Viggen airbrakes, configuration on shutdown

[MeneMene]

I got my hands on the Tarangus JA-37 and am working on the various aftermarket items and modifications I need. My understanding is when the Viggen is on the ramp, shut down, the hydraulic pressure bleeds off, and the canard controls, flaps, ram air turbine, and top thrust reverser all droop. Does anyone know if the same applies to the airbrakes? Furthermore, I've heard that later versions of the JA-37 had the airbrakes disabled and wired shut; does anyone know what time period or production numbers this involved?

 

Thanks

[Murph]

The addition of a data link and the Rb74 (AIM-9L) in the mid to late 1980s required the addition of extra switches on the throttle that displaced the speedbrake switch, so they were wired shut.  AFAIK the whole fleet was upgraded to this standard.

 

Regards,

Murph

[Christer A]

Nitpicking on: The canard control surfaces doesn't droop, it's a flap that is set for landing and take-off, on the ground it's always deflected down, but that is not connected to the oil pressure.

The Ram Air turbine, or Möllan always opens when the landing gear cycles down.

Nitpicking off.

 

The control surfaces for everything else droops when the pressure is bled off though. This also includes the inner main landing gear doors, (but they stop traveling after just a few degrees, enough to notice but no more than 5º!) and the upper thrust reverser petal. That one droops to almost closed position.

 

[MeneMene]

1 hour ago, Christer A said:

Nitpicking on: The canard control surfaces doesn't droop, it's a flap that is set for landing and take-off, on the ground it's always deflected down, but that is not connected to the oil pressure.

The Ram Air turbine, or Möllan always opens when the landing gear cycles down.

Nitpicking off.

 

The control surfaces for everything else droops when the pressure is bled off though. This also includes the inner main landing gear doors, (but they stop traveling after just a few degrees, enough to notice but no more than 5º!) and the upper thrust reverser petal. That one droops to almost closed position.

 

Tack! What about the airbrakes? Basically I'm trying to decide if I need to get an aftermarket airbrake set if they're going to be open. I would assume if it's one of the aircraft with the deactivated airbrakes they would be permanently shut?

[Thomas Kolb]

For the AJ/SK/SH/SF versions, the airbrakes on the sides stay shut, but on the bottom side they tend to drop slightly (just a few degrees really, but enough to reveal a slight gap).

 

On the JA version however the airbrakes were disabled completely. This was done already during mod C in 1993, where the lever to control the airbrakes in the cockpit were rewired for controlling the radar instead.

Edited September 27, 2019 by Thomas Kolb

[Christer A]

What Murph said about the airbrakes is most probably true. It's 21 years since I was since I was a conscript turn-around mechanic in Swedish Air Force, and Skaraborgs Flygfottilj F7 just had one squadron of AJS37 then (rearming to Gripens at that time) and it's a bit different to JA.

But basically, on the AJ:s the top ones were NEVER extended on the ground, but lower ones did droop, IIRC.