Auto Pilot '737 Pilot in Command'

[martinboehme 492]

Phil,I'll chip in as well with a few comments...Tim has already given you a pretty detailed blow-by-blow, but your own description of what you're doing doesn't sound too far off the mark either... there are a few points that aren't quite standard (I'll get to those in a moment), but your procedure should normally work too...At this point my number one suspicion for why the autopilot won't engage is that you're not trimming the aircraft out. At the point when you engage the autopilot, you should be able to let go of the stick and the aircraft should maintain the attitude commanded by the flight director for at least a few seconds. If it doesn't do this, trim it out first (keys 1 and 7 on the numerical keypad) -- the autopilot won't "accept" the plane from you if you're holding pressure on the control column.If it still doesn't work, please tell us what autopilot mode annunciations you're getting on the PFD -- this will help "debug" the problem. A screenshot would be even more helpful.To make things as simple as possible, I would suggest that you skip programming a route into the FMC for now -- then when you've sorted out your autopilot problems, you can tackle that next step (though what you're doing sounds pretty much spot-on). The autopilot will work quite happily without a route, just use heading mode instead of LNAV for the moment.Just a few points I noted on your procedure: As you'll have noted from Tim's description, the standard autopilot mode for takeoff is TOGA. (The screw he mentions that you have to click to activate TOGA is located to the left of the autothrottle switch.) If your autothrottle is armed, this will also set takeoff thrust for you automatically (no need to fiddle with thrust settings yourself). TOGA will command a pitch attitude to climb out at the speed you've set in the autopilot speed window (which should usually be V2+10).Vertical speed mode, which you're using, would also work, but is risky -- the aircraft should be able to do 2500 fpm initially, but as you climb, the aircraft's climb capability decreases. At some point (especially for high gross weights on a hot day), the aircraft will no longer be able to maintain 2500 fpm and the airspeed will start to decay. If you're distracted and don't notice this, the autopilot can take you right into a stall (VS mode doesn't have speed protection).Also, on the first segment of your takeoff, you want to be climbing at the maximum rate you can achieve -- which is hard to do using VS mode (you'd have to do a lot of "hunting" to find the correct VS). Much easier to just hold V2+10 and take whatever rate of climb results.Anyway, hope we help you get this sussed soon so you don't have to stay up till four in the morning again (hmmm, sounds like you were exceeding your duty time there... ;-) ).Martin

[Guest Pinkgin]

Martin,Thank you very much for all that information! It is most kind of you and Tim to put so much time into this for me. I never got a chance to try all of this yesterday but I'm sure going to do it today. I have printed off both yours and Tims advice and will have it next to me when I set up. I had no idea that the FMC did not have to be set for each flight!You say that a screen shot would be good ....?? How would one do that? If I have no luck today I will have to come back to you regarding that!(the screen shot)Many thanks again.Phil

[Timvee 0]

Phil,Try Martin's approach first 'cos it's simpler; and if that works it is 99% certain the full FMC thing will.BTW we've all been in your position. That's why many simmers start to get irritated when people call it a game ... it's a little too complicated for that:-hahTim

[martinboehme 492]

Phil,to make a screenshot, press the "Prt Scr" (print screen) button on your keyboard. This will copy a screenshot to the Windows clipboard. To save it to a file, use Windows Paint or any other image editor and do "Edit / Paste", then save the image.Cheers,Martin

[Timvee 0]

Just a thought Martin, if Phil needs to take a screen shot, at what point would it be best to do it to give us the information we need?CheersTim

[martinboehme 492]

Probably best to do it directly before and after autopilot activation -- so we can see the modes being annunciated...Cheers,Martin

[Guest Pinkgin]

Thanks Tim and Martin,I got the last two messages.Anyway here we go again got the whole day to get this sorted....this is the good thing about being retired so young!!Phil

[Timvee 0]

Good Luck Phil.You'll be flying by lunchtime ...Tim

[Guest Pinkgin]

Hi Tim and Martin,Guess what?..........STILL can't get it to work!!Right this time I set flaps at 10, kept my heading as given straight ahead, turned on FD and and A/T for 250. pressed TOGA. The engines rev's ended up at about 96%, I let go of the breaks and took off at 140 I held 12.5 degs and did a nice steady climb set the green light on heading, I passed 1000ft tried A/P and in a second the plane wanted to dive this was even when the command bars were nice and steady! I took of the A/P and regained my control. I tried to engage the A/P many times no luck! so eventually when reaching 20,000ft I leveled off and trimmed the plane so that the flight was dead steady at 20,000 and level..there was hardly any movement up or down I thought it was just set perfectly so I again set the A/P and immeadiatly the plane went into a sharp dive???!!! I have done this again and again and it just will not work!!..........Wow! this 737 is HARD to fly!!!Phil

[Timvee 0]

Phil, Give me a little time and I'll try and repeat this on mine. At least it seems we have narrowed it down to an a/p problem. In the meantime try doing it with a properly programed FMC with the steps I gave you earlier.Tim

[martinboehme 492]

Phil,what were your autopilot mode annunciations (those on the PFD as well as the green lights lit up on the autopilot panel) in those two situations, both immediately before and after you engaged the autopilot? Can you make screenshots as described earlier?The value of 250 that you dialed into the speed window for takeoff is too large, it should be set to V2+10, so somewhere in the range of 140 to 150 knots.When you had the aircraft level at 20,000 feet, what flight director modes did you have set up? Were the command bars centered?It really would be helpful to know what the autopilot modes were. Again, screenshots would probably be best... of course, there's always the possibility that you have a corrupt installation...Martin

[Guest Pinkgin]

Thanks Tim,I just have done that did my trip from Heathrow to Brussels, I had to fly the whole way the manualy....the Autopilot would not engage..the usual problem! Dive dive dive!!!Cheers Phil

[Timvee 0]

Phil & MartinJust tried it on mine. It happened (the dive!!) as on Phil's plane, BUT only when the altitude hold button wasn't clicked AFTER CMD mode was clicked.I had the speed light on, heading light on, but the altitude light had to be 'manually' clicked.If you're still struggling Phil, try it again making sure after engaging A/P that you count 4 green lights - CMD, ALT, HDG, & A/T and if one of them's missing, click it to bring it on.As a matter of interest can you change heading with the heading dial?Tim

[Guest Pinkgin]

Hi Martin,Going to try the screen shots. I honestly can't remember what was showing, what I do know is that the command bars were perfect at 20,000! Cheers Phil

[Guest Pinkgin]

Thanks for that Tim,That figures! I never had the ALT HOLD on during any of the attempts today.And yes I can change the heading with the heading dial.CheersPhil