Rate of descent.

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I was wondering what the 'normal' or average rate of descent was for airliners. I understand that they are held at various levels before being cleared for further descent, but how many feet a minute do they normally descend at?

This is prompted by a small piece in the press today about the Captain of a Low Cost airliner who alledgedly brought his aircraft down at 6,000 feet a minute as he had forgotten to descend when instructed. The paper says this is twice the normal rate. The Captain is said to have admitted this blaming fatigue and stress for a deficiency in 'logical thought.'

By the same token, what is the normal rate of climb? I presume it differs according to type but I know from experience the 737 seems to climb quite steeply while 146 series aircraft of different airlines seem to differ, BA seeming to take a much shallower angle of climb than say SN or Flybe.

Regards,

kev35

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Profile picture for user bmi-star

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Now looking back at a few of my aviation DVD's the larger, more sophisticated airlines use VNAV for decent. Now as you know Kev, i'm not a pilot, but i'd believe the "usual" rate is about -2000fpm

If i'm wrong then sorry, but 6000fpm :eek: that is bad

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6000ft per minute WOW, you gotta be kidding! Thats like a 15 degree (thats probably way out) descent angle. The again, can you slow the aircraft right down so that it doesn't angle so badly?

Not sure but id agree 1500-2000 sounds about right.

Ben

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I only saw the piece briefly in the newsagents this morning. I believe it is either in the People or the Mail on Sunday.

bmi-star.

I'm not a pilot either, that's why I'm asking ;) The article suggests that 3,000 fpm is the normal rate of descent. 10 to 15 minutes for a descent from 30,000 feet might be about right, allowing for holds at various altitudes on the way down. I'm not a frequent enough flyer to be able to work it out.

There must be a set rate though either for airline or a/c type. You often hear calls on the radio where a/c xxxx has to be level at FLxxx before a reporting point.

Just interested to know what the norm is, and, conversely, what 6,000 fpm must feel like.

Regards,

kev35

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Now looking back at a few of my aviation DVD's the larger, more sophisticated airlines use VNAV for decent. Now as you know Kev, i'm not a pilot, but i'd believe the "usual" rate is about -2000fpm

If i'm wrong then sorry, but 6000fpm :eek: that is bad

VNAV is not airline specific, it's Boeing speak for when their Flight Management System equipped aircraft are climbing or descending (it's short for vertical navigation as opposed to LNAV which is lateral navigation) when managed by a pre-programed vertical profile. Airbus use a similar system however in my experience although it is more complicated it is much more accurate in hitting speed and height targets. They do not call it VNAV, they refer to it as a 'managed' climb or descent.

A normal descent profile would give you about 2000fpm however ATC restrictions, etc frequently have you doing much more than that.

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Sorry yes i was thinking of Boeings this moring, i believe its DES mode in a bus wysiwyg?

So got it from the horse's mouth there Kev :D

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Thank you Ian, very appreciative. Do you have any thoughts on the apparent difference in climb angles by 146/RJ aircraft? Is it a sub type thing or is it down to the individual airline's operating procedures?

Regards,

Kevin Mears

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There is a major thread on PPRuNe about the infamous Ryanair decent into Stockholm. It is quite scary really, 6000' pm decent, a/c flown above the flap limiting speed, etc, etc. and no report was made nor subsequent inspection undertaken before the a/c was flown again. Official report is here:

http://www.aaiu.ie/AAIUviewitem.asp?id=6946&lang=ENG&loc=1652

A

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wysiwyg,
You find it more accurate on the Bus, is that based on your time flying the 757? I was reading an article not so long ago that the 757 and 767 werent as good at being on the ball as the 737NG, which manages to meet constraints more accurately. Could be wrong, your the one with the experience :D

Kev,
Have a read of the last post on this thread. I found it eons ago and have kept it bookmarked.
http://www.pprune.org/forums/showthread.php?s=&threadid=46247&highlight=757+minutes+climb

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There is a major thread on PPRuNe about the infamous Ryanair decent into Stockholm. It is quite scary really, 6000' pm decent, a/c flown above the flap limiting speed, etc, etc. and no report was made nor subsequent inspection undertaken before the a/c was flown again. Official report is here:

http://www.aaiu.ie/AAIUviewitem.asp?id=6946&lang=ENG&loc=1652

A

i read that article on Pprune as well, the captain, blamed "months of cumulative build up of personal stress and fatigue", and this cumalative pressure came to a head on the pilots last day with the operator, on the approach to Skavsta airport.

Nose pitch down reached 12.3 degrees which in turn, with the use of slide slip contributed to excessive rates of decent up to 6,200FPM and excessive speeds for flap deployment., This inturn led to the GPWS alarms sounding, which were ignored by the PF as were the speed and height imputs from the PNF.

TAKEN FROM THE REPORT.
The captains report.
"I cannot understand what possesed me to continue the approach, i have replayed these events in my mind hundreds of times and, at no instance do i arrive at the decision i took. I became fixated and lost sight of the big picture. It was only at such a late stage that the events taking place around me actually penetrated my mind; but then i found myself in the landing roll and i cannot understand myself how it was possible for me to show such poor judgement. I can only imagine that certain personal stresses and tiredness affected my ability to think rationally. I do not offer this as an excuse but merely an insight into my deficiency for logical thought.

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What I find amazing is that the captain said he realised that his judgement had been poor during the landing roll, and then he went on and exercised MORE poor judgement by not writing up the flap overspeed and flying the a/c again without an inspection.

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David, yes I would imagine that the VNAV on the 737NG and the 777 is probably a much more sorted thing than it was on the 757. Most 757 pilots only use VNAV for he early/mid stages of the descent and then go to FL CH or V/S for the approach.

Flex, yes the Airbus equivalent of VNAV would appear on the FMA (flight mode annunciator) on the PFD as CLB or DES. The Airbus equivalent of FL CH is OPEN CLB or OPEN DES.

Kev, different types can climb at the same rate while exhibiting totally different body angles. Also when talking about one specific type climb rates can vary for many reasons such as payload and fuel load or whether or not the airline follows a noise abatement policy with regard to climb thrust reduction altitudes and acceleration altitudes for flap retraction.

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Do you have any thoughts on the apparent difference in climb angles by 146/RJ aircraft? Is it a sub type thing or is it down to the individual airline's operating procedures?

Well I'm not a professional pilot just yet but I would like to give my two cents to this particular theory. BA and other 146/RJ operators are keen to use the "Flex/Assumed temp" method which in simple terms is dialling a higher temperature in the TMS (Thrust Management System) which is much higher then the OAT. So let’s say if the temp was 14 degrees outside like it could be @ MAN this time of year, if performance allows it they will enter an flex temp that it is called in the 146/RJ100 into the TMS which could be 48 degrees or something like that. This tricks the engines to believe that it really is 48 degrees outside and so the takeoff N1/EPR of the engines is reduced. The airlines are keen to do this for most departures as it significantly reduces engine life.

Therefore by doing this the roll on the runway is going to be quite a bit longer, and the climb angle more shallow. As the BAe 146/RJ don't have the most meaty engines it can appear that the aircraft is only doing measly numbers of feet per minute on climbout. :p

Hope that helped. :)

Flex 35

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Derating/flexing take offs should actually make all the aircraft achieve more or less the same performance as you reduce you performance level to that which satisfies the required engine out performance criteria. A 146 with a light load will flex a lot whereas the crew of a loaded 146 will only be able to flex a small amount (or maybe not at all) but they are both setting their performance level to just above what is required.

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Derating/flexing take offs should actually make all the aircraft achieve more or less the same performance as you reduce you performance level to that which satisfies the required engine out performance criteria. A 146 with a light load will flex a lot whereas the crew of a loaded 146 will only be able to flex a small amount (or maybe not at all) but they are both setting their performance level to just above what is required.

Thanks for that, having travelled on quite a few 146/RJ100s they don't seem to have that ooomth when Flexed like say a 320 etc, but I guess that is because of the engines.

Flex 35

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Is the captain of the Ryanair flight still flying? (I apologise if it states whether he is or isn't still flying in the article, but my computer won't load it for some reason)

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Thanks for that, having travelled on quite a few 146/RJ100s they don't seem to have that ooomth when Flexed like say a 320 etc, but I guess that is because of the engines.

Flex 35

They don't need to as their performance is based on climbing out on 3 engines whereas the minibus is based on climbing out on one. Therefore all engines working on the 146 means a surplus of power by a third whereas the minibus has double!

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Thanks for the interesting responses. I shall have to see which departures they are making on 15 at BHX next time I go but after reading these excellent responses I think it may be more to do with noise abatement.

Regards,

kev35

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After reading these excellent responses I think it may be more to do with noise abatement.

The thrust reduction at 1500 feet or thereabouts is more often then not for noise abatement and for the accel altitude and where they start retracting the flaps and start accelerating shortly after. Aircraft such as the B757/A320 etc. respond to the accel alt quite well and still climb quite reasonably but the BAe 146 is often quite lacking and this is why sometimes in the BAe 146 they don't actually apply climb thrust if the CLB thrust effects climbout performance badly and also effects the ALT's which they must be at on the SID.

For example out of Paris last year the Capitano decided not to apply CLB thrust (I asked him).

Flex 35

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I

This is prompted by a small piece in the press today about the Captain of a Low Cost airliner who alledgedly brought his aircraft down at 6,000 feet a minute as he had forgotten to descend when instructed. The paper says this is twice the normal rate. The Captain is said to have admitted this blaming fatigue and stress for a deficiency in 'logical thought.'

Regards,

kev35

6000! Ouch, my ears! ;)

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Is the captain of the Ryanair flight still flying? (I apologise if it states whether he is or isn't still flying in the article, but my computer won't load it for some reason)

One would hope not for the sake of passenger safety