JoeCanuck From Canada, joined Dec 2005, 5031 posts, RR: 29 Posted (8 months 1 week 6 days 21 hours ago) and read 4065 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.
Tristarsteve From Sweden, joined Nov 2005, 3693 posts, RR: 34 Reply 1, posted (8 months 1 week 6 days 12 hours ago) and read 3895 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.
boeingfixer From Canada, joined Jul 2005, 490 posts, RR: 0 Reply 2, posted (8 months 1 week 6 days 10 hours ago) and read 3838 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.
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?
Stitch From United States of America, joined Jul 2005, 26718 posts, RR: 83 Reply 4, posted (8 months 1 week 6 days 5 hours ago) and read 3706 times:
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.
DocLightning From United States of America, joined Nov 2005, 16824 posts, RR: 57 Reply 5, posted (8 months 1 week 6 days 4 hours ago) and read 3672 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?
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.
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.
yeelep From United States of America, joined Apr 2011, 526 posts, RR: 0 Reply 8, posted (8 months 1 week 5 days 8 hours ago) and read 3423 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.
Goldenshield From United States of America, joined Jan 2001, 5441 posts, RR: 12 Reply 9, posted (8 months 1 week 5 days 7 hours ago) and read 3395 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.
Stitch From United States of America, joined Jul 2005, 26718 posts, RR: 83 Reply 10, posted (8 months 1 week 5 days 6 hours ago) and read 3362 times:
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 ).
Eskimotail From United States of America, joined Mar 2010, 33 posts, RR: 0 Reply 11, posted (8 months 1 week 3 days 22 hours ago) and read 3118 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.
Eskimotail From United States of America, joined Mar 2010, 33 posts, RR: 0 Reply 12, posted (8 months 6 days 10 hours ago) and read 2748 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
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.
strfyr51 From United States of America, joined Apr 2012, 488 posts, RR: 0 Reply 13, posted (8 months 5 days 22 hours ago) and read 2682 times:
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.
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