airbrake question

In article ,
(WaltBJ) wrote:

However, some, like the 727, say
'no speed brake use with flaps extended' since loss of lift because of
turbulence behind the s/b results in aero center shifting aft
resulting in a marked nose-down reaction and loss of altitude. Not
good on approach.

Actually that is because a loss of hydraulics with both s/b and flaps
out leaves the s/b floating, still causing drag whereas if they were
down, they would stay down for the most part.

There is very little pitch change with 727 speedbrakes even if you only
deploy one set, ie the inboards only, or the outboards. So little that
you can't use them to offset unwanted pitch like you can on a 707 or 135.

--
Ron

"Ron Parsons" wrote in message
...
In article ,
(WaltBJ) wrote:

However, some, like the 727, say
'no speed brake use with flaps extended' since loss of lift because of
turbulence behind the s/b results in aero center shifting aft
resulting in a marked nose-down reaction and loss of altitude. Not
good on approach.

Actually that is because a loss of hydraulics with both s/b and flaps
out leaves the s/b floating, still causing drag whereas if they were
down, they would stay down for the most part.

There is very little pitch change with 727 speedbrakes even if you only
deploy one set, ie the inboards only, or the outboards. So little that
you can't use them to offset unwanted pitch like you can on a 707 or 135.

Which are, like any airliner, completely different from a fighter speed
brake.

"miso" wrote in message
om...
Thanks to both replies. I was thinking of the F15, so I thought it
might be the center of gravity. I'm going to see if I can find photos
of the other models mentioned.

Yes, a fighter speed brake is completely different from most of the replies
you got. A fighter has the speed brake on the fue forward of the tail and
it is only similar in name to a "spoiler deployed as a speedbrake".

When Hawker developed the Hunter, the prototype had the airbrakes
mounted in such a way that they could be moved forward and aft, to find
the place where they produced no pitch change. It turned out that the
first location tried was the best.

This is why the Hunter's airbrakes are mounted out of contour.

On Wed, 3 Dec 2003 08:39:19 -0800, "Tarver Engineering"
wrote:


"miso" wrote in message
. com...
Thanks to both replies. I was thinking of the F15, so I thought it
might be the center of gravity. I'm going to see if I can find photos
of the other models mentioned.

Yes, a fighter speed brake is completely different from most of the replies
you got. A fighter has the speed brake on the fue forward of the tail and
it is only similar in name to a "spoiler deployed as a speedbrake".

John, once again you illustrate the problem with usenet. "on the fue"?
"spoiler deployed as a speedbrake"?

Seriously, the 102 and 106 certainly didn't have it deployed "forward
of the tail" and those are the airplanes you were involved with in the
FAT ANG. The 105 didn't have it "forward of the tail" and the F-16
among current equippage doesn't have it "forward of the tail" either.

Some do. The F-15 certainly is forward and the F-111 was certainly
forward.

As for "spoiler deployed as a speedbrake"--that doesn't happen on any
fighter type that I've encountered. Certainly some tactical aircraft
used spoilers, primarily as a design counter to adverse yaw, but none
with spoilers have a choice of control surface or speed brake
function. Airliners do.

Tell me again about your fighter experience.

Speed brakes on fighters are single function surfaces.

"Ed Rasimus" wrote in message
...
On Wed, 3 Dec 2003 08:39:19 -0800, "Tarver Engineering"
wrote:


"miso" wrote in message
. com...
Thanks to both replies. I was thinking of the F15, so I thought it
might be the center of gravity. I'm going to see if I can find photos
of the other models mentioned.

Yes, a fighter speed brake is completely different from most of the
replies
you got. A fighter has the speed brake on the fue forward of the tail
and
it is only similar in name to a "spoiler deployed as a speedbrake".

John, once again you illustrate the problem with usenet. "on the fue"?
"spoiler deployed as a speedbrake"?

Seriously, the 102 and 106 certainly didn't have it deployed "forward
of the tail" and those are the airplanes you were involved with in the
FAT ANG. The 105 didn't have it "forward of the tail" and the F-16
among current equippage doesn't have it "forward of the tail" either.

Some do. The F-15 certainly is forward and the F-111 was certainly
forward.

As does the F-18.

As for "spoiler deployed as a speedbrake"--that doesn't happen on any
fighter type that I've encountered.

That does cause one to wonder why there was such a lengthly discussion of
airliner type speedbrakes.

Certainly some tactical aircraft
used spoilers, primarily as a design counter to adverse yaw, but none
with spoilers have a choice of control surface or speed brake
function. Airliners do.

The selection capability is however there for those tactical aircraft using
an actual "speed brake", as opposed to a "spoiler deployed as a speedbrake".

Tell me again about your fighter experience.

Speed brakes on fighters are single function surfaces.

Exactly as I wrote, but thanks for playing.

From: Ed Rasimus

On Wed, 3 Dec 2003 08:39:19 -0800, "Tarver Engineering"
wrote:


"miso" wrote in message
.com...
Thanks to both replies. I was thinking of the F15, so I thought it
might be the center of gravity. I'm going to see if I can find photos
of the other models mentioned.

Yes, a fighter speed brake is completely different from most of the replies
you got. A fighter has the speed brake on the fue forward of the tail and
it is only similar in name to a "spoiler deployed as a speedbrake".

John, once again you illustrate the problem with usenet. "on the fue"?
"spoiler deployed as a speedbrake"?

Seriously, the 102 and 106 certainly didn't have it deployed "forward
of the tail" and those are the airplanes you were involved with in the
FAT ANG. The 105 didn't have it "forward of the tail" and the F-16
among current equippage doesn't have it "forward of the tail" either.

Some do. The F-15 certainly is forward and the F-111 was certainly
forward.

As for "spoiler deployed as a speedbrake"--that doesn't happen on any
fighter type that I've encountered. Certainly some tactical aircraft
used spoilers, primarily as a design counter to adverse yaw, but none
with spoilers have a choice of control surface or speed brake
function. Airliners do.

Tell me again about your fighter experience.

Speed brakes on fighters are single function surfaces.

The term "fue" was to prove he's in the right clique I guess.

As for his fighter experience he was a engine mechanic on F-106s which, with
his EE degree, makes him an expert on everything aerospace, automotive etc as
he is fond of saying in several newsgroups.

Dan, U.S. Air Force, retired

In article ,
David Lednicer writes:

When Hawker developed the Hunter, the prototype had the airbrakes
mounted in such a way that they could be moved forward and aft, to find
the place where they produced no pitch change. It turned out that the
first location tried was the best.

This is why the Hunter's airbrakes are mounted out of contour.

It's a little more complicated than that. Originally, the Hunter was
going to use its flaps as speedbrakes. This cased a lot more pitching
moment than the specifications, or, more importantly, the Ministry of
Supply (I _think_ it was Ministry of Supply it might have still been
the Air Ministry) would tolerate. The Logical Move would have been to
restring the rear fuselage for Sabre/F-84F type lateral brakes, but
for some reason, this was deemed to hold up production too
much. (Although one was prototyped, so _somebody_ did the drawings and
bent the metal). The Last Best Desparate Move was the brake scabbed
on under the aft fuselage. As you say, they got the position right
the first time they tried it, But that position has some
disadvantages. It's vulnerable to damage from stuff like ejected
ammunition links, and you can't have the brake open when landing.

A pity, really. The Hunter is just about the perfect shape. If you
can lose the speedbrake under the tail, and the "Sabrina fairings"
tacked under the gun bay to hold the spent links, so that they didn't
damage the speedbrake.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster