B-738 Crash in Russia Rostov-on-Don

[737er]

The weird vertical speed gyrations aren't unheard of when the autopilot is controlling the aircraft in low level turbulence. It flies like a piece of cr@p. It wouldn't be unusual for a pilot to disconnect and fly an average pitch attitude through it and accept a small amount of speed deviation.

True. Especially if you manage to get the AP to engage in a dynamic siituation.

[framer]

Whatever the stab position/angle how come pulling ("pull,pull,pull") back on the CC doesn't raise the nose even one inch?

What I was getting at above is that there may be limits to the 'power' of the elevators relative to the 'power' of the hori-stab. The elevators are small compared to the stabiliser, so if ( due to a reason I won't speculate on) the nose of the aircraft was allowed to get to very low attitudes (-20? -30? ) then do the elevators have enough power to correct the situation from that altitude?
I'm not at all convinced that this is what happened, I was just surprised that with all the technical discussion around the pitch control of the aircraft nobody had mentioned the STS.

[silvertate]

Originally Posted by Alice025

No 2 is "knuppel". It's a computer mouse round ball whatever it corresponds to in a modern airplane.

Since the trim switch is a rocker switch, rather than a true switch, is is possible this refers to the trimmer.

[PBY]

What if the aircraft climbs rapidly on the autopilot with a lot of power. Than the AP captures altitude quite abruptly. It has to pitch quite hard nose down. The stab is trimmed hard nose down and at the same time power comes agressively off to keep level. Than AP disconnects. Stab is trimmed down. Power goes back. It is a huge nose dow moment.
You try to pull the yoke, but the small elevator is aerodynamically hidden behind the huge stabilazor. You try tu pull, but nothing happens. At the moment you have too options. Either add a lot of power to get the nose up or trim fast like hell. I am not a Boeing pilot. Does that make sense? May be trimmimg would not be fast enough to get yourself out of it. You would probably need to add a lot of power.

[PBY]

The Go around altitude is 3240. So if the power was kept on, the AP had no other alternative than to pitch down very hard. Because of the nose down parameter being exceeded, the AP disconnected. The airspeed increased a lot.
So when the AP disconnects the pilot powers back to get the speed under control. What a set up trap!

[PBY]

The GA altitude seem to support my theory. As the problem started around that altitude.

[de facto]

if your nose is stuck way down(stab down)last thing is to add thrust which will just add the downward energy,speed increase and even harder to pull out.
Adding thrust for pitch up works wonders when in trim condition not in that scenario.
You need to get back to the speed at which it was in trim,reduce thrust which will allow the elevators more control over the jammed stab.(less manual force required).

[PBY]

I slightly disagree. The engines are mounted below the centre of gravity. So immediate hard power starts pulling nose up, even though the increase in speed is counterproductive. But I still think that full power is quicker and faster way to get the nones momentarily up that could buy the pilot some time whlie trimmimg hard up. If that's not possible, than it is a fatal trap!

[PBY]

As I say, I don't fly the boeing. But there was a fatal accident like this on a Airbus. They forgot low altitude selected, something like 1500 feet. But it spdoes not matter what altitude, if you sleep through it. Does anybody know, when that accident happened? It was fatal too.

[Util BUS]

In reference to some of the points mentioned above.

On the ATC recording at time 5:58 the crew advise in case of a go-around they will climb to FL80.

The B737-800 FCOM 2 Section 4.20.2 states that the auto pilot will disconnect automatically in case of:

Pushing TO/GA on a single channel approach:

- Below 2000 ft RA
- with flaps not up or
- G/S engaged

Also if they had a STAB Trim runaway it would have been obvious to the crew from the sound of the trim wheel and would be quickly discovered by the investigators given the associated sounds on the CVR.

I would be much more inclined to believe it was due to tailplane icing such as in the
October 1994 American Eagle ATR72 crash which was further investigated in NASA's Tailplane Icing program of March 2000.

[PBY]

I understand they wanted to climb to 80. But they were not cleared for it, as far as I know. What if they forgeot and left the GA altitude at 3200, but in their mind they were climbing to 80? Would not that be a big surprise surprise as the autopilot leveld out with hard nose pitch down?

[iggy]

I have been reading the thread since the very beginning and, my two cents, when (the Captain) says "don't worry don't worry" at 3.600' he may be referring to the GA final altitude (3240') overshooting by 250'. It is true that in a high thrust and light weight situation an altitude boost is not that uncommon but maybe this GA altitude boost, if such, may point to a possible AP/trim/FD malfunction that lead to the subsequent pitch down.

What can be hear next is: "don't do that don't do that". Whose voice is it? Is it the same voice as in "don't worry"? If so, we can assume it was the Captain who was flying the GA and then asking the FO not to do something specific when he felt something was off. I'm not a Boeing guy, closest I flew to Boeing was MD80, so here is my question: is there any SOP (Boeing or Fly Dubai) that involves two pilots manipulating the flight controls or surfaces at the same time?

Also, what is the SOP in FD when in GA? Accelerate at final GA altitude or at the standard 1.500' AGL or 3.000' AGL when in noise abatement? If they were planning to level off at final GA altitude (3240') after accelerating at 3000' the flight automation might have acquired the final GA altitude way early (IF it is a function of the v/s during climb, as it usually is, but I am not a Boeing guy), if the FO in that moment cleans up the airplane - without waiting for the Captain command - with a lower than required speed for cleaning, is there any kind of protection in the 737 that could have triggered the nose down moment? Is that why the Captain says: "don't do that?", because the FO retracted the flap below the minimum speed?

Does it make any sense what I'm saying here?

[Craggenmore]

Also, the notion that the pilot accidentally held the trim button down to such an extreme degree is something i find very very hard to believe. It is actually quite ridiculous.

AF 447 more or less held full backstick all the way down from FL350 to impact and the AoA was never less than 35 degrees the report stated.

[Util BUS]

At 6:03 the controller responds to their intention to climb to FL80 with "Roger" although this is non-standard terminology I would have accepted it to me "Approved" in that part of the world.

My experience with the B737 especially regarding operators in the middle east, apart from close to landing, it is unlikely the F/O would have been following through on the controls, if at all.

The two possible maneuvers were a standard go around:

Initiation:
- Push TO/GA, Flaps 15
- Verify go-around attitude
- Verify or adjust thrust as needed
- Positive rate of climb - Gear Up
Above 400 feet RA:
- Verify LNAV or select roll mode
- Verify missed approach altitude set
- Verify route tracking
Acceleration height:
- Retract flaps on schedule
After planned flaps set:
- Select LVL CHG or VNAV
- Verify climb thrust
- Verify altitude capture
- Do after takeoff checklist

Or a windshear escape maneuver:

- Disconnect Autopilot
- Press either TO/GA switch
- Aggressively apply maximum thrust
- Disconnect Autothrottle
- Simultaneously roll wings level and rotate toward an initial pitch attitude of 15 deg
- Retract speedbrakes
- Follow flight director TO/GA guidance (if available)
- Do not change flap or gear configuration until windshear is no longer a factor
- Monitor vertical speed and altitude
- Do not attempt to regain lost airspeed until windshear is no longer a factor

[MrSnuggles]

Anything "knyppel" about this?



I don't know anything about the intricacies of a cockpit. This is from a flickr page from a 737NG pilot, as i have understood it.

[GBV]

could flight level 80 be 800 meters? That would be around 3200ft-3500ft which is the altitude they reached during both go-arounds...

[Kulverstukas]

Seems this "CVR transcript" and discussion about stab trim completely put aside previous information from MAK that plane stalled and fell over left wing?

[Daylight Robbery]

I agree, framer. I'm not out, but it's a site for 'professional pilots'. There's some interesting stuff as the awful facts about another accident surface. Would be appreciated if those not flying planes for a living looked and didn't touch.

Regards

[ManaAdaSystem]

The HS on the NG is a very powerful device. If it is grossly out of trim, the elevators are not big enought to get you out of the situation. You have to use the trim as well. Or stop it from happening in the first place.
The problem is this, we are dealing with a system that is not monitored for a runaway condition. Boeing put those big, ugly trim wheels in there, but they live their own life, spinning this way or that way depending on the trim situation. We are used to that, so it takes time to react to a runaway situation. No lady yelling STABILIZER MOTION, STABILIZER MOTION, STABILIZER MOTION on the NG.
Add Speed Trim as framer introduced a few posts ago. That system would most likely have been in full motion trimming down, as it is designed to do, during this go around.
So how are we supposed to discover a runaway trim? After 6 hours flight time, at night, ****ty weather, tired and turbulence. Very easy to miss.
Never heard about a runaway trim on the NG, though.

STS is another weird Boeing system. Most of the time I end up trimming to cancel out this system dueing take off. Why they put it in there, I have no idea.

Iceing? I don't buy that, partly because of that effective HS, and I don't know of a single incident with ice on the HS on a 737. The frozen stab on that Norwegian NG is not applicable for the conditions this FZ aircraft was in. 6 degrees on ground means a lot of any ice would have melted off during approach.

Accidently trimming by hitting the wrong switch?
A. The auto pilot will disconnect if you use stabilizer trim.
B. If you fly manually, you will feel this after a few turns of the trim wheel. It would be very weird if you continue to trim and fight the out of trim with the yoke at the same time.
Unless the PM was trimming? That would be weird too.

There has been a number of near accidents related to level off and pitch down during level off (with aircraft without any defects) as pr the Boeing magazine somebody copied from way back in this thread.

[Util BUS]

STS

Speed Trim System 
The speed trim system (STS) is a speed stability augmentation system designed to improve flight characteristics during operations with a low gross weight, aft center of gravity and high thrust when the autopilot is not engaged. The purpose of the STS is to return the airplane to a trimmed speed by commanding the stabilizer in a direction opposite the speed change. The STS monitors inputs of stabilizer position, thrust lever position, airspeed and vertical speed and then trims the stabilizer using the autopilot stabilizer trim. As the airplane speed increases or decreases from the trimmed speed, the stabilizer is commanded in the direction to return the airplane to the trimmed speed. This increases control column forces to force the airplane to return to the trimmed speed. As the airplane returns to the trimmed speed, the STS commanded stabilizer movement is removed. 
STS operates most frequently during takeoffs, climb and go-arounds.

Conditions 
for speed trim operation are listed below: 

• Airspeed between 100KIAS and Mach 0.5 

• 10 seconds after takeoff 

• 5 seconds following release of 
trim switches 

• Autopilot not engaged

• Sensing of trim requirement