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737 operation

Old 27th Jan 2021, 12:48
  #1 (permalink)  
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737 operation

During lockdown I'm spending time trying to fly the 737-800 via X-plane 11. I'm a retired helicopter pilot with experience of coupled flight in the Boeing Chinook.

I'm trying to fly as realistically as I can but am having trouble with Vnav and Lnav. Could someone tell me the detailed sequence for engagement of RNAV, Auto throttle and the autopilot following 'positive climb, gear up" Do certain parameters of speed and altitude have to be achieved first?

Secondly, on a standard flight (if such a thing exists) at Max weight, and no ATC restrictions, what rate of climb is usually aimed at/achieved passing FL10, 20, 30, TOC. Also is there a standard rate of descent to be planned for/ achieved during a standard descent?

Many thanks, time goes by sloooowly some days
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Old 27th Jan 2021, 13:16
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On the NG LNAV and VNAV can be armed on the ground. Some airlines arm only LNAV on the ground and it will engage at 50 ft, others engage LNAV at 400 ft AAL. VNAV is engaged when Flaps are UP.

For take off, pitch initially to 15 degrees then follow Flight Director guidance.

As for rates of climb, I have never really paid particular attention. We climb at a fixed speed which changes depending on the Cost Index and wind inserted in the INIT PERF page in the CDU. Standard is 250 up to FL100, 280/.78 above.

TOD FLx3+10 works good enough for average weights with a standard descent profile of .78/280/250 to cross check VNAV is behaving.
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Old 28th Jan 2021, 03:38
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Auto throttle is armed pre flight. Usually LNAV and VNAV too (possibly operator dependant as previous post mentions, SOP is to arm both for my outfit). When you take off, you bump thrust up to 40% then hit TO/GA button, you (hopefully) get whatever thrust you asked for in FMC, defaults to all of it if you didnít. Auto throttle engages in N1 mode. Pitch mode becomes TO/GA. No roll mode (LNAV remains armed if you armed it). At 84KIAS auto throttle changes to THR HOLD (thrust levers can be manually positioned). At 50 feet RA LNAV engages, at 400ft VNAV engages. At 800ft auto throttle goes into ARM mode and then at whatever thrust reduction altitude you have programmed it engages in N1 mode and reduces thrust to whatever climb setting you have programmed. You can engage the autopilot above 400ft.
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Old 28th Jan 2021, 10:13
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Autopilot engagement height probably depends on different CAA. For us it's 1000 ft.
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Old 28th Jan 2021, 10:24
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The descent rate is the idle thrust gliding rate. Steepness depends on the chosen speed, the schedule 250/280/M.78 mentioned above for climb works perfectly too. Practically speaking, you do not pick a decent rate, you choose the ToD point. Perhaps at around 5000' AAL 220 kt is prudent for manoeuvring the terminal procedures and no more than -1500 fpm to avoid undue TCAS alerts / inconveniently large thrust changes. When you see the A/C not being able to dive -1500, that's realistic too.

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Old 31st Jan 2021, 21:33
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737

Many thanks gentlemen, just what I was looking for. I hope all is well with you during these difficult times.
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Old 1st Feb 2021, 09:19
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But if you really want to test yourself on your desk top simulator make sure you turn off the flight director and the autothrottle and autopilot and fly it by hand. A ten year old can fly a simulator with all the automatics operating but there is no real life skills to that. . Enjoy yourself and play real piloting - not an automatics "manager."

Last edited by Centaurus; 1st Feb 2021 at 09:48.
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Old 1st Feb 2021, 09:50
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Manual flight

Good thought! I used to fly the S61 helicopter which had no automatics, no flight director, just artificial stabilisation and a heading hold so all IF was hand-flown. I still have memories of ADF/ILS approaches with the stab off in the simulator. Now that was hard work.

So, I have been flying the 737 manually including ILS's. I'm not sure if its 100% realistic as it doesn't seem to hold a trimmed attitude very well. I had no idea about power settings so that was interesting but managed to fly the ILS down to minima without exceeding the limits.

Keeps me off the streets in me old age.
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Old 1st Feb 2021, 11:16
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Trimming an aircraft is done by feel, which is missing in a desktop simulator.
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Old 1st Feb 2021, 12:40
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Trimming

Appreciated. However, with attitude, power, trim, a fixed wing (or stabilised helicopter) should hold the selected attitude and return to it if disturbed. X-plane doesn't. Despite my best efforts it will drift off.
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Old 1st Feb 2021, 12:59
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I am not an expert in flight sims, but I think it depends on the flight model. There are some realistic study level aircraft in terms of flight dynamics and system implementation for various simulators, but they tend to be quite expensive.

It's just like some racing simulators available on PC, with rFactor having the most realistic physics. And if it's anything like racing simulators, also the quality of peripherals play a part.
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Old 2nd Feb 2021, 12:34
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Keeps me off the streets in me old age.
Precisely why I enjoy browsing PPRuNe. Bogans aside there are some very clued up contributors who are a pleasure to read and learn from.
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Old 3rd Feb 2021, 08:54
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Fli Sims

Me neither Joe. I know that X-plane is modelled on the actual flight aerodynamics of each aircraft. From my limited knowledge of software I would have thought it was easier to programme the sim aircraft to maintain the selected attitude sooner than programme something to make it drift off. After 36 years I know something about flying but am still very hazy about computers.

Me too, Centaurus, There's a certain amount of horse manure on here but an awful lot of the good stuff. I rarely ask a question without getting some professional feedback.
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Old 3rd Feb 2021, 16:50
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The very best model to use for realistic flight would be at present the PMDG 737NGx using P3D V4 or V5 and soon the new MSFS FS and the latest PMDG offering for that. As good as the X-plane 737 is with the Zibo mod added, it's not as good a study level aircraft. The 737 Trims through the horizontal tail, so the actual yoke will sit in the same position in trim no matter as the elevators are in-line. Trim changes with power as the engines are low slung. Nowhere near as much force as a turboprop with power changes, but 737 pilots like to think so.... It's really a pussycat to fly, except in crosswind.

Just have fun and enjoy I say, don't worry to much about following an SOP set. If you do go for the PMDG version, get FS2Crew to go with it. Then you can have a helper to move the flaps and gear when you ask. They don't complain, you can select SOP set, voice and gender and at no point do they want to stab you in the back to take your job! Perfect.
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Old 4th Feb 2021, 09:07
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737 sim

Thanks for your comments, RVF. I'm not familiar with the initials in your first sentence but am aware that there are better models. A friend really into FliSim, (he's just bought a Virtual Reality headset,) has recommended the Zibo Mod which I had a crack at last year on a very sophisticated setup elsewhere.

However, I have no idea of how accurately it models a real 737 so I have to rely on those who fly it for real. My last and only fixed-wing flying was fifty-five years ago in a Chipmunk.

Thanks for the info about the 737 trim. I do enjoy flying it (recently Taiwan to Hong Kong) but find it most satisfying to try and fly it as realistically as possible. Which is where I came in.
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Old 19th Mar 2021, 11:40
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Centaurus

i cant agree more, its so pleasant to hand fly the 737 for a visual approach with no FD and PAPI
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Old 20th Mar 2021, 10:02
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Boslandew

If it helps, Pat Boone has done a very helpful guide to pitch and power settings, it should be nice and stable then.

https://b737mrg.net/mrg_download/b73...ngs_737-NG.pdf
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Old 24th Mar 2021, 17:42
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Hi, fellow Xplane user here.
Do yourself a favour and download the Zibo mod 737. Its produced with input from real world pilots to make all the systems, flight characteristics etc as close as you can get on a desktop pc, and its updated very regularly. To say that its free it really is an astounding piece of work. There are also plenty of free add ons to enhance the sim. One of the rw pilots involved with it (Flightdeck2Sim on youtube, well worth watching and one of my favourite channels) rates it above any payware available for other simulators.
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