Please explain spoiler terms

[Flamin_Squirrel 71]

Sorry, squirrel, but weight isn't affect by pitch or angle of attack. Weight is gravity.

If you pitch up/down from straight and level your trust/drag vector will have a component acting vertically, at which point weight, lift drag and thrust will all have an effect on eachother.

[MorsAbAlto 19]

I think in the analogy about an increase in drag resulting in a backwards momentum, the decrease in speed will decrease the airflow over an aircraft's airfoils and decrease lift. Effectively, that drag manages to slow down the aircraft and kill lift.

Precisely! The decrease in lift is caused by the decrease in speed (and thus airflow), not the increase of drag. These are two different things. If you counteract the increased drag by adding more thrust, nothing happens. Please note that I am refering to the aircraft as a whole and not just the airfoil, where drag will affect lift at a given speed (L/D ratio).

A decrease in lift (due to spoilers) will be counteracted by the pilot/autoflight system by increasing angle of attack. This increases induced drag. You shouldn't really analyse thrust/drag alone, as all forces acting upon the aircraft are relevant.

I don't. They are still four distinct forces that affect the aircraft in different ways. Still, the opposite of drag is thrust.

It is far easier to consider the aircraft's state by its energy state..

Yes, it is easier because it a more generalized approach, that does not factor in aerodynamic effects on the aircraft much. It's more relevant in military aviation, where you see all kinds of funny maneuvers away from the horizontal attitude and where energy conservation is important. Since you will normally not see acceleration significantly exceeding 1g on an airliner or bank angles in excess of 45 degrees, I feel it does not matter much in civil aviation.

If you pitch up/down from straight and level your trust/drag vector will have a component acting vertically, at which point weight, lift drag and thrust will all have an effect on eachother.

Yes, but unless the lateral acceleration is exceeding 1g, weight will only work in the vertical, from what I understand. I do not understand, how it would slow down the aircraft.It would be nice if a rated pilot could chime in to this discussion. By the way, what's your real name Squirrel? I always think of some sort of cartoon, when I read your nickname...

[danparker86 0]

Gents,This is a complicated issue and all points so far have relevance. As i understand it, as pointed out the four forces of the aircraft act together resulting in the actual state of the aircraft. An increased component of drag will require an increase in thrust to maintain a given airspeed, should thrust not be altered then the aircraft will slow and eventually increase the AOA. Lets remember that an aircraft needs two things to fly, AOA and RAF when these two hit the sweet spot the wing produces lift so yes the AOA does directly affect the weight in the sense it is required to produce lift to counteract the weight. once the critical AOA is reached the wing stalls and the aircraft will no longer produce lift, so drag has a relationship towards lift in that respect in the sense that the wing has reached the critical AOA. If you descend the AOA changes therefore not producing as much lift for a given weight component (assuming the airspeed has not changed), remembering that when we descend the weight component comes into play and less thrust is required to maintain a given airspeed if we add drag then we can maintain a faster rate of decent even with no thrust component applied because the aircraft can be pitched down and the weight can act as a force to replace thrust. Basically if you increase drag thrust must be applied to maintain straight and level flight, since we would not logically use speed brakes in straight and level flight being you could reduce thrust to slow the aircraft down anyway. You would logically only be using speed brakes in a decent which would therefore increase drag and if you are looking to slow the aircraft on its given decent path without altering power then speed brakes would assist that (because drag has been increased). That being said we can also reduce thrust and apply drag (speed brakes) which would give a much steeper decent path being that lowering the pitch attitude will increase the effect weight has on the aircraft in the sense AOA is reduced, therefore lift is reduced (given the airspeed remains constant) therefore as the nose lowers more and more, the lift component lowers due to AOA and the weight then plays its part.I am a rated pilot however im not sure if what i said needs any clarification but im more then happy to elaborate on any part of it, My apologies if its come out scrambled! (its getting late!) Fly safe Captains-Dan Parker

[Flamin_Squirrel 71]

Yes, but unless the lateral acceleration is exceeding 1g, weight will only work in the vertical, from what I understand. I do not understand, how it would slow down the aircraft.It would be nice if a rated pilot could chime in to this discussion. By the way, what's your real name Squirrel? I always think of some sort of cartoon, when I read your nickname...

Lateral? That's side to side, and doesn't apply to this discussion.And you don't have to be accelerating for weight to affect the lift/drag couple. See image below.My names Jordan, and I'm a private pilot if that counts.

[jcmontagne 1]

Sounds like the stuff we learn for the PPL isn't that evident after all...

[WestAir 2,522]

Sounds like the stuff we learn for the PPL isn't that evident after all...

The funny part is that several of us who replied have hundreds of flight hours, aeronautical degrees, and/or time in turbine-powered aircraft. :(

[StevenHPerry 20]

Looks like the frame of reference is what has us all on different pages.I like to think that my football teams is moving the ball down the field for a touchdown, rather than the football is just "being" while the field moves from right to left. Potatoe, potato.Let's get Dan Quayle's opinion.Steve Perry

[WestAir 2,522]

Let's get Dan Quayle's opinion.Steve Perry

Steve,"Verbosity leads to unclear, inarticulate things." - Dan Quayle. :( . You hit the nail on the head, though.

[MorsAbAlto 19]

Lateral? That's side to side, and doesn't apply to this discussion.And you don't have to be accelerating for weight to affect the lift/drag couple. See image below.My names Jordan, and I'm a private pilot if that counts.

Hey Jordan.as you can tell I am not a native speaker, so a wrong expression might slip in here and there. Sorry for that. I guess what I meant was the vertical axis. Okay, so after staring at the diagram for 10 minutes I can see your point. In fact I had a very similar image in my mind. It seems I was right about weight only acting downwards (in an absolute sense). But somehow I had a hard time to realize how this affects the thrust/drag axis when the pitch changes. Actually it makes a lot of sense now. So, thanks for clearing that up.

[Big_Les 1]

Spoilers "spoil" laminar airflow over lift generating devices. They may/will also create dragAir brakes or speed brakes do not spoil flow over LIFT generating devices but only create drag

[Rickie Welsh 27]

Hi, all these posts sound like a bunch of Philadelphia Lawyers having an argument as to whether the accused is guilty or not. I wonder who is right. richard welsh.

[Jefferson 3]

Funny discussion, indeed.But guys, we should note that there's a Terminology issue here, aswell. "Speed Brakes", "Spoilers" and "Ground Spoilers" are concepts handled by each manufacturer in different ways, but, in overall they all use the same. But, like one said earlier on this thread, The Spoiler will 'spoil' the laminar flow over the airfoil, it 'breaks' the Lift Coefficient of the wing. The speed brake changes the airflow, similar to a barrier, creating drag to reduce speed.The first also adds drag and the later also kills lift.Now the terminology issue. I fly gliders, and they're equipped with a pair of spoilers on each wing, and it serves for both purposes, adding drag and killing lift. it's not called speed brake, just spoiler, and it's effect (speed or lift) is controlled solely by how much of it is deployed. But also, there are other examples, like the F-100. Fokker equipped that aircraft with a tail-mounted speed brake. And so, It's there only for speed reduction, it doesn't affect the aircraft's lift in any way. And on it's wings, there are ground spoilers, called by fokker as Lift-Dumpers.And about the OP question, Boeing adopts "Down Detent" (Full stowed), "Armed" (Ground and Flight Spoilers armed for deployment, triggered when the main right landing gear strut is compressed on landing, or during an RTO), "Flight Detent" (In-flight max deployment of the speed brakes) and "Up" (Fully deployed).I'm almost "sure" the flight detent has a mechanic lock to avoid deployment beyond that limit in-flight.Hope it helps!Terminology, guys... It can be a pain, sometimes :)