Hi,

sympathy for the crew involved, hope all works out for them.

How about some form of head up display that shows the actual runway ahead, even whilst in LVO conditions. As soon as the aircraft starts its acceleration it shows the approx point of rotation. Could be shaded to accentuate that area. Some form of dynamic principle that varies with wind speed etc.

The company i worked for previously had the weight the aircraft thought it was displayed in the FMC. The V speeds were also displayed, based on that weight. Most of the time it was over the loadsheet weight produced !.

Rgds.

In this era of stiff competition and corporate fat boys wishing to pocket more $$ and their shareholder friends looking for incessant profits , do we have here a culture of "just enough thrust for the job " ? Why go with extra thrust when the runway is long and the airplane is light ??? Sometimes, reality and murphys law comes to bite those who become complacent and behind the aircraft computers and the corporate SOP' s , designed to save a dollar and DECREASE safety !!!

Not AT V1
 

It needs to be something short of V1 where you have time to react. At V1, you're committed.

V1-time should not be too difficult though. It must be used in the V1 calculation already, because that's how you know how much runway is used to get to V1 therefore how much is left to stop - it just isn't an output I guess.

If the input data is incorrect, yes it will be in error but that error is exactly what flags an incorrect weight. Instead of monitoring only V1, you monitor V1 and time - if time occurs first, you abort the takeoff. If this happens you know:
- you are below V1 and
- you have have more runway ahead of you than you would have had at V1, because you have been moving more slowly than planned

This wouldn't pick up an error in the runway length however. It also wouldn't flag an incorrect heavier weight being entered, although I imagine that wouldn't be likely to be catastrophic.

If you reach "time to V1" before V1, you are not at V1 by definition.

The only way it can work is if you abort once the time is reached, before V1 - if you wait until V1 and say "that took too long" you don't have the stopping distance that was used for the V1 calculation. If you reach "time to V1" before V1 and continue, you can be sure that at some point you will be below V1 without distance to stop - because the calculated stopping distance is used up by slower acceleration.

And it can't be a rule of thumb - it has to be a hard go/nogo number like V1, output from the V1 calculation.

Another angle.
 

Lots of discussion about acft weight here, and how it likely to be underestimated. Suggested solution has been to weigh the acft, which is difficult, expensive, and potentially inaccurate.

What about switching to actual pax wt? With the technology available, it would be quite easy to incorporate a weighing system where people checking in stand. That way, pax weights along with ALL the normally un-weighed carry-on baggage is also weighed. No extra time taken, because they are weighed as part of the normal check-in.

Would potentially increase safety, but would almost certainly decrease profit margins. Perhaps the accountants don't want this info?

Carryon weights
 

With respect to carryon bags, and the lack of weighing, how does an airline manage this?

Ie, you have 100 pax, do they multiply that by 7kg to come up with a "Carry-on-bag-weight" of 700Kg as standard, and include that in the ZFW?

Reason I ask is not everyone will have carryon, and not everyone's carryon will be right at the 7kg limit, thereby offsetting the overweight carryon bags for those that have them...

Time to v1 NOT suitable!!
 

Guys,

Although time to v1 looks suitable, it is not!!

It would be if there was a thrust problem. For a weight problem however, you are calculating time to a WRONG v1, with a WRONG thrust. On a short runway, I will not have any indication that I can still stop the aircraft after the WRONG time to the WRONG v1 if I suddenly weigh x tons MORE...
So it is the old saying... BS in, BS out.. and that goes for time to v1 as well...

MR8

KRviator, you have obviously never travelled with EK. How shall I put this? The... "95 percentile" EK passenger is pathologically incapable of travelling with less than 7kgs of hand baggage - and would (does??) carry 70kgs of hand baggage if he/she could lift it. (Granted, not on EK, but on another carrier serving the Middle East), I have seen a long succession of (admittedly tiny) Filipinas carrying backpacks so heavy that it took two others to lift each bag onto each one's back - and then, most could carry it only by leaning forward and when still, resting it on a rubbish bin.

Go on a Lagos flight and you'll find a whole new description for the term "Big Momma" - and the size of the hand baggage they all carry is almost beyond belief.

Seriously though, what you suggested is pretty close to the industry standard. A standard passenger weight and a standard hand baggage allowance in theory allows for the percentage who will be above standard being offset by the hopefully equal percentage who will be below it. Likewise with the hand baggage. However, as has been suggested above, from daily observation, in many areas of the world, it may be time a new standard weight for both people and what they carry to be accepted and adopted.

Again seriously, any form of 'real time' weighing would be a commercial nightmare, which is why it hasn't been adopted. (Can you imagine the fights between captains and load control?) Boeing, and I'm sure Airbus, allow a generous 'bugger factor' in their performance calculations. I've (purposely) done a takeoff in the sim. in a 777-200 forty tonnes over MTOW with an engine cut (severe damage and separation) at V1 +1. It was curvature of the earth stuff, but we did climb away, if at a very low rate of climb, and managed a full cleanup.

http://i101.photobucket.com/albums/m...07-16Small.jpg

I would argue against abandoning the take-off on the basis of a "rule of thumb" speed check against distance. This photo, at Danang 1965, is of the remains of a USAF B57 that used this methodology. The pilot thought his acceleration wasn't good enough, so he jettisoned his underwing load and stood on the brakes. Unhappily, the US Marines had just dug a new series of trenches across the overrun. It was fairly exciting - I was waiting for a take-off to the north at the invert where you see an aircraft turning on to the runway, idly watching a B57 squadron scramble into the south. Suddenly, all these iron bombs were bouncing across my nose, followed by the smoking B57.

My choice would be, when reduced power is used for take-off, is to use the methodology applicable to your type that allows full (rated?) power to be introduced if there is any doubt. Clearly, on types where Vmcg is an issue, that speed would need to be known.

I understand the reasons behind why operators like to use reduced thrust on take-off - noise abatement, prolongs engine life etc.

My question is, does anyone know how significant the effect is? Especially with jet engines - would conducting every take-off at normal take-off power significantly reduce the engine time between overhauls? Or is it more a theoretical engineering idea that's just become ingrained into airline operating culture?

Haven't posted for a while but have just caught up on all the posts after a few days away. I'm no scientist but from what has been brought up in the technical posts......

The 744 had a gross weight calculation system as an option. This was years ago. We never used it, can't remember why. If Boeing built it back in the 80's, then a previous poster was probably right in assuming that the commercial departments of the world discounted the usefulness of such a system in favour of the lucrative "standard weights". Maybe it should be re-introduced. Just how much water are we carrying for those First Class showers.....?

Using a flex temp at a light weight or TOGA thrust at a heavy weight, in the same aeroplane, on the same runway, with the same environmental conditions, will result in you using roughly the same amount of runway. That's the whole premise behind using reduced thrust. You use all the runway and less thrust to get you to the required speed when you are light. If you are heavier, you need more thrust to get you to the required speed before you run out of tarmac. It follows that you should rotate near the same part of the runway regardless of your weight. This is great if you fly on and off that particular runway often. Not so great if you visit 100 destinations a year.

The trend vector shows on your air speed indicator, and is thus an indication of your rate of change of AIR speed (which is what you need to get airborne). The reactive windshear system uses airspeed fluctuations (among other inputs), that you see on the trend vector, to warn you when you get into a windshear situation. Before trend vectors previous posters used timed airspeed checks or distance to go markers (both of which gave you an idea of your rate of acceleration in airspeed). If you have a trend vector, you don't need a timed check or distance to go markers (although Bitchin' Betty the RAAS lady will calmly tell you that you have 1000 remaining). The trend vector is more or less instantaneous and is thus more accurate than a timed check, or gut feeling as you whiz past the distance to go markers.

If we have

• GPS
• Trend Vector
• Wind Vector
• Runway length
• Weight (an accurate one)
• Elevation
• Temperature
• Runway conditions

We should have all we need to tell us whether out acceleration/energy is sufficient to get us airborne before the end of the runway. I know this is all stuff that we work out before we blast off, and that the speeds we come up with are supposed to cover us, but humour me and read on.....

The first three items in the list are aircraft system derived.
The remaining ones are what we punch into the FOVE/BLT.

If you can combine all these elements, (plus a few more, including Bitchin' Betty) would you not have a system that could tell you instantaneously (as the reactive windshear system does) that you have insufficient energy to get off that runway on that day?

It could activate when TO thrust was set (Flex, Assumed Temp, or TOGA) and give you the option of going TOGA straight away or discontinuing the takeoff.

This all makes perfect sense to me at the moment, but feel fee to fire away as I'm sure there is something I haven't considered that will see my brilliant idea shot down in flames!:)

Like Jack Schidt, I have been trying to not poke my retired nose in here, but I do believe I can offer a couple of points not yet fully explored.

The first is a bit of local knowledge. 16/34 is long, but a cow of a R/W. 16 slopes down 0.9%. The threshold area of 34 has a localised slope of about 1.15% before it rolls over and aligns itself with the 0.9% up-slope. This means that it requires a very deep flare to not slam it on, and that necessarily higher flare point at night is always very hard to pick. It’s almost like a crop duster’s strip. On the 727-200 I carried a min of +15 to have extra energy on hand for the flare, and with any wind around, at least +20. So an overweight landing was almost certain to be heavy unless the PF grew up at YMML.

The downhill T/O on 16 can be & has been neutralised by the wind shifts along it. I’ve raised dust myself once, to everyone’s surprise definitely including mine. We rolled into a quartering headwind, but down the other end the sock was showing a stiff tail wind. Acceleration was slow, then seemed to stop, but by that point there was no way we would have been able to stop in what distance remained. You should have heard me go on about V & Distance checks after that! A wooded hill sits in the NE corner of the field, and it (the A/p) is surrounded by deep river gullies, producing marked local wind variations. Swirling winds don't always show at the sock or the anemometers. I can recall two occasions when microbursts out of a clear sky put one 727 down out of site in a gully off 27, and another 727 was held low off 16, rattling a lot of tiles quite a few miles out on the extended centreline. They got away, but both times by dint of being US aircraft which have always philosophically allowed beyond-limit-power to be set, and the engine's reduced life accepted.

I was involved years back in an AFAP tech reassessment of Boeing's wet runway stopping distances, and after a lot of work we were able to prove they were grossly in error. Oz T/o charts are now realistic for Acc/Stop in the wet, but it taught me that what is put out by a manufacturer can be determined by the sales team as often as by the performance wizzes, and I didn’t blindly accept all numbers. I worked through every new endorsement’s charts to produce a summary of rules of thumb, one mid-range speed for every approach, fail, & landing configuration, with a kts variation per coarse weight adjustment. It was soon easy to be within +/- 1 kt of the actual chart, and 3 or 4 times caught a gross error.

Back in the early 60's down at East Sale I watched a USAF C-124 Globemaster heading home to Hawaii. Loaded to the gills and hoping to overfly Fiji, they aborted 6 (yup, six) times before finally raising dust at the far end and disappearing over the curvature of the earth (it seemed). That led me into deep discussions with two other USAF crews, and I have been a convert of their system ever since. Their achieved_speed_Vs_distance check was (& still is as far as I can find on-line) set so that zero wheel braking was used for the abort. Mind you, the tyres must have been jolly hot towards the end, but the check can easily provide a completely low stress abort speed. Speed x time is a coarser check, but 80 kts by 1,800’ was a good catch all. Still is by the sound of it. A friend who has more hours up down the back than I ever got up the front mentally prepares to adopt the crash position on any T/O if the nose isn’t starting to lift by 37 seconds, FWIW.

Personally I think that the most valuable comment in this series was that of Dairyground - what an eye-opener. We aren’t the only safety obsessed people, and it sounds as if the aviator sector may need to think more widely. What >is< ISO9000, and why don’t I know about it? Dairyground?

Thanks all for bringing me up to speed.

This report is going to be an interesting read.

Hey Flyonthewall - thats Trimotors idea! Hands off!

Oh actually its a bit better - still got to get the right weight in there though. And you'll be approaching v1 by the time it finishes its calculation! Think you're on the right track.

Anyway those of us on the big twin are not quite as exposed to these performance things (as long as they both keep turning) - maybe two engines is the answer!

jack schidt wrote:
So what happened to "I wait for the report"?

mig3
 

You asked:
"would conducting every take-off at normal take-off power significantly reduce the engine time between overhauls? Or is it more a theoretical engineering idea that's just become ingrained into airline operating culture?"

No it's not theoretical. Some airlines track the life history of individual engines, so they know how they've been treated and their cost.

But the great experts are the engine manufacturers. Every customer demands a maintenance cost guarantee. The numbers they are quoted depend on, amongst other things, the average derate used. No good using what you call "normal power" and claiming on the maint cost g'tee. It won't wash.

I'm not convinced. If the weight entered is too low, it IS essentially a thrust problem.

(Making numbers up) If your V1 is 120 kt and you need 1000m to stop from V1, if you haven't reached 120kt by the calculated time you know:
- you are slower than 120kt and
- you have more than 1000m to stop.

The wrong time and wrong v1 only cause a problem if the extra weight has more effect on braking distance than it does on acceleration distance. This is possible, but it doesn't sound likely to me.

Time to V1 catches the error where your weight is too high and the thrust is too low - and the errors accumulate to provide extra margin.

V1 is not the whole story. You also need to reach Vr before running out of runway.
If the weight is more than calculated, Vr is higher and acceleration is slower. The computer may sense the slower acceleration, and ask for more thrust, but it should also account for a higher Vr i.e ask for even more thrust.
Might be possible to do in real time but I'm not convinced yet.

It sounds like the answer is not so much the time to V1 or any other speed, but what is your speed after the calculated time? If it's way below V1 you have a problem but also, by definition you have enough tarmac left in which to stop because you're stopping from a slower speed.

Isn't the right solution therefore to calculate how long it should take to get to V1 - if your speed is below V1 after x seconds then reject the takeoff?

Since no-one else has picked up on this, I come back to a point raised by mig3: "use of reduced thrust on take-off - noise abatement".

I may be (I am) out of touch, but I can't remember take-off thrust routinely being influenced by noise abatement. Cut-back is another thing, but start-of-roll?

Not only that, I think it could be counter-productive, as it's best to be as high as possible over the measuring point. Comments?

Hold Baggage
 

The actual mass of PAX, cabin baggage and cargo has already been mentioned.

Do EK use a notional or actual mass for checked baggage? (I'd be very surprised if this alone would "upset" a 340....:confused:)

C o' G

Dairyground;
The timing method was discussed, if I recall, as a sidebar in the Madrid Spanair accident thread. Most agreed that if the takeoff run was longer than about 45 to 50 seconds, it was starting to get into outlier territory.

To be meaningful, timing to V1 would involve a number of factors as we know and, as has been pointed out, would require more accurate weight information than the industry, including the regulators, seem to be presently satisfied with.

A long time ago when designing the FOQA program, we decided to include a takeoff distance calculation for each takeoff. The IRS groundspeed parameter, (sampled once per second), is converted to feet-per-second and summed until the liftoff point. We do the same for landing distance.

Though not accurate to the foot because of the 1" time slices used, it presents a sufficiently accurate snapshot of takeoff performance. Most but not all of our aircraft LFL's, (logical frame layouts) are programmed to record wheel speed (in meters-per-second). The parameter is also not 100% reliable - so we use the groundspeed method. This collected information could then be married with the data you suggest in your post and then compared with the numbers that the "manufacturer sales people provide".

All this requires trained resources which no airline seems willing to provide these days but the matter itself does have data solutions. The fact that the airline doesn't use any of this data in any meaningful or productive way is beyond our control but the information is there for each takeoff to provide a full picture of the fleet's takeoff performance over long periods of time in varying conditions off different runways.

I have to say that Airbus provides far more information for the contaminated runway case for both takeoff and landing which includes the use of the CRFI, (Canadian Runway Friction Index) tables for landing, than other manufacturers I've seen but that's a bit of thread drift.

The travelling public are lucky that development of this "satisfaction" has coincided with engines designed for failures > 1 x10^9 flying hours. Or perhaps not luck at all; maybe it's because engines are so reliable that this relaxed and comfortable attitude with aircraft weights has become normal.

Squiffy- Yes, I think the travelling public is on the receiving end of some very good work over the decades. I think in flight safety work, some sources of "comfort" are justified, such justifications to be found mainly in the data. For example, the data has justified ETOPS work yet serious, (in my, and others' view) questions remain regarding an actual vs. planned diversion under worst circumstances, (pressurization failure, arctic/polar/trans-Pacific routes, etc). Like the case under discussion, reliability has justified the approach taken. And of course, we all know and accept that the risk of failure is always present but has been examined (and hopefully constantly re-examined).

Exactly PJ2. As I've mentioned elsewhere, it all comes down to the actuarial tables. If 1 airframe with all souls is lost at an interval of greater than 10^x flight hours, then that's acceptable.

It might not be correct, or moral (who can tell at what point this happens); but it's acceptable data.

Since we've drifted into the mention of ETOPS - (warning: thread drift of sorts; but something dear to the heart for many EK pilots) - I would like someone to quantify the risk in placing the captain (and on some flights, he is the the only captain on board) in a "rest" area about as far as it is possible to be placed from the cockpit, [which in a 773, is a considerable distance - further, in fact, than the Wright brothers' first flight!] as it is on only EK's 777 fleet, and to a only slightly lesser degree, on EK's A345s and 380s.

(The " " surround the word "rest" for reasons we won't go into here, but mention torpedos, U-Boats and the lack of anywhere where rest can be taken in a sitting position to any EK 777 pilot and all will be explained.)

Others have mentioned in earlier threads the difficulty for a captain or FO to get back to the cockpit from the rear cabin past milling passengers and especially meal trolleys in normal circumstances. To do so after a decompresssion or a cabin fire would be near impossible, at least in good time to have any say in the immediate and not so immediate decisions on how the emergency (sorry - "non normal") is to be handled.

Comments from the panel of experts?

MTOW

Makes no difference where the Captain takes his rest or how long it takes him to get to the cockpit in case of an emergency.

The point is,there should always be aircrew on the flight deck that can handle any emergency without the help of the Captain.:ugh:

Just a wild guess on my part, Whiskery, but I'm assuming you're an FO. (Or senior managment, which your profile would suggest you are not.)

I'm sure MTOW was implying no insult of any FO's ability or professionalism, and nor am I, but if you don't understand the rather pressing desire of the man who signed for the aeroplane and who will be held responsible for the outcome of the "non normal", whatever than may be, to take part in at least the subsequent execution and decision making after the problem has occurred, you come from a very different mental space to the one I come from.

Concur....

ISO?
 

I'll leave it to Dairyground to explain ISO 9000 quality standards in more detail, but in the interim, it is a set of standards for documentation, communication and establishment of standardized work processes across the organization (Six Sigma is another quality standard used in aerospace manufacturing). These don't come down from on high, but are the result of process mapping and collaboration across work areas over time. More importantly, someone is designated as the owner of each work process, responsible for keeping it up to date and in use. The company must be audited initially and regularly by an outside certified auditor, with discrepancies addressed prior to registration or recertification. If something is happening that is not documented, or not happening that is, or worked around, it is addressed at a collective review meeting (did I get that right, Dairyground?).

This extends to not just well-documented work processes required in aviation authority regs like Part type SOP's and checklists, but also the regular corporate functions where things can fall through the cracks (e.g. communication between finance and maintenance). I don't have the full list of ISO 9000 registered firms, but I know UPS Air is ISO 9001 certified, as is United's Engine Maintenance Division.

In terms of its specific application to this thread: In addressing takeoff performance, under ISO 9000 a company should address the full end-to-end process, including some issues raised here that go beyond the preflight and checklists: e.g. availability and distribution of laptops, information available prior to crew pickup, thrust and weight calculations, speed checks, etc. Would checks have been implemented for catching erroneous figures or calculations under ISO 9000 if that's not addressed? Should be, but depends on the effective feedback and input from the parties involved.

The feedback from the accident review will probably serve as an interesting after the fact "audit."

For another perspective from a cynic who's been exposed to 'ISO9000' certification (in a non-aviation industry); it's paper pusher's heaven: Basically you must document your 'process', and show compliance to that process. The process it's self can be as broken as you like, just so long as you have a (documented) process (and follow it). Fixing the process becomes a complete nightmare. It's the sort of thing that makes some people a lot of money whilst getting in the way of real work :E

I will however grant that the implementation may have been badly broken, and the company has since gone bust..

Anyway....

It's being reported in the ME forum that the two gents involved have resigned- read into that what you will.

Did they jump, or were they pushed?
 

"Resigned" or more likely: "Both of you can resign, and in which case, we will gladly accept it, or don't resign, and we will sack both of you".

Pressure bulkhead damaged
 

Latest info from Dubai

Composite pressure bulkhead is damaged along with 3 skin panels, lots of frames and stringers.

Airbus repair, possibly a complete bulkhead replacement.

This bird won't go anywhere for some time

:ouch:

ME Forum?
 

What's the "ME" forum?

Middle East

"ME" is for Middle East:

http://www.pprune.org/rest-world-non...uage-forums-8/

If politicians scr#w up, they ass u me "responsibility", demission and get a thefty retirement for life. The taxpayer pays the mess.

If bankers scr#w up, they get huge bonusses and retirement for life. The taxpayer pays the mess.

If local talent around here scr#w up, they get shiny awards, a house and retirement for life. The expats clean up behind and the fuel-taxpayer pays the mess.

If pilots screw up, they get convicted and fired. They have to come up for the mess themselves, even for the one the constructors, companies and regulators helped creating.

Any pattern here?? :yuk:

Just to see if I understood it correctly, and to give an image to some thoughts of previous posters.

It doesn't stop an error from being input, but given the RWY distance punched at the FMGC/MCDU and all the calcs for the V speeds (temps, wx, weights etc),
you just need 2 more parameters:
- Speed trend vector
- a way of measuring ground distance elapsed(GPS derived or wheel sensor)

Then its easy to determine if you'll be able to reach V1 inside min safe stopping distance, or at least if you'll get airborne at the very end of the RWY without taking the antenas with you. You just have to keep it above the green line.

http://img187.imageshack.us/img187/1...ersusspace.gif

Go easy on the flack! :eek:

GD&L