Question regarding Citation C525?

[TotalBeginner]

Can anyone tell me what the black paddle is for that sits behind the engine exhaust?

At first, I thought it was just to protect the engine pylon from the hot exhaust gasses, but the other day I saw one of these aircraft taxiing and it was actually moving to deflect the exhaust flow. Considering that this aircraft does not have reverse thrust, what is it's function?

http://cdn-www.airliners.net/aviation-photos/photos/1/6/0/1357061.jpg

Image courtesy of airliners.net

[cldrvr]

Exactly as you stated, a paddle; giving it greater forward speed to keep up with the grown up planes.

[bfato]

They're Thrust "Attenuators".

They don't produce any forward thrust, they just reduce the amount of reward thrust at idle. For use whilst taxying.

[TotalBeginner]

Exactly as you stated, a paddle; giving it greater forward speed to keep up with the grown up planes.

Right....:rolleyes:

They don't produce any forward thrust, they just reduce the amount of reward thrust at idle. For use whilst taxying.

Ah, I see. Is this to reduce wear and tear on the brakes?

[cldrvr]

Yup the reward reduces the ware.

[bfato]

It's a brake temperature thing. When brakes get too hot they won't work so well, which could spoil your day if you have to reject a take off just before V1.

[TotalBeginner]

So how are these things controlled? Do they operate as a function of the N1?

[fleigle]

TB
Here is a serious answer, honest.
They are called thrust attenuators and are moved into the exhaust to deflect the thrust at idle (tickover), this reduces forward thrust while you are trying to slow down. Idle rpm's are fairly high and there is quite a lot of residual thrust.
The CJ3 does not have them as the engines are FADEC controlled and idle at a lower rpm, therefore less residual thrust.
They are operated by levers on the throttle quadrant, and are not interconnected to N1 values.
Cheers,
f

[His dudeness]

They are deflected with WOW and throttles idle. Unless you use the emer stow switch.
Having them stowed gives you a 5% penalty in T/O distance. No penalty in LDG dist if I remember correctly. Mounted on CJ, CJ1 and CJ2. All the pluses and the 3 don´t have em as they have FADEC with lower idle.
Operated hydraulically. On a side note, there is a difference on how they deploy during startup, I think on the 2 both move, on the CJ and the 1 they move when the respetive engine is started.

[airfoilmod]

In an admittedly Pedantic fashion, they don't "Attenuate" (Reduce) thrust so much as "Vector" it away from rearward, and in directing thrust "To the Side" reduce forward motion. They are "Poor Mans" Reversers.

Airfoil

(Nice Photo):ok: