F104- Boundary Layer Control

[Scet]

When flaps are in the land position and boundary layer control is active, is
there an increase in EGT that is sufficient to register on the cockpit
gauge?
If so, does the pilot look for the EGT rise to ensure the system is working?
If not, is there an indication that the system is inoperative, is the
aircrafts handling characteristics on approach indicative of system failure,
or is it fail safe?

Scet

[Dudley Henriques]

Hi Scet;
I just noticed this post in passing. I'm sure Walt will comment from a
first hand point of view, and the zip was one I missed in my "garage" of
fighters I've flown.
I'll take a shot at what you want and see how close it gets to being
right anyway! :-)
If I remember right, the BLC on the zip was actuated by a valve directly
linked to the flap extension system. The EGT should be a function of the
power percentage and nozzle position. I believe the EGT should be
somewhere below 560 degrees on final with the BLC operative with flaps
over 15 degrees. I don't remember what the visual indication was if any
for the zipper to confirm BLC operation, but if memory serves, 82 to 85%
rings a bell as a minimum on final to avoid uncommanded roll and sink.
Keep in mind; I didn't fly this bird and am going on recall from hashing
with some friends who did. Walt will have better answers for you I'm
sure.
Hope this helps a bit anyway.
Dudley Henriques
International Fighter Pilots Fellowship
Commercial Pilot/ CFI Retired

For personal email, please
replace the at with what goes there and
take out the Z's please!
dhenriquesZatZearthZlinkZdotZnet
"Scet" > wrote in message
...
> When flaps are in the land position and boundary layer control is
active, is
> there an increase in EGT that is sufficient to register on the cockpit
> gauge?
> If so, does the pilot look for the EGT rise to ensure the system is
working?
> If not, is there an indication that the system is inoperative, is the
> aircrafts handling characteristics on approach indicative of system
failure,
> or is it fail safe?
>
> Scet
>
>

[Scet]

Hi Dudley,
My train of thought was that EGT should be relatively stable the moment
flaps to land was selected. If EGT was say 530 degrees and flaps were
selected to land, the valve linked to the flap system would open, removing
air from the compressor/diffuser. A portion of this air is also used to cool
the turbine, so removing it should cause an EGT rise. Is it this rise in EGT
that is looked for to ensure the system is operative? Is there a thermal
switch that is made to indicate the system is or isn't working or is the
first inkling that the pilot has that all is not as it should be, aircraft
controllability issues during the approach phase?
Did the 105 or F4 have BLC and if so what indications did they give the
pilot?
It would be good to hear from Walt or maybe even Ed Rasimus may know?
Thanks for your input Dudley....and thanks to you and John Ward in regards
to the 51....I can't wait.

Scet

"Dudley Henriques" > wrote in message
hlink.net...
> Hi Scet;
> I just noticed this post in passing. I'm sure Walt will comment from a
> first hand point of view, and the zip was one I missed in my "garage" of
> fighters I've flown.
> I'll take a shot at what you want and see how close it gets to being
> right anyway! :-)
> If I remember right, the BLC on the zip was actuated by a valve directly
> linked to the flap extension system. The EGT should be a function of the
> power percentage and nozzle position. I believe the EGT should be
> somewhere below 560 degrees on final with the BLC operative with flaps
> over 15 degrees. I don't remember what the visual indication was if any
> for the zipper to confirm BLC operation, but if memory serves, 82 to 85%
> rings a bell as a minimum on final to avoid uncommanded roll and sink.
> Keep in mind; I didn't fly this bird and am going on recall from hashing
> with some friends who did. Walt will have better answers for you I'm
> sure.
> Hope this helps a bit anyway.
> Dudley Henriques
> International Fighter Pilots Fellowship
> Commercial Pilot/ CFI Retired
>
> For personal email, please
> replace the at with what goes there and
> take out the Z's please!
> dhenriquesZatZearthZlinkZdotZnet
> "Scet" > wrote in message
> ...
> > When flaps are in the land position and boundary layer control is
> active, is
> > there an increase in EGT that is sufficient to register on the cockpit
> > gauge?
> > If so, does the pilot look for the EGT rise to ensure the system is
> working?
> > If not, is there an indication that the system is inoperative, is the
> > aircrafts handling characteristics on approach indicative of system
> failure,
> > or is it fail safe?
> >
> > Scet
> >
> >
>
>

[Peter Bjoern]

On Thu, 26 Aug 2004 21:10:39 +0930, "Scet" > wrote
in rec.aviation.military:

>Is it this rise in EGT that is looked for to ensure the system is operative?
>Is there a thermal switch that is made to indicate the system is or isn't
>working or is the first inkling that the pilot has that all is not as it should be, aircraft
>controllability issues during the approach phase?

Hi Scet

I don't believe there was any variations in the EGT used to verify if the BLC
system is working or not, but I will try to verify this with a friend who used
to fly the 104 and see if he can remember.

In the meantime, this is what the T.O. 1F-104G-1 has to say about a BLC
malfunction :

"If a boundary layer control system malfunction is experienced as manifested
by a strong rolling tendency as the wing flaps travel to the LAND position,
proceed as follows :
1. Flaps-TAKEOFF.
2. Throttle-Adjust to minimum safe setting to reduce the effect of asymmetric
BLC while flaps are returning to TAKEOFF.
3. Fly final approach at not less than 195 KIAS with flaps in TAKEOFF position.
4. Touch down at 165 KIAS minimum."

Regards

Peter

[Dudley Henriques]

"Scet" > wrote in message
...
> Hi Dudley,
> My train of thought was that EGT should be relatively stable the
moment
> flaps to land was selected. If EGT was say 530 degrees and flaps were
> selected to land, the valve linked to the flap system would open,
removing
> air from the compressor/diffuser. A portion of this air is also used
to cool
> the turbine, so removing it should cause an EGT rise. Is it this rise
in EGT
> that is looked for to ensure the system is operative?

Makes sense, but I'll be surprised if Walt or Ed verify that looking for
an EGT rise on final in a 104 would be the indication for BLC operation.
It's more likely a bulb indicator if anything I would imagine, but I
could be wrong. I'm guessing you get blown flaps over 15 degrees as an
automatic function of the direct linkage to the flap system. I do know
this however. The zip guys have told me they knew pretty fast if it was
working if they at any time powered back below 80% :-))
Hope Walt and Ed take this up for you.

Take care,
D

[Ed Rasimus]

On Thu, 26 Aug 2004 21:10:39 +0930, "Scet"
> wrote:


>Did the 105 or F4 have BLC and if so what indications did they give the
>pilot?
>It would be good to hear from Walt or maybe even Ed Rasimus may know?
>Thanks for your input Dudley....and thanks to you and John Ward in regards
>to the 51....I can't wait.
>
>Scet

The F-105 did not have BLC. The F-4 did, prior to the soft wing, for
both leading and trailing edge flaps. I don't recall any landing check
of engine indication for BLC proper operation. The BLC was checked by
the crewchief during preflight when flaps were lowered by his simply
running a hand along the area to feel the blowing. There was a warning
circuit for BLC duct pressure that illuminated a caution light on the
telelight panel in the event of a line rupture. That was very serious
emergency as the superheated air would quickly lead to structural
damage to the wing.

In later years some portion of the BLC was eliminated, but I don't
recall which parts. Maybe someone with some soft-wing experience can
recall.


Ed Rasimus
Fighter Pilot (USAF-Ret)
"When Thunder Rolled"
"Phantom Flights, Bangkok Nights"
Both from Smithsonian Books
***www.thunderchief.org

[Steve Mellenthin]

>The F-105 did not have BLC. The F-4 did, prior to the soft wing, for
>both leading and trailing edge flaps. I don't recall any landing check
>of engine indication for BLC proper operation. The BLC was checked by
>the crewchief during preflight when flaps were lowered by his simply
>running a hand along the area to feel the blowing. There was a warning
>circuit for BLC duct pressure that illuminated a caution light on the
>telelight panel in the event of a line rupture. That was very serious
>emergency as the superheated air would quickly lead to structural
>damage to the wing.
>
>In later years some portion of the BLC was eliminated, but I don't
>recall which parts. Maybe someone with some soft-wing experience can
>recall.
>
>
>Ed Rasimus

The BLC on the F-4 drew air from the 13th stage compressor. I seem to recall
from my days as a propulsion engineer that the EGT rise for the BLC valve open
was no more than 15 degrees. The valve istelf was connected to the flap
linkage When the flaps were lowered, a rod connected to flap structure pulled
the BLC valve open. The circuitry that Ed refers to was on that linkage iself.
When the flaps were down and the wheels were up the "Wheels" light flashed
theoretically telling you to put your wheels down if you were going to fly with
flaps down. If you had both wheels and flaps up, that supposedly meant you had
a BLC valve stuck open and the possibility that Ed refered to, hot air being
pumped to the flaps, existed and you needed to get the plane on the gropund
ASAP as serious damage to things like hydraulic lines and electrcal connections
would happen soon.

I saw one F-4D that had an actual BLC failure. The leading edge was seriously
warped and the crew was luck to get the plane on the ground.

Most of the time the "Flashing Wheels Light" was a switch problem and was a
real maintenance problem and a high manhour driver not to mention a strain on
the runway rescue crews.

The BLC system was eventually capped off at the valve port on the engine and
the planes flew without it. Made landinf speeds 10-15 knots higher, no big
deal in the F-4.

In the early days of the F-4 in Europe, the F-4s sometimes refueled from AFR
recip/jet KC-97 aircraft at 220 kts or so and half flaps. Never had the
opportunity to do but that flasing lights in the cockpit would have driven me
nuts.

Steve

[Scet]

"Steve Mellenthin" > wrote in message
...
> >The F-105 did not have BLC. The F-4 did, prior to the soft wing, for
> >both leading and trailing edge flaps. I don't recall any landing check
> >of engine indication for BLC proper operation. The BLC was checked by
> >the crewchief during preflight when flaps were lowered by his simply
> >running a hand along the area to feel the blowing. There was a warning
> >circuit for BLC duct pressure that illuminated a caution light on the
> >telelight panel in the event of a line rupture. That was very serious
> >emergency as the superheated air would quickly lead to structural
> >damage to the wing.
> >
> >In later years some portion of the BLC was eliminated, but I don't
> >recall which parts. Maybe someone with some soft-wing experience can
> >recall.
> >
> >
> >Ed Rasimus
>
> The BLC on the F-4 drew air from the 13th stage compressor. I seem to
recall
> from my days as a propulsion engineer that the EGT rise for the BLC valve
open
> was no more than 15 degrees. The valve istelf was connected to the flap
> linkage When the flaps were lowered, a rod connected to flap structure
pulled
> the BLC valve open. The circuitry that Ed refers to was on that linkage
iself.
> When the flaps were down and the wheels were up the "Wheels" light
flashed
> theoretically telling you to put your wheels down if you were going to fly
with
> flaps down. If you had both wheels and flaps up, that supposedly meant
you had
> a BLC valve stuck open and the possibility that Ed refered to, hot air
being
> pumped to the flaps, existed and you needed to get the plane on the
gropund
> ASAP as serious damage to things like hydraulic lines and electrcal
connections
> would happen soon.
>
> I saw one F-4D that had an actual BLC failure. The leading edge was
seriously
> warped and the crew was luck to get the plane on the ground.
>
> Most of the time the "Flashing Wheels Light" was a switch problem and was
a
> real maintenance problem and a high manhour driver not to mention a strain
on
> the runway rescue crews.
>
> The BLC system was eventually capped off at the valve port on the engine
and
> the planes flew without it. Made landinf speeds 10-15 knots higher, no
big
> deal in the F-4.
>
> In the early days of the F-4 in Europe, the F-4s sometimes refueled from
AFR
> recip/jet KC-97 aircraft at 220 kts or so and half flaps. Never had the
> opportunity to do but that flasing lights in the cockpit would have driven
me
> nuts.
>
> Steve

Excellent and informative answers guys, couldn't ask for more.

Thanks.

Scet