737NG's V2 + 20

[QAVION]

During the takeoff roll or initial climb, should a 737NG's command airspeed bug vary from the MCP set speed (V2) in any way. A screenshot from a new 737 desktop flight simulator shows the CAB at V2 + 20 during the takeoff roll. Is this correct? This seems to be quite different from other Boeings where the MCP airspeed window speed always matches the CAB on the PFD ASI.

I understand that the F/D target airspeed will be V2 + 20 after takeoff, but the bug also???

Thanks.
Regards.
Q.

[TR4A]

On the MASI the Airspeed Cursor (magenta) is set with speed selector on the MCP, normally set to V2. There is a white bug that is set to V2+15 it is removed after the first flap retraction.

If using TOGA, after liftoff MCP IAS/Mach display and airspeed cursor change to V2+20 knots.

[QAVION]

Thanks, TR4A.
Had to be sure. Can't say I've seen anything like this before.

To complicate things, our 737-800 Maintenance Manual shows no MCP airspeed change, even at 400' (where the pitch mode changes to MCP SPD). I suspect the MM is wrong... unless I've overlooked something.

Cheers.
Q.

[TR4A]

The info was right out of ours OPS manual for our -700. The 300/500's do the same thing. We have non-EFIS on them.

[QAVION]

"If using TOGA, after liftoff MCP IAS/Mach display and airspeed cursor change to V2+20 knots."

Thanks again, TR4A...
Just to clarify... Would the change to V2+20 be due to an air-ground transition, or is it co-incident with a pitch mode change from "TOGA" to "MCP SPD" (on the ASA) at, say, 400' radio alitude? Our Maintenance Manual shows a diagram of the aircraft at 400' with a different pitch mode (MCP SPD), but no MCP airspeed change, as if it was a critical height.

Would the V2+20 speed be independent of FMC input. i.e. simply MCP speed (pilots' selection of V2) plus a fixed 20kts.

On 767's and 747-400's, TOGA remains until another mode is manually/automatically selected. Until this time, the MCP speed or EADI/PFD speeds don't change. The FD commands the correct V2+xx speed however. xx is variable dependent on aircraft type, lift-off speed, maintained climbout speed and number of engines. Is the speed on the NG always +20kts?

Thanks.
Regards,
Q.

[TR4A]

FD command bars are at 15 degrees nose up after liftoff until a sufficient climb rate is acquired then pitch is commanded to maintain MCP + 20 kts.

If engine fails before reaching V2, bars command V2.
If failure occurs after V2, but less than V2+20k, bars command whatever speed you have. If failure occurs above V2+20k, bars command v2+20.

Is the speed on the NG always +20kts?

Yes