A/T thrust mode question 744

[Jeff Nielsen 1,385]

Ok Sam, thanks.I guess I should have also said that I dial in 250 in the MCP (out of habit), yes, but I'm on VNav long before I hit that airspeed and the FMC should control the speed limits as set through the FMC during the clb1 phase or whatever you have selected. If you're a bit heavy then, yes it should go to about 263 for 180k lbs of fuel, roughly.In any case by your statements, it seems like they're a bit contradictory (procedure wise), and you should still have speed control during the first few minutes of the flight as long as the A/P and A/T buttons are armed and engaged.I'm going to try another flight and see what happens, this is still very confusing. I'm not sure why "THR" has to be slected via the MCP when it is selected and controlled via the FMC, especailly when the FMS has to make a calculation based on weight and temp, etc.It shouldn't matter whether you go from V/S controlling your rate of ascent/descent to VNav.Anways, let's go try it again. I'll shoot a vid for everyone. Thanks for trying the flight. :-)

[Guest joediamond]

Sam,You bring up some interesting points and we could have an interesting discussion on human factors and system design but I think we would be getting away from the original thread.As far as which is superior regarding VNAV or V/S that would be up to the individual company and most of those decisions are made by folks sitting in cubicles instead of flying the airplanes. We are allowed to climb in speed or V/S, we don't have a VNAV function. My personal preference is speed mode. Aside from having to reach up to the MCP and adjust the speed knob at the proper points it's the same thing VNAV would do. If we had the VNAV option I'd certainly use it provided it was allowed by company procedure. Some airlines don't use VNAV at all, Southwest comes to mind. I know at one time United pilots flying the 757/767 were not allowed to couple VNAV, not sure if it's still that way or not.V/S does have it uses in the climb and descent. Speed mode works great in smooth air, in anything else it will cause the pitch oscillations as the aircraft starts chasing the speed. V/S works much better in these conditions. AS VNAV is a fixed thrust/speed controlling pitch it would suffer the same problem. The work load is higher as you need to pay attention to your airspeed and adjust the V/S rate accordingly. The aircraft I fly does offer speed protection in V/S mode by lowering the nose and reducing the vertical rate if the speed gets too low, it will protect from over speeding in a descent as well by raising the nose as necessary.As far as shutting down the AT with the AP engaged, it's not something you would would normally want to do but how about an abnormal situation? How is the MD11 system affected by a failure of the AT system? If there is a malfunction in the AT system and it's not doing what I want I like a quick way to disable the system without disengaging the AP. The switch on the MCP in the Boeing would allow that, I'm not familiar with the MD11, would that be possible? Is the integrated AT on the MD11 always armed? If so how would you prevent a malfunctioning AT system from re-engaging if the AP were still engaged?Conn McCarthy

[Jeff Nielsen 1,385]

Well folks, this time it worked for me...lol.I'm going to make and upload the video here in a sec so you can get an idea of my partcular flow.This one is for the "I learned about flying from that" column...hehe.

[Guest D17S]

Conn, Now that's interesting. In rough air a speed-on-pitch mode (Vnav SPD or just SPD for non-Vnav airplanes) tends to get a little 'nosey.' As long as it's a stable speed-on-pitch climb, swapping over to V/S sounds like a good interim answer. Experienced pilots will know that in V/S, airspeed now needs to be watched like a hawk. That's terrific insight we TV flyers wouldn't otherwise get. Thanks.All good points about unhooking an miss-behaving AT on an MD11. Just don't know how the fail-through sequence works. But this definitely needs to be do-able if the AT messes up.Remember that Vnav was part of the original FMS with the first batch of 757-767 back in the early 80s. . . but the use of Vnav was not certified for several years. Vnav was there and a fully functional part of the AFS/FMS, but crews were not allowed to officially use it. Vnav did not have a systems problem. They were working the human factors side. Vnav is tough. Initially, crew just didn't get it. Vnav is still the toughest part of the AFS to master. It's still a factor today. That might be at least a contributing factor to why the guys in the rubber cubicles decide the forbid the use of Vnav in some circumstances. Here's an example: One day I was talking to a Capt about some Vnav issues in the cockpit of a 767 as his captivated FO listened in with rapt attention. At one point the excited FO actually raised his hand and exclaimed "I know that one!" And there you have it. Jeff . . . et al, you're not alone. Vnav's tough.

[Jeff Nielsen 1,385]

LOL, the VNav is actually pretty easy. The other day in the 37 I finally learned how to shoot an actual GPS approach using VNav all the way down. It's was a lot of fun.Like I said I have no idea what I did different this time to get it to work. The vid is not the best, but it will illustrate the sequence very well I think.I'm uploading the vid now, shouldn't be too much longer.

[Guest D17S]

Now you're cookin'!

[Jeff Nielsen 1,385]

Ok try this link guys:http://www.onlinesimulationsolutions.com/p...dia/744test.wmvAgain, sorry about being so sloppy, trying to worry about if you're recording and your panel flow can get a little crazy sometimes.The video shows all my stuff working as it should. Maybe not the proper way as per real world procedures, but per my sim procedures so I can enjoy all the pretty scenery and it gets me in the air...lol.large file, about 48mb's

[Guest joediamond]

>Conn, >>Now that's interesting. In rough air a speed-on-pitch mode>(Vnav SPD or just SPD for non-Vnav airplanes) tends to get a>little 'nosey.' As long as it's a stable speed-on-pitch climb,>swapping over to V/S sounds like a good interim answer.>Experienced pilots will know that in V/S, airspeed now needs>to be watched like a hawk. That's terrific insight we TV>flyers wouldn't otherwise get. Thanks.Even in stable air the AP can be too aggressive in pitch. For example, if I'm climbing in SPD at 250 knots and passing 10,000 I reach up and spin the speed knob to 300 knots the AP will lower the nose too far and actually level off the airplane as it tries to accelerate. It's much smoother to select V/S passing 10,000 and reduce the vertical rate to half of it's current rate and then reselect SPD once the desired speed has been reached. Using the basic pitch hold would also work but many airlines prohibit using the basic AP modes. The same goes for transitioning into a climb from level flight. If I'm cruising at 320 knots and select SPD and dial the selected speed to 270 knots I'd better hope everyone in the back is holding on as the airplane is going to try and stand itself on it's tail. It's better to select V/S, get the airplane climbing and then select the SPD mode after the aircraft has slowed to climb speed. This is all technique and will vary for different pilots and different aircraft.Conn

[Guest D17S]

Yo dude, cool flick!Reminds me of my own setup. Disco city. Just keep connectin' the dots till ol FMC's happy.Other than that, it works. Now, on to a bit more real world stuff. The entire point of 1st and 2 segment climb is to successfully deal with an engine failure. If they are all running, virtually anything will provide successful results. This plane is massively overpowered during the TO phase . . . actually by about exactly 25%. All RW procedures within these critical segments are about dealing with an engine failure and obstacle (the ground, a crane or whatever) avoidance with that engine shut down. The main point of setting a V2+10 airspeed in the MCP is to position a speed bug on the speed tape (whether you are using Vnav or not). With Vnav armed, the FD will guide my pitch to this airspeed. But if you don

[Jeff Nielsen 1,385]

I use VNav all the time actually. the point of the original post was not having any speed automation, which I do now...lol.Now, a few hours ago I did a SFO-SEA run up I-5. Everything went great until I got to the ground. Granted the winds were a Son-of-a-omitted for content., however I couldn't get the a/c on the ground. It just wanted to balloon all over the place. Had to go around and the same thing. I finally managed to slam it on the ground. I've never had that problem with the 747 before. I let it fly itself down to about 150 feet or slightly higher. I even tried disco'ing the A/T all together and it still wouldn't let me retard the speed.Anyways, I'm a bit baffled to say the least.

[Guest D17S]

Ahh, I feel a test flight coming on. Vnav handles all that transition speed changing, so I never noticed what rate occurs as my target speed increases at 10K. We're really spoiled here. That's why this V/S topic seemed so interesting. And now this? I must be living right. Vnav initiated climbs can have that same dramatic effect. Hang on back there!

[Jeff Nielsen 1,385]

Sam,Any idea why I couldn't disco the A/T on landing?I pressed the switch on the MCP as I've done a hundred times before...lol.I guess I wanted A/T again and now I have it...lol.

[Guest D17S]

I'm a systems guy so hand flying really doesn't do much for me. However there have times where I have been so out of whack on an autoland that I just disco everything and try to save it by hand. Boy, that's last resort! But I have had similar experiences. It's a real button pushing drill in the sim. I have the AP disco mapped into my controller, but that darn AT sticks me every time. Thrust just won't retard. As I'm finally giving up and going around, I've though to myself" "Dang. What just happened?" They just love that on Vatsim: "Can we call you a fire truck?" I've always thought that it was just my poor button pushin' skills. Hummm, maybe not. Try disarming it with the AT arm-disarm switch on the MCP. Then watch the left FMA. That FMA positively needs to go blank. Experiment at altitude getting it to disco and then reengage. There is also a setting in PMDG's drop down menu that either allows or prevents throttle inputs from over riding an engaged AT. Might see how that effects things one way or the other. But for sure, mousing around over that MCP at the last seconds of an emergency situation is tough. I need to find a button to set as my AT disco key. . . then make sure it's gonna work. (BTW, the regestered version of FSUIPC is a good way to map in buttons to a controller. Works fine. "Set and forget".)

[Jeff Nielsen 1,385]

Sam,Yes I was on VATSIM...LOL, and go arounds don't happen very often for me (grins). I was not happy.I was using the switch on the MCP, that's what baffled me as to why I couldn't get a disco. As I was re-reading the above sticky post on the subject at first I thought that the only way to disco it was using the thumb screws on the throttles, until I read a bit better.In any case I should have been able to disco it just fine.I must have some gremlins in that 47. Maybe she's been feeling neglected because I've been flying the 37 for so long...lol.

[Guest lespindo]

VNAV all mighty !!!! = lots of hours of study and training. even for the most experienced... Changing altitude from 30,000 to 36,000 in V/S not a good idea!!!! specialy in speed convertion.( mach ).