Uncommanded Dive

Trim setting is 0.0 deg.

 

And why should this be a problem now when I flew for a number of years previously without even considering my trim?

 

And the trim is the same with the B737 and the A321, with similar payloads, fuel, etc, and I can takeoff with the A321.

My question is why is your N1 button on the autopilot on??? With that lit, you are not setting the auto-throttle to the 240 kph but to follow your N1 input, which is set to 0%.

 

Your airspeed in your last shot is at 124 knots....bad...bad! By that time you should be close to 230 knots and speeding up!

 

Edited December 1, 2020 by mrzippy

On top of the other posters' recent comments on your photos, I believe your SPEED button needs to be activated and the A/T ARM needs to be ON. In the diving photo A/T is on but SPEED is not on. I fly with a Saitek Flight Panel so I don't always pay attention to the aircraft's autopilot panel itself. However I am reasonably for the default 737 both need to be engaged so you do not eventually lose speed with the nose up.

Oops.

 

Just selected speed instead of N1 and smooth takeoff. Can't understand what happened there, I NEVER, EVER, run with N1 set. So not convinced this it the total solution but certainly worked this time. Time for dinner. Will try a few more takeoffs later.

 

Thank you all for your input. Watch this space.

 

 

Allan

My question is why is your N1 button on the autopilot on??? With that lit, you are not setting the auto-throttle to the 240 kph but to follow your N1 input, which is set to 0%.

 

Your airspeed in your last shot is at 124 knots....bad...bad! By that time you should be close to 230 knots and speeding up!

 

Yep, Charlie, N1 set at zero, Speed button not engaged, 124 KIAS in a Boeing 737 would definitely cause a stall. Poor Boeing never had a chance!

 

If Allan did accidentally hit the N1, he could have very well done it at other times, something he needs to pay attention on not doing!

 

Allan, here is my panel during climbout on a default B737-800. I find 1800'/min vertical speed very comfortable in a climbout to higher altitudes, but settings can change with obstacles etc.

 

 

And, a external view of the aircraft for the above panel settings. Aircraft looks very content!

 

And you know what Allan, things are starting to make sense of how it is happening. You had successful flights in the A321 and not in the Boeing 737, why is that? Well, could be that the A321 has no N1 preset! You could have very well have been accidentally hitting that N1 button all along? Make several flights with the Boeing and see if your issues have gone away. We all hope that they have!

 

Rick :cool:

Edited December 1, 2020 by Downwind66

My one last suggestion is to not fly with all tanks full, unless you are making a very long duration flight. Always use the fuel planner to adjust fuel load according to your distance being flown + allowing for reserve.

Allan - Earlier, you were wanting to know why the issue with the B747 and the A350 Camsim.

 

If you look at the panels on both the B737's and the B747's, the vertical speeds are selected in opposite directions!

 

In the 737, you roll up to go down, down to go up

In the 747, you roll up to go up, down to go down

 

This could be something you may doing incorrectly? A vertical speed issue with the 747? Just another thing to pay attention to!

 

As far as the Camsim A350, can't help you there?

Edited December 1, 2020 by Downwind66

Right, thank you all so much for your advice and suggestions. The 124kts was a red herring. Look at the pitch up angle, the aircraft was already in the stall and the speed was falling.

 

It sure looks like the N1 versus Speed selection was the culprit with the default B737 and it's possible I was careless in selection, thinking it was the speed button. I NEVER knowingly use N1. So, thats that problem solved, I think. Now to check out other aircraft and see if I can fly those.

 

One problem throws itself up immediately, and could perhaps be part of the problems with the B747 and the A350. I tried another version of the B738. Takeoff was normal, and prior to my takeoff roll I checked the elevator trim was 0.0 deg. However, as I started to climb out the pitch angle continued to increase and I was having to hold the stick forward to prevent this. I checked the trim angle again and it had changed to +20.0 deg. Now gotta find why this is and this might answer the question with the A350, etc.

 

Allan

Allan - One thing I check once, twice before taking off, what do I want for Altitude and rate of climb after breaking ground, I engage my autopilot early after takeoff, after my gear is up and flaps up, I engage it, then, I can relax and just monitor the aircraft to make sure it's flying the way I wanted it to!

 

The +20 trim is a result of the trim chasing what the aircraft is doing. If you get the aircraft off the ground and get your AP engaged, you won't see that. Then, you can merely sit back and make minor adjustments to climb rate as you see fit. Sometimes when I engage the AP, the aircraft might want to start to nose down slightly, at that point I adjust the rate of climb to 2000 or 2100'/min until I see the aircraft climbing again, then I will adjust the rate of climb back down to the 1800, 1900 or 2000, or whatever toots your horn and makes you comfortable.

 

You are on you way to recovery of figuring this out, now you just need to make some minor changes, such as getting that AP to do some work for you! Keep that aircraft from "wanting to do it's own thing!" Keep at it Allan, you're getting close!

 

Rick :cool:

All noted, Rick. Thank you.

Just a quick update.

 

Elevator trim checked at 0.0 deg before every flight.

 

 

Managed a normal takeoff with the default B747

 

 

A350:

 

1st takeoff with all parameters carefully checked. At about 130 kts the nose lifted without a joystick input. Went in to a steep climb and the elevator trim chased the climb to 20 deg trimmed up. Aircraft stalled and crashed

 

2nd takeoff, same parameters. Nose didn't try to climb until I pulled back on the stick at about 140 kts. It was reluctant to climb but eventually did so and I was able to engage the A/P and A/T for a normal climb out. Elevater trim increased to about 2 deg.

 

???? Confusing. But getting there.

 

Allan

Stick with it Allan! Why are you taking off with no flaps? I usually takeoff with about 10* of flaps on most all of my jetliners, but hey it's up to you, whatever works for you! I'm going to give you a good link for checklists, may or may not help you, but I use them any time flying the "big boys!" Keeps me out of trouble! :rolleyes:

 

http://freechecklists.net/simchecklists.asp

 

Rick :cool:

Edited December 2, 2020 by Downwind66

Hi Rick,

 

Thanks for the link. I wasn't aware that I took off without flaps. But bear in mind I'm only doing trial takeoffs I'm not concerned about details like that. LOL.

 

Allan

Allan - My apologies, I was reading some of your posts you provided. You are correct, you have mentioned flaps, I was reading your reference to Elevator Trim set to 0.0 deg and my mind was reading that at 0.0 degrees flaps, "My Bad", again apologies for that! I won't get into elevator trim, that is all personal preference according to the task at hand!

 

I think you are very close to getting these aircraft under control! Just keep at it. When it all comes together and you feel good about it, you will ask yourself, "Why me?" I guess we learn by the tests that are thrown at us? You'll get it!

 

Good luck and happy flying!

 

Rick :cool: