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Mode Control Panel selection - UK

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Mode Control Panel selection - UK

Old 12th Dec 2014, 01:15
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BBK
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Mode Control Panel selection - UK

Hi

Quick question for you lovely ATC chaps/ladies regarding MCP selections on a SID. I don't have a SID chart to hand but say something out of LGW with an initial stop alt of 3000 with higher stop alts and ending at 6000 (from memory!).

My question is: what do you expect the flight crew to select on the MCP, the first restriction or the final cleared altitude. There seems to be some confusion as to which we, as pilots, should select. A colleague was challenged on this presumably because he selected the final alt, which Mode S picked up, but the aircraft in VNAV levelled off as per the SID profile. Shame we don't do famil flights any more as this is the sort of thing it would be good to discuss.

BBK
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Old 12th Dec 2014, 01:36
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I don't have this issue where I work, but I would feel more comfortable if I saw the initial level and not the final level on the mode S.

I'm also thinking that if you go out of VNAV for whatever reason, doesn't that increase the risk of a level bust?

For example, PF decides to hand fly with no FD, for whatever reason there's a distraction in the cockpit. There is no "1000 to go" call or similar because the MCP is set above the initial level, this then leads to a level bust.

I'm just thinking that if the initial level is set then that's more of a "fail-safe" rather than "fail-dangerous" option perhaps? But then again I'm not a pilot.
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Old 12th Dec 2014, 06:03
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BBK/CV

Interesting...

Certainly we're cleared to use the Boeing approved and published "Alternate MCP Setting Technique using VNAV"...which as you say means checking the VNAV profile carefully and if it's OK then setting the highest of any closely spaced SID constraints on the MCP.

It's supposed to reduce crew workload but if that increases the R/T Loading because ATC see something they don't like I guess it'll be back to basics...

I'm just thinking that if the initial level is set then that's more of a "fail-safe" rather than "fail-dangerous" option perhaps?
Might not be - some SIDS (can't think of one at LHR/LGW, but they do exist) can have particularly cunning combinations of step climbs on the SID which will catch you out if you get distracted (e.g. by an R/T call and forget to wind the MCP up at the critical moment.
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Old 12th Dec 2014, 07:02
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Wow

I need to go back to the books. I knew mode S sent more data, but didn't realise it sent back MCP settings.

Does that mean when you give speed restrictions, you can tell when pilots are lying too ? Eg. You say reduce speed to 220kts and they dial 230 on the MCP. You can see that ?
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Old 12th Dec 2014, 07:45
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Does that mean when you give speed restrictions, you can tell when pilots are lying too ? Eg. You say reduce speed to 220kts and they dial 230 on the MCP. You can see that ?
While you can see the selected altitude, the speed that is downlinked is the actual current IAS and Mach No., so you would be able to see that you are doing 230 KIAS, but not if this is what you are targetting. I'm not sure if this functionality is easily viewable or even used in the UK though?

https://www.eurocontrol.int/articles...ional-overview
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Old 12th Dec 2014, 09:46
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Call me old-fashioned (OK, your'e old-fashioned...) but set the first stop alt. Distraction can work both ways, and the VNAV step to the next alt COULD happen even if ATC said 'maintain 4000 due traffic' if you were distracted and didn't reset the MCP. It comes down to who is actually 'in charge' of this beast, doesn't it - HAL or pilot?
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Old 12th Dec 2014, 09:57
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Some operators even set the cruise level on departure. This gives a choice of the following on the mode S for a gatwick departure... 3A, 4A, 5A, 6A, and as I say, even 330 occasionaly. All theoretically correct, or not, depending on your point of view. Got to love standardisation.
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Old 12th Dec 2014, 10:44
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Distraction can work both ways,
Agreed....FWIW going the other way "Descend via.." STARs are becoming commonplace and again you're expected to set the terminating altitude in the MCP and let VNAV "handle" any intermediate constraints..and in some parts of the world you will get shouted at if you don't step down promptly in accordance with the procedure......sometimes you just can't win..
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Old 16th Dec 2014, 12:43
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BBK
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Not long now

Your point about the lack of standardisation is why I am asking!

Wiggy

At work I've debated the pros and cons of whether to select the first altitude restriction or the final altitude and for the moment my purely personal view is the former is better in terms of preventing a level bust. My question was what the controllers at Swanwick are expecting or would like to see.

Thanks to everyone else for their comments. Anyone at London care to comment (is it still called TC Ops?).

regards

BBK
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Old 16th Dec 2014, 14:47
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The SOP wherever I've worked has been first cleared altitude. Anything else just strikes me as a level bust waiting to happen.

How do you manage reducing VS if you have a high MCP altitude set and a low first level off? Also sounds like a recipe for a TCAS RA. I seem to recall someone from STN climbing at a high rate under the LAM stack set off a daisy chain of climb RAs for example.
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Old 16th Dec 2014, 16:00
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The guys and girls at TC want us to set the next altitude constraint on the MCP and not the final altitude on a SID with a stepped climb.

On the TC radar display, the altitude you set on the MCP is displayed on the radar display in orange alongside the traditional radar label, thanks to Mode S. The controller doesn't know what is on the legs page of your FMC and they can only see what we set on the MCP. Therefore they can only assume that what is set on the MCP is the level we are climbing to without any recourse to level flight.

To give an example of why not to set the final altitude on a stepped SID. For arguments sake, we are on westerly ops and we have a departure from LHR on a Detling SID and a LGW departure on a Dover SID launching at similar times. The Dover SID from LGW is stepped initially to 4000 to keep us below the LHR departure that will climb to 6000. Should we elect to set 6000 in the MCP when leaving LGW, then the TC controller will see two aircraft turning towards each other and both climbing to 6000 feet.

I suspect the LGW departure will be challenged PDQ by the controller.

As an aside, I fly the 777 and at my outfit, we are expected to set the next constraint in the MCP until it is assured or we have a ATC clearances that supersedes it. My own view is that even if in level flight, the compliance of a constraint can only be assured as you approach the waypoint with the associated constraint. That is when I would be expected to set the next altitude.

The above may be overlooked if the waypoints are very closely spaced.
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Old 16th Dec 2014, 16:36
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Now that Mode S means Big Brother/Sister is watching I suggest it is simpler for everybody if the guys/gals sitting in seat 0A/0F set the altitude they are climbing to at that time. Forget about the final SID altitude as it makes everything far too complicated and uncertain.
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