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Is It Possible Or Practical To Droop 737 Ailerons?  
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Posted (1 year 7 months 1 week 16 hours ago) and read 7712 times:

There have been a few threads about the effects of going MAX will be on 737 take off lengths. I am wondering if drooping the ailerons, (if it could be done), on the 737 could make an appreciable difference in the take of and landing performance.

The roll spoilers seem to me to be more effective in controlling roll than the ailerons, (but that's just my impression), so my guess is drooping wouldn't have a significant negative effect on roll control.

Any ideas?


What the...?
20 replies: All unread, jump to last
 
User currently offlineTristarsteve From Sweden, joined Nov 2005, 3930 posts, RR: 34
Reply 1, posted (1 year 7 months 1 week 7 hours ago) and read 7542 times:

The ailerons on the B737 are cable operated from a pulley in the wheel well. The control system has not really changed since the -200, and is not yet proposed to change for the MAX. To droop the ailerons would mean inserting actuators into this control run somewhere. I really can't see it happening. The B737 needs fly by wire ailerons to accomplish droop.

User currently offlineboeingfixer From Canada, joined Jul 2005, 525 posts, RR: 0
Reply 2, posted (1 year 7 months 1 week 5 hours ago) and read 7485 times:

As Tristarsteve said, the B737 aileron system, in its current form, is not conducive to incorporating drooped ailerons. On the B737 the aileron actuators are in the main gear wheel well and cables run from there to move the ailerons. Aircraft that have drooping ailerons have the Power Control Actuators right at the control surface. To do this with the B737 would be a big undertaking and also require a backup hydraulic system to be installed due to the loss of the manual reversion system. I could see it happening with a fresh design but it won't be on the MAX.

BTW, the MAX is going to have a FBW spoiler system which is a vast improvement over the existing spoiler mixer/ratio changer system.

Cheers,

John



Cheers, John YYC
User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 3, posted (1 year 7 months 1 week ago) and read 7366 times:

Quoting boeingfixer (Reply 2):

I forgot about the FBW spoilers. Maybe they could go whole hog and do the ailerons as well, which seems like it would vastly simplify that system. Then they could work some droop into the mix.

On a related note, how much effect does a plane get from drooping the ailerons?



What the...?
User currently offlineStitch From United States of America, joined Jul 2005, 29674 posts, RR: 84
Reply 4, posted (1 year 7 months 1 week ago) and read 7353 times:
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AviationWeek evidently ran an article (the link is now dead) saying the 737 MAX will feature an improved trailing edge from the CLEEN programme, incorporating the “mini-split flap” technology, a re-rigged outboard flap and drooped aileron.

User currently offlineDocLightning From United States of America, joined Nov 2005, 18679 posts, RR: 58
Reply 5, posted (1 year 7 months 6 days 23 hours ago) and read 7319 times:

Why is it not possible to do something to the flight software that would droop the aileron? Why does the position of the actuator make a difference?

User currently offlineRavenTech From United States of America, joined Aug 2012, 41 posts, RR: 0
Reply 6, posted (1 year 7 months 6 days 23 hours ago) and read 7307 times:

Quoting DocLightning (Reply 5):

Since the 737 ailerons are directly linked to the cockpit controls, any aileron droop would need to override that direct link. I would actually be surprised if there was any flight software that you could update aside from autopilot type connections. Aileron droop would probably require 1) A redesign of the aileron part to allow for the droop independant of the control cable or 2) convert to Fly-by-Wire.


User currently offlineJoeCanuck From Canada, joined Dec 2005, 5318 posts, RR: 30
Reply 7, posted (1 year 7 months 6 days 21 hours ago) and read 7249 times:

Quoting Stitch (Reply 4):

I didn't hear that...thanks...I'll see if google really is my friend.

I'll have to get my geek on and look for schematics for the 737 aileron system.

Google and ye shall find...but not always...except this time I did;

http://www.aspireaviation.com/2012/0...-engined-narrowbody-battle-begins/

Quote:
The elimination of an aft-body joint, coupled with an optimised engine core on the CFM Leap-1B engine, as well as the adoption of an improved trailing edge that incorporates the “mini-split flap” technology, a re-rigged outboard flap and drooped aileron from the US Federal Aviation Administration (FAA) continuous lower energy emissions noise (CLEEN) programme beginning in end-third quarter this year aboard an American Airlines 737-800 that has entered into final assembly, will make the 737 MAX even better.

Now I just gots to know how the heck they are going to do it.

[Edited 2012-09-12 17:56:29]


What got me going on this is I used to do a lot of R/C flying, (where I could do all the stupid things I wanted with a plane that I was too chicken to do while I was driving one), and I had some delta winged planes which needed elevon mixing. I always did it the easy way, essentially fly by wire. I could never figure out how they did it in the good old days, before fly by wire.

The old delta wings and even the V-tailed Bonanzas. The amazing simplicity of it blew me away...truly an inspired invention for the geek hall of fame.


[Edited 2012-09-12 18:38:37]


What the...?
User currently offlineyeelep From United States of America, joined Apr 2011, 632 posts, RR: 0
Reply 8, posted (1 year 7 months 6 days 3 hours ago) and read 7070 times:

Quoting Stitch (Reply 4):
AviationWeek evidently ran an article (the link is now dead) saying the 737 MAX will feature an improved trailing edge from the CLEEN programme, incorporating the “mini-split flap” technology, a re-rigged outboard flap and drooped aileron.

The CLEEN program is purely a technology demonstrator. Some or none of the tested items may be incorporated into the MAX. As you can see below, the drooped aileron is only a drooped tab. That is easily done through a change in the tab rod adjustment. I'm guessing they are doing it to seek improvements during cruise.
http://www.albint.com/businesses/aec...ing%20Edge%20-%20AvWeek%207.23.pdf
Quote:
Configurations chosen for the adaptive trailing-edge flight test include
a fixed mini split flap for the inboard
sections out to around mid-span and
a drooped aileron tab. The outboard
fixed trailing edge will also be modified to test both a mini plain and mini
split flap. “They are all looking at
better ways to make the trailing edge
move without causing more drag,”
says Mike Carriker, Boeing’s new airplane product development chief pilot.
Quoting DocLightning (Reply 5):
Why is it not possible to do something to the flight software that would droop the aileron?

The flight software will only control the autopilot actuators, which are connected to a shaft that will rotate with input from the autopilot, control yoke or trim actuator. The shaft outputs to both aileron PCU's(power control units), there is no independent input to the PCU's so they cannot be directed to move in opposite directions.

Quoting JoeCanuck (Reply 3):
I forgot about the FBW spoilers. Maybe they could go whole hog and do the ailerons as well, which seems like it would vastly simplify that system. Then they could work some droop into the mix.
The spoilers are a secondary flight control while the ailerons are a primary. I don't think there is the slightest chance that the FAA or other regulators would allow them that change while keeping the current Type Certificate.

Quoting DocLightning (Reply 5):
Why does the position of the actuator make a difference?

At its most basic its location doesn't make any difference. The problem with the 737 is the left and right ailerons are not completely independent from each other between the actuators(PCU's) and the ailerons. Each PCU outputs to a quadrant that are stacked together. These operate separately but are restricted in their independent movement by a lug on one quadrant that fits between a fork on the other. One possible way they could get drooped ailerons is to somehow modify that lug and the PCU's. Of course its not as simple as that due to having to keep all the current failsafe mechanisms in place. But I'm sure it could be done without losing manual reversion. Whether its worth it, who knows.


User currently offlineGoldenshield From United States of America, joined Jan 2001, 5845 posts, RR: 15
Reply 9, posted (1 year 7 months 6 days 2 hours ago) and read 7042 times:

Quoting Tristarsteve (Reply 1):
The ailerons on the B737 are cable operated from a pulley in the wheel well. The control system has not really changed since the -200, and is not yet proposed to change for the MAX. To droop the ailerons would mean inserting actuators into this control run somewhere. I really can't see it happening.

It's possible to achieve this, with a modified setup. Basically, instead of having long cables running through out the airplane, section them off (Left, right, forward) so that they operate push-rods instead. This way, a slide-type mechanism can be introduced using the pushrods, and that in turn will introduce a droop into the ailerons based on the position of the flaps.

I have a similar mechanism on my sailplane, except that it's 100% pushrods.



Two all beef patties, special sauce, lettuce, cheese, pickles, onions on a sesame seed bun.
User currently offlineStitch From United States of America, joined Jul 2005, 29674 posts, RR: 84
Reply 10, posted (1 year 7 months 6 days ago) and read 7009 times:
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Quoting yeelep (Reply 8):
The spoilers are a secondary flight control while the ailerons are a primary. I don't think there is the slightest chance that the FAA or other regulators would allow them that change while keeping the current Type Certificate.

The FAA did allow the 747-8 to move to FBW for it's outer ailerons and they can droop ( I understand that unlike the 747, the 737 does not have inboard ailerons, so perhaps that was a factor in allowing the outboard units to be moved to FBW ).


User currently offlineEskimotail From United States of America, joined Mar 2010, 35 posts, RR: 0
Reply 11, posted (1 year 7 months 4 days 17 hours ago) and read 6765 times:

On current 737 there is approx 8 feet of fixed trailing edge outboard of the ailerons and inboard of the wingtip. This will be the area where the new drooping surfaces will appear.

User currently offlineEskimotail From United States of America, joined Mar 2010, 35 posts, RR: 0
Reply 12, posted (1 year 7 months 4 hours ago) and read 6395 times:

Quoting Eskimotail (Reply 11):
On current 737 there is approx 8 feet of fixed trailing edge outboard of the ailerons and inboard of the wingtip. This will be the area where the new drooping surfaces will appear

Quoting mysel.....
http://www.boeing.com/Features/2012/...bca_eco_demonstrator_09_17_12.html

You can see the new droopy surfaces in this video.
Remember there is always a push and shove to preserve the existing certification as much as possible. In the case of the ailerons, it is significantly less risky (from certification standpoint) to develop and install a new system that accomplishes the same effect without monkeying with the legacy system.


User currently offlinestrfyr51 From United States of America, joined Apr 2012, 788 posts, RR: 0
Reply 13, posted (1 year 6 months 4 weeks 1 day 17 hours ago) and read 6329 times:
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the 737 COULD have aileron droop installed by inserting a ratio changer in the aileron CONTROL system, the L1011-500 had drooped ailerons and was NEVER a fly by wire airplane. The complexity of the ratio changer would be a real Pain in the Wazoo and probably controlled by the Air data computer in a limited flight regime though the 737 I doubt would ever need the system as the 737 wing does not require Load alleviation. This might all be good stuff for the 737 replacement still to come in the next decade. because by then nearly ALL New commercial airplanes will be fly by wire.

User currently offlineLH707330 From United States of America, joined Jun 2012, 592 posts, RR: 0
Reply 14, posted (5 months 2 weeks 4 days 21 hours ago) and read 2879 times:

Quoting Eskimotail (Reply 11):
On current 737 there is approx 8 feet of fixed trailing edge outboard of the ailerons and inboard of the wingtip. This will be the area where the new drooping surfaces will appear.

Does anybody know why they left this section outboard instead of moving the ailerons further out for better leverage and more flap span like on the Airbii? Is there an issue with aileron reversal?


User currently offlineMir From United States of America, joined Jan 2004, 21085 posts, RR: 56
Reply 15, posted (5 months 2 weeks 4 days 21 hours ago) and read 2870 times:

Quoting LH707330 (Reply 14):
Does anybody know why they left this section outboard instead of moving the ailerons further out for better leverage and more flap span like on the Airbii?

Possibly the ailerons would be too effective if they were further out. With FBW you can make very minute adjustments to the control surfaces, but with the 737's manual controls it's harder, and could make the plane overly sensitive in roll.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineLH707330 From United States of America, joined Jun 2012, 592 posts, RR: 0
Reply 16, posted (5 months 2 weeks 4 days 6 hours ago) and read 2616 times:

Quoting Mir (Reply 15):
Possibly the ailerons would be too effective if they were further out. With FBW you can make very minute adjustments to the control surfaces, but with the 737's manual controls it's harder, and could make the plane overly sensitive in roll.

I guess this makes sense, but couldn't you accomplish the same thing through less control surface deflection on an aileron further out, or even make said moved aileron smaller? I'd imagine there's an easier solution to make the A320 layout non-FBW compatible, maybe my moving where the cables attach, etc.

The other question would be, what advantages does the 737NG wing layout have over the A320?


User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 17, posted (5 months 2 weeks 4 days 1 hour ago) and read 2500 times:

Quoting LH707330 (Reply 16):
The other question would be, what advantages does the 737NG wing layout have over the A320?

First the re aileron placement, I think your proposal about aileron reversal is the main reason they are sitting a bit in on the wing.

Secondly which has the better wing? They are pretty similar in area and span but the NG wing contains considerably more fuel, 20.9 tonnes vs 18.8 tonnes for the 320 series. This to me is logical, the NG wing is 10 years younger and therefore has a more modern supercritical profile (read thicker for the same transonic drag ), it therefore can take more fuel and should be lighter everything else being equal.

The in wing fuel is a big deal for the 320 and 737 as they are heavily fuel limited, the 738 gets to 3100nm on wing fuel, the 320 to 2900nm, then it is cargo hold tanks needed and these take cargo/luggage space. A 320 need 1 cargo tank to match a wing fuel 738.

The whole marketing BS game around their and their re-engined siblings range is playing with this fact, Boeing says "both are equipped with 1 cargo tank"  Wow! and Airbus "cargo tanks included"     .



Non French in France
User currently offlineMir From United States of America, joined Jan 2004, 21085 posts, RR: 56
Reply 18, posted (5 months 2 weeks 3 days 23 hours ago) and read 2455 times:

Quoting LH707330 (Reply 16):
I guess this makes sense, but couldn't you accomplish the same thing through less control surface deflection on an aileron further out, or even make said moved aileron smaller?

The problem with lesser control deflection is that it becomes difficult to be precise enough at high speed, and that it might not be enough at low speed. FBW solves the precision issue. And making the aileron smaller would run the risk of not having enough authority at low speeds.

-Mir



7 billion, one nation, imagination...it's a beautiful day
User currently offlineJetlagged From United Kingdom, joined Jan 2005, 2532 posts, RR: 24
Reply 19, posted (5 months 2 weeks 3 days 18 hours ago) and read 2335 times:

Quoting Tristarsteve (Reply 1):
The ailerons on the B737 are cable operated from a pulley in the wheel well. The control system has not really changed since the -200, and is not yet proposed to change for the MAX. To droop the ailerons would mean inserting actuators into this control run somewhere. I really can't see it happening. The B737 needs fly by wire ailerons to accomplish droop.

As you say, actuators could be inserted to create droop, but it's not true that would require FBW ailerons.

Quoting strfyr51 (Reply 13):
the 737 COULD have aileron droop installed by inserting a ratio changer in the aileron CONTROL system, the L1011-500 had drooped ailerons and was NEVER a fly by wire airplane.

The A300 also had drooping ailerons, on all versions, not requiring FBW.

Whether aileron droop would be worth all the trouble to install is another issue. As long as control redundancy wasn't affected I don't see why it would require recertification (apart from the added actuators). But I'm not sure what benefits would be obtained as the existing high lift system is more than capable.



The glass isn't half empty, or half full, it's twice as big as it needs to be.
User currently offlineferpe From France, joined Nov 2010, 2792 posts, RR: 59
Reply 20, posted (5 months 2 weeks 2 days 20 hours ago) and read 2141 times:

Quoting Jetlagged (Reply 19):
The A300 also had drooping ailerons, on all versions, not requiring FBW.

Whether aileron droop would be worth all the trouble to install is another issue. As long as control redundancy wasn't affected I don't see why it would require recertification (apart from the added actuators). But I'm not sure what benefits would be obtained as the existing high lift system is more than capable.

You are correct in that it is doable on a mechanical basis and it would not be to complicated, you just have to twist the pully a bit and you would off-set the neutral point of the ailerons to a bit droop down. I guess the point is if you go to the trouble of changing anything you have to certify the solution and the whole flight consequences thereof and then a more effective/lighter FBW solution might be preferable. Anyway that is, it is quite doable and it would help with the severe constrains the 737-9 has with pitch angle on take-off.



Non French in France
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