplied AFM reflect performance in a flight test environment that is not representative of normal flight operations. The operating regulations require the AFM landing distances to be factored when showing compliance with the predeparture landing distance requirements. These factors are intended to account for pilot technique, atmospheric
and runway conditions and other items to ensure that the filight is not dispatched where it will be unable to land.

- As part of the operator’s Safety Management System (SMS) and SOP, the FAA recommends using either factored landing distances or adding a safety margin to the unfactored landing distances when assessing the required landing distance at the time of arrival. This landing safety margin should not be confused with the regulatory predeparture runway requirements.

- Operators should use the appendices, which contain detailed information about all of these hazards, to develop their SOPs. The 15 percent safety margin additive recommended by the FAA is intended only to account for slight variations in achieved performance.

- The unfactored certified landing distance may be different fom the actual landing distance because not all factors affecting landing distance are required to be accounted for by certification regulations.

- A survey of numerous operators’ Flight Operations or General Operating Manuals by the FAA’s Landing Performance Team indicated that approximately 50 percent of the operators surveyed did not have adequate policies in place for assessing whether sufficient landing distance exists at the time of arrival at the destination airport. Not all operators performed landing distance assessments at the time of arrival nor did all of the operators who performed assessments account for contaminated runway surface conditions or reduced braking action reports, nor did they apply a consistent safety margin to the expected actual landing distance. Operator specific SOPs should be developed for the assessment of landing performance, including the application of a safety margin, to ensure a consistent evaluation of airport conditions at the time of arrival.

- Unfactored landing distances determined in compliance with certification regulations and published in the FAA-approved AFM do not reflect operational landing distances. Landing distances determined during certification tests are aimed at demonstrating the shortest landing distances for a given airplane weight with a test pilot at the controls and are established with full awareness that operational rules for normal operations require the addition of factors to determine minimum operational field lengths.

- Flight test and data analysis techniques for determining landing distances can result in the use of high touchdown sink rates (as high as 8 feet per second) and approach angles of 3.5 degrees to minimize the airborne portion of the landing distance. Maximum manual braking, initiated as soon as possible after landing, is used in order to minimize the braking portion of the landing distance. Therefore, the landing distances determined under §§ 23.75 and 25.125 are much shorter than the landing distances achieved in normal operations.

- Aircraft Landing Weight. Calculate the anticipated landing weight by starting with the aircraft gross takeoff weight at departure and subtracting the anticipated normal consumption of fuel and oil required to arrive at the destination airport. If en-route fuel burn is less than planned, then the aircraft will arrive at the destination at a weight heavier than planned. Therefore, a recalculation of the aircraft’s landing performance must be done prior to attempting a landing maneuver. The pilot may control the landing weight by adjusting fuel burn en route or decreasing fuel load or payload prior to departure.

- Touchdown Point. Extended flare and runway slope are two factors which affect pilot control of the touchdown point. Turbine airplanes should be flown onto the runway being held off the surface as speed dissipates. A firm landing is both normal and desirable. An approach flown using a 3.5 degree glidepath with a touchdown at 8 feet/sec. rate of descent witouchdown down at the target touchdown point, which for certification purposes is approximately 1,000 feet beyond the runway threshold. The typical operational touchdown point
in the first third of the runway, and it may be farther down the runway than the 1,`000 fpoint. This additional distance should be accounted for in the landing distance assessment at the Air Safety Foundation Approach-and-Landing Accident Reduction (ALAR) Briefing Note 8.3, each 1 percent of runway down slope increases the landing distance by 10 percent.

- SOPs should clearly outline procedures to accommodate changes from the original plan. Preplan contingencies. Include the safety margin (factor) required by company SOPs or the appropriate regulation in all landing distance calculations. SOPs should address a process for conducting a landing distance assessment

- Develop procedures to ensure that a full stop landing, with a reasonable safety margin beyond the actual landing distance, can be made on the runway to be used.

- In the absence of other specific guidance, and to ensure that an acceptable landing distance safety margin exists at the time of arrival, the FAA recommends, as a best operating practice, that a 15 percent safety margin be applied to the actual airplane landing distance at the time of arrival. The 15 percent safety margin accounts for actual performance considering the meteorological and runway surface conditions, airplane configuration and weight, and the utilization of ground deceleration devices.


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U.K. Aeronautical Information Circular AIC 14/2006 (Pink 91) on Landing Performance of Large Transport Airplanes
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4.3.1 Another common factor in landing overrun incidents is a deep touchdown, which is most usually caused by excessive height at
the threshold. An additional 200 ft of runway is needed for every 10 ft of excess height at the threshold.

4.3.2 An extended flare, concluding an otherwise accurate approach, might result in a smoother touchdown, but will use up valuable
runway in the process. Aeroplanes can decelerate far more quickly on the ground than by floating along just above it. This merely
reduces the available runway length in which the stopping procedures can have effect.

4.3.3 An additional factor to consider is that for a given threshold height and glideslope angle, a downhill runway will tend to yield an
increased distance from threshold to touchdown compared with a level runway, if allowance is not made in the flare manoeuvre.
Runways with a significant amount of downslope at the beginning of the landing run are most likely to cause problems in this area, and
those in the UK are now highlighted in the AIP.

4.3.4 The conditions that create optical illusions which give misleading indications of height relative to the glidepath, created by, for
example, sloped runways or by particularly narrow or wide runways are well known and should be anticipated when such
characteristics are encountered. To help compensate in conditions where the visual perception of the flight path during a visual
approach may be affected, all available runway approach aids should be utilised.


Inflight re-check of Landing Performance

As stated earlier, an aeroplane's suitability to land at the intended destination is predicted upon forecasts at the time of despatch.
order to ensure that the assumptions made at despatch remain valid, JAR-OPS 1.400 prescribes an inflight re-check requirement,
requires the commander to satisfy himself prior to commencing an approach to land, that a safe approach and landing can be
made, taking into account the actual state of the aerodrome. This re-check is particularly important given that JAR-OPS 1 permits
despatch on the basis of dry landing distances if the landing runway is forecast to be dry at the estimated time of landing.


Any significant departure from the flight plan, such as an unscheduled diversion, would clearly justify a review of the landing
performance. If such a diversion was as a result of an emergency aeroplane condition which necessitated a prompt landing, then
clearly this would be justification for contemplating a landing on a runway which, although nearby, could not fully accommodate the
increase in the factored LDR due to the failure condition. Such a decision requires a sound knowledge of the principles involved to
make an assessment of the conflicting considerations.

[Haroon]

Message To Everyone:
----------------------------

I have updated my first post and have added the following details as many of you wanted to know for a proper answer.

A/C type: B737-300

Reason for land back: Depressurization. However no emergency situation requiring to land ASAP. Everything (including Passengers) under control.

Runway condition: Dry

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To OPEN DES
----------------------

Thanx for your response. I have updated the scenario to be more precise. Now what do you say.

To CheckBoard
--------------------
Thanks again for your response. Your incident is really interesting and i can imagine what passengers, at times, can turn to! :)

Considering the summary of what Safetypee suggested, do you still think that saving fuel and time is a better option as compared to using the factored landing distance.

I agree that extra weight has been catered for in the performance but if safety margin is required at normal weights then why not otherwise, especially if the situation is not Land ASAP. Is there anything that stops from using the safety factor once airborne?

Quoting Safetypee:
"if a factor is required at dispatch to reduce the probability of an overrun, then what has changed at the destination – are they going to accept a higher probability of an overrun"


To Safetypee
----------------

Thanks for the useful Links. I have updated the scenario to be more precise. Do you still have the same answer.

Quoting Checkboard:
" The extra weight is taken into consideration in the landing calculations, the 1.67 factor is to allow for either floating (less likely when you are nervous about landing overweight) or "skidding", so the only time I would think it is "needed more" is with a slippery runway. The weight isn't a problem.

So if the runway is dry, is it still worth it to waste 7000 Kg of fuel and 2 hours operational cost? I mean anyone would like to go for safety but considering a huge cost isn't 67% safety factor a bit too much. According to the AC 91-79 even FAA suggests 15% safety which is different from dispatch safety factor.


To Intruder:
---------------
Thanx for your post. I have updated the scenario to be more precise. Now what do you say.

[OPEN DES]

Thanks for the extra info Haroon.
I would definitely burn-off the fuel to be below MLW (either structural or performance limited) in this scenario. Best to do this in a high drag situation (low and dirty).

I would not deliberately do an 'overweight landing' (not knowing how critical this is in your type and/or if there is a procedure available).
In my a/c type (A320) an overweight landing is an abnormal procedure; in my view only an emergency situation would warrant deliberately doing an 'abnormal' landing when a normal landing (albeit delayed) is available.
Time permitting you could perhaps liaise with the company/maintenance through ACARS/company VHF to let them consider the implications (cost) of an overweight landing.

I remember once we were overfuelled (over MLW) and there was no defuelling available. We had 2 options:
-increase fuelburn (high speed, lower level, early config)
-doing an overweight landing hereby voluntarily making an 'abnormal situation' out of something nominally 'normal'
We chose the 1st option for obvious reasons.

Hope this helps

[rudderrudderrat]

Hi Haroon. If there was no technical reason to Land ASAP, then you can't land over maximum certified weight (52 Tons?) for commercial reasons.

I would have held until I'd burned the excess weight off.

[Intruder]

To Intruder:
---------------
Thanx for your post. I have updated the scenario to be more precise. Now what do you say.
Saving time & fuel is a noble quest. However, are you sure the departure airport is your only option? If not, consider another suitable alternative within your 2-hour hold time.

At what weight will your "factored" landing distance equal the runway length? Why is a 1.67 factor used in the first place? Is it used simply for additional margin for a rejected T/O, or is there some kind of landing consideration? Does it include use of reversers? Autobrakes? Full braking? Normal braking?

If your 5700' figure includes air distance from threshhold to touchdown point, and normal braking, I see no reason to wait for landing due to the runway length. If the crew is reasonably proficient, even the lack of ILS should not be a problem, especially if VASI or PAPI is available..

[Cough]

Always consider whether a lawyer could make mince meat of you if an incident were to happen on that landing. :ok:

[safetypee]

Haroon, in virtually all situations, particularly the one which you describe, then the safest option should be taken, I remain with option (B). If you judge that you can do otherwise then you have to be prepared to justify your decision – possibly in the worst of circumstances, an accident which was not foreseeable or necessarily of your making. You would still have to justify why you were flying the chosen option where the safer alternative may not have resulted in the accident factors coming together. Consider a hindsight view and turn it into foresight.

Re your quote from Checkboard; I don’t believe that this view necessarily agrees with the assumptions held by the certification agencies.
Currently I am unable to locate any regulatory material to support this. However, the following is taken from a 2002 certification conference:
“There is no readily identifiable underlying technical explanation of the operational landing distance factors, which have existed for some time” and “The factors have now become ‘accepted’ as providing a satisfactory safety record. However, subsequent research into the industry’s concerns about overruns reported:-
For dry runway the current operational factor of 1.67 for both Destination and Alternate airports appears to be reasonable
For wet runways, without reverse thrust:
1.92 for Destination airport appears to be low
1.67 for Alternate airport appears to be really low
For wet runways, with reverse thrust:
1.92 for Destination airport appears to be marginal
1.67 for Alternate airport appears to be low
Flight Working Paper 730 and Transport Canada Aircraft Certification Flight Test Division Discussion Paper No. 22

From the Loughborough University Report “A New Aircraft Overrun Database 1980-1998 based on data from “English-speaking world”:
A high proportion of overruns involve near or over maximum weights
Three times as many overruns in landings than aborted takeoffs
Wet runways, contaminated runways and tailwinds are factors in many overruns, particularly landing long and fast.

The overrun accident rate in recent years might suggest that the industry is operating too close to limiting conditions, particularly with respect to human judgment; thus this links with Intruder’s comments (#14).
Once we entertain the thought that we might be able to land overweight, then we suffer bias – a tendency to find supporting information. The example questions given seek to justify the factor; none of which individually or collectively are sufficient or correct.
The factor (in UK CAA terms) is a landing distance safety-factor. It identifies with that undefined margin that we should seek to provide in all of our flying.
Instead of thinking ‘can we land’, we must question our assumptions and consider ‘should we be landing’ in these conditions.

[john_tullamarine]

A few thoughts ..

Flight has to be discontinued and a land back is required at the departure aerodrome. Reason for land back is Depressurization. However no emergency

Then one would suggest that the land back is desired, rather than required, and one would be looking to observe all regulatory requirements as part of one’s decision process. One needs to keep in mind that the MLW is a Type Certificate limitation and, as such, is an underpinning factor in the aircraft’s design airworthiness.

Landing over gross for convenience would be a bit like trying to explain to the nice policeman that you were doing 110km/hr just before he pulled you up ... because the speed limit changed in the next few km, anyway, and you were saving the company some travelling time .... I have discovered, in my occasional discussions with the good constabulary folk, that that sort of argument has never worked really well ...

A) Make a heavy weight ... landing.. Intention is to save fuel and 2 hours holding time.

Hard to argue when the Regulator seeks to revoke your licence ?

B) Hold for 2 hours and reduce the A/C weight .. Intention is to enhance safety.

A good call, I suggest.

C) Some other better course of action

B) is a conservative strategy and you could quite easily plan with a bit more finesse to land pretty well right on MLW.

The aircraft is designed to land at MTOW

Irrelevant if the AFM limit is MLW and MLW is less than MTOW

I would land - 7000kg of fuel and 2 hours flying time is a lot of money.

Fine, but would you not then chose to engineer an emergency situation for the record ?

The 1.67 only applies to the planning-stage

I suggest not, unless you have an emergency and chose to invoke the emergency powers of the commander .. and, even then, you may need a good story for the investigation ...

The answer to your scenario is: 'It depends..........'

exactly

Inter-polate between the two examples above and you will have your answer.

Distances will be related to a quadratic sort of relationship rather than linear so a simple interpolation needs to be approached with some care.

So a "perfectly fine" aircraft (short of a cabin fire), but the company wanted us to return to Perth were we had engineering ... hold over the water

The commander gets paid to think on his/her feet. Some discussion with ops/eng and a sensible decision is the result.

the passengers became increasingly nervous about the vibration ... and we nearly ended up with a riot

Sandgropers .. what did you expect ?

The extra weight is taken into consideration in the landing calculations

Run that one past us again ? The landing calcs are for the declared weight .. if there is some “extra” weight involved, then the calcs change accordingly.

the 1.67 factor is to allow for ..

The raw FT data should be viewed as being unachievable. Even the TP couldn’t do it every time. What may end up as the base, unfactored, data in the AFM may have a little bit of negotiated fat but still represents a routinely unachievable brick wall.

Whatever regulatory factor (generally 1.67) is applied covers all those other reasonably expected things which might cause a problem and seeks to achieve the relevant failure rate which is built into the certification process.

Boeing data usually doesn’t include the 1000ft+ from threshold to touchdown

Can you cite any objective evidence to support this claim ?

So if the runway is dry, is it still worth it to waste 7000 Kg of fuel and 2 hours operational cost?

You don’t have the option. If the situation is not an emergency then the normal operational/certification standards must apply.

let them consider the implications (cost) of an overweight landing

And what are your considerations regarding the implications of the regulator’s seeking to revoke your licence ?

Why is a 1.67 factor used in the first place?

Unfortunately I don’t have sufficient information to comment with any authority on the specific factor.

However, in the olden days, the early regulators had to come up with a range of arbitrary “seems a good idea” figures to start the process going. These were then varied, as necessary, on the basis of historical accident data.

So, for instance, the 70 mph single stall speed was a FITWWAG which still is enshrined in FARs as 61 kts ... the 50 ft approach height clearance likewise came from the trees around a military parade ground ...

One would need to dig into the ancient archives to follow the history through to determine the origin and sequence for the present factor presuming that were possible .. but, I suggest, it will have followed the basic philosophy described above.

Always consider whether a lawyer could make mince meat of you if an incident were to happen on that landing.

Whatever story you come up with after the event, the legal system is going to endeavour to hang you out to dry and go for both the jugular and the deepest pockets.

Every time you take it upon yourself to be innovative, you stick your neck on the figurative chopping block ... I am convinced that all pilots, maintainers and engineers should review, if not be involved in, significant legal actions following serious or fatal accidents ... very sobering. So far I have thwarted attempts to sue proceeding beyond lodging a defence .. all due to a conservative approach to the way I do business.

Although not of direct relevance to this thread and I have no knowledge of the specifics, the following thread (http://www.pprune.org/dg-p-general-aviation-questions/395569-merged-2003-ypjt-crash-court-case-decision.html) and a related one (http://www.pprune.org/dg-p-general-aviation-questions/384200-jandakot-crash-trial-2.html) hark back to a recent Australian damages case which, I suggest, is of relevance to this thread ..

Consider a hindsight view and turn it into foresight.

Succinct.

[cityfan]

Be a Captain! Assume the authority and accept the responsibility! Judgement is what we get paid for, because we can teach monkeys to flick or depress a switch.

As for the A320 overweight landing procedure being an abnormal, of course it is, but it amounts to a landing vertical speed of no more than 360fpm (if memory serves me), which is no big deal. No special maintenance action needed thereafter. As for the landing distance, not sure what the 737 manual says anymore, but ALL performance factors are based on a set of circumstances, which, in the case of a depressurization, would tend to suggest you have considerably greater landing capability than the conditions listed for the landing calculation.

For those who seem to think landing over MLW is a huge deal, it is done with some frequency in regular line operations all over the world. However, as has been said over and over, with the authority comes the responsibility, so one has to ensure that landing margins and conditions merit not waiting for a lower landing weight. Also, in the example, it appears that one does not NEED to burn all 7,000kgs of fuel, as one is only trying to get down to the "factored" landing weight that creates a legally suitable hard surface. Again, I emphasize that I do not remember the normal landing conditions (braking, reversers, spoilers, anti-skid, etc..), but usually you have one or two of these systems in your back pocket to reduce (sometimes vastly) landing distance. One last thing, if the 737 is like the 320, then MANUAL braking considerably reduces required landing distance over auto brakes, so I would be standing 'em up, if needed! :D

[john_tullamarine]

For those who seem to think landing over MLW is a huge deal, it is done with some frequency in regular line operations all over the world.

If the latter part of the statement be true, then I can only admit to being utterly astounded ...

[rudderrudderrat]

Hi John, I'm speechless that MLW is allegedly being exceeded on a regular basis for commercial reasons.

[FE Hoppy]

For those who seem to think landing over MLW is a huge deal, it is done with some frequency in regular line operations all over the world.

I want to see some statistic to back up this rubbish please.

VERY VERY BAD STATEMENT!!

[Quality Time]

Did he say it was for 'commercial reasons'?

He said it happens regularly and I believe that is true.

I would probably land overweight in the above scenario.

Performance wise it is comfortable and legal.
We are not able to continue the flight due to a technical problem .
We are not landing for 'commercial reasons'.
We would have consulted the QRH.
If the a/c actually depressurised at height you would be on a Mayday or at least a Pan call.

In reality the above landing should be a non-event. Don't thump it in.

As usual expect to have to defend yourself if anything goes amiss!

[DFC]

A few issues which I don't think have been considered jump up here in my mind;

1. Initial problem is described as Depressurisation. Was it a failure to pressurise i.e. climb stopped at or below FL100 or even FL125 and then back to FL100 due to the cabin climbing? or Was the aircraft at FL150+ and the cabin depressurised, oxygen masks deployed? What was the rate of depressurisation?

Basically - can thre be people back there who could have medical issues because of the depressurisation problem?

That would make it a good idea to return sooner rather than later.

2. It appears that it is going to take 2 hours at low level to burn off the fuel to acheive a MLW arrival. Is there no suitable airport within less than 2 hours that the aircraft can land at as soon as it gets there?

3. Can the aircraft comply with the missed approach and balked landing climb gradients at the expected mass?

4. It is night. How long until daytime? What is the weather going to do in the next few hours?

These are issues that I would expect to be part of the decision process.

As for the runway lengths?

If the aircraft returns quickly then the full safety factor is not available. However, the aircraft will not be at TOW when it lands i.e. even an aircraft that takes off at MTOW, catches fire 10Kt above V1 and does a tight visual circuit to land will not land at the take-off weight.

The aircraft completed a safe take-off on the runway. Thus in theory, starting at the piano keys, it could accelerate to V1 and for another 2 seconds and then stop with one engine out without ending up in the mud.

What is V1 in relation to your touchdown speed? and where is it roughly on the runway? I would expect that V1 did not occur at or before the aiming point?

These are some of the factors that have to be considdered.

Having said all that, if the climb was stopped at 5000ft becuase the cabin was climbing with the aircraft and there is no other reason to return plus the fact that we are at an isolated aerodrome, I would be more in favour of waiting for the weight to reduce because anything else is rushing and putting money before safety.

To burn off the fuel, I would prefer flying long straight legs with only drag items that do not cause a lot of noise / bumping. This keeps the pax happier. It may take time - but they expected to be on the flight for a lot more than the 2 hours it is going to take to burn off the fuel low level(if that is not the case then how were you going to land at the destination?). Subject to SOP, they could receive an in-flight service and time taken to liase with pax and company regarding later flights.

Think of it like this -

Dear Pax,

I realise that you are not feeling 100% secure with the situation but there is no immediate danger. Would you prefer to;

1. Return for an overweight landing with possible dangerous over-run then (if ) we make it to the terminal, q at a desk for 1 hour to re-book and then sit on the uncomfortable terminal seats for 3 hours; or

2. Sit here strapped in for 1 hour with the noise and turbulence of the gear and spoilers extended before making a normal landing and q at a desk for 1 hour to re-book and then sit on the uncomfortable terminal seats for 2 hours; or

3. Sit here for 2 hours, have your in-flight service, watch the movie, let us have time to book your replacement flight and when we safely arrive back at the terminal, have 1 hour to collect your bags, check-in and proceed to the gate?

In each case the delay for the pax is the same but 1 has the added posibiity of never getting to the destination!!

In the end it is a Command decision. These are just s few points that I feel must be weighed up. There are no doubt plenty more and the longer one takes to review the options fully, the lower the landing weight!!!!!!!

[FE Hoppy]

The primary Federal Aviation Administration (FAA )
regulations involved in landing overweight and fuel
jettison are:
■ Federal Aviation Regulation (FAR ) 25.1519 —
Requires the maximum landing weight to be an
operating limitation.
■ FAR 91.9 — Requires compliance with
operating limitations.

■ FAR 121.557 and FAR 121.559 — Allow the
pilot in command to deviate from prescribed
procedures as required in an emergency
situation in the interest of safety.

In June 1972,the FAA issued Air Carrier Operations Bulletin
No. 72-11 giving three examples of situations
the FAA considered typical of those under
which pilots may be expected to use their
emergency authority in electing to land
overweight:

■ Any malfunction that would render the
airplane unairworthy.

■ Any condition or combination, thereof,
mechanical or otherwise, in which an
expeditious landing would reduce the
exposure to the potential of additional
problems which would result in a
derogation or compromise of safety.

■ Serious illness of crew or passengers which
would require immediate medical attention.

http://www.boeing.com/commercial/aeromagazine/articles/qtr_3_07/article_03_1.html

In this scenario at best you may argue that avionic cooling may be compromised by prolonged flight but that would be tenuous at best.

You need to look for the least risk and that is not landing overweight in this case.

[Haroon]

-------------------------------------------------------------------------------------------------
To Open Des, RudderRudderRat, Cough, SafetyPee, John Tullamarine and FE Hoppy
-------------------------------------------------------------------------------------------------
Thankyou all for your answers and information.

-------------
To Intruder
-------------
Thankyou for your response. Regarding the extra details you want to know:

- Departure airport is the only option.

- The factored landing distance equals the runway length at Max Landing Weight.

- Why 1.67 % is used? It's a dispatch safety figure for landing and thats what the discussion is all about that, "Can it be used once the A/C is airborne?"

- Unfactored landing distance of 5700 feet which I mentioned in the example is with operational reversers and autobrakes.

So with this extra info do you still hold your answer of Landing and not waiting? Thanx.


---------------------
To CityFan
---------------------

Thankyou for your response. Regarding some extra details regarding the example:

- Getting down to the factored (1.67) landing distance required burning 7000 Kg fuel i.e. to avoid legal implications in addition to safety.

- Brakes, Reversers, Spoilers, Anti-skid, etc all operational. And considering all of these, the factored distance came out to be 5700 feet.

- Full manual braking in high energy stops have caused tire deflations also. So even if you stop safely within the runway filed length avaialble but you are unable to taxi and block the runway and by any chance disemabark your passengers on the runway, then what do you think think about the legal implications?

So with this extra info do you still hold your answer of Landing and not waiting? Thanx.

---------------------
To QualityTimes
---------------------

Thankyou for your response. Just for clarity I mention again:

- After consulting the QRH the unfactored distance is 5700 feet. Performace wise field length is not enough if we apply 1.67 safety factor. However if we dont use 67% safety factor then we are within our field length. So is it OK not to use 67% safety factor once airborne? Will this be legally covered?

- This example is not a Mayday or Pan situation. Soon after takeoff there is complete depressurization and the A/C is under control below 10,000 feet. Everything else is normal.

So with this extra info do you still hold your answer of Landing and not waiting? Thanx.


---------------------
To DFC
---------------------

Thankyou for your response. Regarding some extra details about the example which you need to know:

- Soon after takeoff there is complete depressurization and the A/C is under control below 10,000 feet. Everything else is normal. However your
answer has covered this situation and you said you would rather wait to land.

[Haroon]

So far if I try to summarize the discussion, I think the main issue comes out to be using the 1.67 safety factor for landing i.e. incase of a landback at departure airport above MLW with No Emergency condition requiring to Land ASAP.

The situation is that if you apply the safety factor then your factored distance is more than your field length and if you dont apply the safety factor then your unfactored distance is well within the avaialble field length.

Now the issue is whether one should apply the safety factor after airborne or not? If yes then how much, 1.67 or some other figure?

So far we havent seen anything in Black and White from regulatory authoritues regarding application of 1.67 safety factor after airborne, which seems to be the bone of contention.

However one group thinks that it should be applied and have justified their answers with text of various safety documents which is mentioned above in this thread. This group is conservative in reference to safety and legality.

Other group thinks since there is no Black and White evidence that you have to apply the 1.67 safety factor after airborne, you should save money and land if your unfactored distance is less than the field length.

However at this point of discussion I would like to know, if for some odd reason those who want to land go into an over-run or land on the runway with a flat tyre, then would they be legally covered?

Now I am more interested in finding some definite ruling on using the 1.67 safety factor once airborne, and there is no emergency to land ASAP.

Thanks once again to all of you who are contributing to this issue.

[Quality Time]

Haroon

As has been stated before the 1.67/1.92 factors apply to the planning stage, once you are airborne not so.

IMO you don't have to have an emergency situation to justify landing overweight. Even FO Hoppy undermines his own argument by highlighting the requirement.....

Any malfunction that would render the aircraft unairworthy.A 737 that cannot pressurise is in that condition IMO. OK you could fly it unpressurised but probably to the nearest maintenance base to make it 'airworthy' again.

The Boeing FCTM does not make a big deal out of overweight landings.The first sentence stating........'Overweight landings may be safely accomplished by using normal landing procedures and techniques.'

I note also that the B737 Management reference Guide (Author PBoone)
includes the following guidance on overweight landings.

Recommended

A malfunction that seriously affects the airworthiness of the a/c
A condition whereby a late landing would increase the exposure to a degrading level of safety
One engine inop
A serious illness requiring ammediate medical attentionPermitted

A malfunction not directly affecting the airworthiness of the a/c
An unplanned diversionRemember also that you are receiving input on pprune from all over the world from the USA via Europe to Australia so different authorities apply and different aviation cultures too.

Not making light of the scenario,it's one of those that will split opinions/actions. I have said I would land but on the day I might not do so immediately.Some operations manuals will give clear guidance where others will leave it to the Captain on the day.

Call operations if you can so they get the bo**ocking if it goes pear shaped!

Either way cover your ass and do what you believe to be safe and legal.

[FE Hoppy]

QT.

If i can release under the MEL for unpressurised flight then i am most definitely NOT un-airworthy.

Please note that the advise comes from the FAA via Boeing, it's not something i made up in the pub.

[Quality Time]

FE Hoppy

You can release a four engined a/c for a 3 engine ferry under the MEL too but I wouldn't call the a/c airworthy in the normal sense.

I know you didn't make it up in the pub but there is plenty of official 'advice' in the aviation world that is as about as clear as mud.

[FE Hoppy]

Single engine failure on a four jet is no reason to land overweight. The aircraft is still airworthy.

[Quality Time]

If i can release under the MEL for unpressurised flight then i am most definitely NOT un-airworthy.


You brought up the MEL. That only applies on the ground as you may be aware.

If a crew walked out to a A340 with an engine u/s you would try to convince the skipper it was airworthy ?

Best of luck.

[FE Hoppy]

you are completely missing the point mate.

Of course you cannot accept an engine out before dispatch i didn't imply you could. You have tried to tie two unrelated points together.

There is a thread on here about flying across the pond with an engine out. The flight crew were completely justified as proved by the fact they were not prosecuted on either side of the atlantic for their judgment.


Of course I'm aware of when the MEL is applicable.

What you are not considering is the legal implications in choosing to land overweight when there is no logical reason to do so.

If the risk of remaining airborne out way the risk of overweight landing then land. If not then reduce weight.

Take a look at all the accidents caused by remaining airborne and reducing weight compared to those caused by landing overweight or on reduced landing distance factors.

Landing overruns are a problem. I can think of at least 3 in the last few years.

There are two arguments going on here.
The first is "landing overweight" the second is accepting a reduced required landing distance. This scenario tests both. I don't believe there is reason to accept a reduced landing distance nor do i believe there is reason to land overweight. I certainly don't believe there is justification in doing both.

[Quality Time]

FE Hoppy

I certainly wouldn't have continued all the way to Heathrow( sorry - nearly all the way) but as you have stated my judgement may be flawed.

I agree I would be landing well over the max landing weight but as stated previously the landing distance does not require the 1.67 factoring.

I have in fact considered the legal aspect and have landed overweight myself in both seats in Boeings, real ones.

Yes runway overruns are a problem but they are frequently on very wet runways after a unstable approach or with tailwinds. Risk management is an everyday part of this job and believe it or not other people often get it right.

I disagree with your evaluation.

[safetypee]

Re Boeing data usually doesn’t include the 1000ft+ from threshold to touchdown
Can you cite any objective evidence to support this claim ? (#17)

JT at that stage of the thread it was unclear if the unfactored distance quoted included the airborne distance. My statement was poorly worded and it would have been better to ask a direct question.
I have rechecked a 737 ‘Classic’ QRH and the unfactored landing distance tables do include 1000ft airborne distance.
However, I note that the total distance quoted includes 'detent' reverse and thus is not the same basis as for factored landing distances. The details are in the QRH ‘small-print’.
This suggests that the factored distance quoted (9500ft) could be considerably less than would have been calculated with ‘dispatch’ rules using certificated ‘unfactored’ data (no reverse).

A more practical view of the importance of ‘airborne distance’ in determining the actual landing distance, comes from a FDM / FOQA report (SESMA; 12000 landings, 737-400), which shows an average touchdown point around 1000ft beyond the GS location, i.e. about 1900ft beyond the threshold. The report also showed that the median speed at flare height (30ft) was Vref+7. Thus operators should consider adding at least 1000ft to their estimates of actual landing distance.
This addition is also reflected in the FAA advice in SAFO 06012 “The airborne portion of the actual landing distance (distance from runway threshold to touchdown point) should reflect the operator’s specific operations, operational practices, procedures, training, and experience.

Another point is that if the operator’s procedures require full reverse, yet reverse is not credited in the aircraft’s certificated landing data, then landing risk increases due to the probabilities of incorrect selection and operation of reverse. Here (again), operational rules appear to conflict with aircraft certification rules. The SAFO defines both Unfactored Certificated Landing Distance and Actual Landing Distance, the latter better representing flight operations and not theoretical minimums.
In addition, on a dry runway and when required for non-normal landings, crews should always use max manual braking with full reverse. With autobrake, when the deceleration target is reached the contribution from the brakes is reduced, the commanded deceleration is then maintained by a combination of reverse and reduced braking, which is not max deceleration, thus the landing distance is longer.

[Intruder]

-------------
To Intruder
-------------
Thankyou for your response. Regarding the extra details you want to know:

- Departure airport is the only option.

- The factored landing distance equals the runway length at Max Landing Weight.

- Why 1.67 % is used? It's a dispatch safety figure for landing and thats what the discussion is all about that, "Can it be used once the A/C is airborne?"

- Unfactored landing distance of 5700 feet which I mentioned in the example is with operational reversers and autobrakes.

So with this extra info do you still hold your answer of Landing and not waiting? Thanx.
I do not normally consider Dispatch safety factors once airborne. The exception is fo a planned redispatch, where Dispatch rules still apply.

I have seen 15% and 40% runway length factors usded in various scenarios. This is the first time I have seen 67% used.

If the 5700' landing distance includes air distance to touchdown point and uses normal (not max) autobrakes, I would still consider landing. I would still check the emergency max landing weight for the airport and compare that to the TO (or current) weight. That will give another indication of relative performance limitations.

[Haroon]

---------------------------------------
To QualityTimes and FE Hoppy
---------------------------------------

I thank both of you for your responses. Just to remove some confusion let me say at this point of discussion that heavy weight landing is not an issue. Main issue at this point of discussion is about the landing distance available and required. i.e.

1) Whether one should apply the safety factor after airborne or not? If yes then how much, 67% or some other figure?

2) If 67% safety margin is required at dispatch to reduce the probability of an overrun then what is it that stops us not to adhere to our flight plan if the situation is not to Land ASAP. Is there anything explicit that stops from using the safety factor once airborne?

Even MEL is also a document to be used on ground for dispatch but its application after airborne can be pretty useful as it can help prevent an A/C to get stuck at a place where there is no maintenace.

----------------
To Intruder
----------------

Thankyou for your response. The unfactored 5700 landing distance includes air distance with Auto Brake Level 3. However after applying 67% safety factor AutoBrake 3 is not sufficient and Max Auto setting needs to be used. Max Auto stops the A/C even after applying the 67% factor but enters us into the Caution Zone in which wheel fuse plugs can melt. Since you normally dont use dispatch safety figures once airborne, this data wont affect your decision. Thanks anyways.

--------------------
To Everyone
--------------------

Thanks once again for your valuable contributions. I have my Sim check coming up on the 19th at London so I wont be able to spend much time here for the next one week I think. Take care all of you. See you soon.

[FE Hoppy]

Haroon.

1) Whether one should apply the safety factor after airborne or not? If yes then how much, 67% or some other figure?

Yes. One should ensure adaquate landing distance. The FAA favour a minimum of 15% but it isn't a regulation, just a recomendation. The NTSB has been rather critical of the FAA in not implementing this as a regulation as they believe it would have prevented at least one over run accident. (ERJ170)

There is much guidance around. The flight safety foundation have a good breifing.

Some manufacturers are now including overspeed data as the unfactored figures require Vref over the threashold but if you have used a wind additive you will most likely be above Vref and therefore require more distance.

If you are landing the aircraft at an un familliar weight or on a sloping or wide or narrow runway you will flare differently than normal.

You will flare differently than the test pilots who did the certification campaing because their job is to bring home the numbers not the passengers.

The amount of additive is currently up to you to decide so if you go off the end it's going to be you explaining.



2) If 67% safety margin is required at dispatch to reduce the probability of an overrun then what is it that stops us not to adhere to our flight plan if the situation is not to Land ASAP. Is there anything explicit that stops from using the safety factor once airborne?

It's again not exactly clear. What is clear is that a simple in flight re-planning will still require the 1.67 or 1.92 factor according to the current EU-OPS. Not sure about FAA wording. Any Emergency or abnormal may be justification to reduce landing safety factor due to increased risk in flight but then your q1 comes in to play as to how much to reduce by.

[Checkboard]

What is clear is that a simple in flight re-planning will still require the 1.67 or 1.92 factor according to the current EU-OPS.You, of course, have the reference to that statement to hand? ;) :}

[FE Hoppy]

YES!

OPS 1.475:ok:

[Checkboard]

OPS 1.475
General

(a) An operator shall ensure that the mass of the aeroplane:

(1) at the start of the take-off; or, in the event of in-flight replanning

(2) at the point from which the revised operational flight plan applies, is not greater than the mass at which the requirements of the appropriate subpart can be complied with for the flight to be undertaken, allowing for expected reductions in mass as the flight proceeds, and for such fuel jettisoning as is provided for in the particular requirement.

(b) An operator shall ensure that the approved performance data contained in the aeroplane flight manual is used to determine compliance with the requirements of the appropriate subpart, supplemented as necessary with other data acceptable to the Authority as prescribed in the relevant subpart. When applying the factors prescribed in the appropriate subpart, account may be taken of any operational factors already incorporated in the aeroplane flight manual performance data to avoid double application of factors. ...


OPS 1.515
Landing — dry runways

(a) An operator shall ensure that the landing mass of the aeroplane determined in accordance with OPS 1.475(a) for the estimated time of landing at the destination aerodrome and at any alternate aerodrome allows a full stop landing from 50 ft above the threshold:
(1) for turbo-jet powered aeroplanes, within 60 % of the landing distance available; or
(2) for turbo-propeller powered aeroplanes, within 70 % of the landing distance available; ...

OPS 1.520
Landing — wet and contaminated runways

(a) An operator shall ensure that when the appropriate weather reports or forecasts, or a combination thereof, indicate that the runway at the estimated time of arrival may be wet, the landing distance available is at least 115 % of the required landing distance, determined in accordance with OPS 1.515. ...

OK, That does seem fairly clear :ok:

[FE Hoppy]

No worries mate.

[Haroon]

Thankyou FE Hoppy and CheckBoard for the refrences and the document's text. If I have understood correctly according to the document OPS 1.475 and 1.515, 40% safety margin is required for turbo jets. ( i.e. within 60 % of the landing distance available)

According to this document, this factor (i.e. 40% for turbo jets) also applies at the start of takeoff in addition to inflight re-planning. (If I have understood correctly).

So where does the 67% dispatch safety factor go according to these documents? Is 67% only a Boeing figure? :confused:

[FE Hoppy]

Haroon,

It's just a bit of maths.

You need to land in 60% of the available distance. That means you must have 1/60x100 of your actual landing distance available. That's the same as 1.66 recurring so 1.67 is used.

For a wet runway we must have 115% of the dry figure so we could do two calculations or we could simply calculate 1.92 X actual landing distance.

For a test pilot actual landing distance = unfactored landing distance. And in many companies this is what is used for line operations.

It could be argued that as we know the average line pilot is not likely to meet the test pilots results we should use more to fully comply with the spirit of the law but you wont find many(any!) operations that include a line pilot factor.

[Intruder]

Inverting the safety factor numbers may be "just a bit of maths," but it serves to confuse more than anything else. In these forums, using the numbers actually cited in the various regulations would be a much better idea...

[Checkboard]

Problem with the various regulations is they are not consistent themselves. Aviation is a profession with a few numbers - a bit of simple maths shouldn't be beyond anyone here! :hmm:

[Intruder]

Yes, but a simple cite, such as "adapting/inverting the rule from OPS 1.515..." would serve to clarify.

[safetypee]

Aviation safety requires avoidance of unnecessary risk; risk depends on the hazard, frequency of encounter (likelihood), and the severity of the consequences. The process (risk assessment) requires judgment, which in turn requires dependable knowledge and appropriate skills of thought.

A safety factor provides a buffer between the hazard and the planned operation. It is a margin for ‘error’ or deviation from the ideal to minimize the risk(s) and/or alleviate consequences of the hazard.
Haroon discusses ’ the ‘ safety factor (#34), but the issue is ’ a ‘ safety factor, relating to a specific situation and the assumptions made about human behavior/capability (in that situation). Hence, in an emergency (change of situation), the landing-distance safety-factor can be reduced. Note that although a wet landing uses a landing–distance factor of 1.92 it is not necessarily the same safety factor as for a dry runway as the increasing number of the accidents indicates.
Thus, the debate is firstly whether the event is an emergency or not – it’s not; and secondly if an over weight landing were to be attempted what distance is required to provide a margin of safety equivalent to a max wt landing on a dry runway.

EU-OPS 1.475 requires a 1.67 factor (normal operation – in flight replanning).
The QRH actual landing distance (5700ft) is probably shorter than the certificated actual landing distance because reverse detent is used (I assume that this is idle, vice ‘max reverse’ quoted elsewhere in the QRH).
Thus by adding 220ft (QRH adjustment for no reverse), the certificated actual (overweight) distance is ~ 6000ft.
A 1.67 factor would require ~ 10,000ft runway.
However, this calculation does not consider other / new risks such as brake energy limit, brake fade, landing gear limits (vertical rate and side loads).
As all risk assessments should be specific to the situation, the calculations for the overweight landing above does not use an equivalent basis as a for max wt landing, and it is these differences which might sway the argument for not landing overweight without an emergency as the aircraft is not certificated for this on a regular basis.

Re The flight safety foundation have a good briefing. (F E Hoppy), is this the one? http://www.skybrary.aero/bookshelf/books/874.ppt

A recent FSF report outlines the nature of the risks, but provides few practical remedies - http://www.skybrary.aero/bookshelf/books/900.pdf
A similar but more practical document is ‘Runway excursions’ (www.atsb.gov.au/publications/2009/ar2008018_1.aspx)by ASTB.
For some ‘How To’ aspects – Judgement etc see Aviation.org (http://aviation.org), - ‘library’ section, presentations on Critical Thinking, Situation Awareness, and Decision Making (free registration required).

[FE Hoppy]

Safetypee,

I was refering to this:
Approach and Landing Accident Reduction (ALAR) | Flight Safety Foundation (http://www.flightsafety.org/current-safety-initiatives/approach-and-landing-accident-reduction-alar)

Well worth reading through the whole thing for those with a little time to spare. Section 8 is most pertinent to this discussion.

[Haroon]

Hello again. Sorry for the late response as I got stuck in a busy pattern after the sim.

FE Hoppy thanx for the reference I was looking for. Perhaps I did'nt pay proper attention to the terminologies used i.e "Margin" and "Factor" in my last post.

If I have understood correctly now then to land within 60% of the landing distance available means 40% of the landing distance available will be there for us as a safety margin.

i.e. If landing distance avaialble is 10,000 feet then aircraft has to stop
within 6000 feet so that the remaining 4000 feet is avaialable as a
safety margin. The remaining 4000 feet is 40% safety margin in
reference to landing distance available and 67% safety margin in
reference to landing distance in which the aircraft stops.

Thus in reference to the aircraft actual landing performance

Margin of Safety = 67%

Safety Factor = 1.67

Whereas in reference to landing distance avaialble the margin of safety = 40%

Thankyou all :ok:

[sudden Winds]

if pax are calm, and no one is hurt, i would hold and land within max landing wt, course I'd check wx, talk to the company and everything, but I wouldn´t land a 737 or a 320 with 7 tons overwt, at night, out of a non precision approach, JUST to save fuel. Again if there´s one good reason to land overwt, eg a pax not feeling well, weather deteriorating really bad, I´d think about terminating the flight, otherwise I´d burn off fuel.

[ITCZ]

A very interesting thread, and a worthy Techlog discussion :D

I cannot add much more in the way of wisdom, but perhaps can help simplify it or provide a 'take-away' point.

1. Decision maker's rule of thumb for attempting an Overweight (over MLW) landing:

"Is the hazard of continued flight, greater than the hazards of an overweight landing?"

The hazards of the overweight landing having been identified by FE Hoppy, JT and others. Especially the exponential increase in energy that must be absorbed by the gear and airframe on touchdown (Vg Max) and then dissipated via braking systems. Also, beware the temptation to overestimate one's capabilities to 'handle' an abnormal situation.

If you can't dump the fuel, and nobody is likely to die or be injured by your holding 1hr or 2 hrs -- hold.

2. "Make fuel on the easy days. Not the tough days."

If your airline is like our airline, the focus on reducing carriage of 'discretionary' fuel and routinely uplifting Minimum Operational Requirement across the network, every day, will have more than offset your burning 4 (or 20) tonnes the one day you may be called to do that.

3. Overweight landings are different from 'not full factors' landings.

You may also be faced with the situation where you are at or below structural MLW, but forced to consider putting your aeroplane into a field that does not meet the 'full factors' 1.67 (dry) or 1.92 (wet).

In that case, you have eliminated one unknown - you will have landed your aircraft at that weight many times before. You are in familiar territory, handling-wise.

But halving the factor, is quartering the margin for error.

If, after considering the italicised advice, you need to put your aircraft onto a runway that has less than full factors, you have a situation that your cabin crew, your pax, and the airfield services ought to be briefed in on. The subsequent landing will not be pretty, braking may be forceful, and any handling error on your part might have you off the fairway and in the rough. Literally.

My 2c worth.

Great discussion. :D

[Pitch Up Authority]

Dear all

An overweight landing assumes there is no time for dumping or dumping is not possible.

There is no regulation that requires factoring.

As a guideline: runway, climb and obstacles limitations need to de taken into account.

Overweight combines adversely with any system failures that affect deceleration and/or controlability.

Piece of cake.

[ITCZ]

There is no regulation that requires factoring.
True for you perhaps, but lack of regulation does not mean, do what you like.

Would you fly with 0% variable and 0 minutes fixed fuel reserves, if there were no regulation? What would guide you in your decision on fuel reserve, if there were no regulation?

We still have a duty of care. We all know that we are not all test pilots flying in controlled test conditions. We know that, and the court of inquiry will know that too.

How do you assess it, if not by reference to factors implied by regulations as being a suitable standard?

Do you use another method? One that can stand scrutiny?

I ask out of curiosity, not rhetorically - factors are treated as in-flight requirements as well as pre-departure requirement over here.

[Pitch Up Authority]

Its up to the sound judgement of the captan.

And yes I do have some good guidelines that have been found sound by various chief pilots of mayor flag carriers.

Ask Emirates Airlines it they can stand up that challenge.

[ITCZ]

Ask Emirates? They are not here. You are.

Why the reluctance to share?

[Pitch Up Authority]

You want the knowhow, you pay for it...... ask your chief pilot, he gets paid for it I hope.

[ITCZ]

49 yo and still has not learned to play well with others.... :bored:

Mod - no worthwhile contributions here from the probationer... shall we tidy up those last few posts?

[Pitch Up Authority]

ITCZ: Its not a game.

You will find out the day you ever have to take a serious decision. My post regarding overweight landing is correct and reflects the current state of rules and regulations.

Any margin that a company wants to build in is at their own discretion and policy.

You referred in your post to a possible court investigation if something would ever go wrong, I thank you for that remark. I hope you are able to asses that implication wisely and pass it on to whoever you fly with.

I took the decision to share the extend my experience with whom I like and there is nothing wrong with that.

By the way I even have a method that makes your decision completely independent of braking action and malfunctions in the brake system but not for you.

ITCZ: Thank you for the PM. If you claim to have 24000 hrs and be a Chief Pilot it should be easy for you to put in cristal clear language your vieuws and policies regarding overweight landings. I hope I can learn something from it but at a certain moment the learning stops and the teaching starts

[Haroon]

Thankyou SuddenWinds, ITCZ and Pitch Up Authority for your posts.

Pitch Up Authority:

You mentioned that,

Any margin that a company wants to build in is at their own discretion and policyBut the company minima cannot be below the regulatory minima, please correct me if I am wrong.

Secondly you mentioned that,

There is no regulation that requires factoringBut as pointed out by FE Hoppy earlier in this discussion JAR OPS 1.475 and 1.515 states the regulation which requires this factoring for in flight re-planning (if there is no emergency).

Though I am not a test pilot but I am optimistic that I would be able to land within the landing distance available in conditions which are mentioned in this post. I believe even those who say they wont land in these conditions are able to do so.

But we are not optimistic about the fact that absolutely nothing can go wrong. It is very much possible to enter the Caution Zone after landing (if nothing else goes wrong) and if a tire deflates and one is unable to vacate the runway then is there something that will protect us from the legal side :ugh: especially when the regulation does not allow us to land unfactored.

Things can go wrong even after full compliance with the regulations but at least we are legally covered. So basically at this point of discussion we are trying to focus more on the legal side because we need protection on that end apart from passenger and flight safety.

[Pitch Up Authority]

One of the shortcommings in ATPL courses is that there is not enough atttention for the background and reasoning behind certain rules, regulations and limitations. (ex Crosswind limitations, validity of friction coeficients etc....)

It looks like these gaps are sometimes covered by operator trainig programs and manufacturers efforts to inform pilots more than they have done in the past. Technical commisions within pilot unions try to do the same but these organisations have often very limited resources.

Individuals that were and are member of ICAO and JAA performance comities have addressed certain topics but have also highlighted some of the shortcomings of the regulatory proces.

There are a few things we can do but this is not the place.

In the end its about our own safety, nobody can ever accuse you of putting the safety of your pax at danger except a corrupt system.

[Haroon]

One of the shortcommings in ATPL courses is that there is not enough atttention for the background and reasoning behind certain rules, regulations and limitations.Its good to know the background but once a regulation is made it has to be followed regardless of the reasoning behind it. I mean if a policeman catches me on crossing a red light, I cant argue that I should not be punished on the basis that I didn't bang into any other car, as collision avoidance was the main reason of traffic lights at a crossing.


Individuals that were and are member of ICAO and JAA performance comities have addressed certain topics but have also highlighted some of the shortcomings of the regulatory proces.There are shortcomings because regulations are made by humans and one cannot rule out human factors/limitaions. But to challenge a regulation one has to submit evidence against it to the concerned committee so that a revision is issued. Until the new regulation is issued the previous one remains valid in the court of law.

In the end its about our own safety, nobody can ever accuse you of putting the safety of your pax at danger except a corrupt system.Legal Implications + Corrupt System = Nightmare :{

[Pitch Up Authority]

Its good to know the background but once a regulation is made it has to be followed regardless of the reasoning behind it. I mean if a policeman catches me on crossing a red light, I cant argue that I should not be punished on the basis that I didn't bang into any other car, as collision avoidance was the main reason of traffic lights at a crossing.

What if the car has a technical problem?

There are shortcomings because regulations are made by humans and one cannot rule out human factors/limitaions. But to challenge a regulation one has to submit evidence against it to the concerned committee so that a revision is issued. Until the new regulation is issued the previous one remains valid in the court of law.

Not all situations are covered by regulation.


Legal Implications + Corrupt System = Nightmare

I agree

During normal operations I used to (were possible) decelerate with reversers only. After a while you get a fairly accurate idea what lenght you need as function of touch down ground speed. This method makes you independent of brake system problems and breaking action. The only problem is the reliability of the reversers as function of system reliability and the combination of braking action/ crosswind.

It puts the advisory data for slippery runways in another context. These data are subject to fierce discussions at all levels. Directional control problems as a consequence of uneven braking being one of them.

Basicaly you can always land on the runway to took off from if it is dry. Max brake energy may be a limitation.

If it is not dry you better look carefully at groundspeed on touchdown and slope when you choose your RWY. This becomes more important on slippery runways. Those who live in the northern part of our globe know all about this.

[Mansfield]

To all,

I thought I would add a couple of points which I have not seen in the preceding discussion (forgive me if I have overlooked them).

The point has been established that the factoring of the actual landing distance is a dispatch requirement, i.e., a 6000 foot actual landing distance requires a 10000 foot runway under dry conditions. Further we have established that under wet conditions, an additional fifteen percent mist be added, thus requiring 11500 feet.

We have discussed whether this remains a requirement after dispatch. The conventional wisdom is no, it is not a requirement following dispatch. It is a planning requirement only.

In the US, a lesser known requirement resides in Operations Specification C054. This addresses the lower-than-standard minimums case (standard meaning RVR 4000 or 3/4 mile). The relevant text is:

(2) A pilot-in-command of a turbojet airplane shall not begin an instrument approach procedure when the visibility conditions are reported to be less than ¾ statute mile or RVR 4000, unless the following
conditions exist:

(a) Fifteen percent additional runway length is available over the landing field length specified for the destination airport by the appropriate Sections of the CFR.

Note that this is an operational, inflight requirement. The PIC shall not begin an instrument approach, etc. It turns out that the "appropriate" section of the CFR is 121.195(b), making this requirement identical to that in 121.195(d), which is the 115% requirement. So the requirement is the same, but the threshold criteria and the point in the flight where it is invoked are different.

This would seem to suggest that there is an argument to made supporting the use of the dispatch landing distance requirements while in flight.

I was curious to see whether the JARs contained a similar requirement. Perusing through JAR-OPS Part 1, I could not see any such requirement...which, given my lack of familiarity with JAR, isn't saying much. However, I did note the following requirements regarding landing distance in JAR-OPS 1, Subpart G, Paragraph 1.515:

(d) If an operator is unable to comply with subparagraph
(c)(1) above for a destination aerodrome
having a single runway where a landing depends
upon a specified wind component, an aeroplane may
be despatched if 2 alternate aerodromes are
designated which permit full compliance with subparagraphs
(a), (b) and (c). Before commencing an
approach to land at the destination aerodrome the
commander must satisfy himself that a landing can
be made in full compliance with JAR–OPS 1.510
and sub-paragraphs (a) and (b) above.

Again the language requires the PIC to make an assessment, before commencing the approach, that the dispatch requirement can be met.

These seem to be two instances which are not consistent with the interpretation that the dispatch requirement goes away after takeoff. Neither directly apply to Haroon's initial scenario, but these things have a way of laying the foundation for the arguments during the hearing. All of which leads us back to John Tullamarine's point that you really need to justify non-compliance with the landing weight by declaring an emergency. Thus, you need justification beyond commercial purposes.

That said, I'll add my two cents regarding the real thing. Based on my very nearly disastrous experience with an overweight 767-300 returning to the departure field, I can state that non-precision approaches at night are probably not the best time to abandon the factoring criteria. Although we had the factored distance for our weight, the maneuvering required after breaking out at five hundred feet and 170 knot Vref put us well past the touchdown zone at an radio altitude of zero (based on the DFDR later reviewed). This necessitated a go-around, which was followed by an immediate failure of the flight directors, which was then followed by a 2000 foot ATC-instructed level off, which directly led to a flap overspeed. Having gotten that sorted out, the ensuing landing, in the touchdown zone this time, led to three of eight main tires failing.

All three of us (I was the non-flying FO) made a remarkably complimentary series of errors that night, which very nearly used up all of the margin that we had. Overweight landings need not be disasters...I've made others that were far less dramatic...but they open the door up to margin-absorbing non-routine irregularities. Although you can and should plan thoroughly and comprehensively, you retain the margins whenever possible because you will never, ever, see the one coming that gets you.

[Pitch Up Authority]

I agree, dispatch requirements apply when airborne under JAR.

Nice example of where ATPL courses and training should focus on.

Given the same rwy lenght I would take the side with an upslope even if it is a NON Precision app, check the numbers in the AFM.

As a commander you need to be able to put the acft on the right spot.

There is no need to use max brakes but brake as function of runway lenght.

This is what EK did wrong in Johannesburg.

All this is written down in the FCTM, no secrets.

[safetypee]

Mansfield, #61, some interesting items.
For info; JAR is now EU-OPS, but the text is essentially the same.
EU-OPS and FAR 121 are slowly being harmonized; the landing requirements are essentially identical and originate from the same certification requirements CS 25.125 / FAR 25.125. The only significant difference is in contaminated operations where EU-OPS 1.520 requires accountability but FARs do not. However, FAA SAFO 06012 does refer to the difference.
CS 25.1591 ‘Contaminated Runway Certification’ is well worth reading as it provides most of the definitions and assumptions for the operation; one significant point is for operators to determine whether reverse is credited or not.

Pitch Up Authority, re the choice of runway direction, perhaps the head/tailwind – groundspeed might be the dominant consideration. After all it is energy (speed squared), which has to be dissipated within the runway length.

Re There is no need to use max brakes but brake as function of runway length.
Perhaps this is a bold generalisation as it assumes that pilots know what the limiting landing distance is and thus the additional safety margin available from a longer runway.
Unless an operator’s landing performance covers a range of runway distances (usually only the distance of the chosen runway), the crew will only know if they meet the landing requirements or not - yes / no choice.
Landing data is provided for weight (landing mass). A better guide as to how hard to brake can be obtained by comparing the max allowable landing weight (on a given runway) with the actual landing weight, but this too might not consider additional margins on very long runways.
Weight comparison provides some guidance as to the safety margin available, but this still requires experience, and consideration of runway conditions and other variables before choosing a level of braking. Some data (and aircraft systems) provide some of this information, but all, as do humans, have limits of not knowing the precise nature of the conditions, thus rules of thumb such as initially brake harder than you judge might apply.

From your post #60, the reliance on reverse might be foolhardy (cf Midway accident). Normal landing performance rarely credits reverse thrust for good reason. Being ‘independent of the braking system’ is a risky mindset, particularly on slippery runways after cancelling reverse.

Similarly, you may have generalised the phrase ‘the advisory data for slippery runways’, but in EU-land the data required is much more than advisory; see above EU-OPS 1.520, CS 25.1591.

[Pitch Up Authority]

Safetypee: I agree with your statements and I do not see where I stated anything in contradiction.

I you land on a 3000 m runway with a 737 using rev only you take no risk at all. At 120 kts you need 1600 m and at 140 kts about 2000 m to get the speed down to 80 Kts. Nice to know that you have some brakes on top of that if they perform as predicted. Crosswind and directional control are crucial as you may have to stow the rev but all that is part of your assessment.

JAR OPS as opposed to FAR did go one step further by requesting data for slippery rwy with a 15% factor. The problem is the reliability of the friction measurement. See briefing from Boeing on that subject.

I made myself a table based on the AFM with landing data for various overweight conditions including Vmbe limitations. If you look at them on a regular basis you develop a good feeling what is possible.

Groundspeed is a key factor as I had stated before. If rwy is slippery, slope becomes significant.

When driving a car you know how to decelerate as stop before a traffic light. With an aeroplane it just takes a while to get the same feeling but it takes some effort. You need to take some time after each landing to reflect a bit on what happened. After a while it becomes second nature.

A useful exercise on a very long runway is also: Idle rev and no braking and see how she decelerates by herself, you will be surprised.

[Haroon]

Thankyou all for your inputs

According to " JAR / EU-OPS 1.475 ", 1.67 factor for dry runways remains valid for inflight replanning.

Is there a FAR reference like this?

[Quality Time]

Returning for an overweight landing is not 'inflight replanning' as I understand it. That is a defined procedure usually for medium/long haul flights to re-plan a destination if you are struggling for fuel at the initial planning stage.

In any event in my very large EU Ops airline the requirement is not the same once airborne.