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When to disengage A/T and autopilot
40 replies to this topic
Posted 27 September 2011 - 03:31 AM
Hi all When I'm doing an ILS landing, I disengage autopilot at 200 feet above the runway and the A/T a little bit later.Are these the correct altitudes? And when I disengage A/T, when do I put the engines to idle? Just before touchdown or at 50 feet for example? Thanks!
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Posted 27 September 2011 - 01:56 PM
There is no correct altitude, but for many it's not allowed to operate the automatics for that long. CAT I DH is 200R, so if you're not flying the fancy autoland I'd have BOTH AP and AT switched off before the minimum. Technically though, you might leave it on for longer. In FS anyways. Obviously it depends on the aircraft you're flying very much. A little more info would certainly help. When to put the engines to idle is a moot question. Whenever you need to, is probably the most correct answer. There is no 'altitude' where this should happen. As an example, when flying your good ole Skyhawk, some will say "cut the throttle over the threshold". Fine. Someone else might say "start reducing over the threshold to reach idle at touchdown". Now what? And then someone else comes along and says "are you crazy, don't pull back the throttle, leave some power until touchdown or you'll drop like a stone!". I'm sorry?What I want to say is, there are different "philosophies". And just as it's impossible to give a 1-2-3 how-to of the flare, you can't specify an exact general point when to do what to your throttles. And as said above, it certainly makes a difference if you're landing the Skyhawk or the Jumbo. The Skyhawk will almost go into a stall as you try to hold it off the runway. The heavy iron however is 'driven' into the ground more or less with no significant flare. Actually a firm landing should be more desirable than a greaser, especially when you're new to the plane. 'Soft and smooth' is not equal to 'good', and I can't stress that enough as it still seems to be the prevailing opinion. EDITSome more thoughts on the FS idiosyncrasies. Flying a stock plane or any plane that uses the stock autopilot, you can leave approach mode and autothrottle enabled until after touchdown, of course. But first of all, your flare won't exactly be a flare. Secondly, the engaged AT will try to maintain speed forever, which is something you certainly don't want. Even if you flare manually, AT will obviously increase thrust in order to accomodate for the reduced descent rate. So don't do that. Many airlines have SOPs that you either use AP and AT, or none. No mixed operation.
Edited by badderjet, 27 September 2011 - 02:16 PM.
Posted 28 September 2011 - 06:06 AM
1.You don't 'drive' a heavy into the ground. Expecially on a heavy it's important to reduce the rate of descend to achieve a smooth touchdown as 'driving' the plane onto the ground places significant stress on the plane structure which reduces the lifetime of quite a few structural components.2. That depends a lot on the manufacturer as well. E.g. the 777 in our fleet are almost always flown during the approach with the autopilot disengaged and the autothrottle engaged. The 767 on the other hand doesn't like this method at all. @RestUnkown Autothrottle Most autopilots/autothrottles are certrified to at least 80ft AGL. So you can leave both on until that height.Problem is that you don't have time to develop any 'feel' for the plane to achive a nice flare if you disconnect the AP that late.Preferable is between 500ft and 1000ft as this is a matter of concentration as well.Of course if you fly a manual ILS in really bad weather with very little visual cues you leave both on until very last moment which is in case of no autoland at around 50ft. Idle E.g. the 767 manual states that the thrustlevers shoud reach the idle position together with main wheel touchdown.It's an awful feeling to pull to the power off at 30ft only to find out that you hit a downdraft at 20ft without the ability to do anything against it!Either if it's a C172 or a B747 it's mostly a question of your energy state.If you arrive over the threshold at the minium speed approach speed in he 747 and the 172 you will need to keep the power on much longar than arriving over the threshold at the min app speed +15kts...
1.The heavy iron however is 'driven' into the ground more or less with no significant flare.2. Many airlines have SOPs that you either use AP and AT, or none. No mixed operation.
Posted 29 September 2011 - 09:24 AM
What way do you guys turn off A/T and A/P? Is there a preffered way? Meaning do you hit disengage bar for A/P and then hit the alarm buzzer to shut it up, or is there a way to do it with a joystick button? The only other way I know of is flip the F/D off but that doesnt seem proper. This ofcourse is regarding an ILS landing. Is the only way to kill A/T, the "arm" switch. Thanks to anyone who can help with this, Im using pmdg 738 if that matters!!! Thanks in advance!!!
Posted 29 September 2011 - 12:08 PM
You should always use the AP and A/T disconnect buttons on the yoke and the thrustlevers. Using the AP disengage bar and the A/T arm switch prevents any re-engagement which is something you definitely don't want.Switching the FD off is a no-go because you are loosing the lateral and vertical guidance just at the final important stages of the approach.Don't have the PMDG 737 but either there are associated click spots or you should assign a button or key for these 2 items. Some goes for the G/A mode.
Posted 31 October 2011 - 08:22 AM
In the ulralight I'm training in, the throttles goes to idle when I turn final! :D Of course depending on the winds I might have to throw in the throttle OR use crossed controls after that...
When to put the engines to idle is a moot question. Whenever you need to, is probably the most correct answer. There is no 'altitude' where this should happen.
Posted 19 December 2011 - 06:03 PM
Every airplane is 'driven' onto the runway for landing; especially in a jet, where trying to achieve a smooth touchdown could result in hundreds of feet of additional runway to stop the airplane due to excessive float or flaring - this is ever more important in the larger the airplane because the runway required for landing and meeting safety performance is of the utmost importance (e.g. what if you excessively float to get a smooth touchdown and float hundreds of feet down the runway and soon realize you have no brakes, T/Rs, anti-skid, directional control, etc...? As, in the real world, any of those could present a serious situation in a heavy airplane if you were only concerned with achieving a smooth touchdown). Just as important to the before is airspeed control, as that could equally result in excessive runway usage upon take-off or landing. The airplane is built to withstand a hard touchdown, the airframe structure is the least I'd be worried about (I'd say anything less than 500 FPM is perfectly fine). Now, of course you'll see those circumstances where an excessively heavy touchdown occurs and the aircraft will set off its' reporting mechanism that a heavy landing check is required, but in my experience those are few and far between; as, in the real world, you'd much rather have a hard touchdown and the aircraft go into inspection than run the risk of running off the end of the runway. I say this coming from a real world perspective, but that has been my experience in flying jets.However, being that this is FS and a simulated environment, do all that you please; as your decisions really make no difference.
1.You don't 'drive' a heavy into the ground. Expecially on a heavy it's important to reduce the rate of descend to achieve a smooth touchdown as 'driving' the plane onto the ground places significant stress on the plane structure which reduces the lifetime of quite a few structural components.
Posted 20 December 2011 - 10:42 AM
TDZ distance: Irrelevant. TDZ may be standard, but what really matters is total runway length (in a heavy airplane).T/R's not used for distance calculation: Correct, but they will still help you when you land long trying to achieve a smooth touchdown. Landing distance calculation is measured from the same touchdown point, so if you land after that point, any distance calculation goes out the window.Touchdown (and by extension of that, landing) is considered good when you have the correct speed, the correct height above threshold and you touchdown at the correct point on the runway, which is the aiming points. No points for smoothness. Remember the old saying "Any landing you can walk away from is a good landing"?
Not much to reply except that these are a lots of words with lots of wrong information.I assume you know how long the TDZ is.....that T/Rs are not being used for the landing distance calculation etc....
Posted 20 December 2011 - 12:10 PM
Bstolle, not sure what problem you have with E6BAV8R's post. Everything he says is spot on. Would be interested in knowing why your company goes against every SOP I know off.Aim for a firm touchdown to ensure spoiler deployment, this cant be stressed enough in wet/slippery runway conditions. The only time I hear of this obsession with smooth landings or greasers is from simmers.Best thing to do is watch the autoland on most types, again a common misconseption among simmers is that the autoland is smooth when in reality is designed to be fairly heavy to ensure proper weight on wheels and spoiler deployment. Only a few FS addons I know get it right, even the PMDG 744 gets this wrong, they fixed it with the MD11Regards
Posted 20 December 2011 - 12:42 PM
LOL, apparently you've never experienced an autoland in a 767. The rest you mentioned is as wrong as Eds & e6bav8r statements concerning standard ops.Suddenly you come up with wet/slippery runway conditions which is an entirely different situation. Same goes for a landing on a limiting runway of course.If you are landing on a standard e.g. 11-13000ft long runway in dry non-crosswind conditions there's absolutely no need, and it's not desireable to drop the plane at the 1000ft marker.It's amazing how many know-alls are posting crap and are accusing me and my company of violating SOPs.
again a common misconseption among simmers is that the autoland is smooth when in reality is designed to be fairly heavy to ensure proper weight on wheels and spoiler deployment.
Posted 20 December 2011 - 01:10 PM
(LOL) How old are you again? please calm down. No, never operated the 767 simulator in an autoland just hand flew it. However my father was on the 767-300 with Gulf Air for 5 years so I will check with him. And with your wisdom I am sure that you realise that no 2 autolands will be the same for a number of factors.My ref to autoland was regarding the fact that the autoland system on all aircraft I know off can not tell the difference between a dry or contaminated runway therefore are programmed for firm landings.I didn't suddenly come up with wet/slippery runways, it was my first post on the subject - reread my post, I said it cant be stressed enough in those conditions, however as every one else has pointed out, your priority should be a firm landing at Vref and on target.Unless you are Chuck Yeager, trying to get that smooth landing/greaser will more then likely just eat up runway. But if you are in perfect conditions - want to stroke your ego and practice with SLF in the back then knock yourself out. It is all down to judgment since we are not machines..Lastly, how am I saying your company is violating SOP? SOP is just that - Your companys Standard Operating ProcedureCurios to know what airline you work for, and perhaps smooth/firm/heavy should be definedKind Regards
Posted 20 December 2011 - 06:01 PM
What, in your mind, is wrong? Standard Ops are Standard Ops and are specific to each and every operator, as approved by the regulator.
LOL, apparently you've never experienced an autoland in a 767. The rest you mentioned is as wrong as Eds & e6bav8r statements concerning standard ops.
None of us said you must touchdown within the first 1,000 feet of any runway, regardless of the length.FAR 91.175(I)(1) stipulates that "The aircraft must continuously be in a position from which a descent to a landing on the intended runway can be made at a normal rate of descent using normal maneuvers, and, for operations conducted under part 121 or part 135 of this chapter, the descent rate will allow touchdown to occur within the touchdown zone of the runway of intended landing." Therefore, the Touchdown Zone does hold legal weight. Going back to what we were talking about, we said you should touchdown within the Touchdown Zone (que Touchdown Zone Marker references), which is typically defined as "...a point 500 - 3,000 feet beyond the runway threshold not to exceed the first one-third of the runway." Keep in mind that has no bearing on landing distance calculations.It appears you're from Austria so obviously the FAA regulations aren't applicable to you there, but I'm willing to bet whomever your local regulator is isn't far off or is the exact same from that. Keep in mind that each Operator's SOPs may be more strict than (and often are) but not more lax than that.
If you are landing on a standard e.g. 11-13000ft long runway in dry non-crosswind conditions there's absolutely no need, and it's not desireable to drop the plane at the 1000ft marker.
Posted 20 December 2011 - 06:26 PM
trying to achieve a smooth touchdown could result in hundreds of feet of additional runway to stop the airplane due to excessive float or flaring
First you state that hundreds of feet could lead to a runway overshoot, now thousands are ok.On the other hand do you really think that wasting 3000ft on a wet runway is acceptable?
we said you should touchdown within the Touchdown Zone a point 500 - 3,000 feet beyond the runway threshold
Repeating wrong info doesn't make it correct ;)As I mentioned before, it's amazing with what level of confidence people post wrong, contradicting and incomplete 'information'....Have a nice day
My ref to autoland was regarding the fact that the autoland system on all aircraft I know off can not tell the difference between a dry or contaminated runway therefore are programmed for firm landings.
Posted 20 December 2011 - 07:09 PM
Yes, it most certainly can; depending upon the aircraft and the runway length. Ever see an airplane overrun a runway? There are reasons why. Statistically speaking, most runway overruns occur on clear, VFR days on runways over 5,000 feet, in fact.
First you state that hundreds of feet could lead to a runway overshoot, now thousands are ok.
No, I don't. Where did anyone here say it was? I was simply inserting the FAA's definition of the Touchdown Zone in reference to what we were communicating to you, but obviously it seems to be irrelevant as you continuously attempt to incorrectly point out flaws in regulations and/or twist what we attempting to portray.So, to that question you posed, let me ask you this: Do YOU think wasting 3,000 feet on a wet runway, simply to achieve a smooth, soft touchdown is acceptable? Why or why not?
On the other hand do you really think that wasting 3000ft on a wet runway is acceptable?
Posted 21 December 2011 - 02:00 AM
Hey, that's something new we didn't have before in this thread! May I ask sInce when are heavies landing on e.g. 6000ft runways?Furthermore IF (suddenly) using 3000ft for the flare is ok, how do you want to 'drive' the heavy into the runway after that distance?And you are saying that I'm twisting arguments?
Statistically speaking, most runway overruns occur on clear, VFR days on runways over 5,000 feet, in fact.
Posted 21 December 2011 - 03:46 AM
I realize I shouldn't be posting in this thread since I have absolutely no experience of real world procedures landing anything except an Ultralight! :D But I've always heard that at least when it comes to landing the 747 it's a matter of driving it onto the runway. To quote Mike Ray who wrote "The unofficial Boeing 747-400 Simulator and Checkride procedures manual", "DO NOT hold the jet off, fly it on to the runway. Smootly roll on the nosegear"...taking cover
Posted 21 December 2011 - 04:01 AM
You can do that with the 747 with a different outcome. Due to the large ground effect and the rather high number of wheels the rate of descend is reduced considerable until the struts are compressed on the 747.But have you ever seen e.g. Air Force one doing anything else but a greaser?I doubt that the Air Force 1 pilots deliberately jeopardize the presidents life with such 'dangerous' landings
Posted 21 December 2011 - 05:05 AM
Searching for landing techniques I found this quite interesting document: http://flightsafety....d/fsd_aug04.pdf It has to do with HARD landings and not firm vs smooth landings but landing techniques all the same and I'm definitely putting it on the ipad! :DBtw, with all those spectators what kind of landing would you expect! ;D Admittedly most Air Force 1 landings seemts to look like that. At the other end of the spectra (with crosswinds and a short runway) you have the A380 landing at Oshkosh which I'm sure you have seen many times: (about seven minutes into the clip)
Posted 21 December 2011 - 05:19 AM
Quote from the doc you mentioned.A normal flare that results in a smooth touchdown in the runway touchdown zone generally is desireable when flying turbine powered airplanes.If you observe landings for a few hours on a calm and sunny day you will see that the percentage of pilots not trying to make a very smooth landing is insignificant.
Posted 21 December 2011 - 09:11 AM
Surely, one doesn't want to bang the airplane into the runway every time, but again, regarding a good landing, no points are given for smoothness. It doesn't make much difference if your pax feel a slight bump or don't feel nothing at all when you contact the runway, except wasting runway.And yes, even on a 13000ft runway, you should aim to land the aiming points; it's not going to kill you if you don't land strictly at the 1000ft marker, but you should land at the point where a landing is intended and calculated for.
A normal flare that results in a smooth touchdown IN THE RUNWAY TOUCHDOWN ZONE generally is desireable when flying turbine powered airplanes.
Looks like it.BTW, autoland doesn't care for smoothness, it cares for runway contact position. Obviously it flares, but it is not hoping for a greaser past mid-runway.Back on topic: Autopilot and autothrottle engagement and disengagement while on approach are driven by company SOP. Usually you either have full automation (both on), no automation but flight guidance (neither engaged, but FD approach mode on) or nothing at all. Some SOP's state that disconnection should take place at approach minimums, however it is left at pilot discretion. So if you want to fly the whole approach from the final approach point/fix by hand, you can.
And you are saying that I'm twisting arguments?
Posted 21 December 2011 - 09:22 AM
Some time ago I discussed this with a couple of friends who are captains on 738 and MD-80 respectively and both said that a firm landing is something they always strive for. The "charter landing" always draws the applauds from the cabin, but they also didn't consider it a safe landing. The MD-80 captain also said that making a soft landing creates vibrations in the landing gear that causes unnecessary wear and tear. I have no personal opinion on this since I have no experience or knowledge to fall back on but to my simple mind it makes sense.