732 Takeoff Flaps

[aviatorhi]

First time working with a 737-200 so bear with me...

Going through the FPPM and trying to figure out why higher flap setting V speeds are not provided for higher takeoff weights. I got my rating on a CL so not terribly familiar with the Originals but it doesn't make sense to be to be limited to using higher flap settings (15,25) only at light weights when they are most beneficial at higher weights... any help on why this might be?

[JammedStab]

More flap will help you get the same weight at a lower speed and there will likely be no problem.

But, the authorities want you to be able to still climb out and meet a certain climb gradient if you lose an engine at the most critical moment(V1) under the most critical situations.

The 737-200 is not exactly overpowered. Especially ones with the lower thrust engines. So the only way you can meet that required climb gradient in the unlikely event of an engine failure at the worst possible moment where you are continuing on is to use less flap. Which means that you need a higher rotation speed which means that you need a longer runway.

But if you were to break the rules, and knew what you were doing, the plane is capable of the higher flap settings and lower V speeds. In Africa perhaps?

We didn't even have takeoff info with us for flaps 15 and 25. And Flaps 10 was rare as well.

[aviatorhi]

Well, this isn't Africa, though I've been in similar places and done all that.

While a 732 isn't exactly overpowered, as you say, that shouldn't preclude takeoff performance data from being available. Flew the 727 and higher flap settings (30*) will result in a higher runway performance than climb performance, but that's why we carry the performance manual and a brain. Trying to figure out why Boeing isn't even bothering to provide the information for the 737. On face value the 722 and 732 should have roughly similar capabilities as a % of MTOW.

Point is, if I want to sacrifice a bit of climb performance for better runway performance the FPPM should provide me with the information I need to make the appropriate tables, yet I don't see that anywhere, and I don't recall seeing any restriction against using higher flap settings over a certain weight in the FCTM or the AOM.

[Mach E Avelli]

It's been a while now since I operated the 732 but I recall that flap 5 was about optimum on runways over 2000m and flap 10 best for shorter runways. Flap 15 climb limits ruled that one out for operations in warmer climates. This is for dash 15 engines. We got our performance data from Air New Zealand but they no longer operate the 732 so maybe you need to look to South America now.
If you PM me I can put you in contact with a guy in Chile who is the full bottle on performance and probably still has a program for the B732 .

[JammedStab]

Well, this isn't Africa, though I've been in similar places and done all that.

While a 732 isn't exactly overpowered, as you say, that shouldn't preclude takeoff performance data from being available. Flew the 727 and higher flap settings (30*) will result in a higher runway performance than climb performance, but that's why we carry the performance manual and a brain. Trying to figure out why Boeing isn't even bothering to provide the information for the 737. On face value the 722 and 732 should have roughly similar capabilities as a % of MTOW.

Point is, if I want to sacrifice a bit of climb performance for better runway performance the FPPM should provide me with the information I need to make the appropriate tables, yet I don't see that anywhere, and I don't recall seeing any restriction against using higher flap settings over a certain weight in the FCTM or the AOM.

Don't believe that the 727 is allowed to takeoff at flaps 30. At least not when I flew them. Max we used was Flaps 25. I suspect that the Boeing AFM has the desired info on the 732.

[aviatorhi]

While you're right that 25 was the max, after you convert the wing via STC (Dugan) the new max is 30* (in actuality something like 27).

Am looking through the AOM and AFM but can't find any worded restriction other than the lack of data on the V-speeds card.

PM on the way Mach.

[BobM2]

it doesn't make sense to be to be limited to using higher flap settings (15,25) only at light weights when they are most beneficial at higher weights... any help on why this might be?
Higher flap settings are NOT beneficial at higher wts since the added drag reduces climb gradient. As I recall, 727 takeoffs at the highest weights required no more than flaps 5. If you fly the 737-200 long enough, you will encounter "improved climb" takeoffs at heavy wts on long runways that require not only reduced flap settings but also increased V speeds to meet minimum engine-out climb gradients. The T. O. must be balanced between the runway available & the engine-out climb capability of the aircraft.

[A37575]

The 737-200 ADV has a Flight Planning and Performance Manual which gives all the information you need to select take off flap settings from flaps one through to Flaps 15. These are generally in graph form rather than tabular. In my former company in the Central Pacific Region, we were advised by Boeing (who supplied the individual runway analysis on request) to in general use Flaps 10 which was a compromise between short runways (5600 ft length) and longer runways utilising V2 overspeed weights (called Improved Climb). With Flaps 10 and Improved Climb we could take off at the max structural and still not be climb limited (just). Max structural was 53 tonnes.

Some of the airstrips we operated to were coral base and could be quite uneven and bumpy. Where possible, we would use Flaps 25 in order to have lower VR and get of the ground early due to the shaking and rattling caused by uneven surface. As the airline didn't carry many passengers the take off weights were low, so Flap 25 wasn't a problem. On long runways we occasionally used Flap 2 at high weights rather than Flaps 1. The second segment climb limits varied slightly between the two flap settings but we were able to get off at max structural with no performance problem.

The advantage of flaps 2 was in the flap retraction phase, where after take off, the retraction from flap 2 to flap 1 took place at V2 +15. With flap 1 take off, flap retraction from Flaps 1 to Flaps up was 190 knots. It was all too easy to inadvertently go for flaps up at V2+15 with Flap 1 take off which would have been dicey. Flap 2 meant you did make the first flap retract at V2+15 which was standard for all normal take off's except for flaps 1.

[aviatorhi]

Higher flap settings are NOT beneficial at higher wts since the added drag reduces climb gradient. As I recall, 727 takeoffs at the highest weights required no more than flaps 5.

Wrong. That's all well and good when you've got 12000 feet of pavement in front of you. However, when you're at MTOW with only 6000 feet of pavement you have no choice but to use 30* and be on the edge of both the takeoff and climb performance.

@A37575...

I am looking at the FPPM and it is quite enigmatic as compared to the FPPMs for later iterations of the airframe. It's mainly a question of why the higher weights are not allowed for the higher flap settings. I understand the degradation of climb performance with higher flap settings, at the same time I'm used to being able to tabulate the tables and let them say what they will say. The reason it's of particular curiosity to me is that there is no prohibition I can find in regards to using a high flap setting at a high weight apart from lack of performance data. In my experience if something of this nature is a significant enough issue Boeing will address it somewhere (FCTM, AOM, ATM, FPPM, etc.) with a simple statement of "Don't do it" (usually in "warning" text), yet that doesn't appear to be the case here.

[PantLoad]

As a general rule ("general" is th ekey word), more flaps means shorter takeoff roll, but decreased climb gradient. Conversely, less flaps means longer takeoff roll, but better climb gtadient.

Boeing even has "Improved Climb" which is generally used if runway length and first segment climb issues are not the problem, but climb gradient is. Improved climb is generally used with FLAPS 1.

Again, "general" is the key word.

On the newer planes, the ones with sretched fuselage (e.g. 737-400), FLAPS 1 is not allowed, due to tail strike possibilities.

Various flap settings are certified....your individual airline may or may not publish data for takeoffs with all the flap settings that the aircraft was certified to do.

For example, my airline (I'm retired, now.) used to publish data for FLAPS 2 for the 737-200. Not surprisingly, usually (instead of 'generally') your performance would be a mix between FLAPS 1 and FLAPS 5 when using FLAPS 2.

Same goes for the mini-Bus. Generally, more flaps means shorter takeoff roll, but poorer OEI climb gradient. Less flaps means the opposite. Again...."generally". I've seen, however, due to obstacles on the first segement, a lower flap setting giving better performance for takeoff roll.

So, again, "generally".....

I've also flown the 727. Basically the same goes with that, as well. A takeoff out of Denver on a July or AUgust afternoon....well, FLAPS 5 may be the only way to get out of there without offloading weight. Your takeoff roll is in miles, not feet, but an engine loss at or after V1 is better handled.... Density Altitude is really high....your climb performance with OEI is poor with a FLAPS 15 takeoff.....

So, if you have a lot of runway, it's hot and high elevation, and you're heavy, less flaps may be better....


Fly safe,


PantLoad

[aviatorhi]

As I stated before I understand the relationship between runway and climb performance, flap settings and so on. My only question is why Boeing is not providing the data or not openly stating a prohibition against the higher settings at higher weights. That is my only question.

While we can delve through thousands of possible scenarios in the area of operations I'm concerned with (and what leads me to say higher flap settings are beneficial at higher weights) is that I / the operation am / are in a short runway, average temperature, high payload(s) environment. Nine times out of ten the runway is limiting for us, climbs rarely if ever limit us.

Again, I'm not trying to discuss the pluses and minuses of flap settings from an operational standpoint. I'm talking from the standpoint of calculating performance charts, manuals and speed tables to be used in the operation (which are based on the FPPM). Now, as I said, Boeing is not providing the information it has provided for every other Boeing I've worked with before, if I ask them, they clam up, which is why I've turned to the community hoping to get an answer as to why there appears to be a de facto prohibition on this configuration, though not an official one.

[john_tullamarine]

My only question is why Boeing is not providing the data or not openly stating a prohibition against the higher settings at higher weights

I'm speculating only, but ..

(a) the OEM provides what is required for certification

(b) in addition .. some extra stuff which will sell lotsa aeroplanes

(c) in addition .. additional extra stuff for which the commissioning customer pays a princely sum

(d) the early 737 archaics were intended for back blocks flying which generally entails shorter strips but not necessarily paddock ops, ergo, no fancy additional data either for super short or super long runways.

(e) there is no prohibition, per se, it's just a case of someone has to pay for the stuff to appear in the AFM if a particular customer wants to do something different with the aeroplane.

In the meantime, one uses the existing AFM data to advantage within the limitations inherent in those data.

[PantLoad]

Sorry, didn't understand your question...

Boeing has charts and graphs out the XXX. If you're a customer, I'm sure they'll offer any help you may need...maybe free, moaybe not.

So, if you want to take off with FLAPS 25, or FLAPS 30, or whatever, I'm sure, if it's legal and certified, they have the graphs and charts for such.

There used to be an operator in Alaska who operated the 737-200, modified for gravel strips, and did FLAPS 25 takeoffs. No problem getting performance data...Boeing had it in the top desk drawer.

Again, sorry, did not carefully read your question.

Fly safe,

PantLoad

[BobM2]

Wrong. That's all well and good when you've got 12000 feet of pavement in front of you. However, when you're at MTOW with only 6000 feet of pavement you have no choice but to use 30* and be on the edge of both the takeoff and climb performance.

You most certainly DO have a choice & that is to go back to the gate & offload weight until the aircraft is legal to make a takeoff on that runway under existing conditions. I don't know what outfit you're working for, but I would guess a freight hauler in a part of the world where crewmember's life is cheap & profit is the only motive. Otherwise, you would have had ground school courses & would have a basic understanding of how a balanced-field takeoff is computed. The reason Boeing doesn't show takeoff numbers for higher flap settings at higher weights is because THE AIRPLANE CAN'T MEET CERTIFICATION CLIMB REQUIREMENTS UNDER THOSE CONDITIONS.:ugh:
I would guess your company is on Boeing's do not fly list.

[aviatorhi]

Sorry Bob, but the aircraft does meet climb requirements. I suppose the engineering company that wrote our performance books, as well as those of dozens of other FAA certificated carriers has no idea what its doing though. Will make sure to have them contact you to get the updated information.

Additionally, you're making terribly bold statements regarding how an aircraft performs without knowing the equipment installed, modifications made procedures used or environment of operations (meteorological and physical).

@John and Pantload, thanks for those replies, something I see as at least plausible.

[A37575]

I am having a problem with the basic understanding of your question and exactly what you are getting at. I suspect others are having the same problem.

Although you have received many well thought out and intelligent replies you keep on asking (my interpretation of what you want, anyway) why Boeing (for example) don't publish take off flaps settings and climb performance for Flap 40 for example. I suggest you write to Boeing Flight Training and Services and ask them. Then again I might be completely wrong in interpreting what you are on about:ugh:

Are you serious about wanting to know why there are no performance charts for the higher (Flap 30/40 in 737) when it should be obvious the weights would be so low as to be impracticable?

[aviatorhi]

Flaps 30/40 I understand. I'm referring to authorized flap settings only.

Now let me clarify. I'm not asking this as a pilot sitting in the airplane wondering why Boeing or my airline haven't given me performance numbers for certain settings.

I'm asking this as a person in the office writing out speed cards, etc, and wondering why Boeing haven't provided the information that is normally provided for every other aircraft of theirs I've worked with.

Also, I'm not even talking about a performance chart here, if you go back to my original question this was a question regarding the V-speed chart. Which will normally provide weights in excess of even MTOW on many aircraft (this is related to takeoff / performance computations when taking into account performance limiting MEL items). My only question has been why Boeing do not provide data on the 732 which I've seen provided in all their other FPPMs, or at least a statement of "NOT AUTHORIZED" or something to that effect. As I've, also, said they clam up (don't want to say) why this is, I suppose if we throw money at the problem it might solve itself, though I wanted to get some thoughts from the community as well, as I'm sure others more experienced than myself have done FPPM data work before.

In regards to the performance being so low it's impractical, that's really something that is an unknown until you've made the tables for a particular aircraft. In example, if I were to take two 727-223s today, which rolled out days apart from Boeing with the exact same configuration, and made performance tables for each you would find that their performance capabilities vary greatly in the exact same environmental conditions due to a number of factors. Long story short, one aircraft would be perfectly capable of doing a takeoff at MTOW off a 6000 foot runway with Flaps 30* (25) and meet climb performance limits, while the other aircraft would end up in the weeds and / or be unable to meet climb performance limits.

[john_tullamarine]

.. their performance capabilities vary greatly in the exact same environmental conditions due to a number of factors

.. might we enquire as to what those factors might be ?

[aviatorhi]

Engines installed (big difference between -7s and -217s), wing modifications via STCs (winglets, flap droop, etc.), Limiting the forward CG envelope to a point further aft (Boeing approved procedure to increase runway performance), flap retraction schedules, tires installed, etc.

[john_tullamarine]

Thanks.

Guess we understand which rolled out days apart from Boeing with the exact same configuration to mean different things ..

[Mach E Avelli]

Whatever you do, if your runways are less than 2500 metres, do NOT get suckered in to the wing/flap modification that is marketed for this old beast.
Although it is not particularly expensive, it totally ruins a good airframe.
It was created specifically for a very long runway/high elevation situation - like Mexico City - to overcome climb limitations. It works best at Flap 1 or 2 and I think it offers an intermediate setting at about 7 for situations where 5 or 10 is not optimum (but I have forgotten the details of this).
On runways less than about 2000 metres it is more likely that accelerate-stop will be the performance driver. Between 2000 and 2500 metres optimum take-off weight usually becomes a juggling act between field limits and climb limits.
The modified wing won't help here, as V1 for any given weight/flap is much the same with or without the modifications. Distance to reach V1 is basically a function of thrust versus weight and for a given weight that distance wouldn't vary much even with NO wings! The modified wing/flap may marginally improve acceleration (by getting the weight off the wheels a bit sooner), but it would be so marginal that it would not be worth the expense. Bigger engines - like dash 17s - are the only cure.
The AFM will give you all the info you need to manually calculate speeds etc, but one of the after-market performance providers will do it quicker and probably more accurately. At a cost, but what is your time worth?
Also they have all the survey data, so when the Feds come calling to ask how you derive your numbers, it is easier to pass the buck. I certainly would not be making up my own speed cards by the pidooma method.

[aviatorhi]

John, don't you think that an aircraft which was in one configuration 30 years ago may be in a different on now? My point was that just because 30 years ago a given airplane with a certain configuration couldn't take off heavy weight at flaps 25 doesn't mean it isn't able to today at 30*.

@Mach
The flap mods I spoke of don't apply to the 732 I'm working with. Our performance for this and other aircraft I work with are always obtained from a very reputable engineering and performance firm I've worked with before, but speed tables are always in house.

Thanks for the reply though, helpful in trying to shed light on this for myself.

[john_tullamarine]

don't you think that an aircraft which was in one configuration 30 years ago may be in a different on now

Absolutely. However, to an engineer, configuration means configuration control (as an ongoing process). Your post wasn't clear as to your intent ?

I suggest, though, that your concern still revolves around AFM certification processes and who pays - an OEM just isn't interested in being a benign and benevolent institution - it's purpose is to make lotsa dollars. You want/need something out of the ordinary, then be prepared to fork out lotsa dollars for the paperwork/mod/whatever.

[aviatorhi]

I guess I could have worded that a little clearer, the point I was trying to make was that if you couldn't meet climb requirements 30 years ago with -7s slung on the airplane it would have nothing to do with what the airplane can to today.

I agree with your second paragraph that this is a classic case of needing to throw more money at the problem. What struck me as odd, though, is that this is the only type I've worked with which has this issue. On other types the information was always available without the need to purchase additional items.

[john_tullamarine]

On other types the information was always available without the need to purchase additional items.

.. and that comes back to OEM discretion -

(a) required stuff IN - CHECK
(b) optional stuff likely to make us lotsa dollars IN - CHECK
(c) stuff we decided not to include PAY LOTSA DOLLARS - IN - CHECK

No reason why one OEM on one model shouldn't come up with a different compromise documentation solution to the next ...

[aviatorhi]

Thanks for the replies, wasn't saying there was or wasn't a reason, was saying I didn't know if there was or wasn't and was hoping to get information on the matter. For that I thank you.