Limitations on special Boeing 737-800 series
 

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...

RR,
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.

Its 1.45G buffermargin since yesterday, so now we can climb 200ft ;)

wow! do you guys get paid extra for being test pilots

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.

Story I heard was that it is a Boeing decision due to "production problems" on the B737 over the last few years .

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)

Gr.

Spuis

RAT5 , Like I said:

RTFP!

Carmoisine:

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.

Limitations on special Boeing 737-800 series
 

Okay thanks anyone giving exact information here!

Thats nice to know for ATC for capacity planning. Changing RFPL´s is a matter of time, we understand, and we know that it´s intended to change all RFL´s 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 RFL´s 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

R.R.:D

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.

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!

why flying lower than RFL...!?
 

- 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

Limitations on special Boeing 737-800 series
 

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 RFL´s 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 don´t know, it will have a large impact on the service level.
And I´m 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

R.R.

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.

RR:

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?

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.

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.

jon

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:

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? )