Question for BD-700 Global Express Pilots

[BizJet700]

.... Shutting up the aircraft and setting trim to a fully negative position?

Over the past few years I've noticed several Bombardier BD-700 Global Express aircraft parked up with their horizontal stabilizer drooping down at a fully negative position. Is this company policy? A safety measure in strong winds?

I've never noticed any other type of aircraft parked up with their horizontal stabilizer at a fully negative position like this, so the issue seems to be unique to Bombardier Global Express aircraft only.

If you have any information that could answer this question, I'd really appreciate it if you could reply to this thread.

Thanks for taking time to read this.

[screwballburling]

It is possibly a measure to keep water out/away from the elevator drain holes, while parked up. Any accumulated water would also drain away and down. Not into the elevator via the drain holes.

It could also not provide a level surface so snow would be less likely to accumulate.

I dont fly the aircraft in question but i have operated aircraft where we employed this procedure.

[con-pilot]

When we parked overnight in the 727 we always ran the trim full nose down to allow any water to drain out in case it rained. I'm assuming the BD-700 does it for the same reason.

If water is trapped in the elevators and then freezes at altitude you could have some severe control problems.

[screwballburling]

Con

"If water is trapped in the elevators and then freezes at altitude you could have some severe control problems."

Amen to that!

[mystere-falcon]

it's also to avoid that the water drain forward to the APU door, there've been some issue with APU due to rain.

[specialbrew]

All your pics in the link show the stab in a more or less neutral position. Thats just the way it is in the Global. It you see one with full negative (de-iceing sometimes) then there is a big difference.

[BizJet700]

Thanks for all your comments everyone.

@ specialbrew

No, actually you're mistaken. Take a look at N902MM on the right hand side and compare it to M-GBAL:
Question for Global Express Pilots (http://alexpeake.co.uk/bd700/trim.htm)

GBAL's trim is set at neutral, whereas 902MM is set to fully negative. As proof, I have a close-up of 2MM's tail:
http://alexpeake.co.uk/bd700/N902MM.jpg

This clearly shows the trim limits marked with red lines and you can see... it's at the fully negative position.

That picture was taken in September where temperatures were at least 20C+ so any theory about de-icing can be ruled out.

[south coast]

Forgot to reset the trims after landing...

[macjet]

why would you have to trim fully down for landing and then forget to reset?

[welliewanger]

I've heard that these aircraft used to have problems with rain getting into the stab and it filling up. This puts a huge weight right at the back of the aeroplane - not good. To fix this, they put drain holes in. It's only speculation, but it could be that someone has just got into the habit of setting the stab nose down to help drain the water.

As far as I know it's not a Bombardier endorsed procedure.