IMHO Rainboe's position on use / misuse of speedbrakes is spot-on.
They are (in my company) used far far too often, and usually unnecessarily/incorrectly. Many pilots use them on every sector, sometimes several times. This is far too often if proper descent planning and judgement are used.
As RB said, use of speedbrake in intermediate descent where a level sector is to follow is usually a sign of incorrect entry point for that descent, and a slight speed adjustment will often sort that out without shaking the airframe and scaring some of the pax with the vibration. It is a much kinder and smoother way to achieve the same thing, but no, most just dive for the mistake handle. Use of speedbrake followed by an increase in power is, as RB said, often a very questionable procedure.
Pavlovian use of sb whenever the indicator says above profile is another common fault. It happens on a daily basis and is almost always unnecessary, and avoidable by a bit of thought of what lies ahead.
They are sometimes used like brakes on a car for speed reductions in level flight! (followed by a power increase, of course...) This is all just evidence of poor planning and awareness.
On the 737 it is virtually useless below 250Kts anyway, and Mr Boeing recommends it is NOT USED in conjunction with flaps. So why use a control that won't help you, that compromises controlability, that stresses the airframe and pax and that the manufacturer recommends you don't use in this scenario when you can put the wheels down a few seconds earlier than usual? "Non standard, gear down" solves the problem, unless you are so stuck in your SOPs that you just can't fly the aeroplane...It also has the advantage that it works, because if significantly high at this stage the sb's extra 200fpm won't help you anyway, and the minute or so it will take to become obvious just brings the aircraft ever higher and closer in, requiring ever more drastic action to correct.
There are many ways to skin a cat, as there are many ways to get an aeroplane to descend faster. Some are neater, more comfortable and more Proessional than others. You don't have to use the sb every time.
A bit of thought would prevent 75% of use of speedbrakes. IMHO, of course!
And finally, if you must use them, for God's sake use them smoothly and gently. They can cause the most sickening lurches when handled clumsily - which happens all too often, sadly. But then all too often pilots seem blissfully unaware that there are pax behind them who are very aware of jerky, uncomfortable flying.
(Same goes for wheel braking, but that is another topic entirely)
Last edited by Agaricus bisporus; 27th Jul 2008 at 11:50.