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

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

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.



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 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,

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