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Guest dougjc

A couple 737NG MCP questions

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After I start my take-off roll how do I know when I am 40% of NI prior to activating the TOGA switch?Sometimes I push TOGA and the Hdging, LVL Chg and N1 lights on the MCP kick in as expected and all is well. A couple times I pushed TOGA and a different set of functions lighted, take-off was a crash and burn with inadequate thrust after VR. Again, does this have something to with activating TOGA at the right time?TOGA - when would the go-around be used/how?Lvl Change - If I am using Lvl chg should I ever have to use the vertical speed switch? I often find this to be a pain as the accent or decent VS settings seem to jump all over the place each time I use it and I need to keep dialing in what I want. VNAV - seems to have a mind of its own at times when everything looks perfect in the FMC and it will not activate. Mostly below 10000 on descent.Thanks Doug

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I will try to explain how it works in the real world anyway :)1. You will have to look at you engine instruments. You just have to advance your throttles slightly to get approx 40% N1. this is to be sure that both engines spool up symetricly and you dont get a wild yaw because you just pushed the throttle all the way to the fire gate (foreward)When you see the approx 40% n1 you push TOGA only once. the engines spool up to the pre calculated N1. This is to save engine life. If it doesnt work... you put something wrong in the FMC. simple as that. After rotation you maintain 15 degree pitch up and maintain you speed. Passing 1000ft, lower your nose slightly to accellerate the aircraft and retract your flaps. (clean up) maintain 210 on the speed or so while climbing. In the real life you can push TOGA once to get the save enginge life... if toy push it twice to engines gives you MAX thrust.LVL change is used basicly if you need to change ALT by more than 1000 ft. if less... use VS. We dont use VS during climb/descent unless instruvted by ATC or some other reason.Vnav. Make sure that you have the FMC programmed correctly, and be sure that MCP panel is set to the new lower altitude. Vnav use the most restrictive alt put in either the FMS or MCP. They have to agree. or the Aircraft will stay at the most restricted altitude. Hope this helpes a bit. Good luck with your next flight.Kind regards 73-driver

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V/S is also used for example during a VOR/DME approach.From the Final approach fix you start descending at GS (Ground Speed) * 5. f.e. GS = 160kts * 5 = 800'/min descent.I don't think VNAV is very wel modelled in de PMDG737NG. It should work if flaps are set at 15, 15 miles before landing or something like that. Far from real..

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TO/GAas i remember, actual N1 value doesn't affect commanded mode.So you can well activate TO/GA even being at idle.At least for what i remember.LVL CHGvertical speed should not affect this mode which is operated by means of thrust.In simple terms you set an altitude different from actual, then you set a speed.To maintain that speed the plane eighter climbs or dives depending on the actual thrust.Example:commanded speed higher then actual, thrust not sufficient -> divecommanded speed lower then actual -> climbVNAVit is a little buggy during descent, multiple altitude contraints can result in shallow dives and ultimately failing to maintain the vertical profile.During climb it usually performs well.

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"A couple times I pushed TOGA and a different set of functions lighted, take-off was a crash and burn with inadequate thrust after VR."After you hit the TOGA switch, advance your joystick throttle to match the proper takeoff thrust (don't leave it at 40%N1)Cheers.Q> イアン

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Some other things on TOGA takeoffs.The pre-active (and subsequently engaged) lateral mode depends on the first navigation fix on your route.In order for LNAV to engage, the first fix after takeoff should be on runway heading, or a just a few degrees (don't know the exact limit) astray.Otherwise HDG would kick in.And, after Qavion post made me think of it, it could be possibile that jerky potentiometers in your throttle can cause such things as A/T malfunction.Because during takeoff the A/T doesn't hold the throttles, it just position them for the commanded N1 and then un-hooks the mechanical leverages in order to allow for subitaneous retard should the need occur.This is simulated in the software: if you retard your throttle after the A/T has commanded the t/o N1, you'll see the engines spool down.I use FSUIPC smoothing and all is well even if i forget to advance the stick, but problems with harsh axis could occur in that a spike would set the throttle to idle leading to stall and eventually crash if you don't see it in time.

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