Flaps maneuver speed

[S7EVIN]

Hello all,

FLAPS MANEUVER SPEED are recommended operating speeds during takeoff and landing and guarantee full maneuver capability.

FLAPS MINIMUM MANEUVER SPEED is the minimum speed that provides full maneuver capability.

They provide the same thing except that the first is calculated according to aircraft weight and the second according to AoA and airspeed.

Other than that what is the difference? What makes the FLAPS MANEUVER SPEED recommended over the FLAPS MINIMUM MANEUVER SPEED?

Thanks

[RAT 5]

If you mean by 'Min Man Spd' that which is displayed by the amber band on the speed tape (B737NG) then that is 1.3-1.4g. Pull that g at that speed and you will be at Stick Shaker, independent of configuration. The green F number is the normal manoeuvre speed for the configuration. It guarantees upto 40 degrees of bank. (1.4g) It also includes a 20kt buffer to the amber band. This is to protect against those not monitoring the flap gauge and slowing to a lower F number without the flaps having moved; thus being 20kts below the F number. Hopefully that mistake is not repeated but noticed and corrected.
All the above is my understanding, but I might need to 'ask a friend' if the answer is critical.

[S7EVIN]

Thanks RAT5.

1.3g can be pulled in level flight and that corresponds to a bank angle of 40° so this conferms that they provide exactly the same thing except for the higher speed in the case of the green F speed.

So is it only a safety margin? :suspect:

[S7EVIN]

Here a similar doubt.

"For altitudes up to approximately 10,000 feet, the flaps-up amber band functions just like the flaps-down amber band described above, with the top of the amber band representing full maneuver capability. [...] Above approximately 20,000 feet, the top of the amber band shows the speed that provides 1.3g maneuver capability to low speed buffet (or an alternative approved maneuver capability as preset by maintenance)."

What does it mean with "full maneuver capability"? How is it different from the 1.3g maneuver capability at the top of the amber band at 20.000ft?

[RAT 5]

To my understanding Boeing's 'full manoeuvrability' means 25 degrees bank angle with 15 degrees upset overshoot to 40 degrees. Limited MAN = 15 degrees with 15 degrees overshoot. You'll note that 40 degrees in level flight is 1.3-1.4g. This is at all levels.

[Avenger]

You will not extend the flaps above FL200, ( you can fly with flap already extended) if situation requires. Therefore clean, above FL200 the amber band is a reflection of buffet and is limited by thrust, OAT and Weight. In LNAV real time bank angle protection will limit the roll, if you use HDG select you may over bank. In short, 1.3 G is not guaranteed and ref to this is found in the LRC MAX operating altitude tables.

[john_tullamarine]

you can fly with flap already extended

Can you provide some justification for this statement ? .. excluding some unlikely emergency scenario.

[RAT 5]

In LNAV real time bank angle protection will limit the roll, if you use HDG select you may over bank.

With the information fed to me this is not correct. HDG SEL will depend on the BA selector setting; i.e. you can over bank and thrust will not maintain speed. LNAV will allow up to 30 degrees as necessary, at all altitudes. Again, this may cause speed decay if trust is not sufficient.

[S7EVIN]

"For LNAV operation, the FMC provides a real-time bank angle limiting function. This function protects the commanded bank angle from exceeding the current available thrust limit. This bank angle limiting protection is only available when in LNAV."

Avenger what do you mean by "1.3g is not guaranteed"? When it is not? On the top of the amber band?

[172_driver]

It guarantees upto 40 degrees of bank. (1.4g) It also includes a 20kt buffer to the amber band. This is to protect against those not monitoring the flap gauge and slowing to a lower F number without the flaps having moved; thus being 20kts below the F number.

RAT5, my assertion is same as yours except I have never heard about the 20 kts buffer?

Flying min maneuvering speed during moderate turbulence, in a turn, combined with inattentive pilots, could take you uncomfortably close to stick shaker and most likely induce some hair rising AIRSPEED LOW alerts.

As we are on the topic of maneuver limits. Look in the FCTM and check the maneuver margin as you raise Flaps 1 to Flaps Up. The LE devices are retracting. If it wasn't for the requirement to have positive acceleration towards Up-speed, and the slow retraction of the LE slats, it would actually take you into the amber band. As this often coincides with a turn as part of the SID, the Pitch Limit Indicators are not that far away!!

[Qwerti]

Amber bands / manoeuvre margins are affected from Altitude, CoG and weight.

LNAV protection, thats the computers calculating excess thrust and giving the authority for LNAV to bank more.
HDG select, doesn't do that for you which means that with a higher AoB selected and a not enough thrust you can decelerate in the amber band (where indeed, your manoeuvre margins will be more limited). Which confirms that even if you fly outside of the amber band does NOT mean that you have the required thrust to complete the manoeuvre.

I remember an article from Boeing explaining how at low speeds (ie 10,000) the amber/red bands are based on AoA & at higher altitudes/Mach numbers, the FMC bases the margins to either the stickshaker or initial buffet whichever is higher.
1.3g maneuver capability to low speed buffet (or an alternative approved maneuver capability as preset by maintenance)

So my wild guess is that maybe they use full manoeuvre capability for reference to stickshaker and manoeuvre capability for initial buffet? :confused:

I stand to be corrected :ok: