737NG TE Asymmetric Flap QRH Question

[Stan Woolley]

Trailing Edge Flap Asymmetry

In the above QRH checklist where it says..........
' Move flap lever to the detent nearest the smallest indicated flap position.'

If you had the guage slightly(but clearly)split with one indicator (say L)exactly at F1 position and the other (R)between F1 and UP but close to the
F1 position,where do you put the Flap lever?

Up or F1?

[Becker Junior]

I would bet to leave it at F1 position.

[gonso]

Stan, for my money, this is the only tricky flap/slat scenario. When I say tricky, I mean how you interpret the QRH.

Following the QRH exactly, you should put the lever to 1.
BUT if you read futher down, the QRH requires an answer on the following question: How much flaps do you have?
The options are three.

If flaps are 15 or more

If flaps are 1 or greater and less than 15

If flaps are less than 1

By placing the flap lever to 1 (as QRH dictates), you are prone to decide you are in the "flaps1 or grater and less than 15" category.
WRONG. You do not have flaps 1. Your lever is at 1. Not your flaps.

If wrongly you decide to follow the "flaps1 or grater and less than 15" "thread", you will end up landing with no LE devices at all, although there is nothing wrong with them.

If you follow the "If flaps are less than 1" thread, it will lead you to the TRAILING EDGE FLAPS UP LANDING checklist, which will guide you on extending LE devices.

Very badly written, but it is the only confusing one you are gonna have to remember.
I hope it makes sense:)

[Nightrider]

If there is only a little roll moment, like it will be in this situation you mention here, it would be the best judgement to not touch the flaps anymore and to proceed further down on the very same QRH page with the speed selction and follow the details explained there.
If there is a serious roll moment, then move the flap lever to the smallest indicated flap position.

[Ashling]

Up is a Flap position is it not ?

If the indications are as described in the original post put the lever to the smallest indicated flap position.

That would be Up then.

[xetroV]

No, I don't think so. In this particular example, the smallest indicated flap position is "between F1 and UP but closer to the F1 position", so the detent nearest this smallest indicated flap position is F1.

Note 1: I added the "r" in "closer", because I think that's what Stan implied (if not, then it's not just the QRH that needs clarification ;)).

Note 2: I can easily imagine crews (especially non-native English speakers) getting confused by this instruction, perhaps interpreting it as e.g. "move flap lever to the smallest detent near the indicated flap position". It doesn't help that the actual checklist item is FLAPS ... SET, where in my opinion it should have said FLAP LEVER ... SET: the flaps most likely won't move anyway, since hydraulic power should have been removed by the flap asymmetry protection.

[Stan Woolley]

Thank you very much for the replies.

There is a tendency to compare the (split)flap position indicators and take the smallest detent that the lower of the two is closest to.

The QRH actually implies that you should be looking at the 'smallest indicated flap position' in isolation.

I'm an experienced (english speaking)737 pilot and instructor and I've been getting this wrong and putting the flap lever up. As gonso said this actually leads to the correct response later in the checklist(ie. 'If flaps are less than 1')and is a conservative approach I suppose, but I am a bit embarrassed.

Any more input welcome.

[stijn01]

just a thought but not sure. Isn't in an NG the flap indicator driven by the flap and slat computer so the computer will give you the indication so I don't think you will get an indication like you mentionned. I think it will be in the middle of up and Flap one so maybe flap up after all????????? If the computer senses a split it will indicate an exact split via the flap indicator or do I have it completely wrong?

Just a thought I'm not sure

Greetzz