787 Slats Drive malfaunction

[HF1931]

Hello,
I would appreciate if anyone can help me on this issue.
On 787, in case of "SLATS DRIVE" malfunction, we extend only flaps with flaps lever down to 20.
If this malfunction took place when the flaps were set to Flaps1, after the non-normal CHKL is completed, can I decrease airspeed down to the Flap5 speed bug displayed on the instruments when I set Flaps5, without slat extention for Flaps1?
I am not quite sure if the Flaps speed on the speed tape is calculated considering the NO-SLAT status or not.
Thank you very much in advance.

[BleedingOn]

Two issues here. If as you say the failure occurs at flap 1, your wing will be midrange slats and no flaps, so you will effectively be in normal flap extension down to flap 20.

Second issue, to cover any non normal flap/slat issues, I’ve been trained to select the flap position first and wait until that configuration is reached before decelerating to the appropriate speed. This should cover the case where you select flap 1 and get slats drive message then ie you’re not going to get any slats.

Hope that helps

[HF1931]

Hello, BleedingOn!:)
Thank you for your reply.

As for the position of the slats, I would like to assume that no slats are extended because SLATS DRIVE malfunction took place in the Flaps 1 sequence (Slats will never be extended afterwards because ALTN flap system is prohibited by CHKL).
With this situation, the minimum speed will be Flaps up speed.
The final flap for landing is flap20, and the target speed for it is described in the CHKL.
My point is, what speed should I choose for flap 5. Can I reduce the speed to the Flap5 speed bug shown on the airspeed indicator with no slats?
Or the Flap5 speed is calculated considering the no slats condition and enough margin is added to the normal Flap5 speed in this case?

I hope I could clarify my question.
Regards,



Two issues here. If as you say the failure occurs at flap 1, your wing will be midrange slats and no flaps, so you will effectively be in normal flap extension down to flap 20.

Second issue, to cover any non normal flap/slat issues, I’ve been trained to select the flap position first and wait until that configuration is reached before decelerating to the appropriate speed. This should cover the case where you select flap 1 and get slats drive message then ie you’re not going to get any slats.

Hope that helps

[DogSpew]

The SLATS DRIVE NNC caters for all conditions of LE Slat position such as fully UP, MID or FULL EXT and anywhere in between. In other words the NNC doesn’t care where the Slats are positioned, but it's written for the worst case scenario of LE Slats fully UP on one wing. In your example we’re assuming that all the LE Slats are still UP, and the Slat Drive mechanism failure occurred at the initial selection of Flap 1.

As you quite rightly say the NCC prohibits the use of the ALTN Flap system, and therefore the TE Flaps will still operate normally (using the Centre Hydraulics System), however we must use Flap 20 for landing (and in your scenario the Slats remain UP). The NCC uses Flap 20 at a Vref30+30, and this therefore provides a higher approach and landing speed above the normal Flap 20 Vref. This higher speed reduces the pitch angle of the wing sufficiently for a Slat UP condition, and restores near normal manoeuvring margins with normal aerodynamic control response.

Your question seems to me to ask whether you can reduce your airspeed according to the flap extension schedule. Well YES you have to, to be able to reduce to your Vref30+30 bug speed with Flap 20.

Flap UP is Vref30+80

Flap 1 is Vref30+60

Flap 5 is Vref30+40

NNC is Vref30+30 at Flaps 20

Flap 20 is Vref30+20 (this indicates that the NNC speed is approximately 10kts higher than the normal Flap 20 Vref)

The FCTM is a great guide and does describe this condition (FCTM 8.13-8.14). As the TE Flaps are still operating in the ‘Normal’ mode you may reduce speed and extend TE Flap according to the normal Flap Extension schedule (FCTM 5.7). However, as 'Bleeding On' has stated above you could also follow the FCTM advice for Flap Extension using the Secondary or Alternate system (i.e. extend TE Flap and wait for the TE Flap to reach its selected position before reducing speed below the previous bug position). The FCTM does state however that this method is recommended for conditions when the TE Flap system is operating in the Secondary or Alternate modes only, and is due to the slower extend speeds and longer times to reach their set positions.

For me personally (if faced with this scenario - LE Slats UP), I would fly the approach more conservatively and wait for the TE flaps to reach their next position before reducing below the previous bugged speed; and of course in reverse if flying a Missed Approach and retracting Flaps. But that's just me!

Hope that helps.
DOG

[plhought]

You could always ask an FA to look out the window as well....

[DogSpew]

You could always ask an FA to look out the window as well....You could do this but I ask - Why?

To me this would be irrelevant and possibly lead to confusion between the cabin and flight deck. This is no criticism of cabin crew, but I doubt if many Cabin Crew could describe in plain words to me on the flight deck if the LE Slats were UP, MID, FULL EXT, any position in-between, or if there’s a LE Slat Skew amongst the 12 LE Slats.

I also say irrelevant, as at the moment the SLATS DRIVE EICAS is annunciated the Flap Indication system changes from the ‘normal’ (simplified) Flap Position Indicator to an ‘expanded/split’ Flap Position Indicator, which clearly shows you the position of the LE Slats and TE Flaps on each wing. No need to get a visual confirmation as it’s right there in front of you.

Also as explained previously, the SLATS DRIVE NNC doesn’t care where the LE Slats are positioned. There can be a Skewed Slat, Asymmetric condition, or all UP or any position down to FULL EXT. It doesn’t matter to the NNC, or how you complete the configuration, approach and landing.

DOG

[de facto]

You could always ask an FA to look out the window as well....

Right...can we stop with this nonsense once and for all?