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Sim-A 737 Rotate Problems

 
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Nige



Joined: 04 Feb 2016
Posts: 37
Location: Lincoln, England

PostPosted: Thu Oct 27, 2016 3:22 am    Post subject: Sim-A 737 Rotate Problems Reply with quote

Hi guys,
I was wondering if somebody could help explain what I am doing wrong with setting up the Sim-A 737 for flight.
After progaming the FMC for a flight in my Jetmax 737, whenever I reach Vr, I naturally pull back on the yoke expecting the aircraft to left off and continue the climb but as soon as the aircraft leaves the runway, the aircraft stalls and nosedives back in the deck.
I use PFPX to create my flight and load it in to the FMC which is never a problem. I set the ZFW and fuel loading, and let the FMC calculate trim settings and V speeds. These are all accepted but when ever I line up, advance the throttles 40% and then hit TOGA, I accelerate along tow V1 and Vr and the aircraft lift off and then nosedives straight back into the deck. I am wondering what on earth I am doing wrong so could anyone give me any tips as to what I should be doing?
I have also used TOPCAT and loaded in the Sim-A 737 TOPCAT config file. Entered all of the weights manually and even set the ZFW manually; been given the trim and Vspeeds from TOPCAT, used these in the FMC and still nosedive back into the runway at Vr.
I've tried so many times and its beginning to be a little embarrassing now so if anyone could help, I would appreciate it greatly.
Also; could anyone tell me what the term "FIELD" means where I would be expecting to see the climb levels?
Thank you
Nigel
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lulu47



Joined: 17 Mar 2016
Posts: 106
Location: Brussels Belgium

PostPosted: Thu Oct 27, 2016 5:22 am    Post subject: Reply with quote

Hi Nigel,

It is just a problem of piloting skill on takeoff roll and also it seems that you forget to switch on the FD switch (Flight Director), all your preflight preparation are correct.

Before to leave the gate or pushback, the FD switch must be ON, then when you engage TOGA or advance manually the throttles to the takeoff thrust for takeoff, once reaching VR, pull back the yoke to lift off but soon as the aircraft leave the ground release the yoke progressivly forward accordingly with the FD bar which give the pilot the correct climb attitude, this allow the aircraft to accélerate to V2 +20 kts. If you maintain the yoke (as I can read) in the same position that those of the lift off phase, the aircraft attitude is higher that the FD bar, so the climb speed stay arround or below VR and because you have not enough speed the aircraft stall.

Daniel
_________________
Former Sobelair and Virgin Express Flight Dispatcher

737NG Full DSTD MX - FDS Shell - FDSB737NG-NS6-LINER - FDS CB-Walls - IPECO CA/FO Seats
FSC Motorized TQ
Dual Opencockpit Yokes
Sim-Avionics V1.964
P3d V4.3
FSUIPC 5.15
Dual PC Windows 8.1
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Nige



Joined: 04 Feb 2016
Posts: 37
Location: Lincoln, England

PostPosted: Thu Oct 27, 2016 9:29 am    Post subject: Reply with quote

Hi Daniel,

Thank you for your reply. I do have both FD switches set and the auto throttle engaged. I activate LNAV and have HDG engaged aligned with runway heading. I will take more note on releasing the yoke after lift off.

Do you also know what the term "FIELD" means when calculating take off settings and how would this equate to the climb settings in the FMC?

Thank you

Nigel
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Winstonc



Joined: 09 Mar 2016
Posts: 407
Location: California

PostPosted: Thu Oct 27, 2016 11:55 am    Post subject: Reply with quote

Nigel,

I assume you are setting the trim to what the CDU suggests?

David
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MichaelYSSY



Joined: 06 Jan 2015
Posts: 663
Location: Sydney - Australia

PostPosted: Thu Oct 27, 2016 7:45 pm    Post subject: Reply with quote

Nigel

Try ditching all those addon programs and figures and try using the Sim Avionics CDU to calculate all your TO figures
ZFW
CG
TO Trim
V1, Vr and V2

Try flying the aircraft as the Sim Avionics CDU suggests and see if you still get the stall at TO (I use CDU figure pretty much every flight and have no issues 737)

PS important not to over rotate but smooth rotate and rate TO about 15 degrees.

Let us know how you go with this.

Cheers
Michael
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lulu47



Joined: 17 Mar 2016
Posts: 106
Location: Brussels Belgium

PostPosted: Fri Oct 28, 2016 6:38 am    Post subject: Reply with quote

Nigel,

Field = runway lengt available.
The FMC calculates "balanced rwy calculations" (balanced field speeds) but does not take into account runway details such as but not limited to:

•Slope
•Stopway
•Clearway
•Obstacles (Most important!)
•Intersection details (unless entered as a shift)


Take a look here to understand, hope this will help you

http://www.pprune.org/tech-log/527182-boeing-fmc-v-speeds.html

http://www.avsim.com/topic/417334-guidetutorial-takeoff-performance-in-the-777/

Daniel
_________________
Former Sobelair and Virgin Express Flight Dispatcher

737NG Full DSTD MX - FDS Shell - FDSB737NG-NS6-LINER - FDS CB-Walls - IPECO CA/FO Seats
FSC Motorized TQ
Dual Opencockpit Yokes
Sim-Avionics V1.964
P3d V4.3
FSUIPC 5.15
Dual PC Windows 8.1
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Nige



Joined: 04 Feb 2016
Posts: 37
Location: Lincoln, England

PostPosted: Sat Oct 29, 2016 4:23 am    Post subject: Reply with quote

Hi Guys,

Sorry for my late reply. Man Flu!!

I will only use the Sim-A CDU for settings and see how I get on. I have been using the all of the CDU settings.
It seems a little strange though because whenever I fly for real which is pretty regular, as a passenger of course, when the aircraft rotates, the AOA always seems to be very steep, a lot more than 15 degrees say, or am I imagining this?

Daniel,
Thank you for the "FIELD" explanation. Can you also explain what "STRUCTURAL" means for the climb code?

Thank you for your help

Nigel
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lulu47



Joined: 17 Mar 2016
Posts: 106
Location: Brussels Belgium

PostPosted: Sat Oct 29, 2016 5:14 am    Post subject: Reply with quote

Nigel,

I'm pretty sure that you will never crash anymore if you apply the correct procedures for takeoff.

If you pull the yoke fully back to lift off and maintain it so, soon as you have a positive climb, your AOA will be greater than the one indicated by the flight director bar, you will have a rocket climb angle and you will stall immediately because your speed will be smaller than VR so not enough lift, at 35ft your speed must be V2 + 20 kts. Same crashes happens with snow on the wings, not enough lift.

See the links below, just apply...

http://www.flaps2approach.com/journal/2014/8/4/boeing-737-800-takeoff-procedures-simplified.html

http://www.flaps2approach.com/journal/2012/7/7/flight-path-vector-fpv-explanation-and-use.html

Try and let us now

Daniel
_________________
Former Sobelair and Virgin Express Flight Dispatcher

737NG Full DSTD MX - FDS Shell - FDSB737NG-NS6-LINER - FDS CB-Walls - IPECO CA/FO Seats
FSC Motorized TQ
Dual Opencockpit Yokes
Sim-Avionics V1.964
P3d V4.3
FSUIPC 5.15
Dual PC Windows 8.1
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MarkHastings



Joined: 18 Jan 2006
Posts: 938
Location: UK

PostPosted: Tue Nov 01, 2016 6:50 am    Post subject: Reply with quote

Silly question - but it's not mentioned...
Are you selecting TakeOff flaps ? (1 or 5)

Also the speed of rotation is important.
The Stall warning is also triggered using the Angle of Attack.
Pulling the nose up too fast will result in a large AOA which could trigger the stall warning.
You would also run the risk of a tail strike.

Once a positive rate of climb is established you would be looking for a 15-20 deg pitch to control the acceleration and maintain the V2+20 Issue speed.
(If you had VNAV armed it would adjust this up to V2+25 if required)

* The FD bar is not used for guidance during the initial rotation phase, because at that time the F/D's do not have enough data to calculate the correct pitch.
Once the initial rotation has stopped and a pitch attitude is established the F/D can command the pitch to maintain the target speed.

At Acceleration height you would select Flaps UP speed on the MCP. (Or VNAV would do it automatically)
You would now be looking to reduce your pitch to around ~12 degs to establish an acceleration trend.

At thrust reduction height (1500RA) you may need to continue to pitch down to around 10 degs to maintain the acceleration trend as the thrust is reduced to CLB power.

The actual target pitch will vary depending on the aircraft GW, airport elevation and any selected Derate.
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Software Developer
Sim-Avionics
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Nige



Joined: 04 Feb 2016
Posts: 37
Location: Lincoln, England

PostPosted: Tue Nov 01, 2016 1:28 pm    Post subject: Reply with quote

Sorry for my late reply guys but I've been travelling back to the desert so there goes my flying for another six weeks 😭
My last flight before I left ended up with another stall. I do have flaps 1 usually set or flaps 5, whichever Topcat has intimated. Somebody said to ditch all these external programs and just use the CDU. If that's the case, how does the CDU suggest the flap setting as it's always blank and doesn't self populate like the ZFW and trim. Also, how does the power and climb settings work? Should I leave these to what they are set to when first selecting the LIMIT page as there is nothing to tell me what to de-rate to and what climb to use, also what flex temp to use. This is why I've been using Topcat to give me these values and Mark has created a config file for Topcat, which I use. So it's all a little confusing which I should use and I would like to use the system as it's intended. Sorry for sounding so dumb but it is rather frustrating to go through all the setting up only to plough back into the deck at takeoff. I've even switched the crash detection off because of it. What should I do guys?
Thanks
Nigel
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MichaelYSSY



Joined: 06 Jan 2015
Posts: 663
Location: Sydney - Australia

PostPosted: Tue Nov 01, 2016 4:44 pm    Post subject: Reply with quote

Nigel

Sorry, my suggestion to ditch the external flight planning programs was to check and see if you are they were the cause of your problems (supplying you with incompatible data). The weights and loads form your flight planning software and your FS Aircraft have to MATCH for everything to work out okay.

There can be a number or issues with this but obvious one is premature rotation.
The CDU works with the Sim A aircraft and knows what fuel is onboard and ZFW, just pick a flap setting (adjust it to reflect runway length and obstacle clearance) it will work out CG, Trim, V1, Vr and V2 for you. Yes they are balanced figures and not perfect but will get you up into the air safely. In all the times that I have used the CDU for TO Data I have never had the Simulator Aircraft settle back on runway or stall and crash.

Personally I start pulling back on the column about 5kts prior to Vr (I read that in a Manual somewhere) it seems to work for me.

Cheers
Michael
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Nige



Joined: 04 Feb 2016
Posts: 37
Location: Lincoln, England

PostPosted: Tue Nov 01, 2016 9:40 pm    Post subject: Reply with quote

Hi Michael,
Thank you for the reply. I will endeavour to rotate at the correct point and be not too aggressive with it.
I will use the detailed notes that Daniel has prepared which are brilliant by the way! Thank you for that Daniel, very helpful and informative.
My only problem now is having to wait six weeks before I can use my flight deck again..........the agony of real life!!

Thanks for all your help guys

Nigel
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