Issues related to the LE FLAPS TRANSIT

[lechuza]

Hello, Just landed at MMUN, and I was dispatched with a B737-700 MEL 27-1-1, ,and during flight both the #8 slat indicator (aft overhead panel) and the LE Transit Light (forward panel) were flashing on and some time off.During landing configuration upon extension of landing gear and flaps 15, the speed tape began to "shrink", so at selection of flaps 30, there was only about 10 KIAS between top and lower yellow speed bars.And at only about 10 feet about the runway, the takeoff configuration warning horn began to sound until touchdown.Landing weight was about 122000 pounds, and Vref for 30 flaps setting was 129, and for 15 flaps was 133.I choose to use Vref 15 with a 30 flap setting.All was normal during landing with no additional alarms.What caught most my attention was the takeoff configuration alarm as mentioned above.

It is something related with a LE FLAPS TRANSIT or it is maybe another issue related among this flap system and maybe the AIR/GROUND SENSOR.

Thanks, Schaye G.

[ampclamp]

If a prox sensor is giving you trouble, that is false info being fed to the ovhd indication and likely other systems.If the slats / flaps are being sensed as being in a position other than it should be in a landing config, I suspect the speed tape thinks yours slats/flaps are incorrectly positioned as would the landing config logic hence the warning ie throttles back gear not down or flaps incorrectly set.
Take off warning should be an intermittant horn/tone , landing config I think is a continuous horn/tone. Its been a while sorry it is from memory.

Of course you could actually have a real slat problem but suspect you would know about that!:p

The previous poster maybe correct some of the LE devices MEL's do/did require removal of lamps on some 737 series aircraft.Not sure about NG.It has a lot less problems than the 737-300/400 series for LE indication issues.

[BOAC]

Config warning in the air is possible - we discussed it way back and someone posted the failure that is required - not teleflex. A forum search may produce the thread..

[Empty Cruise]

ASFKAP,

LE devices do interface with the SMYDC on the NG's - and it would explain the creeping of the speedtapes as observed.

As for the TO conf warning - well, F30 isn't an approved TO config, so that would trigger that fault as well.

Sounds like the PSEU is well and truly buggered - but that's just an uneducated drivers guess :{

[Telstar]

ASFKAP

Yes that's correct and it has lead to a fatal in the case of Helios and a few very near misses at a host of other airlines.

To quote an earlier post of mine:

The 737 press system has been noted as being deficient in ergonomic terms. It has caught operators out at a few airlines. The accident report into the Helios Crash makes note of this. Here are a selection from 2 operators. The Aer Lingus incident was particularly serious. Please Note that these happened across most variants: -200,-400,-800.

Aer Lingus:

http://www.aaiu.ie/upload/general/3504-0.pdf

FR:

http://www.aaiu.ie/upload/general/3496-0.pdf

http://www.aaiu.ie/upload/general/3893-0.pdf

http://www.aaiu.ie/upload/general/6693-0.pdf

I think there was more, but you get the picture.

What BOAC refers to, I think is this:

http://www.pprune.org/tech-log/352233-737ng-ground-spoiler-system.html

Also another interesting picture!:

Photos: Boeing 737-844 Aircraft Pictures | Airliners.net (http://www.airliners.net/photo/South-African-Airways/Boeing-737-844/1005672/M/)

The former a rare failure mode which despite all the training and contrary to the amended takeoff briefing issued by Boeing as an AD IS actually a config warning once airborne. However the training at the place I work is very clear: Horn when airborne masks on regardless.

[BOAC]

Thanks for digging that up, Telstar. maybe we have a clue here from post#4 of that thread? Config airborne when "Leading edge devices retracted (FSEU function then fed to the PSEU)"

Horn when airborne masks on regardless. - I think on short final I might give that a bye and accept the 'interview'. Just look at me as a rebel with an independent thought process:).

[Telstar]

Just look at me as a rebel with an independent thought process.

Good grief! That's not on. Switch brain off, follow SOPs mindlessly and above all follow the Magenta line..... :}

[Denti]

However the training at the place I work is very clear: Horn when airborne masks on regardless.

Even when the relevant light tells you it is the config warning? Another thing they do in the 737, whenever they feel there is a need to they just add another puzzle piece, warning lights for cabin altitude or config warning, low speed aural warning, the whole aircraft is a jig saw of later added pieces.

[Telstar]

Previous experience has show, and we aren't the only ones if you read the links to the above, that there is more often then not confusion when the horn sounds. Valuable time has been squandered while crews faffed about. The idea is to get the masks on and then problem solve/deliberate.

The message after Helios was horn on the ground is config and airborne was cabin alt. Whilst we have established in the spoiler thread that there is a rare exception to that, there is a chance that it could confuse what should be a simple recognition and so is ignored.

the whole aircraft is a jig saw of later added pieces.

I think it's a very clear admission from Boeing that the pressurization system is a Human factors trap and from a time before ergonomics featured in system design, coupled with a MWS which is a relic and very limited in scope.

[Denti]

737s delivered since shortly after the Helios accident have two additional lights right above the PFD in the pilots primary field of view. One telling you that you have a Config Warning, the other one that you have a Cabin Altitude Warning. I was referring to those lights and the associated distinctly differently boeing advised SOPs than for those planes without those lights. And of course even the boeing advised briefing on the warning (on those old planes without the lights) only talks about masks on above FL100, not on short final.

About it being a somewhat weird combination of pieces, well, that is simply what it is, not a fully integrated system but a puzzle of parts where they add new pieces every couple months.

[BOAC]

And of course even the boeing advised briefing on the warning (on those old planes without the lights) only talks about masks on above FL100, not on short final.- unless it has changed, the QRH still leaves room for the 'non-rebel' pilots in Telstar's club to blindly follow section 2.1 'Cabin Altitude Warning' due to inadequate wording in the 'condition' section. Yes, 15.2 is correctly worded. Hey ho!