No CLB thrust after T/O

[United744]

As the subject.

Situation: aircraft lined up ready for takeoff. Thrust rating TO with CLB armed. INIT REF page shows CLB thrust at FLAP 5.

* Commence takeoff
* Clean up
* At flap 5, NO thrust reduction to CLB thrust
* Clean aircraft passing 10000 ft - still TO thrust.

NO use of TOGA or FD for takeoff (just in case it is pilot error).

10.0.3-beta 12.

[John H Watson]

NO use of TOGA or FD for takeoff (just in case it is pilot error).

Does it work with TOGA and FD?

Is VNAV arm or engage required for the aircraft to switch into CLB thrust mode at Flaps 5?

[Hardy Heinlin]

I think, if you fly manually without VNAV, you need to push the THR button to get CLB.

If somebody can confirm that VNAV engagement is not needed for the autochange from TO to CLB, then I'll be happy to remove this condition. After all, the other thrust mode autochanges don't require VNAV either.

[Stephane LI]

Hi,

Here below an extract from the FCTM. I don't think that thrust mode automatically switch to CLB if you take off without VNAV armed. You need to push FLCH or THR to engage CLB mode.

VNA V is normally armed for takeoff and engages at 400 feet AGL. The use of VNA V for takeoff, flap retraction and climb out is the preferred method of managing the AFDS for takeoff. This provides the VNAV profile and acceleration schedule compatible with the planned departure.

VNA V, armed on the ground with the appropriate acceleration altitude entered, is the recommended pitch mode for takeoff. When armed for takeoff, VNAV engages at 400 feet AGL and provides AFDS management for acceleration, flap retraction and climb out. The VNAV profile and acceleration schedule is compatible with most planned departures.

Note: Climb thrust is normally selected automatically by programming the FMC so that VNA V commands climb thrust after flaps retract to 5.

With VNA V engaged, acceleration is automatically commanded. Retract flaps on schedule. Check that the thrust reference changes from TO to CLB on the EICAS at the point selected on the takeoff reference page. If the thrust reference does not change automatically, manually select climb thrust.

If VNAV is not used, at acceleration height select FLCH and set the command speed to flaps up maneuver speed + 20 knots. Climb thrust is normally set after flaps retract to 5 using the THR switch on the MCP. Check that the thrust reference changes from TO to CLB on the EICAS.

With all engines operating, climb thrust is normally set after flaps retract to flaps 5. To achieve optimum climb performance during flap retraction, accelerate while climbing so thrust can be reduced to the climb limit within 5 minutes (or other required time limit).

Stephane

[United744]

Thanks Stephane!

Is VNAV arm or engage required for the aircraft to switch into CLB thrust mode at Flaps 5?

I thought it was supposed to switch based upon selection of Flaps 5, which is why I was getting confused when it remained in TO.  :oops:

[Stephane LI]

Even if VNAV is armed, CLB thrust may not switch automatically. Then you have to manually do it.

[United744]

Even if VNAV is armed, CLB thrust may not switch automatically. Then you have to manually do it.

Do you know under which conditions it wouldn't switch? I'm guessing not selecting Flap 5 would be one, and where VNAV doesn't capture would be two...