Question regarding Actual and available Landing distance...

[Global Driver]

Here's a Question that came up the other day:

In a normal situation, lets say that the Actual Landing Distance of an a/c (ALD) is 2500 ft. The Required Available Landing Distance (*1.67%) would be 4175 feet.

Now, for the sake of the example, lets say there was a warning msg of degraded brakes and the QRH instructs you to add 1.55 to your ACTUAL landing distance.

Is your now Actual landing distance 2500 * 1.55 = New Actual Landing Dist ? = 3875 ft? And then add onto that *1.67 = 6471 ft - New Required runway available?

- or -

does the Original Actual Landing Dist * 1.55 fall into the the already enough Available runway required, which is the Original Actual * 1.67?

Your thoughts are as always, highly appreciated.

Cheers!

[mutt]

Actual landing distance is established during certification with a firm landing and exuberant efforts at stopping, hence the requirement to factor this distance for mere mortals PRIOR to takeoff.

However, once in flight this factoring is no longer required, you can land on a runway that is the same length as the ACTUAL landing distance. If you have a QRH requirement to factor this distance, you can legally land on that factored runway length.

But the big question is do you want to? Are you a test pilot? If not, then i would suggest that you take your factored landing distance and apply an additional percentage. This percentage can be 10%, 20% or up to the full pre-departure 40%, it all depends on the aircraft condition and and how you feel on the day.

Mutt

[frontlefthamster]

Actual landing distance is established during certification with a firm landing and exuberant efforts at stopping, hence the requirement to factor this distance for mere mortals PRIOR to takeoff

Mutt, this is a common misconception. Whilst true for almost all aircraft over, say, about 15 tonnes, there are some manufacturers who don't approach flight test for landing distances in such a, shall we say, focussed, way... When we started flying a small straight-wing jet, we soon found that we were achieving the AFM figures very easily, and discussions with the manufacturer revealed that they hadn't put much effort into minimising landing distances during flight test.

The rest of your answer is spot on, though I would add, from a practical point of view, that the factors applied (1.67 and 1.95) are, in my opinion, somewhat excessive for some types of aircraft. I routinely fly small straight-wing jets and heavier metal, and it seems very clear to me that whereas I would never aim for the piano keys in a large aircraft, we do so with ease and repeatable accuracy in the small aircraft, at the same time minimising touchdown scatter. (I won't comment on turboprops where such visual aiming reductions are permitted). It would be very helpful if we were permitted to use this technique to reduce LDRs, especially given that in Europe, many runways at small regional airports (exactly where we, and our passengers, want to go in a biz-jet) are of lengths about equal to our factored LDR.

Instinctively, a factor of about 1.4 seems very reasonable for these aircraft on dry runways.

Is there any evidence that runway overruns are more common in private operations than transport? I don't think so...

[potatowings]

Actual landing distance is established during certification with a firm landing and exuberant efforts at stopping, hence the requirement to factor this distance for mere mortals PRIOR to takeoff.

However, once in flight this factoring is no longer required, you can land on a runway that is the same length as the ACTUAL landing distance. If you have a QRH requirement to factor this distance, you can legally land on that factored runway length.

I understand the test pilot situation and certification, however, I had no idea that once airborne the factor no longer applied.

Are you sure about this?

Obviously in an emergency you have got to do whatever is needed... but lets change the scenario a little. In flight your pax tell you they no longer want to go to your massive 1.67 factored runway and want to go to that tiny little airfield off the left wing. It's LDA is exactly what's stated in your manual. Can you can legally put down there without any factor (assuming the AFM doesn't require it)?

[Green Cactus]

potatowings, no you can not.

In this situation ops 1.515 still applies, which means the same requirements exist as if you were on the ground.

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.

GC

[potatowings]

Thanks GC,

Thought it was too good to be true.

I couldn't see why a factor would be implemented prior to departure but then suddenly vanish once airborne.

:ok:

But please excuse my ignorance. How does this effect the original question in the post? Which factor is relevant?

My guess is the most limiting one?

[mutt]

FAR 121.195 states....no person operating a turbine engine powered airplane may take off that airplane unless its weight on arrival, allowing for normal consumption of fuel and oil in flight (in accordance with the landing distance set forth in the Airplane Flight Manual for the elevation of the destination airport and the wind conditions anticipated there at the time of landing), would allow a full stop landing at the intended destination airport within 60 percent of the effective length

So getting back to the original question, once you are inflight you can forget about the 60% rule whilst applying corrections.

I assumed that as Global Driver is based in Tel Aviv, he most likely isn't operating a JAR registered aircraft.

Following the Swissair MD11 crash, aircraft manufacturers very rapidly stated producing ACTUAL landing distance charts in their manuals together with DISPATCH charts, there is nothing on these charts stating that they can only be used in Emergencies as their use is permitted by FAA regulation.

Mutt

[CL300]

Can you take off with your degraded brakes?

If not, then issue is closed. Generally the manufacturer are giving advisory material in order to assess some conditions. So while in flight if the cas message appears then you have to factor you landing; not everybody flies commercial, as a consequence if LDR=LDA in your normal private Ops, it is worth considering another landing spot or you will surely end somewhere not black and solid.
Commercially, if you are dispatched under MEL with a known deficiency on the brakes...hummmmm theory then...you have to factor everything; like fort wet runway 1.62 x 1.15 ( 1.92); if tailwind expecting as well, etc...so your factor of 1.55 is part of the equation. If problem arise in the air, captain decision..LDR with the new factor < LDA.... shall I go ? you are expected to go , will I take off again ? worth looking into the MEL.. Company in the loop and so on.

Private...another story, better speak with the Boss....safe side rarely hurts...

[potatowings]

Thanks for your reply Mutt.

I think that we've got to semantics now. Why on earth would any authority ensure you factor prior to takeoff yet then erase that factor as soon as your wheels are up? That's crazy.

I believe the spirit of the legislation is simple. Before taking off, you have to know you can land factored. I believe that in flight, in normal circumstances, without any emergency, you must still be able to land factored.

[frontlefthamster]

Why on earth would any authority ensure you factor prior to takeoff yet then erase that factor as soon as your wheels are up? That's crazy.


Why would it be crazy? Just interested in why you make such a strident post...

[CL300]

well , this is telling you that you really need this antiskid system ...
Disregarding the fault at planning stage is just against EU-ops; but again, you may operate on a set of regulations that allows you to disregard the fault.

MEL are there to help the operator to move the aircraft out of remote towards a maintenance facility; there was ( and still is) a lot of abuse of MEL, commercial pressure and so on.

But if the manufacturer is telling you that 14000 ft is required.....( factored i understood) for landing... worth considering fixing the problem, or indeed your destinations are scarced..

[Green Cactus]

Global driver,

As I (in Euro land) understand how this works.

During normal ops before departure or in flight you have to factor so ldr*1,67 if dry or ldr*1,92 when wet (I'm not getting involved in grooved or not at this time, different discusion). if prior to departure you have another issue (your brake example) you will have to add that factor.
So in your example, multiply the initial result by 1,55.

If this happens in flight (I'm not getting into discussion when a flight starts, is that off-blocks or airborne). And the failure effects the performance of the airplane (which it does in your example). you can disregard the initial factoring and be legal (but maybe not smart...) with just ldr*1,55.

What I have been doing is: I do not accept anything less than the initial (before departure) requirement.
Unless in an emergency than all of this goes out of the window.

As I said before this is how I understand it works, I do not have a readily available reference.

GC

[keithskye]

A lot of references made here to the regulations regarding runway requirements seem to be for you AOC/Part 135/Part 121 operators. As far as I know, ALD numbers are all I need as a non-commercial aircraft. I know that holds true in the US for N-registered aircraft, but how about M or VP registered aircraft operating in Europe?

[eckhard]

frontlefthamster,

Is there any evidence that runway overruns are more common in private operations than transport? I don't think so...

I think if you visit the NTSB website and research Citation accidents, you'll find that the majority are caused by landing-related problems, such as over-runs.

I haven't made an exhaustive study, but the impression one gets is that most of these accidents occurred during private operations. My reasons? Most of the smaller Citations are certified for single-pilot ops and many are flown by owner-pilots. Nothing wrong with that, except for the self-induced pressure to plan a flight to a runway that just meets the book figures for landing distance, making a mess of the landing (height, speed, touchdown point, retardation, etc) and then not salvaging the situation by going around.

I agree that 1.67/1.92 can seem excessive at times, but experience has shown that even professional pilots get it wrong sometimes, and that extra distance may just save the day.

I advise my private Citation pilot friends to plan their landings with a factor of 1.5. This seems sensible without being unnecessarily restrictive. The Cessna AFM factors the dry distance by 1.35 for a wet runway*. Using 1.5 as a planning factor means that even if you arrive and find that the runway is wet, you'll still have an 11% margin over the AFM wet figure. (1.35 x 111% = 1.5)

If you insist on private operators using public transport factors, you'll lose credibility. They will say, 'I saw Joe land on that 3000ft runway with his CJ, so why can't I?' Better to give them something realistic and to educate them in the critical importance of flying an accurate approach, using the correct stopping techniques and most of all emphasising the need to go around if in doubt.

The other day I watched from the RHS as a private CJ owner/pilot landed on a 'short runway' of 3650ft. He stopped in 2600ft. The AFM predicted 2650ft. The public transport required distance would have been 4425ft, which would have made our landing impossible. It would have been very difficult to convince him that what he just did was 'dangerous'.

This was in daylight with a dry runway and a slight headwind. Also, he placed it on the ground at the right speed, in the right place and did a great job of selecting ground flaps and braking immediately. That's why he made the 'book' figures.

In other words, this was a 'best-case scenario'. The safety factor under these conditions was 3650/2600=1.4 which is not bad, but still less than the recommended 1.5 for private flying and considerably less than the 1.67 for public transport.

The safety factors may seem excessive, but they are there because it is so easy to get something wrong (speed, height at the threshold, touchdown point, delay in selecting ground flaps, etc). He got it all right!

But to get back to the original question: I think it's already been answered.

For planning, you must apply the factors. Once you are airborne, you should still check that you meet the factored performance when you arrive at your planned destination or alternate (and you should, barring unexpected tailwinds en-route). However, if you suffer an in-flight problem that increases your LDR, or if you divert to an unplanned diversion airfield because of an operational issue, my understanding is that the AFM figures can be used at the PIC's discretion. This 'alleviation' should of course not be used to take advantage of any defect that factors the LDR by less than the public transport figure!

*US registered CJ series. Figures approximate.

[request visual]

The landing factors are for planning, in the air you can use actual landing figures. This is according EU OPS.

[Green Cactus]

request visual,

Where in eu-ops have you found that little gem? Eu-ops 1,515 says the opposite of your statement.

GC

[CL300]

I think he means, that at the planning stage you need to comply with 1.67 and 1.15 eventually, BUT if a failure occurs in flight you can go for LDA + any manufacturer recommandation.
A bit like that you cannot plan wet if it is dry, in order to reduce the screen height for example, because everytime the nominal conditions have to be verified, and the most penalizing has to be taken into account.

[Green Cactus]

cl300,

I hope so, but he/she would not be the first to say otherwise. Now it might be true (I'm always willing to learn), but if so please give me the eu-ops reference.

GC

[request visual]

@Green cactus

EU OPS 1.515 say's that the landing mass determined in accordance with 1.475(a) shall be factored.

1.475 is valid at the start of the take off or for inflight replanning.

Thereafter the factors don't apply anymore.

Cheers,

[Green Cactus]

Request visual,

If you continue reading 1.515 you will find this section:

Before commencing an approach to land at the destination aerodrome the commander must satisfy himself/herself that a landing can be made in full compliance with OPS 1.510 and subparagraphs (a) and (b) above.

Or is there somewhere a section that clearly states, you can disregard al factoring once airborne?

GC

[Mad (Flt) Scientist]

#GC

That quote is part of a section which addresses the special case where the destination at dispatch does not meet the factored landing distance criteria, but the alternate does. It is not a general provision which applies to all cases.

The FULL text of 1.515(d) is
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.

It's a very special condition and not a general requirement.

[mutt]

MFS, good to see you jumping in here :D

Presuming that the original poster "is" flying a Global Express, can you please tell us what certification criteria was used with this aircraft? My personal opinion is that it should be treated like an airliner whilst in operation.

Rgds

Mutt

[john_tullamarine]

If I can put a simpleton's thoughts to the question ...

(a) the factors are the result of a lot of history and appear to be able to stand the test of real world operations

(b) let's suppose we put the rules to one side for the moment ?

(c) here we are, out for a nice day's flying, and, for whatever reason, need to land ...

(i) if I have a runway with the normal factors available, then I will be relaxed in all likelihood

(ii) if I don't then I will be looking to prioritise the available runways according to various criteria including length

(iii) if I only have around the OEM's actual figures, then I will be very concerned and expect to go off the far end at a lowish speed (and I have been in the aircraft during performance landing trials and the exercise frightened me witless)

Now,

(a) if my worsening predicament was caused by one or more abnormals or emergencies, then I would be declaring the situation, go for the overall best risk situation and be quite prepared to argue my case in court after the prang

(b) if my prang had something to do with my being a bit cavalier and taking a "short" runway just because I thought it would be a good idea .. then I'd not be all that enthusiastic about my chances in court afterwards.

[rodney rude]

Mutt states
FAR 121.195 states....no person operating a turbine engine powered airplane may take off that airplane unless its weight on arrival, allowing for normal consumption of fuel and oil in flight (in accordance with the landing distance set forth in the Airplane Flight Manual for the elevation of the destination airport and the wind conditions anticipated there at the time of landing), would allow a full stop landing at the intended destination airport within 60 percent of the effective length
So getting back to the original question, once you are inflight you can forget about the 60% rule whilst applying corrections.



Mutt you have it soooo wrong.

The rule is, unambiguously, if you have the problem at dispatch, you must not go unless all factors are taken into account for your landing. You MUST factor by 1.67 and then the brake degradation factor.

If you dispatch a serviceable aircraft and get the problem after airborne, then and only then the factors do not apply.

You are using semantics by highlighting the take off bit. If you take off and say once airborne I don't need the factors, then you have in fact done an illegal takeoff. Why? - because you conducted the take off whilst planning to land at a destination where your landing weight was such that you could not meet the factord landing distance. So you breached the takeoff rule before you got anywhere near your landing.

This is the rule and that's that. Don't mean to sound arrogantly forceful, but if you took Mutt's view, why on earth would any rule about this have been written in the first place???

[mutt]

Rodney rude, I never said to IGNORE the problem until airborne and to do so is totally illegal. To me the rule is clear, if you have the problem on the ground you account for it during takeoff and landing by applying the applicable penalties and apply the applicable factoring. If you have the problem inflight you account for it during landing with the applicable penalties, no factoring required by "regulation".

Mutt

[Mad (Flt) Scientist]

Agree 100% with mutt, except to add also that if you have a system failure which would require you to consult either the abnormal or emergencies sections of the flight manual, then even if there are no additional distance factors in the AFM you should not be dispatching unless the MEL provides coverage to do so.

if it does provide such coverage, then the MEL should also provide the instructions for dispatch, including any additional performance factors which should be applied. If for some bizarre reason it provides no factors, or factors which differ from the abnormal procedures, my take would be that the MEL is the legal authority to dispatch in the configuration, and applies. (Though if the difference is significant I'd be asking myself, and the OEM, why)

To answer mutt's question, the GEX was certified as a Part 25 aircraft, to the same sets of rules as other large transport category aircraft. It also meets the majority of the operationally derived design requirements for a Part 121 or equivalent operator (here I'm thinking things like FDR rules) but there are some exceptions. Right now there are no GEXs in actual airline operations (that I know of), and so I don't believe there is a reinforced cockpit door available (to give an example). There's also no explicit ETOPS operations, although obviously the aircraft has the performance range-wise to be well into ETOPS territory. I'm not sure if any of the Part 91 (or equivalent) operators use ETOPS-equivalent planning for their long overwater routings.

[CL300]

ETOPS below 100000 Lbs ? EROPS yes... The Glex was the first to be able to face the 180 min OEI rule; the Glf are approvable as well. I am not aware of similar rules for FAA land..
AFAIK, private operators just fly.....everything else is just a plane... LoL

[rodney rude]

Mutt are we saying the same thing a different way? Noted, no you didn't say just ignore it.

1. Problem exists on the ground with brakes. 2 factors required, 1.67, and the braking factor. If actual landing distance (normal, no failure ops) x 1.67 x brake problem factor is longer than the landing distance available -- no go.

2. If problem occurs airborne, 1.67 factor disappears. All you need is actual landing distance normal ops x braking factor.

If number 1 above is the case, and the lda is not long enough, maybe you could flight plan somwehere else that meets the lda requirements and then do an inflight divert to where you really want to go - but is that flirting with the rules to make it work in your favour?? I'll leave that one up to you as to whether that is good airmanship or not. But realistically, in the corporate world, if you can get the boss there, then do it.

I hope that clears up my first post interpretation. Have a great day.

Rod

[Green Cactus]

rodney,

You legally cannot do that, you are inflight replanning. That means all the factoring has to happen at point again...

The real question (in my mind) is: how happy is the boss if something goes wrong and you slide of the end? Most bosses (all the bosses I have worked for at least) accept no, they have hired you to take them safely from a to b.
And if b is not possible think of an alternate destination, I've never had a problem that way.

GC

[mutt]

maybe you could flight plan somwehere else that meets the lda requirements and then do an inflight divert to where you really want to go Are you for real? So what other rules do you think we should consider to be "inconvenient"?

Mutt.

[rodney rude]

No Mutt, not for real. Let me clarify.

If tone of voice could come with the written word then what I said would be clearer. I re read my post and it is clear to me that when I mentioned the inflight replanning idea AND THEN said "but is that flirting with the rules to make them work in your favour. I'll leave that up to you to determine if that is good airmanship or not." Usually if someone says that then the answer they have themselves is "No its not" And that is my stand on it. No its not. But granted my last statement does tend allude to me feeling it is okay to flirt with the rules. I didn't mean that. But its hard to argue against that is how it looks.

I am surprised at your response - I thought my earlier posts in response to you was EXACTLY that you cannot ignore the rules before departure and just say its okay, the rules change airborne. My stance has not changed. You cannot ignore the factors prior to departure. If you do you are flirting with the rules and it is not good airmanship. I was never suggesting that that is what I'd do.

[macjet]

Hi Chaps,

I've been reading all this with some amusement as some seem to get wordpicky...

EU-OPS want you to have your landing distance factored by 60 % before you takeoff. (Commercial transport!)
This is also done, to include possible system failures and still be able to go there safely.

The factored ALD (actual landing distance) is called LFL (landing field length) in Bombardier books. This must be met at your destination before you takeoff.

The QRH that is mentioned in the very first post applies only in flight (so after takeoff) therefor the already factored distance ALD x 1,67=LFL is still good to land as the failed system asks for ALD x 1,55 only.

The tables provided have to be used when you handle the (at takeoff) unforeseen system malfunction.

Regardless of private or commercial, EU-OPS or other regulations, the GLEX QRH Volume 1 has a section called GO/NOGO in the back. (That's where you look if suddenly a MSG comes up before you leave) - and it says with BRAKES DEGRADED - NOGO.

So not even worth the discussion if you have to factor twice your landing distance, because you simply should not take off with that MSG.

A document that we would surely have to consult before takeoff with a component failed is the MEL.

There, I do not know any system that would require a longer (factored) runway on landing.

have a nice evening

MJ