737 Flap Extension Schedule

[Sourn Rose]

Iunderstand that there are probably no set altitudes and speeds for flaps extensions, but can someone with insight provide a general guide for speeds, altitude and flaps for an ILS approach in good weather for a Boeing 777-300ER with a landing of Flaps 25 and $V_ref$ of 147 knots.

Subsequent flap settings are also combined with selecting a lower speed as shown above. The speed tape makes it easy. Flaps 5 should be down by the final intercept path to the localizer or before turning base. Flaps 20 when established on the localizer. Then comes gear down and flaps 30 before the glide-slope is captured.

On most Boeing twinjets (don't know about 747), the flap manoeuvre speeds can be derived or at least estimated with reasonably good precision by adding increments of 20 knots to VREF for the highest landing flap, e.g. to VREF30 for the 777. Minimum clean speed on these aircraft is typically around VREF30+80. The approach speed schedule recommends to extend each flap as you decelerate through manoeuvre speed (up to typically plus 20 knots). This means e.g. on a 777:

Thanks for the detailed explanation! I assumed something like this but wasn't sure whether this is actually the case, since I couldn't find anything about it and it is different in other planes (e.g., the 727).

Just had a read of the FCTM and during acceleration the flap retraction schedule gives 15 degrees bank + 15 degrees overshoot buffet protection (ie up to 30 degrees of bank) which is deemed adequate, at the manoeuvre speed with the appropriate flap setting full manoeuvre margin is available as per my previous post.

This makes perfectly sense. I'm not very familiar with the 747, 777, or 787. But I just checked the FCOM of the 737-800, which I fly from time to time. It uses the shifted flap schedules as well: You retract or extend the flaps to the next flap position at the maneuvering speed of the current flap position. I.e., you go to from 5 to 1 at the flaps 5 maneuvering speed, while you go from 1 to 5 at the flaps 1 maneuvering speed exactly as in the 757 and 767.

Just a question as to technique, but are you guys relying on the F flag on the PFD or doing the math on the fly? I've been relying on the PFD information for extension and retraction schedule and it seems to work out just fine. I'm asking to ensure that the information presented on the PFD is consistent with what I should be doing.

I just tried to find this out, but I was not successful. The FCOM and QRH only refer to the maneuvering speeds indicated on the speed tape, and surprisingly, they do not say anything on how they are computer (or at least I wasn't able to find it). I just know that in the case of the 727, the speeds are indeed calculated depending on the GW and not depending on VREF.

I'm was used to fly the plane without speed tape. As @AileronsNeutral stated already, there is not much math to do because +80 and +40 are indicated by speed bugs and the other speeds you need are in the middle between both and 20kt below the +40 bug. V1/Vr and VREF, respectively, are indicated as well.

Thanks for the validation gentlemen. I just wanted to make sure I was doing it "right". I occasionally get the F flag jumping around but I'm positive that is just due to noisy pots on the Saitek throttle, so good to know the alternative method using the bugs.

There is a bug in the latest update where the plane does not decelerate when deploying flaps in VNAV. In previous versions when you started deploying flaps the AutoThrust would decelerate for the next schedule.

However, when using these values I continue to get overspeed warnings. I understand that these speeds are dependent on a number of factors but are there a hard wired set of speeds built into this aircraft?

Retracting the flaps: As you accelerate retract the flaps as the same in reverse. Asssuming Flap 5 departure maintain V2+15-25 until your acceleration altitude and then accelerate towards Vref+40 retracting the Flap to 1 as you approach it, continue to accelerate and select flaps up as you approach Vref+60. Your minimum speed is now Vref+80. If you want to fly part of the departure with a lower speed (ie close in turns at high gross weights) then accelerate to the appropriate manoeuvre speed and hold it until ready to continue accelerating.

The fundamental flaw in the model is not a bug but how the Overspeed warning is set. In a Boeing aircraft (except 777X), will never have an Overspeed warning if Flaps placard speed is exceeded. All indications on the speed tape (Red barber pole) will show (this is accurate in the model.

Everything you asked about is on page 3-1-57 in Volume 3 of the included manuals. BTW, that's the tutorial, and if you haven't flown it, you really should. That and view all of The Dude's videos at this link.

I noticed that the take-off flap schedule given in Vol. 3 differs from the one given in Vol. 1 on page 1-1-38. The former is basically the reversed version of the approach flap schedule (set 8 at 180kt, set 0 at 200kt). The latter rather corresponds to what you do in Boeing planes, where you retract the flaps at the speed corresponding to the current flaps setting (set 1 at 160kt, set 0 at 180kt). Does someone know which one is correct? Or are there situations, where one would use the one or the other?

Good catch. I've long gravitated to visual depictions for profiles as I used to write them for general aviation air taxi training manuals. So I usually pay close attention to the profiles, but find it easier to use what I'll call the Boeing method since I use several aircraft depending on what kind of flying I want to do in a given session. As a long time user of the PMDG 737s, picking up the flaps as you accelerate through the green flap setting numbers is just so simple.

Yes indeed It's the same for Airbus btw. However, I'm coming from XP11 and spent a lot of hours on the 757/767. If you select the early configuration without speed tape, you need to have the schedule in mind. So I usually add the flap schedules to my own check-lists. But in contrast to the CRJ, you have at least those white markers at the analog ASI in the 757/767. For the MD80, which I've flown a lot in XP11 as well, I was using speed cards. Here you also retract the flaps at the speed corresponding to the current flap setting (given that the plane is accelerating).

I just noticed that the speed cards in Vol. 2 of the manual (Quick Reference Guide) on pages 2-1-38ff actually contain the flap retraction schedule. Those numbers correspond exactly to those of @KuntaKinte.

The installer usually adds links to each volume in your Start Menu. So, I suggest you go through every folder there and look for them. If you have it installed through Aerosoft One, look in the Library as shown here:

In any event, you should be able to find them in the Documentation folder inside the Data folder inside your CRJ folder. However, if you bought it through the Marketplace, I'm not sure where they are.

On my G33 there is no limit stop between 0 and Full flaps. I think this is why the POH only has one flap extension speed of 122 kts. Is there an STC for my model that would have incremental flap switch limits between Up - 10 - 20 - Down? If so does the STC allow for a higher speed flap extension? I see in the A36 POH they can extend12 degrees at 152. I think it would be beneficial to put flaps down at a higher speed.

There is no STC that I am aware of that allows a higher flap extension speed. On aircraft without the approach flap detent , the flaps can be stopped at any point by putting the handle in middle detent. It still needs to be under VFE to start any flap extension.

For example, when I am landing at busy airport such as the Tampa Florida airport, leaving the flaps up permits me to fit into the higher speed mix much easier. When I am about 1/2 mile from the airport, I lower my landing gear. With the gear down and the flaps up, I begin my flare about the start of the runway and I am able to touch down about 80 MPH about 1500 feet from the beginning of the runway. I am able to exit the high speed turn off without any problems.

I would also recommend that you find a rural airport the fly to. Less traffic. Then practice slow flight without flaps and then with flaps. In other words, be comfortable flying near stall speed (52 knots dirty and 62 Knots clean).

Should you have to go around, going to full power will put you into an uncomfortable condition when your flaps and gear are down. So, when you start a go around, do NOT shove the throttle in as fast as you can. Depending which engine you have in your aircraft, you may find that the "P" factor will put you into a dangerous condition as the plane wants to turn left and you are trying to push in your right rudder. Last year, a brand new Cirrus with a 550 was landing at my home airport. The winds are often goofy here because of the airport being between river bluffs. What happened that day was the pilot encountered a sudden X wind. He shoved in the throttle. The Cirrus then began to roll to the left (P factor). His left wing tip hit the grass and then his nose hit the grass.

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