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TOPCAT Landing Distance (Actual)

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Can someone explain what this means? I read on the manual its unfactored but what though? It also changes if you select braking mode AUTO MAX

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But why in TOPCAT if you select other than AUTOBRAKE 1 to 3 and select MAX AUTO and MAX manual you get unfactored then?

 

Also for TOPCAT dispatch it calculates LDR etc where does this information come from? Because i only see in my FCOM DP - FLLW and LCLW.

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It always calculates unfactored landing distance according to the manual.

 

As for the other question if you posted in plain English and not abbreviations it would be easier to understand what you meant.

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But what is the unfactored? It can't be the dry safety margin of the 1.67 rule and the brakes

 

FLLW field length limit weight

LCLW landing climb limit weight

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EASA ops

 

CAT.POL.A.230 Landing — dry runways

 

(a) The landing mass of the aeroplane ... shall allow a full stop landing from 50 ft above the threshold:

(1) for turbo-jet powered aeroplanes, within 60 % of the landing distance available (LDA);

 

1/1.67 = 60 % LDA. So it seems TOPCAT isn't applying this safety margin rule

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1/1.67 = 60 % LDA. So it seems TOPCAT isn't applying this safety margin rule

 

Without looking at the documentation, I'm fairly sure it does in DISPATCH mode -- hence why some of the options are greyed out.

 

When you go to IN FLIGHT mode, you then get the "actual" stopping distances based on the autobrake selection etc (which, for instance, allows you to plan which turnoff to aim for etc).

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Without looking at the documentation, I'm fairly sure it does in DISPATCH mode -- hence why some of the options are greyed out.

 

For Landing distance required - YES, but for the Landing distance actual or ALD - NO. So that answers that.

 

From the manual -

 

Dispatch (Pre‐flight): Actual, un‐factored landing distance (from 50 feet above runway to a complete stop) including malfunctions (if any) with maximum braking and no approach speed increase factored with 1.67 (jet aircraft) or 1.43 (propeller aircraft).

 

What is the un-factored?

 

Also is TOPCAT working of JAA or FAA, i think FAA because FAA QRH distances i believe are unfactored and JAA are like my QRH.

 

 

Just to add.

 

I think its pretty useless TOPCAT dispatch, if you work under EASA/JAA because the requirement for dispatch isn't runway length - but LFLW (Landing field limit weight)

 

As a Dispatch requirement, LFLW is the lowest of the LFLW determined for;

- the most favourable runway without wind, and

- the expected landing runway with wind.

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But what is the unfactored? It can't be the dry safety margin of the 1.67 rule and the brakes

You keep asking what is unfactored. Clearly this is the calculated stopping distance without any safety factors applied. In other words the actual stopping distance.

 

The TOPCAT manual goes into detail in the section called Calculation Method and describes the factors to be applied to calculate Landing Distance Required. Basically 1.67 for a jet aircraft and an additional 1.15 for wet or contaminated runways.

 

It's a bit much to expect TOPCAT to provide data on the EASA weight limit method for dispatch. Remember this is a hobby sim utility, it isn't a certified training tool.

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You keep asking what is unfactored. Clearly this is the calculated stopping distance without any safety factors applied. In other words the actual stopping distance.

 

What safety factors will that be?

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The dispatch requirement (1.67) plus any additional factors required for inoperative items.

 

 

 


I think its pretty useless TOPCAT dispatch, if you work under EASA/JAA because the requirement for dispatch isn't runway length - but LFLW (Landing field limit weight)

 

But the two are the same thing expressed in different units.

 

The requirement is to be able to stop within 60% of the LDA. Obviously this will (in terms of the variables the pilot can control) be dependent on the landing weight. If at the planning stage you cannot stop within 60% of the LDA (as calculated by TOPCAT) then you must reduce the weight of the aircraft until you can (i.e. chuck off some pax/bags etc).

 

In any case, TOPCAT does give you the maximum permissible landing weight: immediately above the panel where the computations appear, you should see Perf Limit Weight (Dispatch).

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The dispatch requirement (1.67) plus any additional factors required for inoperative items.

 

Well TOPCAT mentions - Dispatch (Pre‐flight): Actual, un‐factored landing distance (from 50 feet above runway to a complete stop) including malfunctions (if any) with maximum braking and no approach speed increase factored with 1.67 (jet aircraft) or 1.43 (propeller aircraft).

 

So its unfactored then factored by 1.67 contradicting itself?

 

The requirement is to be able to stop within 60% of the LDA. Obviously this will (in terms of the variables the pilot can control) be dependent on the landing weight. If at the planning stage you cannot stop within 60% of the LDA (as calculated by TOPCAT) then you must reduce the weight of the aircraft until you can (i.e. chuck off some pax/bags etc).

 

That is a requirement, not from Boeing's performance recommendations, but the Authority's legal requirements.

 

Just to add..

 

LANDING MASS

CAT.POL.A.230 establishes two considerations in determining the maximum permissible landing mass at the destination and alternate aerodromes:

(a) Firstly, the aeroplane mass will be such that on arrival the aeroplane can be landed within 60 % or 70 % (as applicable) of the landing distance available (LDA) on the most favourable (normally the longest) runway in still air. Regardless of the wind conditions, the maximum landing mass for an aerodrome/aeroplane con guration at a particular aerodrome cannot be exceeded.

B. Secondly, consideration should be given to anticipated conditions and circumstances. The expected wind, or ATC and noise abatement procedures, may indicate the use of a di erent runway. These factors may result in a lower landing mass than that permitted under (a), in which case dispatch should be based on this lesser mass.

B. The expected wind referred to in B. is the wind expected to exist at the time of arrival.

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If at the planning stage you cannot stop within 60% of the LDA (as calculated by TOPCAT)

 

Sorry but TOPCAT doesn't calculate 60% of LDA or / 1.67

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Sorry but TOPCAT doesn't calculate 60% of LDA or / 1.67

 

In Dispatch mode, it calculates your actual landing distance, then multiplies this by 1.67 to give the landing distance required including the safety factor.

 

It then verifies whether LDA <= LDR and if not will return lots of red.

 

It also determines the maximum weight at which LDA = LDR.

 

topcat_lr_zpsb44nrg24.png

Actual landing distance (unfactored) = 1207m 

1207 x 1.67 (actually 1.666) = 2011m, which is the landing distance required. In this case, it is equal to the landing distance available.

 

The maximum landing weight (267,860kg) is indicated above (verified by the fact that the landing weight entered is 267,860kg, giving a result of LDA = LDR).

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Ah good one simon great job. But you wouldn't be able to dispatch surely because your LDA is more than 60%

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Ah good one simon great job. But you wouldn't be able to dispatch surely because your LDA is more than 60%

???

 

Actual landing distance = 1207m

 

Landing distance available = 2011m

 

1207/2011 x 100 = 60% (actually 60.01%, but bear in mind we are rounding the nearest metre, which TOPCAT probably isn't internally).

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But the actual landing distance is the unfactored distance without the 1.67 safety margin for dry runways;

 

Dispatch requirement is 1.67

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But the actual landing distance is the unfactored distance without the 1.67 safety margin for dry runways;

 

Dispatch requirement is 1.67

For dispatch you use Landing Distance Required. LDR already includes the necessary factors. If there is sufficient runway available, as there is in Simon's example, you can go.

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As Kevin says, can we stop within 60% of the available runway?

 

60% of 2011m = 1207m (rounded).

 

Actual landing distance = 1207m (rounded).

 

Therefore, yes.

 

The 1.67 factor is what we multiply the actual landing distance by to find the minimum runway length required, including the safety margin.

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Ok guys my head has been in the books too long! So you always want LDA equal to or greater than LDR.

 

so actual landing distance is the absolute distance without any factor been added ie 1.67 or 1.92 for wet?

 

My understanding is that for PLANNING ie pre-dispatch you must ensure your LDR is not more than 60% of the LDA - I don't think that sounds right?

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I'll try again:
 

The actual landing distance is the distance required to stop the aircraft from 50ft over the threshold, using maximum braking, FCOM technique etc etc. This does not include any additional safety factors.

 

In order to dispatch, the law requires that we can stop the aircraft in no more than 60% of the declared landing distance available. To calculate whether we can land, we multiply the actual landing distance by 1.67 (this is actually an approximation, but close enough) to give us the minimum landing distance we require for dispatch.

 

As long as this figure is equal to or less than the LDA we are good -- it includes the safety margin. You don't add safety margins on to safety margins otherwise you'd never be able to get in anywhere!

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I understand thanks. And of course the WET factor is 1.15 or 15 % but thats already in the B/A < GOOD in the QRH PI

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Does TOPCAT use reverse thrust in the calculation for In-flight?

 

Also for In-flight if you use autobrake 1-3 the LDR always equals ALD, But when you choose autobrake MAX and MAX manual the ALD drops below LDR why is this?

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Does TOPCAT use reverse thrust in the calculation for In-flight?

 

Doesn't matter if you're using autobrake. I'm guessing that may be why the MANUAL brake setting is offered.

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I know for the QRH PI credits the use of reverse thrust (well in my JAA QRH does) not sure about other sources, because at the end of the adjustment table you have the option to choose one reverse inop or both.

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