It is over 40 seconds for a CFM to spool up from idle at FL 370 with ISA conditions. I've timed it.

100% correct, longest 40 seconds I have experienced.

A little good news, my counterpart on the 737NG tells me that 7.B.W EEC s/w will improve the accel characteristics at altitude. Should certify this summer.

Yes caution is in order if in actual turbulence or if it's forecasted ahead.

But, NO, that was not what you were saying before:
But, I am happy if the discussion changed your mind a bit. :ok:

I play with the computer instead of letting it play with me:
http://www.pprune.org/tech-log/52429...ml#post8096769 (post 108 if the direct link doesn't work).
If you don't care to read it, let me ask you: What factors determines the MAX ALT? Which one can we be certain of? And which ones are uncertain? Which ones are factual? And how do they individually affect your max alt?
I can think of one example where I would have no problem climbing to FL390 with max FL384 (or lower) show... It's in the post that I linked to. :)

Cosmo,
Do you have a procedure to modify the cruise CG? We don't unfortunately, but when it is changed from the default 15% to probably a much more realistic 19-22% the max alt 'magically' increases significantly :D

Sorry about this, but from that other thread:
However, I do not set CON routinely, only when I suspect it might actually be needed inline with the FCTM and the recent Bulletin. I don't see any specific issues with CON mind, just CRZ is the intended thrust limit for cruise and I prefer to operate these strategies with specific criteria in mind rather than get into a routine that is, strictly speaking, a deviation - however trivial or slight (or non-existent in impact) that deviation may be.

Cosmo
 

My whole point about crz level was on very heavy aircraft crossing temp/wind zones and the sudden narrowing of the overspeed/under speed margin.

Our EFB provides us with a very accurate MAC because we use allocated seating and know where the passengers are seated re zone a,b,& c we subtract 4% from the MAC for FMC perf page and can re calculate inflight after fuel burn off if necessary

This from Boeing FCTM
Maximun Altitude

Maximun altitude at which the aircraft can be operated, It is determined by 3 basic characteristics (for each model) The FMC max altitude is the lowest of

. max certified altitude

.thrust limited altitude - the altitude at which sufficient thrust is available to provide a specific minimum rate of climb (depending on the thrust rating of the engines), the thrust limited altitude may be above or below the manoeuvre capability

. buffet or manoeuvre limited altitude

Although each of these limits are checked by the FMC , available thrust may limit the ability to accomplish anything other than relatively minor manoeuvring. The amber band limits do not provide an indication of manoeuvre capability as limited by thrust.

NOTE to get the most accurate altitude limits from the FMC ensure airplane weight, CRZ CG and temp entries are correct

You provide some interesting and thought provoking comments and i always welcome that from anyone, but you are in my humble opinion acting in a manner that at best will confuse and more likely intimidate your co-pilot, i would be very interested to know if your company procedures allow you to do this and exceeding the FMC derived maximum altitude its is done with blessing of your pilot/training management? the fact that the aircraft may be able to achieve it secondary to the limitations and what do you suppose would happen to you and your co following an high altitude upset where upon the FDM showed that your were above the max altitude? the reason for the upset is not relevant but if there were injuries arising from the recovery then i suspect the lawyers would have a field day, so why Capt Kirk did you think this was a good idea?

Don't get me wrong, i don't doubt that you are a committed and experienced Capt but the fact that your F/o's are having to be re educated by you on the subject of high altitude flights suggests either your training department is at error or dare i suggest it without offending you that perhaps you should reflect upon your own style of operation

Either way fly safe 41'000 is for biz jets or big aeroplanes with big donks :cool:

PS the next update of the FMC will provide a thrust limited altitude for manoeuvre

It must be a Boeing thing then. At FL320 on the Airbus it takes more or less 15 seconds. Reducing speed at FL380 from M .78 to .72 commands idle thrust...and the thrust comes back on decelerating through .74

LNIDA, no I wouldn't go above max alt, as displayed by the FMC.

What I was trying to get at, was which input the FMC uses to decide on these limits. One that is oft forgotten is the selected speed. The FMC doesn't calculate the max altitude, based on the most optimum speed for that level. It uses the speed you have already select (or cost index you entered), assuming you will want to continue with this speed at the next level.

If this speed is very high or very low, the FMC will show you your max alt lower, than what the aircraft is capable of, if you change your speed. Hence, I can get the FMC to SHOW a very low max altitude, but still climb safely above it. Of course I would change the input to show something sensible before actually initiating the climb.

THIS is what my point is, an extra xxx feet becomes arbitrary, if you don't consider what input is behind it. My only concern is instead this:

"How big is my speed window in the new level." In smooth air my personal limit is 10 knots between the low and high speed maneuver band. In turbulent air, I might want to see 30 or 40 knot, which may be an even bigger margin than your 1000 feet. The difference is, I know what I am getting, and you are not.

By using the FMC, like I described in the other thread in post 108, you will always know exactly how big your speed window is, regardless of other factors. Still of course your weight, cg and temp needs to be fairly accurate.

If you are bored in cruse on you next flight, play around with the values to see how much e.g. a ton extra ZFW, moving the CG 5 units etc. affects your margins. If you suspect the aircraft to be heavier, than the values on the load sheet, you will the have a feel for how many knots that actually change on your margins.

A good eyeopener for a new F/O is to increase the ZFW with 10 tons. At first they see the and unbroken yellow band from minimum speed to MMO, they become a little wary. But after a few seconds, when they see the aircraft doesn't care and happily keeps flying, they become relaxed and and realize that what the computer says doesn't aerodynamically affect the aircraft. Garbage in garbage out. It's still just a stupid computer and the reality of nature determines if the aircraft will fly or not. And no, I don't don't do it to bother them. ;) But to increase their confidence in what they see and feel is more real that what the computer calculates.

The FMC already consider thrust limited altitude based on a residual rate of climb of 300 fpm in the climb and 100 fpm at cruise using LRC tables.

I think your speed spread dependant upon conditions is entirely reasonable and i have also played around with the ZFM and as you say it is interesting to see the yellow bands close.

I want the FMC input data to be as accurate as is reasonably possible.

I am aware of an aircraft that departed with the correct v speeds from an EFB but a -10000kg figure in the FMC which then told them they could go straight to FL410 needless to say despite trying they didn't get there oops

The FMC does consider thrust limited altitude, but the amber band limits do not provide an indication of manoeuvre capability as limited by thrust. The next software release will correct that.

My last comment on the subject.....promise

Thanks for the discussion, I enjoyed it. :)

Could not agree more.
Have seen quite a few overspeed-in-the-cruise-reports for the A320 over the years, and people intervening - reducing thrust, speedbrake, lifting nose etc. almost invariably make the situation worse.
The A/C is a completely different beast at cruise level, and people are not used to it.
As earlier mentioned no inspection is required if exceedance is less than 20 kts (and I have never seen one higher) , so let the A/P+A/T sort itself out, and write the ASR........

Of curiosity, do you need to make a tech log entry? And if so, can you sign it out yourself.

On Boeing it's a mandatory tech log entry, and only a certified maintenance technician can sign it off. Hence, an AOG item when flying to a remote airport with no maintenance.

P.s. On Boeing it's a non-issue to use speed brakes.

OSCAR YANKEE
The autopilot ATHR may not sort it out itself and could lead to more complications. Less than 20KT no inspection is required but crew must report it. The procedure mentioned in my earlier post is given in FCOM:


OVERSPEED PREVENTION

Ident.: PRO-ABN-10-00014874.0001001 / 08 FEB 13

Applicable to: ALL

A318/A319/A320/A321 FLEET PRO-ABN-10 P 11/20

FCOM ← D to E 06 MAR 14
OVERSPEED RECOVERY

Ident.: PRO-ABN-10-00014875.0001001 / 08 FEB 13
Applicable to: ALL
FCOM page F

QRH only gives the recovery procedure.
Abnormal emergency procedures ABN80.06A

I want the FMC input data to be as accurate as is reasonably possible.

I suggest it is time to consider increasing the, IMHO, rather ludicrous low ICAO standard pax/baggage weights. It could well be that on a full 189 seater a/c you could be 2 tonnes heavier than the load sheet tells you. If all male, full baggage at 20kgs, it will be much more.

Regarding the CRZ MAC, it seems some companies allow you to insert the actual number, others forbid it and stay with the default 5% (B737NG) for a safety buffer. Going up to absolute max alt and reducing to 1.2g if no turbulence is forecast is really taking TEM management to the limits. The forecasts are made hours in advance by computer models and differ depending on the meteo centre who made them. Their accuracy is unreliable. I say this because I've been through areas of forecast turbulence with nothing, not even a cough. If that is the case then the forecast of no turbulence must also be questionable; although the met forecasts in all cases e.g TAF's etc. seem to be always pessimistic. I thought we were in the risk avoidance business.

@vilas

I am well aware of the advice in the FCOM.

My opinion is strictly personal, but is based on having read the reports, and seen the flight data from those reports where people have used speedbrake, idle thrust, lifting the nose etc.

Airbus has to give advice like this, because they cover any overspeed.

I dont think my company has seen any excursions higher than 6 knots in the cruise, and the observations were quite clear.
People exacerbated the situation by intervening, and you were left with the sensation that they would have been better off just leaving the A/P+A/T to sort itself out.
(However you cannot know of course, it is speculation, albeit qualified.....)

OY, I fully agree.

But we have to realise that we are of a dying species, the one with experience and some common sense left. We are overwhelmed by the new generation who religiously follow the magenta line, the FCOM and SOPS without filter or questions.
Remember the former UAS by Airbus, that was amended after some incidents? It shows that not everything straight from the A/B horse's mouthes is incontestable and of final wisdom.

Gretchenfrage
"Vanity is my favourite sin" Al Pacino (Devil's advocate) You will love this movie. You read my profile and decide for yourself about my generation. However as I have mentioned it before that armed only with FCOM developing procedures on FBW aircraft is asking for trouble. If experience on line differs from a procedure I agree you have to do something to salvage the situation but after that get in touch with the manufacturer. For all the experience on line you do not become a test pilot nor do you get any insight into the computer logics. You may have noticed many things suggested on PPRUNE vary from highly professional to downright dangerous. None of them can replace SOPs.

vilas

Well, if you throw a stone at a herd of sheep, it's the one who gets hit that yells ....

On another note: I don't quite get you:

One one hand you say ...

... on what i could agree with you, only to hear you state ...

... which puts you right back to the pilots i fear, citing solely FCOM, QRH and ABNs, as in your post below.

Now what is it?

You can recite whatever you want, i will stand firm that on a high speed excursion at high altitude the chances that you will expose an aircraft to a dangerous situation are very much slimmer than falling into a very much more dangerous low speed situation when extending speed-brakes.

Once more: The last decades saw no aircraft crash due to high speed at altitude, but several crashed due to high altitude stalls.

Your choice where common sense lies.

But we have to realise that we are of a dying species, the one with experience and some common sense left. We are overwhelmed by the new generation who religiously follow the magenta line, the FCOM and SOPS without filter or questions.
Remember the former UAS by Airbus, that was amended after some incidents? It shows that not everything straight from the A/B horse's mouthes is incontestable and of final wisdom.

Slight thread creep, but I have to admit I always taught Boeing incipient stall recovery from stick shaker was, 1st elevator then a split second later add thrust. Guess what it is now. Aerodynamics on a basic aeroplane had never changed. I did, also, demo a stick shaker recovery from low level flight with A/P engaged by just adding power. It was always interesting, so they saw both sides of the coin. It wasn't going to work at medium levels or above, but….
Sadly, now, the syllabus I have to use does not include time for such demos. The knowledge transfer is much less than it was. Time is too squeezed.

Gretchenfrage
All I am saying is involve the manufacturer. They are in touch with operators across the world and are aware of incidents that happen. They have all the resources. You cannot device something on your own. If there is a problem they are answerable. You cannot replace a procedure listening to someone.

Spool up time well yes takes a bit. Airbus speedbrake retract time with A/p engaged takes an age. Airbuses o/speed technique seems a little optimistic. :eek:

Gretchenfrage
The reason I keep saying involve the manufacturer is because of FBW. A conventional response to an under or over speed may not take into account the aircraft behaviour due normal law protections. There have been incidents of AP disconnection due over speed and then subsequent engagement of alpha prot causing rapid climb resulting in near air miss. There have been low airspeed events without any failure but due to unusual environmental changes. We know that a pilot cannot expect survive by his own experiences alone. The manufacturer with his resources provides a better platform to tackle these events. Experience is not a name given to mistakes we committed and got away.

vilas

Don’t get me wrong; I sure enough don’t dare excluding any manufacturer. With the complex aircraft we fly, as a pilot it would be preposterous to think we simply know better.

Experience however should keep us alert. FBW is not the wonderful saviour the industry likes us to believe. There are still traps involved and, worse, reluctance to correct them due to some engineer’s pride, but mostly due to the deplorable pack of wolves called litigation lawyers especially from the USA. Any change, even of the most obvious design flaw, would have them backtrack any former incident involving the design, ensuing an avalanche of lawsuits.

The thread starts with the question of thrust reduction in case of overspeed:
Is it ok to go to idle, or should we follow the manufacturer’s advice to only go halfway and use speedbrakes.
Some say follow strictly manufacturer’s FCOM/QRH/SOP, others are quite reluctant to extend any speedbrakes.

We can debate for hours, but here’s the problem:
1. Aerodynamically it makes basically no sense at high altitude to destroy something we are normally struggling for, namely lift.
2. Overspeed at high altitude has not caused an accident in recent times, low speed (or low lift) has.

So why would any manufacturer want lift destruction to counteract high speed??

One of them because his FBW would climb in case of massive overspeed and I hope we all agree that this is undesirable. Another one because he wants thrust levers only halfway back due to its engines unusual long spool-up time.

In both cases I raise the ominous “Gretchenfrage”, the core question:
Why does the manufacturor not cure the sickness and simply fights the symptom? I say:

Get the FBW or EEC logic right before you suggest manoevers that put us in a worse situation to counteract the flaw!

That is what I mean by not unconditionally trusting manufacturers, FCOM/QRH and SOPs. They have an agenda that is called profit. I have one that is called survival, in the economical and physical sense.
They do not always match!

Aerodynamically speedbrake extension creates drag to slow down the airplane. There is no lift destruction. Lift is maintained otherwise the airplane would start descending. Speedbrake extension reduces the maximum lift capability, but that is irrelevant because, firstly, the airplane is far removed from the maximum lift capability in an overspeed situation and, secondly, if the airplane slowed down to near its minimum speed it encounters buffet well before reaching the maximum lift capability, which is immediately restored upon retraction of the speedbrakes.

AFAIK the recommendation to use speed brake has no relation to the functioning of the overspeed protection feature.

I don't know the reason for the long spool-up time at high altitude, but I think it is more likely to be the engine's surge margins than a 'flaw' in the FBW or EEC logic.

@vilas

The manufacturer has to cover liabilities, and keeps that in mind when writing procedures.
Certain things they just drag their heels on. Denying issues at first, and then when presented with irrefutable facts, just say "this will be sorted in a future release".
We have had issues that took years for them to sort, still one outstanding A/THR issue thats been known for 5 yrs plus that they just get on to.......

Gysbreght

I sincerely hope you are not a commercial pilot transporting SLF in "thin air"!
At least your statement made me stop reading your contribution any further .....

Gretchenfrage,

no need to get personal ...

Gretchenfrage @OSCAR YANKEE
Since you went back to the original thread if you read the posts you will realise that those are not all from Airbus pilots. It is a mix bag neither all are of them are from their own experience either. Somebody says good idea somebody say bad idea another says it's settled. I quoted A320 official document and before it went in there Airbus gave elaborate presentation about the issue. I don't think anybody carefully read what it say. It just says to leave everything as it is and select lower speed. This what busav8r, Oscar Yankee said and you support it and yet you disagree because Airbus procedure says same thing. Your opposition is perhaps to use of speed brake. That comes when things have gotten worse and recovery procedure is required. We are faceless entities can say anything to each other doesn't prove a thing so don't so condescendingly include yourself in a threatened specie no grant would be forthcoming for your conservation.

Gysbreght
I might have gotten a little personal if i read complete nonsense, sorry for that, but it is after all a pp forum..
Pretending that speedbrakes do not destroy lift is such nonsense. Why on earth would the red/black tape jump up when you deploy them, if not for loss of lift and by the way, we call these devices spoiler as well. They spoil what exactly?

vilas
Condescending or not, its the recipient who decides. Anyway, it is by far not only an Airbus matter, some experienced contributors here include Boeing as well, as their speedbrake logic is not beyond doubt, especially for such manoevers we discuss. But keep on adopting everything that is in the books, that makes you just the same faceless entity and no grant would be forthcoming for anyone who religiously follows sop into an incident, believe me.

Never stop expecting the unexpected :ok:

@vilas - have a look at this one:


Incident: Jetstar A320 enroute on Mar 12th 2014, alpha floor activation

;)

OSKAR YANKEE
Thanks for the article. The action of the pilot in this are in between what you said in post 91 and mine 46 and 51.You wanted to just observe till things sort themselves out and AB procedure said keeping AP and ATHR on just reduce speed and speed brakes as required. He did this but it was his judgment at that point that it wasn't working and he disconnected all automation and that complicated it further. I cannot question his judgment but I think having followed the recommended procedure he could have waited to see the results before disconnecting the AP because it appears that the speed trend and not actual speed triggered further actions. But if selecting lower speed and speed brakes were not enough then doing absolutely nothing and leaving things as they are may have been worse.

The only thing to do in this scenario (high rate of climb at high alt, and increasing speed) -which an experienced airbus pilot will tell you - is to press VS0, and select a lower speed eg. .76.
This will arrest the climb and level off the A/C. (You might have to press VS0 a few times, if the a/c is already in ALT* (or ALT aquire in Boeing lingo.)

Then when the a/c has regained its composure you select V/S climb with a low rate eg. 500 fpm and monitor it closely as it creeps up to level.
(The rate of course depends of the weight and thrust rating of the A/C).

This way you avoid the drama of a high workload situation involving speed brakes, closure of thrust levers etc.

As a note. These comments are not intended to put down the individual involved in the situation.
He/she found himself in an unfamiliar situation that developed rapidly, and tried to cope as best as possible.
The rest of us can take note and learn....

OSCAR
Let's examine your suggestion. The aircraft was in ALTCRZ in which it is linked to Altitude in Alt window and when disturbed from it will try to get back to it by climbing or descending while VS0 is not linked to any altitude but V/S zero. If disturbed by updraft as was the case AC will deviate and try to maintain VS0 where ever it stabilises. So it is less aggressive. But in the present situation when the ALT mode is unable to prevent climb or descend changing to VS mode will cause larger deviations. Yes it may give you better ride because it accepts deviations. I don't see any magic solution in VS0. The pilot applied the correct procedure but may be he could have left the AP on till it disconnected on its own. It may have handled it better but not VS0.

Villas
If you read the article, the aircraft was in OPEN CLIMB.
"The aircraft climbed through FL373 when the first officer noticed the speed had increased to 0.81 mach and had engaged in a 3000 fpm climb, the speed trend indicator suggesting the aircraft would accelerate beyond the maximum mach number operating (MMO) of 0.82 mach."

In open climb, the aircraft attempts to maintain speed by adjusting pitch to change the V/S. 3,000 fpm with only 700 feet to go is excessive. Pushing V/S zero will change the auto thrust to speed control. Once the aircraft is under control again, a gentle climb rate of say 500 fpm using V/S would be sensible.

Why do you not like using V/S 0?

My Lord I'm glad I don't fly an airbus, I don't understand half of what you guys just said. ( I've always been a bit slow though).

Goldenrivett
The initial part of the news seemed to suggest aircraft was at ALT. However you are right the AC was in OP CLB. My comments were for ALT mode. I don't have anything against VS0 mode rather in RVSM I thought everybody uses it in last few thousand feet to reduce ROC to avoid nuisance TA/RA. Just to recap the event the AC was climbing through FL373 to FL380 when he noticed the speed .81M and ROC 3000 and went to select Mach of .76. It is not clear if ALT* was engaged. If it was not the ROC would further increase to bring the speed back. Anyway with only 700 feet to go the SPEED ALT* should have engaged. At this point he disconnected the ATHR by bringing it to idle and also applied speed brakes. So by now he had done everything that should have been done. By selecting VS0 nothing more would have been achieved because the thrust was idle and FG in ALT capture mode. If the AP was kept engaged the problem should have settled. The workload increase was due to AP disconnection. If speed brake was in full position with AP ON the disconnection of the AP could cause the speed brakes to extend full from half. This would increase the VLS and the drag leading to alpha floor.

@vilas.

You're not paying attention mate.

Does not matter whether a/c was in ALT* or not, by hitting VS0, you "break" the ALT* mode.
(Hence my comment "that you might have to press VS0 a few times because it will inevitably go into ALT* again with 3000ft/min ROC and 700' to go.)

No need for speed brake, or A/THR disconnection, if you just go VS0 and select speed .76. :ok:

And as for the comments of reducing ROC before level off, it is only rarely necessary above FL350,
and I think you will struggle to find any operator recommending the routine use of V/S mode at those levels irrespective of aircraft type....

Hi OSCAR YANKEE
SKYbrary - Rate of climb within last 1000 ft before cleared level
"many operators have standard operating procedures requiring the pilots to reduce rate of climb/descent to less than 1500 ft/min when in RVSM airspace or within the last 1000 ft before cleared level;"

You'll be one of those giving me the heart attack as I wonder if you'll ever level off approaching me! The automatics always do stupid things - they can't think, so please reduce your rate of closure.

OSCAR YANKEE
Oscar I am paying full attention. ALT* surely matters because ATHR would go to speed mode and in this situation it should go idle. He had already selected .76M and without ALT* that would have only increased the ROC to reduce speed. Coming to your point why do you want VS0 is to get ATHR in speed mode to bring the speed back and stop climb but when the guy has brought the thrust to idle with speed brakes and still the aircraft tends to over speed how VS0 would have helped? However had he left the AP on aircraft should have levelled out and he would have had more time to pay attention to adjust thrust manually or put it in auto. He followed the correct procedure except that there was no need to disconnect AP because had the over speed continued the AP would have tripped by HSP activation and then in any case you take over manually but at least give it a chance.

Maybe im not explicit enough......
I wrote:

I know the recommendation as well as anyone, but tell me the last time you had to intervene to reduce the ROC above FL350 ??

Maybe the A/C I have flown have been underpowered, I dont know.......

As the example above - high ROC above FL350, will "normally" only happen in empty A/C or if you get a WS type scenario.


@Vilas.

All im trying to say is no A/C can defy the laws of physics, no matter how advanced the A/P. Sometimes it needs a bit of help.....

And as I said in my first post.
I have had the good fortune of reading quite a few safety reports (incl. FDR read outs) similar to the one above from Avherald - and my personal opinion remains - you are better off leaving the A/THR + A/P in and take a minor overspeed, than ending up in the mess as described above.

Follow the official procedure, and you might end up one day with the "Successfull operation - but the patient died"-scenario......