Posts about: "Flaps (All)" [Posts: 165 Pages: 9]

That was my first thought, I don\x92t like to speculate but it\x92s hard not to isn\x92t it. Perhaps time for Boeing to take a leaf out of Airbus book with regards to incorrect flap settings prior to take off and the config warning? The 738 will only provide a config warning if the flaps are in a non-standard take-off position but will not trigger in the event that the flap setting used does not match that of the performance solution for the given departure (intersection etc). Surely a fairly simple solution of FMC vs flap position. Do any of the 787 pilots on here know if that\x92s a thing? I know it\x92s not on the 738.

*obviously this may be wide of the mark on this occasion, but it\x92s an inherent risk that SOPs will trap 99.999% of the time*

It obviously got off the ground before the runway end and apparently reached 635ft, at which point you'd expect gear up, flaps down, but the opposite has happened.

the before takeoff electronic checklist senses the flap position based on FMC takeoff data input. The checklist won’t display the “checklist complete” icon if the flaps aren’t set, the takeoff configuration warning would sound as takeoff thrust is being set.

To address a couple points raised as best able:

• B787 does have takeoff config warning, but for the flaps will only warn if a valid takeoff flap setting isn't selected - doesn't crosscheck against the FMC, and there is a range of valid settings (UP and 1 are not valid settings)
• Similar to Airbus there is LE Autoslat extension for low speed protection.
• That EK B777 freighter referenced may have been lightly loaded and generally speaking has far more excess thrust than a B787. Intersection takeoff could be quite valid for the former, having flown both I would be much more hesitant (read: not a chance) to take an intersection in the B787 without an incredibly compelling reason even if the OPT says it's possible.

787 driver here. The BEFORE TAKEOFF electronic checklist will not show as completed unless the flap position indication agrees with the flap setting entered into the CDU. If that is missed, a CAUTION is issued: CHKLIST INCOMPLETE NORM as the aircraft lines up on the CDU-entered runway.

Thank you for the confirmation, this is something that is missing on the 738 and obviously therefore if the flap is in a normal take-off configuration it won\x92t warn you if it doesn\x92t agree with that entered into the FMC. Clearly not the issue here if there is such a warning system on the 787.

No speculation as to what caused the crash, but a couple of points. If there was an inadvertent retraction of flaps instead of gear, this could potentially be remedied by reselecting flaps promptly once recognised. Whether the startle factor would allow it is another thing.

If the RAT is indeed out and there was some sort of powerplant issue, ie. double engine failure, I don't think I would be in a hurry to retract the gear either. In fact it may well have been put down again in that scenario.

Regardless, awful footage to watch. RIP.

Hmm. B787 pilot also and with respect, on the B787 (-9 tho) in the sim anyway, wanting an answer to this very question we experimented with setting a flap setting other than the one in the CDU and received no config warning. I believe the config warning system reads the flap position sensors, not the CDU. I am completely willing to be corrected but was quite surprised myself. 🤔

Boeing 744 logic results in acceleration and thrust reduction if flap retraction commences before programmed acceleration height. Lots of the B744 FMC /Autoflight logic seems to have made its way into the 787. If flaps were retracted in lieu of gear and this logic was so, could explain the lack of noise?

Personally I think take off flaps are extended. It's a grainy video but if you compare it to a normal 787 take off, you can see the profile is similar. The 787 has a sleek wing, even with take off flap deployed.

The 787 screams blue murder at you if you take off without flap. I think selecting flaps up instead of gear up is also unlikely.

The gear not being retracted could be due to confusion in the cockpit/workload.

I'm thinking perhaps a take off performance mis-calculation and/or power issue.

777 guy but you\x92re talking about two different things. Unless I\x92m mistaken. You\x92re talking about the Take Off Config EICAS warning. He\x92s talking about the Before Take Off checklist showing as complete, if the selected flaps aren\x92t in agreement with the entered CDU value.

FYI that only works when slats are already in midrange (not up)!
For some back ground: the B777 has autoslats and the B787 has autogap, slightly different.

From Boeing differences handout:

(B787) The slat autogap function is only available in primary mode when the slats are in the middle position and the airspeed is below 225 KIAS. At a high angle of attack, autogap fully extends the slats to increase the wing camber, thus increasing the lift and margin to stall. The slats return to the middle position after the angle of attack decreases. The autogap trip threshold is a function of AOA, airspeed and flap position.

When flaps are up, there is no automatic extension!
On of the items of the stall recovery procedure is: DURING LIFT OFF, WHEN FLAPS ARE UP, CALL FOR FLAPS 1 (memory item!)

Like most Boeings, on the 787 you are prevented from selecting the flaps/slats all the way up in one go by the gate at flap 1. If this was a mis-selection by one of the pilots, they would have been prevented from selecting ALL the high lift devices up in one go by the flap 1 gate. Even if you manage to get the lever to the Flaps Up position then below 225kts you should get Slat-Gap protection which maintains MOST of the lift. I have never tried it personally but that's the operation as advertised by Boeing. Would that provide enough lift to save them...... that is really a matter of debate.

The aircraft may have suffered a power loss of one or both engines possibly by bird strike. I have to say that the B787 is the very easiest aircraft I have ever flown when handling an engine failure above V1. The flight path vector and the flight director in the head up display make finessing an engine failure absolute child's play. Having said that the Boeing 787 performance is calculated right to the limits of legal requirement, so there is no scope for mis-handling. If they failed to select the landing gear up, not due to a flap lever mis-selection, but some another distraction, like an engine failure, then the aircraft would struggle to accelerate to V2 to safely climb away.

The B787 derates are calculated to give an acceptable Vmca in the event of an engine failure. That is to say, if you apply any more power asymmetricly the Vmca criteria of up to 5deg of bank towards the live engine will require more control input resulting in more control drag. Our SOP was - If you need it - Use It! Thankfully I never had to find out.

By way of illustration, on the B747-400, leaving the gear down following an engine failure had the same effect as failing two of the four engines.

Airbus does the same as 737, will only warn you if flaps are not in any takeoff position. The actual position within the takeoff range is irrelevant to the warning.

You're correct, but I'm not talking about the config warning, which will not sound for any takeoff flap (5, 10, 15, 17, 18, 20 for the -9) set. I'm talking about the BEFORE TAKEOFF checklist. The FLAP item on that checklist is closed-loop, meaning it looks for the CDU-entered value and compares it with the sensed flap position. If they differ, the FLAP item won't go green, therefore the checklist won't be completed. If not rectified, as the aircraft lines up (i.e., before thrust lever movement to set takeoff thrust and so nothing to do with the config warning), a MASTER CAUTION and the CHKLIST INCOMPLETE NORM EICAS is generated. Having said that, it's entirely possible that that function is operator-configurable. I'll check up on that.

Just for the record, there is no system on modern Boeing aircraft to prevent the accidental retraction of flaps when too low or slow when airborne. You wouldn't even get a warning on Boeing aircraft that is related to Flaps, you'd eventually get one related to Low Speed or Stall. The Airbus has a safety feature called "Alpha-Lock" which physically stops the Flaps from moving when the AoA or speed? is deemed too low. But that's not a safety net for all flap settings, just the lowest for takeoff. It will save the day in 95% of situations though Mr Boeing (hint hint)

Takeoff config warnings and checklists may not have helped if the flap setting was not enough given the weight and conditions. A good handling pilot could recover from an incorrect flap setting (providing there's no obstacles to deal with), by gently lowering the nose allowing the airspeed to build up before resuming the climb. However, various human factors such as startle and over reliance on automation (my thrust setting must be good) will not help the situation.

In order of likelihood:

1.) Flaps moved instead of gear
2.) Incorrect Flap settings and inability of crew to recover from that
3.) Double engine failure
4.) Some electrical event that distracted them

I just ran a quick performance calculation using our performance tool, albeit for a 787-9, but for the given WX conditions, the given Pax load and minimum Fuel amount for the given stretch and intersection R4. (no cargo load)

In short\x85
Even though the 9 has less TO performance, it seems very unlikely they could have departed in those conditions from less than 2000m with only flaps 5, which is the minimum TO flap setting. IMHO it\x92s impossible to judge from the footage that it left with flaps up (and very unlikely) ? but it certainly wasn\x92t flaps 17 or 18.


*B787 jockey here, but feel free to not believe that

Item 1) On the 787, is the gear lever on the main panel facing the flight crew, or on the centre console? I'd imagine they'd (flap and gear levers) need to be adjacent to each other for that to happen. All good points though.

Main panel. And the handle is a rubber wheel. The flap lever is shaped like a flap. But that hasn\x92t stopped it happening multiple times in the past. The yellow and red lines on the speed tape will start to converge and should be an indication to PF. On all Boeing / Airbus that\x92s it\x92s happened on the pilots have recovered by re selcting flaps. Selecting F1 will save you. It\x92s a Boeing procedure written in the manual.

TE Flaps are extended, flap gaps between the wing and the flap element are observable. This is not an aberration of the spoiler position, you can see the nacelles through the gap, and that means the flap can not be in the retracted position.

An error of the TE flap deployed position, say between flaps 5 or 15 is not going to cause a stall event.

The flap has not been retracted instead of the gear.

Double engine failure... India. birds, always a latent threat. No rudder deflection, no aileron deflection, so it's not a SE problem, any engine issue is affecting both engines.

Pitch control and roll is not compromised in the video. The crew put out a mayday, not sounding like an electrical fault or distraction.

any funerals near by?

Incorrect TO thrust setting would not present in the video as recorded. Low thrust results in low acceleration, and extended distance to rotate. after rotate, low thrust results in low climb rate, and can result in the crew over pitching where the aircraft has obstructions that the crew have to avoid. the video appears to show the pitch increasing at a point where the aircraft is already unable to climb, not the other way round. An outside possibility.

For survivors, any from the aircraft will be a miracle, and mainly from the rear of the plane near door 3 area, if any. Plane is still striking tank traps at 70m/sec +, high ANU, it's not a high survivability event. Occupants in the buildings along the flight path will have a high fatality rate as well. This is going to be a high toll event in the aircraft and on the ground. Bad day at VAAH. RIP.