The Impact of Lowering the LDG and Flaps/Slats In Standby???

[AeroTech]

In the drills regarding the LOSS of hydraulic systems (737-300/500) there is two notes.

-Note: When the gear has been lowered manually, it cannot be retracted. The drag penalty with gear extended may make it impossible to reach an alternate field.(This note is related to the loss of system A)

-Note: The drag penalty with leading edge devices extended may make it impossible to reach an alternate field. (This note is related to the loss of system B and the flaps/slats are extended by standby pressure)

How serious the fact that extending the gears and the leading edges devices will affect the fuel reserve?

Did this problem (fuel depletion) happen before?

Does it mean, it is preferable (may be recommended?) to delay the extention of the gears (manually) and the flaps/slats (standby mode)? How pilots overcome this problem?

Can other aircraft (Boeing & Airbus) encounter this problem?

Thank you. Feedback appreciated
Best regards

[Maverick343]

When you are considering an alernate airfield may be 45min. to an hour away, flying with flaps/slats and gear down is going to have an adverse effect on the fuel consumption.

I am not sure if this has happened before but I would say it is advisable not to lower the gear/flaps until you are sure your landing (if that is possible). This obviously is a judgement call, but with a long runway I wouldnt be as concerned about getting my flaps out, especially if i may end up having to go to my alernate, because than I could be flying for a prolonged time with flaps/gear down.

[Old Smokey]

It's a common problem on most aircraft. In almost all circumstances, the penalty of dragging the gear and Flap to your alternate would be intolerable.

May I suggest the following 2 points to add to your decision making process -

(1) Ensure that the arrival weather is comfortably above minimums, and unlikely to change, before irreversibly lowering your gear and flaps, AND

(2) Ensure that ATC have given you Number 1 priority for landing before irreversibly lowering your gear and flaps.

If BOTH of these criteria cannot be met, divert to your alternate whilst still in the clean configuration.

Regards,

Old Smokey

[Empty Cruise]

I think there was a HL A310 some years ago - the crew demonstrated that not only can flying with the gear down make it impossible to reach an alternate - it can even make it impossible to reach the destination - despite the FMC predictions :rolleyes:

So before you drop the gear - check what your revised Alternate & Final Reserve Fuel is gonna be - this info can be found in the QRP. The same goes for operation of the SBY flaps - make a calculated "guesstimate" of your fuel required before touching those switches.

That being said - depending on when you discover the failure & the amount of fuel you have chose to carry, you might find yourself way below those figures when you finally realise you have a problem. E.g.: 1 main gear will not extend when you call for gear down. Will you retract the gear on the go-around? If you do - that might compound the problem. If not - you might not have fuel to go anywhere else. Do you take that into consideration before you "go & have a look" at an approach that you are not totally convinced will lead to a landing?

As OS pointed out - when you know the problem in advance, you have options, and need to exercise them. The problem occurs when the problem is sprung on you - so you even need to take these considerations into account during normal ops. Trying an ILS cat I with RVR0600 BKN001 - while legal - suddenly becomes less appealing if you are close to your minimum fuel for diversion already, and you think about suddenly getting a flap skew around F25 :{

Empty :cool: