leading edge flaps

Slats are typically UN-powered devices on the leading edge that extend
simply by the reduced dynamic pressure against them as airspeed slows.
Example would be the leading edge extensions of the F-86 and F-100.

I wouldn't agree with "typically." Aero slats also extend when a certain
AOA is achieved ... the A-4 slats would extend at approximately 12 units AOA
(IIRC) and bringing them out symmetrically at higher airspeeds was not a
sure thing.

Grumman liked powered slats. Both the A-6 and F-14 had them.

R / John

"John Carrier" wrote in message
...
Slats are typically UN-powered devices on the leading edge that extend
simply by the reduced dynamic pressure against them as airspeed slows.
Example would be the leading edge extensions of the F-86 and F-100.

I wouldn't agree with "typically." Aero slats also extend when a certain
AOA is achieved ... the A-4 slats would extend at approximately 12 units
AOA
(IIRC) and bringing them out symmetrically at higher airspeeds was not a
sure thing.

The Blues bolted 'um shut. Can you imagine what would happen in a tight
diamond with an A4 if a wing position got an asymmetrical slat extension
with roll induced....say in a barrel roll? Not a pretty thought!! :-))
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt

The F-4C, D and hardwing E had leading edge flaps, the E (post 556) and
subsequent models F,G, S had powered slats. The Thunderbirds used hardwing
E-models, probably for the reasons you stated. Also had no radar and added
VHF radios, but we weren't talking about that.

I once had an asymmetric leading edge flap extension in a C model. Rolled
inverted faster than I ever had. Pilot was cool and unloaded and used a
whole bunch of rudder to regain control.

--
Les
F-4C(WW),D,E,G(WW)/AC-130A/MC-130E EWO (ret)


"Dudley Henriques" wrote in message
k.net...


The Blues bolted 'um shut. Can you imagine what would happen in a tight
diamond with an A4 if a wing position got an asymmetrical slat extension
with roll induced....say in a barrel roll? Not a pretty thought!! :-))
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired
For personal email, please replace
the z's with e's.
dhenriquesATzarthlinkDOTnzt

The Blues bolted 'um shut. Can you imagine what would happen in a tight
diamond with an A4 if a wing position got an asymmetrical slat extension
with roll induced....say in a barrel roll? Not a pretty thought!! :-))

Also bolted shut when the A-4E/F (AKA Mongoose) was used as adversary for
F-8 and F-4. Then unbolted when the Turkey showed the necessity of better
slow speed capability.

John X

"Dudley Henriques" wrote...

The Blues bolted 'um shut. Can you imagine what would happen in a tight
diamond with an A4 if a wing position got an asymmetrical slat extension
with roll induced....say in a barrel roll? Not a pretty thought!! :-))

In over 1700 A-4 hours, I never had an asymmetric slat extension that I could
not quickly and easily control. After about 1000 hours, few of them were even
unpredictable... Careful preflight of the slats would give a VERY good idea of
which one would come out first, and any preflight "stickiness" was grounds for
rejecting the airplane or having the Airframers work on it before flight. I
believe too many TA-4s were lost in the Training Command due to students'
unfamiliarity with the airplane and instructors' failure to teach and emphasize
both preflight and recovery techniques.

That said, I fully understand why the Blues bolted them in -- their 36"
wingtip-to-fuselage clearance in some of their formation maneuvers gave quite a
bit less room for error than our nominal 3-5' wingtip-to-wingtip clearance in
the fleet.

On Sun, 11 Jan 2004 20:14:26 GMT, "John R Weiss"
wrote:

"Dudley Henriques" wrote...

The Blues bolted 'um shut. Can you imagine what would happen in a tight
diamond with an A4 if a wing position got an asymmetrical slat extension
with roll induced....say in a barrel roll? Not a pretty thought!! :-))

In over 1700 A-4 hours, I never had an asymmetric slat extension that I could
not quickly and easily control. After about 1000 hours, few of them were even
unpredictable...

I wonder if you could try to describe, as well as you can recall, what
exactly happens during an asymmetrical slat extension?

The reason I am asking such an obvious sounding question is that we
recently had a discussion concerning asymmetric slat extension of a
BF-109 in a Finnish newsgroup. While the immediate lay-man's reaction
is that the aircraft would, of course, violently roll away from the
extended slat (=extended slat up), because of the increased lift by
the slat, the situation becomes less obvious the more I think about
it.

Theoretically, from the textbook figure illustrating the effect of
trailing edge flaps and leading edge slats, one could argue that
nothing happens, since slats (unlike flaps) do not increase Lift
Co-efficient (CL) on a given Angle of Attack (AOA) but only increase
the maximum attainable CL. This at least in the case that the net wing
area does not increase when slat extends.

If the wing area increases (as probably is the case with A-4, judging
from the photo I have) as the slat extends, the aircraft would tend to
roll extended slat up. Right?

However, if the geometry is such that the leading edge moves down as
the slat extends, one could argue that the AOA of the profile
decreases causing roll towards the extended slat.

Or, if the slat extension causes a change of pressure distribution
around the aileron (the aileron snatch reported by the British BF-109
test pilots ?) moving the ailerons (probably not on the hydraulic
irreversible(?) control system of the A-4) until the pilot corrects
it, the roll could be either way.

Mikko

On Sun, 11 Jan 2004 13:13:00 GMT, "Dudley Henriques"
wrote:

The Blues bolted 'um shut. Can you imagine what would happen in a tight
diamond with an A4 if a wing position got an asymmetrical slat extension
with roll induced....say in a barrel roll? Not a pretty thought!! :-))

Or you could ask Steve what happens when one F-18 slat popped up over
the stops and got stuck, perpendicular to the airflow. Not a pretty
sight at all.

Of course, the O'Hare DC-10 had a slat asymmetry, although that was an
asymmetric retraction of an extended slat. Subsequent simulator
studies showed that, even knowing the problem was asymmetric slats,
the airplane was too low to recover.

Mary

--
Mary Shafer Retired aerospace research engineer

On Mon, 12 Jan 2004 23:03:31 -0800, Mary Shafer
wrote:

Of course, the O'Hare DC-10 had a slat asymmetry, although that was an
asymmetric retraction of an extended slat. Subsequent simulator
studies showed that, even knowing the problem was asymmetric slats,
the airplane was too low to recover.

Mary

If we're talking about the same DC-10 that was lost at O'Hare about 20
years ago, the slat assymetry was caused by the engine and pylon
departing the wing, up and over and in the process taking a chunk of
leading edge with it.

The accident investigation and subsequent simulator trials
demonstrated fairly conclusively that the aircraft was recoverable,
however training to immediately pull up and reduce speed to Vmc was
incorrect. What was needed was the more high performance airplane
practice of "unload for control" in which you (counter-intuitively)
ease off the back pressure possibly all the way to zero G and let
airspeed build to a point where more G is available for the recovery.


Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
Smithsonian Institution Press
ISBN #1-58834-103-8

On Sun, 11 Jan 2004 06:05:28 -0600, "John Carrier"
wrote:

Slats are typically UN-powered devices on the leading edge that extend
simply by the reduced dynamic pressure against them as airspeed slows.
Example would be the leading edge extensions of the F-86 and F-100.

I wouldn't agree with "typically." Aero slats also extend when a certain
AOA is achieved ... the A-4 slats would extend at approximately 12 units AOA
(IIRC) and bringing them out symmetrically at higher airspeeds was not a
sure thing.

"How many angels (angles?) can dance on the head of a pin?" My use of
"typically" referred to the "un-powered", i.e. hydraulically or
electrically actuated/operated aspect. And, the examples (F-86 and
F-100) were aerodynamic, not mechanical. It, hopefully, recognized
that slats can be mechanically operated.

If they extend when airpressure is reduced as airspeed slows, then it
would be redundant to add "also when a certain AOA is achieved"
because that is the inevitable, inexorable, undeniable result of
slowing.

Gotta believe that the assymetric deployment even intermittently would
be exciting.

Really, the discussion of the wide range of wing-modifying devices
that have been employed over the years is amazing.



Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
Smithsonian Institution Press
ISBN #1-58834-103-8

If they extend when airpressure is reduced as airspeed slows, then it
would be redundant to add "also when a certain AOA is achieved"
because that is the inevitable, inexorable, undeniable result of
slowing.

I was thinking of maneuvering. The A-4 slat would extend up to around
350KIAS once the proper AOA was achieved ... hardly slow. I suspect the
various NA products behaved similarly.

R / John