B737 QRH LANDING GEAR

[Raptor71]

Hello guys,

Small question about the Check list ( LANDING GEAR WILL NOT MOVE UP after take off)

We are instructed to use the override trigger if the horn stays silent ( failure in the landing gear lever assembly)
However, we are told to keep the gear down otherwise because it would mean a failure in the ground spoiler valve or in the air/ground systems.
However, I do not understand the consequences of retracting the gear with such failures... what would be the risk? not being able to extend the gear afterwards?

Thanks

[FlyingStone]

If the warning horn stops after you retract the flaps, the problem is only in the landing gear lever mechanism, as you point out. In this case, all other procedures (after the NNC) stay the same as all of the systems work normally.

If the warning doesn't stop, you have a serious problem, that has effect on multiple systems, especially on speedbrakes, where the ground spoilers will deploy in-flight if speedbrake is used. So in that case, you can't continue normal flight (imagine that you have a rapid decompression at FL410 and you pull the speedbrake and you get ground spoilers out :eek: ), so the safest way is just to leave the gear down and configure for a landing at a nearby airport.

On a side note, I'd consider raising the gear in the latter scenario only with an unsatisfactory aircraft performance with gear down (engine failure). But then it would have to be a really bad day for that to happen...

[Raptor71]

Ok so the only reason to keep the gear down, is because the best course of action in to turn back to land.
However, retracting it will not cause any extra problem.

[wiedehopf]

this thread seems to offer some background
737NG Ground spoiler system [Archive] - PPRuNe Forums (http://www.pprune.org/archive/index.php/t-352233.html)

if for some reason the ground spoiler valve fails retracting the gear could maybe "reverse" the failure meaning loss of ground spoilers? just a guess though
(cable connecting the valve to the ldg gear being stuck or high friction)

[Raptor71]

That was the meaning of my question.
What are the risks if we retract the gear?
there is a risk of ground spoilers actuating but only if we use the speed brake lever and it does not matter if the gear is up or down in that case....so this is definitely not the answer.

My guess would be , it is not possible to extend the gear afterwards since the airplane is in ground mode.....

[RAT 5]

My guess would be , it is not possible to extend the gear afterwards since the airplane is in ground mode.....
Are you suggesting the manual extension systems will not work? Isn't that just mechanics, gravity & aerodynamics?

[4Screwaircrew]

If you just pull the trigger and raise the gear you now don't know which failure you have, keep it down and follow the QRH and you will find the diagnosis much easier make.

[FlyingStone]

What are the risks if we retract the gear?

The question should be: what are the benefits of raising the landing gear in that situation?

The NNC clearly states to land at the nearest suitable airport. Since this happens on takeoff, performance/fuel to reach a suitable airport shouldn't be an issue (assuming two engines obviously).