View Full Version : Limitations on special Boeing 737-800 series

24th Aug 2006, 14:12
Good afternoon,

since days I observe a lot of Boeing 737-800 series deviating from their requested level by 2000/4000ft. RFL ist very often 370/390 or 380/400. The flights are conducted istead at 330/350 or 340/360.
Questions led to the short notice, that is due an advice from Boeing and because of stall buffet margin.
Has got anyone an idea what the exact reason is and If its insisted to change this by modification?

Thans very much indeed and happy landings...

24th Aug 2006, 23:05
I can only assume you are talking about Ryanair. There is a temporary company restriction in place issued by the Chief Pilot that we must ensure a Buffet manoeuvre margin of at least 1.5G which is in contrast to our previous of (I think) 1.3G, due to occurences in flight which are still under investigation we are told. This results in cruise levels of as low as 330 when we are heavier.

25th Aug 2006, 07:40
Its 1.45G buffermargin since yesterday, so now we can climb 200ft ;)

25th Aug 2006, 07:56
wow! do you guys get paid extra for being test pilots

25th Aug 2006, 08:03
What is unique about RYR B738's? I believe the FAA allow 1.3. Years ago the UK CAA had a 1.5 recommendation, but I believe the company asked for a 1.3allowance on their B732's, and got it. What is the JAA thinking on this? and what do they limit the FMC advice to considering Max FL? i.e the FMC programming.
Whatever; have any other operators had this restriction, and what prompted it? Surely it should be a type restriction not a company fleet matter.

25th Aug 2006, 08:34
Story I heard was that it is a Boeing decision due to "production problems" on the B737 over the last few years .

25th Aug 2006, 09:29
I fly the -800 as well. manufuctured over the last years...
Never heard of such a restriction. We operate up to 1.3G margin as usual. (with or without winglets)



25th Aug 2006, 09:48
RAT5 , Like I said:

temporary company restriction

occurences in flight which are still under investigation


25th Aug 2006, 11:03

I don't want to get into any slanging match: you said, he said. I did very well RTFP, but

You started with " I assume you are talking about RYR.....". Just because your CP has issued a temporary company restriction does not mean that other C.P's have not done the same. Equally "....due to occurances in flight..". does not necessarily mean that it was to a RYR a/c. You may know it was, but it was not clear. If you do know, please enlighten the rest of us.

It is still an interesting question, if indeed it is purely a RYR fleet restriction, as to what is so different about the RYR operation compared to others. Surely your CP would have informed the crews as to the back ground of this issue. I would have thought it wise to keep all informed about such a rather drastic operational limitation. After all, trundling along at FL330 wondering what has gone wrong before at higher levels can make someone nervous. At least when the fixed flap speed schedule speed increase for F5 was applied on earlier B737's everyone knew why and thus understood. Admittedly that was worldwide fleet issue, but then why is this not one?
If Zed 3 is correct it should affect more than RYR. By the way; have RYR altered their Plogs for the increased fuel burn. It would seem from R.R. that the lower levels are a surprise to ATC. This would suggest that the RFPL's are still being filed at higher levels.

25th Aug 2006, 11:49
Okay thanks anyone giving exact information here!

Thats nice to know for ATC for capacity planning. Changing RFPLs is a matter of time, we understand, and we know that its intended to change all RFLs accordingly.
But the "problem" is another one. Since we are working some areas, where traffic is very dense and by nature limited in performance (e.g. joining routes over FFM to the Southeast) we as controllers appreciate the performance of the 737NG since they are almost no problem in handling at any time. Now since several flights are conducted lower there is a conflict of more flights within dense flown levels.
The interest came just because of our observation and if something is intended to be changed. But we do understand the facts and appreciate safety culture like that.
Anyhow It would be much more helfpul if departing traffic advices the "real" RFL on intial contact to avoid unnecessary conflicts. But this is not a problem with the 737-800 fleet, this is a general one.
Best cooperation and a lot of thanks to the BA-fleet, they always want their RFLs as inserted in the FPL or they advice accordingly on initial contact any change.
Okay people, so far thanks to anybody, I will watch If there are some further comments within the following days. Have a nice weekend and always happy landings


25th Aug 2006, 12:12
RAT5, I was reffering to your comment "What is unique about RYR 738"

There is a background, but I was trying to just asnwer RRs question. Otherwise these FR threads descend into chaos, and I don't want to break the PPRuNe "FCI" of discussing or questioning FR and safety in the same sentence lest FR start sending angry solicitors letters again.

25th Aug 2006, 12:16
RR, I sympathise with your problem. The problem is that what appears on our flight plans is not always what the controller has in front of him/her as the filed level. Some controllers in the Swiss sectors have reacted with a little anger at this and leave us at a low level, 290 for example as thats what we are filed at. I believe that some levels are "tactically" planned off optimum to avoid slots. That this new restriction is not reflected in our filed levels is a little dissapointing to us too!

FCS Explorer
25th Aug 2006, 12:35
- RFL is based on assumed TO-weight by dispatchers. more extra-fuel or pax or cargo -> higher gross weight -> lower level

or: running late, flying fast (M.8) -> unable for higher level which would have been good for M.78/.79

or: crew wants more buffet margin, maybe due to expected turbulence. 738 fmc gives you info about optimum and max LVL (in hundreds of feet) for act weight and desired speed. e.g. opt: 368 max: 381
now u could go up to FL380. but the red bars on the speed tape will get VERY close to your speed bug from both sides. one bad bump and you can't hold altitude anymore. plus your climb performance is pretty miserable.

or: radiation: crews don't feel the need to fly in FL400

25th Aug 2006, 14:56
Good afternoon FCS-explorer,

thank you very much for the detailed information, anyhow we are not talking about these facts. Actually we are talking about hundreds of flights per day remaning well below RFL because of internal needs.
If we as ATC know about the needs of our customers we are able to react in a professionell manner and to provide the best service we can.
This is not the first time we deal with the problem, but obviously there are flight crews, that are able to advice different RFLs on contact.
And to be honest, we are trying to be any day as good as we can, but if there are some serious changes, we dont know, it will have a large impact on the service level.
And Im on the cockpit side with the argue, that to keep flights well below dense levels as a reaction on the problem, is not the best idea with the present kerosine prices.
An early advice of the crew what the planned cruise level is, is the opportunity for us to plan the flight from the early stage to the expected level and to adjust any need to a common sense.

Folks, thanks very much so far and have a nice weekend


FCS Explorer
25th Aug 2006, 15:27
morsche Rhein-radar
if u need to know the level early, have the previous sector ask for it (:ugh: gee, just another smart a** answer from the flight deck!). or even better, as done in some places: the crew advises RFL when obatining start-up.

enjoy your W.E.

25th Aug 2006, 17:53

If this problem is only a RYR one, and you want to know more, why not ask your managers, on behalf of all Euro control, to ask RYR what is going on. If it is causing you a problem then include a suggestion to solve it.

However, we still haven't had a definite answer if the is a RYR limitation or a type one. Are there any other operators in the same boat?

25th Aug 2006, 19:12
We have not been told that it affects all -800 operators. It was not a technical bulletin. I am assuming it only applies to our Airline.

25th Aug 2006, 21:12
i think flying higher with the reduced buffet margin is and has been a less than perfect technique...I know about fuel consumption, routings and all that but having seen pictures of turbulence encounters (CAT) I think taking a giant step backwards from the edge is in order. I know nothing of ryanair, but is this as a result of the recent russian plane crash?

perhaps ryanair had an inflight upset which has stayed out of the news...if this is the response I think it is the proper one.

icarus learned that flying too high can be a bummer.


25th Aug 2006, 22:58
Let me see if I can get this right.
FR used to fly with a 1,3g stall margin
Then, a little while ago that was changed by FCI to a 1,5g stall margin.
As of yesterday that was changed again to a 1,45 stall margin.
In effect this means that most FR flights now wants to fly at 350 and 360, instead of the usual 370 and 380. Note that most FR flights are flown at very similar weights.
I do not think all standard flight-plans have been changed to reflect this. (those flights actually filed, and flown at those higher levels.)

I understand that FAA registered aircrafts are normally allowed to fly at 1,2g stall margin and the normal limit for JAA operators is 1,3g. Am I correct in this?
One last thing is that with winglets the optimum and maximum levels are much closer than with the standard wing, leaving less of a buffer zone. :hmm:

26th Aug 2006, 17:30
Of course the Flight-plans haven't been changed,otherwise someone would have to tell Big Micky that we are wasting all the benefit of those snazzy bent wings. Perhaps if someone had mentioned to the chaps driving that 4 percent extra N1 was available in the cruise by line selecting CON as the limit on the N1 page we might not need to fall out the sky in the first place(this is only a rumour, but I guess it could help if our "woopsy" was a low speed variety) but hell i'm only a simple line pilot, and not the calibre of guy who lambasts the engineers for not being able to clean my polaroid glasses induced stress lines off the windscreen (alledgedly).Think you will find the non wingleted aircraft at same levels as before, and the bent-wings 2 grand lower, as prev poster said optimum and max for these were a little too close ( never did feel very sensible did it? )

26th Aug 2006, 18:29
I can only remember the outline details - old age. But there used to be a significant difference between UK registered 744s and US registered ones because of CAA/FAA differences. This may read across to the 737. It all revolves around cruise Center/Centre of Gravity and different certified turbulence max g. The FAA takes an average c of g case whereby the CAA takes actual input into the FMC. In addtion the FAA limit was I believe 1.2 g whereas the CAA equivalent was 1.3g. This results in different max altitude displayed calculations on aircraft Flight Management Computers depending on how they are configured and to which rules.

28th Aug 2006, 02:12
...there have been several incidents regarding buffet alert bla bla bla....
could be possible that during FMC programing the temperature expected at a certain FL has not be put correctly or not at all? Dunno why 738 FMC do not make this entry mandatory. The fact is that if it is not entered, the FMC will assume standard temperature making it -61 at FL 380 . This never happens most of the time as we are at ISA +10 to + 15 depending on the place on earth you are flying and in what season. Not entering the correct temp you will get on the CRZ page OPT/MAX maybe 365/382 but once you enter the correct data...SURPRICE!! On the 744 this entry is mandatory FMC has boxes and not dashes as on the 738 FMC. Summer season has been specially hot this year. Here in Asia we had some times ISA + 20 over Japan airspace.
Hope this helps... if not we have to call Spiderman to solve the mystery
Happy landings...

28th Aug 2006, 02:19
the limits set by the authorities should be programed into the FMC software. This is made by maintenance . It is factored into the equation . Now the pilot needs to put reasonable numbers in. What ever the limit is don't make a difference to the computer if the input data is correct. You will get the correct data displayed on your PFD Speed tape. You cannot go that high:=
B good

28th Aug 2006, 08:19
BA 757s always used to have a lower "Max FL" than FMC due CAA v FAA diffs, or even the whim of one BA Fleet Manager - we had a chart on the back of the FMC reflecting the Max FL we were to use (as above, increased buffet margin).
Bear in mind that the RFL is likely determind by a (bought in?) piece of software - costly and time consuming to alter. Changing Max FL by CP dictat can be achieved overnight, and tweaked (as here, 1.5g to 1.45g) by immediate experience even ATC feedback....
Someone speaks well of BA and RFL, but we often "tanker" fuel (especially post Buncefield) that is not on our Flight Plan, hence lower Max / RFL. Believe it caused some problems, especially ex USA, in the early days with Atlantic crossings all at lower levels than filed...
Only solution I can really see is better comms / heads up... ATC asking / crews advising early when RFL is not as filed...

28th Aug 2006, 14:07
VonLuffers, you said:

...the FMC will assume standard temperature making it -61 at FL 380

ISA temperature lapse is down to -56 degrees at 35000 ft and thereafter a constant -56 degrees in the Stratosphere......(approx).


Of interest, one of the pin selectable parameters for the FMC is whether FAA or CAA rules are applied. You can trawl through the maintainance pages and find what it is currently set to......

28th Aug 2006, 14:26
Hi Bus:
You are right, but dunno if that is what really happens with the FMC software( I'm not that smart nor stop to review my AOM that often and in detail :p ) Never mind, -56 assumed by the computer instead of an actual number of lets say -48 -50 what ever may be can be the difference between being at the operating envelope or out of it.

29th Aug 2006, 11:31
Too true.

A few weeks ago I saw ISA +15 temperatures at TOC here in Europe - very unusual, but a very real effect on performance. It lowered our ceiling by several thousand feet.

Even with the FMC not given a TOC temperature or deviation, as the aircraft climbs it will recognise the impending situation and issue a buffet alert. Or does that mean its time for a snack?

29th Aug 2006, 15:44
Was/is it not the case that UK CAA (not sure about new fangled JAA) had the FMC default to max forward C.G for crz? Some airlines were not allowed to alter this as a safety margin. Now we can put in the actual C.G.
What I do find disappointing is that the crews have so little data about how the FMC is calculating the info upon which they operate the flight. Surely it would be a simple matter to have a crew notice in the tech log; indeed should it not be the case: 1.3g or whatever, and at what Cof G. 21st century, high tech fancy equipment and so little information. When there is an accident/incident in a new all bells & whistles a/c, one of the often mentioned items is how much crews are becoming divorced from their a/c by all the automatics. This can only be worsened by keeping them in the dark about WHY it is producing some information. FMC data is often guidance, but how do you know to trust it if you don't know how it arrived at its advise?

have another coffee
30th Aug 2006, 15:50
Weight is an important factor in calculating max FL's. As there is reference to Ryanair I wonder which standard weights they use after their change of policy regarding hand/hold luggage.
A rough estimate:

Operator's are allowed to use 84 kg (charter flights even a lower 78!) if no male/female distinction can be made. Standard luggage weights may be as low as 13 kg a piece if no actuals weights are available. Make a rough calculation for yourself how much a full loaded -800 (186/189 pax) can be off actual weights if these figures are used.....

Try and add 3 ton to your actual weight if at FL 360/370 and see how much MAX ALT changes :sad:

This is not intended for Ryanair bashing, just for awareness :ok:

p.s. Note the blocked red line on the speed tape. Try to stay in the black area between the red blocks. You should be safe there :E

1st Sep 2006, 07:36
Is the limitation lifted by now? I saw a couple of RYRs climbing to 370 this morning...

1st Sep 2006, 08:04
They might have been very light, less then a 100 pax you can make that. There are many Captains who choose to ignore the advice of theri Chief Pilots also.

1st Sep 2006, 13:37
"There are many Captains who choose to ignore the advice of their Chief Pilot, also."

And what is the F/O doing in the meantime? It would be THE CREW having tea no bisciuts in the head master's study if owt happened. I thought RYR had a strong CRM review recently after a few captains did certain strange manoeuvres.

1st Sep 2006, 14:50
RAT 5. What can you do. I made my opinion known to the Captain in the crewroom. He or she stated that this was a knee jerk FCI, he/she had flown this aircraft for a long time and knew it was unessecary. I argued that it was an FCI and not open for interpretation. I said I felt extremely uncomfortable breaking it and did not want to do it. That was him/her pissed off and not talking to me in a conversational sense for the rest of a very long duty day. What else can I do apart from wrestling the controls off him? Refuse to fly? You've obviously never heard of Cliodhna Duggan then have you? :



www.bugmenot.com for the passwords.

1st Sep 2006, 17:42

I apologise; there was nothing personal intended. You have my sympathy. It sems a rather unnecessary reaction. Perhaps a soft suggestion that there is less radiation lower down and thus the macho captain might benefit in the long run? I haven't heard of the erstwhile C. Duggan. Is there a relevant story, without going off thread?

Meanwhile, there has been no information here about why only RYR have imposed this restriction. The whole NG community is waiting & wondering what the hell is going on & why.

1st Sep 2006, 23:35
RAT5, The memo we recieved is that there were a series of "high altitude upsets". The rumour mill has even suggested an approach to stall or stall itself. These are under investigation we are tld and until it has been resolved we have been instructed to fly at a lower level. I have my own theories and have heard certain stories, but as I recall there was an order from the owner of this site not to discuss certain isues about a certain airline due to legal hassles.

2nd Sep 2006, 07:20
Do FR Pilots load the correct T/O Mac into the FMC on the Perf Init page on the FMC?
On our fleet of 800`s, this automatically defaults to 5.0% and this can make quiet a difference to speed margins at Altitude, and obviously Max and Optimum levels.

2nd Sep 2006, 07:51
Guttentag Rhein Rader wie geht's, I am also one of the pilots that is often requesting a lower level in stead of flying the filed Flightlevel. In our company the flightplans are generated by LIDO and since we are now flying with winglets, the optimum flightlevels are more or less the maximum flight levels if we would follow FMC predictions. The problem is that everything what is filed, is based on weight and balance assumptions and unfortunately these assumptions are often wrong. In many cases we are a lot heavier than predicted and also the weight distribution is different. Let alone that the computer is calculating ISA atmospheric circumstances. Which are often not the case. Especially in july it was a lot hotter than standard in Europe. Last but not least the computer generated flight plan does not take in to account CAT or turbulence from TS, where I do in order not to fly in the ''coffin-corner'' while more than light turbulence can be expected.

Danke und viel spass,

2nd Sep 2006, 20:04

Thanks for the links to the court case you quote. That young lady obviously had more ba*ls than most male pilots I've met. I wish her well in her future career and from everything we hear about that company, isn't she better off out of Ryanair wherever she now is.

4th Sep 2006, 03:38
Think you will find the non wingleted aircraft at same levels as before, and the bent-wings 2 grand lower, as prev poster said optimum and max for these were a little too close ( never did feel very sensible did it? )

We were told FMC data would show increased optimum altitude performance data for the newer wingletted 757's. Also told that max altitude data would not change.

Did max altitude of the a/c actually improve? Yes. How much? Unknown. The company that produces the winglets did not too the high altitude buffet margin testing to produce higher max altitude data.

FMC shows increased optimum altitude capability. Max altitude is the old, but only, data available.

4th Sep 2006, 03:42
Forgot to mention - 757 max alt is typically 3500' above optimum. You can check it by putting FL420 for a crz altitude on the crz page and then clearing the 'check cruise altitude' prompt that appears. FMC will shortly display max altitude on the scratch pad (typing line - 6L).

With winglets it should be around a 2000-2500' difference between opt alt and max alt.

Few Cloudy
4th Sep 2006, 14:59
1. If Ryan change their procedures and the poor ATC guys have to ask here what is going on - then Ryan's coord. with its partner bodies is poor.

2. Tongue in cheek, in case someone comments - you can keep 1.5 margin by flying straight and level innit?


5th Sep 2006, 15:35
Hi everybody!

I have been told by RYR management that this is due to a quite unusual incident:
A RYR B738 flying FL360 next to or on top of a thunderstorm encountered some turbulences. At the same time OAT was increasing (ISA + 20C), maybe due to the convection of the CB, and they started to pick up ice on the wings (very unusual at this level) :suspect: . Then they were unable to maintain the speed with full thrust and asked for emergency descend. Hopefully, the crew saw it coming and the stall was just avoided. :ok:

Lets wait & see the official report!

Nevertheless, when I did my transition from the 737 classic to the NG, I was quite impressed by the fact that the 738 has difficulties to regain the speed when it is lost at high altitude (in climb or level flight) and it also has significant less margin concerning the high speed buffer (apparently, if you overshoot the Vmo/Mmo limit, you are not going to stall the airplane immediately because the first restriction is the airflow around the stabilizer).

Any comments ??

15th Sep 2006, 18:17
anyone have any more news on this subject? has the problem been solved ?

Jambo Buana
18th Sep 2006, 14:52
Re-checked is quite right about the incident. Also a factor was the crews selection of WAI which automatically adjusted the margin to stall. OFDM is a great tool, and is being used in FR by the CP in a very responsible way. I believe we are trying to get boeing to remove the WAI Vs feature above a certain FL.

ps Carmoisine, you need to evaluate your own lack of performance by allowing a Captain to operate outside of sops without filing a report! Your situation is not like Cliodhnas.

20th Sep 2006, 00:22
Cliodna Duggan was an FO in Ryanair who was sacked for leaving an aircraft after a disagreement with a Captain whom she alleged in court had both verbally and physically abused her. He disconnected the autopilot a number of times without telling her (she was PF) during an instrument approach into Prestwick. It later transpired that this same individual had done the same to a number of other co-pilots, none of whom had reported it to anyone. She was sacked after a typical Ryanair 'kangaroo court'. She then took a High Court action against FR which was settled after about an hour on the floor of the court because FR couldn't afford to have the full story come out in open court. FR agreed in the settlement that she had "acted in the best interests of flight safety, and of Ryanair and its passengers". However, she remained sacked and that is the real issue. The chairman of the local IALPA branch, Martin Duffy, had been sacked a week previously after a similar FR "hearing", for allegedly refusing to position to STN in a jumpseat. Her father, who was the Chief Pilot at the time, departed FR shortly afterwards. The message went out loud and clear to all pilots - do what you're told in this company or else.

It is this type of response that has determined the "safety culture" in Ryanair. The whole aviation world is aware of it but nobody, including the IAA and the UK CAA, seems prepared to do anything about it except for the remarkable Capt John Goss. The other good ones just leave for Emirates etc which is exactly what MOL wants.

19th Oct 2006, 20:21
The restriction has now been lifted. So we might even dare go all the way up to 410 again..............

20th Oct 2006, 13:45
Or no buffet margin at all! The number of times you hear the clackers going off in the background on the r/t from FR is shocking.

late developer
23rd Oct 2006, 13:22
What's going on here?

I haven't read this thread before but got just halfway through it before I thought "I wonder if this has to do with being much heavier than the sheet".

Are some here talking about coffin corner? Or something similar where margins for safe resolution tend to zero? I sincerely hope not.

I mentioned in another thread how I reckon I have been personally responsible for 140kg on a flight when the sheet probably only says 100 total for me.

I've seen some of these flights are almost completely full. Isn't that maybe 189 pax? I'm tall but not obese, but a hell of a lot of passengers are thesedays, and some on every flight seem to be moving half their houses right up the steps into the cabin (the other half being in the hold we presume).

Last night I overheard some regular golfer pax talking about inconsistency in charging for excess baggage. Sometimes charged, sometimes not they agreed. They called it pot luck.

1. Forget the hand baggage for a moment (but note it is still relatively easy to board with 20 kg).

2. What is the authorised average weight plotted per passenger with the low cost high load factor models we are talking about? I recall that some authorised models used to assume just 65kg.

3. I'd now like to know how the exact total baggage weight checked in please (via normal channel and fragile) is reflected on the dispatcher's load sheet. Unlike with some airlines, there was no weight shown on my luggage tag last week. In the authorised models is there an average assumed per bag if it isn't charged as excess?

Could someone enlighten us generalists as to what's going on?

late developer
23rd Oct 2006, 20:14
Well forgive my impatience but I'll start answering some of my own questions - yes we are talking about coffin corner and yes weight is a very significant factor, isn't it? I see "have another coffee" long ago answered my question about questionability of using standard pax and baggage weights on loadsheets.

Now then, which one of you practising low cost PPs is going to tell me how you or the FMC really knows the exact weight of your aircraft before or after you sign the load sheet thesedays, say to the nearest 10%?

Or maybe a different question - if you add up the 'lost' 40 kg per passenger that I said might apply when me and my 188 2006-sized mates fly what difference might that make? Oh ... thats the same thing ... deary me!

So how much difference might 7 tonnes make to the manoeuvre margins at FL410 if we inadvertently plan no more than the theoretical max allowed up there on the day and head straight up there without knowing we are carrying all the extra?

I see that "have another coffee" reckons 3 tonnes is enough to make a significant difference. Maybe that's roughly where his 3 tonnes comes from. You can't plan to go to FL410 with more than about half load of pax and their bags? I was multiplying 189x40kg. Take 100x30kg as unrecorded extra load and maybe that's pretty close to what you PPs actually encounter?

Never mind the theory - how do you PPs actually know when you actually are up in that corner. You get warnings I assume triggered by some of the parameters you may incorrectly have programmed into the FMC? What safe ways out are there if you do actually stall or get some warning of onset? Is there some kind of physical high speed buffet/low speed buffet convergence stall warning system that actually picks up the physical condition at the wing irrespective of how incorrect the load data was?

I thought high altitude stalls were extremely dangerous?? Or are they no big deal anymore?

Jambo Buana
23rd Oct 2006, 22:23
Why are you directing your questions at the LCCs? They are ruled by the JAA just like any other airline. You do have a point but tell me what do other more respectable airlines do then?

late developer
24th Oct 2006, 07:16
Why are you directing your questions at the LCCs? They are ruled by the JAA just like any other airline. You do have a point but tell me what do other more respectable airlines do then?Ehm pardon? It may have escaped your attention, but not mine, that all significant airlines are now LCCs and respectability became a myth when Quantas lost that tag somewhere along the way. So then, for the avoidance of doubt, would ANY PP like to comment in detail about what exactly goes on in the office on this subject. I would particularly like to hear from 737-800 pilots because I happen to risk my life in them far more than other types and by no coincidence, that seems to be the type in question in this thread.

Jambo Buana
24th Oct 2006, 08:55
Okay I fly the 800 for Ryanair. You are right that some pax carry more than their fair share of extra weight, be it on their bodies or in the overhead lockers or in the holds. Equally though there are many walk ons with no extra weight. In RYR we use 80 kgs per adult pax which is a good average between male and female, children are 30kgs and infants nil.
Now where you do have a point is when the balance is not equal and that all pax are male carrying the kitchen sink into the airplane. The male bit cant be changed or altered but the kitchen sink is primarily the airports/checkins responsibility backed up by our cabin crew who regularly redirect things into the hold.
For your peace of mind after 13 years in low cost, I have never had an all male pax load, and that if I ever expect the a/c is overloaded or misloaded then I check fuel flow which we can do for the specific weight down to the nearest kilo from the onboard QRH. I havent found a problem with weight yet except for mistakes on loadsheets.
The BMI accident was one of the first to teach us not to overfill the hat bins as when you do a lot of people loose the top of their heads!! So it is an industry problem in general to try and reduce hand luggage, and you do have a point. Also the cabin crew are in such a rush normally that these issues can sometimes be overlooked, but on the other hand the RYR policy of charging for excess baggage at checkin means the eagle eyed check in staff, who are on bonuses for their extra baggage spotted, probably offsets the cabin crew.
Overall it seems to work, which is the main thing!

late developer
24th Oct 2006, 16:39
JB, I am really pleased you have engaged with my amateur attempts at queries on this. Thank you very much indeed for your candid response.
I hear what you say. It's a long time since I worked back from a graph of fuel flows to obtain an accurate weight. The Quick Reference Handbook is exactly that, a quick reference, and I am left wondering what inbuilt errors there may be if you are in the climb at some lower level, potentially loaded/trimmed not quite as ideally as you planned, working back your fuel flow observations on a QRH graph of climb performance which might not take into account all the variables of the actual (partially unknown) configuration.
Meantime, with your commercial manager's hat on (and I accept that you are expected to be commercial on behalf of your employer) you are continually re-evaluating whether you will soon be able re-confirm to ATC that you still want that planned FL410 or are going to have to ask for another level. Is that generally how it goes in the office ten minutes after take-off?
So you make several re-evaluations of your weight as you traject up through the troposphere relying upon Boeing's graphs and your winglet manufacturer's modified graphs to give you hard data about your likely weight to the nearest kilo (using standard assumptions) plus of course your load sheet and all the other pilot observations you have made since the last time you knew it had no load and an exact known quantity of fuel. Right so far?
Let me rewind a bit. Never mind the full on FL410 - lower levels can still be problematica, eh? You have a turnaround time of 25 minutes - you achieve less sometimes. You started the inbound late. It's night. You've had great tailwinds on the inbound. You made up some of the delay you've been carrying since fog this morning. It's snowing here and runway clearance have been working non-stop tonight and the moment you landed they were back out there to keep it clear for the outbound. You must be working like Trojans behind that door if the runway conditions are marginal, the outbound load is high and you have not burned off as much inbound fuel as you had hoped because you had tailwinds. It was only an hours flight. Your employer wants you to tank some fuel too if you can. So
1. are you sure you can still take-off on this runway with the heavy pax load in their heavy coats with goodness knows extra weight hidden underneath, and in their pockets, already at the gate and their bags already being loaded?
2. can you still plan to get above those headwinds going back? Where in or above the Tropopause (forgive me I've forgotten if its a line or a zone!) will you find the fastest track now? Is it pushing performance?
3. The destination runway closes at 00:00hrs Local. (Oh that old chestnut!)
4. Despite the headwinds you think you can still get back before it closes.
5. What are your diversion planning obligations? You know it is 50/50 that your destination will now not be operational when you get back. More fuel? Are you really sure you still allowed to excecute a flight plan to this destination with what you know right now? Or must you plan for another destination and another divert?
6. If you execute a plan for high altitude the numbers say you are still legal for the original destination. Which flight level was that?
7. More fuel?
8. The refueller has gone and the dispatcher has asked you to sign.
9. Doors closed. Time to go.
10. The runway crew have done a magnificent job. It's very white but it's clear. The braking efficiency check they've just done is marginal but ok. Another couple of tonnes and it wouldn't have been. But this is a military installation - it's long. You go.
A full 35 seconds from full power to rotate, despite the dense air.
Now you are in the climb. How heavy are you? I mean really?
How are we doing? Not so hot. They've routed us direct across this part. Great. But we really need that high level. Gonna be bumpy up there. Wish we were lighter and could go higher still. What are we using today? 1.25, 1.3, 1.5, 1.45?
How heavy now? Where's the right QRH chart?
15 minutes since airborne and still 50/50 we will get in before 00:00 if we go high. There'll be a hold when we get there. Bound to be if we are one of the stragglers in the usual 2300 to 2330 flock coming home to roost and bed. Everybody's been running late since this morning. How much fuel did we got?
Fuel flow? QRH says how heavy now?
Safe to go up there using 1.3 today? How rough is that air at that level tonight?
Do we got good data programmed in for everything else?
We do? Fuel flow again. How heavy are we? I mean really?
And that gives us what margins up there?
OK looks tight but looks good.
OK ... they are clearing us now for climb to that level. We'll take it? We'll take it.
JB I may have it all wrong. Maybe I should have chosen a hot example not a cold one?:O But is any of my imagination run riot as above about right?
I really don't know what the risk is. That's why I have asked. I'd like to know. I watched TopGun a few times. Out of the envelope and it's curtains for Goose and the airframe, eh? F14s in combat is one extreme. But just how much of an upset can you 738 drivers imagine with the typical errors we've been discussing? Maybe it'd just be a walk in the park?
Say those numbers were still a bit wrong despite your worked-back-from fuel flow QRH plotting. It's bumpy up there but you can still read the graphs and maybe it's not too bad. So when the onset of an upset occurs, it's a surprise. What's the first sign of an upset in the corner? Is it the clackers someone mentioned? What do you do? Get on the radio and ask for a descent? Or descend immediately whilst your co-pilot immediately radios an emergency descent? I really would like to know.
I have read about 12 knot margins between high speed and low speed buffet. That sounds so thin but I guess an autopilot can nail it. I have read here that speed lost at high altitude in a 738 is hard to regain as if that is a good thing, but if are just about to unexpectedly drop out behind the low speed curve and you want faster to get back in the envelope then surely that 738 characteristic's a bad thing if you can't get what you need?
You have a relatively new wing, don't you? You have winglets. You have QRH with some winglet data and some no-winglet Boeing data. I've seen one PP asking others "Are you test pilots?"
I have read on PPrune about incidence of 1.6g to -0.02g in 2 seconds (slightly lower altitudes I guess).
Combine something like that with a typical error in weights and a 12 knot buffer zone then what kind of upset are we talking about? Again, I'd just like to know what I am up for when I pay BAA £39 to park, and my airline £7 including tax each way. That sounds a kinda crazy way to run a railway to most people, so much so that they run lemming-like to the web site daily and then do the most creative things to avoid the £39 which is nuts and spend hours researching how maybe they can save £4 by booking in advance or even handing the keys to a local entrepeneur who will park it securely at some roadside in Bishops Stortford! If only they knew, eh?

I am sure if most people really understood how high and low speed buffet was managed last week, and then compared it to this week and then compared that to South West, they'd think that was all kinda crazy too! Some might say FL390 is crazy, FL410 is nuts, but I don't mind FL350. Maybe some might even lobby for some extra breathing space and airspace and R&R for guys like yourself, JB!
I just had a crazy idea (another one!) for a subtle variation of the oleo model.
It goes something like this:
When we book online we should be asked to select from three extra dropdown boxes:
(i) what error in loadsheet take-off weight we are prepared to accept (+-2%, +-5%, +-10%) and
(ii) what high altitude manoeuvre (buffer?) zone (min 12kts, min 50kts, min 100kts) and
(iii) what manoeuvre load factor (1.3, 1.45, 1.5)
then receive a price accordingly. Afterall, we can't buy proper smoking hole insurance without disclosing on a scale of 1 to 10 how risk averse we are:p
It would mean that if the scaredy cats booked early they'd probably get whacked with a big price, eh?;) And if they nevertheless paid that price then in order to accommodate them all the golfers and skiers on the flight would get their excess bags weighed and charged big time:D

24th Oct 2006, 18:48
late developer, chill out man , sit back relax and buy a few of our bulls-eye baggies and fill yerself full of booze from a plastic bag. Incidentally has anyone worked out why we now use 10 degrees of bank above F300 in HDG SEL but we are allowed to let LNAV command 30 or whatever ? I guess the aircraft can't stall in LNAV . . .Duh ? Incidentaly, when you are using 10 degrees. . .well you are aren't you ? be very careful when given heading changes over France. My experience so far suggests that they expect us to turn a bit quicker than we now do if we are to maintain normal seperation. All in all, think I prefer a bit of buffet to a RA.

Jambo Buana
25th Oct 2006, 17:10
So who says we are just glorified bus drivers?

Your perspective as an amateur is rather too well informed me thinks?:cool:

I will try and reassure you with regards to some of your points, but it will be short as I have to fly.

Your scenario is extremely realistic when compared to some of the LOFT ( Line oriented flight training) that we run every 6 months in the simulator; Marginal contaminated runway takeoffs/landings, minimum legal fuel dispatch, closed or closing airfields, pushy dispatchers, unforecast weather leading to enroute diversions (into nasty little airfields), jet upsets and high altitude engine failure, medical emergencies, crew incapacitiation etc etc are all practised regularly.

All your `what if` scenarios are pretty well covered IMHO and when you go down to the wire on certain things like performance you must remember that it is not an exact science so the regualtors build in margins for exactly your type of worries, overloaded, poor crew reaction time, Friday airplane etc.

But to cut it short as I really have to go, if I thought my airplane was too heavy for the phase and position of flight I would simply add a couple of tons to the FMC whilst we worked out where the mistake was made. Normally the dispatcher can be contacted and if he has stuck on a few tons in the aft hold without telling us, then we can get back to business. What you may not be able to appreciate is that unlike a fully laden jumbo, our 800s operate in general around 66 tons which is 13 tons below the absolute max that can be bought from boeing (papework job to buy more weight = same airplane). Therefore there is such a lot of spare performance these things would be easily covered in your suggested scenarios. I remember being involved with a Recurrent Training scenario a few years ago where the training dept wanted to train pilots to recognise a max aft CG situation, hoping it would also lead to a tailstrike in order for crews to recover and follow the QRH etc. We ran the scenario in the sim with a 36% aft CG and found most line pilots didnt even notice the difference. I also flew the sim with flaps up and 36% CG on a takeoff using Flap 1 speed and still didnt hit the tail using normal rotation rates. So the point is the airplane is damn good and the crews are pretty good and it would take a lot of unusual events for a crew to get out of shape with this over weight thing. But not impossible! If it can be done it will be done sooner or later, but more likely on a heavy hot and high 777 or 380 etc.

If on the other hand, we were flying Tupolev 154s in a Russian environment be afraid be very afraid!!

26th Oct 2006, 08:47
we do fly all the time on TU 134, TU 154, YAK 42, and we know how to check in with 30kg overweight without it going on the record - then add another 15kg in the duty-free. Then the belly freight with gestimated weight ...

Has there ever been an actual physical cross-check of calculated data when a cap suspects overweight with the relatively simple expedient of electronic load cells ?

late developer
30th Oct 2006, 01:11
Your perspective as an amateur is rather too well informed me thinks?:cool: I'd love to be doing the job JB, but at 50 next year, with my ears and eyes beginning to age, methinks I've left it a tad too late - and besides, my ATPL theory runs out end of November and to be honest, I reckon I have already forgotten far too much to ever be the ace of any base without a complete re-run :ugh: Oh, and as you've seen, I tend to think a lot and then spoil it all by expressing a rather large proportion of it:p Not many employers necessarily like that. So then, I am resigned to just hurtle around the sky in 738s as a paying passenger a dozen or more times a year until I get really scared or run out of money for the car park!
So the point is the airplane is damn good and the crews are pretty good and it would take a lot of unusual events for a crew to get out of shape with this over weight thing.That's what I figured all along with this type, but if someone could enlighten me about the usual reason on 738s for an "erroneous" warning light problem on engine start up, or worse still on applying takeoff power then maybe I'd believe it better! I've had three 'return to ramp's as passenger where captain says we needs an engineer to come see a warning light that shouldn't be on, but which have then been quickly solved without an engineer come see! Hey I wonder - it's not the "We might be a tad heavy" light is it?

Actually I remember one explanation after we had deplaned and been told to expect to wait for an engineer to be flown from the UK, and had each been issued a free half sandwich. Then got shepherded back on just a few minutes later and when we were sitting comfortably again the boss said: "Ladies and Gentlemen we are pleased to inform you that we have solved the problem - actually we discovered another problem which was impacting upon the first! Both problems are now resolved and I think we can go." Da-da! So that'll be alright then!

Reminds me of the "new" '365' trains introduced ten years ago from Kings Cross to Cambridge. They too were nice bits of kit to ride in and had good drivers but far too frequently and for as long as I used them, six times out of ten they just couldn't get the blasted things to move on command after they'd hitched two together ... some inevitable but never fully understood glitch which was always solved eventually by something like "Ladies and Gentlemen if you will be seated please there will be a jolt as I shall try again to recouple, and if that doesn't work, I'll pull the plug and reboot the damn thing. Do not be alarmed if the doors close and the lights go out! Normal service will be resumed when I have reminded the computer what we are here for today!"

And I always felt sorry for the machine when the strip messaging above the door retrograded to something like "Good Morning. My name is HAL.... I am a type 365 locomotive.... I was built in 1995 in Crewe....." and the journey then commenced with no more fuss! Thankfully I never cruised any higher than about 5 feet in one of those.
TU154Yes, now then, if there was ever such a thing as a cold-war copycat not-quite-right piece of kit, then that would be it, eh? I recall receiving that message 15 years or more ago when I read about the CofG causing one to have a tail strike at rest on the apron (at Gatwick was it?) just cos the front pax got off first! Believe it or not, there is a photo of a 747 cargo doing the same party trick somewhere deep in the annals ... personally I reckon all the wobbly types should have one of those special anti-tippy-uppy sticks that the groundcrew hang underneath the tail before loading or unloading - like the one which comes as standard with the Saab 2000! A red and white stick doesn't help much once you have left terra firma though, does it? :hmm:

30th Oct 2006, 09:37
Hello all,

What is the max height the 737NG go? Is FL 41 a bit on the high side? :uhoh:

Cheers :ok:

Jambo Buana
30th Oct 2006, 09:49
A crew would nearly never be able to detect an overweight aircraft just by the amount of taxy power you are using as slope, square wheels etc make it very difficult to assess and again a 2 ton overload is very insignificant in terms of taxy thrust required.

Warning lights during taxy are probably 99 times out of a 100, these days, warnings generated by on board computers that go around sensing and checking systems internally. On the 800 it is called the PSEU, which stands for proximity sensing electronics unit. It monitors micro switches in doors, air /ground logic (sometimes the plane thinks its in the air or vice versa), and the takeoff configuration warning system. Its brother is called the FSEU (flap slat electronic unit) which monitors the health of the proximity sensors on the flap positions versus the actual commanded position of the flaps. As you taxy out, micro switches and proximity sensors etc are exposed to vibration which, if they are faulty or sometimes not, then sends a message to the flight deck in the form of a warning light. To date I have had half a dozen of these warnings, and getting less as the manufacturer improves the product, but mine have all been false warnings and were reset by powering down the computers and rebooting! Yep, just like windows. Actually I have more than 12000 hours on the 737 and have been stuck out of base due to technical reasons, not including birds strikes, just 6 times! Thats why the Boeing is better than the airbus and preferred by the low cost guys like us that dont have an expensive engineer in every destination to reboot the computers or fix a genuine problem. If we break down then we are grounded, but look at the dispatch reliability, it is amazing!

The 154 is statistically the most dangerous passenger airplane in the world. It has killed, with the help of the crew, the design and the unreliability of the engines, thousands of people. Thats why you shouldnt fly in any of the old soviet a/c. The airmanship and skill required to fly these things safely is far greater than the achievable airmanship and ability demonstrated by the average crew!

The 800 will also tip on its tail if everyone is sitting down the back end of the plane with no baggage in the front hold. The typical scenario that this will happen is during an on board fracas perhaps, when a pax goes berserk. The police get on and hold everyone behind the incident for interviewing. If this is behing the over wing exits the recipe is set. And yes it has happened at Ryanair, but luckily the captain (an excellent South African pilot) was ahead of the game, and only the bottom step of the airstairs came off the ground.

Phew!! Hope this is helping to calm the nerves! Cant do much about the car park payments though :yuk: