Are the MD-90's pylon flaps EVER cycled?
 

So, as you may know, the MD-90 has movable control surfaces on the engine pylons called pylon flaps:

http://i.imgur.com/mBxe13M.jpg

http://i.imgur.com/l5vS5MI.jpg

When the MD-90 was developed, it was discovered that the larger engines were heavy enough that they made it difficult to recover from stalls in certain situations.

So when the yoke is pushed near full forward position, and (presumably) when certain airspeed/AOA conditions exist, the pylon flaps deploy hydraulically to provide additional nose-down authority.

Here's the thing: They appear to literally NEVER get cycled.

I work at an airport where MD-90s appear constantly, and I've never seen the pylon flaps deployed during control checks. No MD-90 pilot I've spoken with has ever seen them deployed. And three MD-90 maintenance technicians with whom I've had contact each said the same.

Additionally, I can't seem to find a single photo or video anywhere on the web showing the pylon flaps in the deployed position.

So is it true that these potentially quite critical control surfaces are literally never cycled? If so, how in the world can it be ensured they will function properly when needed?

EDIT: Removed an unnecessary word.

Well, I'll be... Never even knew they existed and I commute on the Quiet Dog fairly frequently.

I guess tested & serviced as per maintenance schedule.

I thought so too. But in speaking with multiple maintenance technicians, none of them have ever seen the pylon flaps cycled even during heavy checks.

A flight test report I read says the flap deflects 30° down when the stick is full forward and take two seconds in operation. Perhaps it's operation is tide in with AoA, WoW or some other, hence no movement on a ground check.

Just found this.
• A pylon flap system, installed on the trailing edge of each pylon, provides increased aircraft nose-down pitching moment in the event a deep stall is encountered.
• Moving either control column to the forward stop activates the system. The pylon flap surfaces move from neutral position to fully deployed. Moving the control column off the forward stop causes the pylon flap surfaces to return to the neutral position.
• The blue ELEVATOR AT LIMIT light on the OAP illuminates to indicate that the pylon flaps and the elevators have reached the full down position, and will also illuminate to indicate full up position of the elevator.

Sounds as if when you do a full movement check if you don't get a blue limit light you have a problem with elevators or the pylon flaps, trouble shoot to find which is not bringing the light on.

Is there a plane with more doodads, oddball fixes and aero tweaks than the Mad Dog? I hope not.

GF

Probably the Beech 1900.

Yes, the only aircraft i've flown that had a compass mounted behind the pilots.


Read by looking into a mirror, looking into another mirror on the glareshield


Didn't look at it much..

Every day you did the Cockpit Preparation Procedure, Stilts, I hope! :E

I'm sure FBW covers up a lot of those... ;)

As an old boss used to say, "a multitude of sins".

Thanks so much for finding this. It doesn't seem to specify whether the pylon flaps actually deploy during a control check on the ground. It's possible they only ever deploy while in flight.

In which case, I still question how they can be checked and how it can it be ensured they will function properly when needed.

At the risk of stating the obvious, they aren't very big and from many angles they are hidden by the nacelles.

But you can see them move (just) during the control checks here

https://www.youtube.com/watch?v=aiC2-TRBdqI

at about 3:11.

Sweet mother of god....you just blew my mind.

I swear I must have stared at dozens of MD-90 control checks over the years trying to see those damn things move. Thanks so much for finding the video clip for me.

I knew PPRUNE would come through.