I think that was quite easy to realise, thanks. Also in English there are ranges of similar implements called shears, for garden use, sheep, surgery, dressmaking, metalwork ...

It appears that some of these translations have been done by automatic means, perhaps sometimes two or three times successively.

"B737 trim does not work the same as small aircraft trim. In small aircraft you trim out the forces. But in B737 which has THS, you do not necessarily trim out the force. As a matter of fact, you can have the control column in neutral position with no force, while the THS is being trimmed hard forward and not feel anything on control column."





Actually to some degree, this is true. You still trim out the control column forces, but for the most part, the yoke remains centered when trimmed. In a light ac, you are changing the position of the elevator and yoke with trim changes.

Confirming what ManaAdaSystem has said, and for the avoidance of all doubt, flydubai policy is that dual-autopilot approaches are not approved and must not be utilised. Furthermore, the use of dual-autopilots is part of the 'data monitoring' process and it is therein possible (retrospectively) to determine if dual-autopilots have been utilised. The last FZ pilot who took it upon their-self to utilise dual-autopilot's for a landing was sacked for wilful breach of company SOP. Whilst a single autopilot might be utilised for part of an approach, at some point during said approach, that autopilot (and the auto-throttle) is required (SOP) to be disengaged and accordingly all landings (regardless of them being either category I/II/III) and go-arounds (in flydubai) are therein flown manually; albeit always possible for a pilot to re-engage an autopilot and the auto-throttle at some point during a go-around (subject to all the normal engagement criteria).

Let's say they went around for Windshear. As they pull up, they meet a greatly increasing head wind component.

The GA starts, and from what I've read, a 737 pilot has to push, and trim forward, especially with a light a/c.

So: pushing forward, would make the THS trim nose down on a 737? (it does on the non-Boeing type I fly).

Full power causes nose to rise due to engine thrust line below the wing, so more nose down trim to stop it rising too much.

Extra energy from increasing HWC, would tend to need nose down trim as ROC increases as aircraft meets rapidly increasing headwind.

Generally high ROC with full power and while hand flying might cause PF to trim forward to reduce the ROC.

Reaches GA standard level off alt.

As they level off, thrust comes right back, reducing that upward thrust moment, and causing the a/c to go nose down with THS already almost full forward, nose down.

They are IMC, so miss the gravity of the situation for a few seconds (some distraction or other).

Big ROD develops.

Come out the bottom, see the ground,but too late.

SLF: where does the bank angle come from and would that be hard to notice?

Great article here - explains what that pesky stab trim actually does. When I saw the first video of the high ROD crash following the beginnings of a GA, my mind turned immediately to this, as well as the Bournemouth ThomsonFly incident:

Roger-Wilco | Do you really understand how your trim works?

I've not read the rest of the thread so forgive me if this has been answered already but you're not exactly right.

As a 737 air tester it is standard to brief the use of power to recover from an out of trim nose low attitude. Especially in a low speed scenario it is one of the first things I would consider (and it works) if my primary pitch control isn't as effective as it should be.

Reducing thrust with an aircraft out of trim nose down is the last thing you want to do.

Firstly, not all light aircraft are the same. The trimmer on a Piper Cub is exactly the same as the 737. And yes, the stick or cc will remain in the same place as you trim forwards, but unless you give a mighty pull on the stick or cc, the aircraft is going south very quickly. So you cannot trim without experiencing stick or cc forces.

And regards this incident, I cannot see anyone trimming forward without noticing the loud racket from the antique trim system, or the sudden pitch down, or the large cc forces required to resist this. The only thing that might make sense is a trim runnaway, that was not caught in time. Remember that if the flaps were still extended, the trim runs at double the rate. Not sure why it would not be stopped, as it is easy to hear and see, opposite cc pressure should stop it, and you can grab it with your hand if you don't mind losing a finger.

The mystery remains. The only thing we can perhaps dismiss, is a stall or a Bournemouth thrust pitch, as the VS, altitude and GS plots don't support these scenarios.

Just to clarify, I'm not saying it was a repeat of Bournemouth, just in the sense that my first thoughts were that it may be pitch trim related.

FWIW- IMO- This has all the hallmarks of the Bournemouth incident and will be exactly where the authorites would be looking for similarities.

https://www.gov.uk/aaib-reports/aar-...september-2007

I couldn't see if it had been mentioned yet or not, so perhaps someone can link to it, or our weather guys could shed some light on the wind changes within the altitude band we're looking at. The wind speed has been mentioned at 600m as being somewhere in the order of 60-70 kts if I recall, but not direction.

On the surface, the wind appears to be fairly steady directionally from 250 degrees, so a crosswind from the right (runway 22), so assuming it veers with altitude, it becomes a stronger, more direct crosswind. This doesn't fit with a rapidly increasing headwind scenario, as the change in direction would to a large extent cancel out substantial changes to headwind component. If the direction remains steady however, then that theory holds water.

The BOH and AMS events occurred where elevator authority was exceeded by a combination of trim and thrust couple largely because they ran out of airspeed. The IAS does not appear to have reduced significantly here, so they would have had enough elevator authority unless there was some problem with the elevator.

Anson
 

You may be on to one of the issues. Here is a quote from the Bournemouth report.

"The trimmed position of the stabiliser, combined with the selection of maximum thrust, overwhelmed the available elevator authority."

If the FZ guys got trimmed one way or the other without realizing it (and I find that hard to understand), this could be a similar situation.

If the wings were pretty much unloaded, quite easily. You need an angle of attack on the mainplane to generate lift in order to accelerate away from the course you’re on. If the aeroplane was in a bunt, which seems to be the case, it’ll rotate about the longitudinal axis and that’s about it, a bit like an aileron roll. This was not a “balanced turn”.

In some ways this is good evidence that something was seriously wrong in terms of stabiliser and/or elevator position.

Old Boeing Driver, my post above was to counter the previous comments about similarity with BOH. If the speed and altitude vs time graphs are true, then IAS never reached a point where this would have occurred.

For all those speculating about active noise reduction headsets, please leave PPRUNE; you are clearly not pilots and have no idea how ANR works.

HUD
 

Do all FD aircraft have a HUD? Is it SOP to always them?

Personally, I'm not a fan of them at all. Ive seen 2 good drivers, in the sim, stuff it all up during a GA (resulted in the loss of the aircraft), trying to recover from an abnormality, when using the HUD as opposed to doing it the way they had been trained for, for the previous 25 years, where the result was never in doubt and the "event" was a non event.

Whether it will be a factor in this accident, i don't know, but so far on this thread, no one has discussed their limitations and it might just be necessary to start, if indeed a HUD was fitted and used.

Aluminum Shuffler
 

I understand. Thanks for your clarification.

Regards.

And if they were then a stall is unlikely.

I initially was thinking about the Bournemouth incident also but as someone else said there does not seem to be a low speed event (from the data that has been posted).

If the leaked CVR transcript is accurate and there are shouts of Pull we don't know if it's because of a stall situation or the aircraft being in an nose down situation and still "flying".

Someone said it appears to have got to (perhaps) the MCP altitiute okay, then suddenly it all changes, this could be that it got there okay as one would expect, or it got there converting forward energy converted into vertical climb rate and then stalled (data so far doesn't seem to suggest that).

So left wondering what would cause rapid descent

Stall
Uncommanded nose down
Fight control problem

I wonder if during the go around if the a/p was engaged and because of the crazy rate of climb the A/P shoved in loads of fwd trim to try and reduce the climb rate, or the pilots did.

Then once the thrust came off reaching altitude they are now left without the pitch couple to the thrust and aircraft nose naturally comes down, but the stab is now fully forward also, with very little Sky available to try and resolve it ?

Never flown a Boeing but many years flying various FBW bus's.

Reading the comments here about pilots mishandeling trim and speed and pitch difficulties during GA makes me think more airlines should be buying A320's instead of 737's.