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Guest TheCat

Climb/descend/approach speeds and distances

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Hello all,This was probably asked before, but I would just like to ask a fewpretty fundamental questions.All the questions generally pertain to the 747-400, which I like to flymost often.First of all, regarding climb rate. Generally I set my autopilot to aclimb rate of 1800 fpm initially, and then reduce to 1500 fpm when Istart losing airspeed. However, in a few locations on the web I foundarticles describing climbing at up to 4000 fpm on some models of theengines. 4000 is of course too much, but what is the best initial climbrate for the B744? Is 1800 fpm unnecessarily low? It does seem to havemuch more power initially, and I often exceed the 250 kt limit when myautopilot lowers the nose for my specified climb.Next, regarding the descent to my destination airport. I seem to havesome trouble judging the distance from the airport at which to startdescending from cruise, and often arrive too high, or sometimes too low.Can someone give me an optimum distance to start descending and adescend rate (or set of descents, I'm really clueless with regards tothis). I cruise typically at FL350 at Mach 0.85. Also, if I use theautothrottle, what should I set it to when I start my descent so Idon't create an overspeed situation? I typically reduce the settingsignificantly, but I wonder if that's necessary initially. I also oftenhave to descend too fast and have trouble not exceeding 250 kts whenI enter back below 10,000 feet.Thanks for any help!

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>Hello all,>>This was probably asked before, but I would just like to ask a>few>pretty fundamental questions.>>All the questions generally pertain to the 747-400, which I>like to fly>most often.>>First of all, regarding climb rate. Generally I set my>autopilot to a>climb rate of 1800 fpm initially, and then reduce to 1500 fpm>when I>start losing airspeed. However, in a few locations on the web>I found>articles describing climbing at up to 4000 fpm on some models>of the>engines. 4000 is of course too much, but what is the best>initial climb>rate for the B744? Is 1800 fpm unnecessarily low? It does seem>to have>much more power initially, and I often exceed the 250 kt limit>when my>autopilot lowers the nose for my specified climb.>>Next, regarding the descent to my destination airport. I seem>to have>some trouble judging the distance from the airport at which to>start>descending from cruise, and often arrive too high, or>sometimes too low.>Can someone give me an optimum distance to start descending>and a>descend rate (or set of descents, I'm really clueless with>regards to>this). I cruise typically at FL350 at Mach 0.85. Also, if I>use the>autothrottle, what should I set it to when I start my descent>so I>don't create an overspeed situation? I typically reduce the>setting>significantly, but I wonder if that's necessary initially. I>also often>have to descend too fast and have trouble not exceeding 250>kts when>I enter back below 10,000 feet.>>Thanks for any help!Hey,The general rule of thumb is to aim for a 180kt (KIAS) airspeed for your initial climb out of the field. In saying this, the FPM rate depends largely on your load. The best way to do this is to use the MFD/Artifical horizon and aim for a good 15deg. Usually this will result in between 2800fpm right up to 3300fpm but like I said this depends on your load.You continue to aim for 180kts until about 8-10,000ft (or transition level) then start your main climb out. Obviouly the higher you are the less fuel you burn and because the majority of your flight is the cruise, you want to be in the cruise, as soon as possible to run the aircraft at eco. So, without busting your pax ears, aim for a climb of about between 250 and 290kts. This will result in about 2100fpm, but will vary depending on your load, yet again. As you have noticed, the higher you get, the less you can climb. So just continue to reduce the VS on the AP to retain your climb out speed. In the real world, the FMC will make all these FPM/VS/KIAS decesions for you, depending on your operating mode. Once at Cruise, boost her up to .85 or whatever your desired speed is.As for the descent into a location. There are a few different ways of ways of calculating this. Basically ALL ways will be using track miles as opposed to DME. The difference between the 2 are as follows:Track miles: This is the dist of your route that you are taking.DME: dist you are away from the VOR/NAVAID. *All dist communicated via atc is based on your dist from a fix/navaid/ap or a place in space etc etc unless otherwise stated with the termonology "track miles". IE: ABC, you have 5 track miles to run"Now, it is quite common for you to be 100nm away from the VOR but really have a total of 120 track miles to run or land. Why is this? well because you have to travel the extra 10 miles on downwind (away from the VOR), 5 miles on base and about 5 for final (figures are examples only) and this is just an example.So, now that we understand the difference between trk miles and DME dist, it gets more difficult.To know your TOD (top of decent or AKA BOD - beginning of descent) you need to make some choices. Once again, a real world FMC will do this for you but in FS (minus payware like PMDG) you need to work this one out for yourself. The choices you need to make is what your fpm descent rate will be. This can be anything within the aircrafts operating limit - or without blowing yours and your pax ears, aim for between 1500fpm for super comfy and slow or 2100fpm for a faster descent.Now, working out when to head on back to ground.Method 1: the 3x rule. Simply get your FL remove the last 3 digits and then multiply it by 3. IE: We are crzing at FL330. 33x3=99. This means our TOD would be @ 99 track miles. BUT the problem with this, the meathod assumes you would be descending at about 1900fpm, give or take. So you dont have a choice of your descent rate. Method 2: This one is if you like calcuations. You need to know your adverage TAS during descent and what FPM you want to descend at. To keep it simple it is.actual crz (not in FL abbreviation) / desired VS * adverage TAS during descent / 60 = TOD in track milesie:33000ft / 1500fpm * 350tas / 60 = TOD @ 128.3 track miles.Method 3: Time of descent. This is not that realiable as you need to know update to date/realtime figures such as your ATD, ETR & ETA.This is quite simple as all you need to do is obtain how many minutes it is going to take you to get from 33000ft to 0ft. So, it is crz alt / desired fpm/vsIE: 33000ft / 1500fpm = 22mins.So, if I am expected to arrive at my dest at 12:22. I should start my descent at 12:00 @ 1500 on the VS dial. This then tells me that in 22mins, I will be at 0ft..Controlling your spd on descent also depends on your acft. The Airbus for example (A320) is a fast little #### and requires almost all the time a touch of speed break. A good rule of thumb is to get down to .75mach or 300kias (whatever is lowest) 3000ft before your transition level. Then for the last 3000ft until you hit the max 250kt mark (here in aus it is 10,000ft) you should aim to drop off 55-60kts bringing your IAS down to 245-240. After that, you really just want to be flirting with your landing speed by final, so make adjustments as needed. At the end of the day, a lot of this depends on the aircraft type itself but this is as generic as it can be, and for FS it will work.I hope this helps to some degree.Steve.

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Wow, I must say, this was a very detailed response!Thank you! It definitely helped a great deal!Although I am familiar in general with the traffic pattern and itsvarious legs, I usually don't follow a strict pattern upon approach,and just give a set of headings to the autopilot to follow dependingon my assigned runway aided by the GPS.I wonder, if I am told to fly straight in to runway X, do I stilltechnically need to perform the full pattern? Because it makes senseto just land directly. I am often told to fly straight in intoHeathrow when I fly from Toronto.Also, I noticed you mentioned the speed brakes on the Airbus A320. Isthat referring to the spoilers or something else? I was always underthe impression that they are not to be engaged in high speeds, kind oflike the flaps.Thanks!

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Unfortunately, the 2 main parts of flight are not as simple as it should be L hehe. So much more goes in to climb and descent, this was just some touch on revision.In regards to the approach that should be flown. This in itself a whole new kettle of fish. In the real world there are set entry points and routs to follow to get the aircraft down on the runway. This is called a STAR. I am not sure if you are aware of. It must be noticed though that throughout all the airfields in the world, MOST do NOT have a STAR

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Thank you! Your help is much appreciated!I guess I'll just experiment a little :)

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180 kts to 8-10,000ft seems very slow.You want to be climbing out and rolling the flaps up anywhere above 1,500. Be at clean initial climb speed shortly after. Up around 220-250 until 10,000, depending on pitch rate, then pick it up to FMC speed afterwards.

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I guess so but at the end of the day it really depends on your load and how quick you need to get to crz. Its not uncommon for fmc to take an a320 to fl150 at 200/190kts depending on the mode they are running the fmc at, usually eco. Either way, you want to reach trans alt ASAP, this meaning best rate of climb. once trans alt is reached, then aim for your the premium climb to crz, this usually between 250-290kts.

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>The general rule of thumb is to aim for a 180kt (KIAS)>airspeed for your initial climb out of the field. In saying>this, the FPM rate depends largely on your load. The best way>to do this is to use the MFD/Artifical horizon and aim for a>good 15deg. Usually this will result in between 2800fpm right>up to 3300fpm but like I said this depends on your load.Yes, at least up to 1500ft. After that, start pulling the flaps in, lower your VS, and aim for 220-250kt. A very heavy 747 will require Flaps 1 at speeds below 260-270kt, and in such a situation it is quite legal to go as high as 280-290kt, if such speeds are necessary for safe operations.To kind of simulate the FLCH/VNAV mode on most modern airliners, you want to just set a climb power manually (85-95% N1), leaving autothrottle OFF, and vary your VS manually to hold the airspeed you want (unless the plane is really light, since you will wind up with crazy climb rates). IE, if you get slow, lower the VS; if you're too fast, raise it a bit. Once you hit 10,000ft (or whatever the transition level is), set VS to about 1500fpm, and accelerate to 290-340kt, depending on the aircraft. Your 747 will like the high values. Continue climbing, but keep an eye on your Mach readout as you get towards 25,000-30,000ft. When it hits about .80-.82 (for your 747), hold that value as you were doing earlier, but using the Mach readout instead of IAS. Once you level off at cruise, you can engage the autothrottle as necessary.

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I agree, it is too slow. General ICAO noise abatement procedure involves climbing away at V2+15 to 1500' above the ground at take-off power. Then V2+15 to 3000' above the ground at climb thrust, then accelerate to Vy (best rate) clean speed which will be limited to the 250kts speed restriction on most jets below 10,000'. Above 10,000' cruise climb would be something like 280kts. All at climb thrust. Speeds may vary by 10-15kts depending on weight. The rate of climb you get is what you get depending on the weight. The general idea is to get away from the ground as quickly as possible with a low a noise footprint as possible, when that is achieved, it is then a case of getting to cruise as quickly as possible.

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>I guess so but at the end of the day it really depends on>your load and how quick you need to get to crz. Its not>uncommon for fmc to take an a320 to fl150 at 200/190kts>depending on the mode they are running the fmc at, usually>eco. I have yet to see an A320 (even a little 319) command anything less than 220kts after the initial turn has been made. Even then it's very rare. As others have posted, in the real world it's take off power (derated or otherwise) at v2 plus a bit, to the acceleration altitude (which is runway dependent but usually around 1000ft above the ground). Then 250 knots until FL100 (or 10,000ft) or as otherwise instructed. A 747 at high weights will require a higher speed than that, 270kts maybe. After that it depends on your cost index, I've seen as low as 258 and as high as 342 (on an Airbus). Even using a cost index of zero would command a greater speed than what you're advocating. >Either way, you want to reach trans alt ASAP, this meaning>best rate of climb. once trans alt is reached, then aim for>your the premium climb to crz, this usually between>250-290kts.Nobody gives a monkeys about the transition alt, especially not with regards to speed. It could be argued that the transition altitude is often near the MSA (minimum safe altitude) and hence keeping a lower speed until then may be a good idea in certain circumstances. However, even then, at 220kts even an old, heavy A320 would go up like a lift. If you have a high MSA that needs clearing by all means fly a bit slower but anything less than 210kts in a jet is unnecessary (and in a heavy 747 most definitely not recommended).Most of the time 250 to FL100 then 280-330kts until you switch to Mach nos.With regards to the descent questions I think everyone else has covered them but here's a few pointers. The 3 times table is good (FL300 requires 100nm to descend). Don't forget that it takes about 10nm to slow down from 300kts to 220kts. Don't forget the wind (a stonking tailwind will get you seriously high very quickly). Don't forget about the altitude of the airfield, in some places that can make a big difference. In exceptional days the QNH could affect your descent but that's very *very* rare. Don't rely too much on the FMC (of FMGS), it only knows what you've told it, sometimes you have to go with your gut about where you think ATC will vector you. Guess at track miles to go, then work out how high you should be (not forgetting wind, airport alt and slowing down) then decide if you are high or low. The 3 times table (contrary to what you've been told in this thread) is loosely based on a three degree (over the ground) descent angle. As a rule of thumb, to achieve this, halve your groundspeed (400kts = 2000ft/min). If speedbrakes are needed to help get you down, use them, they rarely have a speed limit (how silly would that be? "We're so fast we can't use the very device that is designed to slow us down" eh?).Once you're slowed up speedbrakes rapidly lose effectiveness, start getting the flap out (speed permitting) to help your cause. If things get really bad drop the gear, that's very good at adding drag and rescuing a hot and high situation. Of course, both flaps and gear have limiting speeds so use with caution.Hope this little bit of real world info helps (and doesn't make this tricky subject any more difficult than it really is).Take care,Ian

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>I agree with the kias above 10k, but like i said, depending on>the cost index (mode being easier wording for the people not>up to speed), it is not uncommon to see such kias on the dial>- 190-200 for the INIT climb to the trans alt... I never said>a definate, just "not uncommon" - this is also taking FS in to>account and its failure to reproduce accurate real world data.Sorry, disagree, it's *very* uncommon to see less than 220kts for the initial climb. Nobody cares about trans alt so a "climb to the trans alt" is misleading at best. Most of the time the first speed limit is the 250kts below FL100.>Remember, we were wording this stuff for someone who is not>100 up to speed with the every day talk amongst RL pilots. That doesn't mean we can tell him something that is untrue just because we can't explain it properly though, does it?>As for making a tricky subject more difficult, im sure that>has just been done....By me? Maybe, I'd prefer it to be tricky but correct than simple but downright, plain and simple wrong.>Another case of people wanting to prove their real world>knowledge (be it an experience outside of FS or not) by>bragging about what they know using terms and garble that not>all will understand... Good work tiger :)If my explanation was unclear then I apologise, if you couldn't understand it then I recommend you ask rather than patronise, it just makes you look misinformed and ignorant. I'd like to think that most simmers could understand what I wrote and if not, most are clever enough to ask, don't judge them by your standards.>PS: At the risk of turning this into a pprune thread by>continuing, I tend not to reply any further.Good idea, you're making things confusing by telling untruths.>TheCat, the best way to learn is to experiment, if you wanting>to replicate real world procedures, there is plenty of reading>out their but you must keep in find that what works for the>RW, may not be replicated in the sim. Either way, have fun and>keep on learning, there is so much to learn, it never stops!>hahaI concur, although most of stuff we do in the real world can be *simulated* quite well, not perfect but close enough. There is indeed much to learn ... but the learning never stops, the second you think you've reached the exalted heights of our Steve here and there's nothing more to learn, you're dead.Hope this hasn't gone too far downhill for you all,Take careIan

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Bah, I give up haha.I took to long to edit my last post, got a bit trigger happy with the post button.Either way, I dont really care.Best listen to Ian (No sarcasm).Cheers,Steve.Edit: PS: TheCat tried removing my threads so you dont get confused with what others and I are saying but the edit feature wouldnt work, just keep focused on what others have said, mainly Ian, he's is spot on for the real world.All i ask is that Just dont kick yourself when you find the aircraft in FS wont perform like RW acft would . I'm assuming that Ian has real world experience and should be aware of the differences but obviously it was more important to communicate his real world knowledge than pass on what would be most likely be more helpful in FS, just so you dont have big expectations. Ian, my statement re always learing was made on the assumption that I to am always learning. Like you, a Pilot should never expect to know all because simply a pilot never will. For you to state that I am a know-all is outright purely discusting, we all dont spend thousands and thousands of dollars learning and expect to know all. For one to put such hard work and money in to such a theory and career, it would be a discrase to think one knows all.. You can stick that comment right back up where it came from cowboy :). Enter the Pprune bahahah.Enough from me!

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>Edit: PS: TheCat tried removing my threads so you dont get>confused with what others and I are saying but the edit>feature wouldnt work, just keep focused on what others have>said, mainly Ian, he's is spot on for the real world.>All i ask is that Just dont kick yourself when you find the>aircraft in FS wont perform like RW acft would .The difference is small enough that most of us won't notice but you're correct, FS is not quite right aircraft performance but it's good enough.> I'm assuming>that Ian has real world experience and should be aware of the>differences but obviously it was more important to communicate>his real world knowledge than pass on what would be most>likely be more helpful in FS, just so you dont have big>expectations. I was under the impression that real world experience *would* be helpful in FS.>Ian, my statement re always learing was made on the assumption>that I to am always learning. Like you, a Pilot should never>expect to know all because simply a pilot never will. For you>to state that I am a know-all is outright purely discusting,>we all dont spend thousands and thousands of dollars learning>and expect to know all. For one to put such hard work and>money in to such a theory and career, it would be a discrase>to think one knows all.. You can stick that comment right back>up where it came from cowboy :). Just saying it like I see it sunshine, Take care all,Ian

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