737NG - gear lever will not move up after takeoff

[vopz]

condition: the landing gear lever cannot be placed to the up position in the normal manner due to one or more of the following:

• failure of the landing gear lever lock solenoid

• failure of the air/ground system

• failure of the ground spoiler bypass valve to close

the first and second items are obvious but the third one is not.
the question is why the ground spoiler bypass valve restrict the landing lever to move up after takeoff if it fails to close.

[Lufthansa_NFF]

sounds like B737

[Rainboe]

Interesting question. I assume it is B737. FCOM 9.20.15 says the right main gear compression causes a mechanical linkage to open the ground spoiler bypass valve to allow spoilers to deploy. If it is a mechanical linkage, therefore if the ground spoiler bypass valve does not close after take-off, the air ground sensing is faulty and the aeroplane still thinks it is on the ground, therefore will not let you retract gear (I think!).

[vopz]

sorry i am talking about a B 737 NG

[vopz]

it sounds wrong,why?
if after takeoff i have a probleme with a ground spoiler bypass valve that prevent the ground spoiler to be in the down position,it add another probleme wich is i cannot raise the landing gear in the most critical phase of flight.

second point is :the takeoff is always made with the spoiler in the down position.in addition even if the ground bypass valve fails to close, the ground spoiler don't raise without actionning the speed brake lever and the airplane must be on ground.

[Rainboe]

Yet if you have a problem with air-ground sensing, you are also unlikely to be able to pressurise. There are very many other problems associated with this air-ground sensing. I think they intend that you cannot complete your flight and should land back anyway as loss of adequate air-ground sensing is so serious. The danger also is that full ground spoilers would be available in the air, so leave the gear down and do not complete the flight and land back.

[Conan The Barber]

Is the air/ground sensing on a 737 a single or dual system?

If the ground spoiler bypass valve is mechanically operated, I assume it is done so by the oleo extending. Should the oleo remain compressed will the gear fit into the gear bay?

[vopz]

i would like to be more clear.
i do not have a probleme with air-ground sensing.
i agree with you when you rainboe when you say if the problem concern the air-ground sensing,it 's ovious that all pilot will land back.besides the check list is very clear :

" if the intermittent cabin altitude/configuration warning horn sounds and the TAKEOFF CONFIG (if installed and operative)iiluminate when the flaps are fully retracted:

note: this condition indicates a failure of either the air/ground system or
failure of the ground spoiler bypass to close.

so the note is very clear,that are two distinct failure:

-1- failure of air/ground system.

-2- failure of the ground spoiler bypass to close.

my question is about the second failure,wich is different from the first one.
boeing says the air/ground system or failure of the ground spoiler bypass to close
there is an or between the two sentences,it means the failures are diffrent.
dealing with the two failure are the same ,in the two cases we have to land back i agree but why this bypass valve restrict to continu the flight.

[Rainboe]

There is more than one air-ground sensing system. In this case, compression of the right main gear opens the spoiler bypass valve, and blocks gear retraction. It is 2 outcomes of one failure event. You still have available the Override trigger which will bypass the lever lock and allow the gear to be raised, but it is essential to follow the QRH.

Perhaps more useful than the FCOM here is Bill Bulfer's excellent 'Cockpit Companion' book.

[vopz]

i prefer to say:two failures event for one outcome

[Rainboe]

The only failure event from your original question we are examining here is in particular the lack of closure of the Ground Spoiler Bypass Valve on lift-off. The two implications are:
*availability of full ground spoiler operation in the air
*inability to raise gear without using override trigger

[Conan The Barber]

For the gear retraction interlock, which gear's air/ground sensing is used?

[Rainboe]

See post 4

[HAWK21M]

The MLG Teleflex cable sensing Air-Grd is also linked to the ground spoiler Bypass valve so that the Ground spoilers only deploy on Ground.
regds
MEL

[Terraplaneblues]

• failure of the landing gear lever lock solenoid = open circuit

• failure of the air/ground system = air/gnd system 1 not in air OR air/ground system 1 is overidden to air - from sensors on the gears/PSEU box logic

• failure of the ground spoiler bypass valve to close = mechanical teleflex on RH MLG that operates on gear extension - may have failed allowing full extension of flight spoilers & ground spoilers in air

Or on a bad day all three faults.......

[Terraplaneblues]

Ref Conan Question

For the gear retraction interlock, which gear's air/ground sensing is used?

Any 2 of the 3 gear system 1 inputs = in the air AND system 1 not overridden to air AND ground spoiler interlock valve closed