LDR versus actual landing distance

[TCASfail]

The LDR is the actual landing distance x 1,67 for dry RWY and actual landing distance x 1,92 for wet RWY unless dry would be the greater number.

My understanding of EU OPS is as follow: those rules are to be met in the planning phase of the flight or for an inflight replanning (change destination).

Inflight when preparing the landing we have to look for the actual landing distance. In this phase of the flight we have to consider a lot of things we can´t consider in the planning phase prior the flight. For exampel the actual landing weight of the aircraft (may be higher than planned because of less fuel burned etc.). The now calculated actual landing distance (AFM - no factor) has to be within in the factored LDR as above.

The result is that the margin could now be less than within the planning phase. It could be zero (not good). The actual landing distance could be greater than the LDR as well (no landing allowed).

Am I right?

[eckhard]

My understanding is that for the PLANNING phase, we ensure the runway will be long enough as you describe.

In-flight, if we are landing at the planned destination or alternate with no defects suffered since departure, the safety margins will be adequate to allow for any small difference in planned and actual landing weight.

If we make an unplanned diversion or suffer a defect that affects landing performance we are in an UNPLANNED scenario and therefore the planning criteria no longer apply. We would naturally look for the longest suitable runway and make every effort to land with the greatest possible safety margin.

The Non-normal checklist or QRH should give guidance on factors to apply to the actual unfactored landing performance published in the AFM. Some operators advise adding a further 50% to this adjusted distance to allow for 'operational variables'.

In the 'subsequent Court of Enquiry' you should be able to show that you took all reasonable steps to ensure the safe outcome of this unplanned event.

If all goes well, no problem. If not.........
Hopefully, your lawyer will be better than theirs!

[Denti]

There doesn't seem too much regulatory guidance for the inflight phase. At the outfit where i have to work now we allways have to at least use the planning performance data for the revised expected landing weight and actual runway conditions. Even for diversions or non normals except when the non normal data requires even more landing distance.

That way we allways have to check the planned landing distance table for every landing inflight and the minimum factor is the same inflight as during planning.

[eckhard]

On the face of it, Denti's company procedures would seem to add an extra margin of safety.

However, If you had a serious problem in-flight and the nearest suitable runway was wet and only offered your actual LDR x 1.85 (instead of 1.92), would you fly for an extra hour to get to a runway that offered the full 1.92? Would you dump fuel or hold in the vicinity of the shorter runway until your actual LDR reduced to the LDA x 1.92?

It must be possible for the crew to weigh up the balance of risk between:

1. Extending the flight time with a serious emergency; and
2. Accepting a slightly reduced 'landing distance available' and landing immediately.

That is what airmanship and command is all about. (Think of Swissair MD-11 at Halifax)

What you need to know in these circumstances is the actual unfactored LDR for the conditions. Then you can make a judgement whether or not the actual LDA is sufficient, given the nature of your problem.

[Capt Claret]

My operational experience is limited to Australia. Here, the 1.67/1.92 are required for normal operations. The relevant CAO (Civil Aviation Order) 20.7.1B (for larger aircraft) requires the LDR be equal or less than the LDA given the actual landing weight (and other pertinent factors). For an emergency situation, then, one does the best one can.

I'd be very surprised if this thinking doesn't apply world wide.

[Gulfstreamaviator]

on the day you can "plan" to include the actual wind.

for planning purposes no wind.

glf

[safetypee]

TCAS fail, note that the factors quoted are for jets, turbo props differ.

Your interpretation is generally correct except that in-flight re-planning could be interpreted as requiring the same aspects at the destination.

EU-OPS 1.400 requires the Captain to satisfy himself … that the condition of the runway intended to be used should not prevent a safe approach, landing … in the pre-landing assessment. From a safety perspective (consider how regulators define and use safety), it might be difficult to justify landing with any lesser factor than required for dispatch. The dispatch calculations are ‘safe’, thus, any lower factor might be construed as less safe.
Normally the industry requires the highest level of safety, except where different levels can be justified by risk assessment such as in an emergency.

An interpretation or guidance might be in UK AIC 14/06. (www.nats-uk.ead-it.com/aip/current/aic/EG_Circ_2006_P_014_en.pdf)

Also see AIC 86/07. (www.nats-uk.ead-it.com/aip/current/aic/EG_Circ_2007_P_086_en.pdf) and http://www.skybrary.aero/bookshelf/books/874.ppt

[Flexi]

Hey TCASfail,

short post for clarification:

first of all, it is IMPOSSIBLE that under given conditions the required landing distance on a dry RWY is LONGER than for a wet RWY!

This is because of the additional safety margin of 15% on a wet RWY compared to a dry RWY!

The required landing distance is derived/calculated from several flown approaches from testpilots (50ft passing Threshold, Vref, TD at 1000' etc).
This idealistic (and unrealistic) ACTUAL Landing Distance is multiplied by 1,67 to get the REQUIRED Landing Distance DRY RWY!

If you mulitply this lengths by 15%, you get the REQUIRED Landing Distance WET RWY, which therefore equals to ACTUAL Landing Distance X 1,92!
Nice to know, that in general the landing performance on a wet RWY requires more than the 15% safety margin, therefore the ACTUAL safety margin reduces compard to DRY conditions!

Landing on a contaminated RWY:

The REQUIRED Landing Distance on a Contaminated RWY is the longer of the

-REQUIRED Landing Distance WET RWY or

-ACTUAL Landing Distance CONTAMINATED RWY x 1,15

If the second one is the limiting, your safety margin reduces to 15% compared to the ACTUAL Landing Distance. By the way, the data for actual landing distance on cont. RWY may be based on calculations - it has never been demonstrated on a real aircraft under these conditions!

Under normal conditions (no emergency) the Landing Distance Available MUST NOT be less than the REQUIRED Landing Distance! This is valid for planning as well as for the actual landing. It must be assured at all landings that legal requirements are met and Landing Distance Available is sufficient for your conditions!

Things are different in an emergency situation! For the 737 for example, the QRD gives you information for the ACTUAL Landing distance for different malfunctions (One Engine Out, Flapless Landings or Dual Hydraulic Failure etc.). Corrective values are given for different pressure altitude or wet RWYs. But you should keep in mind that these are again ACTUAL Distances. If this distance is equal to the Landing Distance Available, you have NO safety margin at all!

Cheers

Flexi

[Denti]

@eckhard, the 737 we do fly cannot really, and does not neet to dump fuel for landing, and of course the captain allways has the final authority. Fire on board is a special case and requires immediate landing where any kind of landing, including off airport or ditching, has to be considered. During simulator training taking more than 15 minutes to land with a fire still burning will automaticly fail you and require retraining in an additional simulator session. I do not know if our airbus fleets have to follow the same rule, however on the 737 we have to use full factors except if an immediate landing is required.

When operating under non normal conditions we have to check a factored non normal configuration landing distance (20% factor) against full factored normal configuration landing distance and use the higher value. The captain can decide to not follow that rule of course, but has to defend his decision later on if he is still able to do so.

[Checkboard]

Things are a little different now, under EU-OPS, than they were under JAR-OPS.
EU-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. ... [My Bold]