View Full Version : SID given climb gradient

7th Nov 2005, 15:58
Hi to all ,
already used the searchengine but couldīt find an acceptable answer .
1) a SID gives you a climb gradient ( something like min. clb gradient 7% until 7000ft). From which Segment on this is valid(starting at 400ft or after the acceleration alt? ) and how do I know that the aircraft is going to make it?
Is the TO Graph ( obstacle limit) taking care of?

2) encounter a eng. failure on a SID with a min. clb. requirement. Again how do I know that Iīm safe to follow the SID? . Our company offers only for Antalya a special climb out procedure in case of.

Hope someone can help me.

7th Nov 2005, 21:26
(a) SID has naught to do with OEI. Hence has naught to do with segments and acceleration heights. Climb requirement is a straight geometric thing. Not immediately easy to overlay an engine failure procedure on a SID. Is the aircraft going to meet the SID OEI ? ... one needs to do the full OEI escape calculations to establish that ...

(b) refer (a).

In general, SIDs and OEI don't mix and match. SID is intended to be an AEO procedure.

7th Nov 2005, 21:51
J_T.... Now you have scared the poor guy.... :)


7th Nov 2005, 22:27
It doesn't matter which segment it is for. Unless you have reached safety altitude, you cannot begin to work out climb gradient or what rate of climb is acceptable, you have far more important things to do. So, unless you have reached safety altitude, you should have company information or special 'emergency turn' or engine failure procedures to allow for emergencies. This may be something like 'turn left before 5 miles and proceed to XXX climbing to 2000' and advise ATC'.

7th Nov 2005, 23:17
(a) Mutt ... good ... the more we can put the wind up people the more likely they will be to take the subject seriously. Far too many folk fall into the trap of getting so used to the AEO case (and, for twins - especially, AEO is real good) that they subconsciously see the OEI problems as being far less significant than they are.

(b) Rainboe .. or to put it another way .. not suitable for doing it on the run .. the sums need to be done beforehand in a competent engineering manner.

8th Nov 2005, 07:50
I'm not trying to take a shot at anyone, but it seems to me that I've been reading questions like this for years! For the most part, they appear to come from people employed by airlines, so I have to wonder if there are some companies around the world that haven't done their sums (or had someone else do it for them). Surely this sort of thing would be well and truly covered in Route Guides or whatever?

8th Nov 2005, 19:29
Oz, mate .. that's the problem .. it IS an operator responsibility at the end of the day. Most try to do a reasonable job of it, some not so good, a few don't even bother .. including those who might just look at the runway length limits and ignore the climb bits and pieces.

The message you, Mutt, OS and I have to get across .. is that it is not reasonable to expect the pilot to do any sums from scratch during the taxi out to the holding point ....

9th Nov 2005, 08:27
We've all been trying to do that over the years John but it doesn't seem to be making much difference. There's always going to be one more question. It's clear to me that the folks asking these questions are genuinely worried that there's little or no information from their airline about the really difficult places.

I guess the situation won't change until we see a smoking wreck half-way up a hill after take-off. I suppose that the problem we're up against is that, to date, there hasn't been such an event - or, at least, not one that can be attributed to lack of take-off data and OEI escape information.

It's tough enough to work these things out when you can spread out all the weather data, runway data, relevant topo charts (in the right scale), and use computers and calculators to draw the relevant splays. We have time limits for this work, but at least we have the tools and training to do it.

Even on his/her best day, a line skipper couldn't do that and airlines shouldn't expect it. Now all we have to do is convince everyone else about this eh? :uhoh:

9th Nov 2005, 14:24
Okay thanks a lot for your replys. Coming back to the question. Theres no information for the OEI on a departure route. I get it. Have way through.
But still not clear to me: The SID wants you to climb up to xy feet with a gradient of xy. Where is the information that gives you a gradient for a temp. weight etc. . I mean there is a difference if I take off emty or full loaded.
Thanks again.

Empty Cruise
9th Nov 2005, 15:19

yep - full = only a bit of derate / empty = a lot of derate :D

Will make no difference in the end - as j_t and OzExpat have more than hinted at, you don't readily know how much the acceleration segment on one engine is gonna take out of your total climb gradient. As the mass varies, so will the limiting obstacles - on a computer in an office, or with a GWC on stand, it's all very easy to work out.

Re. question 1, from start of 2nd segment.

Re. qestion 2, if you insist on using the SID procedure design gradient, you need to check the "Horizontal distance to end of 3rd segment" graphs in the AFM first. Your limiting mass will be the one that places you at the end of 3rd segment above the PDG. Secondly, you will have to check the final segment climb + the en-route climb limits to be at or above the PDG all the way up to the MSA or the end of the SID.

However, due to increasing obstacle clearance (obstacle identification surface + 0.8%) & a much wider survey area (thereby possibly including even more limiting obstacles) - you will end up with a much lower obstacle limited TOM than a GWC could provide you, So why not forget the SID & go with the GWC + any emergency turn procedure stated therein? :)


Miles Magister
9th Nov 2005, 16:45

There is some good information posted here.

It is the responsibility of the operator to educate crews with the answers to your questions.

JAR-OPS 1.975 and AMC Ops 1.975 state that any airfield with performance limitations should be classified as a Category B aerodrome. I interpret a minimum SID gradient as a performance limitation. In actual fact most of the SID gradients are for noise abatement considerations. However this can lead the unwary into comlacency when they need to be alert.

I have issued Cat B briefs for all airfields with minimum SID gradients that require terain clearance. The briefs include a set of parameters (TOW and Temp) up to which our aircraft can achieve the min SID gradient with an engine failure and engine anti-icing on. If the take off is outside these parameters then the Captain is obliged to consult the AFM before departure. Your AFM or Ops manual should contain a graph of groundspeed vs rate of climb shown as a gradient. There is some guidance on this in JAR-OPS but I do not have the reference on me at the mo.

If you do not have gradient information available in the AFM or Ops manual then it may be wise to consult your chief pilot. But do not challenge him, ask politely and remember the CRM acronim PACE.

Climb gradients and performance are good subjects for ground recurrent training.

A tutor from the D and X.