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hotmetal
29th Mar 2003, 01:55
Approaching LHR before leaving the hold there is a min 500fpm rate of descent. Does this apply after the hold? I always thought it did but lately I have had some discussions and some people are saying it doesn't and all you have to do is maintain some sort of descent so as to achieve a constant descent approach. I always try and achieve a CDA but with 500fpm minimum. Is that necessary? I thought the min ROD was introduced a few years back when a slow rate of descent was found as a factor in an airprox. If so doesn't it equally apply on the latter stages of approach?

eyeinthesky
29th Mar 2003, 04:26
The AIP is unequivocal:"You must at all times maintain a rate of climb or descent of at least 500fpm. If you are unable to do so you must inform ATC. (sic)" It was introduced so that we know that you will continue to perform in a certain way so that we can base separation upon you. When it all goes wrong it gets very nasty. (There was a humdinger of an incident several years back with a 747 for Heathrow and a G4 (I think) for Luton. The 747 called Approach and was told to reduce speed, so he raised the nose and almost levelled off. The G4 which was being descended on top was doing 1000FPM+ and got very close. The controller was criticised for giving the G4 further descent 100ft too early, but realistically it would have all been OK if the 747 hadn't reduced below 500FPM).

Obviously, if you are sidling down the ILS with a ground speed of 85 kts then 500fpm will put you on the ground about 2 miles short of the runway, so the glideslope or other approach criteria will take over! It is also unlikely that there will be anybody descending on top of you in the approach area who needs to rely upon you maintaining 500fpm.

In effect, what the AIP is covering is ROC/ROD in areas other than SIDs or Approaches, which provide their own lateral separation.

BOAC
29th Mar 2003, 05:47
'eits' - I suspect the CAA may see things differently now and perhaps the AIP has yet to 'catch up'?

A recent CAA pamphlet (cannot quote the detail) advised that RODs of less than 500fpm (in the approach phase) were 'OK' in order to achieve the required CDA profile - as 'hotmetal' says.

9 times out of 10, if one takes the instruction 'descend altitude 3000' and further with the glide' as 'descend now', and flew 500 fpm, you would require power to fly level at 3000' before the GP. I am flying less than 500fpm iaw the pamphlet and achieving CDAs

TopBunk
29th Mar 2003, 15:58
As BOAC says, I think the requirement to maintain minimum 500fpm has been rescinded for LHR (not sure about LGW) once below Transition level and therefore on QNH, in order to better achieve CDA profiles.

Rgds

Jerricho
29th Mar 2003, 18:08
If it helps, for people training for LHR, it is almost physically beaten (well, almost *grin*) into you to issue range from touchdown as soon as practicable to the descent from FL's to altitude when being positioned downwind. I have always worked on allowing descent that will roughly equate with a continuous 3 degree "glide-path" ROD, 18 miles - 6000 ft (keeps the math simple.....I like simple). Sometime this isn't possible, especially if you require an increased ROD for separation, expecially if we are landing on both runways and you are trying to get the first guy down so you can run the following for the other runway over the top of him and not trying to keep him too high above the glide (that make sense?).

It does make me smile though when a certain flight (who shall remain nameless) is told no speed (being the only jet in the sky), given a range from touchdown, and then comes down like a brick and levels for ages. Good fun trying to apply night noise descent restrictions.
;)

moleslayer
29th Mar 2003, 19:43
This subject was flogged to death in Nov/Dec 2002 !!

search 'CDA' and it's all still available to you.

Basically the rules in the London TMA below TA (6000ft), require that no segment of flight is flown 'Level', defined as a change in altitude of less than 50ft in 2nm. Therefore use whatever ROD will achieve that aim. Note this is 'monitored' and letters sent to the companies of the 'sinners' !!

The requirement for a min. ROD = 500fpm en-route, in the hold & down to TA is still mandatory.

Moley.

Duke of Burgundy
30th Mar 2003, 23:14
Just for the record there is no actual prohibition on the use of rates of descent of less than 500 fpm when in the en-route or holding phase above the Transition Altitude.

The requirement is that the pilot should inform the controller if the rate of descent either is, or is anticipated to be, less than 500 fpm.

Incidentally just a word of caution to pilots operating into LHR.

If when below the Transition Altitude you are requested by the controller to report passing a particular altitude, this is almost always so that another aircraft in close lateral proximity can be descended to that altitude. If in order to carry out a continuous descent approach your rate of descent is less than 500 fpm then I think it would be prudent to inform the controller of that fact even though the requirement to do so has been removed.