I'm reading the FCTM and it says when taking off, begin flap retraction at V2 + 15 kts. For my TO weight, my V2 is 144 kts...so V2 + 15 is 159 kts. So I can *begin* flap retraction at 159 kts going to flaps 1.

 

Or maybe not:

I'm taking off at flaps 5. My flaps 40 vref speed is 136 kts. So, the flaps 1 min maneuvering speed calculates to 186 kts (Vref flaps 40 + 50).

 

According to the FCTM, I can begin to retract to flaps 1 at 159 kts yet the flaps 1 min man speed is 186 kts. A 25 kt spread.

 

So, in this case, with my weight numbers provided, I would have no choice but to wait until 186 kts to start flap retraction...right?

 

Normal flap retraction schedule is a function of speed and altitude.  For a non-noise abatement takeoff, above 800ft AFE you may retract flaps at V2+15kts, except for flaps 1 takeoff.  For flaps 1 TO, begin flap retraction reaching the flaps 1 maneuver speed.

 

During flap retraction, selection of the next flap position is initiated when reaching the maneuver speed for the existing flap position.  Therefore, when the new flap position is selected, the airspeed is below the maneuver speed for that flap position.  For this reason, the airspeed should be increasing when selecting the next flap position.  During flap retraction, at least adequate maneuver capability or 30 degree bank (15 degree bank + 15 degree overshoot) to stick shaker speed is provided at the flap retraction speed. Full maneuver capability or at least 40 degrees of bank is provided when the aircraft has accelerated to the recommended maneuver speed for the selected flap position.

 

Note at TO flap setting bank angle must be limited to 15degree's until reaching V2+15.

 

A typical F5 takeoff - select F1 at 800ft and V2+15.  Select F0 at F1 maneuver speed(VM1).  F15 takeoff - F5@V2+15 F1 at VM5, F0 at VM1.

 

VM0=Vref40+70 PFD Bug 0

VM1=Vref40+50 PFD Bug 1

VM5=Vref40+30 PFD Bug 5

VM10 =+30/10

VM15=+20/15

 

Source is company flight manual 25 Oct 14.

Thanks for that info.

 

Now I have to think about my take off sequence of events and blend that into the flap retraction sequence.

 

For example, while I can start flap retraction from 5 to 1 at V2+15 and 800 feet, I can't do flaps 1 to Up until I reach 1500 feet acceleration height which is where I increase my ATS speed from the pre-flight setting of V2 to flaps up maneuvering speed...and *then* accelerate to that speed so I can retract flaps up.

A technique I have grown found of is to use VNAV - it will automate much of the accelerate/cleanup and you don't have to keep messing with the bug speeds. It will command FD pitch for the next flap maneuver speed as you retract on schedule.

 

Select VNAV on ground before selcting TOGA, and it will be in the FMA as a white - standby pitch mode.  It becomes active mode at 400ft.

 

For smoother VNAV speed transitions, I like to set my VM0 (vref 40+70)in line L2 on the VNAV climb page - TGT Speed. 

 

Then, when you are ready to accelerate above this speed - just hit ECON and the normal climb speed profile resumes.

Thank you...I'll take note of that when I start to use VNAV.

 

My current route I am learning to fly is KLAX to KLAS (Los Angeles to Las Vegas) and I depart west bound on radar vectors. I am flying LNAV and VNAV but the FMC route doesn't start until I fly outbound for 15 miles on the Loop6/7 SID and then make a left turn back to the LAX VOR at 10,000 feet...as I approach the VOR I engage LNAV and then VNAV and they engage and take over from there, but obviously, that's well after take off.

 

Sooooo...this means I have to take off without LNAV/VNAV and just fly the MCP alone for a while at least. So, I'm currently trying to learn how to fly the take off with just using the MCP and auto pilot. I turn on the auto pilot at 400' agl and am trying to wrap my head around the flap retract schedule from that point on.

Not sure if you are familiar with Boeings FCTMs - they are included with the product and should include the info you look for.

Yes I am and that's the problem I was posting about: the FCTM says to start flap retraction at speed tape display 5 to 1 and 1 to UP. But my speed setting for TO is V2 so I was wondering about the steps (which is not covered in the FCTM) to accomplish this. I can't get to flaps up with my speed window set to V2. So I assume I have to wait until my CDU set acceleration height (1500 feet) and dial in the speed window the flaps up speed before the plane will start accelerating to that target speed and then I can finish flap retraction.

Yes I am and that's the problem I was posting about: the FCTM says to start flap retraction at speed tape display 5 to 1 and 1 to UP. But my speed setting for TO is V2 so I was wondering about the steps (which is not covered in the FCTM) to accomplish this. I can't get to flaps up with my speed window set to V2. So I assume I have to wait until my CDU set acceleration height (1500 feet) and dial in the speed window the flaps up speed before the plane will start accelerating to that target speed and then I can finish flap retraction.

 

 

You might refer to the NADP 1 and 2 PDF that I posted in your other thread.  I think it goes into more detail as to the process from V2 (+ 10) and into the retraction schedule.

Curious what few months off type does to a person.

 

I had to go take a look at the books.

 

What I found:

 

-Setting your SPD command window will make the pitch bar command for V2+20 climb (normal ops).

-You should keep V2+20(+-5) and TO flaps until acceleration, pitch down slightly at reduction (you should see a pitch down tendency due to both inherent speed stability and whatever-is-that-effect-called-when-airplanes-with-underwing-engines-pitch-in-reponse-to-thrust-changes)

-at acceleration, select LVL CHG, dial in flaps up speed, accelerate and retract flaps.

 

You can begin retraction at V2+15, but that does not mean you start retraction before acceleration.

The event sequence as described by both FCOM and FCTM will have you keep TO flaps until acceleration altitude is achieved, then retract according to schedule. Your flying at V2+20 will allow you to retract one step immediately (except on Flaps 1 takeoff)

Wow -- very clear explanation Fabo (especially your last paragraph)...now I feel like I understand what's going on with this topic...and you were able to explain it much better than what is in the FCTM or FCOM...thank you so much....!!!

Clarification please:

 

My CDU acceleration altitude is the standard 1500 feet. Should my MCP altitude initially also be 1500 feet to force the level off? Currently I'm setting the MCP altitude to 3000 feet and I notice there isn't really a level off happening at 1500 feet. The only thing that is happening at 1500 feet is that CLB power is kicking in.

 

So, should the CDU acceleration altitude match the MCP initial altitude?

 

Thanks...

No, you dial in first cleared altitude (explicit by ATC clearance or implicit by publications. Often 5K feet in Europe. No idea about US, no experience flying there).

 

There is not supposed to be a level off at reduction altitude, just a slight pitchdown to keep the speed.

Same with acceleration altitude, no implicit level off, just a further pitch down to get to speed.

 

 

No idea about US, no experience flying there

 

All based on airport SOP.

 

IAD is 3, DCA is 5 and BWI is 4 be default.  It's all based on local traffic flows.

 

 

 

So, should the CDU acceleration altitude match the MCP initial altitude?

 

For name dropping so many aircraft on which you have experience, shouldn't you know most of these things already?