Do You Reduce Your Climb Rate In The Last !000 ft?
 

If cleared to level off at a relatively low level, you 'll be approaching that at a very high rate.
What do you guys use to do in that case, let it capture alone or reduce in the last 1000ft?
Do you use VS mode in climb?

Nowadays reducing the rate is becoming a requierement not only for the danger of overshooting, but above all not to trigger undue RA.

If you engage VS mode, remember speed control will default to speed at that time. When you reach selected altitude, it will maintain that speed which may well be lower than required horizontal speed. Usually letting the automatics take care of it works, but if you take over, a check of required speed is needed.

Depends on the type of bird LEM, but on the 737 we used to call "2000 to go"(in the old days that is !) and "1000 to go". At the "1000" call we'd reduce the climb rate gradually to 500 FPM by either CWS on the old 73's or VS on the newer ones.

But, having said that, on all the Efis 73's(Classics) and NG's the autopilot is well capable of sorting out a smooth transition even with high rates. The capture mode works out the rate and adjusts accordingly.

So, to answer the question, on the -200 we'd reduce the rate in the last 1000' to 500FPM till ALT CAP but on the later 73 models the autopilot can do the job well with no danger of a major bust. Unless of course a sudden request to level off has been made and you have to select ALT HLD, different matter.

If the autopilot is not engaged, no matter what the type, I suggest 500FPM within 500 to go is the target.:)

Yes, Gentlemen, I know the autopilot does a good job, but today the problem is Resolution Advisories: if you still have 3000 ft/min
400 ft before levelling off (which the autopilot DOES) you are gonna scare the other transponders AND ATCO's!
It's still not a legal requirement to reduce rate in the last 1000ft, but it won't take many years before it becomes one.
Read the article at www.eurocontrol.int/acas/
I see an increasing number of colleagues on the 737 classic switching to VS=1000 1000ft before levelling off (at low altitudes). The same people used to let George do the whole job.

work with TCAS and not against it...
 

and for this I agree it should be a must to reduce rate approaching a cleared level to avoid nuisance RAs.
I reduce normally the rate when climbing but so far never reduced when descending, eventhough rates are normally much higher.
Probably I should start now...

Hi!

Our airline has a requirement of less than 1500 fpm in the last 1000' of a climb/descent, so as not to set off other people's TCAS (we don't have it yet).

Most of the airplanes I fly don't have any type of speed mode on the autopilot, and the ones that have them need to be less than 500 fpm, generally, to capture the altitude.

The airplanes that don't have any speed mode often need a 200-300 fpm or less rate of change to capture correctly (by manually selecting the altitude mode) and many of them won't do it at all on the first try and have to be re-set.

When we convert to RVSM standards we'll get new autopilots that will work well.

CLiff
KGRB

Reduce the VSI if you are climbing manually for the reasons everyone has stated already (RA avoidance and overshoot). If flying on the autopilot, you will need to quickly lower the VSI wheel or else it will capture quite soon on its own, and maybe not avoid the pending RA.

We are required by our Ops Manual to have a maximum of 2000fpm when the autopilot goes into the ALT CAPTURE schedule either climbing or descending. Makes good sense for tcas and pax comfort. I don't think overshooting the level is a big factor in this SOP though, the Autopilot can cope with level offs from much higher ROC/ROD.

NB 'Overshooting' is not the issue here - TCAS is

Lem said: Nowadays reducing the rate is becoming a requierement not only for the danger of overshooting, but above all not to trigger undue RA.

Danger of overshooting? I thought autopilots were getting better over the years, not becoming prone to overshoot errors.

I would be most surprised to see a serviceable flight guidance system that has been properly set and armed and monitored by a crew overshoot the armed altitude.

(Mind you, I still watch mine).

That is the whole point of a lot of whizz-bangery in the altitude capture mode of an AP. And it is programmed to do it at a "g" that is comfortable to pax.

It is simple enough to do manually - take ten percent of your vertical speed as the point at which to start your level off. ie 2500 fpm descending to F060, commence level off at 6,250 feet. If a manual pilot can do it, should be piece of pie for Otto, who is recalculating it at so-many-megahertz. Also a very useful calculation to make if one is concerned about 'overshooting,' if you are monitoring Otto and he hasnt started to pitch up/down at that point.

I'd be u/s'ing the unit if it overshot.

But for TCAS, well I can accept that, but I am curious -- how many folk here had a RA or TA due simply to high vertical speed approaching an assigned altitude?

Not everybody flies modern autopilots, especially in the third world, so reducing the rate in the last 1000ft is still good basic airmanship.
Of course undue TA/RA are not triggered VERY often.
I personally had a TA because of the rate of the guy above me.
Anyway, don't forget that statistics don't lie, and if you still have any doubt, read this: www.eurocontrol.int/acas/webdocs/ACAS_BULL-D-2.0ReleasedMARCH03.pdf

ITCZ, here's a shocker:

after many years with most different autopilots, I'm now flying the 777....never had an overshoot on other types, but we had one on the 777 recently. Everything correctly armed, etc, and a/c being closely monitored by all as we were in an expedited descent at near Vmo, speed brakes extended, and very fwd c.g. The a/c initially seemed to be levelling normally, and then at selected altitude, not yet in capture, speed brakes being retracted, the a/c pitched down abruptly to 300 feet below, before manual disconnect and recovery. The handling pilot said the a/c seemed to be massively out of target-speed (trim) when he disconnected. The only thing I can compare it to is a "load limit" type scenario on some other autopilots (it was in v/s, selected speed for level flt 250 knots in the window, which you'd expect it to reduce to after alt capture). Blind sided the lot of us....never expected anything like that on the 777; no harm done, but report filed, AP written up, etc.

It may be that the 777 cannot cope with 3000 fpm-plus v/s level-off at vmo, fwd c.g., changing wind and speedbrake configuration change all at the same time....it doesn't come up very often, and it's not recommended for pax comfort!! But if you're doing an emergency descent-type scenario (we'd just had a major medical emergency and were racing for the deck ) - watch out. :uhoh:

BTW, agree with the TCAS comments above - I try to reduce the vertical rate substantially before the last little bit, especially when passing under the arrival routes/opposite direction traffic. It's seems polite to me....

Hmmm interesting.

RRAMJET, Emergency descent v Line operations?

777 did overshoot, but didn't you just describe that as an emergency situation? Fair enough, but the earlier posts are suggesting reducing to 1000fpm as a matter of course in all ops.

FWIW, my coy ops manual and manufacturers ops manual says that my 1980's vintage Smiths AFGS will very likely bust the target altitude in an EMERG DESC. It has never busted a target in day to day ops, sometimes with full airbrake, bastard trim and 3000fpm. Presumably Mr Smith knew what the autopilot could and could not do when they installed it, and then told the pilots of this via their manual.

What does yours say about AP controlled EMERG DESC in the B777?


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Sorry LEM, still don't buy the need to do the autopilot's job for it if your concern is overshooting.

Do you not set your TCAS to look ABV or BLW when climbing/descending to show targets at greater than 2700' sep? At 7200' or 9700' (dep on software revision), and 12 nm range on basic TCAS display, that is at least 2 minutes to spot a fellow below you.

Basic airmanship? To not ruin a colleagues day by avoiding setting off bells and whistles in his cockpit and spilling his coffee, yes. To not approach a hazard (other aircraft, ground, etc) at a high speed (vertical or otherwise) with corresponding great momentum, yes. To have and apply situational awareness before taking such action, yes.

To do it all the time without applying situational awareness and making decisions, no, that is not doing the job one is paid for. If such were necessary, Messrs Smith, Sperry and coy would have programmed it into the unit.

ITCZ
If I can! Unfortunately BA have acquired some 737s which have only 2700 look up and down ie no above/below function - and they are a right pain! Hence the reinforced need to limit climb rates. Even reducing ROC to 1000fpm at the end will not help here, because 2700 is not enough at ANY stage to give time to react to traffic which suddenly appears.

That would be a nuisance, I'll buy that one then. Is it normally selectable on other 737?

What I consider to be the 'normal' and 'user-friendly' has
a 3-pos switch

A 7000 up/2700 down

N 2700 up/2700 down - virtually useless unless traffic is V. intense

B 2700 up/7000 down

Hang on, supplementary point from the antipodean upstart:)

Lets not forget that the TCAS is tracking targets outside the range that it displays. The 2700 thing is to reduce display clutter.

Lets say that one is climbing to F060 at 3000 fpm. The TCAS is watching targets up to 7200'/9700' above depending on software status.

Your autopilot plans (roughly) to start the pitch over to capture F060 at a maximum 5700', six seconds (again, roughly) before it would shoot through F060 if that altitude were not armed for capture. The autothrottles are also perhaps rolling back to keep the speed limit for the terminal control area.

Worst case then is another fellow descending at 3000fpm rate to F070 in your vicinity. Will he not also commence a pitch up at at least 6 seconds before to capture that altitude, and will his TCAS not be tracking you?

Can someone perhaps resolve this as 'so many seconds to closest point of approach' for RA? I cannot remember off the top of my head what CPA triggers an RA. Maybe our answer lies there.

It was indeed the screen 'clutter' I was referring too. Without 'mentioning the war':uhoh: I do not sometimes wish to feel as if I am in middle of a thousand bomber raid (in the cruise).


"Worst case then is another fellow descending at 3000fpm rate to F070 in your vicinity".

Not in my experience. Worst case is a high climb rate to, say, 100, with LEVEL traffic at 110. Happened a fair bit in the 'early' days at LGW with BOGNA SIDs and WILLO arrivals but we have ??all?? learnt now.

I understand the next generation TCAS will know what level you are planning to stop at, which COULD bring its own problems!

Sorry, ITCZ, only just got back from a trip....

No, nothing in the manual, or the Boeing one. The 777 A/P shouldn't have a prob with this maneuvre - it's just a maths exercise for it, so I've been told. The L. a/p has been removed for evaluation on this occasion....

Agree with your comments on older Smiths a/p's and the cautions - absolutely correct.

As regards original topic: it's all about sit. awareness and politeness....:cool:

I have heard this is a constant problem on the Dornier 328Jet on initial climb. The airplane can supposedly climb out at +5000 f/m setting off TCASs. Some FAs love the DOjet, others hate it because they are depending on their shoulder harnesses to save them (ie back to the FD door). I fly the CRJ and we only have this problem of high capture rate when asked to level off at the very low altitudes. In the last year, I have been reducing thrust slightly while climbing in speed mode to shallow the rate of climb the last 1000 feet. Several of my FOs said that I was the only person who they have seen do that. I have wondered about this myself so I enjoyed reading this post.

Cheers.
BBB