Monocleman From United States of America, joined Apr 2001, 137 posts, RR: 0 Posted (14 years 9 months 2 days 12 hours ago) and read 3081 times:
Being just a lowly flightsimmer, I always figured spoilers were only for slowdown on rollout. Then, reading more about aerodynamics and spoilerons and the such, I learned that, true to their name, they spoil the lift over a wing. So, what are their true purposes? In flight, is the main purpose to decrease airspeed or to make an aircraft descend faster? And during landing, I can see their main purpose as to kill lift to decrease the likliness of a bounce rather than slow down the aircraft. Then again, I may be completely wrong. Anybody care to enlighten me?
Iainhol From , joined Dec 1969, posts, RR:
Reply 1, posted (14 years 9 months 2 days 12 hours ago) and read 3008 times:
I am sure an airline pilot can give you a better answer but here is a bit of info I know.
During flying spoilers are used when flaps are down to assist ailerons, to turn the aircraft.
Once you are down on teh ground the spoiler deploy (in more advance aircraft the do it automatically) which kills lift putting more weight on the landing gear, making the brakes work better!
CYKA From , joined Dec 1969, posts, RR:
Reply 2, posted (14 years 9 months 2 days 12 hours ago) and read 3004 times:
Spoilers are not used to assist the ailerons in flight. They are only used for slowing down the a/c during flight and on touchdown to help force the wheels on the strip, assisiting in the braking process.
777236ER From , joined Dec 1969, posts, RR:
Reply 4, posted (14 years 9 months 2 days 11 hours ago) and read 2994 times:
Spoilers (spoilerons) ARE used in flight to provide additional roll control. Usually, the spoilers only move to about 60-75% while acting as spoilerons, but they tend to be used at all stages of flight, regardless of flap positions and/or speed.
CYKA From , joined Dec 1969, posts, RR:
Reply 5, posted (14 years 9 months 2 days 11 hours ago) and read 2992 times:
I still think your both wrong. Spoilers do one thing, go up and down creating drag by counteracting lift. They cant control an aircrafts roll since they are deployed with a single handle meaning that they both go up or down at the same time. The reason you cant see them in the photo above is probably due to some optical effect.
Purdue Arrow From United States of America, joined May 1999, 1574 posts, RR: 7
Reply 7, posted (14 years 9 months 2 days 11 hours ago) and read 2988 times:
Spoilers serve several purposes, each of which have already been addressed. They can be used in flight, at the pilots command, to slow down the airplane or to increase the decent rate. They can also, despite CYKA's assertions, be used to augment the roll capability of the aircraft. Whether or not spoilers aid ailerons in roll control is a function of aircraft design. On aircraft that use spoilers for this purpose, spoilers automatically assist the roll, without extra control input from the pilots. As Iainhol said, most aircraft that do this will use spoilers to assist in the roll once the flaps are extended past a certain position - on a 727, IIRC, the spoilers assist in roll control when flaps are extended to 20 degrees or more.
Modesto2 From United States of America, joined Jul 2000, 2898 posts, RR: 5
Reply 8, posted (14 years 9 months 2 days 11 hours ago) and read 2985 times:
Purdue Arrow is correct. To add one thing. When taxiing after pushback, watch the pilots test the control surfaces. When the aileron moves to the up position, the spoilers will also move. In flight, if you look carefully at the spoilers, you can see them move with an aileron. However, this deployment does not occur during all turns.
JG From United States of America, joined Jun 2005, 0 posts, RR: 1
Reply 10, posted (14 years 9 months 2 days 9 hours ago) and read 2973 times:
My frustration is peaked. Men, why don't you just wait for an answer instead of offering opinion/speculation if you do not know the answer.
Flight spoilers assist in roll on airliners. Ground spoilers deploy upon landing.
There are many experts available to answer your questions. Experts in every aspect of airline ops. This Tech/Ops forum has drifted so far from it's title, it has become obsurd. All of this idle speculation, incorrect opinion, discussion of written test scores, lenghty diatribes of jumpseat experience, et al. Frustrating.
Delta-flyer From United States of America, joined Jul 2001, 2682 posts, RR: 6
Reply 11, posted (14 years 9 months 2 days 7 hours ago) and read 2968 times:
I agree 100% with JG.
People should answer questions only if they are certain of the answer. With all due respect to the young folks in this forum, who are much brighter than the general population, you should defer these questions to people like JG who obviously know - and have the credentials (as indicated in their profiles).
FDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 30
Reply 14, posted (14 years 9 months 2 days 2 hours ago) and read 2958 times:
On the 727, the roll spoilers are utilized at all flap settings. Perhaps what you were thinking about was the outboard ailerons (low speed ailerons) which are in effect locked out with flaps retracted but are *unlocked* as the flaps are extended. The more the the flaps are extended, the range of outboard aileron movement also increases as this a progressive system, not simply an "on - off " system.
Klaus From Germany, joined Jul 2001, 21652 posts, RR: 53
Reply 15, posted (14 years 9 months 1 day 22 hours ago) and read 2943 times:
XFSUgimpLB41X: In addition to roll and braking, the spoilers are also used on the Airbus (i know the A320.. not sure about any boeing models or other Airbus's) in turbulent air to prevent over stressing the wing.
That sounds interesting. How exactly does this work?
Jetguy From , joined Dec 1969, posts, RR:
Reply 16, posted (14 years 9 months 1 day 21 hours ago) and read 2938 times:
Spoilerons are also on some the business jets. The Lear 35s use them and there are several others also. Certain aircraft, like the Beechjet and MU-2 use spoilers exclusively for roll control - they have no ailerons. Spoilers can also be found on many light aircraft. Finally, spoilers are on just about every sailplane ever built for glidepath and speed control. They are very useful tools.
Leigh Pilgrim From United Kingdom, joined Dec 2000, 392 posts, RR: 0
Reply 17, posted (14 years 9 months 1 day 14 hours ago) and read 2921 times:
I could be wrong but here is my opinion,
Spoilers spoil the air flow across the wings, this will in effect slow the aircraft down and decrease in height, if an aircraft is too high the pilot may pull the lever back and deploy both left and right wing spoilers to decrease in height, When the aircraft has just landed the spoilers on each wing will deploy to stop the aircraft bouncing, I dont know if I miss read the info or what, but I have never heard of the spoilers giving Aileron support,
(Boeing 777): Has a special system, that allows the onboard computer to use spoliers as a stablizing device, ie. when in crosswind T/O, the system deploy a small amount of spolier to lessen the effect of turblence. Other A/C may also have this, but I only know it's on 777.
JETPILOT From United States of America, joined May 1999, 3130 posts, RR: 27
Reply 19, posted (14 years 9 months 1 day 12 hours ago) and read 2911 times:
The spoilers on the 727 deploy regardless of flap position when the control wheel is deflected more than 7 degrees (if r emeber correctly thats the right number. You wont find that number in the AOM. It's normaly surperfluous info except here).
Speedbird092 From Canada, joined Apr 2000, 169 posts, RR: 0
Reply 20, posted (14 years 9 months 1 day 10 hours ago) and read 2895 times:
Spoilers are used in flight to slow the plane down quickly (usually on descent). Example, I was nearing my destination in a KLM 747, all of a sudden the plane dipped into a steep descent. The front screen displayed flight information and I saw that the aircraft was flying at above 750km/h until leveling off above 10,000 ft to deploy spoilers and slow down to 250 kts.
During a landing, the spoilers do slow down the airplane while it's still rolling at high speed (it looses efficiency at lower speeds) but its main purpose is to "spoil" lift over the wing putting more weight on the wheels to make for better braking.
By all means correct me if i'm wrong.
A330CFBUS From , joined Dec 1969, posts, RR:
Reply 21, posted (14 years 9 months 1 day 9 hours ago) and read 2890 times:
In regards to whoever it was that mentioned the use of spoilers during turbulence... the reason the spoilers are deployed at this time, is to my understanding, not to minimize the effects of the turbulence, so to speak... but rather the pilot slowing the aircraft to the Vmo "Buffet", or "manouevering" speed... this is the best speed for turbulence penetration, or in other words also, the highest speed for maximum control deflection, should it be necessary. In heavier turbulence, that is anything other than the light stuff... a pilot will slow the aircraft to this speed, it will be less stressful on the aircraft, and if heavier control inputs will be necessary no damage will be incured, and the controls will be most effective at this speed.
Another finer point, when the "spoilers" are deployed in flight, they are actually "speed breaks"... "spoilers" are all the panels, as raised on landing... and when they are used in a turn, they are referred to as "spoilerons"... the use of speedbreaks in flight is characterized also by a light buffetting, due to the sudden drag being incurred on the wing. It's quite noticeable, and there also tends to be, when you're sitting near the wing, and noise... that I really can't think of a word for, but those who know what I mean, can recognize it... but basically the sound of the wind going around those spoilers... I guess, in effect, the sound of a buffet... but it's audible... and is always associated with the deployment of the speed breaks... many aircraft though, like the 737 for example, are "slippery" in that it's not an easy plane to slow down and descend at the same time... speed breaks help to accomplish that... again, 737 pilots would perhaps be able to better characterize the flight characteristics of that plane... speed breaks also help with descending, when a quicker descent rate is necessitated... helps you descend without having to pitch the nose down as much, you can descend more flat...
XFSUgimpLB41X From United States of America, joined Aug 2000, 4300 posts, RR: 34
Reply 22, posted (14 years 9 months 1 day 5 hours ago) and read 2885 times:
The auto spoiler deployment during turbulence has to do with keeping the wing from getting over stressed in a load factor increase during one of the bumps... You can see them (actually the speed brakes if you wanna get technical) flapping up and down as the aircraft sinks and bumps around. My dad was an A320 pilot, and this is the best i remember his explaination. I shall ask him tommorrow to get a bit more detail...but it is not just to slow the plane down to manuevering speed.
Klaus From Germany, joined Jul 2001, 21652 posts, RR: 53
Reply 23, posted (14 years 9 months 23 hours ago) and read 2881 times:
Thank you both for your explanations.
I´m still wondering about the A320 system, though. If the system actively reacts to turbulence, it might try to "dampen" a sudden updraft by temporarily reducing the wing´s lift. But it would need to react very fast to do that. (This would at least help to take the "spike" out of the jerking movement of the wing.)
Is that conceivable or is it something else?
Deploying the spoilers asymmetrically would also induce a certain yaw impulse, wouldn´t it? When assisting in a turn, that might actually be a desired effect, or am I mistaken here?
Musang From United Kingdom, joined Apr 2001, 920 posts, RR: 6
Reply 24, posted (14 years 9 months 20 hours ago) and read 2872 times:
Ref. spoilers in turbulence, I believe Lockheed pioneered this concept for commercial jets with the series 500 TriStar, and the phrase "Gust Alleviation" springs to mind.
If the accelerometers (or IRS gyros??) detect a sudden upward lurch, an almost instantaneous spoiler deployment proportional to the intensity of the gust will counteract it.
On the subject of assymetric spoiler deployment, this does indeed cause a yaw, but its in the desired direction anyway. This would reduce the amount of rudder needed to co-ordinate the turn.
Traditionally, a turn would be initiated with aileron, but the most drag would occur at the downgoing aileron, i.e. the one opposite the direction of turn. So an aircraft rolling right would experience a yaw to the left, which the rudder is used to counteract. it is known as adverse yaw, familiar to private pilots from early in their training.
One way to reduce it is to design the aileron system so they operate differentially, i.e. the upward moving one always moves further than the downward one.
Roll an aircraft without roll spoilers smartly into a turn, and don't use the rudder, and it will often hold its heading or even yaw slightly opposite the direction of roll until it catches up with itself. Proper rudder input simultaneous with the aileron input cancels this out, and one of the functions of a Yaw Damper is to do this automatically.
Basic yaw dampers in GA aircraft work simply by a mechanical connection between the aileron and rudder. This would suit lazy or unco-ordinated pilots! Advanced systems detect the roll (via the IRS) and/or aileron input, and feed rudder in accordingly.
Regards - Musang
25 Max Power
: I must agree with Delta Flyer and JG about this forum. There is a lot of incorrect information on this post. Most of this stuff belongs in some genera
: Thank you. That´s the kind of information I was looking for! Good to see I wasn´t all that far off - this time.