Throttle for speed, or stick for speed?
Avoid imitations
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Did a bit of gliding myself, nearly 35 years ago now, and I'm sure they were called spoilers back then. Having done a web search on the subject, I found about an equal number of references to "spoilers" on glider wings.
So we ought at all costs avoid perpetuating misnomers.
I'll just maintain my stance that airbrakes slow the aircraft down, spoilers spoil lift. RAF CFS told me so and they've seemed to do all right so far.
So we ought at all costs avoid perpetuating misnomers.
I'll just maintain my stance that airbrakes slow the aircraft down, spoilers spoil lift. RAF CFS told me so and they've seemed to do all right so far.
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Regardless of the correctness of the nomenclature, the two gliding clubs where I learned to fly in the 80s both referred to the items that popped out of the wing as "air brakes."
Looking back at an ancient document, it discusses the use of "half airbrake" on final approach.
Looking back at an ancient document, it discusses the use of "half airbrake" on final approach.
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I currently fly the Vigilant motorglider for the Air Cadets and we most definately refer to Airbrakes - never spoilers. The key thing to understand with them is not only the effect they have, but how we actually use them (I agree with previous posts that effect of a control can't always have a generic answer - it depends how you employ it/what are the other factors).
For example, we teach effect of airbrake initially - which is an increased rate of descent (non-linear as a/b is most effective through the 1st 1/3 of their range) and nose pitches down, hence increased speed (due to movement of centre of pressure) , put a/b in and effect reverses. We then teach the use of a/b, which is deploy a/b and control the pitch down with back stick to maintain the desired speed - so in effect we are using them to control rate of descent and not decrease speed. This is then employed to allow bloggs to control his rate of descent with regard to an aiming point on the approach, while maintaining a constant airspeed (which will inevitably alter by +/- 10kts as bloggs weaves his way down to somewhere on the airfield!!)
For example, we teach effect of airbrake initially - which is an increased rate of descent (non-linear as a/b is most effective through the 1st 1/3 of their range) and nose pitches down, hence increased speed (due to movement of centre of pressure) , put a/b in and effect reverses. We then teach the use of a/b, which is deploy a/b and control the pitch down with back stick to maintain the desired speed - so in effect we are using them to control rate of descent and not decrease speed. This is then employed to allow bloggs to control his rate of descent with regard to an aiming point on the approach, while maintaining a constant airspeed (which will inevitably alter by +/- 10kts as bloggs weaves his way down to somewhere on the airfield!!)
Avoid imitations
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Blagger,
From what you just described, pitching nose down is a secondary effect of control, not a primary effect. If you held a constant IAS, then what happens?
So "AIRBRAKES" ON = vertical SPEED INCREASED at the same IAS.
and "AIRBRAKES" OFF = vertical SPEED REDUCED at the same IAS.
That makes 'em technically (lift) spoilers / dump, not airbrakes!
When I was taught gliding, and it was by RAF instructors, I'm certain we were just taught to approach at a constant IAS but use WING SPOILERS where necessary to adjust the rate of descent to make the aiming point on the field, the opposite of power on a powered aircraft.
Well, if you're flying 'em now then I have to bow to your more recent currency regarding terminology, but it still doesn't seem logical to my old fashioned and simple brain to refer to them as airbrakes, when the primary effect is to reduce lift!
If I operate my car brakes the speed reduces, not increases. If I operate (real) airbrakes, either split ones at the rear of the fuselage like the Buccaneer or BAE146, or a single blade under the fuselage like the Hawk (no lift dump in either case) my aircraft slows down also. The reduction of lift comes as a function of reduced airspeed, not as a primary effect of use of the airbrake.
Did it all change when colour telly came in?
From what you just described, pitching nose down is a secondary effect of control, not a primary effect. If you held a constant IAS, then what happens?
So "AIRBRAKES" ON = vertical SPEED INCREASED at the same IAS.
and "AIRBRAKES" OFF = vertical SPEED REDUCED at the same IAS.
That makes 'em technically (lift) spoilers / dump, not airbrakes!
When I was taught gliding, and it was by RAF instructors, I'm certain we were just taught to approach at a constant IAS but use WING SPOILERS where necessary to adjust the rate of descent to make the aiming point on the field, the opposite of power on a powered aircraft.
Well, if you're flying 'em now then I have to bow to your more recent currency regarding terminology, but it still doesn't seem logical to my old fashioned and simple brain to refer to them as airbrakes, when the primary effect is to reduce lift!
If I operate my car brakes the speed reduces, not increases. If I operate (real) airbrakes, either split ones at the rear of the fuselage like the Buccaneer or BAE146, or a single blade under the fuselage like the Hawk (no lift dump in either case) my aircraft slows down also. The reduction of lift comes as a function of reduced airspeed, not as a primary effect of use of the airbrake.
Did it all change when colour telly came in?
Last edited by ShyTorque; 19th Feb 2005 at 17:28.
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I think another specific benefit of drag inducers (air brakes, et al) is that they move the drag curve up and left thus moving the min power and min drag points to a lower IAS. This, I assume, is a major benefit when on the approach as the IAS will more speed stable as a result (tend not to drop away so quickly).
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Shy Torque,
I know what you're saying - if you hold the attitude and deploy the airbrake/spoilers (!) you will see a decrease in speed, when we teach maintaining the desired speed (65kts on the approach) this will be at a new attitude with a/b out than before without.
As for the move in the drag curves, I got this question by a CAA examiner recently - he asked me why the BAe146 approaches with it's airbrakes out and this is the reason why!
As an aside, when I'm flying SEP I always use the throttle for speed technique from my 400ft reference point on approach - much easier to get the thing down on the numbers consistently than with any other method.
I know what you're saying - if you hold the attitude and deploy the airbrake/spoilers (!) you will see a decrease in speed, when we teach maintaining the desired speed (65kts on the approach) this will be at a new attitude with a/b out than before without.
As for the move in the drag curves, I got this question by a CAA examiner recently - he asked me why the BAe146 approaches with it's airbrakes out and this is the reason why!
As an aside, when I'm flying SEP I always use the throttle for speed technique from my 400ft reference point on approach - much easier to get the thing down on the numbers consistently than with any other method.
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Having only just picked up on this thread I'm utterly amazed how long it is! ... so I'll add my bit too
I hate to agree with SAS but his...
is the most sensible bit I've seen.
I came from gliding to power but haven't flown gliders for many years now. Most of my glider training transfered to the way I fly powered aircraft (rightly or wrongly?) and seems to have been OK for the simple SEP's that I have predominately flown. In gliders I was always taught attitude controls speed and rate of descent (taking lift and sink out) was controlled by airbrakes/spoilers. I quickly applied the same logic to power with throttle controlling ROD instead of airbrake ... it also has the added advantage of acting as my very own thermal to allow climb
So when I'm on the approach, if I'm high I pull airbrake/reduce power, and if I'm low I reduce airbrake/add power. Obviously all these controls have further effects which kind of simply takes the qustion marks away from the title of this subject! and reinforces SAS's above quote.
Of course in an engine failure, speed can't be controlled by throttle anyway you work it and so has to be controlled by stick! ROD can be finely controlled by sideslip if needs be, but is essentially controlled by the glide angle and sink rate of the aircraft.
There seems to be way too much analysis here ... Obi-Wan would have lost Luke's trust if he'd said "Consider all the ways you can use your power Luke, then in the given time frame select the most appropriate and apply in a carefully controlled manner". Nope, he preferred "Feel the force Luke"
SS
PS. Bound to be wrong, but in the gliding fraternity when I was active, we used to refer to top-only drag inducers as spoilers, and split top and bottom ones as airbrakes. Airbrakes and spoilers have one main difference to flaps in that they normally do not effect stall speed (but can effect stall attitude).
I hate to agree with SAS but his...
Getting bogged down in the semantics of point and power Vs. anything else is a waste of time, since there isn't really two different ways of doing it. Watch someone who knows what they are doing and they'll be manipulating the attitude and power at the same time without even thinking about it.
I came from gliding to power but haven't flown gliders for many years now. Most of my glider training transfered to the way I fly powered aircraft (rightly or wrongly?) and seems to have been OK for the simple SEP's that I have predominately flown. In gliders I was always taught attitude controls speed and rate of descent (taking lift and sink out) was controlled by airbrakes/spoilers. I quickly applied the same logic to power with throttle controlling ROD instead of airbrake ... it also has the added advantage of acting as my very own thermal to allow climb
So when I'm on the approach, if I'm high I pull airbrake/reduce power, and if I'm low I reduce airbrake/add power. Obviously all these controls have further effects which kind of simply takes the qustion marks away from the title of this subject! and reinforces SAS's above quote.Of course in an engine failure, speed can't be controlled by throttle anyway you work it and so has to be controlled by stick! ROD can be finely controlled by sideslip if needs be, but is essentially controlled by the glide angle and sink rate of the aircraft.
There seems to be way too much analysis here ... Obi-Wan would have lost Luke's trust if he'd said "Consider all the ways you can use your power Luke, then in the given time frame select the most appropriate and apply in a carefully controlled manner". Nope, he preferred "Feel the force Luke"
SS
PS. Bound to be wrong, but in the gliding fraternity when I was active, we used to refer to top-only drag inducers as spoilers, and split top and bottom ones as airbrakes. Airbrakes and spoilers have one main difference to flaps in that they normally do not effect stall speed (but can effect stall attitude).
