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Su-27 intakes


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Hi gents,

I'm wondering what state would be the FOD guard in on a Su-27 while landing and taking off?

My impression is that the FOD guards may be raised to protect fodding the engine as the runway conditions are not alwyas perfect?

take off and landing ?

Or not at all and the FOD guards only are raised on the ground when the engine is off ? If so why do they use intake cover then ?

I'm about to close some Zactoman intakes and I would hate to make a use mistake :)

(at this time the FOD are raised) for a landing roll flanker ...

Comments & inputs most welcome

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I've gotten this wrong in the past so Flankerman correct me if I'm wrong!

Down = not in use, fan is visible.

Up = Guard in use, screens visible.

On the ground, engines off - Down, the fans are visible. They usually put intake covers on at this point.

On the ground, engines running - Up. Screens are there to protect the engines.

At takeoff - Weight on wheel switch automatically drops the guards.

At landing - ??? Do they go up when the gear are dropped? When the flaps are dropped? Or when the wheels touch down?

:cheers:

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I THINK it works like this........

If the engine is running and there is weight on the wheels, the FOD guard is up - i.e deployed.

On the ground, with the engine off, they are down flush with the bottom of the intake - i.e. not in use.

The same is true in the air.

I think they are governed by a weight-on-wheels servo - but I could be wrong.

On some of my ground-based Flanker models I have had one up and one down - on the basis that there MUST be a manual override for maintenance purposes!

Just waiting for someone to tell me I'm wrong........ :thumbsup:

Intake_05.jpg

Ken

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Thanks gents,

If it's WOW, then the question is the speed. Some Ac system coulpe the WOW swicth with speed.

in this case of a landing roll, with all braking systems deployed, the wing won't generate much lift and WOW should be ON, then remains the speed of the aircraft. I guess I found the exact tricky spot :salute:

I might even make then half deployed :angry:

that being said, are the bottom louvres an indicaton of the position of the FOD guard?

Do they come Open only when the guard is up? if so that's a good indication on the pictures, you can't see the guard generally, but you do see the bottom of the intakes.

Very interesting, thanks gents

Edited by Red Dog
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The bottom louvres are suction-relief doors.

They are spring-loaded and open on demand from the airflow - if you look at the underside of a Flanker in flight, they 'flutter' as they open and close.

Some are open, some not.

I have a photo somewhere of me pushing one of those slats open with my hand........

They are not connected to the FOD mesh screen.

Ken

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I was remembering wrong in terms how the guards are attached. I thought that they "dropped down" from top of intakes, instead of going up from bottom of intakes. So, to correct my statement "Up at take off and landing." :soapbox:

Here is a shot showing Su-27SMK with screens:

http://img51.imageshack.us/img51/6059/su27skforfra.jpg

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I was remembering wrong in terms how the guards are attached. I thought that they "dropped down" from top of intakes, instead of going up from bottom of intakes. So, to correct my statement "Up at take off and landing."

ok, I'm confused again.

On the ground, engines off - Down, the fans are visible. They usually put intake covers on at this point.

Agreed there

On the ground, engines running - Up. Screens are there to protect the engines.

ok, but that means WOW is true and thus as soon as the system is powered up, the FOD should raise to protect the engine. which conflicts with the following:

At takeoff - Weight on wheel switch automatically drops the guards.

so I gues it would be , when WOW goes false, (at liftoff) the guards lower down.

At landing - ??? Do they go up when the gear are dropped? When the flaps are dropped? Or when the wheels touch down?

I guess they's then go up again to prtect fodding the engines at WOW, with thus the wing developping no lift at all.

In any way, I'm screwed as I followed initial advise and glued them DOWN :wub:

while my initial impression was UP. (always follow first impression)

No turning back now anyway

They are not connected to the FOD mesh screen.

Thanks Flankerman

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My first impression is that mesh screens were attached at top of intakes, not on bottom as seen in Ken's picture.

So, when i was saying there were down, i thought they was going from top, downward to bottom of intakes, like on MiG-29. On Su-27 when they are turned on, they risen up, not other way around like on MiG-29. So, i meant all time that they are turned on during landing and take off (as long as engines are on), like seen on my picture.

The point with those screens is to protect engine. And most hazardous area for engines are on ground. So it is perfectly logical that they should be deployed during landing. :thumbsup:

Edited by Berkut
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Protective mesh in flight position is down (usual position - its covered moved springed down air intakes hatches). On photo, what posted Ken this mash manually up and fixed by wire.

On upper surface of intake also positioned three-parts moved aerodinamic surfaces (for control air pressure sprues on engine)

12.JPG

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Just to clarify....

The photos I took of the intake/mesh screen were on a rather forlorn looking T10-20 at Khodynka

I manually moved the mesh screen up and down - using the loop of string that was attached to it....

Here's the whole set of photos.....

The compressor face..

Intake_01.jpg

The whole intake - the mesh screen is lying 'down' at the bottom of the intake trunking - it is hinged at the rear edge..

Intake_02.jpg

The intake starting to lift - into the 'closed/deployed' position.....

Intake_03.jpg

The intake almost fully deployed...

Intake_04.jpg

Fully up - the structure at the bottom is the auxiliary blow-in doors...

Intake_05.jpg

Blow-in doors from the inside - the first two are open..

Intake_06.jpg

Blow-in doors from the outside - I have simply just pushed them open with my hand...

Intake_07.jpg

You can see the mesh screen (in the down position) through the blow-in doors....

Intake_08.jpg

Down the back end - the afterburner flame holder...

Intake_09.jpg

Ken

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Thank you Ken for the pictures; most appreciated.

Since the FOD guards lift up, if the aircraft still is at a certain speed, that mouvement needs to be very powerfull from the back pivot point as it has to fight against the airflow. Even if speed is rather slow, it still needs to be very powerful.

Speaking of FOD, there's one on the last picture :thumbsup:

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Hi gents,

I'm wondering what state would be the FOD guard in on a Su-27 while landing and taking off?

My impression is that the FOD guards may be raised to protect fodding the engine as the runway conditions are not alwyas perfect?

take off and landing ?

Or not at all and the FOD guards only are raised on the ground when the engine is off ? If so why do they use intake cover then ?

I'm about to close some Zactoman intakes and I would hate to make a use mistake :thumbsup:

(at this time the FOD are raised) for a landing roll flanker ...

Comments & inputs most welcome

Hello Red Dog

This is how Andrei Fomin describes the Intakes complex of Su-27, in his book "Su-27 Flanker Story"

http://i635.photobucket.com/albums/uu71/ae...u-27Intakes.jpg

Regards

aetosjm :thumbsup:

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