Spoilers, no spoilers?

An Air Canada DC-8 crashed in 1970 because spoilers were deployed
before landing, which "by the book" is a definite no-no (cf. Air
Canada 621 disaster). How come the first officer (with over 5500 hrs
with that type of aircraft) made such a decision to deploy spoilers
while still in the air? What else, when full flaps and idle power
aren't enough, can a pilot use to handle a too high/too fast final
approach if not deploy spoilers?

As a side question, what is the functional difference between spoilers
and airbrakes?

Hi,

In article ,
wrote:
As a side question, what is the functional difference between spoilers
and airbrakes?

Just read that section of the book for my PPL exam. I *think* that spoilers
can be used differentially for roll control, whereas speedbrakes both pop up
together so can't control roll.

But I'm probably wrong

Andy

"Andy Hawkins" wrote in message
...
Hi,


Just read that section of the book for my PPL exam. I *think* that
spoilers
can be used differentially for roll control, whereas speedbrakes both pop
up
together so can't control roll.

But I'm probably wrong


Andy,

Spoilers deploy together symmetrically. What you are thinking of are
Spoilerons. Spoilerons come into play at slower speeds (typically when the
flaps are deployed beyond a certain point) to improve roll control at slower
airspeeds. Instead of the spoiler panels coming up symmetrically on both
wings to kill lift, only the panel on the wing with the "up" aileron will
deploy. Next time you are in an airliner watch the aileron/spoileron panels
work together at slower speeds. When the aileron moves up the corresponding
spoileron panel will move with it.

Mish

deploy. Next time you are in an airliner watch the aileron/spoileron panels
work together at slower speeds. When the aileron moves up the corresponding
spoileron panel will move with it.

Aren't spoilerons ailerons that can move UP together, killing lift?

Bartek

As a side question, what is the functional difference between spoilers
and airbrakes?

Spoilers reduce lift. Speed brakes create drag. ...and each might do a
little of both. Bob F.

Amine wrote:
An Air Canada DC-8 crashed in 1970 because spoilers were deployed
before landing, which "by the book" is a definite no-no (cf. Air
Canada 621 disaster). How come the first officer (with over 5500 hrs
with that type of aircraft) made such a decision to deploy spoilers
while still in the air? What else, when full flaps and idle power
aren't enough, can a pilot use to handle a too high/too fast final
approach if not deploy spoilers?

Go around.


--
Dudley Henriques

"Dudley Henriques" wrote in message ...
Amine wrote:
An Air Canada DC-8 crashed in 1970 because spoilers were deployed
before landing, which "by the book" is a definite no-no (cf. Air
Canada 621 disaster). How come the first officer (with over 5500 hrs
with that type of aircraft) made such a decision to deploy spoilers
while still in the air? What else, when full flaps and idle power
aren't enough, can a pilot use to handle a too high/too fast final
approach if not deploy spoilers?

Go around.


--
Dudley Henriques

My thought exactly!

On Feb 7, 3:35 pm, Dudley Henriques wrote:

Go around.


Well, let's play the devil's advocate... What if you can't go around?
(E.g. because of engine failure or in a glider). I mean, I understand
why you don't want to deploy spoilers if you're below minimums or if
you're flirting with stall speed. But if you're well above minimums,
with no risk of stalling, I don't see any reason why you shouldn't use
spoilers to bleed the extra momentum/altitude. The only disadvantage
would be that the final approach will be steeper and thereby would not
have the elegance of the perfect glide slope. But that's seems to be
more a matter of taste (and possibly performance) than an actual
safety issue.

After all, the "no-spoiler-in-midair"dogma isn't built in the design
of the pilot interface. If there truly was a physical reason why
spoilers should not come out in the air, it would have been an
engineering requirement to systematically disable their mechanism
unless, say, the gear is down and the wheels rolling.

On Feb 8, 6:57*am, Amine wrote:
Go around.

Well, let's play the devil's advocate... What if you can't go around?
(E.g. because of engine failure or in a glider). I mean, I understand
why you don't want to deploy spoilers if you're below minimums or if
you're flirting with stall speed. But if you're well above minimums,
with no risk of stalling, I don't see any reason why you shouldn't use
spoilers to bleed the extra momentum/altitude. The only disadvantage
would be that the final approach will be steeper and thereby would not
have the elegance of the perfect glide slope. But that's seems to be
more a matter of taste (and possibly performance) than an actual
safety issue.

This paragragh has several misconceptions as it relates to the OP.
First, An engine out missed in a DC8 or even a two engine jet is
doable and it is practiced all the time in the sim. Spoiler usage in
sailplanes is a completely different kettle of fish and it is normal
to use them into the touchdown in most ships. The crash discused in
the OP happened many years ago and it has been standard in the
industry as long as I can remember (I go back 20 years) to be on
glidpath, on speed, and fully configured with the landing checklist
complete by 1000 AGL (An exception to this is that in VMC you dont
have to be on speed but you must be slowing). No Ifs or Buts. The use
of spoilers below certain RAs and past certain flap settings is
prohibited in the Boeing products and you would be hard pressed to
find both a captain and fo who would ignore operating limitations. So
its not just a mater of taste.

. If there truly was a physical reason why
spoilers should not come out in the air, it would have been an
engineering requirement to systematically disable their mechanism
unless, say, the gear is down and the wheels rolling.

Actually, this is the way it works. Only some of the spoilers deploy
inflight (Either through the spoiler handle or the Aileron/Spoiler
mixer ). The rest of the spoilers will not deploy until the plane is
on the ground.
F Baum

On Fri, 8 Feb 2008 07:40:33 -0800 (PST), "F. Baum"
wrote:


. If there truly was a physical reason why
spoilers should not come out in the air, it would have been an
engineering requirement to systematically disable their mechanism
unless, say, the gear is down and the wheels rolling.

Actually, this is the way it works. Only some of the spoilers deploy
inflight (Either through the spoiler handle or the Aileron/Spoiler
mixer ). The rest of the spoilers will not deploy until the plane is
on the ground.

Or an airspeed lockout. If memory serves they won't deploy, even for
roll assistance, above a certain speed either. Don't they also
deflect at different angles depending on what system is activating
them? Highest angle off the wing is for full in-flight spoiler handle
(and some don't even come up for that), inboard segments deflect at a
greater angle than outboards for roll assistance (which is about 1/2
the angle off the wing compared to full spoiler), and everything comes
up at full for weight-on-wheels spoiler system?