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2:04 AM
@ymb1 in re: your answer to the Continuous Descent Approach question. I'm trying to figure out how it could be a safety problem.
 
2:20 AM
@TomMcW ISTM that the safety gains from flying a continuous descent profile outweigh the potential losses from being lower and slower more
 
@Shalvenay Why would you be lower and slower more? I’ve always heard that dive and drive was less safe
@Shalvenay ymb’s answer says something about 4-D trajectory is needed to achieve conflict-free CDA. So I guess it has to do with less accurate airspeed control. I dunno, though.
 
2:40 AM
@TomMcW I think the detractors misunderstand when the dives are happening in dive-and-drive, really. if you step down as soon as you can, you'll actually be lower/slower more often than you would on a CDFA
 
@Shalvenay It said it failed a safety test.
 
@TomMcW I think it was more an operability problem than a safety problem in terms of spacing airplanes on the approach
 
3:02 AM
@Shalvenay Sounds like it
 
 
7 hours later…
10:01 AM
@TomMcW in high density airports, where there are a lot of planes -- in a proper CDA it's the pilot, not the ATCO, that knows the optimum top of descent, now in a very busy environment, if each pilot flew their optimum VNAV path, then conflicts happen
on paper it seems like a really cool idea, apply it to a high density airport, and it's a cool idea that requires very high tech
the solution is for the ATCO to know each pilot's ToD
they can ask by voice, but that's making things worse, so an automated way to each FMS to downlink its 'future plans' is the way to go
then if a conflict is detected ahead of its time, a plane or two can be delayed to solve that conflict
@TomMcW topic change, about your London City comment, it may seem like one runway, but it's one of the hardest single runway apts to control out there, mainly due to the high traffic and that there isn't a full length parallel taxiway
keep that chart in mind when watching the video for runway 27 ops
 
10:34 AM
also, because it's in the middle of London, you need to fly quite steep approaches to it
 
 
1 hour later…
11:53 AM
@Koyovis not sure if you saw my comment, but with regard to this aviation.stackexchange.com/a/47531/14897 maybe it's better suited for chat--I was saying a heavier plane needs a gentler pull, due to the load factor on the heavy wings + the diminishing vertical lift
or is that not correct
@DanHulme true, initially I dismissed it as a pilot's-only problem
 
sure, it's some extra work for the pilot, but it's also relevant to whether you can do a CDA
their ILS glideslope is steeper than normal - maybe I've misremembered the numbers, but I think 5 degrees is normal, and theirs is 15 degrees
 
those were two different posts, see here: aviation.stackexchange.com/q/47622/14897
3 is normal, and London City is close to 6°
 
aha
all I know is that BA pilots keep coming to do circuits in Cambridge because our ILS glideslope is adjustable
 
@DanHulme that's interesting
@DanHulme see the photo / video here: aviation.stackexchange.com/a/43950/14897
quite something
 
 
2 hours later…
1:39 PM
it doesn't feel that steep to me, because the Tiger Moth likes really steep approaches
if you're number two on approach, you always have to be careful not to turn inside the number one, because they're probably running a much longer final than you
 
@DanHulme how steep w.r.t. sink rate? I always thought all GA planes prefer steeper approaches
here's a much better video (minus the HUD stuff), looks cool:
 
@ymb1 say 1.7 km track (just under a nautical mile) to descend the 1000 ft from circuit height, at 65 mph IAS
 
3 times steeper then, must be fun
 
you can do it even steeper if you sideslip to lose energy
 
which reminds me of a question I've been meaning to ask about flying even older rotary engined airplanes, e.g. sopwith camels
 
1:51 PM
I've never flown a rotary, but I might know
 
I'll post in a bit on the site, but it boils down to, the throttle application is continuously on/off
 
yeah, I know the Camel gives you throttle control by simply not firing some cylinders
I don't know if all rotary-engine aircraft did that.
they sound awful when running, like an old car with a misfiring engine
this is why pilots stereotypically wore white scarves - not to keep warm, but to wipe all the oil and fuel off their goggles
 
> throttle control by simply not firing some cylinders
intriguing
are those notifications time delayed, or they do wait for the post to be reviewed
bec it popped up as soon as I reviewed it
 
there's a short delay; I don't think it's review because occasionally I see a spam post in the list and I'm first there to delete it
 
I believe feeds are checked on a timer to avoid flooding the feed's server
I don't think SE treats its own feeds as anything special so it'll be on the same timer
 
 
 
2 hours later…
3:54 PM
@ymb1 Yes mate, did see it and was in the middle of looking into it, got sidetracked & forgot. Will check further tomorrow - midnight here.
 
 
3 hours later…
6:56 PM
@ymb1 EGLC sure isn't built for high volume. All that back-taxiing. How do they get anything done?
I have always wondered why tod isn't part of an IFR flight plan. I asked a question about it at some point. It seems to me that they should be able to figure out where that will be ahead of time. If conditions change dramatically, then they'd have to update, just like anything else in the flight plan.
 
@TomMcW let me just say if the industry had its shit together there would have been awesome datalink applications since 1996
re ToD, it's easy for short flights, not so for long haul, I'll find an example:
@TomMcW see the brief history section I wrote here aviation.stackexchange.com/a/44817/14897 the Pacific example is a good one
@TomMcW and to play the devil's advocate, all that spending on the cool tech to increase the capacity by 30% (IIRC), can be solved by using bigger planes :P :D
bring back the A300! :P
from 1994:
> ATN's coming into existence, however, requires at least three things: cash invest- ment; a modest degree of technical advancement; and agreement over how to proceed. What is emerging, most recently at Flight International's Paris datalinking conference, is that the final element is in short supply.
> I asked a question about it at some point.
@TomMcW can't find it for some reason, link it whenever possible, no rush
 
8:06 PM
8
Q: Why isn't the point you begin descent part of the flight plan?

TomMcWIn This question there is discussion about how to determine when to start the descent from cruise. There are several factors at play and it is usually calculated for maximum fuel performance. Would this calculation not be done ahead of time, especially for aircraft cruising in class A airspace ...

 
@TomMcW so it's two parts, what's been said which is not knowing the exact, and taking into account the other traffic, which brings up the CDA issue, communicating those trajectories and simulating before hand any conflict
 
@ymb1 Casey said in his answer that the FMS calculates it based on the STAR. Doesn't seem that hard to include it in the FP. That'd be a start. But, yeah, with so many different AC types with differing descent profiles, etc. It would be a task for the ATC computer you make it work
 
correction for what I said earlier, the 30% is actually 80-100% more, so still an A300 would do, or a 747-Domestic :P
users may have forgotten, but let's utilize that spam flag option please: aviation.stackexchange.com/q/47659/14897
 
8:25 PM
@ymb1 The real question is how a few inches of snow can gum up KMEM so badly. They got another storm Monday night, so we're still running a full day behind.
 
@TomMcW a guess, loading/offloading planes
 
@ymb1 It must be. They don't seem to be having that much trouble getting flights in/out. During the the years I worked there we didn't have a single snow accumulation. It only actually snowed, as in real, significant flakes, twice. It just melted right off. So I don't know what kind of chaos it creates on the sort
 
8:44 PM
@TomMcW so it's not typical to have such frequent storms?
 
8:59 PM
@ymb1 It appears to be getting more frequent. Hard to say if it's a permanent climate change pattern, but it sure looks that way
 
hi @Farhan got a second in a private room?
@Farhan actually disregard :) will make a meta post about it
 

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