Flap Retraction and Zero Flap Speed

[nealfix]

Hi,

On approach how is zero flap speed derived? I am looking for the regulation and the aerodynamic theory please.
On departure how is the flap retraction speed derived? Again I am looking for the regulation and the aerodynamic theory please.
I do not care about noise abatement.
I have seen V2 plus a value (10, 15 and 20 knots)for flap retraction speed and V2 plus a percentage that varies with aircraft weight or does not vary with anything.
On departure how is zero flap speed derived?
If someone can point me to a manual that gives answers that would be great.
FAR 25.143 is free of stall at 40 degrees of bank and may enter into some of the calculations. The airplane is a four engine airplane so the 1.7% of FAR 25.121 would have to be respected.
Are there actual graphs and/or tables in other four engine airplanes?
I fly an older airplane. A Lockheed Electra and there are no performance data for any of this in limitations or the performance sections. Is flap retraction minimum 1.25 of the stall speed?
Thank-you for any help with these questions.

[Zaphod Beblebrox]

I am straining my limited brain power to answer this question but I think the question revolves around a possible difference between a min flap retraction speed and a minimum maneuvering speed.

A poster speaking on the A320 is correct in that the min maneuver and min retraction speed on the bus are the same. Green dot is that speed. However, on the B737 for single a engine go-around there is a lower speed for flap retraction and acceleration that is maneuver limited. You are limited to 15 degrees of bank.

So my answer is on departures and especially on single engine go around there may be a lower speed to select flaps up but that condition is maneuver limited until you have reached the min maneuver flaps up speed. I think this is to improve single engine governing weight limits etc.
I don't know the technical definitions however.

[Gysbreght]

If someone can point me to a manual that gives answers that would be great.
FAR 25.143 is free of stall at 40 degrees of bank and may enter into some of the calculations. The airplane is a four engine airplane so the 1.7% of FAR 25.121 would have to be respected.The 'aerodynamic theory' is that an adequate margin to the stall speed and stall warning speed must be maintained during flap retraction. To my knowledge it is not written in any regulation or associated guidance material, with one exception: to allow flap retraction in a go-around at VREF, the stall speed in the approach climb configuration of FAR 25.121(d) may not exceed 110% of the stall speed in the related landing configuration.

FAR 25.143 requires freedom of stall warning at 40 degrees of bank at VREF in the landing configuration. It is not relevant for flap retraction.

FAR 25.121(c) requires a gradient of 1.7% for 4-engine airplanes in the clean configuration. It does not define the flap retraction speed.

Boeing's Jet Transport Performance Methods, Chapter 17 Speeds, sections "Maneuvering Speeds" and "Flap Retraction/Extension Speed Schedules" has the following description of Boeing's methodology:

Flap Retraction/Extension Speed Schedules

Following the takeoff, the airplane must accelerate from its initial climb speed and, during that
acceleration, retract the flaps to their faired (fully retracted) position. Bear in mind that flap extension
greatly increases an airplane’s drag and reduces its climb performance, so it’s desirable to
retract the flaps as soon as it’s safely possible.
During flap retraction after takeoff, the wing’s lift coefficient is decreasing and the stall speed is
increasing. Also, takeoff departure paths frequently require turns at low speed and altitude, and
those turns will increase the stall speed at any given flap setting. (...)

During the approach for landing, the airplane must gradually decelerate toward its landing reference
speed and extend its flaps in order to cross the landing threshold at the proper speed to
ensure the correct landing distance capability. (...) Once again, he is following the rule of selecting
the next flap setting when decelerating through the maneuvering speed for his present flap setting.

Maneuvering Speeds

Maneuvering speeds are those minimum speeds recommended for maneuvering the airplane after
takeoff and before landing. The intent of the maneuvering speeds is to ensure adequate margin
from stick shaker or initial buffet.
“Adequate” margin in this context is considered to be a speed that will allow maneuvering at bank
angle up to 25 degrees plus an unintentional overshoot of 15 degrees, for a total bank angle of 40
degrees. You’ll recall that the load factor is given by 1/cos(bank angle) which, for a 40 degree
bank, would correspond to a load factor of 1.305 gees.

Maneuver speeds are chosen to meet a number of criteria:
• simplicity of use (round easy-to-remember numbers);
• commonality with other models;
• maneuver margin to stick shaker equal to or greater than 1.3 gees;
• provide climb capability or acceleration that is close to optimum for that flap setting;
• never greater than the flap placard speeds;
• never less than the reference speed VREF for the given flap setting;
• compatible with actual times required for flap retraction or extension;
• provide relatively constant pitch attitudes in level flight with minimal thrust changes required at the different flap settings.