Ques. for MD90 pilots

[your_dreamguy]

Hello,

I was wondering if the VSCF is a device which uses ram air to spin a generator, thus, making electricity? IF not, can you clearly explain what a VSCF is, using simple language.

Also, is it true that the ailerons in the MD90 are not hydraulically actuated but are actuated by tabs?

Also, can you explain why the MD90 elevators can look split (or disconnected) on the ground?

Finally, do you know where I can get MD90 information and gouges at (on the web)? Hope to hear from you.

 

[FreightNazi]

Need to bone up for your oral at CAPT? The VSCF uses the Fetzer valve to generate electicity. The valve compensates for the variable speed of the engine and helps to dampen out the surges in electricity when the engine power is varied, keeps the lights from dimming and the getting brighter.

The aileron tabs are hydraulically powered through the aux hydraulic pump system and provide redundency in the event the ailerons become jammed.

The elevators are split on the ground by a bungee spring and at approx. 80 knots of airpseed, ram air through the big scoop at the base of the tail pushes a piston connected to a rod that mechanically locks both elevator panels together.

There are not many MD-90s around and I was fortunate enough to be able to fly one in a previous life. Let me know if you have any more questions.

 

[LarryinTN]

I know the DC9's through the -41 series. I don't think any of this was changed in the MD90, wasn't in the MD80.

Don't know what a VSCF is. The DC9s don't have it.

The only powered control is the rudder. The elevators and ailerons are free to float up/down. The ailerons are bussed together with a bus cable so if you push one up the one on the other wing moves down. The two elevators are not connected and move independently. Both the ailerons and elevators are controlled via a control tab. The control yokes are connected to the control tabs with cables.

The elevators can split on the ground because there is no internal connection. If wind comes from the side it can push them in different directions. As airspeed builds on takeoff they will move to the position commanded by the control tabs.

Now, before anyone jumps in to say that the elevators can be powered, there is a system which pushes the elevators toward nose-down using hydraulic actuators but it only comes into play if the elevators are not moving on their own. This should only happen if the airplane is stalled and there isn't enough airflow over the elevators to get them to follow the control tabs. It doesn't come into play during normal flight operations.